John Eiler, Isotope Geochemist, Instrument Builder, and Division Chair of GPS

To review John Eiler's scientific record, from field geology to cosmochemistry, from the upper atmosphere to biological compounds, and from paleontology to planning for the return of Martian samples, is to behold a research career that traverses a massive range of chronology and geography, all with a grand unifying goal. Eiler's vision is to build, through his lab and in enabling the capabilities of students and colleagues, a comprehensive review of all isotopic varieties in nature. Noting the nearly infinite extent of the scope of research, Eiler readily acknowledges that the target is both crazy and absolutely worth pursuing. Eiler wants to push the boundaries of what can be discovered in the laboratory, and the benefits of those discoveries, whether for resolving basic questions in the fundamental sciences, or applied toward societal benefit, will work themselves out. And for anyone who knows Eiler, the pursuit is where all the fun is.

In the discussions below, Eiler recounts a very midwestern upbringing, an undistinguished academic record in high school, and a love of geology that he developed in college at the University of Iowa, where he connected with the laid back culture of geology and the outdoor opportunities that field work offered. At the University of Wisconsin, Eiler honed his interests in isotope geochemistry, which naturally led him to Caltech for his postdoctoral appointment. As an incisive student of history, Eiler was well-acquainted with Caltech's historic leadership in this field, and he discusses with pride and affection what it was like to see Professor Sam Epstein, one of Caltech's founding geochemists, in his prime. He explains Professor Ed Stolper's "miracle year" and what it means to publish four revolutionary papers in rapid succession.

Through brashness, hard work, and an intuition that allowed him to zero in on the most important research problems, Eiler was offered a faculty position in 1998. The story he relates about the moldy lab he inherited is one of the funniest and most inspiring stories that has ever come out of Caltech, and it is a testament to Eiler's do-it-yourself approach and a capability to solve problems from the mundane to the esoteric. During his assistant professor years, Eiler's focus was in field work, and his reflections on the process of coming up for tenure offer instructive lessons for a system that works in the best possible way. Having established a solid and well-regarded research record, Eiler felt that the decision was truly not his concern, and the positive outcome and academic freedom it secured allowed Eiler to pivot more squarely into instrumentation. For the past twenty years, the Eiler lab has become world-renowned in isotope geochemistry for the sensitivity and range of its instruments. It attracts scholars from around the world whose interests have made the Eiler lab a hub across the fundamental disciplines of chemistry, biology, and physics, all connected by the mysteries that can be unlocked through analysis of the isotopic composition of rocks.

Toward the end of the discussions, which concluded in 2023, readers with enjoy some famous last words. In looking toward the future and thinking about the possibility of becoming Division Chair of Geological and Planetary Sciences, Eiler offers a confident "not going to happen." One year later, and his appointment is reflective of all good things: Eiler's love of Caltech and the GPS division; his commitment to service and to giving back; a can-do attitude that will keep his lab running at full steam; and above all, a sense of adventure that will propel GPS into its next generation of greatness.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Tuesday, October 3, 2023. It is wonderful to be here with Professor John M. Eiler. John, thank you so much for having me in your office.

JOHN EILER: Thanks for spending the time with me.

ZIERLER: To start, John, tell me please your title and affiliations here at Caltech.

EILER: My name is John Eiler, and I am the Robert P. Sharp Professor of Geology and Geochemistry in the GPS Division.

ZIERLER: Geology and geochemistry, does that suggest a dual appointment, or is that just inclusive of your areas of expertise?

EILER: This is a great question. I was hired to build a geochemistry lab but my background is in field geology and in petrology, which is the study of rocks. You'd think, well, isn't that all geologists who study rocks? In a way, but petrologists study rocks in a very formal way, using classical thermodynamics and mineralogy to understand the origin and evolution of rocks. I have that sort of classical background, and yet I don't have a classical career. My career is all about the creation of new technologies, the creation of new measurements, exploration of all kinds of things that are not rocks. To me, the title is totally appropriate. It captures both my perspective that is an outgrowth of my training—I feel very close to the field-based geosciences, to classical areas of the geosciences, so, yes, I'm a geologist—but I'm also a geochemist, which is a different thing. Geochemistry is sort of this branch of chemistry that was stolen from the chemists when they weren't paying attention to it—

ZIERLER: [laughs]

EILER: —and stapled onto the side of the Earth scientists. It is this visitor from another discipline that comes in and tries to solve problems in the natural sciences. I feel aligned with both of those things, so it seems perfectly appropriate to me.

ZIERLER: For geochemistry, is the perspective for you that you're a geologist who uses the tools of chemistry, or in some ways are you a chemist interested in geology?

EILER: By training, I'm definitely the first of those things. I have virtually no formal training in chemistry, physics, math, instrumentation, engineering, nothing.

A Total Rocks Guy

ZIERLER: You're a rocks guy, geology all the way.

EILER: Totally a rocks guy, in my training, and yet somehow everything that I do that has any lasting impact, I would say, is a consequence of things I've been able to do with chemistry, with even life sciences—biology sorts of applications—mostly with technology. I had no idea until I started doing this job that I was good with instruments, I was good with my hands, I could fix things, understand things. I didn't know! It's sort of like somebody who owns a car. If it's never broken, they don't know whether they can fix it or not. If you break a car and put it in a garage and say, "Do something," well, maybe most people would be frustrated, but that's a kind of situation I discovered I was good at. All of that is sort of home-cooked, me catching up with my own ambitions in whatever way I can, but really my intellectual home base is in geology, in classical geology.

Another thing is that the people within the geochemistry option, none of us take the label that seriously, to be honest. From my perspective, it is the freest of the options intellectually in our division, and maybe on the campus, at least in my experience of the campus. We kind of don't care what people think we are or do. We're doing what we're doing. Geochemistry is what we do. If we change what we think that means, then the field is changing with us. If we want to show up at a geology meeting or show up to admit geology graduate students or go to a geology seminar, well, for that hour, we're geologists. If the next day we want to go hang out with the planetary scientists, well, now we're planetary scientists for the day.

Geochemistry is a very loosely defined field. It can be about many different things. I think you can see that in our heritage. Part of the heroic age faculty of geochemistry at Caltech was like Clair Patterson. What was he doing? Solving problems of pollution in the environment and thinking about humanity and its future and its environment and what it was doing to the world. Walk down the hallway, and you see, say, Gerry Wasserburg, working on extraterrestrial materials, stellar evolution, early solar system history, the geological evolution of the Moon. Things that feel completely intellectually separate, but they had a lot in common. Whether they were friends or not, they knew each other, they understood each other's science, they each knew what the other was doing every day. They maybe could have stepped in and done similar things in each other's groups. This gives you a sense of the intellectual flexibility of what geochemistry is. To me, it just spells freedom. Every day, you do what you want to do that day.

The Bob Sharp Legacy

ZIERLER: The other aspect of your title, being named in honor of Bob Sharp, what does that mean for you besides the honor of it? What does that mean intellectually? Is there a connection to what Sharp did to what you do?

EILER: There are several things about Bob Sharp that I respect very much and that are important to me, and that I try to identify with. One is his commitment to a positive, connected, academic culture within the Division and the Institute. He was somebody who understood leadership. He understood what it meant to have a close academic community, to make decisions together, to talk openly with each other. He was just a wonderful tent pole of the culture of the Division. To me, that's a very important thing to keep contact with. The second thing is the nature of his science was unique, in a way. He was fascinated with absolutely anything that had a kind of puzzle-like quality to it, in the natural sciences. It could be landscape evolution, stratigraphy, the movement of a rock across a playa. Like almost anything would catch his attention, and if you could look at it and be open to your own curious responses to what you were seeing, and realize, "There's something mysterious about this, something peculiar. I don't have an intuitive ready-made understanding of this. I have to find my way to an understanding of it"—he would do this with anything. You put absolutely anything in front of his eyes, and he would problem-solve it.

I love the openness of this idea, the notion that the world, that nature generally, presents us with puzzles. They don't have to be recognizably important for you to want to solve them. You can let the importance come later. Let the future figure out whether or not these things are important. Some of them will end up seeming trivial and yet they appeal to us in an aesthetic way. Others seem like they are naturally going to be important. Maybe they end up being impactful, and yet they might be less beautiful in this way. He just was drawn to his own curiosity, his own desire to understand what was happening around him. I relate to that very much. I recognize there are certain scientific questions that have immediate impact—things having to do with climate, and human health, and so forth—and it is important to advance those. But that isn't necessarily what motivates me every day. I'm much more motivated by the desire to go to new places, see new things, either literally or metaphorically, and somehow understand them, and somehow impose an understanding on them.

ZIERLER: On the topic of going to new places, seeing new things, tell me about the decision-making for a field geologist. It's a big planet. There's lots of places to go. Resources are limited. How do you make those decisions to maximize productivity on a trip?

EILER: This is a great question, and not everybody answers it productively. In fact, field geology as an enterprise is enormous. Many thousands of people may have to make this decision every year when they're going to design their field seasons, and they answer your question in different ways. I think there's a fork in the road that happens early on in the career of a field-oriented scientist. One path that you can follow is mastery of, almost possession of, a limited block of real estate: I will be the expert of the who-goosed-the-moose, pluton, or the such-and-such quadrangle. That will be my stomping grounds, and I will become the person who is the arbiter of understanding and facts and interpretation in that place. A lot of Earth scientists get drawn into that. The way I'm saying it, you can tell how I feel. It's an intellectual mistake. It makes you automatically parochial. There's a strength to it. You like to know people who are like that, because they know things, they see things, that you have never seen, just by exposure and time. But the other path, the one that's more impactful and fruitful, I would say, is to go out into the world with a question in your mind, and to be seeking for the clues that are answers to that question. I think that's making your decisions seeking out a line of argument that will bring you to some sort of yes or no conclusion about a motivating problem.

ZIERLER: A generational question, for field geology. Nowadays, with computational modeling, even AI and machine learning, are you seeing in students an assumption or a lack of interest in field geology because so many things can now be done in a simulated environment? Is there a concern? How do you convey the irreplaceability of going out into the world?

EILER: That's a great question. First of all, this whole line of questioning, I feel a little bit of an imposter syndrome answering it, because by training and inclination, I love the field, I understand what it means to be out in the field; I'm a lab rat in practice. The last 30 years, 20 years basically, I'm in the lab, building things, designing things, and so forth.

ZIERLER: But you're reliant on samples.

EILER: Absolutely, absolutely, and I retain an affection for the field. In any event, you are correct that there are crosswinds that blow people out of the field. There are all sorts of things that are going on. One is the diminishment, in the U.S. in particular but also in Europe and Japan, of field-oriented economically driven geology. In the 1950s, 1960s, maybe even 1970s, many of the people who came through Earth science programs, they knew in advance, or in the end they would soon learn, they were destined to work in economically inspired, field-based geology, whether it is the metals mining industry, or the petroleum industry, or coal, or who knows what. All these different subdisciplines of economic geology, they were a massive draw as a job market. That largely shaped the nature of our programs. We had to teach people the skills to do those things. Also, the structures of our programs. There were lots of people who would get master's degrees and go out into the world. I was part of the tail end of that. I was educated in the early and mid 1980s, and the programs that I was in were still shaped from that history.

Today, virtually nobody—nobody is too strong of a word, but a small fraction of all of the people who get PhDs in the Earth sciences in the U.S. end up doing some form of economic geology. They are almost all either moving into other areas of STEM, or working in environmental sciences, or moving into space science, or life science. They're doing something that is different. Different problems, different inspirations. That has radically changed the skill set that is called for. The fact that there is a lot of remote sensing going on and a lot of computational science, I don't think that's the main driver in the move out of field work and into other sorts of modes of study, because the people who do lots of remote sensing and the people who do lots of modeling of Earth's surface and Earth interior processes, those people are actually closer to the field now than many other disciplines. They are using those tools to interact with their field-based understanding of the Earth. A person who uses geodesy or orbiter imaging or something like that of the Earth, those people probably also go into the field and interact with the Earth in a more direct, human way. It's the people who are off studying completely different questions, things other than the origin and evolution of the rocks at the Earth's surface—those people have less and less reason, over time, of going out into the field and doing classical geology sorts of activities.

ZIERLER: Some overall questions before we get to what you're actually pursuing in your lab. Let's start first with fundamental research and translational research. Is there anything that you do where you see the applicability in society, or would you say your entire research agenda is what we call curiosity-driven?

EILER: My personal motivations are all curiosity-driven, but I interact with translational research a lot, and it's intentional. My motives are not so much to engineer outcomes in society myself, but rather to take things that I know I'm good at creating and presenting them to a broad enough community that people who are focused on these other issues will pick up what I have created and reshape it to those ends.

ZIERLER: What would be an example of that?

EILER: Analytical technologies are the most obvious ones. Over the last 20-some years, most of my career has been organized around a series of sort of five-year-long steps that have slowly built to a crescendo of ability to observe isotopic content and structure, at the molecular scale, of natural things. I have my own motivations for doing this, but I recognize that there are many spinoff applications. Initially, these were applications to environmental small gases—CO2, oxygen, things like this. Those have obvious applications to climate research, to rocks. Those remain connected to geology, but the things we could measure had to do with the climate of the Earth's past, so again circling back to climate change.

Increasingly, as the technologies that are being developed in the lab have become more sophisticated and broader in their applicability, the translational potential for this has expanded. Forensics, so the ability to recognize pollutants, explosives, chemical weapons, illicit drugs like performance-enhancing drugs, these are all things that you would read about on the front page of the newspaper, and they are being impacted by things that come out of my lab. I'm not driving that in the sense that I haven't dropped everything that I'm interested in and gone off to pursue those subjects with a goal in mind. Instead I sort of purposefully dabble in a way to signal to those communities, "Something new is here. There's a new potential for you. I'll show you with a paper, or two, or three, what can be done." Then my expectation is the people who have lifelong commitments to those subjects will pick them up and develop them as appropriate.

ZIERLER: You're enabling capabilities.

EILER: Absolutely. Then I would say the capability that has been—I've seen it off on the horizon for a long time but now it's here—is the ability to influence the study of life in very impactful translational ways—medicine, and environmental issues. Environmental metabolomics, environmental pollutants, and the metabolic processes of the human body, these are things that we can now directly design studies that speak to current problems in those subjects. I'm not a doctor. You should not come to me to fix a metabolic disorder that you have. I would do a very bad job at that. But I know that the things that have been enabled by developments in my lab are going to impact that field. The problem that I face is learning just enough about that discipline that I can show people who are really in it what is possible, and once they see it, they will pick this up and run and I'm sure that they will.

ZIERLER: Have you ever come upon something that inspired you to start a company or get involved with tech transfer, or is it always about sharing this with the people who are already in that space?

EILER: I did start and run a company for a few years that was an analytical services company. I viewed it as a way of concretely enabling this transfer of analytical capability out of the academic realm and into more applied uses. It more or less worked, but I quickly figured out, this isn't more effective than what I was doing before. The thing that really is effective is recruiting people who are high-performing, creative, intellectuals, whether they are academics or not—they're intellectual leaders, in these other disciplines. Finding a way to get their attention, finding a way to engage with them. Convincing them to invest their own time and resources into this. They will then figure out how to bring the rest of their field with them. Simply opening my doors and saying, "There is a measurement that I can do for you," that presupposes that people know what to do with—the measurements that get developed in my lab, they're really different from anything that people have been measuring. Most people don't know what to do with them until you show them.

The technological inventions, methodological papers, these have no impact by themselves. The only thing that has lasting impact is a proof of concept demonstration that you can take a new tool and solve a problem with it that matters to the other person. That catches people's attention. They will look at that and say, "I wish I had done that. I don't care about the measurement. I wish I had solved that problem." Once you catch their attention in this way, whether it's competitive or whatever else, you've got ‘em. They're hooked. Now they want to learn. They want to know how to do this. They want to adopt it. That, I think, is the most effective way for somebody like me to impact other fields.

ZIERLER: Let's overlay that looking at the motivations and interests of your graduate students and your postdocs. Will a prospective person come to you and say, "I'm interested in this technology"? Not so much interested in geology and the basic science, but you have now developed the tools where I can take this. Does that happen?

EILER: Absolutely, that happens, yeah. The students and postdocs that come through my group, first of all there's two very different paths in and out of my lab. One is people who show up wanting to apprentice themselves to me and to the laboratory group so that all the things that we know how to do, they will learn how to do, and then go off and take it in their own direction. That's one path, and it demands a certain set of skills and a dedication to a certain set of goals.

There's then a lot of other people, say a subequal group, who come in with a specific motivating problem. They are almost certainly co-advised by somebody else, another member of our faculty, or maybe even another colleague from another university. They know that we have something going on that's probably relevant, but they don't really know how to do it. They don't know how to craft a measurement that addresses their problem. So, we work together to problem-solve that. In those sorts of instances, I'll only really get engaged with them if I find the problem interesting, like I'm personally getting something out of it that I find engaging, intriguing. But these are things that don't come directly out of me alone. They show up with a motivating idea and I respond to it and say, "Yeah, that's pretty cool. I want to learn more about that. I want to hear more about that. That is worth solving. I want to help you solve that." That's a different sort of path for people who come through.

The subject matter, what these young people imagine they're going to go on to do, this has changed a lot over the 20 years that I have been engaged in this technologically-focused research, and increasingly it is aimed at life science, biomedical science. The last PhD student who just defended was co-advised by Dianne Newman and myself, and Woody Fischer. Dianne Newman is a biologist, Woody Fischer is a geobiologist, I'm a geochemist and geologist, and the student in question, Renee Wang, her mission from the beginning was to use the principles and the tools of isotope geochemistry in order to solve problems in metabolism, generally defined, but also medicine—metabolism as it influences disease and human health. That's a student who showed up with a vision, and we all sort of responded to that and resonated with it.

These sorts of collaborations, co-advising young people, this is the way that you evolve your own science, I think. I really mean co-advising, because if I attempt to change directions by responding to a fresh interest or a fresh opportunity that some student is maybe also interested in, well, I don't really know much about it, because it's not my area of specialization. They don't know much about it; they're at the beginning of their career. We're likely to make a lot of mistakes and to miss a lot of details. By joining forces with a colleague somewhere else on campus who has a really different body of training, and maybe even different motivations for doing the same project, that way we can really bounce off each other and make each other stronger.

Crossovers into Biology and Chemistry

ZIERLER: Have you found that the smallness of Caltech is really conducive for interdisciplinarity? Do you bump into colleagues from different divisions and ideas nucleate just from those chance encounters?

EILER: For sure. For me, the two main conduits for that interdisciplinary stimulation and projects, one is through biologists who are adjacent to our interested in our geobiology program. Not everybody who does biology is interested in what Earth scientists do. Earth scientists and planetary scientists, we are fundamentally engaged in a different intellectual enterprise from what most other branches of the natural sciences are doing. We are not there to abstract a principle of physics, or a new class of chemical reactions or whatever, that can be idealized as a sort of abstract thing. We are there to understand the specific, the particular, histories of real objects, unique events, unique objects. The history of the Earth and of the planets, it's not composed of abstract principles; it's composed of things that happened, and objects that really exist! You have to be engaged with this individuality of materials to be an Earth scientist.

That's a very different perspective from a biologist or a chemist who wants to get something different out of the study. They want to get out of it an insight into something that will be universal, that will then translate to other organisms or to other chemical systems. Earth scientists also like it when they discover things of broad importance, but we're always thinking about the individuality of the things that we study, rather than their abstractable generalities. I have a bunch of Chemistry students who have come through my lab. They remain Chemistry students. It's not like I go and steal them from the Chemistry Division. They are Chemistry students. They just hang out in my lab, and I advise them, and they are doing chemistry theses in my lab. The biologists, it's a similar sort of thing. You can absolutely be a Biology graduate student if you want.

ZIERLER: All of the impetus for sustainability nowadays—we have the Linde Center right here, we have the Resnick Institute—what are some points of contact for you to get into that world?

EILER: I just received my first Resnick seed grant, and it is to help us—this a perfect example of the give and take. What I need is focus and support to pursue a goal that's the—the thing that's right on my horizon now is to translate the ability to study isotopic structure as a way of understanding materials from its current focus on discrete molecules, things I could dissolve out of a material and I could hold up and say, "That's this chemical species of the following name, and the following well-defined structure." That's great, seems like an obvious target; most of organic matter in nature is not like that. Most of it is condensed. Most of it is refractory. It's a solid. We have very poor tools for understanding how these solids form and evolve and respond to their environment and record their environment. Think about your own body. Like, yes, there's molecules in your body, but mostly, you are a big goopy pile of boogers or something! Like you're just a condensed material with a very irregular structure. So how do you talk about that thing? It's not a molecule, it's not not a molecule; how do you study it in ways that relate directly to the sorts of things that I measure—isotopic contents and isotopic structures? It's a problem that needs things that I can do, very badly, because these are super complicated materials. Some of the oldest carbon materials in the Earth, in the solar system, are of this type. How do we study them? We have very few ways to understand their origins. As a result, we say very crude things about them.

How do you bring a sophistication of observation, a specificity of interpretation, to these sorts of materials? You have to somehow observe complexity in them, a complexity that records their chemical history. And I think it's possible. These things have isotopic structures. I think it will rationally record how they formed and what they've experienced. But how do you get it out? This is the highest-level challenge that my group is working on right now. It connects directly with one of the goals of the Resnick Institute, which is to both understand, and more importantly engineer, the Earth's carbon cycle, a major component of which is refractory carbon in soil. Most of the organic carbon that is fixed by the Earth's biosphere that doesn't get immediately re-respired, it ends up going through a very complicated multi-timescale history of breakdown, storage in soil, part of it is permanently buried, part of it is remobilized but over many timescales and many mechanisms. It's complicated.

But as soon as you start trying to track one of these solid particles, like a piece of charcoal or a decaying piece of wood, through the environment, there's a lot going on chemically but you don't really see most of it. You don't have ways to interrogate that, that are very sophisticated. You have crude ways of describing them, like, "How much carbon is in the soil?" Okay, that's a thing you should know, but it's a simple observable. There are many different things that could lead to that same thing that you observed. So how do you bring nuance and interpretability and sophistication to these sorts of observations? I think one way to do it is systematically disaggregate these materials into component parts that are in the Goldilocks zone in size. They're not so small that they contain no information; they're not so big that I can't work with them, I can't manipulate them; they're in between, where they are faithful recorders of their chemical histories.

The project that we're doing with Resnick is to figure out how to bridge the gap between easily solubilized molecules that we already know how to study with a lot of sophistication, and refractory carbon in the environment. There are steps on that path. The molecules make oligomers, groups of molecules. The oligomers condense to make solids. The solids are assembled in tissues of plants and so forth. So, there is kind of a Russian doll, nested doll problem here, and we're trying to worm our way from the free molecules to the solids that we find in soils and asking specific questions like "What are the isotopic fingerprints of origin?" Materials that are stored as refractory carbon in soils, how were they synthesized? And then what are the isotopic signatures of destruction? Can I take carbon out of soil and say, "Fifty percent of it was made like this, and 50 percent of it was made like that, and it's 70 percent destroyed by this mechanism, and it's 10 percent destroyed by that mechanism, and you are seeing the 20 percent that's left"? That kind of statement is what we're aiming to be able to do.

ZIERLER: Beyond campus, what about JPL? Is that an asset for you?

EILER: Yeah, for sure. The scientific problem that my group talks about most often as giving shape to what we're trying to do is Mars Sample Return. Mars Sample Return is motivated by lots of different scientific questions. Many different sorts of scientists will work on the samples that come back. But I don't believe we would have done it if we didn't think we were going to get back organic matter so that we could interrogate that organic matter and ask whether life has ever existed on the Martian surface.

ZIERLER: To clarify, organic matter does not mean living matter?

EILER: Exactly. Organic matter, organic molecules, organic solids, organic films, things made of carbon-hydrogen-bond-rich materials. So, life is entirely organic. Basically, without organic chemistry, there is no life. There was a time when people interested in the origins of life and the distribution of life outside of the Earth would talk fancifully about silicon-based life, and germanium-based life, and all kinds of wild-eyed things. I saw Freeman Dyson give a lecture on this once that was entertaining, but also like, kind of pointless [laughs].

ZIERLER: This is when physicists go out on a limb?

EILER: Yes, exactly. These days, nobody is talking about that, because it's ridiculous. You look at yourself. Life is organic chemistry. You look out into the universe. The chemistry of the universe is mostly organic chemistry.

ZIERLER: It's the same chemistry here on planet Earth.

EILER: It's the same chemistry. Like the resonance between what we are and what we see outside of the Earth, in terms of chemical processes, is so obvious and so direct that of course we're looking for organic life.

ZIERLER: It probably overcomes a bias that we have to think that we're somehow special or separate from everything else in the universe.

EILER: Perhaps. I think that the interest in conceptualizing life as being something other than organic, I think it was just sort of a playfulness. People would like to play with the idea of what life could be. That's fine if it's a parlor game, but once it becomes real and you have to design experiments and design telescopes and send missions to places, playtime is over, okay? You need to actually make some serious decisions. Once people are making serious decisions, they are going to focus exclusively on the search for organic evidence of organic-based life. The problem is that organic chemistry is everywhere. That both should make us optimistic that it is imaginable that there could be life on places other than the Earth. If organic chemistry is everywhere, well, then, why couldn't it organize itself in a way that it did here? On the other hand, that means there's a background of non-biological but very complex organic chemistry happening everywhere. At some level of concentration, I can take a rock from the Moon, from Mars; I could just collect all the molecules in a big volume of space; I will find organics absolutely everywhere. And they won't be that simple. There will be complex organics all over the place.

How do I understand the way they got to be the way that they are? If I go to Mars, some of the organic carbon that I find could be the remains of life. Once a system stops being alive, once an organism dies, it very quickly degrades. It doesn't degrade to nothing. It's not like every atom separates from every other atom and it's like the thing was never there. But the specific molecules that are present, they are transformed. They are not the things that were there when the organism was alive, with a few rare exceptions that we call molecular biomarkers. Even molecular biomarkers, we shouldn't expect to find any.

If you knew, for sure, that Mars had been inhabited, and you had a sample from Mars that had organic carbon in it, that doesn't mean your job is easy. To connect the carbon you're seeing to the organisms that were there, you have a big job in front of you, because it has been transformed. Billions of years have probably passed between an organism's living chemistry and the gunk that you're finding in the rocks. How do you recognize the processes that transformed it? How do you undo those transformations in your imagination and picture what the chemistry was before? Once you've done that, how do you recognize that those precursors were biologically created and were not non-biological products of some abiotic chemistry? Doing this, it sounds impossible. And, it almost is impossible. It's a big task. But we're doing it. Like, we're definitely gonna go. We're there. We're going to try and bring these rocks back. Hopefully that succeeds. If it fails, we'll try again. Eventually, we will make this work. But then what? How do we interact with these materials? We either get incredibly lucky and discover like the chemical equivalent of an eyeball or something, and you're just like, "Yeah, obvious that was alive"—maybe, but don't count on it. That's a very unlikely outcome.

ZIERLER: Especially don't count on a sample that's based on a few centimeters of surface drilling.

EILER: Yes, that's right! Imagine your job was to randomly grab—just clear away all the obviously living biomass on the Earth, and look at the rock record, especially the old rock record, which is what we had access to on Mars. Close your eyes, reach out, grab one rock at random, and look at it. Prove to me that the Earth is inhabited based upon that. If you know the answer already—we have a set of circular arguments that we use in the geological record. It's very instructive to follow, what is the logic that people employ to recognize life in the very ancient geological record? What it amounts to, when you strip away all the blibber-blubber, is if it's carbon, it was alive. That's the reasoning. Then there's a bunch of little filigrees people add to that to make it sound good. But that's basically what we do. And we're probably right, okay? Because it's the Earth, and the Earth is inhabited, and it has been for a very long time, and when you pick up rocks that formed in Earth's surface, in the oceans and things like that, and you find a bunch of carbon, well, that's a very good guess. But it's a guess. If we discover, truly discover, life on another planet, it will be an epochal transformation in the way that people view themselves, their history, their place in the universe. I don't think you can really overstate how impactful it will be.

ZIERLER: Not to mention the appetite for future discovery that it will engender.

EILER: That's right. But I think just the recognition—not that it's possible. Everybody sensible recognizes that it's possible now. Recognizing that it's true is a very different thing than recognizing that it's possible. How about if it's not true? If you knew for a fact that we were alone in the universe, that would be an unbelievable transformation of thinking. Maybe some people with certain sorts of backgrounds, philosophies, religious perspectives, whatever, would feel validated, but most of us would be shocked if we knew that that was true. And we would be shocked if we knew specifically how it was not true.

ZIERLER: Also it's logically impossible to prove the negative, notwithstanding the size of the universe.

EILER: I suppose so. Let's just say that you knew that everything within a thousand light years of us was completely uninhabited and sterile. We would find that shocking. That's a knowable thing.

ZIERLER: You're just talking about the world of probability—the number of stars, the number of exoplanets, the number of Goldilocks zones?

EILER: I suppose. I think that the Drake equation kind of argument that you're circling around—this is the famous equation where you say, the probability that life is on a planet is this factorial probability times that factorial probability times that factorial probability, and when I do the product sum, that's the chances of life. Well, you've only seen one thing, okay? One of these terms is really, really much more important than all the other terms. It feels good to do the Drake equation, because you're like, "I have a question. Here's a question mark. It equals a number I can know, times a number I can know, times a number I can know, times a number I can know, times a question mark." Sorry, brother, you ended up with question mark equals question mark.

ZIERLER: [laughs]

EILER: Like, it didn't work! You got nowhere! And we are getting absolutely nowhere with this problem until we actually discover either evidence of life outside of the Earth or a truly exhaustive and representative set of null results where we're seeing organic chemistry in potentially habitable settings and it just didn't work.

Organic Chemistry Across the Universe

ZIERLER: In the way that you are establishing these connections of organic chemistry here and throughout the universe, is that to say for your research agenda the distinction between terrestrial science and planetary science is not particularly meaningful to you? Is it all planetary science and we're living on one of them?

EILER: It's all planetary science. There's a difference in methodologies, obviously, because of the ways that you access places outside of the Earth. But we're not so unfamiliar with that. Almost all of the Earth's volume is inaccessible to us, also, and yet we have opinions about it. There's also a difference in scientific culture. Planetary science is an outgrowth of astronomy and of the lunar program and the federal bureaucratic structure of that. That's a different community from the community—geology and geochemistry, they are outgrowths of late 18th century gentleman scholars going on walks, okay? That's what we are descended from. These are very different sorts of communities, and that, actually I feel like, is the bigger barrier. Obviously the principles of physics and chemistry and potential principles of biology and so forth, those were all the same, of course. The Earth is just a planet. It's one of a whole bunch of planets and we just happen to sit on it, so we know more things about it. But I don't view that as an important distinction in terms of what is worthy of study or not worthy of study or what I would take on as a question.

ZIERLER: Is your starting point always Earth and you look for applicability beyond Earth, or sometimes do you start with a research question that originates with a meteor, Mars, the Moon?

EILER: The latter. The applied research focus in my lab group has shifted in a very purposeful way. I view it as a—maybe it's in bad taste—but as kind of Stalinesque five-year plans.

ZIERLER: [laughs]

EILER: This truly is the way I have always conceptualized my research program. There is a goal. At the end of history, we're getting this lab to this place. Seems impossible. You're wrong. It is not impossible. We're going to get there. I'm going there in a straight line, but I'm not telling you that that's happening. I'm telling you, in five-year steps, where we're going. The first step might sound implausible, but you'll come along with it, because you can see it might be possible. At the end of that, we're doing another one. Now, the end of that second five-year period, you can see it, even if it isn't there yet. And so forth and so on. After you do four or five of these, you're there, at the end. Every one of these sort of five-year plans or five-year steps, there is a restatement of what the applied scientific purposes of the activity is. In my mind it's all the same activity, it's all the same goal, it's all the same motivation, but with different things to talk about on that leg of the journey.

Starting about five years ago, that leg of the journey became about prebiotic chemistry, the chemistry that enabled the emergence of life. There's a sort of paradox in the study of life's origins—that we can only study prebiotic chemistry in nature as opposed to in the lab, in places that were never alive. Because you put life in the midst of prebiotic chemistry, and it's going to completely run the show. So, we only see prebiotic chemistry happening on the modern Earth in small amounts, in special places. Probably even in those places it's heavily influenced by life, directly or indirectly. If you want to see pure prebiotic chemistry, you need to be looking at materials that were never alive. This includes, luckily, most of the universe. You look up into space, virtually every molecule that has more than two or three atoms in it is organic, and they're everywhere, and there's a lot of them. So there's a lot that can be done with telescopes.

Then primitive meteorites also contain an abundance—actually, there's more unique soluble organic molecules in primitive meteorites than there are in living organisms, a greater diversity of them. Life is in a way not the proliferation of organic chemistry; it is the restriction and control of organic chemistry. Organic chemistry run wild is much more diverse than the chemistry of life. That's what you see in primitive meteorites. Understanding how it operated, not just how it could have operated, that's what the lab chemists do, and they're very good at it. Some of them are very good at it. They will go into the lab and say, "I declare that the origin of life could have been like this." Yes, that's beautiful chemistry, but Earth science is not about what could happen; it's what did happen. We want to know exactly what did happen, and from that, you have to read records. You have to find objects that are preserved from that period and interpret them correctly. Beginning with the primitive meteorites is an obvious place to go, and once you're done with them, you then want to go to the oldest parts of the geological record and planetary bodies that may or may not have undergone the emergence of life—so Mars, outer solar system bodies.

ZIERLER: You mentioned Mars Sample Return. Do you have formal affiliations or collaborations at JPL?

EILER: I do and I don't. There are research collaborations, some of which—there have been research grants that I am a co-PI on that are part of the joint funding program between Caltech and JPL. I have colleagues at JPL who work very closely with me and are in my lab all the time, and they have their own grants through NASA and so forth. I don't have a JPL appointment. I don't even have a JPL ID or anything like that. I have to call a friend if I ever want to get on the Lab.

ZIERLER: You're a civilian like anyone else.

EILER: I'm a civilian like anybody else, and I don't have my own separate-from-another-colleague NASA grant or anything like that. I like it that way for the time being. Big institutional activities, if they're well motivated, I like to interact with them and do things that promote their aims, and elicit a response, and are just part of the scientific dialogue; I don't really like being totally aligned with them because they restrict your field of play, in a way. There's a level of groupthink that's involved—in what is an appropriate sample, what's an appropriate measurement, what's our sequence of operations. I like deciding that stuff on my own, so I prefer to just somehow, by hook or by crook, get access to samples. Luckily that's not too hard. My lab was the first to measure isotopic properties of individual molecules from the Hayabusa2 mission, the Japanese Space Agency mission. They added me to their team, so now I'm technically part of their team. I never did anything to be added to their team. They just said I was on their team. They didn't directly send me samples. They said another colleague who knows me could send me samples. It's just totally informal. I prefer it like this.

ZIERLER: When the Mars samples come back, there's going to be a worldwide effort.

EILER: Yep.

ZIERLER: The best instrumentation in the world—

EILER: Yep.

ZIERLER: —the best minds to look at these samples. How do you see your lab contributing? In that five-year plan—we have some time to plan for that—

EILER: Yes. We do.

ZIERLER: —where do you see the evolution of your lab to be responsive to looking at these samples?

EILER: First of all, there's a good chance that I will be retired either as the samples return or soon thereafter. That's just reality. I'm 56 years old.

ZIERLER: This is like a ten-year kind of thing.

EILER: Exactly. I'll be mid-sixties. You could say, "Oh, you could keep going until you're 80." Well, who knows? Maybe I'll fall over dead from a heart attack, or maybe I'll lose interest, or who knows what. People at the end of their life, they go do other things. I am not assuming that I will be the person who says, "All right, here's what we're going to do. We're going to measure exactly like this." More likely, given the timing involved, somebody who has been trained by me, or one of their trainees, or something like that, that will be the way that the individual effort manifests. My focus is rather than on preparing myself and the instruments in my individual PI lab, I'm focused on getting Caltech ready, getting Caltech and JPL ready, to, whoever is here—if I'm still here, great; if not, also great, everything is going to be great—we will be in a position to lead. That will mean first of all focus. We need to pick some things that we will lead on. There are many different tasks that will be part of the study of materials returned from Mars. Some of them will be necessary but not important, others will be important but not super-super important, and others will be potentially transformational.

If you could discover, and be correct, and could convince everybody else in the world who's paying attention and knows what you're talking about, that you had found evidence of life on Mars, or could prove that everything we had found was not alive—either way, that's going to be one of the most important statements that comes from this whole activity. If the answer is a positive, that there are the remains of life, and you can prove it in a way that will stick, that's one of the most important things anybody has ever said in the sciences. So, we need to be a part of that. Whether we're a part of all the other things, I don't care that much. That question, I think we need to be not only part of it, we need to be leaders of that. I believe that the kinds of research that comes out of my lab, it won't be the only line of evidence that is used, but it will be an important line of evidence.

So, one of the things that I'm doing right now is trying to act as sort of matchmaker, if you will, or midwife, or something, to create what will be the next-generation lab. It will have to be a new entity. I view it as being the synthesis of two things that already exist. One is the kinds of capabilities that are in my lab. And then, the capabilities that exist in our analytical centers. We have a departmental analytical center that was funded by the Moore Foundation 15 years ago or something. We also have some other PI labs that do exotic sorts of spectroscopy on surfaces. So there's a kind of unified lab that, if it existed, if I succeed, it will have involvement of half a dozen or a dozen Caltech PIs, engagement with JPL that's very direct—people from JPL coming down and working in the labs here—and that will be focused on instrumentation that is specifically designed to address the question, "What is the origin and history of traces of organic material?" Most of which will be solids, condensed things, films and so forth.

Preparing for Mars Samples

ZIERLER: In preparing JPL and Caltech to study these samples, what aspects of your enabling capabilities do you think will be geared toward the need to develop new instruments designed to study these? Because there are things obviously that our current capabilities fall short.

EILER: Right. I think that the correct environment in which to do this kind of work is, first of all, to have multiple modalities of observation together.

ZIERLER: What does that mean? What does that look like?

EILER: What that looks like would be top-of-the-shelf observation of surface topography and composition. These are known technologies, things like electron microscopes and things like that. Second, spectroscopic observations that are nondestructive and characterize the chemistry of surface materials. Third, destructive but only modestly destructive chemical analysis using ion-microprobe type technology but that's general in its applicability. It can be used to study elemental abundances, isotopic abundances, metals, organics, all kinds of different things. These are technologies that already exist. They should be innovated, made better. They're naturally being made better because they exist as commercial devices. Those are needed as a kind of base to make framing observations so that you can contextualize the more decisive capstone measurements that you're using to make decisions about what you see, but you shouldn't disrespect them. These are things that have to be happening in part of the same environment.

So, I can take the same sample, I can look at it, I can characterize it. What are the minerals that are here? What's the topography that I see? Put it in the spectrometer. What are the compounds that I see? What are the chemical moieties that are present? Put it in the ion probe. What are the trace element abundances that I see? Now I have a context built and I move to my decision-making, "it was alive or it was dead" measurement, which I would say is going to have to be based on the integration of very good organic speciation characterization, so mass spectrometric description of what molecules are there—that will get you partway there, and then it must be merged with descriptions of the isotopic structures of what you see, which encodes what it was made from, what are the environments it was in, what reactions has it experienced. Which of these compounds I see are connected to other compounds that I see? Because the chemistry of life is not just a mechanism for churning out molecules; it's a system of cycling of molecules. A begat B. B begat C. C begat D. D begat A. This sort of cycling connection among chemical components of systems—that's, at a very high level, a thing that you are looking for in the recognition of the products of life. You want to see exactly how the begats worked in the relationships between molecules.

How do you do that unless you have tracer that you can follow from atomic position to atomic position in a natural material? The only thing that does that is isotopes. It's obviously self-serving in a way, or self-referential, because this is what I've committed my life to working on, but I think it will be decisive piece of evidence. So, I think that the correct lab is, we do that in a way that is beyond what I can do today in my lab, but I can see it. It's gonna happen. Do that on solids, do it in a way that's more sophisticated than what I'm doing right now, and then nest all of that in this contextualizing information that comes from more familiar technologies.

ZIERLER: This question is going to be as much political as it is scientific. The narrative of Mars science from the first rover in 1997 to Perseverance's capabilities today, it makes perfect sense why Mars Sample Return would be the next chapter in this evolution. We now have the rovers. They can drill the samples. They can store them. Now we just have to get them back here. The built-in frustration, though, of Mars Sample Return seems to be that what we know is suggestive that there isn't any life on the surface of Mars.

EILER: Yeah!

ZIERLER: You have radiation. It's totally dry. And yet we don't have to abandon Mars entirely. We know that there's probably subsurface water.

EILER: The subsurface aquifers. If there's somebody alive in Mars, they are living in the subsurface aquifers.

ZIERLER: To go back to this multimodal approach that you're saying, I wonder if you can explain—we don't yet have the capabilities to go to the most likely source of extant or past life on Mars, but how does what is available to us now—Mars Sample Return—ultimately get us to perhaps a jackpot?

EILER: What we know for sure is present, because we observed it with the Curiosity rover, is that there are trace organics that are part of the sedimentary rock record, we probably will get these things back by Mars Sample Return, and they consist of organic compounds that have been reacted with sulfur. They are sulfur-bearing organic compounds, and they are mostly ringlike structures that remind us of things that form through catagenesis or breakdown of organic matter. If that's going to be representative of what we get back—and we should assume that it is—if you're hoping for a Hail Mary pass, like we pick up the samples and there's DNA or a perforin or something in it, like, God bless you, but this is probably not going to happen. If instead we get back this gunk, this sulfurized gunk that I describe as being like vulcanized rubber—actually, this will be—I'm going to commit right now—I'm going to figure out some way to do a measurement that proves that vulcanized rubber has as a component biomass, at some level. It comes from a petroleum product. Petroleum is from biomass. I'll figure it out.

ZIERLER: [laughs]

EILER: We're going to just—hold me to that! Okay. How do we take this vulcanized rubber that we're going to bring back and figure out what it was? We have two tasks. One is, recognize the chemistry that controlled its transformation from some precursor into what it is now. This is a family of processes you could call—geologists, we'd call it catagenesis when it happens hot in the interior of the Earth; metagenesis when it occurs at very intense heats, like maybe impact metamorphism. You could call it surface weathering or something, or surface modification. There's lots of different processes that are happening. Diagenesis. This whole collection of processes, this molecule you're looking at, there's a process that was the last one it experienced. Figure out what that was, and undo it. Okay?

Then once you've done as many steps as are needed to figure out, "What do I think the precursor or precursors of this molecule were?" do that simultaneously with a variety of molecules. You will hopefully recognize, "I had a family of precursors. They looked like this." There's a chemistry side to that. Now you know the chemical molecules that were there. You have some ideas of them. But now you've also undone the effect of their modification on the isotopic structure. The isotopic structure—and this is something you and I haven't talked about at great length—but the basic concept is that even simple molecules, molecules that look to us chemically sort of anonymous, there's many ways of making them, they could be made from many different substrates, and once they're made they all look the same. Like every molecule of glucose, to first order, looks the same. Most of them are made by plant photosynthesis, and so forth. But once they're made, how are you supposed to know?

The ways in which the naturally occurring rare isotopes substitute in them are tremendously diverse, and so diverse that they impart a complexity on these molecules that rivals genomics. If I take a molecule like glucose, there's six ways I can put carbon in it, and six ways I can put an oxygen isotope in it, and twelve ways I could put a hydrogen rare isotope in it—deuterium. You might think, okay, great, so there's twelve, six, six—twenty-four—twenty-four different things. Oh, no-no-no-no-no; we're just getting started. There's also the doubly substituted forms. I could have a carbon-13 here, and an oxygen-18 over here, or a carbon-13 here and an oxygen-18 over there, or two carbon-13s here, and so on and so forth. Once you start working through the combinatorial math of all the forms of substitution, for all practical purposes there's an infinite number of them. It's like 1015 or some crazy number like that, and every one of those forms of substitution is its own chemical entity. It has its own free energy information, its own rates of reaction, its own probability of formation from substrates. It is unique. Each one of them is an independent vote on how that molecule was formed, and what processes it has undergone that have destroyed it.

The gestalt, the change in thinking, is to realize not just that isotopes impart some kind of additional info. Yeah, if you just measure simple things, like count all the carbon-13 atoms and then you're done, yeah, you just learned one additional variable. No-no-no-no-no. In principle, and therefore if you are good at our job in reality, there's a functionally infinite number of independent things that are recorded here. It's like the genome. It's unique. Every sample must be unique. So, instead of being guided by Darwinian evolution and inheritance, and defects and so forth, it is instead guided by chemical physics. What are the physical rules and physics expressed through chemistry that control the probabilities of rare isotopes finding their way to all the different positions in molecules, and in different combinations, how does this work?

You could look at it in despair and say, "It's so complicated nobody is ever going to know." Great, if you feel that way, you sit in the corner while we work on this. This is a massive undertaking, but the components of it are known. Before I started working on this, the components that were known were the existence of the isotopes, the chemical physics of how isotopes change bond, vibrational energies and a few other things about isotopes. We didn't know their manifestations and every possible way they could manifest, but we know the basic principles. I layered on top the ability to observe. Now we can observe. Basically you name any molecule you want and any reasonable set of substitutions, and I can in a few minutes design a measurement that could be done that will see them. If you can merge the ability to observe and the capacity to understand, well, now you've reduced it to engineering. You just have to get out your elbow grease and get to work on understanding the specifics of the real reactions you care about, and so forth.

That's the situation that we've created, and I believe that once we aim that tool at even relatively simple molecules that we recover from Mars Sample Return, we will figure out how they got the way they were, and then we will recognize in their isotopic structures whether they either resemble things we already know—"Oh, that's just meteorites, primitive meteorites falling out of the sky and getting cooked." If that's true we will figure that out really fast, because we already know what meteorites look like, and we will figure out quickly how the sulfur reactions work. If they're not that, well, then what are they? Oh, maybe they're atmospheric aerosols. Okay, I can make atmospheric aerosols. I will figure that out. Maybe they grew from hot springs. We have hot springs. We will figure that out. What if none of those check out? What if they don't look like any of those things? What if they have isotopic structures that are not terrestrial-like? We know that because we know what all the terrestrial life looks like. They're not any of these things we recognize. And yet, they have patterns to them. I recognize, oh, well that molecule was made from that one. That inherited something from this other thing that I know from the principles of chemistry that are related to each other like so. And there's some weird pattern I've never seen, like every third atom is enriched, or something like this.

That's sort of like how life works. All of your cell walls have fatty acids in them. The fatty acids have a zigzag carbon isotope structure like Charlie Brown's shirt. That's an imprint of the acetyl group-based chemistry, the center of our metabolism. Every other carbon atom comes from a different origin. If there are patterns like this, we don't have to know in advance what the metabolism was that made them. We will recognize, that's not right. Something is there that does not happen abiologically. Now my task is to figure out a plausible mechanism that explains it.

ZIERLER: If I'm hearing correctly, you are decoupling the scientific value of studying these samples from the somewhat reductive goal point of determining if life exists or existed on Mars. The question is, is there a concern to avoid a media narrative that defines success or failure based on life?

EILER: Yeah, the media narrative will be composed almost entirely of nonsense from day one, I guarantee you.

ZIERLER: [laughs] Okay! You've made your peace with that already. [laughs]

EILER: [laughs] Yeah, I've totally made my peace with that. It is unavoidable. Because no one controls anybody else in this business. If you're an academic scientist, unless you're unlucky enough to have a boss, you get to say what you want to say. If I want to take a sample and I make some stupid measurement and I run to the press and declare that Mars was alive, or that it was dead, or whatever, I can do it! They'll republish it and whatever, like, "Oh, Caltech professor says—blah." Of course that will end up in the newspaper. None of that matters. That's just noise. The reality that will stick is a logically sound evidence-based proof. People have become so jaded into thinking that, well, but what is proof, and what is real, and what if not everybody believes me? This is noise, okay? In the end, there is a community of serious-minded scientists. They are evaluating each other's evidence. There is a dialectical process. If I say something, someone else will try to disprove it, as they should.

ZIERLER: That is science.

EILER: That is science! That process is going to take place. I have a particular vision of what I think would be a central argument that will happen. There will be many side arguments. There will be people who say the effective equivalent of what we say about ancient rocks on the Earth: "If there's carbon, there was life." That's what they'll say. They'll dress it up, but that will be what they say. Fine, let them say it. They can say anything. You're allowed to say whatever you want. It's a free country. But that doesn't mean that you have to be distracted by it, and I will not be distracted by it. One of my reactions to the media narrative about these samples will be the same reaction I actually had that got me into the study of prebiotic chemistry. I started in this area by going to a conference where I knew a bunch of people would be talking about prebiotic chemistry. I thought, "That sounds interesting, I want to see what kind of field this is." I went and sat all day and listened to them, and they were talking past each other. Nobody was really responding. Everybody got to have their pet theories, and while they were on the stage, it was true.

ZIERLER: [laughs]

EILER: Then the next person gets up, and their pet theory is true, and everybody [claps] you know, golf-claps for them. I thought, perfect. There's no one in this room who knows how to say no. I will be the one who says no. I will figure out a way to test hypotheses quantitatively. If you want to tell a story, I will turn it into a prediction that is quantitative, and then I will go measure, and then it will be true or not true. The papers that we write about this subject, the part that I think has longer-term impact that people follow are the positive statements: "I think this prebiotic molecule formed like this, and I think this one made that one," and so forth. Also in these papers is a lot of me saying, "No." Like, "It could have been like this. People said it was this theory and that theory and the other theory. None of them are right. Because, it would have led to the following testable consequence, and we looked, and it's not true."

That will also be a very important part of this dialogue. Again, it's self-referential, but I believe that the observation of isotopic structure will be an important part of those arguments. People will find organic molecules. They will say, "This reminds me of a hot spring in the Earth. Mars was dead." Then we'll go and measure the isotopic structure. If it's identical to the isotopic structures of things from hot springs, well, then, congratulations, you guessed right. If it's not, please sit down. We're still working on this. I think that process will continue, and if at the end we actually bring back the digested, transformed remains of life, we will figure it out.

ZIERLER: How do you think those discoveries, whatever they are, will define the next mission to Mars? What does that sequencing look like to you?

EILER: I think the only thing that resets the clock in a way is if we discover that all of the organic matter we recover is explicable as meteoritic infall that was then destroyed in the weathering environment at the surface. If that's true, then it means we mostly missed the story of organic synthesis endogenous to Mars. Although there's a silver lining in that case. You could say, well, all of those organic molecules, now they exist on Mars. Next, what happens? What's their fate? Some of them will end up in the crust. Some of them will end up in the aquifers. Some of them will end up wet. Some of them will end up getting gardened deep in the crust by impacts. What's happening there? So, it's not the end of the story, if that is the outcome. That would lead us to think, well, let's try again. But instead of looking at surface deposits, which appear to be overwhelmingly dominated by things that fall out of the sky, we've got to look somewhere else. We have to look, I don't know, hot springs, maybe that vent fluid. We have to look at places where the aquifers vent to the surface or near the surface and see what's inside of them.

The second possibility is we discover evidence of prebiotic synthesis endogenous to Mars. I think this actually won't be that difficult to recognize, whether it's endogenous to Mars, because the atmosphere and the hydrosphere of Mars have exotic hydrogen and nitrogen isotope compositions, so we will figure out molecules that are made from them. If it's endogenous to Mars but clearly formed by mechanisms that are non-biological—they're thermodynamically equilibrated, or they remind us of processes we can do on the lab on metal catalysts, or in hydrothermal bonds or whatever—then we will say, "Okay. There was no life here. But the building blocks were being made here, actively." So now they're not even a choke point on the supply. There was probably a lot of organic chemistry happening in the crust, and now again we have to move somewhere else that gives us indirect access to that crust. Maybe we look for rocks that are exposed at the surface that experienced subsurface aqueous alteration, or we look for places where we believe that the salty aquifers are occasionally venting.

The third option is we convince ourselves we're looking at the remains of endogenous life on Mars, and now we desperately want to find it. Is it alive? I think all paths lead us to shifting from the surface environment, the lake bed sort of concept, to materials that were processed in a water-bearing crustal setting and then brought to the surface where we can sample them.

ZIERLER: It's exciting, no matter what way you look at this?

EILER: Yeah. We're obviously going back. I mean, come on. It's the only planet that seems geologically exciting and is near us, so we're going back.

Tenure and Pivot to Instrumentation

ZIERLER: For the last part of our talk today I'd like to take a verbal tour of your lab. To start, by way of context, you mentioned a shift in your research about 20 years ago, the focus from field geology more to laboratory work. What was happening 20 years ago? What were the advances technologically and in instrumentation? What was the evolution of your research questions that prompted this shift?

EILER: That's a very good question! The most important thing that happened 20 years ago [laughs] from my perspective is I got tenure. [laughs]

ZIERLER: Freedom.

EILER: Freedom. But actually it led me to ask a very specific question of myself that changed the direction of my research and the time scale that was important to me. Prior to 2003, my lab mostly studied the isotopic compositions of oxygen and hydrogen in igneous rocks, in basaltic rocks, asking questions ultimately about plate tectonics, the chemistry of the Earth's interior, the processes by which the Earth's interior melts. It was petrology, and very rock-focused. But I dabbled in other things. I worked on molecular hydrogen in air, thinking about the hydrogen economy and things like this. I worked on meteorites off and on. I studied the Allan Hills Meteorite that some people thought already provided evidence of life on Mars. I had exposure to other areas of science, but this lab that was really only capable of doing things in this petrology-focused, geo-focused sort of area.

Near the time that I got tenure, I really asked myself, like, what do I think of what I've accomplished? It's good enough. I have enough papers and so forth and people will say nice enough things about me that I'll probably get tenure, but what do I think about it? And I thought, you know, it's a little derivative, honestly! Like, I go and pick up an igneous rock, and I ask what the chemistry of the interior is and how it melted and so forth; I basically know the answer. There's some fine details to this that I don't know, and it would be nice to define, but this is like—I've been in this room before, I know this space, and I know what's going to happen. The scientists that I most respected—

ZIERLER: They pivoted?

EILER: They pivoted, and they—there's many different kinds of scientists that are all—it's all perfectly valid. In fact, it's all necessary. You can't have scientists that are constantly pivoting. If every scientist is constantly pivoting, certain problems never get anywhere. We don't land on the Moon if everybody involved is constantly changing their mind. We'd never understand the Ice Ages if everybody is constantly changing their mind. That required decades-long commitment to specific programs of research to make that happen and specific applied areas of research where you largely know what's going on; you just have to fine-tune, you have to get to that next decimal point, to really have an answer that satisfies you. Great. You guys all go do that. That's not my game. I'm not strong at that. I don't want to do it.

The scientists that I most wanted to emulate—Sam Epstein is probably the paragon of this. He was happy—he would study anything. He was absolutely fearless. The concept that he would look at a problem and say, "That's too hard," or "It's too far away from me"—if he was interested in it, then it was in the palm of his hand. He could just do whatever he wished. If he was not interested in it, okay, maybe then he loses attention. But this capacity to just treat everything as your subject—and he had another trait that he—not only was he willing to go in new directions, he was clearly drawn in them. He wanted to study things where he didn't know the answer. You get up in the morning and you just don't know what's going to happen today in the lab. That was the kind of science that he did throughout his career. I said to myself, "You gotta stop doing things that you know the answer to. That's a great way to keep your job, but it's not who I am, and it's not the person that I want to be."

ZIERLER: Did you know him? Did you overlap with him?

EILER: Yeah, he was my postdoc supervisor. So, I really committed the idea that assuming I get to keep my job, knock on wood, I am going to swim towards the open water. I'm going to find something in my field—it can't be so far away from me that I'm unable to impact it. It can't be like particle physics or whatever. Although—I guess that was my pandemic project, was—

ZIERLER: [laughs]

EILER: —something with particle physics. But it has to be something that I can reach. It also has to be somewhere I've never been. And just by weird coincidence—I also love the old literature, like really old literature. If I'm getting into a new subject, I don't want to read the latest review paper. I want to read the first paper that was written in 1935. What did they think this was about? Because scientific disciplines drift, and sometimes they drift towards the light, and sometimes they drift down into the gutter and they don't get anywhere. Like, don't go to the end of the drift. At least look at where this began and think about that.

I was working on hydrogen in air, and the hydrogen economy at the time. I could have just been reading papers about fuel cell cars or whatever, but I wanted to read papers about the isotope chemistry of hydrogen. It was the model system, molecular hydrogen, from which chemical physics of isotopes emerged. That was the system that Harold Urey and people working in that same era studied to understand how isotopic substitution changes chemistry. I'm reading these papers and I realize, they didn't really care about all the things we measure. We measure molecules that have one rare isotope in them because they're easy to measure. They're not super, super rare. They cared about molecules that had two rare isotopes in them. That's weird. No one has ever measured that, in nature. Huh. I wonder like what that would be like, if you tried to do that.

First of all, how many are there? You think about it for 10 seconds and you're like, "Oh, wait a minute. It's almost everything." Almost every unique form of matter that is different from other isotopic forms is multiply substituted. 99.999999999 percent of all the things that are being recorded in nature isotopically are recorded in forms that are unique combinations of rare isotopes. No one has ever seen one of them. That's open water. I'm going to get there. Immediately I set as a goal, we should be able to measure anything in anything. There's a lot of molecules in science. There's like 50 million molecules that you will find on PubChem or something like that. My discipline at that time knew how to measure maybe 12, all little things, like CO2 and N2 and things like this. This is ridiculous.

ZIERLER: There's a big world out there.

EILER: There's a huge world out there. We are stuck, we are literally—it would be as if you knew what the scope of the universe was and you're living in a community that has not undergone the Galilean revolution. Not only is there something out there in the solar system—keep going, brother. Like, there's just a lot. There's a huge amount out there. A negative mindset would say, "Yeah, but what's it for?" "Trust me. You're going to figure out what it's for." There's no way that nature is recording a trillion unique forms of every molecule known to science and no one has ever measured one of them and that it will not be good to look. It will be great to look. We will learn so much by looking. But we have to do it in a way where we have freedom, where we're not constrained by our technology in the questions that we can ask.

Of course, you're always constrained by your technology, but I want to push against that. I want to make this as general as it can possibly be. Because virtually all of chemistry is organic, immediately it was clear, "I have to be able to study any other isotopic form"—within reason, let's say up to four or five rare substitutions or something in a molecule—"and I must be able to do it on any arbitrarily chosen organic molecule you'd like to name." Because that's virtually all of chemistry. It's virtually all of isotopic variability. This has to be the technological goal. And I will start heading in that direction. But I can't say it to anyone. Because they'll incarcerate me.

ZIERLER: [laughs]

EILER: Because it's so far away from anything we have measured. If no one has ever measured anything but a single isotopic substitution in a dimer, gas, obviously what you're saying is crazy. But how can it not be possible? They're there. They're here. They're everywhere. They're molecules. They weigh something. Of course you can measure them! They have concentrations. They have masses. So of course a mass spectrometer can measure them. You just have to problem-solve it. That took 20 years, but now we're truly there. We're actually there.

ZIERLER: What you're narrating is really the platonic ideal of what tenure should be about.

EILER: Yes. I feel like I experienced that. It's not going to be everybody's experience, and lots of people will have perfectly admirable goals that don't benefit in the same way.

ZIERLER: But what's unique for your experience is you saw diminishing returns in the area of expertise you had achieved to get tenure.

EILER: Yeah, and not just diminishing in some absolute sense. People still do the stuff that I was doing, and they're writing great papers, and it's exciting, and all that stuff. It wasn't good for me. It was diminishing for me. I did not want to do it. That's not the person I wanted to be. So I jumped ship, and started swimming. And won't stop. The five-year Stalin plan now is Mars Sample Return. Why? Because that is the thing to say that is both true and forces people I'm talking to, to want to go in the direction I'm going. [laughs]

ZIERLER: [laughs]

EILER: I want to be able to do the things that I do on the reality of the world. The materials that are most of the organic material in the universe, really, are these condensed things. What is the purpose of only being able to study little soluble molecules? There's a lot of them but they don't make up most of what is there. Most of the material is this other stuff, and we're just avoiding it. We're like not looking at it, or something, other than in very simple ways. I'm going to crack that. We're going to figure out how to take that material and do to it what I now do to free molecules. Then Mars Sample Return, perfect timing. That's a great excuse. If it wasn't that, I would pick a different excuse, and that would be the excuse.

ZIERLER: John, last question for today. In this transition, pre-tenure, post-tenure, going from field geology to lab experimentation, what were the perspectives, skills, even your sense of intuition, that you brought with you from field geology into the lab?

EILER: Really reductionist problem-solving was always something that I enjoyed. I knew I was good at it but I didn't know how good I was at it. I didn't realize that I could solve problems no one had solved, with it. I knew I could play this game with other people. I didn't know that I could get outside of the game and use those same skills to really innovate and get myself to a space that people hadn't been to before. But the thing that I brought with me that I still value is training in not necessarily field geology but petrology, classical thermodynamically inspired petrology. It's a very formal, rigid almost, discipline. I'm not a master of it the way that Paul Asimow or Ed Stolper are. They are true masters of thermodynamic petrology. But I'm not bad at it. I'm pretty well trained at it. This formality of analysis and the playing with rules, it has a chess-like quality to it, and a rigor, that makes you good at formal reasoning, and makes you good at addressing the reality of the complexities of materials. Both of those are things that have been super important. If I had set the goals that I set but I was a flake, I would have gotten somewhere—like, they couldn't fire me, so of course I would still be doing something—but it wouldn't have been productive. It was very important that I could make new measurements and then shore them up with formal understanding—experimental, chemical physics theory, applications that make rational sense. This sort of training in very formal petrologic reasoning,

I've fallen back on it again and again and again. Today I'm doing it in trying to develop the data science tool that will let us make measurements—the current benchmark goal in complexity of measurements that we make is to take a medium-sized molecule, something with a couple dozen atoms in it, and observe, let's say, a thousand unique isotopic forms at some unique precision. What that means is, it's more complicated even than measuring a thousand genes in a row, because genes are present or absent, on-slash-off. I'm saying a thousand independent Cartesian coordinates that are finely divided, and different samples lie along different distances along them. A thousand of them that are orthogonal to each other. That's complicated. It's intrinsically complicated. How do I organize my thinking in a thousand-dimensional Cartesian coordinate system? How do I present arguments? What does it mean to say that I hypothesize a certain process has happened to a sample and it will lead to a certain consequence in these thousand dimensions? How do I take the thousand independent things I observed and turn it into the thousand independent things people want to talk about? I observe mass spectra. I talk about isotopic structures. Those aren't the same thing. You have to go back and forth between them.

There's a lot of mathematics, formal logic, chemical physics, neural network training, taking things that can be predicted formally but very slowly, and turning them into things that can be predicted empirically but very quickly. This whole toolset of data science needs to be created. The measurement will be useless without it. It's sort of like genomics without data science is just a bunch of strips on an electrophoresis chart. It doesn't mean anything. Only when you organize it with the data science of genomics does it impart meaning. That has to be created. Maybe somebody else will do it better than me, but at the moment I'm the only one trying to do it. If it works, it will be because of my training in petrology.

ZIERLER: And you've been having fun every day.

EILER: Absolutely. Every day is fun. Especially with Luigi.

ZIERLER: This has been a great overview conversation. Next time we'll go all the way back and establish family origins. We'll take the narrative from there.

EILER: Okay!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, October 13, 2023. It is great to be back with Professor John Eiler. John, thanks again for having me.

EILER: You're welcome. It's my pleasure.

ZIERLER: Our first conversation, we took a great tour of your approach to science, all of the issues that are important to you. Today let's go all the way back and establish some family background. Let's start first with the name Eiler. Do you know what it means, or who or what an Eiler is?

EILER: I do. Eiler is a word in both German and Yiddish, and it means basically the same thing in both languages, "one who rushes or scurries around." To "eilen" is to scurry. It's sort of an entomological connection I have with one of my main mentors here, Stolper. Ed Stolper—Stolper is "one who stumbles" or stumbles around.

ZIERLER: [laughs]

EILER: "Stolpern" and "Eilen" are kind of related words.

ZIERLER: Ed never told me what it meant.

EILER: He might not have known! Maybe he didn't know.

ZIERLER: Maybe he knows and he wanted to keep it a secret, given [laughs]—

EILER: It could be! My father had a lot of interest in his family roots in Southern Germany when he was young. His own life experience brought him there right after World War II. He spoke German, and so I learned a little German when I was young, and I think I figured it out then.

Brethren Roots

ZIERLER: For your family history, how many generations back did you know? Did you know any great grandparents?

EILER: I personally didn't know anybody beyond my grandparents' generation, but my family history in the Midwest goes back before the Revolutionary War and is weird. I learned a lot about it, and I met extended relatives in Central Indiana, like when I went to my grandfather's funeral there. On my father's side, the family name comes through a branch of the family that lived in Pennsylvania right before the Revolutionary War, and then they fled to Canada because they were basically traitors to the Revolution [laughs], and then came back and lived in Indiana. They were Church of the Brethren, which is sort of like being Amish or Mennonite or something, more like being Amish. There are subtle differences. Honestly I don't know the differences that well. But every male pater familias in my family line on that side going back to the 1750s or something was a deacon or minister in the Church of the Brethren, and because they were always church elders, there is a biography—well, it's sort of a historical description of the Church of the Brethren in America, and it talks extensively about them.

ZIERLER: Oh, wow.

EILER: I have a book somewhere on my laptop that is a discussion of all of them. I probably would have grown up in rural Central Indiana, maybe not really been highly educated, I might have ended up as a farmer or something, except my grandfather, my father's father, he remained a very religious person through his life and he stayed in the Church of the Brethren, but he didn't live apart. Basically he tiptoed out of the sort of separate lifestyle that many of them maintain, when he was middle-aged. He became a school administrator in the secular school system and became a superintendent of schools at a county level. Then when World War II happened, he was probably 40, 42, 43, which at that time made him an old man. Obviously nobody was going to come knocking on his door to make him go fight, but he left his family, left his job—his comfortable, respectable, upper middle class job—and he joined the Armed Forces right away. He was in North Africa before most of the U.S. Army was in North—he served in the U.S. Army but he ended up in a kind of intelligence or signals unit, and they sent him out before the Army started the North African campaign, and he was with like the British Eighth Army in 1942, in North Africa. Then he went all through the North African campaign, all through the Sicily campaign, up the boot of Italy. Then he went to England. He was in the Normandy landings. He was with Patton's Army all the way into Germany. He went to almost Berlin.

ZIERLER: Whoa!

EILER: His family back in the U.S., they were impoverished the entire war. A school superintendent's salary was fine, you could own a home and things like that then, but the idea of having deep savings or anything like that—they were basically in poverty the whole war. Then, he stayed. At the end of the war, he was like, "This is great. I'm living my best life. I want to stay in Europe and you guys can come join me." He ended up being appointed—he was probably almost 50 at that point—and they appointed him the responsibility of rebuilding the school system in Wiesbaden, which is currently one of the biggest Air Force bases in Europe. Most people don't know that, because it's kind of a quiet—there's thousands and thousands of U.S. soldiers there. So my dad came over, I don't know, sometime in 1946 or something like that.

ZIERLER: What year was your dad born?

EILER: He was born in 1938. So he came over, old enough to be making formative memories, and lived in Wiesbaden, and then they would travel occasionally. They went to Berlin within the first six months of his being there. Berlin was just piles of bricks. It was complete devastation. Wiesbaden was mostly gutted. It had been bombed like most of the cities in that part of Germany. His childhood memories of being a school kid there are wild. Like they would go to the opera house in Wiesbaden, and the dome over the central part of the opera house was totally blown open and exposed to the elements, and bent girders and things reaching across the abyss of the orchestra pit, and they would go climb around in there and just like hang out and walk across beams. He had a really wild childhood in that respect, growing up in sort of the ruins, the rebuilding ruins of World War II in Germany.

ZIERLER: Was your grandmother game for this?

EILER: You know—she did it. What choices did she have? Like she couldn't say, "I'm going to bail and go support the family with my own career."

ZIERLER: I suppose it's better than your grandfather finding a new woman there and abandoning everyone.

EILER: I suppose so, that's right, yeah. I don't know what her experience of that was. I was too young when she passed away for me to really know what that was like for her. And their family culture didn't like—people weren't talking about—

ZIERLER: Emotive.

EILER: Right, they were not talking about these things. It wasn't my formative experience, but it ended up influencing my childhood a lot, because I traveled to Europe when I was young almost annually, and many of our trips were weird trips, like for tourism. Like when I was 11, we flew to West Germany as a family. My parents took us out of school for over a month. The teachers were like, "But what about their homework?" My parents didn't care. They were like, "Eh, they'll catch up. It'll be fine." They flew us to Europe in the middle of the school year and we rented a car and drove across the Iron Curtain into Eastern Europe, and we just drove around for a month. We stayed in Dresden and in Erfurt. Now it's a beautiful tourist town in South Central Germany; then, it was like broken glass in the streets and kids wandering around in torn clothing. It was like really going to a completely different world. Getting stopped at borders by teenagers with machine guns in soldiers' uniforms and stuff. Being followed, and obviously profiled by security people because we were obviously Americans in a place we weren't supposed to be. It was legal—there's nothing wrong with doing it—but nobody else was doing it. Those sorts of experiences really open your mind to where you could go, what you could do. Without even consciously thinking of it, I think it influenced—

ZIERLER: Did you ever get the story from your father about your grandfather's motivations in going to war when he didn't have to?

EILER: Not really.

ZIERLER: He's of German heritage. Was that like—?

EILER: —Ish, yeah. He also tried to track down our family tree in Germany. My dad was interested in this. He got as far as figuring out that about 50 percent of the people with the family name Eiler were more or less Prussians and during the war they were all Nazis, and the other half were from far southeastern Germany almost near the Swiss border and they were almost all Jewish. So he had this like dichotomy. What is my family history? I don't think he really figured it out. He traced down some people who my dad's dad had made contact with that he thought were family members near Wiesbaden that had the same family name. I don't think we ever actually figured out that they were family members.

ZIERLER: There's a possible Jewish connection?

EILER: Maybe? It's unclear. If there is, it is centuries old, because the family name—the immigrants who were my dad's forefathers, they were in the country by 1750. That is a long time ago. They were working class when they got here. They were then religious outsiders. How you would go from being ethnically Jewish to a Church of the Brethren, no idea. It's all very unclear. How you would go from Prussian to being Church of the Brethren is unclear. They were like a separatist religious group in Southern Germany. So, it's unclear.

ZIERLER: Was it known that he was horrified by the Nazis? I mean, to give up his job and leave his family?

EILER: No, no one knows. I talked to him—when I was young, I remember he would visit us. I remember my mother saying, "Hey, he's not going to live forever. You should go talk to him and see what he has to say." I was like, "I don't know what he wants to say." He was a very quiet guy. He was not at all garrulous. You could get him talking about the War. He would talk about his experiences driving around in Jeeps and capturing some guy on a bicycle. Like he had war stories, but you never could get a sense of why he would do this, particularly at the age and stage and responsibility. He had three children. One of his kids was almost old enough to join the Army himself. In fact, my oldest uncle, my Uncle Bob, my dad's oldest brother, he was enough older—I think he was 17 in the last year of World War II, and he tried to get into the Armed Forces, and they wouldn't let him. The closest he got was passing a test, a Japanese language test, to get into the Navy to go to the Pacific. He did not know Japanese. Whatever the explanation is—I'm sure the story is apocryphal at this stage—but he supposedly cheated or something and he got far enough into it that he like—I don't think he ever ended up in uniform. He became a cop in Central Indiana. Actually, he wasn't a cop—he was a computer programmer—but his like center of his life was being a volunteer for the Sheriff's Department. He also did like pistol shooting and stuff like that. He was a character as well.

ZIERLER: What was your grandfather's position in Wiesbaden? Was he a military employee?

EILER: He was the superintendent of the school system, and I don't know whether he stayed in uniform when he did that or not. He was tasked with rebuilding both the local school system and then mostly the schools for the children of servicemembers. The Falaise Gap is not that far from Wiesbaden. That's the area where, if there had been a tank battle between NATO and the Soviet Union, that's where it would have happened. That's basically due east of Wiesbaden. So, there was a lot of buildup of Armed Forces in that part of the Rhine Basin right after the War, and so there was tons and tons of Army brats.

ZIERLER: Obviously he picked up German.

EILER: His German was okay. My dad's German became very good because he was a kid there, and he picked it up then, and then when he was like early middle aged, he started taking weekly lessons from the high school German teacher at my high school. He started doing it before I was in high school. This is how he sort of got back into it. He has always had a very nostalgic connection—if you were to ask him all kinds of questions about German history and culture, he doesn't know that much about it. It's more like the vibe of the place, the nostalgic connection with his childhood experience there, that was always a very meaningful thing for him. I think learning German so that he could go back and travel there was always—and he still does that. That's probably the way I interact with him most. He's still alive. He's 85 now. He goes back to Europe, mostly Southern Germany, every year for like a month. He's a pretty vigorous person for his age so he can still just pull it off. I'll go with him for a week or two most summers.

ZIERLER: Did your grandparents live out their lives in Germany?

EILER: No, they then came back, before 1950. They probably came back in 1949 or something like that.

ZIERLER: What pulled them back?

EILER: I think just the job was done. He couldn't live forever there. They didn't really need him to be there forever. It was just time to get back. They then moved back into Central Indiana and lived there the rest of their lives. My grandmother died young, of like a heart attack, but then my grandfather lived long enough into his maybe early eighties, and he remarried, so I knew his second wife as my grandmother on that side. He spent the rest of his life there.

ZIERLER: What about your mom's side of the family?

EILER: My mom grew up in Ohio, so also a Midwesterner. Her mother was a child of the Depression and really—I suppose all of them were children of the Depression; she really was a child of the Depression. Like they were dirt poor, working class, urban Ohio folks. Her husband—

ZIERLER: What city? Cleveland?

EILER: Conneaut, a little town. But their extended family was very influential on my mom. My mom had a conflicted relationship with her mother for various reasons, but her aunts and her sort of extended family relatives were very influential on her. My mom was very committed to cooking and like being a master of her kitchen and her house and her garden. It sounds like a very conventional thing—like, oh, a mid-twentieth century woman running her household; okay, that was like the stereotypical role—it meant a lot to her. Her food, her kitchen, her garden—these things were very important to her. She had a real strength to her. She filled that role but she was doing it her way. You never had a sense that this was something that was imposed upon her. She picked that up, I think, a lot from being around these like farmhouse matrons in her extended family who ran big, complicated households and farms in Ohio.

Her father was adopted. We don't know really very much at all about his family. My mom's knowledge of her family tree, most of the family she could trace down were Welsh. Her family name, Nye is also a Welsh name. My mom was also really, really smart. She was smarter—my dad's an accomplished person, he's a physician and so forth; my mom was smarter than him. She was a very, very smart person, and a real intellectual, but also very committed to her private life and really wasn't that comfortable being outside of the home. So, she expressed it in unusual ways. She was a very voracious, deep reader. His library is just filled with deeply annotated and marked books. All of her reading in literature and philosophy and history and so forth, always just densely, densely marked texts.

ZIERLER: Did she go to college?

EILER: She did go to college. In fact, they met at college in—I'll remember the name of the college in a minute—where they went to college in Northern Indiana. She studied to be a school teacher. She was maybe an English major. She taught school for like a year, and then between moving around for my father's medical residencies and getting pregnant with my oldest brother, she stopped teaching and she really did not want to go back and do it. She wanted to live her own life at home but remain very engaged with her own internal intellectual life. She wrote a lot. She never published anything, but she often thought about publishing things. She had a lot going on inside her head that didn't get projected out into the wider community. But if I got anything from anybody intellectually, it was from her, for sure.

ZIERLER: What did your father specialize in? What kind of doctor was he?

EILER: Anesthesiology. His most unusual thing was early—well, two things. One, he was a runner when nobody was a runner. He ran every single day of his life from like late high school until his hips wouldn't work anymore. Now he walks, as if he was running, every day. He was a runner in the sixties when people would yell at him out of cars, like, "Go get a horse!" and crap like that.

ZIERLER: I remember in Forrest Gump when he was running and people were like, "What are you doing?" [laughs]

EILER: Yeah! And he was kind of a nerdy guy. Yeah, he is very Forrest Gump-like. The second thing is, he became really passionate about modern art in his early adulthood. He may have had a somewhat earlier formative experience like going into a modern art museum in Indianapolis or something like that, but where this really turned on for him was when he was in the Washington, D.C. area. During the Vietnam War, he was a resident or some sort of post-MD, pre-full-time-position job at the Annapolis Medical—the Naval medical center around D.C.

ZIERLER: The Naval Academy is in Annapolis.

EILER: Yeah, maybe—there's a hospital associated with it. That's where he was, and he was an officer in the Navy. We still have insurance through USAA that is like the insurance for veterans. I get to use it because he was an officer in the Army for years. Anyway, he went there for that reason, but then wandering around in downtown D.C. he just sort of pulled himself into a modern art museum when they were having a show of Sam Gilliam. Sam Gilliam at the time was a young man, probably in his twenties. He was what's called a color field painter. It's a branch of Modern painting that is Impressionistic but very free from the whole idea that you're depicting images of specific objects and things. You'd know it if you saw it. He died a year ago or two years ago, but he had a big renaissance over the last five years. You can find New York Times profiles about him, and they're having shows at the Whitney, and stuff like this. He was a super influential artist, and my dad saw his work right at the beginning of his career, and got so turned on by it that he just wanted to be involved in some way. He knew he wasn't going to be involved by becoming an artist—you know, leaving it all behind and becoming an artist. Although maybe, who knows, maybe he dreamed of it, given what his dad had done. But he became a collector.

He didn't have a lot of money, and he would form relationships with the artists and strike deals. Like, "Okay, I can't just walk in and buy your x-thousand-dollar finished piece that's in your gallery, but I can pay you 300 bucks a month, and then maybe once a year you make a piece for me, or then I can come to your studio and pick something that you're not showing, and that'll be for my collection. That way I can afford it, and you're getting something, and it all works." He did this with a couple of different people, and really these were like his main adulthood friendships, were these artists. There's something a little unusual about it, because it's kind of transactional, right?

ZIERLER: And he's an anesthesiologist. [laughs]

EILER: And he's an anesthesiologist. It all worked. He remained very close with these people. He was very close with Sam Gilliam through the end of his life. Their relationship kind of mutated in a way, where my dad also—he was a collector—his whole life, he collected art, and he was a pretty serious art collector, but he also had these manias for other things, kind of like Toad of Toad Hall, getting obsessed with something for a year or two. One of the things he really got into were vintage toys and model trains. He had his vintage toy period of a couple years, and he had his model train period of a couple years. Sam Gilliam also loved all of this stuff. They had been children at the same age, and so they had all the same kinds of experiences. They were quite different in their family backgrounds. Gilliam is Black. He grew up on the East Coast, had a very different experience growing up than my dad did in Indiana. But in terms of like the culture—

ZIERLER: Generationally.

EILER: —the generational material culture of like what was it like to be a child, what objects did you have, what objects did you covet, what did you see around you, they had a lot of this in common. So Gilliam would come and like pick nice things from my dad's toy collection and trade them to him for paintings and things like that. In the end, Gilliam's paintings became worth millions, and so my dad ended up like wealthy from this—

ZIERLER: Wow.

EILER: —but it had nothing to do with the money. Most of the artists whose works he collected never was worth anything. But he valued them, and those relationships were also very close. Gilliam, it just so happens, was a genius and a very influential artist. My dad got all of his pieces—if you were a big-time art collector, if you were a Broad or whatever and wanted to buy a Gilliam, you kinda gotta buy my dad's Gilliam, because he's the one who owned most of the things that were coming out of his studio when he was 30 years old.

Madison Upbringing

ZIERLER: Wow!

EILER: Yeah. It also really influenced me in a more direct way because the household I grew up in, in Madison, Wisconsin, was—the first house we lived in was just purchased off the market and was kind of a normal house in an older neighborhood. Then my dad and mom built a house on the outskirts of Madison in a neighborhood called Arbor Hills that at the time was just sort of empty. It was a newly made subdivision, like suburb. But it was in a peculiar place. It sat on the last big glacial sand deposits of the glaciation. So you're standing on this big, sandy hill and sort of looking off around the farmland around it. Then we shared a fence line with the Arboretum, which is the forest that the University of Wisconsin owns, and it's many square miles. So I basically grew up not in the woods, but like kind of on the woods.

ZIERLER: Was your dad connected to the university?

EILER: Actually, yeah. He had a courtesy appointment on the faculty of the medical school.

ZIERLER: But this is not what drew him to Madison?

EILER: No, he was recruited to Madison by the head of the anesthesia group, a guy named Phil Hoffman who lived up the street from us and was good friends with our family. He was recruited by him out of his residency and went to Madison just to work in a private practice. This was like pre-HMOs, and a private practice of specialists like anesthesiologists, first of all there wouldn't be very many of them. Pretty high status among all the different physicians. These are people who really only are going to surgeries and stuff. And they would work at multiple hospitals and have courtesy appointments and connections to the medical school because residents would come and work with them at their hospitals. He had a connection in that way. He wrote a scientific paper about a method he invented for intubation, which is the act of putting a breathing tube down your throat. He was like a wizard at doing this. He actually saved my older daughter's life because he was so good at intubation. He wrote a paper about his thing he called the lightwand intubation, and he couldn't get it published because he like didn't know anything about writing papers.

ZIERLER: [laughs]

EILER: I spent my whole life learning how to write papers, so you tell me to write a paper about a lightwand, and I will write you a great paper about a lightwand!

ZIERLER: [laughs]

EILER: He didn't know what to do! He sent it in to some journal and it came back with reviews and they asked for changes. He was so insulted by like, "Why should I change it? Why would you want me to change it? It's my paper!" So he was not cut out to be an academic. He couldn't quite engage in the dialectic with stupid reviewers.

ZIERLER: What happened with your daughter?

EILER: My daughter—now we're wandering—we'll come back to the art collection and all that stuff. My daughter, we lived in Madison when I was in graduate school. When she was 17 months old, she got a mosquito bite and got viral encephalitis, very severe. They never figured out—they can't titer most of these things, so you don't ever know an exact strain, but it was a very aggressive encephalitis. She was in a coma for a month. During the crisis of her coma, she was very close to dying. We were all in the university hospital watching some people try to care for her. She was losing her airway, losing the ability to breathe, and the attending physician had a resident there, or a physician's assistant, to try to intubate her, and they were screwing it up. My mom was with us there in the hospital, and early in this process, maybe half an hour before like the real crisis of it, she just got a bad feeling about—was just like, "Holy crap, these guys look like they're incompetent. This is going badly." She calls the hospital, calls my dad where he's working at the private hospital across town, and tells him, "You gotta get over here." He has a case, and so he's like, "What am I supposed to do?" One of his colleagues just overheard him and said, "Get outta here. I'll take your case." So he runs, jumps in his car, drives over, grabs a parking place, runs upstairs, and he runs into the room like the minute she has lost her airway, and is like—she's desaturating, she's probably a minute from being dead—and he just physically pushed everybody away from her and intubated her [snap] like that. Bang!

ZIERLER: Whoa!

EILER: Yeah. It was—

ZIERLER: Wow, wow!

EILER: —amazing. Yep.

ZIERLER: And you witnessed this?

EILER: Yeah, I was standing there in the room. Yeah, it was pretty incredible.

ZIERLER: And your daughter came out of it?

EILER: Oh yeah, she came out of it. She has permanent disabilities from the—epilepsy and brain injury and things like that. But, she lived, and she has a well-rounded adult life, and things like that.

ZIERLER: Oh my goodness. What a story!

EILER: It is. It's an incredible story.

ZIERLER: Were you born in Madison?

EILER: No, I was born in India-no-place, as we call Indianapolis.

ZIERLER: [laughs]

EILER: Then lived in—gosh, I'm trying to remember. We went from Indianapolis to D.C. and then to Madison. Before that, my dad had been in medical school in Saint Louis. Actually just by insane coincidence—my dad was in medical school at Saint Louis—this is just before I was born—the same year that my wife's dad was a resident in Saint Louis. Saint Louis has a great medical school, so it's not that weird that two successful physicians would have been there, but they were there at the same time. They knew each other.

ZIERLER: Do you have memories of Indianapolis and D.C.?

EILER: I have no memories of Indianapolis, but I do remember D.C. In fact, I'm very color blind, and my memories—when I started—my mom would ask me, "Oh, do you remember this house?" or "Do you remember that thing?" and I would tell her like, "Yeah, I totally remember that. I remember we had this like gray couch, and we'd watch the black and white TV"—and this and that. She was like, "The couch was that couch"—which was our purple couch. [laughs]

ZIERLER: [laughs]

EILER: She actually is the one who figured out I was color blind. I was going to kindergarten down the street. This was when we were in Madison. I was maybe four or five years old. I got a bad report from my kindergarten teacher sent home. I was a let's just say very unaccomplished student until about the age of 20. [laughs] When my mom died, we went through her paperwork, and she had so many crappy reports from school for me, but the oldest of them was this one, because I was "misbehaving during coloring" in art class by not following directions. The directions I was not following was to like paint the tree green and paint the trunk brown and whatever. I wasn't using the right crayons. Somehow this irritated the teacher for whatever reason. My mom then put it together that I had gotten confused when she threw an orange frisbee out into the yard, that I couldn't find it, and she was like, "Oh my God, he can't see colors." Anyway, she was the one who figured that out.

ZIERLER: You grew up in Madison your whole childhood?

EILER: Yeah, my whole childhood from age three on was in Madison. I went to Beloit College, which is just like an hour south of Madison, and then to University of Iowa, just following by to-be wife, because she wanted to go to Iowa. Then we went back to Madison for graduate school. So it was 27, 28—

ZIERLER: A very Midwestern life.

EILER: Very Midwestern life. I had traveled internationally but I had never lived anywhere other than university towns in the Midwest my whole life. That was all I really knew. Madison in the 1970s and 1980s was a very unusual town. It was a college town the way Ann Arbor is a college town and so forth, but you could still really feel the aftereffects, the reverberations of the antiwar movement. Like all my friends in high school, they had been in baby back carriers getting teargassed and stuff. Their parents were all involved in the antiwar movement, or a lot of them were artists in the Madison area or part of that scene, because my dad was part of that scene. So you really felt it. The town, it wasn't like, "Oh, everybody's running around like a hippie," but there was this kind of counterculture vibe. The punk scene took off there more than it would. Obviously the center of the punk scene was New York City and maybe a little bit L.A. in the years later, but early in the whole punk thing, you felt it there. It was picking up early leading-edge things in the culture.

I think combining that with a parenting style that was both generational, like a lot of people who were raised this way at that time, and idiosyncratic to my family, I could do anything, and did. I could go anywhere at any time, day or night. I had this very free rein run of both a big forest that was over the back fence of my yard—so like this immersion in open-ended nature, I could walk for miles in the woods—and, I could go downtown and do whatever the hell I wanted. I had this sense of just complete unobserved freedom. That was quite formative for me, I would say.

ZIERLER: Science, math? Were you on that track at all?

EILER: Terrible. Not at all. Not at all.

ZIERLER: That's amazing.

EILER: It is kind of amazing. I'm sure that there are other faculty members here who had the experience of not being successful academically when they were young.

ZIERLER: You're in the minority.

EILER: I'm probably in the minority. I knew when I got here as a postdoc I was in the minority in a bunch of ways. One of them was I didn't come from Harvard. I didn't come from Chicago. I came from the University of Iowa and the University of Wisconsin. I had no cross-section with high-end academia and didn't even know what it meant. Even at the stage where I was coming to start a postdoc, I didn't know what it meant. I had barely even seen it, even as a PhD student at Madison, and definitely as a young person, I had no idea what that was. Nobody in my extended family on either side had ever gotten an advanced degree other than my dad's medical degree. The idea you would become a scientist, it never entered my mind personally. I never ran across anybody who wanted to be a scientist. It just wasn't part of my world view, that that was a thing that you could do.

And, I didn't know that I was any good at it. I wasn't accomplished academically. I was threatened with being held back a year in grade school and then again in middle school. I was unaccomplished in high school. I guess I did fine on the SAT and things like that. If you sat me down to take one of these standardized tests, I did very well on them, and so I wasn't like below the water line in that sense. Actually, when I went to apply for college, I had a close girlfriend all through high school, and her family were like artists and intellectuals and social activists and things, and she had a lot of ambitions for her career and her college. I didn't. I never had any sense of what I—the question, "What will you be when you grow up?" never occurred to me.

Weightlifting and Troublemaking

ZIERLER: What was your social circle in high school? Sports? Drama? Writing? Doing your own thing?

EILER: Like D&D nerds and doing my own thing. I did a little sports, like I did a year of football and a year of track. But that wasn't like a big thing to me.

ZIERLER: There's no trajectory of your life at this point, where it's headed?

EILER: None, whatsoever. Before high school, honestly the thing that really lent some shape to my daily life was weightlifting, which is something I picked up in high school. As soon as I could get myself to a gym, I started doing that. That made sense to me. There are different subcultures of weightlifting, and today kind of everybody gets exposed to it; there's like the CrossFit thing and all that stuff. Proper barbell gym weightlifting, that's a different thing. It's a more intense sort of subculture. It's much more supportive than you would think. You might imagine, oh, everybody is competing with each other, and who's the strongest one; nobody gives a shit how much people lift. You're just there doing your own thing, making yourself better, camaraderie, learning things from people. That was very formative for me and gave my life a lot of structure in high school. The fact that I didn't naturally have a build for it, I didn't care. I was kind of a skinny kid. But I liked doing it. That was a big deal for me. Before that, honestly, my brothers had a punk band that I roadied for in middle school. You would think like, oh, in middle school, nobody can get up into much trouble. Ohhhh yeah, you can.

ZIERLER: [laughs]

EILER: 1980 in Madison, Wisconsin, hanging out with a bunch of skateboard punks, you can get into a lot of trouble, so I was going down a pretty bad path that way.

ZIERLER: You had access to pot and alcohol?

EILER: Oh, yeah, drugs are everywhere. No one is controlling anything. It's like if you ever saw The Ice Storm, imagine you're one of the kids in the ice storm, except you're not hanging out at home; you're gone. That was sort of my lifestyle. Then I imposed my own shape on it by going to the gym every day. It wasn't like these were my friends I would hang out with; most of them were adults, so I had no cross-section with them other than being in the gym. But it was a disciplined thing. You're not like a better person after you've done it, but you're focused on your own like growth and testing yourself and learning things, and just being in your body, and being around a lot of other people every day. It's like a community. That meant a lot to me.

ZIERLER: Was it an open question with you or your parents about whether you would go to college?

EILER: They never really raised the subject, honestly. Then I applied [laughs]—okay, I applied to the most inappropriate collection of colleges you could imagine for me—

ZIERLER: [laughs]

EILER: —given my lack of accomplishment [laughs] and focus. This was entirely my girlfriend's influence. She was like, "Oh! You're so smart." I'm like, "If you say so."

ZIERLER: [laughs]

EILER: "You should go to Harvard." Or Haverford, which is like—the only reason I even remember it is it sounds like Harvard, but somehow it meant something to her because a family friend of hers had gone there. Or Swarthmore, which another family friend of theirs had gone to. I was like, "Okay, I'll apply to those three!" That's what I did, and they all rejected me.

ZIERLER: [laughs]

EILER: And so like late spring, senior year, I had been rejected from every college I applied to. I had nowhere to go the next year. That was the moment where my parents noticed, like, oh, wait, he's supposed to be going to college next year, and he just told us he got rejected from all of them. That was when they sort of clicked that something was going on. Then my dad called a recruiting agent or the recruiting office or admissions office down at Beloit College, which is like an ACM liberal arts college an hour down the road from Madison, and said, "Hey, I'm sure you already did your class this year, but why don't you check this kid out and maybe you'll admit him?" They liked me. I met with the guy. And my SATs were good and stuff, so he was like, "Yeah, let's try that." That's how I got to Beloit College. When I went there, basically I did all the things that I had been doing before—lifted weights, drunk beer, hung out with people. I found a bunch of sort of outsider nerd types in the bar and music scene and hung out with them. I wasn't really a very interested student. If you had asked me halfway through freshman year of college, "What is going to happen with your life?" I would have been like, "That's kind of a stupid question. I have no idea."

Getting Into Geology

ZIERLER: Caltech professor is not going to be top of the list.

EILER: [laughs] No, absolutely not! That did not enter my mind at all. I had to pick a major, and I picked anthropology, because I was a big reader. I read a lot, and I knew a lot of history before I went—just myself, just privately. It had nothing to do with school. So I thought, oh, that could be interesting. But I didn't like them. When I showed up at the Anthropology Department, I felt like it was a bunch of dusty old guys dating their students, and their lectures were boring, and I had a job in the museum painting little numbers on flint chips and I thought it was stupid. It just did not click for me.

I was taking geology to fulfill my science prerequisite because it was obviously easier than doing other things, which it is. The teacher of my geology course was sort of the senior—he really built the department there. In the inner circles of college geology professors, he was a well-known guy. People knew him as a pretty serious person. It was Hank Woodard. He just died maybe two years ago. I don't know how he got a read on me, but he did. I was not doing well in his class in particular, but he liked talking to me. He would talk to me before and after class. He figured out that I knew how to do a lot of outdoorsy things, like I fished every day in the summers growing up, and so I really knew how to fish. I was big, so I could carry things and stuff. I knew how to canoe. I had been camping in remote areas in Canada as a kid. He figured this out and he invited me to be his porter for their field excursions.

ZIERLER: This is it. This is the story.

EILER: Yeah, exactly. That's how I got into geology. I didn't even do any geology on those trips. They would go out and do their mapping. I would go catch fish, I would clean fish, cook fish, clean camp.

ZIERLER: You were the roadie!

EILER: I was the roadie. I would carry all of his crap when we moved camps, carry canoes around and stuff. That was my role, but I could see what they were all doing, and I liked what they were doing, and I liked the people.

ZIERLER: Was he engaged in real research or this was teaching geology?

EILER: There's a hybrid between the two. You can't really be a good geologist unless you are comfortable making scientific observations in the field. That might be a controversial statement in 2023 because there's people who get to be professors and whatever—probably there's people going into the National Academy in geology who have never done that now. Whatever, that's their opinion. I would say you cannot be a geologist if you have not had the experience of doing this. You need to teach it to people, but you can't really teach it to them just by talking at them. They have to go do it. It's sort of like proctored research. He had his own long-term research program on the geological history of the assembly of the North American Craton. It wasn't a super serious research program that resulted in earth-shattering papers, but it was research. They were learning new things and making new observations, and the students were a part of that.

Yeah, so I loved that. That got my attention enough that I switched to that major. More importantly I just started identifying with that group, that community. My summer after my freshman year, I worked for one of the Geology Department professors picking little paleontological samples for him, which was just as stupid of a job as painting numbers on the flint chips, but a better community, a little more independence, a little more—there's more reason for it, more focus, and I enjoyed it. Even after that, I wouldn't have said I was on the path to becoming any kind of scientist. But I had already made a connection with my wife. We started dating spring of my freshman year.

ZIERLER: Where is your wife from? Also the Midwest?

EILER: She grew up in Walla Walla, Washington, but also spent a couple years in Iowa City, Iowa. Her family's roots were in Iowa City. Her grandparents were from there. On both sides, they were from Iowa, so that felt like a real connected place for her. How she got to Beloit College I can't even remember. It's sort of a shaggy-dog story. But she didn't like it. It was too small, people too much in each other's business. It was a little seedy, honestly. So she didn't like it, and she was leaving. She already knew she was leaving. She had decided to leave and move to Iowa City, transfer to Iowa City. She was a year ahead of me, so she was a sophomore. But she wanted to like date a little before she left. She had just had a breakup. And I was the one she picked! She was like, "Oh"—she saw me in the gym every day, and she was like, "Oh. That'll do."

ZIERLER: [laughs]

EILER: "I'll date him for a few weeks before I leave town." But it stuck. Then a semester later I moved with her, I followed her. After I moved to Iowa City—Iowa City was where I decided to become an academic, like to focus on being scholarly in some way.

ZIERLER: You're at a research university now.

EILER: I was at a research university. The bigger reason was [laughs] I didn't have any friends, okay? I showed up there. I'm obviously in classes because that's like why I'm there; I'm a university student. I'm a geology major so I guess I'm all in science classes. They made me take a bunch of survey classes because they were requirements and I hadn't met them by being at Beloit. So I found myself in these huge STEM classes—chemistry, introduction biology, stuff like that—with hundreds and hundreds of premed students. Other than my wife, I had no friends. I didn't know anybody. I had nothing to do. I couldn't like go hang out at the gym with a bunch of buddies. I couldn't go hang out at the bar. I was just like—nothing to do. So I thought, "Well, I'll just do this. I'll work, and that'll be my thing I do, just to try it." Then I also sort of—there's a competitive side to it. Like, you're being judged, and you look around in a class and like, "Oh, that's the top dog. That's the one that everybody thinks is the smart one." If you're in a huge STEM class full of premed students, well, they're all trying to be the ones who get the A's. So I thought, "I'll just do that. It's just a game but I'll do it. I bet I could beat them, so I'll just beat them, at that." For the first semester or so, that was my only thought, was like, "I have nothing else to do, so I'll be good at this." I discovered, oh, I can be very good at this. Like I can get the top score in all of these classes.

ZIERLER: You probably could have done this in seventh grade if you had the same—?

EILER: Maybe so, but it never occurred to me [laughs]. It never, ever occurred to me! But I was so much better at it than I would have thought. It was easy to be the best one out of 500 in chemistry, the best one out of 500 in biology. Like that. It was easy. I thought, they're rewarding me for this. I'm being told that I'm good at something. I'll just keep doing this. Then eventually I started developing interest in the work, but more interest in the people. I liked being around the people who were doing research.

Outdoors Culture and No Nobel Prizes

ZIERLER: You're succeeding throughout STEM but you stick with geology as a focus?

EILER: That's correct.

ZIERLER: Because you like that particular—?

EILER: It's just the community. I liked the people. That's all there is to it. They're—

ZIERLER: Outdoorsy.

EILER: They're outdoorsy. There's also a kind of unassuming character to the Earth sciences. Part of it—I never really realized it until I came to Caltech—we don't have a Nobel Prize. Thank God! [laughs]

ZIERLER: [laughs]

EILER: If you want to have a terrible dinner sometime, go to dinner with half a dozen people who all think they're going to get the Nobel Prize. Oh my God, they won't talk about anything else. You go to dinner with half a dozen geologists, they know they're not going to get the Nobel Prize. They can't. Like it's impossible. So all of that is removed from your radar. None of us are going to get rich. If I'm a chemistry professor, I can go invent some crazy thing and make a bunch of money. I can't get rich doing geology! Nobody cares! I mean, people are kind of interested in it when you discover something fun, but—it's about itself. It's not really about getting a prize or getting rich or whatever. You're doing it because of your own attraction to the field.

You would think, oh, that means I have the attraction to the field. Eh. Like, I could do other things. If you told me tomorrow, "Sorry, John, now you have to study the history of the Byzantine Empire," I'd be like, "Well, that's gonna be a transition, but, I'll do it. It's fine. I'll commit to it and just do it." It's not that big of a deal to me exactly what it is that I'm doing. I just like being around people who are interesting to talk to, who are all kind of unique. Earth scientists also interact with each other more, I think, like at the professorial level, maybe because we tend to have smaller groups, we don't get all these prizes and things. I think it makes us a little more—it's a little easier, just to get along with each other and interact with each other.

ZIERLER: Maybe this is where the phrase "down to Earth" comes from. [laughs]

EILER: Yeah, exactly! Also, it is fundamentally a different scientific enterprise from what people are doing in other areas of STEM. When you study the geosciences or the planetary sciences, every single thing you study is unique in some way, and every event is unique in some way, and the uniqueness of the things is what makes them special and interesting rather than some universal rule that binds them. Like of course we like to have understandings that stretch across many places and times and so forth, but always with a focus on and a respect for the uniqueness of distinctive events and places. That's just not what a chemist is thinking. When they're doing an experiment, they're not like, "This experiment is unlike any experiment that will ever happen before or since." That's a terrible result for them! They want to do an experiment that's exactly the same as every time before and after. It's just that they understand it and then can project out and predict them all.

I get it, I understand why they're doing what they're doing, but it's not what we're doing. We are basically doing history, detective work. There is a kind of idiosyncrasy that's just cooked into what we do that's different, and it appeals to me. I like it for the same reason that I like history. Nature is like this. If you go into nature, you're not like, "I want to see a triangular object that is mountain-sized." No! You want to see a mountain, like a specific one, and it's cool to you that it's that one, and that you've never been there before. Or that you've been there every day and now it's familiar to you. You want to have a relationship with that unique thing. That's sort of what becoming good at geology or at planetary science—you have to have this sense of developing a relationship with a unique specific thing. This is the thing about Caltech, is everybody here, everywhere you go, there is an intensity, a drive, a dialectical discourse. It's just all intense, in a great way. When I go to other places, even places that are famous schools—I won't name names because I'll end up getting dragged for it—but you go to famous universities, world-famous universities, and walk around and talk to people, and it's like somebody turned the volume down. It just feels—the edge is not there. I think that is the thing that took me a long time to learn when I came here. I showed up as a postdoc. I was Sam Epstein's postdoc, but really Ed Stolper was the person guiding me day to day. I had an early meeting with him, and he was like, "What are you going to do?" I said, "Well, I wrote chapter one and chapter two and chapter three and chapter four and chapter five of my thesis, and I have a great idea for a project. We can call it ‘chapter six of my thesis.'" [laughs] He was like, "No. We're not going to do that."

ZIERLER: [laughs]

EILER: "This is a terrible idea. Remove that. Wipe the slate clean." Just the sense of being shown, like, there is more. Reach for more! I knew what it meant to try and be as good as the best person I saw around myself. I didn't know what it meant to realize, it's not about you. The fact that I wrote a paper is not the important thing. It's that it got written, that it got done. This sense that there is something really grand out beyond yourself that is not about you, that is worthy and you should engage with, and do the best you can at—I didn't really get that, not in a real way, until I got here and saw the way that people here approach science, and the willingness to look at, judge, engage with, things that were not officially your job. That was amazing to me, to show up and see—the people jumping up and yelling angry, focused questions at the end of a seminar. they're not specialists in this. They're just somebody who wandered into the room—angry man yells at cloud—except it's focused on a scientific question. There was this intensity and it could be aimed at anything. I realized early on that I needed to remake myself here as a postdoc. I felt like, "Oh, I'm ready. I've written a few papers. I had a few successful talks. I'm ready go to be a professor." I wasn't even ready to be a postdoc! I needed to figure out how to operate on this higher level. I knew I had gifts in a technical sense, but none of it mattered if I couldn't engage with important questions, recognize them for what they were—

ZIERLER: This was a culture that you had not yet been exposed to.

EILER: I had never been exposed to this. Really the formative decision in my postdoc was when I told myself, "You are way behind the ball. You have to catch up. The only way I can catch up is by exposing myself to as much active scientific discussion as I can." So I decided, I will go to a seminar every single day, and not only will I go, I will ask questions. And not only will I ask questions, I will be a jerk [laughs] about my questions. I'll be engaged. And I don't care what it is. On Monday is our division seminar. On Tuesday I'll go to a planetary seminar. On Wednesday I'll go to an environmental seminar. Or I'll go over to chemistry or I'll go to physics. Thursday, geology. Friday, Seismo Lab, geophysics. Or other. It didn't matter. I never skipped a day.

ZIERLER: This almost sounds like your game plan when you got to Iowa.

EILER: Sort of, yeah, in a way. But I was very intentional that I knew, I just need to log the hours. I need to spend hours engaging with active, debated, live science problems in front of me across all these subjects.

ZIERLER: With people who are operating at the top of their game.

EILER: Exactly. And seeing how people here react to them, and myself reacting to them, really engaging with it, and doing it independent of subject. It makes me sad—I'll occasionally encounter a postdoc or a student or something here, who will tell me, "Oh, I'm not going to go to seminar today, because it isn't about something I'm doing." I can't even answer this. Like, that's exactly the seminar you should go to. You should be interested in everything and engage with everything. There is nothing somebody can present to you that follows the scientific method that you should not be able to follow and have opinions about or at least questions about. Engage with it! I really committed to that in a big way, and stuck to it, until I got too busy to do it every day, basically.

ZIERLER: When did you start to think about graduate school? You're at the top of your class at Iowa.

EILER: Yeah, I went to graduate school because my personal research advisors brought up the subject. At that point I knew, well, this is the only thing—

ZIERLER: You can do this.

EILER: Yeah, I obviously can do it, and it's the only thing I know to do, and why not.

ZIERLER: Coming out of Iowa, were your options limited?

EILER: They were very limited. I applied to Caltech and was rejected. The place I really wanted to go was Johns Hopkins because they had a professor there, John Ferry, who for the Earth sciences had an enormous, very influential group working on a subject that is now dead. That's a different line of discussion. I think one of the most important things you can learn about the sciences is to go through the full arc of watching a subdiscipline grow, become wildly popular, and then die, blow away in the wind.

ZIERLER: What did he work on? What was it?

EILER: He worked on fluid flow in the Earth's crust—which is an important thing; it's a problem that can never be fully dead like forever, because it's just connected to too many things—but the idea that that would be the subject that fills the big lecture hall at an international meeting, and a professor could have 11 students all working on it at once, which he did, and be like among the most well-recognized Earth scientists in the world for a few years—that's ridiculous. You could never be that, studying this question. We don't really have to go into exactly why it became so big and then fell apart so quickly, but I wanted part of it. I knew that it was a big thing.

ZIERLER: And you were well-read enough that—?

EILER: I was well-read enough to apply. He basically told me, "Eh, I've got too many people. I can't take on any more students." I was very happy with where I ended up at Madison, both because I had lived there before and because the person I worked with, John Valley, was a really great scientist. I could also have gone to Michigan or to UT Austin. I got rejected from a bunch of places. I applied to other top programs that I got rejected from. That never really bothered me. I also got rejected from almost every professor job I applied for. I applied for over 30 jobs and interviewed for 13 of them before I got an offer. I was a postdoc for four years. There were days when that was discouraging, mostly because I had a family. I had two children, in graduate school, and obviously a spouse who—I had to take care of the children. One of our children was sick. There was a lot of responsibility at home, and the main reason I wanted to be successful was so that I could support all of them. So I really would have taken basically any job, and luckily nobody [laughs] gave me one, because who knows where I would have ended up! Between college admission, grad school admission—I also got turned down for most of the postdocs I wanted to get, turned down for almost all these faculty jobs—I got very used to this, and it did not bother me. I never took it personally. I often thought it was stupid. Like I would apply for a job and think, like, "Are you kidding?" But I never really took it personally.

Back to Madison for Isotope Chemistry

ZIERLER: When you got back to Madison for graduate school, how focused were you? You knew geology at this point. Did you have a good idea of what you wanted to pursue for a dissertation?

EILER: No, not really. I knew I wanted to work in the study of the origin and evolution of the bedrock components of old mountain belts, mostly because it was an extension of the only thing I knew. That was what I had worked on as an undergraduate. But the person that I was working with, John Valley, this is what he did for a living, but he used a toolkit of isotope chemistry that he had picked up, sort of from one of the side branches of the main genealogy of isotope chemistry.

There was a guy named Jim O'Neil who had been trained at Caltech by Sam Epstein, and he then went and worked at the Geological Survey. He was a real intellectual, totally unique person, but in a job that was sort of off to the side of the real highly visible research universities. He ended up mentoring my advisor, John Valley, in the application of isotope chemistry to the study of rocks. That was the first time I had any cross-section with a part of the scientific endeavor that had a lot of technology involved—mass spectroscopy, trying to innovate at that, was part of that environment—and with the rigor of chemical physics. It was the first time I had encountered a core STEM discipline like physics or chemistry in a form where it was serious. I had obviously seen it as an undergraduate in survey class training and stuff. That's not the real thing. You have to see it in a research setting and see people who are struggling with the cutting edge of something. That's when you realize how it really works.

This was the first time I saw chemistry and physics and instrumentation and realized that those are things that can change because of what I do. I can somehow push that and make instrumentation change. I can make the knowledge of chemistry change. I can make the knowledge of physics change in some small way. Instead of being this dead thing that just sits on the page, it's a live thing. That was the first place where I encountered it. My thesis ended up being kind of weird because of that. I did a lot of theoretical modeling and exotic analyses in a way that today would sound routine. Like, okay, of course you would do numerical models of chemical processes, and of course you would experiment with exotic technologies, because we get exposed to them frequently now. Not then, you didn't. The early 1990s in a geology department, there was very little quantitative modeling, quantitative skillsets going on. The technologies that we had access to, they were really things from the 1940s and 1950s, so it was an unusual choice to steer into that as hard as I did.

ZIERLER: Was your research outpacing computational capacities at that time?

EILER: I wouldn't say that. It was outpacing my computational capacities. [laughs] It wasn't so much that I was doing something that was computationally so outrageous. It was that I was doing it in a context where it wasn't common. Basically the most impactful thing that I did as a PhD student was to describe in a way that was sort of physically grounded, and realistic you could say, how isotopes are redistributed between minerals as rocks cool and heat. They move around just due to Brownian motion at the scale of crystal lattices, diffusion, and then they are driven by the thermodynamics of how isotope mass changes the chemical properties of bonds. Isotopes are being traded between minerals as the minerals cool and heat, but then they're rate-limited by their capacity to diffuse through crystal structures.

The interaction between all of these things—the diffusion, the properties of the minerals, the thermodynamics of the minerals, the effects of the isotopes on the thermodynamics—people knew that there was something there, but it had always been described in kind of kludgy and inaccurate ways. Some famous scientists, at least in our small area famous, folks from Yale and other big-time East Coast schools, had worked on this problem and they had all the top papers in it, but they were not good papers. They had made bad mistakes, stupid approaches, simplifications. They just didn't get how it all should go together. I came up with a description of that, how it should work, and then tested that using analytical instruments that were really way beyond what people were using in common labs. For that, I traveled to the University of Edinburgh to work on an instrument called an ion microprobe. Not because they didn't exist anywhere else, but you needed a lot of access to beam time to make progress.

ZIERLER: This was as a graduate student?

EILER: As a grad student, yeah. The merging of ion microprobe measurements of isotopes at very precise levels with a new integration of how you should describe and mathematically model isotope mobility in rocks, that was my contribution as a grad student.

ZIERLER: How closely was this related to Valley's overall research?

EILER: It was absolutely related to it in the sense that he ran a stable isotope lab and he was interested in the thermal histories of rocks and he used stable isotopes to study these processes. And, he was the lead person forcing innovation on ion probes for these sorts of measurements. So I benefited enormously by being his apprentice.

ZIERLER: He was a real research leader.

EILER: Absolutely. He got into the National Academy a year or two ago, so—he's a serious guy. Having the opportunity to be the person on point with that effort—organized by him, led by him, but I was the one who did it—and then the application of that tool to this specific problem I'm describing—it's a kind of Rube Goldberg problem where you have all these moving parts that you have to figure out how you make them mesh, all these different physical and chemical processes. I found it very engaging as a puzzle, like how should you engineer the way you think about this so that all the different things are being accurately described and you get back something that nature actually does.

I think that experience of having a deep conceptual and numerical description of something and a cutting-edge analytical study of it and forcing those two into the same work really matured me as a scientist. I got to do things that were beyond what my advisor would do, and I did it by reaching out to other people. There was an assistant professor in our department at Madison at the time, a guy named Lukas Baumgartner, who was a very talented Swiss experiment petrologist. He was the one who knew all the numerical modeling business. He basically taught me how to take the tools of quantitative numerical science and adapt them to these sort of quirky, complicated, Earth science materials and problems.

ZIERLER: What was Valley's style like as a mentor? Did you work closely with him?

EILER: Yeah, I worked very closely with him. One of the things about being at a state university research environment—there are great people there. The programs are great-ish. They're not quite there, and it's because they're spotty. That means, as a supervisee or as an apprentice, you get much more attached to one individual. You don't have the sense that you are your own free-floating entity with many advisors. That's the case here. A senior student in my group, they are advised by many people. I would never say, "Oh yeah, that's my student, doing my project." They're doing their project. You really had to be much more closely aligned with your advisor in that setting. But he was very hands-off. He would present goals, and he set a standard of excellence, and he could be very critical, but he wouldn't micromanage, at all. In fact, my first year in grad school he wasn't even there. He was on sabbatical the whole time. I loved that. All my first wave of work that ended up being my master's thesis, I did when my advisor wasn't even in the country. Perfect. I got to figure it all out myself. I'd ask some questions now and then by email, or letter, or whatever it is we used to do—throwing paper airplanes across the Atlantic! But I had no sense that I was being micromanaged or that somebody needed to judge. I could just decide to do something and do it. That kind of independence, it was an important part of my childhood, has always been an important part of my intellectual style, and it was important to me at that stage as well.

When it came time for me to transition from my master's thesis—which, we had a program where you would definitely do a master's thesis that was its own thing, and then you would propose a PhD project. I knew it was time for me to transition to the full project of my PhD. And he wouldn't take my meetings! He was back in the country but he basically blew me off. He wouldn't even have the conversation with me for months. I don't know whether he did that with all of his students, or whether it was just some accident, or whatever was going on in his life, but it was exactly what I needed, because at that point I felt like I had just completed a project, I felt like it was successful. It wasn't the sort of thing that I was just describing to you a moment ago. It was some smaller project. I was ready to play it safe. I was basically like, okay, let's take that and puff it up a little bit.

He gave me his version of what Ed gave me when I showed up as a postdoc. Ed just laid it on the line and said, "Yeah, you're not going to do that. You've got to come up with something better." John Valley did the avoidant version of that. He just said, "You know, I don't want to talk about that. I don't have time to meet with you. I'm busy. Come back another day. Come back another week. I'll talk to you next month." I had to really stew on that and come up with my own idea, and it led me to do something much more ambitious and much weirder. The combination of skills and problems and types of papers that I wrote for my dissertation, I never would have written anything like that if I had been more directly guided.

A Formative Edinburgh Interlude

ZIERLER: Do you think there was a reasoning behind that, as far as he was concerned? Was he encouraging you along that path?

EILER: I don't know. I think he had a pretty good read on me. He never articulated it, exactly. But also he was reacting to what I was doing. Like I had to pitch to him—probably the most important moment in organizing what I did for my PhD is his colleague at Edinburgh who ran the ion probe lab where he was doing this really important technological advancement work, that person was visiting us right at the time when I was transitioning to a PhD project. I had to pitch to them, almost like a Shark Tank kind of situation. I gave it as a formal talk, but just to those two, of what I would do if I went to Edinburgh. I was proposing that I would go to Edinburgh also, and spend a whole summer there, and get lots of beam time, and have a bunch of ideas to test. I had to pitch to them, why should you spend really an enormous amount of money in terms of instrument time—because these are very expensive labs—on me? I had to pitch an idea that was one I really had cooked up on my own. So, he was reacting to me, in that way, but also, I was only in that situation because he encouraged me to do so.

ZIERLER: What did you learn about yourself in terms of what you were good at, during this experience?

EILER: I learned two things. One is I learned to really trust my instinct to do the thing I want to do, which is usually something peculiar and difficult. Like I want to do it not because it's hard, but because it's so distant from things that I knew the answer to. I wanted to do something that had as few connections as possible to an incremental advance of a well-established problem. I wanted to get outside of that and really explore. I don't always do that every single day. There's always a penalty for doing that. But that was my instinct. And it was a moment that taught me and reinforced, "Follow that instinct. Do that." The second thing is, I had no technological background, either in my undergraduate training or earlier in life. I had no formal training even in graduate school. I didn't know that I was good with instruments. The experience being in Edinburgh and basically being the person with my hands on the machine for a whole summer, doing really quite challenging things, that was a revelation—that like just put me in a room with a machine that is capable of doing things, and I will figure out a way to do something special with it. That—I had no idea that I could do that. And I didn't know that that would be—it took a while to figure out that it's unusual to be able to do that, in that way, and that I was good at it.

ZIERLER: Last question for today. What were the main conclusions of your thesis, and did they reverberate beyond Madison? Was it relevant to the larger field?

EILER: Oh my goodness. I'm hesitating, because—

ZIERLER: I'm establishing the story for how you get the postdoc at Caltech, because it's still not necessarily the trajectory that you're on.

EILER: It was definitely not the trajectory. I would say that the outcome of my thesis was a very realistic and sort of deeply described understanding of mechanistically what atoms do as you move rocks up and down in geological environments. You make them hot, or you make them cold, or you bury them, or you exhume them—what is happening? Just describe it to me.

ZIERLER: This is really bigger than geology.

EILER: I suppose it is. And the work remains highly cited. I hesitate to describe it as impactful, though, because—then what? How do you use that to then solve an applied problem? There are answers to that question.

The Importance of Intuition in Science

ZIERLER: But that's a bias for measuring impact, though. As a basic science thing—

EILER: Yeah, it is. I don't regret doing it, and I like the work. I still like those papers. It's a sort of aesthetic thing. Actually, why do I like those papers if their impact—? I can't point to an applied paper that uses that work and solves a problem that I would say, "That's a first-rank problem in the natural sciences." So, why do I like it? It's hard to say. I'm having a thought that reminds me of an earlier part of this discussion where we were talking about my childhood. When I was like a middle school and teenage-aged kid, we had artists in and out of the house all the time. They would do installations and build things in our house. That was a community I got exposed to, and I never knew it at the time, but they were exactly like the scientists that I like here. I didn't realize it until I got to Caltech, that really good artists—you would think, oh, they have this very elaborate idea in their head of a message they're trying to get across. Bullshit. They don't. They're thinking about, do I like how I cut this brush? Did I build this frame well? Did I stretch this canvas right? They're very focused on the tactile, physical things that they're doing, and then the meaning emerges out of their engagement with that material. Then I come here and I see like the scientists—you would think, these scientists, that they'd have this like, "Oh, there's problem x, and I am about to go solve it." No, this is not really what's going on. There's a lot of granular things in front of them that they're engaging with. It might be equipment. It might be complicated parts of theory. It might be materials that they're just interested in—like George Rossman is so obsessed with all these different minerals and their colors—and they just feel their way to something impactful by doing what feels right with these materials.

When I was writing those papers as a grad student, that's what I was doing. I said, "There is a problem in front of me. I don't know exactly what the big message will be. Maybe there isn't a message. Maybe I'm doing a Jackson Pollack painting that nobody can think there's a message in. It doesn't matter." The materials, the problem, the question—just asking yourself, what does an atom do, as you take a rock and move it up and down in the Earth—it seems like a stupid question, and maybe it is, but I found it engaging. I wanted to describe that, to understand that, to see it, just on its own merits. I think that's why I liked it.

ZIERLER: This is a statement of the power of intuition in science.

EILER: Yeah, I think that's right. It's partly intuition, and also I'm sort of reminded of something I often tell my students and postdocs and I really believe—people are not good at science. Science is good at science.

ZIERLER: [laughs]

EILER: The scientific method, it just does this stuff. It's almost like we're ants, and we don't know—like an ant doesn't know what the hell it's doing. It knows it's supposed to pick up a piece of sand and walk, okay? But if it just does it, incredible things will happen. We are very much like that. If you don't know that, if you think, Oh, no, I'm a special ant, I'm going to build Carnegie Hall,"—like, no, you're not. Pick up your rock and move, and that's you doing a good job. For us, it is engaging with the reality of what's in front of you in an honest way, whether it's the tactile reality of doing something with a piece of equipment or a material, or the intellectual reality of organizing a math problem or a numerical problem or something. Just be real about that, and good things are going to happen to you. Don't get pulled away by the deceptive thought of thinking you're bigger than that, thinking that you can somehow shortcut those things or not pay attention to them so that you can get to this goal. Your goal is probably stupid. Just do the real stuff that's in front of you and good things will emerge from it.

ZIERLER: A question to consider for next time; we'll pick up on this. I'm hearing an imbalance between the advanced work you were doing with Valley, your own intellectual maturation, a solid thesis—and yet, you came here, and you were like a fish out of water.

EILER: Yeah!

ZIERLER: We'll pick up on that next time.

EILER: That's a perfect place to pick up.

ZIERLER: We'll see how that connects.

EILER: Very good!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, October 20, 2023. It is great to be back with Professor John Eiler. John, once again, thank you for having me.

EILER: Yeah, thanks for continuing to work on this.

ZIERLER: The cliffhanger from last week, the imbalance that we were talking about between what you had accomplished for your graduate program, coming to Caltech and really feeling like a fish out of water—

EILER: Yes.

ZIERLER: —culturally, in terms of your preparedness. I asked you, the way that you narrated your graduate experience, clearly Valley was a serious guy.

EILER: Yeah.

ZIERLER: He probably could have been in a lot of places. He was in Wisconsin.

EILER: Right.

ZIERLER: You did a good thesis.

EILER: Right.

ZIERLER: Probably it was as good as what you might have accomplished had you been at a Harvard or a Stanford or whatever.

EILER: Very possibly. But the self-critique that I would still raise against what I had done at that point is, it had all the quality and innovation I could have possibly wanted to have included in a few papers' worth of science, but the sense that it should be aimed at something with impact wasn't part of my thinking. I was solving the problems that were in front of me, not finding the problems that I should be working on.

A Fish Out of Water at Caltech

ZIERLER: Are you saying this as a retrospective thought, once you got to Caltech?

EILER: Yeah, once I got to Caltech. I wouldn't have said that about my thesis work in the first year after I got to Caltech, but I felt it right away. I knew, okay, I believe in myself as a person able to grapple with scientific problems and do innovative things, but what is a scientific problem? What should I be using my ability to study? That's the first-order question, and it's a question that I never really asked in a serious way as a graduate student.

ZIERLER: Let's fast-forward, because now you're a mentor. Is this an expectation that you challenge your graduate students?

EILER: Absolutely, it is, and I'm guided in part by my own experience and the outcome I would want for them, but an even more powerful motivation and the way that I advise on this topic is—life is too short for me to spend all my time advising people who are functionally acting as a kind of echo chamber for me. I want to have all of the people around me, whether they are my senior colleagues or my junior colleagues or the most junior colleague like a SURF visiting from out of town or whatever, every one of them, I want that connection, that relationship, to be about something real. That is, both of us recognizing a shared interest in a scientific problem, both of us recognizing its value, and then going after it in some way. It doesn't have to be that every project is grandiose in its technical ambitions, but just to have a good reason to do it, and a reason that you share and maybe develop together.

When I pitch projects to students or postdocs, basically never will I sit down and say, "I've got these four projects in the lab and I would like you to pick one and do it"—and then you get to riff a little at the end of every tune, like a Jazz standard or something. That's not at all the dynamic. I will always sit down and talk with people about their general interests. What did they read last? What are they thinking about? What excites them? What are they curious about? I'm not going to accept everything that they say and then say, "Oh, yeah, of course I feel that way, too." But somehow in a dialogue we will talk our way, if possible, to an area of mutual interest and excitement, and then we'll cook up a project. It's not just like, oh, naturally that means it's project A. No, no. Let's go to the literature. What's happening in the literature? React to something other scientists are saying. React to something that has been discovered. That's our job, is to be part of this grand dialogue among people making discoveries and testing hypotheses and so forth. You need to be responding to what's happening out there at the moment, not sitting by yourself with your little checkoff list of project. I did that in a limited way in my own graduate experience, but I could see such a short distance. I basically found my way to something that felt innovative and like a good problem, but it was a good problem in a tiny room. I needed to see the bigger room to see bigger problems.

ZIERLER: Just as a thought experiment, could you have taken this entire experience and in a different environment applied your research to that bigger question?

EILER: Sure! Absolutely!

ZIERLER: What would that question have looked like?

EILER: That's a great question. What would I have studied, in the moment? If I could go back in time and apply the skills I had as a PhD student to the problems of that moment, I think I would have focused more on asking very critical questions about the way people were studying fluid mobility in the Earth's crust. Fluid on the Earth—basically the Earth has a lithosphere, a solid rock envelope; it has a metal sphere if you will, the core; and it has a fluid envelope at the surface, where we live. The interaction between that fluid envelope and the crust, that was probably the most prominent problem in petrology, in the study of rocks, at the time I was in graduate school. It had several different subdisciplines to it, but the big question was, how deep into the solid Earth do the fluids of the surface reach? How fully can they perfuse the crust and change its chemistry? There was a lot of focus on this, a lot of energy, and it was a little overcooked. It was a discipline that in retrospect was too arch. It had some pet ideas. It had gotten lost in highly quantitative modeling that was never going to go anywhere because they didn't know enough about fundamental processes. Working critically in that, really deconstructing the way that it worked, that's what I would have—should have done.

ZIERLER: Has the field addressed those questions?

EILER: No, it really didn't, not in a comprehensive way. If it had, it would have rejuvenated that subject. I can see glimmers of it coming back to life now, but basically that discipline kind of collapsed. It's something that I've seen two, three, four times over the course of my career—to watch from a close position a discipline grow, reach some sort of climax in visibility, activity, vigor, and then just as it gets too big for its own britches, it falls apart. I don't know if this is something that happens as frequently in the more fundamental STEM disciplines—chemistry, physics, and so forth. It happens to them in a way that feels very revolutionary, because when one world view falls apart and another replaces it, it changes all of the sciences. In geology it can happen in a big way, like our understanding of how geological time works and so forth, but it also happens in small ways, where a school of thought about some major Earth system, like the subduction of ocean floor into the Earth's interior and those consequences, or the interaction of the fluid and crust, things like this—they'll develop into very elaborate schools of thought that then collapse under their own weight, because the thing they're trying to study is not really subjectable—it can't be deconstructed like that. It's too idiosyncratic. It's too complex. We observe too little of it. If geologists are like detectives, because we come in after the crime and try, on sparse evidence, to figure out what happened, well then, an overly elaborate school of thought would be sort of like imagining that you could predict all crime, and that you like knew what all criminals looked like from the shapes of their skulls or something. It's clearly wrong, and it's never going to lead in a good direction.

ZIERLER: But there's a grand quest of extrapolatability.

EILER: Right, but we want to do it. We can't resist the temptation to do it. Yet it's destined to collapse, and it will collapse quickly. As soon as we think we've gotten very good at something, it will collapse.

ZIERLER: Because the big story is the planet is far too variegated to make those connections?

EILER: Right. It's more like, okay, I'm fascinated in the collapse of the Roman Empire, therefore I will create a theory of the collapse of all empires. It's just not going to go well. You're much better off just being scholarly in your study of the one or two or three things that you really understand, and feel your way gradually into these broader understandings, rather than trying to superimpose something really I would say arch—like, too overthought—on it. That happened to that discipline. It also happened to the discipline that was my greatest success as a postdoc, which is the study of the chemical consequences of subduction into the Earth's mantle. That also had a tremendous moment of popularity and vigor and visibility, and it collapsed. It is done very poorly now compared to the way that it was done in the era that I was interacting with all of the people who do this for a living. It had a very similar dynamic, just an attempt to overcook the evidence and overthink the processes.

Missing Plate Tectonics

ZIERLER: To set the stage before you get to Caltech, where does Caltech Geology loom in your mind? Are the Sharps and the Epsteins and the Wasserburgs out there? Are you thinking about Caltech institutionally?

EILER: Absolutely. Caltech has a unique position in the Earth sciences and has since the mid-1970s. Those people who really know, they know that there's multiple sides to this. There's things that we got and we led very aggressively. There's unique things about our culture as a department and as an institution that made us very different, very special. And there's things we missed that also defined who we are.

ZIERLER: Plate tectonics.

EILER: We missed plate tectonics! I'm so glad you know that! That shows you're—you're a real one. You get it.

ZIERLER: [laughs]

EILER: The fact that we missed plate tectonics, we will never live that down. It's like saying, "Oh, that guy that Darwin knew that didn't get evolution." It's like that. We missed that.

ZIERLER: Let me ask you—this is a very interesting point. I'm curious your perspective on this. Frank Press left because we weren't going to do plate tectonics. Another way of thinking about this—it's not necessarily that we missed the boat, but that the Caltech way is to either go all-in on something, or not at all. I wonder if you can comment on that, especially because we're not Scripps, we're not Lamont, we're not next to an ocean.

EILER: Exactly. I think our failure was cooked into who we are, and it was a consequence of our successes in other areas. It was sort of inevitable that we would fail at that specific endeavor for the reasons you mention. The discovery and really the explication of plate tectonics, that's the really important part of the science, is going from a vague concept to a quantitative description of what is happening. This again comes back to the idiosyncratic detail of the Earth sciences. If somebody just jumps up at a cocktail party and says, "I think the plates are moving!"—who cares? Sit down! Like, you don't know anything. You didn't see anything. It doesn't matter that you think that it works this way.

ZIERLER: [laughs]

EILER: It only matters that you have proven, through descriptive observation, in all its gory idiosyncratic detail, that it is happening. Then you know. That could only be done in the oceans. There was no way prior to satellite technology for us to prove unequivocally how this worked in real time, on land. We had to do it in the oceans, where the integrated consequences over time were so visibly obvious that they just couldn't be mistaken once you looked. And it had to be done with resources that absolutely demanded national-level infrastructure. A lot of the initial clues came through either military or military-adjacent—like the Merchant Marine—sort of surveying of magnetic navigation evidence in the oceans. The mapping of the strength and directional vectors of the Earth's magnetic field, that's what really sort of pulled people towards the critical evidence. That was being done for the purpose of navigation in the North Atlantic. Then all the sonar work with submarines, that was all military-related things for navigating coastal environments in the Pacific. It had nothing really to do with geological questions, and you had to be part of that community to really get it. It was going to be a technical advance with lots of connections to marine science, lots of connections to big national-scale infrastructure. This isn't our game. We were never going to be good at that in the way that other places would be good at it.

You can't sugar-coat it, though; it's the big story. It's like missing out on genetics or missing out on evolution or the Big Bang or whatever. We missed it. Part of it is because we couldn't help ourselves. It's just who we are. But we still missed it, and while missing it, we really were the foundational institution for modern planetary sciences. Starting from before then, but really powering through the plate tectonic era, we were the place that created the culture of high-end analytical geochemistry, especially isotope-related geochemistry.

ZIERLER: Where do you put seismology in all of this?

EILER: Seismology is obviously essential to it. It has deeper roots. Seismology is a lot of the critical data that proves plate tectonics' existence and how it works, but also they were looking right at that evidence for decades without knowing what they were seeing. They were guessing, and there were early ideas and so forth, but they didn't get-it-get-it until the evidence from marine topography and magnetics and so forth came together. We had a window on plate tectonics through seismology, but not the synthesis of it, not really the formulation of the theory, I would say.

ZIERLER: Let's go back. You were saying the mid-1970s is when Caltech Geology really established its place in the world.

EILER: Yeah, and I would say the most visible part to the outside world, of our Department—if you're in planetary sciences and you're part of the Voyager, Mariner, all the sort of first-wave solar system exploration programs, that's what you would think of when you thought of Caltech in that area. But that's a small community, relatively speaking. The bigger Earth science community, they really knew us through our geochemistry program, I would say, and its connection to geology. This sort of intimate marriage of laboratory geochemistry and field-based geology, that was a thing that we did extremely well. Then another—it's like a complicated Venn diagram, where the geochemistry is also interacting with cosmic chemistry, with solar system origins. It's interacting with lunar exploration. It's interacting with climate science, leading edge of environmental science, like Ralph Keeling, or Dave Keeling. The Keelings, who like did the CO2 curve, the older one was a postdoc here working with Sam Epstein. His very first observations were done on Mount Wilson. These sorts of very leading-edge reaches into all different branches of the Earth sciences, they were rooted in laboratory chemical and often isotopic analysis. That was really the thing that we were known for. Also the culture of that group was so extreme in its—it had a lot of different personalities. I was warned not to come here, because I was told that the people that I would work with, the really senior scientists at the time—Wasserburg, Silver, Patterson, and so forth—that, yeah, sure, they're the best scientists in the world, doing this, but they're so difficult! They're loud. They're aggressive. They're pushy.

ZIERLER: This was coming from Valley?

EILER: This was coming from everybody who I talked to, before—everybody thought of the Caltech—really they meant this handful of brontosauruses that sort of dominated the laboratory, mass spectroscopy-based geochemistry groups here. It wasn't everybody. It was really just three or four people kind of bouncing off each other. They were really extreme personalities. They trained virtually everybody who was influential in the field in the period when—when the folks here were entering midcareer, all the people they were training were then going off and founding groups other places. They had an extreme culture. They rubbed up against each other a lot. They were very opinionated about other programs and places and things. Really hard on visiting speakers. Very dialectical with visiting speakers. A lot of that, honestly, I kind of value. I think now that kind of culture is forbidden, and for good reasons, and it's destructive in a lot of ways, but if you can hack it and you kind of get it, it also has tremendous positive upsides. It exposes weaknesses to arguments very effectively. It leads to good ideas. It leads to good measurements. It's a very effective way of making scientific progress when everybody involved is up for it and wants to do that. Unfortunately, most people don't want to do that, and those people also can be great scientists; they just don't want to do it that way. So it was a little off-putting, I think. It was like a mixture of jealousy at our success—at that time it wasn't our success, it was their success; I was an outsider—a mixture of jealousy, fear, and feeling intimidated about the idea of going there and presenting your work, or just talking to people and having them ask you probing questions.

To this day, if I talk to one of my colleagues—I can go over next door to Woody Fischer, and if we have a conversation, I guarantee you we'll talk about the latest thing in our labs, and whoever is leading the conversation, the other one is definitely going to ask them something critical about it that could have an answer that reveals a problem. Great, love it. Not everybody loves that. And it was much more aggressive at that time, and much more public, much more visible. So that was something that was also a big part of our identity, of the Department's identity.

ZIERLER: And you're coming from the Midwest, of all places!

EILER: I'm coming from the Midwest. I didn't pay a lot of attention to these warnings that I got. I was told, "You don't want to go there. That's going to be a negative experience because of how negative the people are who are there." I had ups and downs. I had some very peculiar experiences being vetted by different people over the course of my postdoc, people who had different takes on me and had different ways of trying to figure out if I was any good. Maybe some people would have not flourished in that environment. It was a rough environment for the first couple of years, I would say. But I also loved it. I thought it was great.

Postdoctoral Paradise

ZIERLER: The original topic from today, talking about how your dissertation was smaller than it might otherwise have been, was your sense from your peers and the programs that they had come from before they got to Caltech, were they doing these grandiose dissertations?

EILER: No, this was very much my own internalized view of what I thought my job should be. But I think I was right! If you were to say, "Was my thesis a success?"—by the standards of the mode of reasonably successful PhDs in geochemistry in the 1990s, yeah, it was a success! I wrote four or five papers, and they're all highly cited to this day, and like, it was great. If I could get in a time machine and go forward 100 years and look back, would I think it mattered at some sense, that it moved the needle on an important question? Not really. It provided insight without impact. I would be critical and I think I would look back and think, "I could not know those papers, and I would be okay. I wouldn't be missing that much." I knew that at some instinctive level, then, when I came here.

ZIERLER: What about your level of preparation? How much did you know relative to your peers?

EILER: In some ways, I knew much more than my peers because of my classical training in petrology and my experience, my exposure, to a kind of analytical chemistry that is very demanding and innovative, expensive, difficult. I had seen things and done things that many of my colleagues had not done, so my basic technical skills were very good. What I lacked was any kind of understanding of what was occurring in the field around me. I had no understanding whatsoever of what constituted good physics or good chemistry or good biology. Other disciplines of the Earth sciences, I knew nothing about. I knew nothing about planetary science whatsoever. Astronomy, forget it. I didn't know anything outside of this narrow bubble of things that I had experienced in my own research and a few classes. I was just blind. It was like I was wandering around in a big, dark room filled with great stuff and I had no idea what was there. That was the weakness that I felt. And it was true. Both the strengths that I'm describing to you, and the weaknesses, were real, and I knew that I had to fix the weaknesses.

ZIERLER: This is just an administrative question. Do you come here to join a professor's group or do you come to the Division?

EILER: This is important, actually. At the end of my PhD I applied to a bunch of postdocs. I was turned down from the ones I wanted. I think I applied for a Prize Postdoc here and was turned down. Then I was hired on a faculty member's operating grant. You can come as a fellow and then you have a lot of intellectual freedom that's sort of independent of who your supervisor is. I suppose you might end up with somebody very pushy who pressures you to do things, but in general you have a lot of intellectual freedom, maybe enough that you don't get anything done. [laughs] Then the other route is somebody has an NSF grant or whatever and it has goals and timelines and whatever, and you show up to do the work and meet the goals and meet the deadlines. I was in the latter group. My fate in a situation like that was very dependent on exactly who my supervisor is. Luckily for me—I think I was identified first by Sam Epstein. He saw me give a talk at a national meeting and came up and talked to me afterwards and encouraged me to apply. I don't know what he was seeing, really, but he liked something about me and encouraged me to apply, and that was how I got on the radar of him and Ed Stolper. Ed Stolper was functionally my main advisor, even though it might have been Sam's grant or a joint grant or something that they had. I didn't really know Ed until I visited here. I had never met him until I visited here to interview for a postdoc.

ZIERLER: What was the dynamic between Ed and Sam?

EILER: Beautiful. A beautiful, beautiful relationship to watch. I just treasure the fact that I got to be part of that general relationship. It had a very familial feeling to it. Like they were colleagues and did research together. I don't know that they socialized with each other in some super-intimate way like they always had dinner with each other every week or something like that. I don't think that they really had that level of connection. They had lunch with each other every Saturday. That was a tradition. I'll tell you about that when we get to my experience here as a postdoc in a minute. But they had a connection that was more than collegial. I think Ed had a very deep respect for and affection for Sam both as a scientist and as a person.

Sam was not that easy of a person to read, because he had a very unusual kind of presentation. He came across as a little discombobulated. His public talks were kind of train wrecks of just like disorganized stuff. He was a little like that in conversation as well. But he had tremendous intuitive feel for science, for what should be done and why, and what was interesting, what was not interesting. He couldn't articulate it super well, but he definitely felt it and did it. He really understood what he was doing at the highest level of decision-making, which is exactly what I needed to be around. I didn't need Sam Epstein to teach me how to do numerical modeling or operate a laser in a lab. I knew how to do that. I needed to be around somebody who felt his way to the leading edge of scientific questions over and over and over again, and that's exactly what Sam was.

I think Ed really could see that in Sam and really appreciated it, but then also had this very personal connection with him. I almost felt like I was hanging out with a nephew and his uncle or something like that. I've spent my whole adult life basically with some kind of relationship with Ed. He was my postdoc supervisor. He then hired me. He was the provost when I was tenured. I was his son's PhD supervisor. We just have this long, long connection. I can't speak to exactly how close Ed and Sam were, but it has this quality to it. We are spending our lives together, basically, as colleagues, and it's more than just having a person in the office next door who knows what your last paper was.

ZIERLER: Was it common for them to share postdocs? Was your experience common?

EILER: Yeah, that was very common, and it is very common. Ed and I co-advise people constantly. We don't even know who's paying for what and who is the lead advisor. Who's to say? Who cares? Who cares! That's a very common arrangement. It's a kind of arrangement I have with other colleagues here as well where we co-advise people. It has a different quality with Ed, I think, when Ed and I co-advise people, because both of us think of it as—we don't sit around and talk about this, but I feel like both he and I recognize we are continuing this long line of being a community that has a cohesive culture that goes beyond just being neighbors in the hallway at work, and we are bringing young people into that community and helping them figure out what to do, and we're doing it together. We bring different things to the table. Often, what we're bringing to the table is we will argue and talk about things and this other person will listen, and see, oh, that's what an argument is. That's what it means to ask a question. That's what it means to be critical about something that has been done. Then others, as they get more confident and have more experience, then they will be part of it, and they get to start hitting the tennis ball on some of the volleys as well. It's just the idea that you are creating a little microculture that's sort of the scale of a family, almost, and that young people enter into it and they learn from everybody around them.

ZIERLER: Did you have a good sense of what you wanted to do, even before you got here, or it got handed to you?

EILER: I had so many hilarious conversations with Ed in that first year that I was here. I thought very highly of myself when I first arrived. I had a bunch of papers. These days, everybody has a bunch of papers when they're young. Then, it wasn't so common. First of all, you had to type them, okay? [laughs] Nobody has to do anything anymore! You basically pick up your computer and go, "Siri, write a paper about quantum physics," and then you go drink some coffee or whatever.

ZIERLER: [laughs]

EILER: I'm just as guilty as everybody else with using modern technology—internet, and laptops, and everything else, like that. I was literally typing on a typewriter and drafting figures with a pen and cutting out pieces of paper and crap like that. It was a very different era, and the fields operated differently. I felt very confident because I had written a variety of papers and had done well as a grad student. When I came here, my basic pitch to Ed was—he's like, "Okay, so what are you gonna do? Now you're here. We brought you in for this grant, but whatever, that doesn't matter. What are you gonna do?" I was like, "Oh, I'm gonna do my thesis—chapter six of my thesis"—which had five chapters—"I'll do the next one." He's like, "No, we're not going to do that."

While I was waffling about what I would do if I didn't do that, first of all he sent me some physical tasks, I had chores, okay? Every kid should have chores, so he gave me chores. One of my chores was to run his cold-seal pressure vessel lab, his experimental lab, to learn how it worked. How do you learn how it works? You're in charge of it. It's not like Ed walked down the hallway and said, "Okay, John, put on your dunce hat and sit in the corner, in your little shorts, and I'll show you what to do." He just said, "You're in charge of the cold-seal pressure lab, and I want it to work, so make it work." Of course I didn't know how, so I would then go ask his staff members, his senior postdocs, his senior grad students, learning what it was that I needed to do.

ZIERLER: What is the cold-seal pressure lab?

EILER: This is a laboratory for creating elevated pressures and temperatures in controlled environments and then observing the properties of materials under those conditions. It's a way of studying the thermodynamics of minerals and rocklike materials, studying chemical reactions at elevated temperature and pressure. I never really did very much of it. It was just one of my chores. Like just because your chore is to empty the dishwasher doesn't mean you know anything about dishes. It was one of my chores. Then another one was shaking down vacuum lines for stable isotope measurements in Sam Epstein's labs. Now, that is more my job, and I did more research on them, but really most of what I actually did was like mucking out the garage or something. It was in an unbelievable state of dilapidation, hysterically badly managed and set up, and I was tasked with somehow cleaning it up and making it work.

One of my favorite little vignettes—I don't know whether it will translate well to somebody who doesn't do this particular kind of science, but one of my jobs was to take a vacuum apparatus, the whole point of which is that it's under vacuum on the inside, and somehow make it all work and calibrate it and things. First of all, I'm looking at it and I'm like, "Wow, this is a mess." Then I take out the lab book. First step, let's read the lab book, log book. Wow, that's a mess, too. I go look at all the vacuum gauges and they're all very high, very—terrible vacuum. I go get Sam, who is down the hall, and I say, "Sam, what is wrong with this vacuum line? It like barely even has a vacuum in it." He goes, "It's fine. It's fine. The gauges are funny." I go, "Uh, okayyyyy." Then I start cleaning. I'm like cleaning, cleaning, cleaning. And I get up on a stool to clean the top of it, and I look down, and I can see there's a hole in the main manifold the size of my pinkie nail. I stick my thumb on it, and all the gauges go—whannnnnng!

ZIERLER: [laughs]

EILER: They drop down to vacuum. I looked in the log book; they had been like this for like 15 years. Like no one had ever—probably it was like this when it was installed! And no one ever put their thumb on the stupid hole and made it actually be a vacuum line! It was like, "Oh my God!" Like, "Where am I?" This is the kind of crap that I was doing when I first arrived here. My project, it was a good project—eventually, then Ed and Sam were like, "Okay, while you're getting yourself sorted, work on this"—it was to study how the isotopes of carbon are fractionated between vapor—carbon dioxide vapor—and carbon dioxide dissolved in magma. It's a good problem. It's a thing you would use to study explosive volcanism and the way that gases get out of magmas as they ascend towards the surface. Perfectly good problem; it wasn't a good problem for me. The experimental apparatus we had, the experimental design, it was all a little kludgy. It wasn't working very well. I don't think I ever generated any data that were publishable. But it kept my hands busy for a few months.

Then something really wonderful happened that I would say was effectively the turning point in my career. It was a reading group that Ed ran—which in fact I will go to immediately after our interview today, because he still runs it—a petrology reading group where we would read current papers and just talk about them, usually trash-talk them or whatever. You would think, well, what's such a big deal about that? It was the mindset I was bringing to it. I was in this context where I felt like every single day, I need to do something that makes me better at picking problems or working on problems. Going to all these seminars, going to planetary science seminars and geophysics seminars, and blah-blah-blah—just every day trying to get better, and that included going to paper groups, reading groups.

In Ed's reading group, we read a paper that pretty much everybody liked that was about the study of the isotopes of oxygen as tracers of material from the Earth's surface that had been subducted into the interior and then stirred, creating chemical anomalies in the Earth's mantle, and then those chemical anomalies contribute to the properties of magmas that come from melting the mantle. It's basically a way of tracing the passage of material from the Earth's surface, where its fluid envelopes have changed the chemistry, through the entire plate tectonic cycle and back up to the surface in magmas, and watching how that all occurs. Where does it occur? Is it everywhere on the Earth? Is it only in certain places? What are the changes correlated with? How does it change the properties of the magmas? There's a lot to it. It's a very rich problem. The isotopes of oxygen are a good way to do it, because the isotopes of oxygen are strongly separated, fractionated from each other, when water interacts with solids—minerals and rocks—at low temperatures. That happens everywhere on the Earth's surface, and you create this signature, and down the tubes it goes.

We read a paper in a prominent journal, maybe Nature, from another group that had used this tool to do exactly what I'm describing. Everybody liked it, and I hated it. I said, "This paper is garbage." Because the measurements were not done well. The samples they chose were clearly compromised by weathering, and things like that, that happened at the surface. The whole thing should have been thrown out. It was terrible. That kind of trash-talking is not uncommon in reading groups. It's sort of the point, is like to deconstruct things and think about how they should have been done. But it only becomes useful if then you think of a good way forward. Well, then what should have been done? Ed told me, "If you're so smart, well, then you do it better." It's one thing to be critical of things and another to actually fix them, make them better.

The obvious logistical problems are, well, how am I going to—? To make the measurement I think should be made, I have to go somewhere else. Fine, go somewhere else. I need samples, special samples, from a special place. Fine, get them. Here, I know a colleague; they'll give them to you. Yeah, but what about all these other projects I'm doing? So what? Do this one instead. This sense of complete freedom, where we're not going to belittle the process by arguing about how much it costs to fly somewhere, or whether we picked up the samples ourselves or we have to ask a friend for help, or are we going to make the measurement in our own labs out of some sense of pride or whatever, or would we go somewhere where we think we can do it better. Just do it. Just make it happen the way you think it should happen.

And I did, and it worked beautifully, completely overturned that paper, and it led to a kind of paper that is honestly my favorite sort of paper in geochemistry, the null result paper, where instead of saying, "I have discovered something completely crazy, pay attention to me because of the crazy thing I found," you instead say, "There is nothing crazy here. I have shown to every level of precision imaginable that everything here is exactly normal and as it should be." If you've correctly framed the problem, you understand what a signal would mean, you are very confident in what you've observed, and then the null result is the most powerful vote there. Wild, insane findings, they could reflect any number of things. You're noticing them because you've never seen them before, and so you don't really understand how to interpret them. It ended up being a really helpful, influential paper. It drew on my experience at Madison. I flew back to Wisconsin to make the measurements.

ZIERLER: Oh, wow.

EILER: Basically I knew this should be done using a special kind of laser-aided chemical extraction of oxygen from minerals that's much more efficient, much more precise, than what other groups are doing.

ZIERLER: You went back to Valley's lab?

EILER: I went back to Valley's lab! Because I knew that they had a device there and it worked, because I had been there, and I knew how to use it.

Isotopes and Ocean Basins

ZIERLER: Let's go into a little more detail about the original paper. What did it argue and what was problematic about it?

EILER: The original paper argued that—first of all, as backstory, when you study the abundances of the radiogenic isotopes, the isotopes that are products of radioactive decay, things like exotic isotopes of strontium, neodymium, lead, these are trace elements that have rare isotopes that accumulate slowly through radioactive decay. We use them for dating rocks, but we also use them for tracing ancient rocks of certain chemical affinities. When you go and measure these rare isotope systems in volcanic rocks through the ocean basins, you notice that some of them have isotopic signatures if you will, compositions, that remind you of ancient crustal rocks from the continents. That resemblance suggests that they are ancient continental material that weathered, eroded, was transported into the ocean somewhere, subducted, stirred around, and now is coming back out, and is influencing the chemistry of the new basalts that you just sampled.

To confirm that, it's actually more useful, if you can do it right, to do exactly the same thing but with the isotopes of oxygen. Why? Because the trace elements like strontium and lead and so forth, they're so variable in their concentration, you don't really know how much. If you see the signature, you don't know whether that's a little teeny, teeny, teeny bit of something with a lot of lead in it, or a vast amount of something with no lead in it, so the physical meaning of the measurement is very unclear. Oxygen—basically most of the volume of the Earth is oxygen atoms. Every common rock type, every common fluid, is mostly oxygen. So oxygen is a wonderful tracer of amount of stuff. If you recognize an isotopic signature that's distinctive, perfect. You get like mixing ratios, things like this. That was what this paper was trying to do, and they reported a very extreme positive result, that when they found these radiogenic isotope signatures of subducted crust, they found a very strong signature of oxygen from subducted crust, therefore what they would surmise happened is crustal rocks were subducted, they basically floated around as big chunks, came up underneath a volcanic island, and melted, and they contributed vast amounts of mass to the volcano. The volcano was basically melted crust that was subducted.

I came in and did this in a different way, a better measurement technique. My critique was the samples they measured, they have surface oxygen because you collected them at the surface. [laughs] They were glasses that were hydrated, and like they clearly were not primary magmas. They had undergone surface weathering processes and things like that. They were badly compromised for that reason. I knew a way to recover refractory minerals—olivine—that can't really be weathered—you'll notice for sure if they're weathered at all. You can get very fresh grains of them. You can't get the oxygen out of these sorts of refractory minerals without a laser, so nobody really studied them. I knew that these lasers existed and were a good way to get oxygen out of solids for isotopic analysis, so I just put two and two together, went to Madison with the appropriate samples, did a study, showed there's absolutely no signature in oxygen. Your interpretation of the original finding, then, is turned on its head. You would say, oh, yeah, for sure the lead and the strontium and all these trace constituents, they're there, and maybe they come originally from subducted crust or from some other process, something happening in the mantle, but the substance of the mantle beneath this volcano is totally normal. It is not a big block of subducted crust. You have changed your mind about what is the fate of plates. How does the fate of a subducted plate connect to the generation of a future volcano? Opposite answer.

ZIERLER: This is the kind of answer that's big—

EILER: That's a big answer!

ZIERLER: —that you were lacking through the dissertation.

EILER: Exactly. I was able to comment on not just some thought about the best way to describe how atoms vibrate around in a mineral. That was what I was working on as a student. I could comment on the way the Earth behaves and evolves. Not everybody is interested in subduction and the origin of volcanoes. But they should be a little bit interested. It's part of the Earth you live on, and it's how the Earth evolves and how it behaves at the biggest scales. I had found a way, first of all, by having some technical skills and understanding that they could be translated from one subject to another, one field to another. And, I was a bit of a jerk, okay? I had picked up on the aggressive culture, the probing, the questioning, the lack of deference to outside papers, studies, and things. I could pick up this paper that was getting a lot of good press, a lot of people liked it, and I could say, "Garbage! I am going to undo this!" Which, it's not the nicest thing to say, but in the end it was the right thing to say.

ZIERLER: Science is after truth. It's not after being nice.

EILER: Exactly. It's not about—I love to tell this to my students—"You're great. It's wonderful that you like your job. This is not about you. This is not about me. This is about the integrity of your description of what you did. You don't even have to do it right. You just have to honestly describe what happened. ‘This is what I did. Here is the honest result.' Then what you think it means—okay, that's negotiable."

ZIERLER: You're getting at something deeper here, which is why scientific fraud is so bad.

EILER: It's incredibly corrosive. But it occurs in many different ways. This gets back to something I said to you maybe in our first or second time together, that I feel like humans are bad at science. We're terrible at this. It's incredible we figured out how to do it at all. When you supervise a lot of people doing difficult laboratory measurements, you see it exposed over and over and over again. Of course there's the n-member case of people who intentionally manipulate what they say about outcomes and from their work to get some attention or result or whatever. Yeah, I'm sure this happens, but we like to imagine it's rare. I keep my eye open for it very aggressively. If it has happened in my group, then somebody was very tricky about it. But there's this other much more common thing of just human nature, people making dumb decisions just as mistakes with no motivation, or they feel like they're doing the right thing—

ZIERLER: Or there's confirmation bias.

EILER: Confirmation bias. The biggest problem is every raw data stream you generate with a modern analytical instrument generates a vast amount of metadata, and a digital data stream that's very rich. There's a lot in it. And you don't report all of it. You summarize it. The act of taking a raw data stream that is so complex and turning it into a deliverable, that's a human activity. You decided to do something. Even if you automate it, you decided how to automate it. So, how do you do this? The human-nature way of doing it is sort of by feel. You'll look at it and you'll just feel like that's good and that's bad, or that should be averaged and that shouldn't or whatever, or I should stop my experiment now and not later. This of course is like—you're finished. Every day you're going to make a bad decision if you do this. You need to somehow reduce what you're doing to rules.

The rule of thumb in my group that I tell absolutely everybody is, "Of course you're going to cull data. That's the nature of reporting. It's a kind of culling, in a way. But you have to make it so that any human being on Earth, if you hand your written recipe for your data culling and your pile of raw data files that have had absolutely nothing done to them, they will come and hand me a data table in the end that's identical to machine precision with what you handed me." That has to be the level of clarity, of transparency. That, I think, is the actual goal, is to just be transparent, so that you become invisible. It's not you. You are just like the agent that delivered this information along with a key that tells people, "If I made a mistake—and probably I did, somewhere—here is the decoder ring that will let you go back and figure out what mistake I made." It has gotten a lot easier, in a way—not morally, but like technologically—because our raw data now almost always comes in these very packaged-up forms that we had almost nothing to do with the way they were created. Then it's possible to describe what you do with those in a way that is very specific.

ZIERLER: Ed knew the lab that you came from. He put this paper in front of you. Is there a level of omniscience on his part where he was teeing you up to do this?

EILER: I love Ed, and he's a genius; he's not that kind of genius. [laughs]

ZIERLER: [laughs]

EILER: He didn't figure that out. No, we were reading the paper because everybody was reading the paper. It was a paper in Nature. His group studies the origin and evolution of igneous rocks, of volcanoes, so of course he's going to read this paper in reading group. I was a smartass about it, and he said, "Put my money where your mouth is," basically. "If you're so convinced, prove it." He was responding to my reaction, really. Basically it was the first instance after I came here where I took—I hadn't even perceived that my ability to recognize good problems had been improving. I was trying to improve it, but where's the proof that it's working? That was the first proof that I was willing and able to identify something that I could personally do that would matter and for it to be a good-sounding choice. He was there to support that. That's his genius, is he knew to support it when he heard it.

A Miracle Year in Geology

ZIERLER: Does Ed have an independent research identity from his students, or is what Ed does inextricably linked with what his students do?

EILER: That's a very good question. It's a good question for every scientist who is in a supervisory role.

ZIERLER: You saw it from the postdoc perspective.

EILER: Yes. He has a unique vision as a scientist and he maintains a unique identity in his self-cultivation of his interests and in his insight. First of all, an important thing to know about him, if you don't know that much about his scientific background, is he had a wonder year that is topologically similar to Einstein's wonder year. Smaller stakes than Einstein—that's why Ed doesn't have a Nobel Prize—but in our field, he did kind of what Einstein did as a young person. When he was here as an assistant professor, he wrote, in a period of order one year, four papers in four very different subjects, all of them quite technical and fundamental, and each of which then gave rise to a subdiscipline and really changed their fields. This is the level of his gift as a scientist. Then he also has very strong fundamentals. He was trained in thermodynamics by one of the greatest persons ever to study the thermodynamics of natural materials, and really is passionate about that. Then he has a very interesting taste for weird things. His most recent thing he did that I think shows his maintaining of a distinctive scientific identity is he did a bunch of work on the zonation of phosphorus in olivine, which even as he was doing it other people would look at, including myself, and think, like, "What are you—?" Like, "Have you lost it, man?"

ZIERLER: [laughs]

EILER: Like, "This seems really stupid." First of all, who cares how much phosphorus is in olivine? He was fascinated by it because you could make maps of how much phosphorus is in olivine. You take this mineral—it's totally bland and boring-looking in a way, and yet it's ubiquitous. It's the most abundant mineral in the Earth's mantle. It's the main first mineral that grows out of magmas when they grow. It's a really important mineral. Unfortunately, it's very boring. There's almost nothing to it. You look at it in a map of phosphorus, and suddenly it's incredibly fascinating. It's textured, variegated, wild variations in zonation patterns that all reflect the way in which it grew, how quickly it grew, what the melt was like around it as it grew, how hot it was, did it dissolve a little and then regrew. Its whole history is written in its phosphorus zoning. He went after it not with any specific goal in mind, I don't think. It's not like he thought, "Okay, problem x that everybody is arguing about, I am going to solve with this." He did it because he wanted to do it. In the end I think it provided a new way of understanding the growth of what is arguably the most abundant and important Earth material. Any new insight you get into it is important. Just his way of finding some way to see something new in an old thing that nobody else had ever seen or even thought about—he's still got it, in that respect.

ZIERLER: When you called out this Nature paper, did you publish in Nature?

EILER: Oh, yeah! Yeah.

ZIERLER: How was that received?

EILER: Very well. That was good. That remains a well-cited paper. Then that approach of studying the origin of igneous rocks in this way, using their isotopes of oxygen, I then set up a little cottage industry of working on that, and that body of work was the foundation of my being hired here as a faculty member. It was for sure the most prominent body of work that I had published at the time I was tenured, so really the first big wave of success as a professional scientist. The papers I did as a PhD, they remained cited, they were good; the work on the oxygen isotopes in the igneous rocks, that was my first big thing.

ZIERLER: Did this resolve your feelings of dislocation about whether you belonged at a place like Caltech?

EILER: Yes and no. It temporarily assuaged those feelings, but then when I was tenured, they came roaring back.

ZIERLER: [laughs]

EILER: Because I knew that what I had done was basically like a clever chess move, a kind of gamesmanship, where all the pieces are on the table, the rules are known, you have a certain puzzle in front of you, and you see the correct move and make it. That's fine. I don't feel like that is what is the best thing I have to give to the sciences. The person I really wanted to be emulating was Epstein. Epstein was never playing chess. With Epstein, you think you're playing chess; he's riding a rocket to Jupiter. [laughs]

ZIERLER: [laughs]

EILER: He's just like [laughs]—he is doing his thing, and he will do it however he sees fit, in whatever direction catches his interest, and it all sounds totally chaotic until you look back on it and realize, oh, you just created a new branch of cosmochemistry. Oh, you just created a new way of studying metabolism. Just things would just come out of him spontaneously. Of course there's a process inside. He had a head like a garbage can, just like a huge head, and I'm sure he had an enormous brain inside there!

ZIERLER: [laughs]

EILER: He could not articulate to you his process, not in my experience anyway, but it obviously worked. That appealed to me. I perfectly understand not every scientist should want to operate that way. If you're trying to solve a focused problem, you can't operate like that. It's too chaotic. But it's what I wanted to do. When I was coming up for tenure, I had basically had enough of oxygen isotopes in magmas. If I never see another grain of olivine, it would be too soon. But I knew there had to be something more that I could do and wanted to do. In a way, it was like that same feeling I had when I got here, but transmutated into—rather than catching up, I wanted to somehow get out ahead, or get free, or something. I conceptualize it as just seeking out open water. Just get out into open water where you can move freely, you don't know anything that's around you, you are truly exploring. That was what I wanted to create for myself.

ZIERLER: As a postdoc, what was your sense of the integration or not of the Seismo Lab with the rest of the Division?

EILER: That's a really good question. Our structure—there are six options in the Division. In a way it's a microcosm of the Institute, the way the options work. They are smart things institutionally because an option isn't so serious that it has to live forever. If somebody said, "We're going to dissolve the Department of Biology," you'd be like, "You're gonna what? You can't do that." Departments, they are so administrative, they're so permanent-seeming, they become fixed and therefore conservative. Options, why not make another option? Why not kill an option?

ZIERLER: It's an option!

EILER: Who cares? [laughs] They're all optional! Exactly! The whole thing is optional. Some of our options, when you're inside them, they still feel that way. If you told me tomorrow, "Sorry, John, your lab's fine, we're not going to fire you or anything, but the geochemistry option no longer exists," I'd be like, "Who cares? What does this have to do with anything?" The people within a subset of our options really act that way. Geobiology, geochemistry, geology, a good half of planetary science, it's just all pudding, all the way down. It's just all the same thing. People move around. They have different interests. They work together in different combinations.

ZIERLER: Is it because it's all geology?

EILER: It's all geology. Everybody involved is studying natural materials with a similar mindset of how you go about solving problems. We speak a common language. Other options, they really are just their own thing. They're just doing their own thing. The Seismo Lab was sort of set up to be that way from the beginning because of how it was administratively created. Planetary science and geobiology here, they were created intentionally from nothing, where there's just a void and we come in, and like God, we turn chaos into order and create this thing. The Seismo Lab existed as a separate institution and we basically—

ZIERLER: It predates Caltech.

EILER: Yeah, it predates Caltech, and we basically acquired it. It doesn't help that the discipline as a whole, the things that it observes and its mindset about history—how do I study seismology in the past? Mostly you don't. You study seismology as it is occurring right in front of you. The same is true of a lot of the satellite-based remote sensing data products, all of the interferometry and things like that. It's very present-focused, structure-focused. As kinematics is to dynamics, or something like that, so is geophysics to geology. It's a description of this current state. The geologists look around and we're like, we have our heads totally up our butts. We're just thinking constantly in four dimensions, and thinking about the past, and evolution. Instead of seeing comprehensively a simple thing, we see partially but with great complexity. We'll see little snippets of many different sides of a problem; they will see a carpet bomb of the velocity structure of something. It's just a very different way of going about working. So those disciplines, they're very collegial, like we like each other's work and pay attention to each other, but there isn't an easy way to share students or sit down and do projects together. It can happen, but it's not as easy as when geologists and geochemists and things like that sit down.

ZIERLER: When you arrived, the Seismo Lab had been located to North Mudd. That had happened 15 years ago. But from what you're saying, administratively, intellectually, in certain cases it's almost as if they could have still been up in the San Rafael Hills.

EILER: In some ways. I would say my colleagues in geophysics, in the Seismo Lab, I feel just as collegially connected to them as I do my other colleagues, but the nature of the connection is different because we can't work together in the same way. Then they also have another side to their identity that's very hard-wired—it's baked into the Seismo Lab—that they like manage a network and they are part of the hazards evaluation. They have a mission that's very specific.

ZIERLER: And also in front of the news cameras during an earthquake.

EILER: Yeah, no news cameras need to talk to me. This is not important to anybody's news consumption, what I have to say about anything. They're public-facing, immediate. There's a service component to what they do. There's an educational component to what they do. They have a lot of things going on that are beyond what an academic option would normally entail.

ZIERLER: What about JPL? When you got here, were you aware that there was a new era of Mars exploration on the horizon, that we're sending a rover to Mars in just a few years?

EILER: Absolutely not. [laughs] I had absolutely no idea that anybody did anything with planets [laughs].

ZIERLER: Did you even associate Caltech and JPL?

EILER: I didn't! When I came here as a postdoc, that was all fresh to me. I had no real concept of it. I didn't really have an appreciation for what had happened at Caltech and JPL during the Viking era or any other of the big periods of solar system exploration. It was all just darkness to me. I didn't know any of it.

ZIERLER: What about Ed supervising students like Laurie Leshin? Did that register with you, that he had an expertise that was relevant for Mars science?

EILER: Not before I came. I came here right at the end of Laurie Leshin's PhD, so I overlapped with her. Her, me—Paul Asimow was a grad student in the group then. Mike Brown was a postdoc just about the same time. Ken had just been hired as an assistant professor. All different roles, we had different jobs, but we were basically all the same age doing the same things. Mark Simons also came in as a postdoc about the same time. Part of my learning about these other areas of science was just learning about these colleagues of mine who were coming in at the same career stage.

ZIERLER: Did you ever go up to JPL? Were you curious? Or this all comes later?

EILER: That comes much later. I did find my way to Mars research fairly quickly, though. I did it as a postdoc. This is another one of these cases where a paper gets published, everybody loses their mind over it, but it's order of magnitude bigger than what I described to you before, and I found a way to get involved, and Ed helped me do that. John Valley helped me do that as well. In 1996, I think—so it was near my second year as a postdoc—I was a four-year postdoc, which is not my greatest claim to fame, but it is what I did.

First Thoughts About Mars

ZIERLER: [laughs]

EILER: Halfway through my postdoc, a paper is published that purports to have discovered evidence of life on Mars. The paper contains some things that are good. In net, it's nonsense. It's just like blathering about, "This thing makes me feel like life—"

ZIERLER: Was the methane question already resolved?

EILER: No, no, no, this was long before the methane thing. This is the Allan Hills meteorite. At this era in the remote sensing observation of Mars, basically telescope observations of Mars—I don't know that we had an orbiter around it full-time at that point—people were working on different things. Anybody who talked about life was sort of talking out of their hat. There was a crazy abstract I found in that era where somebody said little spots on the North Pole were photosynthetic plants or something. There was all kinds of nonsense. You could get that published back then. No, this paper made an enormous splash. It was based on the study of a meteorite recovered from Antarctica called the Allan Hills meteorite. In fact, here's a piece of it right here. It is among the most famous objects to fall on the Earth, and you can—

ZIERLER: Whoa.

EILER: That doesn't look like anything, but let me open it up. You can look at it. Don't spill it. [laughs] That is a four-billion-year-old rock from the crust of Mars, and it contains in it little carbonate minerals that are very distinctive in their texture. They were studied by a consortium of scientists who said, in short, "We have no proof of life on Mars, but there are four things we're going to tell you, none of which tell you that life was on Mars, but they all make us feel like there was life on Mars! And if there's four of them, how could it be wrong?" [laughs] Then they gave you four things that were all kind of stupid. Individually, they were all—like, "Oh, there's polycyclic aromatic hydrocarbons on them." Aaaaand everything else in the universe.

ZIERLER: [laughs]

EILER: Every object, every substance literally in the universe, has polycyclic—like they are the chemistry of the universe, making these things. Soot, everything, has these things on them. They mean nothing. Then the other three were just as bad. This paper gets published. It makes an absolute furor. Everybody is going crazy about this. I had an angle. I said, "Hey, you know what? Some people think that these carbonate minerals form by growth from water." Aqueous minerals. This comes back to the discipline I learned about in graduate school of the interaction of crustal rocks with waters. They are the precipitates from waters. They will tell us about the climate state of Mars in this early part of its histories by telling us about the hydrosphere that was there. Other people thought, no, no, they're melt. They were created by impact melting. They're basically igneous material. There were all kinds of ideas about them. And, I know how to study them. I will take the sample and go to Edinburgh, Scotland, which I had spent a summer at, as a graduate student, learning how to do ion microprobe measurements of stable isotopes. This was a thing that I think I told you in an earlier discussion, that Valley was pioneering and I got to be part of as a grad student. I thought, that's perfect for this. That tool will help us unpack how these things form. So I go there to Edinburgh. Valley is there and has access to a sample, and we do a paper on it. It's a pretty big paper. It still gets a lot of citations. Then I wrote some follow-up papers as well. This was my way of taking the skillset I had in petrology and stable isotopes and instruments, and reaching into planetary sciences in a very topical way, basically responding in the moment to things that people are excited about.

ZIERLER: This planted a seed, obviously.

EILER: Yeah, this obviously planted a seed. Although I move around in subject matter that I study quite often. Every five years or so, I'll switch subdisciplines that I'm working in, mostly, and retain just a presence in things that I used to do. At that stage in my career, I was basically just doing it by feel, and just like, "Oh, that seems exciting. I'll try that. That seems exciting. I'll try that." Now it's much more strategic because I have this longer timescale goal that I'm trying to realize, and I'll figure out, oh, that problem—or even more, that community—that's the right place for me to cultivate this next stage. In one stage of this process that has marked the middle of my career, paleoclimate studies were clearly the place where I could develop an interest group. Then the organic chemistry of like gases like methane, that was clearly the appropriate place for the next stage. Then prebiotic chemistry—the origin of small, soluble, molecules—that was obviously the place to go for the next stage. And now, what's the next-next stage—knock on wood, maybe the last one or so? That is refractory organic matter, complex organic matter, which is the next thing I'm starting to work on.

ZIERLER: We'll get there eventually.

EILER: We'll get there eventually, yes.

ZIERLER: 1997, the first rover to Mars.

EILER: Yep!

ZIERLER: Do you recognize in real time, sequentially, what this means, that this ultimately is going to lead to a sample return mission?

EILER: Yes and no. Everybody was talking about sample return, and laughing at it, because we knew—

ZIERLER: The engineering is insane?

EILER: The engineering is insane. Parts of it that you would think, "Okay, if you can land an object you can take off again"—Mars is exactly the wrong size. It's like too big to land on and take off of, and it's too small to land on and take off of.

ZIERLER: [laughs]

EILER: It's like exactly the wrong size for both operations. The idea of, "Oh yeah, but human history is a march forward and technical progress"—okay, the things we've done, we figured out how to do, but what about all the things we wish we had done? Like where's my flying car, and why can't I teleport like in Star Trek? There's a lot of things that don't work out. The sense in 1997 was, "I hope it doesn't crash, but it probably will. And who knows what happens next." I don't feel like I was confident that a good-faith effort at sample return was going to happen until after Perseverance landed. I honestly would have said—

ZIERLER: Oh wow.

EILER: Yeah. I think, okay, Perseverance is obviously a good-faith attempt to start sample return. Before that, it could easily have gotten diverted. Really before Perseverance, Mars Sample Return was just....

ZIERLER: It's mostly technology demonstration up to that point?

EILER: Yeah—I mean, Curiosity was—it's always a mix of technology demonstration and science. Curiosity was fairly science-heavy. But the notion that we were really going to do this thing and bring samples back from Mars, I didn't really believe it until Perseverance was on the ground and its drills had succeeded in getting specimens. Then I thought, we kind of can't—like, once they exist, once there's a tube and it's lying on the ground, and it's waiting, we're not going to walk away. We'll go get it.

ZIERLER: This will set the stage for next time—it's a small detail on your CV, but in 1997 you are promoted from Research Fellow to Senior Research Fellow.

EILER: Yeah.

ZIERLER: Is this the beginning of, "Maybe I'm going to be a Caltech faculty member"?

EILER: [laughs] No! I wish! No.

ZIERLER: No one's talking to you like that?

EILER: No. That is basically Institute rules. You're not allowed to be a postdoc for more than two years or so, three years at a stretch, so that was not so much a promotion as an acknowledgement that I didn't have a job yet. [laughs] That's what that was!

ZIERLER: And a willingness to keep you around until you do?

EILER: And a willingness to keep me around—well, I mean, this is a two-edged sword. I had two children. My wife did not work at that time.

ZIERLER: This is not easy. It's hard to support yourself.

EILER: No, this was hard. I was applying for everything and stressed that I wasn't getting it. The idea that I persisted through as a postdoc here, or like a super-postdoc—if I had known what the outcome would have been, I would have been like, "This is the greatest thing in the world. These are the best four years of my life. This is incredible." I mean, what better thing for a young person than just to hang out, do science, write papers, and travel the world? Incredible. But I did it with an axe hanging over my head and not knowing what the outcome would be. Those next two years were great for me in terms of my scientific development. By the time I was hired in 1998, I had published a lot of papers for a postdoc, especially in my field, so it really set me on a great trajectory, but it was very anxiety-producing.

ZIERLER: Here's another imbalance. Why were you having so much trouble on the job market?

EILER: Maybe I was a jerk? I don't know. [laughs] I sort of had strong opinions, and I don't have a strong filter. I just sort of tell people whatever. It was obvious when I visited institutions where I didn't belong they got that I didn't belong there.

ZIERLER: [laughs]

EILER: Like, what sort of scientist should I be? If I show up and I've got 20 papers and they're all using ion probes and crazy lasers and data-rich things—"We don't do that. There's no labs like this here. Why would this person be here? They don't belong here." They were right in the end, but that isn't how it felt at the time.

ZIERLER: Did you really only belong at Caltech? Is that sort of the inevitability?

EILER: In a way, I kind of feel that way, that I only—hindsight is 20/20.

ZIERLER: But that's about you; it can't be about the program. Because if it was about the program, then it wouldn't launch successful careers elsewhere.

EILER: Yeah. I felt like I belonged here from the beginning. In fact [laughs], probably one of the funniest things that ever happened to me as a postdoc—this was probably within the first six months I was here—is Ed calls me into his office—I talked to him basically every day—and we're talking about this and that about the latest paper, and then he asks me, "What kind of job do you want, John?" And without even thinking, I lean onto his desk, I said, "I want your job." [laughs] He was so shocked!

ZIERLER: "And you need to become provost for me to get it"!

EILER: Believe me, I do not want to be provost.

ZIERLER: No, I'm saying you had to tell him to be provost so that you could have his job. [laughs]

EILER: [laughs] Yes, something like that. First of all, it was a ridiculous thing to say.

ZIERLER: [laughs]

EILER: But I love it, because he was so shocked. Like I could tell I had genuinely shocked him, just in the way that I had said that. I always felt that way. I was like, okay, these people don't want me; they're wrong. I'm really good at this. They should want me.

ZIERLER: Last question for today. This is clearly for Ed but I want to hear your perspective on it. This is no charity organization. They're not giving you a job because you're not succeeding elsewhere. Why did Ed allow you, both the risk of losing you, and allow you to have that axe over your head for as long as he did? Why not make the offer earlier?

EILER: First of all, it's not trivial to just pick somebody and hire them, because there's a lot of other people around. They tried to hire some senior people who would have effectively ended up in my position. Ed denies that that would have cost me my job if they had succeeded in hiring some senior people. I think it would have cost me my job. I think that they would have filled that role in their ecology and there would not have been a space for me. There were other things going on that made it difficult to hire me. They were replacing the old guard. That's a difficult time because people don't like being replaced and they can kick on the way out. He probably saw correctly that my handwringing over my eventual fate was overwrought. Like, okay, this is going to work out somehow in the end, so he's not hurting me by having me be here. And, I was gradually getting better. I was just becoming a better scientist every year, so why not let that process continue?

ZIERLER: Would it have occurred to you—let's say you got the offer at Berkeley or MIT or whatever—to leverage that back to Caltech and say, "I'm leaving unless you match"?

EILER: I wish I was more manipulative than I am in that regard. I've never negotiated with somebody over salary. I've never tried to leverage outside offers. I'm now successful enough that I get outside offers from places. I don't even bring them up. It's not interesting. I'm not going. Why would I go? It's a demotion! It's not even worth talking about. I felt that way. It never occurred to me that I would try to twist their arm. In fact, eventually, in quick succession I got three offers at other places, and then was hired here. I remember distinctly the conversations I had with Ed around that time. I told him, "I'm going to have to take one of these jobs. I don't want to, and I really don't want to, but I have a family. I have to feed these people. I can't just go on being a postdoc here forever." He also had constraints, because he can say, "Oh, I give you my word that you'll be hired"—unless somebody doesn't like you in the faculty meeting. Unless the Board of Trustees doesn't meet for the next quarter. Unless, unless, unless. So even if you are the most powerful person on the campus or whatever, that doesn't mean you can just [snap] make something happen like this. The generation before you could, but you couldn't at that time. So it was just a tough situation. It never occurred to me to frame it as, "I will go get an offer and then make you do this." That didn't really enter my head.

ZIERLER: But the three offers you got and then the timing from Caltech, they clearly are related?

EILER: Oh, no, they hired me because I was going to leave. Would they have hired me eventually without an offer? I don't even know. If I had gamed that more aggressively, maybe I could have shortened the timeframe by a year, but to what end? I don't know why that would have been a good outcome. It wouldn't have helped me to be starting a lab a year earlier. That's for sure.

A Moldy Beginning

ZIERLER: You were all set to go, just by staying where you were?

EILER: For sure. My first year as an assistant professor, it was sort of farcical how ludicrous my initial office and lab setup was, but I'm very proud of it, because at the time, I just felt like, "Great. I don't care where you put me. Any room, I'm going to make it work. No instrument? Fine. I'm going to go get an instrument." That's exactly what I did. They put me [laughs]—we're running out of time, but my very first—they hired me and said, "Okay, you're hired." "Great. Where's my office?" "There's no office. We have to make an office." "Where's my lab?" "Eh, there's no lab. We'll figure out a lab. But we have this room at the end of the hallway. It used to be Geoff Blake's lab. But we've been loaning it to the Biology Department as a greenhouse."

ZIERLER: [laughs]

EILER: The room is completely infested with mold. It's just solid mold. And when they vacated it, what was sitting in the room the day I occupied it was a pile of garbage—

ZIERLER: [laughs]

EILER: —maybe eight feet in diameter and four feet tall, in the middle of the room, a bunch of mold infestation, and a little metal school desk like your second-grade teacher would have had in 1975 sitting in one corner. That's my start. That's where I'm starting. I was like, "You know what? Fuck all y'all. I'm gonna make this work." I did! I did not want to wait to buy a mass spectrometer or get my startup money or whatever. I found out somehow that the Chevron laboratories in La Habra had shut down and they had a mass spectrometer sitting under a tarp that had been vented to air 15 years before. It was one of the oldest mass spectrometers ever built of this general type, and they needed to throw it away. I was like, "I'll be there tomorrow." I rented a U-Haul. I found a guy who had been fired by the mass spectrometry company but knew how to move stuff. He and I drove a U-Haul over, we threw this thing in the back of the truck with our own hands, drove it here, set it up in that room, and I was making data that led to probably my best paper on oxygen isotopes in igneous things within a couple months.

ZIERLER: Whoa.

EILER: Yeah! [laughs]

ZIERLER: Whoa. Welcome to the Caltech faculty.

EILER: Yeah, welcome to the Caltech faculty.

ZIERLER: Oh my God. All right.

EILER: Get it done!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Halloween, Tuesday, October 31, 2023. It is great to be back with Professor John Eiler. John, as always, great to be with you. Thank you for having me again.

EILER: Boo!

ZIERLER: [laughs]

EILER: I gotcha! I gotcha!

ZIERLER: [laughs]

EILER: My pleasure, and you'll have to catch me up. What are we on now?

ZIERLER: We're going to pick up right as you finished this hilarious story of how you actually started as a faculty member at Caltech. The lore is—and it's a well-deserved lore—that Caltech really supports its junior faculty, that the idea is we want to hire the best, we want to partner with them to achieve tenure. This is not like the culture at Harvard and Stanford from 30 years ago where there's three assistant professors for one tenured slot. That's not how we do it at Caltech. Yet the story [laughs] as you've narrated it was like clearly Caltech had no investment in you whatsoever. Now the caveat here might be, you're a postdoc, you're close with Ed Stolper already, you're a known quantity. I wonder if the takeaway here is you didn't need the hand-holding that perhaps a quote-unquote "outsider," a new addition to the faculty might need.

EILER: I felt that I had a quintessential Caltech experience despite the silliness of the first year or whatever and the lab, and that it went down the way it did not because Caltech wasn't invested in me but because we're a little place, and humans are not good at doing organizational things. Everything is a little shambolic all the time. When you peek under the certain what's going on, everything is a little disorganized, and it's easy to stumble up against that, especially if you're pushing. I wanted to get moving not tomorrow; I wanted to get moving today. I wanted to be not sitting in my office watching the paint dry while I order machines. I wanted to be in the lab, setting things up, making measurements. I wanted to do it yesterday. Given that pressure on my part, what could they do? It takes two years or something to build a lab and order machines and all that stuff, and I didn't want to wait for two years. I wanted to be working. So I think it made perfect sense.

I'll bet you if you turn the clock back, get in your little time machine, go back to the 1950s, and ask yourself, what was Sam Epstein's first day in the lab like?—I'll bet it was a mess. He was in the basement of a building that had absolutely no prior history of laboratory science. It was filled with field geologists and paleontologists and things like that who just sat in their offices and read books and went out in the field in their boots and stuff. They didn't do lab work. He was the first generation of people doing lab work. I'll bet that was pretty rough when they started. So I never really resented it. I thought it was silly, but I didn't resent it at all.

ZIERLER: Now that you're on the senior side of the faculty, have you ever seen a new faculty member—

EILER: No. [laughs]

ZIERLER: —get the same treatment you did?

EILER: No, I have not.

ZIERLER: [laughs]

EILER: But also, the whole model, on both sides of the equation—both the people who are hired and the people hiring them—there's a formality to how it is all supposed to unfold. You're supposed to visit six months before you're—you've been offered a job, you come and visit, you tour the lab spaces that are available, negotiations begin about which room will be yours. You're writing grants for money. You're negotiating with the people in Physical Plant who are going to make your lab beautiful. I didn't do any of that stuff. I was here. I wanted to put a mass spectrometer on the ground and turn it on immediately, and whatever was going to happen after that to make a beautiful lab, that would happen later.

ZIERLER: It's almost like when you have a guest over to your house, you clean up beforehand, but for you, joining the faculty—

EILER: I was a drop-in.

ZIERLER: You were a drop-in. You were family, basically.

EILER: Exactly, I was family. I was basically the weird cousin living in the basement on the couch who somehow got promoted to owning one of the rooms, or something like that.

ZIERLER: Also clearly there was no concern that not rolling out the red carpet for you would result in an unsuccessful professorship.

EILER: Yeah. Over time, it became a more conscious approach on my part, but from the beginning, I always felt like, it's never going to be to my advantage in the long run to make trouble over things that other people can't really fix. So like I never argue with anybody about my salary, and I never have. I suppose if I pushed, if I threw a tantrum or whatever—or moving to a different office, or getting a bigger lab space or whatever—I just never argue with people about anything like that, because the person you're arguing with, if you ever do this, they're not really in control. It's not like they're your boss, exactly. The chairman is not your boss. There are limits to what they can give people. They will give things to people who complain a lot, but at a cost. You damage the relationship. You damage the environment. It doesn't help in the long run.

ZIERLER: Do you think this is like a Midwest bootstrap kind of approach?

EILER: It may be. It's some mixture of just taking care of your own business, in the way you suggest, but also—early on, that was probably all there was to it, but at this stage of my life, it's a very conscious thing, that I am not going to pick fights with people about things that, first of all, don't really matter. In the end, it didn't matter how beautiful—even if there wasn't a pile of garbage in my lab, it would have worked in exactly the same way. It's just a room with a roof and plugs. It doesn't matter. What am I actually accomplishing by throwing a fit about something like that? Then if I don't throw a fit and I'm easy to get along with and I produce things without being trouble, guess what? Later in life, people are happy to just hand you stuff!

The real story of Caltech, I would say, is not that you bring in the young person and you cultivate them and cultivate them and cultivate them until they bloom, and ta-da, they've bloomed. To me the real story is that you get to keep reinventing yourself. You get to keep alive the sense that—it's like the good part of being an assistant professor never ends. You get to constantly become somebody new if you wish to. Not everybody wishes to. Many people have perfectly good reasons to just stay focused on what they're doing. But if you have a good reason to evolve, the Institute is always there for you. That, I would say, is absolutely true, and has made a huge difference to me. It's basically the attitude on day one is the same as the attitude when you're 55. So long as you have a reason, if you need something, say it. If you don't need something, now you're just being a complainer.

ZIERLER: The imagery is just too delicious to gloss over, so this moldy lab that you inherited, are you in there with like the yellow dishwashing gloves and Clorox? Are you really taking care of this yourself?

EILER: Sort of. Basically as soon as I was offered a position, I drove over to USC to talk to Nami Kitchen, who is my lab manager. I had known her since both of us were in graduate school. She was in the same group as me at Wisconsin, maybe a year or two behind, and I knew that she really had the golden touch at doing things in the lab. She was employed down at USC.

ZIERLER: What does that mean, the golden touch?

EILER: There are people in this world who are ham-fisted in a lab. It doesn't matter how good they are at tennis, or how clever they think they are or whatever; you put them in a room full of glass, and things just break. Or you put them in front of a machine and they're going to touch the wrong button or whatever. They just don't understand how to make things work. She is the absolute inverse of that. Any problem you can pose, whether she's down machining things in the machine shop, or messing around with electronics, or playing around with chemistry, or teaching somebody how to do something—problems just get solved. You don't have to argue about it, you don't have to talk about it; they just get solved.

ZIERLER: This is a skillset you hang onto for dear life.

EILER: Absolutely. I knew that this was what she was like. I knew she didn't really care about being a professor or anything like that. She was working as a lab manager down at USC in the lab of Jean Morrison who at that time was a professor. She went on to be one of their senior deans. She then went on to be some kind of senior administrator at Boston College. Really great person. She had been a senior grad student—Jean Morrison, that is—in the same group I was trained in. Real strong personality, great person. My first move was [laughs], "I am going to snake her lab manager out from under her immediately!" So, I went down there and hired Nami Kitchen. So she and I are in that room trying to figure out what we're going to do, and yeah, day one is put on the rubber gloves and just start cleaning crap out.

Day two is the butcher block paper. This is an old trick that I don't know whether—I don't know where I first saw it done. Maybe at a University of Wisconsin lab, or maybe we just made it up? But every instrument that we've installed in my lab—and now there have been, I don't know, over a dozen major instruments put in, and beginning with this first one—step one, go get a big roll of butcher paper and roll out a footprint of everything you want in the lab, and then just play Legos. Move it around, play house with it, move stuff everywhere, put it where you want it. Instead of doing this on a computer screen or something, we laid out what we wanted the lab to look like with big pieces of waxy, brown paper and taped them down, and then just start. My second grade teacher metal desk, that goes over on this piece of paper. That was how we laid out the first equipment in the lab. It included two ridiculous things and one really good thing. The first ridiculous thing was this mass spectrometer that I got from the Chevron labs in La Habra.

Jumping Into Mass Spectrometry

ZIERLER: What is Chevron doing with mass spectrometry?

EILER: Once upon a time, all of the major petroleum companies, along with a lot of other materials and technology companies that are familiar to us, like Dow and Corning and places like this, they all ran basic science labs. It was considered a standard part of being a serious company, that you would do R&D. Now, not very many old-school companies, whether they are in the oil industry or not, really do that anymore. Exxon Mobil does it. Most of these companies don't really do that.

ZIERLER: Now we see that in tech, for example.

EILER: Yes, you see that in tech. A lot of the old-school sort of materials research, chemistry research, things like that, they either just don't do it all, or they farm it out to academics or consultants or something like that. Chevron ran an isotope geochemistry lab, and they were actually the breeding ground for the biggest, most impactful innovation in stable isotope studies, studies of the isotopes of light elements like carbon and things, prior to maybe the year 2000. They were the place where a fellow named John Hayes, who was a very famous scientist—he trained Alex Sessions, who is one of our professors—John Hayes was a young scientist working there and developed methods for isolating individual organic molecules out of complex mixtures, and then in the same experiment as their isolation, immediately burning them and then putting them in a mass spectrometer. That's a very impactful invention. Biochemistry, environmental chemistry, petroleum geochemistry, all these different fields used this, and he invented it there.

Their lab then slowly fell apart as it became less and less profitable to run your own research groups. It all got mothballed, and their highest performance mass spectrometer, the one I took, had been sitting under a tarp for over 10 years, maybe 20 years, vented to atmosphere. Just a dead hulk. We hauled it back here and me and Nami Kitchen got the thing plunked down and ready to run. Then there was another old guy named Vic Nenow, who was the GPS Division's electronics expert. This was the kind of position that doesn't exist anymore. We have IT people; this is totally different. Vic Nenow would wander in with glasses on top of his head and a soldering iron and a toothpick or something and he would just MacGyver anything. Anything that broke, first you pull the boards out, you start touching stuff and fixing things and soldering things. Back then, even in 1998, 1999, the first year or so of my assistant professorship, the equipment we had, you could interact with it in this way. Today, even the people who design these machines, mass spectrometers, they can't fix their electronics. If something breaks, you just pull out a board and throw it away and you put in another board. They're all made by automated systems who knows where, and nobody knows how to repair them, diagnose them, anything like that. Vic Nenow helped us revive the electronics in this thing, and then me and Nami Kitchen got the hardware working. That was one piece.

Then another thing was a glass vacuum line. All of our laboratories, to this day and going back to the origins of stable isotope chemistry, you always have to have vacuum apparatus so that you can prepare and work with gases. It's because our mass spectrometers all required gases as analytes. The whole game was turning things into gases, purifying gases, and so forth. So, we built one of those. One of my first plans was to prove to the world that I'm alive, I'm going to write a paper as soon as I can, about anything. I knew that the Mars program was spinning back up into a high level of activity.

ZIERLER: Sojourner was 1997.

EILER: Yeah, Sojourner was there, and the Life on Mars papers. The 1996 Life On Mars papers, which I don't know if you know about those?

ZIERLER: This is where they figured out that there's no methane, and this was very disappointing for everybody?

EILER: This is long before that. The 1996 paper was by McKay et al. This has now been completely forgotten by almost everybody, but if you're over, say, 45, you remember it as being one of the biggest moments in Earth and planetary sciences in terms of public awareness of a Science paper, broad discussion of a single paper, arguments back and forth, conferences and so forth. It was a paper published in Science that said a meteorite from Mars contains evidence of life in its mineral deposits. It was all hooey, it was a bunch of nonsense, but it felt compelling at the time, or compelling enough that you had to respond to it. NASA made a big deal about it. So, everybody is thinking about Mars, and I thought, I'm going to think of one thing that nobody has done that has to do with stable isotope chemistry on Mars and is obvious and I can do standing on my head with a vacuum line, and I'll do it and publish it. That was to measure the isotopic changes in CO2 when you freeze it and re-liberate it to the atmosphere. That's what happens on Mars. That's Mars's meteorological cycle, CO2 atmosphere that freezes on the poles and then re-liberates into the atmosphere. I thought, I'll figure out what the isotope chemistry of that is. I built a very simple apparatus to do that, and then we built a laser line that allowed us to study isotopes of oxygen in minerals. That was the thing I had done as a postdoc at John Valley's lab. Those were the things that we put in that moldy room. The laser was the good part. The laser was nicely built and worked very, very well.

ZIERLER: Last time we ended, you mentioned parenthetically that you had done some of your best work with this.

EILER: Yep.

ZIERLER: You mentioned now two projects. Are you referring to both of them as some of your best work, or are you emphasizing one?

EILER: No, the best work was the stuff done with the lasers. We studied very subtle variations in the isotopic composition of oxygen in major classes of volcanic rock at the Earth's surface. The mid-ocean ridges, where 90 percent of the Earth's volcanism happens, and the ocean plates are formed, and oceanic islands, places where volcanoes punch through the oceanic plates from so-called plumes or upwellings in the mantle, and then volcanic arcs, where the oceanic plates subduct back into the mantle, these are the three major environments where volcanic rocks get generated on the Earth, and they sample different domains of the mantle that are themselves subject to different amounts of stirring-in of subducted material. You're seeing different windows on the chemical evolution of the Earth's mantle. The ridges show you the mantle very well mixed, almost homogeneous.

The question there is, can I see actually evidence at all of chemical heterogeneities that are introduced through subduction? Anything you see will be very subtle, but if you can find them, they will be very meaningful, because you're looking at 90 percent of the volcanism. If you go to the subduction zones, volcanic arcs like Japan or the Andes, there it's the opposite extreme. You're immediately next to places where the ocean plates are subducting and shoving chemically exotic things into the mantle. Can you trace them into specific kinds of volcanic lavas and see their effects where they are abundant? Then the ocean island basalts, where there are these plume upwellings that punch through, there you are seeing a kind of mysterious form of volcanism. It samples a part of the plate tectonic stirring of the mantle that is counterintuitive and a little peculiar. Actually it's not clear that it has any direct connection to plate tectonic sorts of motions. There, you're wondering, are there parts of the mantle that are quite exotic? They are nothing like the top of the mantle that is producing most of the magmas that we see. Are there deep parts of the mantle that have maintained a sort of exotic chemical identity? That was the focus of my oxygen isotope studies in those first few years as an assistant professor. The papers that we did on the mid-ocean ridges and the volcanic arcs, I would say they were the best things that I did in that subject area.

ZIERLER: Your work on Mars or recreating conditions on Mars, did that add to the debate about whether there was life on Mars or not?

EILER: Yeah, I'd say—there were several responses to the Life on Mars papers. One line of argument focused on the environmental conditions in which the carbonate minerals—in the specimen, the Allan Hills meteorite, the carbonate minerals in it are a secondary mineral. They form by weathering processes, basically. Some people looked at those minerals and said, "I think they are created by shock melting"—by impact of asteroids striking the Martian crust and heating it and melting it, and there's some sort of exotic mineralization from that process. Other people looked at them and thought that they were maybe some kind of igneous material or hydrothermal material related to magmatism. Other people looked at them and thought, oh, no, they are a consequence of the same process that makes chemical precipitation of carbonate at the Earth's surface, like caliches and little carbonate crusts and things, through weathering, and near-surface chemical processes, and that they are basically a product of the water on Mars and its shallow crust, interacting with the rocks.

These three points of view, the last of them would be consistent with the preservation of remains of life, although obviously it doesn't require it, but it would be consistent with it. The other two would make it very implausible that there would be evidence of life preserved there. Figuring out the conditions at which a mineral formed, that's one of the things that stable isotope geochemistry is good at. That was something I worked on starting as a postdoc. The best paper I did on that particular subject was something authored by Itay Halevy who was a postdoc here and is now a professor at Weizmann. He applied the carbonate clumped-isotope method which is something invented in my lab that lets you measure the temperature of growth of a carbonate mineral without knowing a lot of contextual information.

Carbonates and Context

ZIERLER: What does that mean here, contextual information?

EILER: The founding idea in stable isotope geochemistry, the application that made the whole field just sort of click into shape, was proposed by Harold Urey, who was this professor at University of Chicago, Nobel Prize winner. He's a person I mentioned before. He was Sam Epstein's supervisor. He had the idea that chemical separation of isotopes happens in nature and is a response to the changes in thermodynamic properties of substances when you put heavy rare isotopes into chemical bonds. It helps to understand physically what is going on in this tool. He proposed a tool that looked at the way that the vibrational frequencies in chemical bonds slows when you take out a normal light isotope and put in a rare isotope like oxgen-18 in place of oxygen-16. When you do this in water, you will lower the frequency of motion of all the modes of motion in water. The hydrogen-oxygen stretch, even the hydrogen bending modes will change a little bit. You'll slow those frequencies of motion.

Planck's postulate from 1900 tells us when you slow a frequency you lower an energy. Frequency and energy are equivalent through Planck's constant. If I slow frequencies of motion, I lower the vibrational energies of substances, and they become more stable. So every chemical bond in nature wants the heavy isotopes. But for the light common elements like oxygen and carbon and hydrogen and nitrogen and sulfur and all these common elements, the heavy isotopes are rare, and so chemical bonds have to compete for them. A chemical bond that has its vibrational energy lowered by a lot will win the competition and steal heavy isotopes from other things that have less of such an effect. In water the effect is small. In the carbonate iron, CO3, which is like the main building block of calcite and other Caltech minerals, the effect is big. So the carbonate ion is stealing oxygen-18 from sea water when you grow carbonate minerals, and that effect is modulated by temperature. When temperature is low, you notice this effect a lot. When it is high, entropy starts to take over and randomness becomes the rule, and the isotopes are freely shared.

Urey realized how the thermodynamics of this effect worked, and he said, "I can go back in time by picking up a rock from the geological record and measuring its oxygen-18 content, and if I assume something about the O-18 content—oxygen 18 content—of the ocean in the past, I can interpret that as a temperature. If the Earth was cold, the carbonate will be very rich in O-18. If the Earth was hot, it will be poorer in O-18. Now I can just go back through old sequences of carbonate minerals and reconstruct the climate of the Earth through Earth history." Incredible idea, everybody understands it immediately, and this is the birth of the entire discipline of studying the chemistry of isotopes. The only problem is you don't know how much O-18 was in the ocean in the past. You really, really don't. Urey's thought was basically, "Wow, the ocean is really big. I bet it can't change in its O-18 content." That's sort of like the people around the time Arrhenius was first pointing out that CO2 in the atmosphere would heat the Earth. Many people's response was like, "Yeah, but the Earth's atmosphere is big. You're never going to raise CO2 in the Earth's atmosphere. It would take forever." They were wrong. Urey was wrong. The O-18 content of the ocean can change through time. It changes through the ice ages, when you take ice out of the water and store it on land, put it back in. It changes over longer timescales, through interaction with the crust through weathering. So his tool fundamentally could only work if you had the right context; you knew the O-18 content of the ocean. Only then are you studying climate.

Probably the most important thing I did right near the end of my assistant professorship, early after I was tenured, was the creation of a tool that gets past this need for context and lets you study temperatures of formation of materials when you don't really know much of anything about what they grew from or what other materials were around them. That is based upon a very rare thing. This is something Urey talked about but he thought would be impossible to ever measure. The effects were too subtle. The species involved were too rare. And that is, molecules that have more than one rare isotope in them. The basic idea behind this tool is if you have a heavy thing vibrating on a spring against another heavy thing, this has a reduction in the frequency of motion that is significantly greater than if I took each of those heavy things and split them off into two different molecules and had them vibrate against a light thing. That basically heavy with heavy, that's best of all, and it's better than two heavy with light. It results from the fact that the frequency of motion, it doesn't scale with the mass of the object that you're looking at moving, the atom; it scales with the reduced mass of the whole motion, which depends on every component part's mass. It's sort of like the orbit of the Moon around the Earth; its dynamics is not independent of the mass of the Earth. It matters how heavy the Earth is. It doesn't matter that much. It matters a little bit, not a whole lot. If you made the Earth one percent heavier, it wouldn't really matter much. But it matters some. It matters in some observable, calculable amount.

This effect of heavy against heavy being a preferred state, that means that the heavy isotopes not only seek out molecules where they do the best good energetically; they also seek out each other. They try to stick to each other. This effect is also temperature-dependent. When it gets hot, entropy wins and they don't care so much anymore. They just wander freely through structures. But when it's cold they really stick to each other. That temperature dependence—first of all, the molecules are very rare. I told you oxygen-18 is rare. Rare times rare is really rare. So all the things you wish to measure, they are much rarer than all the isotopic species we are used to measuring. The effect that you want to study is about a hundred times smaller, weaker, than the effect of separation of the isotopes between molecules. It's really a third-order thing happening in a third- or fourth-order abundant species.

Urey looked at it and he said, "Yeah, this is a thing. It's not a thing for geochemistry. You're never going to measure it." My contribution was to say, "Says who? Of course you can measure it. They exist, so you can measure them." To figure out ways to measure them, and then apply them to this classical problem: what is the temperature formation of objects in the distant past of the Earth? The same logic applies to Mars. If I wanted to use Urey's tool to solve the problem of how the Mars meteorite minerals got carbonates in them, I would fail because I don't know the O-18 content of the ancient Mars oceans if they existed, or any of the waters. With my tool, you don't care. All you care about is that you have a sample, it has a state of organization of its isotopes, you observe that, and boom, you know the temperature.

ZIERLER: Does that lead to building out the context that you don't know? Does it work both ways?

EILER: Yes, it works both ways. Once you know the temperature of formation, now you can read the O-18 content of the mineral as a statement about the O-18 content of the water, and you're doing it rigorously. You have a calculable answer to what the O-18 content was.

ZIERLER: I want to go back to the ancient mass spectrometer that you got from Chevron. The image in my mind is, brand-new assistant professor. The division chair—I've heard stories about Dave Stevenson saying, "Name your number," and then the assistant professor is like, "What? I don't know. What is my number? How high can I go?" and things like that. What's the takeaway or the lesson that you revived this ancient machine with messed-up electronics and did really good science with it? What's the lesson to be learned here?

EILER: There's no amount of money that you can spend that is a substitution for knowing what you are doing and having a goal. Of course you can't just lock a person in an empty room and have them succeed, but you can put a person in a moldy room and just give them a little something, and that should be enough. There's limits to that thought, but yeah. I understand your question. It's a hard question to answer, because money does things. Money opens doors. Money enables things. But really money is a two-edged sword in a way, in that it is a shortcut to accomplishments, but it is also a time suck in itself. My early first year or two experience was a good example of this. If you had handed me a brand-new mass spectrometer the day I was hired, I probably would have been better, somehow better. I would have made even better measurements. I would have not wasted time fixing an old machine.

ZIERLER: Okay, so you are establishing some level of causation here.

EILER: Yeah. So that would have been better. If you had handed me the money for a mass spectrometer, I would have done worse, because then I would have sat there staring at my pile of money for two years while I place orders, and there's bids and other nonsense, and they build something, and they ship it, and then some engineer comes, and blah-blah-blah. All of that is the clock ticking, and when you're an assistant professor, the clock is your enemy. You need to have impact on a schedule. I was very sensitive to the fact that I didn't really need money; I needed measurements, and if I had to fly somewhere to make them, I would do that. If I needed to go get some crazy, old machine and fix it up, I would do that. I needed to beat the clock, not the bank.

ZIERLER: The common conception that the arms race of discovery in science rests entirely on cutting-edge instrumentation—again, the lesson here—is that not entirely true? Do you not need the latest and greatest tools in order to make the latest and greatest discoveries?

EILER: You need to do the latest and greatest experiment, and sometimes that is just through weight of metal, like a device that nobody else has, or, maybe it's a device that no one else knows how to use. Or, maybe it's a device that's totally ordinary and then you glue to it something special. That's the case—these early studies I did of igneous processes and basalts and so forth, the mass spectrometer was a piece of garbage. The laser line we attached to it was great. It was one of the best in the world at the simple job that it had of getting oxygen out of materials. Sounds like a simple part of the whole process; actually, much more important than the mass spectrometer. I understood at that time that what was needed is any functional mass spectrometer of any description attached to the best functioning laser line we could create. The laser lines were all home-cooked. You couldn't buy one. You could buy a laser, but then you had to build a vacuum line and the pumps and the chemical preparation devices and the converters and the acids. All that stuff, that is just the skill of the experimentalist. That has nothing to do with money. The devices themselves, all of it is cheap, but you put them in the wrong hands, and they do nothing. Assembling the correct front end to our mass spectrometer, that was where something special was happening. The mass spectrometer itself could be a party favor, almost. It just didn't matter what it was like.

ZIERLER: It's almost like you went to the junkyard and got a chassis and then you souped it up.

EILER: Exactly! We put a V12 engine from some classic old roadster into a VW Bug just because we needed wheels. An engine with no wheels doesn't go anywhere. Yeah, that's exactly right.

ZIERLER: I want to ask about the thought you gave to establishing a research agenda vis-à-vis your fellow faculty members in GPS. I can see it cutting both ways. On the one hand, you just want to do the best possible science with the tools and skills that you have. On the other hand, you're an assistant professor, you don't want to step on toes, it's not a very big place. The whole idea behind Caltech is we're not going to give you, like a bigger school, three or four colleagues who basically do the same as you. We expect you to define the field in the way that you define it. I wonder if you could just reflect on all of that.

EILER: It was ultimately successful, but the most difficult period of my career was not my first or second year as an assistant professor. There, I'm just moving on the momentum of my four-year postdoc. I almost in a way couldn't fail. All I had to do was keep writing the next five papers or something about things I knew how to do, and I would have a decent start. The question is, what happens for the next three years? How do I evolve myself? How do I innovate? How do I change? What do I think is going to define—? Saying that you want to define your field, even if you end up doing that in the end, you'll probably fail if you're goal is to define the field. A field is a big thing, and it's an entire ecosystem of people making decisions and discoveries being made. You have to have a dynamic interaction with your field.

ZIERLER: It's also staying close to the thing that you defined before you got there.

EILER: Yeah. So I needed to define myself. What was my style of contributing to science going to be? I did not have a clear answer to that question in year one or two or three of my assistant professorship. There was a period, maybe right about in the middle of my assistant professorship, so maybe 2000, 2001, where my tracking committee—let's just say they had notes, okay? They thought that I was dithering. I was looking around at too many ideas. None of it was gelling. It wasn't clear that I had a concept of what I wanted to be doing for the next five or ten years other than finishing off some obvious things to do from my postdoc. And they were kind of right. I was searching around. Probably the most creative and in terms of citations and things influential thing I did during that period was I got interested in the hydrogen economy and molecular hydrogen in air. Currently there's another wave of hydrogen economy talk happening, and this time maybe it will happen. Back in 2000 was a first major wave of that.

ZIERLER: What does that mean, hydrogen economy?

EILER: Meaning using hydrogen and fuel cells as a means of energy generation.

The Hydrogen Economy

ZIERLER: Oh, this is Governor Schwarzenegger and his hydrogen Hummer.

EILER: You got it! Exactly! I'm sure people were talking about it before, but the first big wave of interest in that was in about the year 2000. I knew about that, although I kind of wandered in it through the back door. I was talking to a new colleague of mine, Jared Leadbetter, who had just been hired. He studied the chemistry, the metabolisms, and the associated chemistry in the guts of termites. I don't know anything about termites. He's walking down the hallway, and I go, "Hey, Jared! What's going on with your termites?" "Oh, yeah! They're doing their thing. They're farting out hydrogen!" I'm like, "Hydrogen? That's crazy! Hydrogen? That's like a rare molecule in the atmosphere!" He's like, "You're an idiot. Hydrogen is the second most abundant reduced gas in the atmosphere. Hydrogen is everywhere." I thought, how did I not know that?

ZIERLER: [laughs]

EILER: And how is it possible? Because I had heard people in talks at national meetings, people who supposedly knew better, saying, "Oh, yeah, the hydrogen in the atmosphere, it just flies out into space." No, it doesn't. None of it does. The hydrogen in the atmosphere is very dynamically cycled, through atmospheric chemistry, biology. All kinds of things modulate it. It does not just fly out into space, and there's a lot of it. I thought, I don't believe I've ever seen somebody study the stable isotope chemistry of the hydrogen in air. It wasn't completely true. A couple of people had tried to do this but had not gotten very far. I thought that would just be fun to do. Hydrogen—molecular hydrogen, H2—was the molecule that Urey used to understand the chemical physics of isotopes. And yet it never evolved—it never had a natural isotope geochemistry.

I really didn't have a deeper thought than that—that okay, I read about it in the newspaper, Jared has his bugs that fart this stuff, Harold Urey worked on it, it just seems kind of interesting, so I'll work on that for a while. So, I did a series of papers on hydrogen. The most dramatic and publicly visible of them was a theory paper—that was written by a postdoc in Yuk Yung's group but I helped write the paper—that was about the possible consequences of leakage into the atmosphere from a hydrogen economy. This pissed off a bunch of people who were basically in the advocacy business. They were in this gray zone—there's a sort of liminal space between academic science and lobbying and advocacy for profit sort of science. There are people who live in this space very intentionally, developing expertise and some level of notoriety as an academic, but then kind of cashing in and developing more influence through political processes and lobbying and fundraising and things like that. There's a cadre of people of that sort who were very invested in the idea of a hydrogen economy at that time, and boy, did they get ticked off about this paper. So there was a lot of back and forth, and I got interviewed on KPCC and things like this, lots of comments and replies about this paper. So that was something that was very visible but also very frothy; it didn't have a lot of oomph to it. There's only a few interesting things to know about the natural geochemistry of hydrogen, and you could guess some of them, at least semi quantitatively already, without having isotopic data. So I was learning things and contributing things, but if you looked at it from the outside, you'd think, "Where is this going? What really is the impact of this in the long run? Come back in 30 years; what will you think was the contribution of this?" The answer is, not much. The papers continue to be cited. They were kind of interesting. They're not leadership. They're just a few interesting papers.

But out of that experience came the thing that was very impactful, that emerged right at the end of my assistant professorship—the study of the isotopic ordering in natural materials, the clumping effect that I was describing to you a moment ago. It arose through a very Zen, stream-of-consciousness thought process. I'm studying molecular hydrogen. Part of it is because I really appreciate my roots in Epstein and Urey's approach to science. Urey thought hydrogen was the most important—that's how he got the Nobel Prize, was working out the effect of isotopes on the chemistry of hydrogen and therefore figuring out how to enrich it and detect it. I read his old papers in the 1930s. As I read through them, I realized, everything in this paper, it's not about molecular hydrogen with one deuterium in it; he hardly cared about that at all. He is focused on the doubly deuterated hydrogen and how its dynamics, its vibrational properties, are uniquely different from the singly deuterated version of that. That was the focus of his theoretical treatment of the chemical physics of isotopes.

I looked at that and I thought, that's incredible, and because it's a property that is intrinsic to the hydrogen itself, it means it's a record of that molecule's origin, fate, environments, whatever, that doesn't require these contextual clues. It will be preserved just in itself. Why is there no geochemistry of this? Nobody in 70 years at that time had touched this analytically in a natural material. I don't think there was a single measurement or even like a theoretical paper or anything, about the natural chemistry of these things. I realized that the abundance of the most—the ion beam in my instruments that corresponds to the most abundant, the easiest to access of such species, a multiply substituted form of CO2, that ion intensity is almost exactly the same as the ion intensity of the singly deuterated hydrogen that I am studying today. If it's there, I can study it. If I'm measuring this ion beam, I can measure that ion beam. That thought, as sort of simple and basic as it is, that's what led me to do experiments. I just asked—there's no machine that is designed to measure this, it seems impossible, and yet I'm doing something exactly like that. So all I have to do is fiddle and tweak and squeeze and push on the machines I have to make them observe this weak ion beam.

Basically I had to take a beam that was supposed to go into a bunch of collectors for heavy molecules like CO2 and make it go into this other physically distant collector for hydrogen, and then do that in a way that would be reproducible, precise, accurate, and standardized, and things like that. I figured out how to do that just by basically hacking a very simple mass spectrometer in my lab, and then used those results to go raise money for a new mass spectrometer that was built to purpose that would have detectors in it of the correct sensitivity and the correct position so I could really study that molecule. Why? Who cares why? Because nobody has ever done it, and it exists in nature, and it's a special form of material, and I'm sure it will be good. That thought was really the beginning of me finding my own scientific identity.

ZIERLER: And this is four, five, six years in?

EILER: Yeah, like in my fifth year.

ZIERLER: Tenure clock is approaching.

EILER: Yes, tenure clock is ticking. They're not going to decide my tenure based on this because there's no way I'm going to write a paper in time. The first paper came out a few months after I was tenured. But my colleagues knew what I was doing. I was telling them what I was doing. I had my meteorite projects, and I had other meteorite projects. I had my igneous rock projects, and I had my molecular hydrogen projects. I probably had some other stupid stuff I was doing, like my vapor pressure of CO2 from Mars. I had a bunch of things going on. Other than the things that were carryovers from my postdoc, which I probably could have gotten—if I had just said, "I'm the guy who does isotopes of oxygen in volcanic rocks," they probably would have tenured me. There are other people who have become professors here who had similar levels of focus. It's not who I am. I don't have that kind of focus. I'm much more interested in exploring, finding new things, trying new things. That's really what motivates me in reality. And I just was not successful, up to that point, in finding something that was both exploratory and impactful. It's because I hadn't reached far enough. I hadn't actually attempted anything that was genuinely new. I had attempted things that were clever, I had attempted things that were difficult, but I hadn't really attempted anything that was genuinely, totally new. The first time I did that, I really felt like, okay, this is what I'm supposed to be doing.

ZIERLER: How did you know that? Is it intuition?

EILER: It's totally intuition. I just—the simplest thought about what the chemistry of isotopes is about, and where is all the information written in nature, in its isotopic content, you realize virtually everything that there is to be read from nature, using the chemistry of isotopes, is written in molecules that have two or more rare isotopes in them, because that's where all the diversity is, by many orders of magnitude. No one has ever seen one of them, and yet that's where almost everything is! It would be like saying, "I have a telescope, and I can see all of the planets in the solar system." That's wonderful! Knock yourself out! "But I've never seen anything outside of the solar system." Well, that's where everything is! So you have to somehow see that much further, or you'll never make progress beyond where you are today. It sounds sort of grandiose, but when you do all the order of magnitude calculations about this, it's really true. So I thought, I'll begin with this one simple—the most accessible possible version of—the most easy-to-work-with molecule that there is. Of course I'll start there. But there's no end to it. I can go forever. Every single day will be something that I get to discover, something new, a new problem, a new application, a new molecule. Everything will be new every single day that I work on this, from now until I'm done. I was right! All I had to do was just leave where everybody else was.

ZIERLER: That gets to my earlier question about the extent to which you were sensitive to stepping on the toes of your colleagues. It sounds like you weren't.

EILER: I never cared about that, at all. At all.

ZIERLER: Is that because the world is big enough where the redundancies are just too rare of a phenomenon to give much heed to?

EILER: My interaction with the idea of like precedents and not stepping on toes and things, partly it's just that's not a productive way to think as a scientist. It's maybe helpful in the short term. If you're in a densely packed field—like imagine that my passion was understanding climate change or something like that. I care about climate change but that's not my scientific passion and it's not where my big contribution is. If it were, I would have to learn how to work in a crowded field. There's no avoiding it. Then, if you want to make an impact within the next few years and work in that area, you've got to figure out how to contribute without stepping on toes. I'm sure that there's all kinds of ways to have an impact where you are independent and so forth but you will always be in a crowded room.

I just have never been that interested in doing that kind of science, being that kind of scientist. I prefer to be doing things where the motivating questions are things everybody cares about—like, was there life on Mars? What was the climate in the past?—questions that everybody cares about but the actual on-the-ground research is in an empty room, is in an empty amphitheater, is far away from anything else that is going on. Not because I want to avoid other people, but I want to see something new. I want to see something fresh, attempt something where I don't know the answer already. A lot of what we do in the lab, you don't know exactly the answer but you basically know the answer. People who are doing the normal way of, say, studying the Earth's climate in the past using isotopes of oxygen, they were doing their own thing. They continue to do it. It's still a big field, using Urey's thermometer. It's based on oxygen isotopes going between sea water and carbonate. It's productive, and it's great at solving certain kinds of problems, and—you know exactly what you're going to see tomorrow. Every single day you wake up and pack your lunch to go to work, you know what's going to happen. Maybe the number is gonna be 12 and maybe it's gonna be 12.1 and maybe it's gonna be 11.9, but you know basically what's going to happen to you that day. I just can't do it. I have to do something where the answer is like infinity symbol-something, some totally new thing. I want to translate the hieroglyphics. I don't want to sit there and rewrite Latin translations or something like that.

ZIERLER: Just as a thought experiment, you're merrily working away in your lab, and say Ken Farley is down the hall and he's merrily working away in his lab, and you're not communicating at all, for whatever reason. Is there any likelihood of convergence, that you guys are going to find yourself working on the same thing?

EILER: No.

ZIERLER: Do you care? Is it okay if you do?

EILER: Yeah, and I think the ideal structure for a group, a department, an option, at Caltech, given our culture, is a community of people who can be independent but choose to brush up against each other in a variety of ways.

ZIERLER: To mutually productive benefit.

EILER: Yes, to mutually productive benefit. You should know what your neighbor is doing. You should have dialectical conversations around the water cooler about what you did today and what they did today, and be able to understand enough about each other to ask probing questions. You should be able to co-advise students and postdocs, do little projects together. All these things are extremely important. But if they don't show up at work tomorrow, you've still got plenty to do. I think that that is certainly the case—Ken and I have lots of things to talk about, and we co-advise people quite frequently. Not quite as often as Ed and I do, but I probably have half a dozen or more colleagues who are regularly co-advising people with each other. If none of them come to work tomorrow, I will think of a way to fill my time. We don't really need each other in that way.

Collaborators and Apprentices

ZIERLER: I want to return to building up the lab. We've covered instruments, a lab manager. What about students, graduate students and postdocs? Who are the students who are going to be attracted to work with you and not another faculty member? And that's acknowledging the fluidity of the way that supervision happens in GPS.

EILER: I explain this in exactly the way that you are framing it to people who come and interview with me for student or postdoc positions. I tell them that there is two different ways that people interact with my group or my labs. One, which might even be the most common, is they have their own motivations. They have to have some overlap. If I don't think it's interesting at all, and I don't even want to think about it or talk about it, then maybe it doesn't happen. It's their motivation that I resonate with and I think is interesting, but probably they're mostly supervised by somebody else, somebody who has expertise in exactly what motivates them. Maybe it's a biologist like Dianne Newman or somebody like that. Maybe it's an igneous petrologist or something like Claire Bucholz, somebody who has a shared passion for exactly their project but they need a tool. And they don't need to just walk into a room and have a magic machine and they punch the button and the answer comes out. They need help. They need to design and execute experiments. They need to figure out how to even ask a question using those tools. They need a collaborator to help them make observations or do experiments. That's a kind of collaborative situation that I like a lot. Those people typically will drift in and out of my group for a year, two years, maybe three years, do what they need to do, and then they move on with their life. Maybe they later in life adopt some of those techniques or instruments or whatever in their own career, and maybe they just leave them behind, but it was a productive interaction. That's one way of being in my group.

The second way is, you're an apprentice. You're trying to become the kind of scientist that I am, in some way. Everybody is going to be unique, but you will develop the toolkit that I think is essential to be really good at this field. They always end up doing three things. They have to contribute to technology. You can be good at isotope geochemistry without being a technologist, but that's what I do. I create new ways of observing things. You have to create new ways of observing things in some fashion. You can't just learn what I can do now; you have to create something that I can't do now. The second thing is you have to engage with the chemical physics through theory, experimentation, study of fundamental properties of natural materials. That can't be a casual thing for you. You have to really commit to it. I felt like that commitment to the literature, of the people who originated isotope chemistry, that was so important to my career, to feel like I can just draw a line straight between the things that I want to do and the ideas that were present at the founding of this discipline. What were the questions they were asking? The most fundamental basic answers to those questions, all of that remains true, and all of it underlies the emergent behaviors of isotopes in natural materials, which is our job. So you have to really engage with that, and that means making it better. You have to be able to take this century of chemical physics theory and make it better. How do you do that? Through projects in theory and experiments and so forth. That has to be part of your project.

Then you have to have an application that you're passionate about and involves questions that natural scientists, Earth and planetary scientists care about, or life scientists, and you have to advance that and become the best person in the world at that application, at least for while you're doing it. Those three things all have to be true by the time you're done. That really sets out—the details, when you fill them in, each person is unique. Everybody comes into the group at a different point in time. My interests are different. The existing technology is different. What is possible in the near future is different. Their interests are different. The exact details are always unique, but every person who spends five years or whatever in my lab, they have to do those three things.

ZIERLER: Are you reflecting on this retroactively, or were you able to articulate this in the early years when your research was quite eclectic and not particularly deep in any one area?

EILER: No, I couldn't articulate that until I was probably eight to ten years into my career. I would say the first two or three years, I was just scrambling to deal with the fact that like now I have to keep a weekly calendar. As a postdoc, I didn't know anybody or talk to anybody, so why should I have a calendar? A day is a day. You get up and you work on stuff.

ZIERLER: [laughs]

EILER: It's just embarrassing, but I had meetings with like members of the visiting committee, chairs council people, people who were like friends of Caltech; I missed my meetings with them because I never wrote meetings down. I literally kept every single thing I was supposed to do, every deadline, in my head. I didn't write down proposal deadlines. I didn't know when my classes were. I didn't know when I had meetings with people.

ZIERLER: The important stuff, you remembered?

EILER: Some of it!

ZIERLER: [laughs]

EILER: I was knocking tile off the floor in my guest house during one of my first introductory geology lectures because I had forgotten what day it was!

ZIERLER: [laughs]

EILER: I didn't know I was supposed to be teaching! And I didn't keep a calendar! And I just forgot. Things like that are why the first year of being an assistant professor is hard. Maybe other people, it's not their calendar—now we all have calendars on our phones or whatever—but there's always something. It's a shock to become a professor. No one is teaching you how to be a professor before you are a professor. You have to figure it out in your first year or two. It's a completely different job from being a postdoc, mostly because you have all of this BS that are demands on your time. The volume of paperwork suddenly increases exponentially. The money side of it, all of the stuff is new. The first year or two is just hell, for everybody. Even if they say they love it, they don't love it. It's really hard.

But scientifically I didn't really have to think. All I had to do was just do, execute the program I already knew how to do and the problems I had been working on as a senior postdoc. Then I had this period, three or four years, of kind of wandering in the wilderness. Then I had a period of two or three years when I was really just focused on myself. Like the idea that I had this insight, my God it's happening, it actually is really new, I'm getting exposed to all these new scientific communities who are interested in what I am doing and I had no cross-section with them at all before. All kinds of new, stimulating interactions and ideas and concepts for applications. I was very focused on just my own personal growth as a scientist in those first couple years after being tenured. Really only after that started to settle down could I start to view myself as a group leader with a strategic—I wouldn't say plan, because the plan evolves, but I had a vision of where I was going and how my group would work. It really took a decade for that to take shape.

ZIERLER: Were there cues either from Valley or Stolper or anyone else who you considered a mentor that you tried to translate into your own transition as a mentor?

EILER: I really love and respect both Valley and Ed Stolper, especially. Ed was extremely influential on me in a lot of ways. But I didn't try to emulate either of them. I recognized that there are things that we have in common and we get along very well and I respect them and learn things from them. I'm not them. I'm different from them. The person that I most identified with at a deeper level was Epstein.

ZIERLER: Where was he in your career when you interacted with him most deeply?

EILER: He was already retired, but he was around, hanging around. He was quite old. But [laughs] I remember I saw him give a presentation—he gave a division seminar or something, and it was totally incoherent. Nobody could follow what in the world he was talking about. I mentioned to Ed, like, "Wow, gosh, I wish I had been able to see him talk when he was younger and"—dot-dot-dot—"more together."

ZIERLER: And Ed's like, "No, he was always like that"?

EILER: He's like, "No, no, he's always like this."

ZIERLER: [laughs]

EILER: Totally—and he just—his whole—he had a kind of dithering, wandering—but decisive. You couldn't tell where he was going, he couldn't tell you where he was going, but he's going somewhere, he knows where he's going, and he can sort of issue instructions through gnomic utterances. It never made a whole lot of sense, but if you just listened to his judgment, it was good, and he had a very good instinct and sense for where he could contribute. He was never really thinking, oh, I'm going to help these other people with this thing, or I'm going to fill this role. He just wanted to discover things, or explicate things. Take something weird that you've noticed and understand it. He was just wandering around with his flashlight just shining it on things, and focusing on things that caught his attention and were interesting to him. He just had impeccable taste in what was interesting in the long run. And he was totally right. Even people who would make fun of him—his lab practice was a little sloppy, and he was kind of a funny guy—but his taste was perfect. Like everything he touched turned to gold. It wasn't that I wanted to be him exactly, but I related to that. I knew he was doing what he was doing for his own internal reasons, and he was living by judgment and seeking out newness, seeking out discovery.

ZIERLER: Before we get too far afield I want to revisit some aspects of the research, because I think they're really interesting. The Mars meteorite—has anybody thought about this before—is that sort of Mars Sample Return via Mother Nature?

EILER: Absolutely, yeah. We have, I don't know, hundreds of kilograms of Mars rock already in our collections. The only problem is, it's selective, and it's selective—

ZIERLER: Isn't it the opposite of selective? It's like it came here—

EILER: It's highly selective, but being selected by a stupid person.

ZIERLER: [laughs]

EILER: They are not random pieces of the surface of Mars. They are random pieces of the things that survive getting hit by a meteorite impact at kilometers per second. Most of what you're interested in is destroyed in impacts like that. What survives are rugged, intact, igneous rocks. I just went to Yosemite this weekend. Imagine I want to understand the biome of Yosemite Park, all the amazing Sequoia trees and all the rest of it, and all the rivers running over waterfalls, and I just want to see the whole thing. What I get is fist-sized rocks that survive an asteroid impact. I would get like a chunk of molten granite and nothing else.

ZIERLER: Because it's all obliterated.

EILER: Everything is obliterated! Nothing can survive as a rock lofted to space other than these really rugged things. Our meteorite collection is almost entirely made up of coherent, igneous rocks from the shallow crust. They can't be too deep because otherwise they won't get excavated. They can't be weathered things and sediments and soils and sand dunes. All that gets blown away. They have to be just these special kinds of rocks. That's fine, I'm glad that we have them; it's not enough. We need more.

ZIERLER: As you started to become involved in this community, could you extrapolate the narrative of Sojourner as a technology demonstration, ultimately we're going to get to Curiosity to see if we can get to Perseverance, to get to Mars Sample Return? At least in your imagination, could you see where the technology would ultimately enable the science that would be most interesting to you?

EILER: Yeah, although simultaneous was like the Mars Orbiting Observatory crashing into the planet because some idiot mixed imperial and metric units. That also is part of the narrative. I don't design satellites. I'm just watching this like all the rest of us are, but with some skin in the game in terms of research interests. An optimist over that arc would look at it and say, "Of course it ends in sample return and the discovery of life, and blah-blah-blah." A pessimist would be like, "Well, half these things are going to crash. We had a good run of a couple missions, but how far can this really go?" When you see how the stew really gets made, you understand that a lot of the technologies that get flown—yes, they're building on each other; yes they're getting better and they do amazing things; most of them are not really tested when they fly. Many of the analytical instruments, to this day, that are on the Perseverance rover, people on Earth are trying to figure out how they even work. Like yeah, but you flew it already! You built it ten years ago! How do you not know how this works? We didn't have time! Somehow we didn't get it together. We don't know how it works. There's something beautiful in that, though. What if you stopped and understood every one of these devices perfectly? You'd never fly anything. So they're getting it done. It's probably good that in the end the engineers drive much of this process.

We have almost perfected, knock on wood, the process of getting to the planet and landing and so forth. The mechanical engineering of making these things work has gotten really exceptional, and the engineering of the scientific observations, it keeps moving forward in a kind of random-walk fashion. In the end, it's not what's going to be decisive. The highest-level questions that we want to answer about the planet, we will answer through returned materials plus satellite observations. The observations you make on the ground, they're important, they're exciting; they don't have to be perfect. There's other things going on as well.

ZIERLER: You omit manned missions to Mars. This is a not-in-our-lifetime proposition?

EILER: [pause] Probably not in my lifetime. I'm 56. Do I think that there will be people wandering around on Mars taking selfies in the next 30 years? I doubt it.

ZIERLER: That's what we're looking at? It wouldn't even be the follow-on to Mars Sample Return? There's one after Mars Sample Return, and then this would be the one after that, probably?

EILER: The thing is, the hurdles to be crossed for a person to go to—first of all, there's plenty of people who will say, "Oh, I'll go to Mars even if there's no return back." NASA is not going to do that, okay? Maybe there's some private company that will do it as a nihilistic act of self-aggrandizement or something.

ZIERLER: Can't you see Elon doing this?

EILER: Maybe? If he promises to go himself, that'd be great.

ZIERLER: [laughs]

EILER: There are people who will say this casually, that they would happily go without the ability to return. But that's not a mission plan. The mission plan is going to be—

ZIERLER: That's a suicide mission.

EILER: It's too nihilistic. Nobody wants to watch this happen. Most of the reason why you send a person to Mars is so the rest of us can watch a person go to Mars. The thing the person will do while they're there won't be very important, at least not at first.

ZIERLER: It won't be on the headlines for nine years.

EILER: They'll walk around. They'll pick up a rock. It will be a lot like the other rocks that you already have looked at there. They'll like make some fake air and stuff. They'll like grow a plant. They're not going to do anything that important. The important thing is, there's a person there, and I know that that's happening. That's the value. That value is greatly diminished if they're dead, okay? [laughs]

ZIERLER: [laughs]

EILER: It's just not—it's less exciting! The plan is going to be, you send a person, they don't die of some horrible wasting disease on the way there, they survive the descent and landing, they do their thing, they get back in a magic rocket, and they come back. That's the arc. We are so far from doing that arc. You'd think, like, oh, yeah, but we went to the Moon. This is nothing. The Moon is like right there. It's super easy to land on the Moon. It's trivial to take off from the Moon. There are no problems compared to going to Mars. I just think we're very far away from anybody seriously doing that. And where's the investment? Who is actually investing, other than a few simple experiments where they lock somebody in a room for six months and then ask them what it was like? There's nobody really investing at the appropriate level in making this happen. They could. I'm sure they could. But think of the effort that would be called for. I'm not counting on that one.

ZIERLER: Your work on the hydrogen economy—you're a dyed-in-the-wool basic scientist. Thinking about Sam Epstein, the metaphor of the flashlight, it's all curiosity-driven, regardless of applications.

EILER: Yes.

Considering Translational Geology

ZIERLER: What was that like for you when you were doing research that had obvious, in-your-face, potential applications, particularly at a time when we're starting to talk about alternatives to fossil fuels and sustainability and all of these things?

EILER: To continue the metaphor of having the flashlight and you're shining it around and seeing things, the flashlight hovers on things that are interesting, and that interest can come from a lot of different directions but often it's just human interest. I did some papers on dinosaurs. It's not because dinosaurs are important. They're not that important, okay? They're all dead. What's the big importance here? They're interesting! Everybody is interested in them. They're giant monsters that ruled the Earth. They're just intrinsically interesting. Why study them instead of the primitive—the therapsids, the early mammals? Scientifically, they are probably more interesting. Because nobody knows or cares about therapsids. They care about the giant monsters.

The hydrogen economy, to me, it's a little like that. I don't have a committed belief that hydrogen-based technologies are going to be a singular solution to climate change or sustainable energy production. It is plausible that they will be a significant part—a percent, two percent, three percent. That's not nothing. You need a bunch of one or two or three percents to actually replace the way we've been doing things. So it's relevant, but it's not because I think it's of singular importance. It's just—peculiar. There's something about it that is different. It's a material, a set of technologies, a process that's just fundamentally different than the way we've been doing business in a way that I think is sort of interesting. It's a fuel like our existing fuels, and yet it's other. You make it in a different way. It has different properties. It poses different problems. I think it's just enough to trigger a human reaction of curiosity. It's the same reason why if you saw a paper about it in Popular Mechanics, you'd go, "Okay, I'll read that while I wait for the dentist to call me in," instead of something else.

ZIERLER: When the industry scientists or the industry-adjacent scientists were starting to flip out about this research, was there an inflection point for you where you had to make a decision whether to go deeper down the rabbit hole or not, in the sense that maybe it's a good thing that industry was upset, because there is now an opening for you to improve the system and to make the energy better than it would otherwise be?

EILER: I never felt like this was going to grow and grow and grow until it overtook my research career and became most of what I did.

ZIERLER: Like becoming a hydrogen guy and then a startup and then you stop being a Caltech professor?

EILER: Right. The scale and structure of the hydrogen problem, understanding the natural chemistry of hydrogen, it was always going to be something that a scientist like me would write a half dozen papers about, maybe set down forever, maybe pick back up later. I had a paper about hydrogen last year, and we'll probably do another couple of them in the next couple of years. It's one of these things that when you spot interesting little sides to it, there's an opportunity to make things better. There's an opportunity to contribute something. But when you don't spot those opportunities, I don't want to be part of the grinding, day in and day out. First of all, a lot of it is advocacy. I don't do advocacy. I'm not interested in advocacy, for anything. I think it's inimical to being good at science. I don't believe in it. I think it's kind of dumb in a situation like this, where there's 50 different things that are kind of clever and potentially useful. Why would you be an advocate for that one? They all should be explored.

I also don't like the idea that there's a thing that you are not critiquing. This is poison to science. You have to be willing to kill your darlings, or whatever it is they say about playwriting. I would never invest in it in that way, and yet there's new opportunities that pop up. Like the things that I'm working on currently, the basic vision of how it would be interesting to add something more to the work I did before on hydrogen is, now we've figured out how to do the clumping business on natural hydrogen, so now we're learning things from it. We're sort of merging the research I did before on hydrogen with the study of isotopic structure or ordering.

And, there's a new problem, something people didn't talk about a great deal in the year 2000 of the hydrogen economy—where do you store it all? Now people are actually facing the practicalities of creating and moving large amounts of hydrogen. You're going to need to have big storage reservoirs. They probably should be underground. Hydrogen is food to microbes, so you're basically throwing roast beef sandwiches down a hole and seeing, like, what happens? Well, somebody is going to eat them, okay? And what happens? How do you watch that? How do you interrogate it remotely? If all I have is a sample of hydrogen gas from a reservoir, can I tell whether somebody is eating it or not? Can I tell who is eating it? Can I tell where in the system it is happening? Questions like that, it is challenging to answer them with a molecule as simple as H2, but there are ways to contribute things that aren't known now.

ZIERLER: If the numbers weren't as miniscule as they were—overall contribution, one or two percent—if it was like when they talk about nuclear fusion, really being a gamechanger, like portable plants, just a whole new energy infrastructure here—if the numbers that you were looking at for hydrogen were not one or two percent but like 40 or 50 percent, would that have changed your approach? Would you have forced yourself into a more applied framework?

EILER: No, I would not.

ZIERLER: I thought not, but I wanted to ask.

EILER: The science side of like what do I have to understand to go from two percent to forty percent, there are some basic science questions that are natural science questions. That's the thing. I'm not a materials scientist. I know enough about it to do a thing or two on the side. But the part of this where I can actually do something is in the natural science of it, more in complex experiments that are too complicated to be fully controlled, and those are basically like natural systems. They are human-made but they are organic in the sense that a natural system is organic. Those sorts of systems, I know how to come in and learn something that we wouldn't otherwise know. When I spot things like that, I have an urge to go and work on them, and if it seems important, then I would absolutely do that. But that's two papers. Then if there needs to be 50 papers, somebody else can write the other 48. I don't need to devote my life to this. Once I've already shown, "Oh, I can know this about the system by measuring this," great, now you go do it. I don't have to do it anymore.

Tenure Will Be Whatever it Will Be

ZIERLER: We'll close out today's discussion with something of a cliffhanger. In the way that you've painted the way you went about research, you were doing a little bit of this, and a little bit of this, and you were sort of all over the place. The thing that you knew was going to be new and highly impactful and was going to take you to that place that we idealize what a Caltech professor is, that was all sort of in the works, but that was only going to come to fruition after the tenure clock came up.

EILER: That's right.

ZIERLER: The question is, in year four and five and getting into year six, are you sweating it, or no?

EILER: No. I had a conversation about this with Ken Farley, who was my closest on-the-ground, day-to-day confidante, I would say, on the faculty at that time. I remember it distinctly because we were in Toulouse at an international conference, just walking around in the street talking. I had just given a talk about one of my papers on igneous rocks, and he said, "Yeah, that was good. That's helpful because you'll be up for tenure in a few months. How do you feel about that?" I told him, "I'm so sick of it. First of all, it's not my problem. I don't have to decide whether I get tenure."

ZIERLER: [laughs]

EILER: "You have to decide. And whatever you do, then I'll get up the next day and I'll do something. Either I'll do it here and I'll move and I'll go somewhere else. It's not my problem. It's your problem. You deal with that. You earn your paycheck dealing with that. And tell me when you're done!"

ZIERLER: But part of being at peace with that is you feel like you've done what you needed to do.

EILER: Yes and no. I felt like it would be dumb for them not to tenure me, because in terms of just the pile of papers and citations, I clearly had done it. I wasn't satisfied that I had achieved what I wanted to achieve as a scientist, but I knew the direction I was going to go to reach that. If they couldn't see how I was going to grow, I didn't feel like it was my job to try and push that down their throats. They're either going to see it and I belong here, or they're not and I belong somewhere else or doing something else. First of all, it does no good. What am I supposed to do? Call them up in the middle of the night and beg? It's stupid. I did what I did. I am who I am. Either that's what they want or it isn't. That really is how I felt at that point.

ZIERLER: We'll pick up next time on the philosophy of how much of a tenure decision should be aspirational. We'll go there next.

EILER: Okay, good!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Tuesday, November 14, 2023. It is great to be back once again with Professor John Eiler. As always, thank you for having me.

EILER: Yeah! Thank you for coming, David. It has been a pleasure.

ZIERLER: Today, before we go back in the chronology, we left off right at the point where you had sort of let go, and you were very Zen about it. You had done what you needed to do. It wasn't your decision; it was the decision of the tenure committee whether to make this decision for you, and you were okay with all of that. I want to ask you now on the flip side, as a senior faculty member who has been involved in tenure decisions—and this is intrinsically a philosophical question—in making the best decision for tenure, what is the best mix of retrospective analysis, what has this person done up to this point from point of hire to the tenure clock is ringing, and what is the best mix of trying to extrapolate from within that assessment where they might be going and what their promise might be, and what that looks like for yes or no? I wonder if you could wax philosophical on that.

EILER: That's a great question. I believe that you tenure a person because you believe they are going to be an intellectual leader in mid-career, a real intellectual leader that everybody in the world in their discipline would say, "Yeah, this person is distinctive, unique. I follow what they do. It impacts me." It doesn't necessarily have to be that they're in charge of the biggest thing happening, or that has the most money or whatever. They have to be this unique intellectual leadership in their discipline. That's the thing you're trying to predict, whether that's possible for them. It also I think is important to realize about yourself as a mid-career person when you're making these sorts of decisions that nobody is their best every year. People wax and wane, and they have ideas that end up in dead ends, and they have funny things happen in their life or whatever. People rise and fall and rise and fall. But at their peak, when they're having a great year, is this person capable of showing true intellectual leadership? That's what you love to tenure a person because you see that in them. It's sort of the ideal. If you look at a person and you think, "Well, I'm 80 percent of the way there," well, maybe you round it up, but this is the thing that you're looking for.

What is the purpose of the five-ish year span between hiring and tenure? What do they have to do during that period to help you reach that understanding about them? I would say mostly they need to kind of grow up a little bit. It sounds patronizing because everybody you hire is an adult and has already been working in this area as an apprentice and a journeyman and so forth, for probably a decade since they graduated college. So, yeah, they're an adult, but there's levels to this thing. Are they able to take on all the new responsibilities of being a faculty member? Which is sort of like being a small business owner. There's a lot of bureaucracy that distracts you. There's all the people management skills, the capacity to grow into a position where others rely on you, others look to you, others expect you to deliver, every time, when you show up. There's a maturation process that has to happen. Can that occur and be consistent with that person's creative spark? Are they able to be a grownup and be productive and be creative all at the same time?

It's hard to predict about people. There's a lot of people who you look at, at hiring time, and they're very clever. You fall in love with their creativity, or extreme technical skill, or math ability or whatever, and you love how sharp they are. But then there's a kind of personality test that kicks in later in life. Do they have the character? Doesn't mean that they have to be particularly nice. You'd like it if they're nice. It's not necessarily character in the sense we mean it in a colloquial sense. But do they have the capacity to grow into this multifaceted position and then really move forward, with their whole life? With their whole professional life, can they move forward with it? How do you know that that's happening?

It'd be nice if the proof was they had five papers that were all really well cited and important, but you can't look to outside impressions about these sorts of things. The papers that you really want your faculty colleagues to be writing are things that people pick up literally 50 years from now and go, "Wow, that was cool." Of course everybody in the world can do this now, but think of what that meant then. The insight, the whatever, the technical capability. Think of what they did and what grew out of it. That's the kind of paper that you want to be seeing people writing. How do you know that that's what you're looking at? It has almost nothing to do with what the broader community of colleagues will say and write letters about that person or whatever. It sounds super elitist, but not very many people have judgment that I would trust to say that about a person's work. I trust my own judgment about that. I feel like I can look at their papers and I know how I feel about it and whether I think that there's something there, like a capacity to write papers of that sort, and to train people who then will go on to write papers of that sort. It's so idiosyncratic that you can't say specifically what somebody has to do to get there, but you know it when you see it.

ZIERLER: You're really emphasizing future potential.

EILER: Totally! The five years between hiring and tenure, they just fly by, and half of that time is spent—if it's a lab scientist, which many Caltech people are, they're doing stupid stuff like figuring out how to get the cold and hot water pipes right in their lab, and blah-blah-blah, and making people deliver things, and trying to raise money, and all this junk that you have to do to make it all happen. They're just learning how to do that. Expecting them to be simultaneously a sparkling intellectual leader—I think there's a misconception that you realize a person should be tenured here because they have like a montage scene from A Beautiful Mind. You know, at the chalkboard—

ZIERLER: [laughs]

EILER: —the music is swelling, the proof happens, and so forth. This is a totally unrealistic expectation to have of a person who is just a few years into their career. I know for myself—my tenure case may have been easy, it may have been hard; I'm glad I didn't have to be part of that discussion—I know I was nowhere close to done. I had done enough to be acceptable, but I had not done a single thing that I know I would look back at the end of my career and say, "That was an important decision. That was something that really led to things that to this day I'm seeing unfold in various ways."

ZIERLER: In a sense, you were a beneficiary of this perspective that you have on junior faculty.

EILER: Absolutely, and I know that there are senior colleagues of mine who have the same perspective. I don't know if they would state it the way that I stated it, but this sense that you're looking at your colleagues—how old are they? You finish your PhD at, say, 28 or something. You're hired. You're done with your postdoc stuff usually around 30 or so. That would be kind of young, maybe, but that's plausible. You might be 35, okay? Thirty-five is like you've already grayed out of the NFL. You're ten years past your peak as a track athlete or something. But as a scientist in basically all disciplines, you're probably just hitting your stride, unless you're some kind of genius or something. In the Earth sciences, oh, you've still got a long road ahead of you. The Earth sciences, there's so much detective work that is based on reaching conclusions about things that you didn't see happen. You have tiny scraps of evidence.

ZIERLER: It's almost like you're on a geological timescale.

EILER: Exactly, exactly. There's a lot of inference and drawing connections from little observations. You're kind of Sherlock Holmesing the thing. Sherlock Holmes only can be Sherlock Holmes because he knows the names of all the crazy tobaccos, and he knows all this stuff. What if Sherlock Holmes was 12 and didn't know anything? It doesn't matter how smart he is. It's irrelevant. He has to live life, and then he starts to become Sherlock Holmes. That's very true in the Earth sciences. You just have to live it for quite a while, you get gradually better and better and better, and then you're finally really able to make informed, intuitive decisions and judgments when you're 10, 20, 30 years into the whole arc. Before that, you have little areas of specialization where you shine, and then a lot of other stuff where you're kind of a dummy.

ZIERLER: This struggle to try to ascertain some future intellectual leadership and impact, is that to say that that is never fully apparent in the junior faculty years?

EILER: There are traits that you absolutely have to see.

ZIERLER: I'm not talking about traits. I'm talking about what you're trying to figure out, who this person will become. Is that ever evident in a junior faculty member? Are those traits ever fully—?

EILER: Fully manifested?

ZIERLER: I mean like an Ed Stolper or a Richard Feynman.

EILER: I think it is totally possible. There are people who go through the maturation process faster. Ed Stolper is a great example. He absolutely did it. As an assistant professor, he was doing stuff where you could just pull out paper after paper after paper that he wrote as an assistant professor—crushing it, crushing it, crushing it, home run, home run, home run. It was very purposeful, intellectually broad, drawing on all the latest tools and things. It's an incredible body of work. It is like a mid-career body of work. How did he do it? He's a special individual, but also he was operating at a very high level relatively independently early in his career.

ZIERLER: I heard stories, at Harvard, as an undergraduate, he sat in on graduate classes and would engage the professors at a higher level than the graduate students would.

EILER: Oh, I totally believe that. First of all, he was extremely well trained. He was a student of a guy named J.B. Thompson, who was sort of like the last great classical thermodynamicist who didn't have to be anything else other than that. Ed is a great classical thermodynamicist, but he also has to be other things in order to be successful in the modern environment. He developed a classical, rigorous foundation that still counts for something. I don't care how buzzy all the latest important-sounding problems are; if you can't manage rigorous bodies of work like that, you're not ready to play in the major leagues. He got that kind of training very early. He went to the University of Edinburgh for the first couple years of graduate school, and he worked at a very high level there. He was working in an electron microprobe lab. Today these are thought of as sort of—they're expensive, but basically standard automated devices that everybody who studies solids has to have access to. Back then, they were a cutting-edge tool, and it was special for him to be able to be doing that.

They then offered him a PhD. This is anyway the story that I heard from him. They offered him a PhD—or maybe I heard from folks at Edinburgh. I also spent a bunch of time in Edinburgh for grad school. They offered him a PhD, and he turned it down. He said, "No, thank you very much, I'll take like a master's degree or something, and I'll go back to Harvard and get my PhD there, because that's where I want to complete my training." This gives you a sense that he was approaching his training years not as—he knew he was an apprentice, and he was apprenticing to be a very top-tier scientist in his own mind, early. If that's your mindset, then by the time you're ready to be hired as an assistant professor, you've already spent five, six years with your head really focused on preparing yourself for this level of work. That's just a special—I don't know whether there was something in his family background or his high school education or whatever—I don't know how he got himself this level of focus on scientific accomplishment at such an early career stage, but he definitely had it.

One of the most famous things he did as an undergraduate is he and a colleague or two, who were also grad students at Harvard, they cooked up an idea that a group of meteorites that are called achondrites—that is, they are not chondritic, they're not primitive objects; they came from a body that melted and produced a crust, like the Earth melts and has a crust—and they proposed that they were from Mars. At the time, there was a group of dynamicists, people who calculate Newtonian sort of motions of bodies in the solar system, who said, "It's physically impossible. You can't take an object off Mars and have it land on the Earth. It just can't happen." And just more generally, how would you prove such a thing? These are just a few rocks out of thousands of meteorites. Why do you think you have pieces of Mars? It's kind of ridiculous. And they're doing it as graduate students! And they don't have the shelter of some senior éminence grise who is sort of blessing their paper. It's just them.

He went and gave a talk—I think it happened at maybe MIT or something—when probably at the time the most famous isotope geochemist, and geochemist generally in the world, a guy named Claude Allègre, from France, was in the audience visiting. As Ed is giving his presentation, about, "Oh, yeah, these rocks are from Mars, and here's what that means," the guy is in the back of the room yelling, "Bullshit! Bullshit!" Which is like an old habit of his, that he would yell things like this at seminars. Okay! This tells you, Ed is like—his experience in grad school was like the guy in Saving Private Ryan who drags himself up the beach, takes the pillbox, empties it out with his flamethrower, lights a cigarette. Okay?

ZIERLER: [laughs]

EILER: That arc, he experienced that very young. I think that just means he was ready in a way that almost nobody is ready. Yes, he's very smart, but lots of people are smart but they have not hardened their character and made themselves capable of really persevering and making good judgments and accomplishing big things. It takes people a few years. You're basically watching people over their assistant professorship develop in this way. Yes, they're writing papers and things, and you hope that they're good, but you're really watching, how is their character developing? Are they turning themselves into somebody who is capable of something like this?

ZIERLER: What about the expectations? This is really a generational question. If you ask the old guard, and they look at what current junior faculty, their expectations, a current junior faculty member, it's almost like they have to be masters of seven different careers—research, and funding, and science communication, and committee—all of these things that when you talk to somebody who started as a professor in the 1960s or 1970s, they said, "I just had to be a good scientist. That was the expectation." You're generationally in between that.

EILER: But I started early enough—I wrote my first paper on a mechanical typewriter. My collection of papers that I knew from the literature were literally things I checked out from the library. This is such a completely different era. And the amount of money—there was almost no money. My advisor's lab was one of the best labs in the world at the time. The instrumentation in his lab today, it couldn't get a position in the like junk heap in my basement. Just the amounts of money involved are exponentially bigger. Yet, the capacity to get that money somehow is harder, actually, in a way. How can we have more money if it's harder to get? It has become very divided. There's people who figure out how to get a lot of it, people who can't get any of it. The rapid rise in income inequality in the economy, it's like that in funding. There's so many sides to this, but I totally agree that the job today is radically different than it was when I started. That job was radically different than it was 20 or 30 years before.

But I think there was kind of a continuity, as I understand it, in what the job was like between probably like—before World War II it's hard to say, especially in the U.S., because the hard sciences were just not that serious before World War II. So let's say 1950 to maybe 1980, or even 1990, there was a continuity of what the experience was like for people. You look at the careers of some very prominent, accomplished scientists and you realize, "This person wrote 11 papers in their whole life." I couldn't get by writing 11 papers in half a year! The grind of productivity is enormously, enormously greater. That's just personal computers and stuff like this. It's so much easier to write a paper. You sit down, let all the crap spew out of your fingers, hit return, you're done. Of course there's a process behind that, but it's possible to do an enormous amount of writing. Because of time limitations, people actually do less reading, so I don't know what's happening to all these papers. We just throw them [laughs] up into the air and they get consumed by the wind or something. It has become madness, the way that it works now.

Big Questions and Focused Research

ZIERLER: There's not necessarily more science to be writing about?

EILER: Probably the most challenging thing for any scientist to ask themselves at any given moment is, "Where is the revolution happening in the sciences generally?" It might not be in your field. Don't be an egotist here. Most scientists are sitting in fields that are not ready for a revolution, and some of them are dying out and they will sort of diffuse back into the chaos and some other discipline will come up. But somewhere near you, a revolution is happening. It might be visible, and even better, it might not be that visible, or there might be an opportunity for a revolution that could be seen but maybe you haven't seen it yet. These sort of very high-stakes questions about the way the field will evolve, they are so hard to anticipate. Even very clever people, they can't force it. Often if you hear like how this certain person stumbled into a revolutionary idea. it's because they were the right person at the right place. They met the right other person. They talked about the right thing. It's just totally fortuitous how it comes together in the end for one individual.

But it's hard not to ask yourself that constantly. "What should I be doing, other than just writing this next paper?" The distractions of the way things work today—and they just keep expanding. There's the distraction of publishing large amounts of papers. There's the distraction of being judged. People weren't really judged in the same way. Of course, people would appreciate if they were a good scientist, or they were a less accomplished scientist, and so forth, but the idea that you would—there wasn't enough visibility to judge each other. We didn't know what each other had done, other than our close personal associates. Everyone is sort of exposed, on a visible playing field, and the only metrics that—you know we're being judged. What will I be judged based on? Quantifiable things. My h-index and so on and so forth. That becomes a rat race. Then there's the money rat race. Then institutionally, all institutions are becoming radically more bureaucratic. I think it's mostly driven by conservatism in the face of legal threat. Whether it works exactly this way at Caltech or not, I'm not certain, but I suspect it does—you basically as an institution look at, what is my exposure to uncontrolled costs? It is being sued for things, or somehow shamed in public about something. How do I avoid that? I don't know. It's not my job. I don't know how to avoid that. I'll hire a lawyer. It's their job to know that. They will come in and they will advise me. What is their advice? Do nothing. Okay?

ZIERLER: [laughs]

EILER: How do I do nothing? How do I do nothing while seeming to do a lot of things? Well, bureaucracies are excellent at that. So start filling in the void. Fill in, fill in, fill in.

ZIERLER: Oh, God. [laughs]

EILER: I need a person in this position. Why? Because when I get sued it's important that that person exist, so they can either be thrown into the flames or—

ZIERLER: [laughs]

EILER: —I can say, "Look, I invested in this. There's a person there." Then that person needs a boss and several people to be the boss off, and then those people all need some bosses, and so it just—and then suddenly they think that they're making real decisions, and now you're done. That process is inexorable. I don't think I've ever seen a place where it went backwards. And after two thirds of my career here we had staved it off, but it's finally catching us, I think. It's finally getting us. It's like being caught in a woodchipper. Once your shoelace is in the woodchipper, you're done. It just pulls you in. I would say as an institution, that's the thing we most need to be thinking about. Even in the short term, how do you resist it? What are you supposed to do? Get sued? End up on the front page of The New York Times with somebody saying that we're all a bunch of jackasses? It's very hard to make wise, long-term decisions in the face of the risks that institutions face.

ZIERLER: What about the size of one's research group in the junior faculty years? Some people will have a bunch of graduate students and a postdoc. Another will have one or two. How do you determine what's good and what's not good? What's a sign of ultimate success?

EILER: First of all, good is almost always somewhat smaller than what they have. Almost everybody overreaches in the size of their group. Then that immediately creates financial burdens on them, but that's just the beginning of it. The real burden is you have to teach them things, and there's just so many people. You barely know yourself what you're doing, and now you're having to teach all these people. Then the writing begins, and oh my God, now you have all of this writing that you're editing constantly, and most of it isn't very good when it first appears on your desk. Just every person you add to your group is a massive increase in your workload while you're supposed to be doing something else. You could train 20 students and probably they won't do anything remarkable by themselves in their first few years as graduate students. So, where are your accomplishments? All you did was train a bunch of people that didn't really do anything yet, and you didn't do anything because you were so busy training and mentoring them, and so forth.

I think the best thing that an assistant professor can do is to exercise very harsh judgment about the capabilities of the people that they let into their group early on. It's not only can they do math or do they show up for work in the morning. Can they work with other people? Can they work with you? Are they reliable? Are they driven? Are they interested in interesting things? A lot of people go through grad school. It's just a constant flood of people going through. Many people in the midst of that process, they don't know exactly why they're there. It's understandable. They haven't developed and cultivated strong interests yet. They don't have a lot of exposure to things that will help them have good judgment. So it's very easy to have people who are a little aimless at that moment. Maybe they will be great in a year or two, but at that moment they're kind of aimless. You draw them into your group, you have very little to teach them because you're just starting yourself—they would do much better in a more senior group where there's patterns to life. They can just start emulating all of the other people around them and they will make it work. You have to do that for them. There are no senior graduate students and postdocs and things to model for them what they should do. So I think a healthy thing in an assistant professor is their group didn't get too big, and you look at the people in it and you think, "Wow, they're actually flourishing, and they're all unique." Each one of them is doing something a little different from the others.

ZIERLER: One's threshold for hand-holding as a mentor, that should go up after tenure?

EILER: Yeah, hand-holding is a really interesting problem. [laughs] When I go home in the evening and I'm gossiping with my wife about how my day went, the way I would put it is, "Oh, man, I had to change a lot of diapers today." [laughs]

ZIERLER: [laughs] Even less advanced than hand-holding.

EILER: [laughs] Right, yeah. Of course it's very patronizing, but the only person who will ever read this is like some other old person—

ZIERLER: [laughs]

EILER: —a decade from now, so it's all right. Every faculty member has a different attitude about this, but I think there's an expectation today of a level of personal engagement with students and postdocs and things that I don't think was there 10 or 20 years ago. The notion that you should be personally revealing, they should be personally revealing to you, you should have dinners together and things like this—some people go way down this road. I don't really like this. Like, okay, Thanksgiving is coming up; I'll have a few people who are foreign students over for Thanksgiving so we can have a nice, big party. But there's a wall. I don't really like the idea of me presenting myself to my students as—

ZIERLER: Totally accessible?

EILER: Yeah, I don't want to be totally accessible. I want to be accessible enough to be helpful. There are several things that I think are really—they wouldn't necessarily work for everybody else, but I find they work very well for me. One of them is, everybody is given enough latitude that they really need to be making their own tactical decisions very early on, and strategic decisions by the time they're done with grad school. By the last year of somebody's PhD program, they should be doing stuff that I don't even belong on as an author. They should really be making their own decisions about things that they will be working on for multiple years. I wouldn't necessarily do all of them, but some of them I might find interesting. It doesn't matter. They should be making those choices and relationships with outside scientists and things, themselves.

To go from, "Gosh, Professor Eiler, what can I do in your lab? Are there any bottles that need to be washed?" or whatever, to that, that's a big arc. To get a person moving on that arc, they need to have a lot of freedom. If they have a lot of freedom, there's two messages that they need to always hear. One is, if you burned the mass spectrometer to the ground last night, it's okay. It's just a piece of metal. We're going to put another piece of metal in there, and we'll go on tomorrow. That doesn't matter. If you do it three days in a row, okay, now [laughs]—now there's a skill issue that's involved. But if you push yourself out to the edge and bad things are happening—there are safety issues of course, but like the risk of failure, you need to entertain the risk of failure and not feel like you're going to be criticized for it. I'm always mindful of this, to never ride people over things that they failed at—bad calculations, weird measurements—so long as they're transparent. Transparency, that is absolutely required. Success is not required. Success you can always get to. You just keep digging. Keep shoveling the gravel; you'll get to the bottom of that pile. But you have to be transparent. So the sort of scientific virtues I think of as being absolute.

Then the things that most people fear—the logistics, of like money—another thing I really feel strongly as an advisor—whether it's true or not, you should project to everybody working in your group that the money is your problem, not their problem. This drives me crazy when I see it, because it's so bad for morale, when a student hears, directly or indirectly, the message, "Your livelihood, and your ability to work, to buy equipment, to buy supplies or whatever, that's on you." Or, "It's on me but I'm failing." Even if you are failing, cover it up, okay? Find a way to put food on the table that does not make it their problem.

ZIERLER: Ultimately they have no capacity to fix the problem.

EILER: Exactly! They can't really fix it, so even if you can't fix it, don't dump that on them! Let them focus on what is important for them, not carry your burden of worries about money. Then if you do that, you'll usually be successful, somehow—I don't know, a miracle keeps happening—and you'll mostly be able to cover costs of things. Then they feel this freedom to just focus on their own judgments, interests, passions, skills, without thinking about all this nonsense. "Oh, can I go to this meeting?" "Of course you can go to the meeting! This is your job! Go to the meeting!" "Oh, can I buy some supplies for my experiment?" "Well, this is why you're here, is to do the experiment, so go get the supplies and do the experiment." Just this removing of logistical barriers, I find it very effective. It cultivates a kind of benevolent hierarchy that is good. There are hierarchies that are bad. There's lots of hierarchical things that end up in problems. That's not a bad hierarchy. That's basically a division of labor that is healthy. So long as you are always there—you're not a parent that withholds food from the table—so long as you're always giving, then it's a good hierarchy to have it be like that. It removes worry from them.

ZIERLER: All of these comments about mentoring, this is a grad student centric perspective. What about postdocs? Is that basically the in-between of a grad student and a faculty member?

EILER: They are. If grad students are apprentices, postdocs are journeymen. The journeyman needs to—at this point it should be very clear to them, this is your job, but you are working for you. This is another thing—I'm not anybody's boss. I've even had colleagues get angry at me when I expressed that I tell my students I'm not their boss. I'm not their boss. I can't fire them! They're students. The institution can do that. It's not within my right to fire them. It's also not within my right to hire them. I can choose to offer a research assistantship or something like that to them, but if I don't, they're still a student. I think it really confuses the issue to project yourself as somebody's boss.

Postdocs, it's more like you're the uncle for somebody—let's say you've got a nephew or a niece who is opening a business. I've got my hot dog cart outside of the baseball stadium, and they're going to start a hot dog cart outside of the baseball stadium. But their first day at work, their hot dogs are going to be terrible and mine are going to be great. How do I get them to understand how to run their hot dog cart? First of all, you've got to make the hot dogs every day. Now, you can't be sitting in the basement, as a third-year grad student, like, "Oh, I wonder when my next brilliant idea will come to me." Today. It has to come today. Get stuff done. That means you have to be more directly engaged with the literature and your colleagues everywhere. This is a business for you now, and you need to be producing very day. Okay, maybe you have a bad day, but producing regularly. The time constant of the thing changes. I guess today you would say building of your brand.

To go from day one of being a postdoc to day one of being an assistant professor, the major thing that changes is the way you are seen by your broader community of colleagues. Do they know who you are? Do they have confidence that you are on the right path? No amount of internet searches and h-indices and stuff like that can replace the fact that hiring a professor is a very personal feeling decision. You're bringing someone in to live next door to you for 40 years, and it's basically an irreversible decision. We were just talking about tenure. You can have as many philosophies as you want about that, but 95% of the time, you say yes, so the hire is the commitment, for all practical purposes. And people are very conservative. We know that it's not our profession to evaluate people for hires. We get tasked with it, but we're not trained to do it. We spend a minimum amount of time on it. So we're uncomfortable. We feel like, I don't have enough information to know that this is really the right decision as a fact, so I have to feel like it's the right decision emotionally. How will I feel that? Everybody around me, all my colleagues, feel that this is the right person, and I will kind of join in on that feeling.

That's a lot of how hiring works. This is what the external letters are there for. But you can make that happen yourself. "Oh, I wish I could get interviewed at Stanford." So walk in the door and say you want to give a talk. Call a friend there and say, "I'm coming to Palo Alto"—or wherever the hell Stanford is—"and I want to give a talk on Tuesday. Can you find me a room?" Sounds crazy; I have my senior grad students do this all the time. And it gets them jobs. I just had a senior student get a job at Chicago. She didn't apply for the job. I didn't even know that the job was happening until I knew another person got offered it. But they were doing some group of hires, and so, got her on an airplane, she went out and gave a talk, they fell in love, she got an offer. I think you just need to push connections with people, to get them to feel familiar with you, comfortable with you, to see enthusiasm of other people. How do I make that happen? That's the main problem a postdoc faces.

ZIERLER: The whole focus here has been on research. What about teaching? I know in GPS there's not as much interface with undergraduates as other divisions. Where there is, or for teaching graduate students, how important a metric is that for all of the considerations on tenure? Do people think about one's gifts as a teacher?

EILER: I think it matters, but the form—I think that there are maybe like three forms of teaching that I recognize. One of them is the classical form where you're standing in a lecture hall, or it could be out in the field or in a lab or whatever, but it's the structured experience. There's a curriculum. There's the webpage and assignments and all this stuff. There's that. Personally, I know that this has to happen in order to have an academic program; I'm not crazy about it. I don't feel like I'm moving the needle very much even if I do a great job. I know that over the fullness of time, the integral of the number of people, how much I changed their life, is modest when I do this.

ZIERLER: As opposed to in the lab where a key insight can be a gamechanger for a career?

EILER: Right. The other extreme is a person who is your close mentee, you are working with them day in and day out, and you get to guide them in their own—through your decisions, then they're collaborative decisions, then they're their decisions. How are their skills, their decision-making, their ethics, their value system as a scientist? You can cultivate that whole thing. Each person is a totally unique individual in this respect. You absolutely have to respect that every single person there is going to end up somewhere different that will be perfect for them. You can't think, "Oh, I'm going to have this person end up being like this other person was." Impossible. You have to get to know them very well in order to guide that process.

Then there's a sort of in-between zone that I think of as being most like the Oxbridge system of tutoring, I think they call it, where you basically hang out with the professor in their office or the library or something, in small groups—one, two, three, four students—and you're just talking over things. You're talking over a problem set, a paper, a question, whatever. Those are very effective environments for getting across concepts, and in a very time-efficient way getting to the crux of a problem and teaching it to somebody. Those latter two ways of teaching, I spend a lot of time on that. On paper, I teach three classes a year or something, and it doesn't seem like that many hours a year compared to my colleagues at other institutions. I spend way more time per week with close mentoring than most colleagues that I know. I feel like I spend a lot of time teaching. I just don't do it standing at a chalkboard. Well, I stand at that chalkboard, but I don't do it standing in a room full of sleeping kids who didn't read their homework for the day.

Bringing Undergrads Into the Fold

ZIERLER: Why does GPS not have more interaction with undergraduates relative to other divisions?

EILER: It's a very simple answer to that—nobody applies to Caltech or any other university in the United States intending to become a geologist.

ZIERLER: Is that because it's not one of the foundational—physics, chemistry, biology?

EILER: Yes, exactly. It's an alternate. It's an elective thing. Some people get it in high school at some level or another, but nobody gets really a formal training that is uniform across institutions. If there is an exam you can take for your SAT, your APs and things, it's clearly a second-tier subject. It's not how you get into good schools. You have to be an unusual person to know that you want to be a geologist at the age of 18, a very unusual person. It's something that people discover later. You're lucky if they discover it halfway through their program. Then there's other competing things. I do freshman advising, so I end up seeing a lot of Caltech undergraduates, and a surprisingly large fraction of them are concerned about earning a living when they're done with college. This sounds like a reasonable thing until you consider there's only a couple hundred Caltech graduates per year that enter the world, and the world is ravenously hungry for people who have these skillsets. Of course you're going to earn a living! You will have your pick of the litter! Any way you wish to earn your living, you will do. They don't understand it that way. A few of them do, but mostly they don't understand it, and so they gravitate towards disciplines that feel both new and densely populated, and with a lot of jobs around them.

ZIERLER: This is what computer science is now?

EILER: Exactly. I wouldn't want to denigrate that decision too much, because there's good reasons to want to be doing computer science. It's a super-important tool in all of STEM, and it's interesting in its own right. That's fine, and I'm sure a lot of them approach it with that basic science mentality, or engineering mentality. But unfortunately many of them do it because they think it's safe. Becoming a geologist doesn't feel safe, even though actually you could get a geology degree, you could get an English degree, or whatever, and if you have the kind of training that we provide all of our undergraduates, you will get whatever sort of job that you want. I really believe that, but it's hard to get across to people.

ZIERLER: For an undergraduate who wants to do geology—they're that oddball that loves rocks, and this is their path—is there a solution for them at Caltech? Can they do that?

EILER: Absolutely. We have an undergrad major and they get a good education. Honestly, all you really need to do to get a good undergraduate geology education is go outside with a geologist. That's how you learn. Other people on campus will teach you math, chemistry, and physics. You definitely need to know that, and a little biology. The geology side, the thing that is unique about applying those disciplines to the Earth, is you have to go out and look at the Earth and experience it. You just have to have a field-based education. Increasingly, that's not the way undergraduate Earth science programs work. They'll focus instead on things that are closer to environmental engineering—climate science, energy science. Great topics, very important. If you're going to go into policy, that's great. Maybe there are certain kinds of jobs—climate modeling and so forth—where that's absolutely appropriate. If you want to just generally be able to study the Earth, and you're not making a decision at 20 about exactly what that means, then just go outside! Grab a friend who knows a lot about the Earth, go outside, walk around, talk, look, pick things up, learn as you go, maybe have a conversation when you get home about classification and things. "Oh, what's the formal way that we would describe this?" "Oh, okay, there is a formalism, and it goes like this." But begin as an experiential activity. I think this is why traditionally every Earth science undergraduate did a full summer field camp. They'd go spend eight or ten weeks out in the field, learning how to make maps and so forth. That is actually where you become a geologist.

ZIERLER: This actually connects to an earlier discussion thread about the importance of Caltech faculty retaining that muscle memory for field geology, and why it's important for assistant faculty in GPS to have at least some of them to have that capability.

EILER: Yeah, I have a soft view of that around the margins of what the Earth sciences are. You can be a member of our Division and an excellent scientist, and your job is to look through a telescope at extrasolar planets. Okay, well, maybe you should spend a little time in the field or something, but it's not as directly relevant. If you study microbial metabolism and so forth, okay, maybe you like stick your hand up a cow's butt or something now and then, but basically you're in the lab doing culturing and things. But everybody else—if you're talking about, thinking about, the Earth, its materials, its behavior, its history, you have to go out and experience it. I know it sounds ironic coming from me because I run this super technical lab, and I'm basically juggling lab processes and materials and instruments and things like that, but I have this as a background, and I can do it. Put me in the saddle, I can still ride.

ZIERLER: To put a bow on this whole assessment of assistant faculty members, how much of your perspective is really Caltech-specific, given the idiosyncrasies of the Institute? It's small. We have an expectation that every faculty member is going to be a world leader in their field, that we hire on the hope and with the support that they will get tenure. How much of it is really unique to the Caltech way of doing things, and what do you think just being an academic is a universal how-to for tenure decisions?

EILER: Honestly, I think in my heart of hearts, the way I feel about this is unique to Caltech. I don't even think it translates that well to other highly reputable institutions. I won't name names because I don't want to get into a pissing match [laughs] with some colleague at another school, but I visit a lot of universities, and every single one I go to—they're mostly great universities; they're not like us. They're different from us. They're great in their own way, in a different way. I think there are other ways of being a very good professor that work at those institutions that doesn't work here. You could maybe squeak by into tenure and be a productive colleague and do things that are helpful to the Institute, and helpful to your students and so forth, but that's not furthering the long-term mission of the institution, why it exists. If we dissolved back into the ether, the basic activity of teaching 19-year-olds differential equations, it would go on. There's a dozen institutions just in the L.A. Basin that will do a great job at that. You could probably go to PCC and have that done just fine. But something will have been lost from the world. We actually have a unique role as an institution. There are other individuals, other groups, other universities, that are also pursuing that goal, but there are not many of them, and we are one of that small group. I think this is why we need to have strongly-held views about what it means to be successful here.

ZIERLER: Let's go back now in the chronology. We left off with a cliffhanger for you—out of your hands. How did you get the news? Do you give a talk? Do they vote up or down right then and there?

EILER: No. Ed wandered into my office a couple months later, it was probably a few days after they had made the decision at the IACC level, and just told me, "Hey. You got tenure." Then we had a very small party at my house. I remember Jeroen Tromp, who was a colleague in geophysics that was here at the time, he brought a super nice bottle of champagne, which was greatly appreciated. We had maybe a dozen, two dozen people over. Then I carried on. It meant a lot to me. I have a very strong sense of there being two parallel streams in my life. One of them is my role as a scientist here at Caltech, and the other is my role as a father, husband, homeowner, things like that. Keeping my family going. Honestly, the tenure decision meant more for that second stream. It basically said, okay, now everybody is taken care of. Even if I get hit by a bus tomorrow, it's going to be okay. We have a stable situation. This is going to work. If you go through graduate school and postdoc period with multiple children, a disabled child, this doesn't feel obvious that this is going to be the outcome. A lot of people have outcomes that are not terrible in the big picture of things—they like are still alive—but life is hard if their career doesn't work out well and they have these kinds of responsibilities. The tenure decision meant a huge amount to me in that way.

Professionally, I experienced it as just a starting gun going off that said, "You can stop thinking about this short-timescale, tactical maneuvering, of this paper has to come out by this date," and "Oh, I guess I really should do this next grant," or "Gotta get a grant in for this particular thing because the odds are good I'll get it." All of that thinking just blew away in the wind, and I felt like finally I can just approach my research career in the way I want to approach it.

ZIERLER: You can now focus on achieving that leadership that you articulated to me.

EILER: That's right. I knew I had not achieved it. Even though I could write review papers, and some of the things I was doing then remain highly cited—they're not like embarrassments or anything; they're good papers—I knew I had not attempted what I needed to try to do, as a scientist.

ZIERLER: Is there a tenure talk? Is there an opportunity to lay it all out for what you've done so far?

EILER: No, and I don't know that it would be helpful, because it would focus the attention on judging specific research accomplishments made by that date. I could have given such a talk, and it probably would have been successful, but it also would not have been representative of why they should have tenured me. They might have tenured me but for the wrong reason.

ZIERLER: [laughs]

EILER: The reason to tenure me is what I was about to do, and the only reason I was about to do it is that as soon as you tenure me, I'll feel free to do it. To have all of your focus be on, well, he wrote these eight papers in the last four years, and they all have h-indices of blah or whatever—who cares? This is all just going to diffuse away into the ether in time. What is important that's going to happen here? That's in the future.

ZIERLER: Absent that talk, looking forward, what is the information that senior colleagues need? What do they have to know?

EILER: They have to know me. That's the main thing. It helped very much that Ken Farley and I shared a lab. He's a private person, and he doesn't gossip a lot and things like that, but I think it was valuable for their capacity to know who I really am that he is sitting there, 20 feet away from me, while I am doing things that did matter to me. I started doing experiments that did matter to me in the runup to my tenure decision. He was aware of what was going on, and he knew what kinds of things I was trying to do. It all seemed very weird and speculative and unlikely to succeed at the time, but that doesn't mean he couldn't appreciate why I was doing it. He could read, what are my values as a scientist? What am I trying to do? What are my skills that I'm applying to those goals? I think it really helped that he knew me in that way and could articulate that back to the rest of the faculty. Although of course I don't know what the discussion was like, so who's to say.

ZIERLER: Now, within GPS, you clearly have a reputation—people can go to Eiler because his lab can make stuff happen. People go to you to solve problems. You have capabilities. Did you already have that or were you building that reputation by the time you had achieved tenure? Was there anybody besides Ken that you were working with in that capacity?

EILER: All of my published work in the latter half of my grad career and then through my four-year postdoc—which, four years is a long time to be a postdoc, especially if you write a lot of papers; it really piles up—all of it was centered on the ability to make measurements that were both a little unusual and done very well. This expertise in the lab was always part of who I was. The only question is, what do you aim that at? If I measure something boring and unimportant extremely well, even if I use a creative technique, who cares? You have to somehow use this capacity for good. That's what I was trying to figure out. But they knew that I had that capacity. The postdoc work I did when I was mostly mentored by Ed was very central to the things that I was doing in his group.

ZIERLER: As Ken was getting pulled more and more into JPL Mars stuff, did you self-consciously stop yourself from doing that? Did he have opportunities that you didn't?

EILER: Yes and no. I got encouraged to apply for roles in MSL and MSR mission teams, and I did. I applied to both of them and was rejected from both. I don't really know why. Honestly I don't even think about it that much, because I don't really care. I think they made kind of stupid decisions. I know more about the measurements that they're making than most of the people working up there do. But there is a culture to the way their groups work, and for whatever reason, I wasn't the right person that they wanted in that group, so I didn't do it.

ZIERLER: Was it appropriate in retrospect how low-key the news from Ed was that you had gotten tenure?

EILER: Totally.

ZIERLER: That's the Caltech way?

EILER: That's the Caltech way, yeah. It's the right way to do these sorts of things. The only thing kind of like it, that they made a bigger deal of, like there was a cake and a big group of people and stuff, was when I got into the National Academy. That's a more visible public thing. In fact [laughs] I knew that they were going to have some cake or champagne or something like that for me in the courtyard, and I thought, "Eh, they might ask me to say something," so I memorized Bilbo's speech from the "A Long-Expected Party" and gave it—

ZIERLER: [laughs]

EILER: —extemporaneously. [laughs]

ZIERLER: That works.

EILER: It was like, what do you want to hear from me? You guys already know me. Like—"Thanks? I guess? Except you didn't do it." I don't know. [laughs]

ZIERLER: Your research group, the grad students and postdocs, are they on pins and needles? Does their future really get impacted about your tenure decision?

EILER: That's a good question. I don't really know how cued into that they were.

ZIERLER: If it's a vote up or out kind of a situation, and you have a second-year grad student, and you heaven forbid are denied tenure and you're out in a year—

EILER: Yeah, that person is in big trouble.

ZIERLER: Right? They are. They probably are more keyed into this than they might let on.

EILER: We never discussed it. Some of the first people to enter my group as an assistant professor were quite senior postdocs, and like ten-years-older-than-me senior. How they ended up in that position, that's their own shaggy-dog story, and those relationships were unusual in terms of the power dynamic and age difference and things like that, but they were also very successful. It was a very good way to have done it. That's another thing I would recommend to a young assistant professor—find some peculiar skilled somewhat older postdoc and get them in your lab, and then hold on tight, because that relationship will be fraught. [laughs]

ZIERLER: There's wisdom there. There's life lessons.

EILER: There's wisdom there. There's conflict that's cooked into that, because there's a level of jealousy, and who's in charge, and who isn't in charge and so forth, but there's wisdom there, and you can draw on that. They can benefit from the opportunity you give them. You can definitely benefit from having them there.

ZIERLER: This idea, this metaphor, of all of your concern about being tactical and about publishing this paper so that you best position yourself, once all of that goes away and you get the good news, and now you have this, "How do I become this leader? Now I am unfettered. No one is standing in between me and achieving that," what's your game plan? How do you build that?

EILER: If you had asked me the year before I was tenured, "How would you characterize your papers and talks you give at conferences?" I would have said the cool thing about them is every one of them is different from every other one. I never gave the same talk twice, anywhere. That is, in a sort of low-stakes way, an intellectual virtue in that it shows you have breadth. You're able to engage with many different questions. But where are you going? Where is this all headed? Soon after tenure, it solidified in my mind. I identified a target that I was going to pursue that felt to me like a singular goal. It was really the work of a lifetime to do it. The appeal to me is that the direction I wanted to go, that I identified to move in, was effectively infinite. It's like everybody has been sailing around close to shore, and you turn around and you go, "The ocean is kind of big. I'm just going to go. I'm going to go and go and go, and who knows where this all ends. Probably it never ends." The decision to go also then coincided with the decision to be more strategic, to think in terms of multiyear arcs of accomplishment that would build on one another. Imagine like, okay, I've got my ship, I've got to sail into the ocean, I have no idea where the other side is. How far will I go on this first journey? Well, maybe I turn around after I've gone six months and I come back and refit, and then I get a better ship, and then I go out enough I can go a year.

ZIERLER: Tenure allows you to do that.

EILER: Tenure allows you to do that. So I very much switched my mindset from, I'm a person who is moving around and showing that I can—that's one thing—to a mindset that what I'm attempting to do sounds so crazy that I'm not even going to tell people what I'm doing. I'm only going to tell them what they need to know, which is the thing that is happening right now. The crew on the ship, everybody now in my field is now the crew on my ship. The captain does not tell you, "Oh, we're sailing to the ends of the Earth. And maybe off the edge." No, no. The captain says, "Pretty sure there's an island. It's two months that way. It's gonna be good. We'll go there, we'll come back." Great. Except we go there, and now actually there's kind of a better island, and it's another couple months out. This immediately became my mindset, that we're going to do this thing in stages.

I also began developing and frankly manipulating my relationship with the instrument manufacturers. In the old days, you would hire in these very gifted engineers and they would build things for you. Today, you can do a little of that—it's okay for little marginal things—it's not a way to run a lab. It's just too expensive, too slow. You need a whole team, and you need to convince them that they're going to make money doing this. Somehow I had to get a King Whoever of Spain to underwrite my journey and my ship. How do you trick them into doing that? I'm not doing it for their reasons. I couldn't care less if they make any money. But I need them to think that they're going to make money. And if they're going to think they're going to make money, then they need to make a little money. How do I manipulate that? How do I manage that? That also suddenly became part of my thinking. Really it was a marked change both in what I was trying to do, how I was trying to do it, what were the time scales involved, who did I think of as a partner in this endeavor. It was a very radical shift.

The Quest to See Every Isotopic Form

ZIERLER: You're articulating the journey. What are the science objectives? What are the questions that are propelling this journey?

EILER: The true goal, and the one that I can't really articulate to people without having them judge it too harshly, is to create the capacity to both observe and interpret and ultimately use for applied purposes the study of all the isotopic varieties of nature, which are almost infinite in extent, starting from almost nothing, from the capacity to observe one or two isotopic forms of carbon dioxide. That is really the bedrock of almost all of isotope geochemistry at that moment. How do I turn that into the ability to see every isotopic form of all molecules known to science? It's insane. But that's really what I'm trying to do.

Stated that way, it has no specific scientific goal. But if you went back and asked Sanger, who first sequenced DNA strands, "For what purpose? Why?"—well, he knew there would be purposes. I also knew, there are going to be purposes to this, and they will be good purposes. Then in the near term I need to identify a goal that's a few years away and is good, and is good enough, to motivate the coming step. That ended up being carbonate thermometry, so measuring the temperatures of formation of carbonate minerals using isotopic structure; that is, the organization at molecular scales of isotopes. That was the first goal that I identified and went after, and it really framed the whole first five years or so of my work in that area. But I always knew, we're going to do that, we're going to do it for five years, but while we're doing that, we're getting ready for what comes next, which will be a completely different problem.

ZIERLER: Would Urey have known that there were these infinite number of combinations, or when does that become apparent in the field?

EILER: His first paper about the chemistry of isotopes really bottom-line is about the propensity of heavy rare isotopes to stick to each other. It's about this question of where in molecules do the rare isotopes want to be in relation to each other. He knew that. He only thought about it in the context of very small, simple molecules, but who's to say what he imagined? If you had said, "Oh, well, how do you think this works in like a steroidal compound with 50 atoms in it?" he would have just been like, "The same, but super-super-super complicated." He addresses this in a paper he wrote in 1947 or so, where he talks about the application of isotope chemistry to the Earth. He has a throwaway line in it where he mentions the multiple substitution of rare isotopes into the carbon dioxide molecule. He says, "This is kind of interesting, but the effect is so small, and the species involved is so rare, it will never be measured."

I started with it because it's the most abundant thing you can measure that's like this. All the other ones are, in general, much more rare, and it never occurred to him he could directly measure big molecules. That was just a physical impossibility to him. So, it's hard to say. He would have understood what I was doing, for sure. In fact, of all of the people in history who I would have been willing to tell my actual goal, I would have told him. I would have told one or two other people. I might have told Sam Epstein, one or two other folks. I wouldn't have told much of anybody else, because it required three or four big five-year jumps to get where I wanted to go, and a lot of the details were unclear to me how they would be solved.

ZIERLER: The quest to be able to identify all of these different permutations, obviously the emphasis is going to be on technical capacity and instrumentation, but the process of getting there—stamp collecting is a term that is derisive in science, right?

EILER: Yeah, of course, and it should be.

ZIERLER: Is it inevitably stamp collecting even though that's not your purpose?

EILER: It would be called stamp collecting if you did it without two other things being glued to it the whole time. One of them is an understanding of the fundamental chemical and physical properties of these things that you are measuring. Do you understand the chemical physics of these things, these molecules, that have these rare substitutions in them? If you understand their chemical physics, now you know what their behavior is like in natural or engineered situations, and now it becomes possible to use them as tools for other ends. The second thing that has to be attached to it at all times is a focused application, and because of who I am it has to be in the Earth and planetary sciences so that I know what I'm talking about and can exercise some judgment about what we go after.

Every one of the multiple arcs of development of this problem has unified these three things. There has been an instrument platform that enables a certain kind of measurement, a body of experimentation and chemical physics theory that explains what is currently being measured, and then a specific application that everybody in the community can look at and go, "Yeah, I wish I knew that." Independent. You could not even use the word "isotope"; they will appreciate the scientific deliverable. That was there from the beginning, and has simply shifted and then expanded. Initially, it's on measuring the temperatures of chemical entities that have the carbonate ion in them, which includes like dinosaur teeth, and eggshells, and ancient sediments from the geological record, and rocks from Mars. If you can say a temperature that has been experienced by one of those objects, that opens up all kinds of natural science questions. If I can say, "Four billion years ago, the temperature at this place, on that day, on the surface of Mars was 18 degrees"—well, that actually is a very specific statement, and now a lot of things blossom out of that. What was the climate like, therefore what was the atmosphere like, so what was water doing? Was it habitable? What kinds of chemistry was possible? Lots of things come out of that that are worth discussing.

This is like a chess game. I know I can get to checkmate in 15 moves, because the problem is hard, but to get there, first I've got to take this sucker's knights. Gotta take em. I'm gonna take the knights in these clever five moves. Boom, got ‘em. Now I'm ready to do the next thing. I've got to break this down, major stage by major stage. Each one has its own set of goals. Then at the end, you can turn around and look back and say, "Ahh! We were headed here the whole time!" The here that we're at looks radically different from what was happening in that first stage.

ZIERLER: Even absent these two additional objectives that you put on yourself, even if it was quote-unquote "only" stamp collecting—would anybody have complained if Gregor Mendel was, quote-unquote "only" doing—I mean, nobody had done it before! Isn't there an inherent value in cataloguing because it needs to be catalogued, even if it's only for other people to do what you also wanted to do with these things?

EILER: Somebody would have liked what I was doing, but the community as a whole would not have respected it in the short term. One of the things that I had to manage—I never cared what anybody thought about me, at all. Like I couldn't care—to this day, I don't care whether anybody thinks what I'm doing is good or not. But I have a logistical problem to solve. I need a certain level of positive attention so that I can get the resources. It's expensive. It's just expensive to do all of this stuff. I don't think it's unreasonably expensive. People waste money on a million different things, so why not waste money on me? But in order to convince people, there needs to be a compelling case that is relatable. Every part of it needs to be true. It needs to be transparent. No puffery, no fakery, no trying to pull the wool over people's eyes. It has to all be transparently true. But in my mindset, it's a limited subset of what we're doing. It's just a step. The goal is at the top of the staircase. This is a step. Nobody knows where we're going. They don't know that we're going to the top of the stairs. They just know we're going to get up on this step. Great. We did it. Now what? You can stay on the step if you want. I'm going to the next step, and maybe other people come with me on that next step.

ZIERLER: Last question for today. In order for you to get there, you have to get the instrumentation to a place where it isn't already. How do you operationalize that? What are your relationships with manufacturers, with engineers? You need bespoke instrumentation. How do you make that happen?

EILER: In the end, I needed to kind of take over at least a part of the design and use of a multi-billion-dollar-a-year industry of life science mass spectrometry that had no connection to natural abundance isotope ratio work. How do you get there? How do you make that enormous boat change direction at all? Even if it's just a little change in direction, that's the change in direction you need, because it's so big that it will accomplish a lot for you. That's where I ended up, but to get there, I had to burrow my way through a little side room of that ship—maybe that's not a great extended metaphor [laughs]—but I had to somehow go from deep down in the bowels of that ship, start prodding, start pushing. It's its own half-hour story how that worked. Maybe we do that the next time.

ZIERLER: Why don't we pick up right there?

EILER: Okay, we'll pick up right there!

ZIERLER: Perfect.

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, December 1, 2023. It is great to be back once again with Professor John Eiler. John, as always, it is great to be with you. Thank you so much.

EILER: Thanks for spending time with me, David.

Tactics and Strategy in Research

ZIERLER: Today we're going to pick up on this great extended metaphor you used. You're deep in the ship. [laughs] You're boring a side-hole because you've got to get there to create the instrumentation. We engaged on a great level of detail, tactically, what you needed to do, but maybe let's step back a second and now talk strategy. What was the science? What did you need this instrumentation to do in order to fulfill these science objectives?

EILER: Right. First of all, what are the targets? What are the things that we're trying to observe? They're rare forms of molecules that contain rare isotopes in any number of substitutions where every additional substitution after the first makes it more and more rare. There's a sort of bottomless well of sensitivity that we are seeking. The more sensitivity we have, the larger the number of substitutions that we will be able to observe, the greater we can explore isotopic diversity.

ZIERLER: What's the bottom threshold of "rare"?

EILER: The rarest of the rare?

ZIERLER: No, I'm sorry, the top threshold.

EILER: Many of the heavier elements—chlorine, iron, and so forth—they actually have sub-equal abundances of their various isotopes, and it's a misnomer to think of one isotope as being rare and another as being common. Lithium, also, and boron, have relatively common rare isotopes of order tens of percent. Some of these are easy targets. Unfortunately from this standpoint, the standpoint of what you need from sensitivity, almost all of chemistry is organic, organic chemistry is basically all about carbon and hydrogen—with some, as bit players, oxygen, sulfur, nitrogen—and for all of those elements the rare isotopes are truly rare. They're of order a percent. Then for hydrogen, a fraction of a tenth of a percent, some part in 10,000, so they're really rare. Then every additional substitution after the first, you obviously need—it's to that power. If I have a one percent change of a rare isotope being present and I want there to be three of them, that's a part per million. It really runs away from you quickly. There's a counterbalancing factor in organic chemistry that organic chemistry also involves repeated use of the same element over and over again in different structural positions. Every time that an element is reused in a molecule or is present multiple times, that's an additional bite at the apple. That's another chance that the rare isotope will be present.

ZIERLER: What does "used" here mean? That seems like there's an activity going on as opposed to like the existence of—

EILER: That's right, I'm using jargon here. Basically when a rare isotope is present, it changes the physical and chemical properties of the molecule, so it creates diversity in behavior, diversity in signature. I don't really know why I use the word "used." But when the rare isotope has substituted for the common isotope, yeah. Okay, so one thing we need is sensitivity. We need tremendous sensitivity. We also need the capacity to observe molecules in their native state. We don't want to destroy them. Because really, we're studying—this is a subtle point—we're not studying the atoms; we're studying the bonds. We're studying the bonds between rare isotopes. We only are interested in making a measurement if we know where the rare isotopes are in the molecule. We only know that if the molecule is intact. We have to be able to apply whatever this technology will be to very rare things, so it has to be sensitive, and it has to be applicable to basically any molecule of interest to me. It can't be applicable only to a few molecules.

ZIERLER: You have a set idea of what's interesting?

EILER: In terms of chemistry?

ZIERLER: Yeah.

EILER: Everything. The idea is, we are going to create a toolkit that will be of use irrespective of what kinds of questions about laboratory or natural science motivate you. This is a general thing. It's sort of like the first person to invent a telescope, you don't ask them what star they're looking for. This is for everything. This is to look at absolutely everybody. We just want our telescope to work right.

ZIERLER: You're structuring this to be an enabling technology out of the gate?

EILER: Correct. One of the things that will be required to make that technology useful, to make it be able to develop over time with repeated investments of time and money and energy and innovation, it has to be perceived to be useful as you are developing it. The first telescope, you can probably sit in your basement with a little grinding pad and a piece of glass, and you worry away at it for a few weeks, and then you give it a try and see if it works. We can't do this. This is such a complicated undertaking that it has to unfold over many years, over many steps of innovation, and you will run out of steam if you don't prove to people that it has applied use as you go. There has to be little way stations of demonstrated applicability on the way from nothing to everything.

ZIERLER: Running out of steam means money, grad students?

EILER: All of it, yes. Interest, promotion, money, students, opportunities to write papers, so on and so forth. Recruitment of other professors and other research scientists to also be interested in this. This sort of activity, it's not really something that one person completely owns. It doesn't matter how successful you are at it. There's too much to be done. You have to get people interested so that a community comes along on this journey with you. They will do some of the technical innovations themselves, although for the most part my experience has been everybody who gets interested, they're interested in what can be done now. They're not that interested in what will come next that seems like a radical departure from what is being done now. In general, the community of people who I recruit to come along, they are interested in tactical innovations, making the immediately possible thing work a little bit better, or on one or two new molecules that hadn't been studied yet. I'm trying to get the entire activity to be substantial enough that I can then use it as a springboard for the next big innovation. We're kind of playing different games, but I need there to be people who come along with me. They will only come along with me if they're benefiting, and they're only benefiting if there's applicability to their areas of science.

ZIERLER: This applies to colleagues and students?

EILER: Absolutely. As far as I'm concerned, it's all the same thing. Some of them are people who were students and now they're colleagues who are working in their own labs. Those people tend to be, relatively speaking, quite ambitious. They are also pushing at this more strategic level into new things. There's other people who they just have kind of an incidental cross-section with me, I happen to be working in an area that interests them, and they see an applicability to problems that they want to solve, and so they adopt the technologies, they get involved. They never really have the intention of participating in major moves forward, but they still need to be there. If they're not there, there's no community. There's no way to take a measurement capability and use it for discovery, explication of complicated problems, to do things that get people excited.

Innovation and Momentum

ZIERLER: Is there an elevator pitch from you, or is it more like people are seeing what you're doing and they either get it or they don't?

EILER: I learned early on, the only way you recruit people to do something that is fundamentally driven by technology innovation—[laughs] it sounds like kind of a funny way to put it—you have to make them sort of jealous. They have to look at something you accomplished scientifically where the word "mass spectrometer" could not be used, the word "isotope" might not be used—you achieved a science deliverable that they wish they could do, and they look and see, how was that done? Oh, there's a new machine. There's a new measurement concept. I guess I'd better do that. I guess I'd better get involved in that. Maybe they will look at the first paper that we did and say, "I'll bet I could do better." Great, do better. I'm moving on. You stay here and do better, like make this be better. There is no counterflow of jealousy about this. I don't particularly get upset when people like build a copy of a machine or try to race to write a paper first or something. Great, do it. This is all happening in a much bigger context from my perspective. I'm just trying to get them enmeshed in the whole activity. Some people will do that in a way that's very positive, like, "Oh, I just want to help, and I'll send you some samples, and I'll visit, and I'll learn." Other people will do it in a more negative way, like, "I'm going to compete. I'm going to try and get a grant you didn't get, or build a copy of a machine" or whatever. Doesn't matter. In the end, they are all doing the same thing; they are getting on this boat with me, like it or not, and they are helping sail the boat. That's a super important part of making this work.

From the beginning—what is the technology problem? How do I end up in this partnership with Thermo Fisher and they end up very involved with Caltech? It's because I'm making a mental checklist of all of the things that need to be true for the measurement to be physically possible. If you can't make the measurement, then none of this is even worth talking about. The first one I mentioned is sensitivity. The second one is applicability across many different kinds of molecules. The third is the trickiest one. You need to be able to structurally localize where isotopes are in a molecule. Otherwise, you're missing out on a lot of the information that you want. You want to be able to make statements that a rare isotope is in this atomic site, not that one, this end of a molecule and not the other end of the molecule.

So, I'm looking around. There are all these different ways that this could potentially be done. I'm not the first person to have these thoughts. People have explored different ways you can physically interact with molecules that potentially provide observations of this sort. You can do it by nuclear magnetic resonance spectroscopy. You can do it by infrared spectroscopy. You can do rotational spectroscopy. You can do all kinds of things like this. When you really start to push the practicalities of them, though, you quickly realize that they are gonna hit the wall really fast. They might sound great at the beginning, but then—for example, nuclear magnet resonance spectroscopy seems like the obvious choice if you know a lot about all the different physical ways that people interact with molecules and observe their structures. It's isotope-specific. It's intrinsically structural. It tells you about individual sites. It seems like a great idea. But you need a gram of pure material, and it doesn't have the sensitivity to see multiple substitutions, not really. Multiple substitutions, they are 99-plus percent of all the diversity, and in natural materials, you never have a gram of a pure anything. You're always working with complex mixtures of all kinds of compounds, and usually in very small amounts. So it sounds great, and there are groups that are invested in that sort of thing, but it's never going to be the breakthrough technology that just enables the whole thing.

You can run down the list of all the different physical and chemical ways observing molecules and you end up concluding, I would say unavoidably, that it must be some form of mass spectroscopy that gets this done. The main reason is mass spectroscopy is so generalizable. If you can put a charge on a molecule, you can observe it and manipulate it. And there's a century of prior experience with various ways of breaking ionized molecules in systematic fashion so that you get to observe chunks of them separately. That gives us our spatial information. And, they are tremendously sensitive. At the extremes, like an accelerator mass spectrometer that is used for carbon-14 dating, they routinely observe relative abundances of 10-15. That's great. If that's your floor and that's the best you're ever going to do, that's good enough. You're able to do a tremendous, tremendous amount with access to 10-12, 10-15, this sort of level of abundance that is part of your potentially observable universe.

Mass spectroscopy has a huge number of advantages. Its main disadvantages are its ability to observe location within molecules is very situational, imperfect. That will be just a remaining problem that we will just always be struggling with. That's the technical challenge for individual measurements. Yes, I can break molecules up into pieces, and by observing those pieces, I come up with a kind of map of where the isotopes were living in the molecule, but I'm never really doing it perfectly, only in special cases. I'm always sort of limited in this way. That's a good tradeoff. The bigger problem is, at the outset of this activity, in the early to mid 2000s, you look around at all the work of mass spectrometry, everything that exists, and there is no instrument that has the mass resolution to separate different forms of a molecule or different forms of fragments of molecules that have the same cardinal mass but for different reasons. Like if I have a molecule that has let's say ethane—so I have two carbons and six hydrogens—it could have a one extra cardinal mass relative to the normal molecule because it has a carbon-13 atom in it, or it could have that plus-one cardinal mess because it has a deuterium atom in it, a rare isotope of hydrogen. Either one imparts a plus-one atomic mass shift. How do I tell those two states apart? The carbon-13 and the deuterium, they're both one AMU, one atomic mass unit higher, but they're not exactly one AMU higher. This is the mass defect. That is, every nuclide is unique in its mass if you measure it precisely enough, so you have to have the precision to separate the masses of interest.

Then because we wish to do this for all kinds of molecules and their fragments, in practice there are molecules that weigh thousands and thousands of Daltons. We're never going to do those directly, at least with nothing that I've thought of or seen. Most of the power, though, in mass spectrometry, most of the information that we want, is recorded at masses of up to a few hundred atomic mass units. That's really the playing field we need to be able to master. If I take a common conventional mass spectrometer that is used for isotope ratio measurements, for the first almost century of isotope studies, they have mass resolutions that are about one part in a few hundred. All the ones that can study molecules, which is what we're interested in, these are the kinds of mass resolutions that they have. There are more specialized mass spectrometers that have higher resolutions, but none of them are engineered for isotope ratio measurements, and they would be poor at them. So, one part in a few hundred—well, what do I actually need? To separate the near-adjacent masses for organic molecules, masses of a few hundred atomic mass units, you need like close to a million. Maybe half a million. You are orders of magnitude away. So, no instrument exists on the playing field that is really suitable for this. We're going to have to invent something.

The ultimate solution to this was a marriage of the sample handling and methodological approaches of isotope chemistry with the tremendous power of Fourier transform mass spectrometry that is used in organic chemistry for molecular identification. That's the ultimate solution that we got to. We didn't go there in one step, because it's a tremendous investment, there's a lot of unknowns in whether that combination will work, and at the beginning it wasn't clear there was any purpose to it at all. We hadn't yet engaged in this activity of showing the utility of the measurement in simple molecules and building up a community, building up a body of work. To get there, we actually had to jump several stepping stones. The first stepping stone was to create a mass spectrometer that looks from the outside just like every other low mass resolution isotope ratio mass spectrometer you've ever seen, but it has a more sensitive detector in it, in the appropriate position to study the multiply rare isotope substituted form of carbon dioxide. That was the first step of the whole process.

To do it, beginning with no relationship with any funding agency in this area or any company, how do you do this? Back in the 1940s or 1950s, you would hire engineers to build machines for you. Charles McKinney was the person who did this for the first generation of isotope geochemists at Caltech. Today, this is not a good idea. There are people who do it; they're not helping themselves. They're not going to create a community. The machines that work at a high level, they have integrated circuits. How do I make integrated circuits? There's all kinds of reasons why this is going to be very slow. And you'll never translate it to other people's labs. What am I supposed to do, become a company that manufactures mass spectrometers? It's ridiculous. You have to somehow convince an existing company to do what you want. The only way you'll do this is if there's a market. There's only a market if there are scientists who want to do what you're doing.

ZIERLER: [laughs]

EILER: How do I get the horse in front of the cart? It just seems impossible! The solution—in the end, it worked, but it had to be one little step at a time. I began by taking a mass spectrometer that was already in my basement, and I kind of hacked it both physically and in terms of methodology to make a very, very crude measurement of the multiply substituted form of carbon dioxide from air. I used this to go to the National Science Foundation and say, look, these species exist! Of course. They must. Everybody who thinks about it understands they must exist. I have just observed it in air, and it is present in a non-random proportion. Meaning there's some kind of chemistry or physics that it is recording. This is a new thing that can be observed. CO2 in air is important, because of greenhouse warming and all the rest of it. So, give me a little bit of money to go and bring to a company and convince them to build me a slightly modified instrument that will do that measurement properly. They agreed, and gave me the money.

The very first step—I'm just a customer. I go to several different companies and ask them whether they're interested in this. I could have potentially ended up working with any number of them, but only Thermo Fisher agreed to do the project. Everybody else said, "Why? This is going to be difficult. It's not going to work, probably. It's just not worth it." They all turned me down. Thermo Fisher said, "Sure, we'll do it." I asked them to do two things. I wanted them to improve the mass resolution by a factor of just a few. I want to get an improvement of a factor of a thousand or more. How do you get to a factor of a thousand? Start with like two, then we'll go from there. Let's improve the mass resolution a little so I start to nibble away at all the problems of isolating the ion beams of interest, and give me a detector on the back end of the instrument that is orders of magnitude more sensitive than the best that we have on isotope ratio mass specs that are common sorts of instrument.

They said, "Sure, we'll do that," and we signed a contract. And then they didn't do either one. They basically descoped the thing. They're busy people. They don't want to spend any more money than they have to. So my first decision in the relationship-building with them was, what do I do when what they ship to me is not what I asked for? They shipped me something that was—good enough, it turned out. They gave me a somewhat more sensitive detector in the right position so I didn't have to do a bunch of nonsense in my methodology to see all the different ion beams, but it was not what I asked for. It wasn't a very, very sensitive detector. And they did nothing about the mass resolution. My response was, I'm going to choose my battles. I'm not going to get in a fight with them about this right now. Because I could maybe win the battle over the contract. Maybe I get back some of that money. To what end? I don't want the money. Money doesn't mean anything to me. I want the instrument. And they didn't build the instrument. They refused. But they built something that I thought, it's just good enough, I may be able to develop a science case that convinces other scientists. Then when I come back them in a year or two years or three years, it's not just me, it's a market, and now they will respond, and they will give me what I actually want, which is the instrument.

So, that's what I did. I started studying carbon dioxide in air, making relatively precise measurements of these multiply substituted rare species. That was sort of interesting. It could have been the only thing I worked on. But then I quickly pivoted to studying CO2 that was released from carbonate minerals. This enabled thermometry, measuring past geological temperatures or biological temperatures, if you have a carbonate mineral from an animal's body, using the thermodynamic controls on the so-called clumping effect, the grouping together of rare isotopes. This was a measurement that, because we could do it on CO2, CO2 was basically the only molecule we could study on this first-generation platform, but the carbonate minerals, they're all through the geological record. They record climate. They record ocean composition. They record things people care about. The study of CO2 and of carbonates, this is the oldest, well-established stable isotope subject in the whole community. Back to the early 1950s, there are papers about this. So it was a huge community already studying the isotopes of these materials in a more conventional way, where they're just counting isotopes in materials and not molecular structures.

I start going and giving talks about this work where I'm measuring temperatures of mineral formation using this clumping effect. It was one of the most surreal experiences of my life, to stand in front of a community of colleagues—at this point, they all kind of know me, because I'm now a tenured professor at Caltech, and they've seen me for a few years, and I know all of them—and I'm talking absolute nonsense. I'm describing to them something—they've never heard of anything like it. They've never seen anything like it. They get the motivation. They've been does this their whole lives, They know, yes, I want to know about isotopes, I want to know about carbonates, I want to know about temperature. But how could I be measuring that with this crazy thing of these very rare molecules with multiple—like, how does this even work?

ZIERLER: "What happened to Eiler?"

EILER: Yeah, "What happened to him?" It was really fascinating! I remember distinctly having this sort of out-of-body experience where I'm giving my talk and there's like data slides and the rest of it, I'm doing my performance, but I'm not paying attention to what I'm saying; I'm watching them. How are they reacting to this? What do they think about this? It was a very powerful thing because I realized that you can use uncertainty or discomfort as a way of really motivating scientists. If you get just a person walking down the street and you say something to them that sounds crazy, they'll probably just be like, "There's a crazy person," and they'll move on. A scientist is not going to do that. They're going to try to figure out what's wrong with you.

ZIERLER: [laughs]

EILER: Are you making some weird mistake, have you misunderstood something, or have you discovered something? Because we always have an antenna out for the new. We always want to see something new, and yet we're also skeptical. So you're never going to get an aha moment where everybody in the room goes, "Oh, a genius has arrived! And of course we'll all do what they say!" No-no-no, you're going to get skepticism. But that won't stop there. They'll get involved. They'll get enmeshed. And it totally worked. This was maybe 2007, something like that. Very quickly, a few people who were these sort of competitive actors—they wanted to like, "Oh, I'll take that, I'll jump out in front of that"—they appeared immediately. Within months, they were giving talks about their attempts to do this sort of thing. They all botched it. It was all just like ridiculous. It was very badly done in a technical sense. But people kept coming back and wanting to see what we were doing.

The most important thing we did is to immediately write a Science paper about the uplift of the South American Andes using the temperature history of the surface. We basically collected a bunch of soils from South America, working with geologist colleagues there, and showed that the surface of the ground in the high Andes had cooled off from near like tropical temperatures—right now it's incredibly cold. Ten million years ago, it was like 30 degrees centigrade. We showed the gradual cooling of the surface which corresponds to its uplift. That's a scientific deliverable, a geology finding, that a whole community of people who don't care about isotopes at all, they don't care about mass spectrometers, suddenly they're motivated to want to study that. They want to be able to do that in Tibet, the biggest plateau in the world. They want to do that in the western U.S. and study tectonics in North America. People want to be able to do this, and they could immediately understand, what if I translate that tool to my problem? Climate history, evolution, global climate change—all these different applications of temperature measurement, they immediately saw there are science deliverables that come from this. We're not going to just watch Eiler and see whether he's losing his mind. Now we're going to start to follow him, and try to replicate this. We're going to try and do it ourselves. That nucleated a community that within maybe two years got pretty big. Maybe 40, 50 labs started trying to do this in a serious way.

ZIERLER: Bigger than even geology labs?

EILER: Yeah, 40 to 50 different Earth and planetary science labs. Some life science people, but mostly it was Earth scientists at first. This also had an interesting resonance with what was going on in Thermo Fisher's mass spectroscopy group. They made a variety of mass spectrometers for people who study isotopes, and the ones who studied molecules—gases and things—they had two basic types of instruments. They had their little cheesy Ford Fusion mass spectrometer, and then they had their Cadillac. The Cadillac is the one they want to sell, because they make more money off it. Everybody looks at these instruments, and they say, "Well, the mass spectrometer doesn't really matter." Because all of these mass spectrometers are very similar to each other, and the high-performance one doesn't really tell you anything that you don't learn from the low-performance one. It would be as if you're driving around, and you have nowhere to go other than to like pick up some takeout at In-And-Out, and no roads to drive on other than like 30 miles an hour; why take your Cadillac? What's the point? You're going to get your cheap char.

They really didn't see a purpose to those, and so their big instrument line was dying out. They were probably going to stop making them soon. Suddenly, 50 different labs order these more expensive instruments that we were using, modified in the way that we had done to make this measurement, so they get to charge an extra premium for that modification. This made a huge difference to them in their business in a very short window of time. It basically revived an entire group within the Thermo Fisher mass spectrometry factory. They like didn't lose their jobs, they got to keep making money, and so forth. Now, we renewed the conversation about technology development with a complete switch in the power dynamic. Now I'm not a customer with a measly couple hundred thousand bucks to give them. Now I'm the person who has motivated this community that is giving them tens of millions of dollars. Which it still isn't very much money, but it was enough to really catch their attention.

So now we design the real project, which is now we're going to make a sector mass spectrometer that is really sophisticated, much more sophisticated than what I proposed to them initially. I pitched to them, now let's make a mass spectrometer that goes not to a few times the normal mass resolution, but to, oh, 50 to 100 times the mass resolution. Let's make the highest mass resolution that a so-called sector mass spectrometer can achieve. A sector mass spectrometer's job is to take ions and separate them in space so they can be collected at different places. We'll come back to, well, what else would you do? We'll come back to what else you could do. That's what a sector mass spectrometer does, and it does that by passing the ions through magnetic fields. So, let's have the best version of that that we could make. Instead of one special collector in our collector array where we count the ions, let's have a bunch of special collectors, and let's let them move so we can change our minds from day to day about which molecule we're studying. That is a machine that now the commercial name for it is the Ultra, and it's just an enormous thing compared to anything they had ever built, quite sophisticated. They drew in technologies from their plasma mass spectrometers that they used for studying isotopes of rare metals, their thermal ionization mass spectrometers that are also used for studying rare metals. They drew in technologies from different sorts of platforms and created a hybrid just for this purpose, and they did it to my specifications.

This is then an interesting point. They built this thing and sent the prototype to me, but I knew, this is not the end. I'm going to work on this thing—and I'll explain what it was for, in a minute, exactly what problems it was designed for—but I knew this is not the end of the process. We're going to build on this as soon as it's done. How will I go back to them and get them to do this yet again? There are limits to their patience with new technology projects. My sense was they're still interacting with me like a customer—like a super-customer, but still a customer. How else might they interact with me? What if I patented this instrument? You might think, how can you—? And this was their response initially—how could I patent a thing that they built? Well, that's how intellectual property works! If it was my idea and I said it first, I patented it.

So, I patented it. And they were furious. Their initial reaction—I mean, Thermo Fisher, it's one of the biggest companies in the world—how could this punk patent a thing that they built in their factory, that they consider themselves the masters of? Well, that's how intellectual property works, and I did it. If you don't like it—their initial reaction was, it won't stick. No one will ever award it. Well, it was awarded. I was awarded that patent. So now, they have a big investment—they're making something big, they have a whole customer base, it's a good business, and they don't own it. They don't own the intellectual property of it. I'm not in a position to compete with them. I can't go build one of these machines. But they're uncomfortable. How do you respond to being angry and uncomfortable like this?

ZIERLER: Don't build them?

EILER: Yeah, so their initial reaction was to want to pull away from me, but that's not going to be the long-term reaction. In the end, they're in the business of making money. How are they going to make money? Build better machines and sell them. I'm presenting them with ideas that clearly make markets. This has value to them that is more than whatever money I would spend to pay them for my one instrument. So we eventually come back and have a sort of reconciliation where we reach an agreement—that I will work with them, instead of adjacent to them, against them maybe—and in exchange they will basically keep me in the loop with instrument design projects. That helps them and it helps me. And, they'll basically give me machines, sometimes for free, sometimes super cheap. They supercharge the technology development in my lab, and I supercharge the technology development in their mass spectrometry group. It is a mutually beneficial thing. But the only way that it could be created was through conflict. If I had just gone to them and said, "Well, little old me, please, please? I promise you I'll have another good idea tomorrow"—this isn't going to work. And it wasn't working. They needed to somehow be, I don't know, given a shake, kicked under the kneecap, something, to get their attention.

ZIERLER: Who helped you put the patent together?

EILER: Our IP office people did. Absolutely. It's not that complicated. I write a few-page document and say, "Hey, there should be a mass spectrometer and it should work like this." Then that gets submitted. They help turn it into legal language. Then they do all the fighting and the money expenditures to defend the patent. Then a few years later it gets awarded.

Technology Development and Intellectual Property

ZIERLER: Does Caltech get a cut of all of these machines that are sold?

EILER: Ehhhhh—in the end, the basis of the agreement that solidified the long-term relationship and sent a bunch of machines to Caltech was that they would be co-owners of it. We ceded that to them in exchange for basically having a close working relationship in perpetuity. If you're interested in getting money out of them, maybe you go for a different deal, but at this point this is small-ball money. The sector mass spectrometers for scientists who study isotopes, tens of millions of dollars a year is the whole market. This isn't really enough. This is not going to be of interest for getting into a huge fight over it to get one little slice. It's not really about the money. I don't think it was even really about the money for them. I don't believe that they thought we were going to somehow steal money from them using this IP agreement. They just didn't like the idea of a person outside of their factory owning the concept of a machine that they were building and selling. They couldn't tolerate it. The solution was obvious—bring me under the umbrella so that now the ideas that I come up with are our ideas, including them, and they are automatically co-owners of them. This totally fixed the relationship, and that was the basis of our moving forward.

ZIERLER: You weren't concerned that some idea would be better built at a different company and you were now tied to Thermo Fisher?

EILER: It's not an exclusive agreement. If I thought there was another company where I could do something better, I could do that. But honestly the scale and complexity of the Thermo Fisher operation, it was always clear—they might not be the perfect ideal solution to every single technology component you could name, but they're going to be good everywhere, and better than everybody in integral. It was the right partnership to cultivate. The next short-term stage, the next few years, was taking this big sophisticated sector mass spectrometer and repeating the experience of the carbonate thermometry arc of community-building. This was centered around methane, understanding the biochemistry, the geochemistry—because it's an important energy resource, it's a greenhouse gas—so building up an interest in using isotopic structure in the study of methane as your sort of use case that draws interest to this new generation of big instruments. In a way it's just the same story as the carbonate story. It took a little longer to unfold because the technologies involved were more expensive and bigger. Fewer labs were able to invest in it, in a short timeframe. But the line quickly became profitable, and they continue to sell a bunch of these things.

The next stage was, okay, we've pushed things a long way, and now there's mass spectrometers that do all kinds of things that nobody really imagined they could do. You could spend your whole career using just those instruments to study methane and gases like it, and carbon dioxide, and so forth. That would have been the natural pausing point in terms of technology development for me. But I felt like we basically now had just done the proof of concept of the idea of studying isotopic structures of molecules. We hadn't really touched the big problem, which is all the rest of chemistry, things that are not little, simple gases. How do we get this concept that is now proven, with close to a decade of work, to pivot to bigger molecules? This is where the first stage of having private donor investment became quite important. The end result would be adapting Thermo Fisher's Fourier transform mass spectrometry instruments to this purpose, but there was an intervening step that was pretty important. Charlie Trimble was the person who really made this happen. Charlie Trimble, he is one of a number of—

ZIERLER: GPS pioneers.

EILER: —pioneers, exactly—and he's a close friend of the institute. He really understands what's going on in the Institute and in the Earth sciences and in labs. He has just the right personality type to respond to something like this. There are quite a few people who like to support the sciences. They all have different personal motivations. They all respond to different sorts of things. This was exactly the sort of thing that Charlie would respond to, that there's a bottleneck in technology but a proven concept that you know you want to apply. You absolutely are sure you want to overcome that bottleneck. How do you do it? My first thought was, I need to figure out how to develop some measurement concepts that apply to bigger molecules that are organic, and I need to use an existing instrument. So I went to Thermo Fisher and shopped around in their—it's almost like their old discards or something. It's like the island of misfit toys or something. They have all of these instruments that they continue to build for very specialized reasons.

ZIERLER: Are they local? Are they in Southern California?

EILER: They probably have a branch here or something, because they're everywhere in the world, but this is Bremen, Germany, where their main factory is. They had an instrument called the double-focusing spectrometer that was initially created maybe back in the late 1970s or something, and it only gets used today to measure the concentrations of dioxins in groundwater. That is its only applied purpose. But at the time it was invented, it was a cutting-edge instrument for identifying trace organic molecules of any kind. It was important in life sciences for a little while before it got superseded by other things. The properties that it had that really were good for me is a substantially higher mass resolution. This then reaches the very outer limits of what sector mass spectrometry, separating in space, can do in terms of mass resolution. It allowed me to start working on molecules that had more than one carbon atom in them—hexane, other things like this.

In addition, just due to a technical detail of the way that the instrument was designed and works, I could take families of ion beams at a single cardinal mass, where I don't wish to pick one and ignore all the others. I want to actually see all of them. If I do that with a sort of more normal isotope ratio design mass spectrometer, I would spend one day looking at one, and then I would move all the collectors and then look at another, and then move all the collectors and look at another, and so forth. It would be very slow. This instrument, due to a peculiarity of its ion optic design, it could hop quickly between them. Jump-jump-jump-jump. Jump-jump-jump-jump. Jump-jump-jump-jump. Jump. It let me start playing with measurement design concepts where I would harvest all the information from multiple ion beams at one cardinal mass, then go do the same thing at another cardinal mass, and then stitch them together into a data product that told me about proportions of isotopic substitutions in ways that contributed to each cardinal mass.

The details are like a little boring; we don't need to go into it. The important thing is the way that measurements were being designed and the way that data was being processed, the way that the mass spectrum was being interpreted, elevated, qualitatively, to a higher level. I played around with this for a couple of years and made some measurements of volatile larger hydrocarbons. During that period, I am continuing to interact with Thermo, I'm continuing to visit their factory, and we start having a discussion about—and it's really mutual. I'm looking for a way to get to much higher mass resolutions even though it seems impossible to do with sectors. They are looking at this activity, which now has three stages of technical innovation, and they're all kind of interesting and productive, but they're all in the area of their business that is small. Next to that, in the same factory, is an orders of magnitude bigger business using Fourier transform mass spectrometry in the life sciences. Metabolomics, proteomics, drug quantification, environmental organic chemistry, all of these areas where—

ZIERLER: Biotech is in full swing, at this point?

EILER: Exactly, biotech is in full swing. They're doing orders of magnitude more business there. All of those instruments, they are beautifully designed for mass separation and for mass quantification, which is great for identifying what a molecule is; they are terrible instruments for quantification. They don't measure amount very well at all, and they never have. They're the descendants—the instruments that they're using, they're called Orbitraps, and they are this incredibly ingenious design of a little electrostatic trap that mimics the behavior of devices called ion cyclotron resonance mass spectrometers. The ion cyclotron resonance mass spectrometer is like the most evolved dinosaur of the age of dinosaurs.

ZIERLER: [laughs]

EILER: It's like the Tyrannosaurus Rex compared to the Allosaurus and all of the other ones. It's very evolved, but it's rooted in this incredibly primitive, brutal design. The ion cyclotron resonance instruments have a magnet in them that is enormous and cooled by liquid helium. The whole thing can be the size of a garbage truck. They cost tens of millions of dollars to build and operate. Only national labs and things like that do this, that are really high level. They're really awkward to work with, really a big pain in the butt, but they get to mass resolutions of like millions. That fully opens up the whole problem. And, they've already been integrated with ways of delivering all kinds of organic molecules.

So, they're exactly what I need, except they are terrible at quantification, and I need them to be perfect at quantification. I need them to tell me changes of parts in 10-5 in abundances of very rare things. They don't even think they detect very rare things, okay? And the relative heights of their peaks are like [grinding sound] up and down, and up and down, and up and down. It seems totally ludicrous that this could ever work. But they would love me to try, because if it worked, now maybe my ability to introduce innovations that bring in new uses, build markets—that comes in contact with the place where they actually make money. So we agree mutually—and at this point nobody needs to argue about who owns the idea, because now I'm under the umbrella of this agreement—now we're going to try to adapt these instruments, their little electrostatic version, which as a business model kicks the crap out of the giant magnets. It's just this little teeny device. It's fully patented and protected. No other company in the world can make this thing. It's not quite as good as the giant garbage truck-sized magnets, but it's good enough, and anybody can use them. They're fully automated. They're integrated with all kinds of sophisticated platforms. They are amazing devices. The guy who invented them is a guy named Alexander Makarov, and if he doesn't get the Nobel Prize, nobody should get a Nobel Prize for mass spectrometry ever again. He is just a brilliant guy, and a real sweet guy as well.

ZIERLER: Where is he?

EILER: He's in Bremen. Basically Thermo Fisher has sort of created—[laughs] I don't know if you ever saw the movie Slaughterhouse-Five?

ZIERLER: Oh, yeah.

EILER: Awesome movie. You know the little dome he lives in in Tralfamadore?

ZIERLER: Yeah, yeah.

EILER: That's what they built for this guy!

ZIERLER: [laughs]

EILER: Bremen is kind of a cute, medium-sized town. It's kind of in the middle of nowhere. Their factory isn't that big of a community activity. They have this brilliant guy who can invent a thing that's like a little curved piece of metal that's just the right shape, and it does what it took decades of innovation to make these giant magnets do. He's just a genius. So they have created a little geodesic-land playland for him where he gets to innovate things, propose new variants on it, and so forth. They're just making money in the life sciences off of this. He's kind of a rockstar now in life science mass spectrometry because his invention is at the heart of all the high-performance instruments, like proteomics and all the rest of it.

They put us in the room together, and we just start talking about how we are going to adapt these instruments to this purpose. I went and spent a month there just playing around. Honestly, it sounds insane, but the basic solution to the problem I figured out in a couple of hours. It was so obvious—when you sit in front of these machines and use them in new ways, don't use them the way they've always been using them. Use them the way an isotope ratio measurement person would use them. Control. Standardization. Long integration. They're used to the idea that a molecule flies by and you sort of glance out the window as you drive by. No, nail that thing to the ground. Stare at it for an hour. Now we understand what we are looking at. Integration. Control. Regulation. They had never used these machines this way. It's just settings. Once you understand how the thing works, you can just type in the appropriate settings, go away to lunch, and you come back, and boom, you see, oh, this thing actually works beautifully. You can measure isotope ratios of whatever you want, to small fractions of a percent. It's exactly what we wanted it to be. That experience, first of all it was a kind of surreal experience in a number of ways. I had Thanksgiving in Germany for the first time, by myself, while I'm there, so I'm like trying to convince a restaurant to feed me a thing that is like a roasted turkey, and they came up with like a goose. Like, "Here's a goose."

ZIERLER: [laughs]

EILER: Also, I had a horrible injury the entire time I was there. Before the pandemic, I was really into historical fencing, and I even taught in a club on campus and stuff for a while. I would go to tournaments and fight in tournaments. It's sort of like fencing in the Olympics, except the objects you are fencing with are the weight of a sword, like a sword you see in Game of Thrones or something, and you can wrestle. So, everybody gets injured. People blow out their ACLs and all this crazy stuff happens. I had a terrible fall in a wrestling exchange at a tournament right before I went to Germany to do this, and I fractured my scapula right down the middle. My scapula went crack, like that. I went to the doctor with it, and they misdiagnosed it. They were like, "Eh, you're"—they thought it was a dislocation. They said, "I don't see it's dislocated. You're probably fine. Just go to Germany. It's not a big deal. But try to rehab it while you're there. Do a few pushups or something, just so it doesn't stiffen up." It's actually broken in half, okay? [laughs] So I'm spending a month there doing this lab work, with this like—an arm that should have been in a body cast or something like that. Oh my God, it was really crazy. But that experience, we basically convinced each other that this was going to work, and we just needed to start working on it, refining it, integrating it with the laboratory methods that are needed to deliver analytes of interest to natural science measurements to it. They then shipped one of these machines here. It's the first of these instruments. It's down in the basement now. And off we went.

ZIERLER: What year is this?

EILER: The machine arrives here in 2016, I think.

ZIERLER: How big is the community that you've been building this whole time?

EILER: Okay, so the community—this is another case. This was a slow-burn version of my surreal experience giving talks. The community of people doing carbonate clumping chemistry and now methane clumping chemistry, this is now dozens of labs, several different kinds of applications communities, a whole bunch of different instruments and things. They are having annual meetings. They're having big sessions at international conferences and things. I always show up at these things because half of them are my former students, and they're all doing this thing that came out of our labs here. The talks I start giving around 2014, 2015, start getting really weird. I start by giving talks that are based on this instrument Charlie Trimble bought, where they all show up and they're like, "The methane from bugs is like this," and another one gets up and says, "The climate of the Mesozoic was like that." I get up and say, "Imagine, if you will, I took this random molecule that exists in nature and I measured a hundred isotopic forms of it!" They're all like, "What are you talking about?" The only reason that they allowed me to talk about these things is I invented their field, so like, they have to let me talk—

ZIERLER: [laughs]

EILER: —but I'm only giving these totally demented talks, and I'm doing this for multiple years before anything substantial comes out. I'm sure they thought I had completely lost it. But then about six months after the first of these Orbitrap instruments gets here, we finally have enough data that when I go and give my crazy John talk at the next meeting like this—"Oh, there's data now"—and, "Oh, they actually measured a whole bunch of these things"—suddenly people are noticing, but they don't have any easy way in. The previous two steps, the measurements being made, they didn't understand why I was doing it at first until they heard it a few times, but the physical act of making the measurement, that they could figure out quickly. They were perturbations on styles of mass spectrometry they had seen. They understood what it meant to make a good measurement versus a bad measurement. The basic concept of what was being measured only involved one or two new variables. Now suddenly the whole idea of the mass spectrometry makes no sense to them. It's not a sector. An Orbitrap never separates the ions. You start with a bunch of ions that have different masses. You put them into a cavity. You never separate them. They just live in this cavity together and they rattle around in harmonic orbits, and you kind of listen to them with an antenna. The noise in the antenna, you do a fast Fourier transform on, and then you infer from that the fundamental modes of the packets of ions that are there.

To the audience at these talks I was giving, it just makes no sense at all. The other half of the potential community that ultimately has to get built, they understand the mass spectrometry perfectly well, the life scientists. They've been doing this for years. But the notion that I would look at two peaks in the mass spectrum and say, "Okay, their relative heights changed by one part in 10-4," they'd be like, "Uhhhhhh—the whole—both of them went up and down by a factor of two. How can you even say anything about that?" It's all experimental design and integration and data processing and control. They don't understand any of that. So neither side of this community I now have to make gets it, and it's going to take close to five years before they really get it. I was very patient during this period. I understood what I was doing, and I knew that they couldn't understand it immediately. It was going to have to take two or three generations—not of like full student generations, but of people who come into the lab, learn things, do things, and go back out into the world, and visitors, and me giving talks—it's going to take a few years for people to start to understand what is going on.

The key thing that really draws people in is an applied science deliverable that really matters to them independent of the technology of what you're doing. That really only emerged in a significant way around 2020, when the first generation of students who were working with these devices began studying the isotopic structures of organic molecules from meteorites, and they discovered tremendous isotopic anomalies associated with individual atomic positions in these molecules that informed, in a very new way, our understanding of how the molecules of life, like amino acids, emerge from non-living organic chemistry in the universe. There's many steps between non-life and life, but a necessary first one is, I have to make simple molecules that are essential to metabolism. I have to make amino acids and sugars and things like that. Nature knows how to do this—they're everywhere—but how? We know how to do it in the lab, but do the things we do in the lab bear any relationship to what actually happens in space? And so forth.

This catches the attention of people in a new way. This then cultivates enough interest that Thermo Fisher realizes, okay, now it's time for us to make a bespoke instrument for this community. That just went on the market 12 months ago, something like that, so two years or so after—the first paper like this was published in 2021, actually. All the papers before that were methods papers. We had close to 20 methods papers, or simple applications papers, that people are looking at. They're kind of like, "That's weird," "That's looking better," "That's looking better," "It's looking better." Suddenly, it seems relevant to the science that a big community is doing.

Then, this is just going to come out in a couple of weeks, but I feel like the biggest expansion in interest and awareness will come from a paper that a student in the group, Sarah Zeicher, is publishing—just got accepted and it should come out right before January 1 or so in Science. It's a study of the isotopic structures of organic molecules in the samples returned from the asteroid Ryugu, by the Hayabusa2 mission. The reason this is going to really enhance visibility is first of all, the measurement that she is presenting, it's one of these bizarre clumping measurements that mean something very different and special as compared to normal isotopic measurements. Second, it's on a sample return mission. It's on like the best sample return mission since the lunar program, really. And, it has international involvement, and hundreds of hundreds of scientists involved. It went there mostly to study the organic chemistry. They succeeded in identifying many molecules in the returned samples, but no one was able to analyze anything isotopic in the organic molecules at all. The samples were too small. They were too complicated. They were contaminated in the lab by all the extraction chemistry that was done. It seemed impossible.

Sarah figured out how to use our instruments to both make the measurements everybody did understand but couldn't do, and then to layer on top of them these bizarre multiple substitution indices that we measure, and then she made a first-order discovery. She discovered that there are very exotic multiple substitution enrichments in the organic constituents of this asteroid that we think can only be made in interstellar space chemistry at very, very low temperatures. These organics, most people thought they were condensates from carbon-rich stars, that they formed very hot. She's showing these very abundant common constituents of organics in the interstellar medium, they actually form in the medium, that they are a product probably of radiation-induced chemistry in the interstellar medium. Totally different setting from what people had in mind. It's a discovery. It's a technological tour de force. It's involved in a sample return mission that's the best one in decades. It has all the makings of something that a very broad community will be interested in. And it's only because of these technologies. It's the only way in the world you could have done that. I think it's sort of a good thing that that has been a slow burn, because the interest now has kindled enough that Thermo is selling a bunch of machines that are for this purpose. Then on top of that, there will be a very broad community watching what all of those early adopters do.

Dinosaurs and Outer Space

ZIERLER: You've emphasized the non-terrestrial applications. Did you see that coming? Was that a surprise to you?

EILER: That was totally on purpose. The three major stages of this—the carbonate-focused thing where we're doing like dinosaur body temperatures and ancient climate; the methane, metabolism, natural gas, pollution and all that stuff second phase; the third phase working on prebiotic chemistry and meteorites and things like that—those were conscious choices that were made because the measurements that were enabled by that particular generation of the technology, they spoke to this specific set of measurable molecules that sat at a sweet spot between things that I knew how to talk about and things that a new broad community was interested in. Prior to the carbonate clumping business, I wasn't a climate scientist of any description. I was not a paleontologist. I studied volcanoes. All the dinosaur papers that we wrote and all this other business, that's all me moving into a new community and becoming a member of that community, but it wasn't a community that was too far away. I understood what they were doing, and I knew how to speak to them, and I knew how to work on the problems that interested them, so long as I had a few colleagues who were specialists who could help me out.

It was the same thing with the methane and natural gases. Then again, the meteoritics and prebiotic chemistry, I know enough about meteorites, I know what the planetary scientists are doing. I could catch up quickly. In fact the way that I picked it is I went to an international meeting in Japan and I thought, this might be a good area for me to have be the proof of concept window dressing application for this next stage, which was basically the final stage—getting the concepts and moving them into all of organic chemistry. I thought it might be good but I wasn't sure, so I spent all day at this conference just sitting in a session of scientists talking about the origin of organic matter in space and in meteorites, and on other planets and stuff, and using isotopes. It was totally inspiring to me—how dreadful it was [laughs] intellectually. They had amazing tools, amazing samples, telescopic observations, incredible samples, lunar rocks, all these different things—very exciting, but the community had no basis of interpreting what they measured. They were talking past each other constantly. They were so used to it they didn't even know they were doing it. But as an outsider you could see what they were doing. They would get up and say, "I have a pet idea. These molecules are made in the following way. Now I go and do my fancy measurement, and I see something that doesn't really tell me one way or the other." Basically it wasn't enough information. It didn't constrain the problem. "But I will explain it as being consistent with my idea." It's just confirmation bias after confirmation bias, combined with a kind of polite gentleman's agreement to allow each other to say things that are inconsistent with each other without arguing.

They were doing this all day, and I thought, "Beautiful. I want to enter this community, and I will be the one who says no. That will be my job." It's great, because first of all, that's what every scientist's job is. You encounter an idea, even your own, and you try to disprove it. You try to violate it. You try to break it. But most importantly it means I get to be saying something differently from the way they're saying things, and so they will have to respond, and when they respond they will have to deal with what I'm observing, and it will be different from anything they have ever observed, so it will create a dynamic that will force them to pay attention to address what I'm doing, to get involved. It doesn't have to be that they love it. It just has to be that they respond to it. Other communities, what they needed was, here's a tool, let's help each other use this tool. That's not what this community needed. They needed somebody who came in and kind of pushed over a couple of chairs and said "no" and threw a shoe from the podium, and like that. That's what they needed to get interested. And it's working, I would say. Basically it's working.

ZIERLER: This is real science, what we're enabling now.

EILER: Right.

ZIERLER: Why don't we pick up next time on exactly what the significance of all of this is?

EILER: Yes, what is the significance of all of this. Yes.

ZIERLER: Perfect.

[End of Recording]

ZIERLER: This is This is David Zierler, Director of the Caltech Heritage Project. It is Wednesday, December 13, 2023. It is great to be back for the grand finale with Professor John Eiler. John, thanks again for having me.

EILER: Thanks for being here. I should have brought in my medieval trumpets to blast—

ZIERLER: [laughs]

EILER: —for the last—the final lap!

ZIERLER: I want to pick up on a "ripped from the headlines" story that actually connects to one of the very first topics we engaged on. As you well know, there's a lot of bummed-out people at JPL because of these cuts to Mars Sample Return. One aspect that we didn't talk about—there's a lot of questions right now about how was the narrative lost, or how can we regain the narrative. I want to ask you specifically, because you're not super close to it like a colleague like Ken Farley, but you are one of the future excited users of this stuff when it comes back—the emphasis is in the title itself, Mars Sample Return, it's all about returning the samples. Is part of the problem that this enormously expensive and complex undertaking, the perception is, is it really all about making a bunch of geochemists super excited? Is there an imbalance there? Is there an opportunity for geochemists to say, "Yeah, this is great, but we've got to think bigger. We've got to think about the United States. We've got to think about China"? Is the bigger story that this is really about demonstrating that we can go to another planet and come back. The samples is what's making us do that, but the technology demonstration is the planetary return. We did it first for the Moon; we should do it first for Mars. So I wonder, just speaking for yourself, but where geochemists might be right now, what are your thoughts?

EILER: I think there's two real value propositions to Mars Sample Return, things that really extend beyond a fun Science paper or a couple dozen people at a conference getting excited about something. One of them is what you mentioned, that our technological leadership very broadly defined, thinking about technology more broadly than a specific lander or a capacity to make measurements or put satellites in orbit or whatever—our capacity to run a society that has technological ambition with real reach and vision, that's something—there's are many signposts that say, "You're in such a society," and this is one of them, and it's a big one. You could say it's no different from the OSIRIS-REx mission or Hayabusa2 that are bringing back samples from asteroids. It's way different from those. That's easy. Those are nearby objects. They're tiny. You bring back almost nothing. As an engineering feat, it's exciting if you're a scientist but it's trivial as an engineering feat, relatively speaking. You could say it's like the Moon. The Moon is just the right size and has just the right atmosphere, which is zero, for landing and getting back off, with a rocket.

If we are able to visit and interact with other planetary bodies, you have to be able to do it with an Earthlike body that's near you, and this is the existence proof that we can do that. We've repeatedly demonstrated we can do the first half—landing there. How are we going to prove that you can get back off? The concept that we could have human beings who go to Mars or wander around and do things—whatever value you attach to that, I think most people think of it as a visionary idea—that will never happen if you don't prove that you can take an object and remove it from Mars safely. The idea that everybody who goes to Mars is a one-way trip, this is nihilism. No one is excited by that. We want to be able to visit and return. I think that, as a really high-level vision, you just have to respect that, and if we abandon it, it says we've lost a step in a really big way.

The second is that there are scientific questions that are important with a lowercase "i" and scientist questions that are Important with an uppercase "I" or all caps above the fold. Life on other planets, it's the last of those. It is I would say among a really small number of questions, maybe even unique as a question, in challenging our vision of—what is reality? What is the universe? How are we here? What is happening? What's happening!? Everywhere! This sort of question comes along very, very rarely, where you get to challenge your concept of how the universe works. We have come to think about that in sort of stark physical terms. How big is the universe? How old is the universe? How fast are things in the universe? So on and so forth. How heavy is it? All these sorts of rudimentary questions. How alive is it?--That is an enormous, enormous question, and the only people who say that they wouldn't be impacted by learning that there was life on Mars, they're living an unexamined life, okay? This is a really, really big question, and you don't get very many chances to ask it in a meaningful way.

Most of what we do in the search for life outside of the Earth is basically us honing our skills, burning time, speculating, philosophizing. Almost all of it is like that. This is an opportunity to pick up an object that had something alive in it, or has something alive in it, and bring it home. It's unique. This has never happened, really, where we've had this sort of opportunity. If we abandon that, we're fools, and we just don't understand why it is that human beings do science, why we invest money as societies in doing science. It's just foolish, and there's no excuse for it, really.

ZIERLER: You grew up in the Cold War, and everything you're saying about Mars could have been said in the 1950s about the Moon.

EILER: Except the life part.

ZIERLER: Right, except the life part. But it took the Cold War to make that happen. Are we lacking the urgency of—whether or not we're in a Cold War with China, because they're going to get there if we don't first, however we conceive of that, is there an international security framework that we're lacking here that would make this happen otherwise?

EILER: I'm exactly the wrong age to feel like I have a coherent visceral understanding of what the competition with the Soviets felt like in, say, the mid-1960s, when the runup was intense.

ZIERLER: Too young for that.

EILER: I was born in 1967. But I do remember what that felt like a decade later and so forth. It was intense, but it wasn't more intense, and it wasn't more Manichean in its opposition, this sense of opposed poles, as our relationship with China. I think that's a really polarized relationship right now. In people's minds, it is. In reality, human beings go back and forth every day, and we have businesses and trade and all of these exchanges of people and ideas and objects, and yet in our hearts of hearts we feel this stark difference, and it feels competitive in the same way that the Cold War felt really extremely competitive. What has changed, I think, is a lack of our own coherence. We don't see ourselves as a coherent entity group that can define a collective ambition and go for it. We do ambitious things, but in subgroups. Silicon Valley does this. Biotech does that.

ZIERLER: There's no Manhattan Project. There's no Hoover Dam.

EILER: Yeah, we are not able to look at ourselves and say, "Not only are we different from those people over there who we feel competitive with, but we are also a coherent group ourselves and we can set our own goal. Maybe we'll debate it on the way, but once it's set, off we go, and we will all share in the trials and tribulations and victories of that thing." Other than lunatics who think we didn't actually land on the Moon, I've never met an American who believes we landed on the Moon who wasn't proud of it. Even people who have all kinds of heretical views about international relations today, if you ask them, "When you watch Saving Private Ryan, what do you think about World War II?" they're like, "We did great. We won. It was awesome. We were incredible. America is this incredible thing that can do all of these things." There's this sense of collective—the sharing of a burden, the sharing of a reward, of a victory. I think it's just something we really struggle with right now. In the absence of that, competition doesn't mean anything. The fact that you believe yourself to be in some way different from or that you are afraid of someone on the other side of the fence, if your side of the fence is in disarray, you'll never react, you'll never do something strategic, coherent, and positive in response to that fear.

Let's say someone from China or another country that people view as competitive with us lands on Mars tomorrow, and takes off again. Maybe the discovery of life happens there. How do Americans feel about that? I think if you'd asked that question 40, 50 years ago, a large majority of Americans would have said, "That's a disaster. We lost. We should have been the ones to do that. We are the country that has that ambition. We are the country that has that capacity." Even if it's total arrogance, it's still a coherent vision. I don't think that we have that right now. I think half of the country would say it didn't happen and the other half would say, "Who cares? It doesn't matter." I just think we're too fragmented to understand what we're giving up.

ZIERLER: If the cuts hold, does that put the timeline beyond your active research career?

EILER: I've always had a very circumspect view of the timeline. When I give public talks or mention this subject in papers—Mars Sample Return is a central aiming point for the research that my group does now. And yet, if you scratch the surface, I'm not on a Mars Sample Return team, and I don't want to be.

ZIERLER: You want to get your hands on it.

EILER: Or I can watch somebody who I trained do it, or I can watch somebody who was influenced by somebody who I trained do it. All of that is fine for me. I'm not obsessed with exactly when it occurs, who exactly does it. I want to see the ideas that I created be brought to bear on this problem. If it's me sitting pushing buttons, that could be one thing. If it's a student of mine doing it, that's another thing. It's all fine. So long as that idea can come to fruition, I'm equally satisfied.

Complexity and Chemical Anonymity

ZIERLER: Now we can get back to the narrative and this ties in beautifully. Our last discussion—I want to see how clearly you connect the theme from the first part and to the last part. We started with your vision to increase the sensitivity of the instrumentation and all that that required, and the reconceptualization and the relationship with Thermo Fisher, and your research group and all of that. We have the story of advancing the sensitivity. Then we have all of the paleo—the paleobiology, the paleoclimatology, the paleogeology—and all of the non-terrestrial stuff. How clearly are we connecting these narratives, that the greater the sensitivity, regardless of the motivations, the utility to the stuff that's far away—either far away chronologically in the past, or far away spatially?

EILER: First of all, I would reframe the way that you posed that. The notion that the technological purpose of the things that I've worked on is to increase sensitivity—for a certain value of sensitivity, what you mean by that word, that could be okay, but it's not specific enough to capture what I felt like I was doing. I wanted to bring complexity to the anonymous part of the chemical world. Complexity arises from being able to study many different versions of a given molecule. That's really the heart of what I've done.

ZIERLER: I'm glad I asked the question, because this really deserves explication. In order to uncover that complexity, isn't it all about the sensitivity of the instruments?

EILER: The complexity is recorded by things that are rare, and so of course you must have sensitivity to study them, yes. But the sensitivity is a stepping stone to—the real goal is to take a thing that looks anonymous—you have only your speculations or your assumptions about its origin or its history—and you bring to bear a complexity that resembles, at least qualitatively, say, genomics, and now you take this simple object and suddenly it becomes, to your understanding, very complex, unique, rich in a record of its history. I wanted to be able to bring that capacity to everything. That basically the world of information-rich chemistry would not be limited to the special biological oligomers—DNA, proteins, things like this. It would be a generic thing that you would apply to everything you look at—every mineral, every molecule, every sample. Everywhere you look, you see complexity, uniqueness, a richness of record. That was the vision.

I think how that then relates to problems like the nature of ancient biology, the nature of ancient climate, the search for life on Mars, the study of organic matter in space, these are all problems that I absolutely respect them as individual problems—I wouldn't work on them if I didn't think they were great problems—but really they are subsidiary to this broader goal. They are pursued both because it's intrinsically fun—to study dinosaurs is just fun, and it's interesting. The things you learn enrich your understanding of the world around you, and so that's great. But if you said, "Sorry, John, dinosaurs actually didn't exist. All the fossils are fake," I wouldn't stop. I would be like, "Okay, that's too bad. We're going to do exactly the same thing, exactly the same vision, we don't skip a step, but we're going to hop over to these other things that do exist, and we'll do it to them instead." I'm just ecumenical in what—there's lots of interesting things, and I'll pick the ones that appeal to me the most and that I think are best posed as solvable scientific questions or advanceable scientific questions, but no one of them is actually in charge of my decision-making. The decision-making is completely motivated by this—it's like keeping two thoughts in mind at the same time. One of them is freewheeling and connected to topics of immediate interest to many people. The other is monomaniacal, is focused on something that I'm not aware of anybody who I have worked with who saw it the way that I saw it and wanted to do what I wanted to do with it.

To this day, when I present—I just came from a workshop up in San Francisco where I'm pitching—showing new entrants into this subject matter. "Here's the basic idea, and here's how the instruments work, and here's what you can do with it." Everybody who wants to get into this subject area, they want to get in, in a way that feels comfortable, where the water isn't up above their heads, they're holding onto their stuffed animal that they've had their whole life, and they're comfortable. The line to some kind of payback seems short to them, like they know exactly what they're going to get as a reward for doing this. I'm never thinking about it this way myself; I'm just delivering to them what they need to know so that they'll start to move. The vision has always been, this thing has to become completely universal or it failed. There can be no little alcoves that the light won't shine into.

The crazy thing is—you have to give a caveat, that of course any given target that you set, a certain isotopic form of a certain molecule, some of them are very difficult, some of them are very easy. This is all logistics and technical details. The basic concept, I can hardly believe it but it actually came to fruition. Relatively recently, I felt like it was going to happen, but I don't think anybody else thought that that would happen. I think they thought that I was almost like a crazy person, talking about this. Even as I'm chipping away at it and moving forward the basic ideas and the measurement concepts and the theoretical concepts, no one is mirroring this back to me. Nobody is going and copying it. Other than people in my group who are along for the ride, no one is really trying to do this in parallel, not really. They're doing the version that I was doing several years ago, maybe better even. They're taking this thing that looks productive and focusing in on it. To me, that was just a trivial step that you had to make, but it was never the goal.

ZIERLER: If I can package that neatly, and you can edit accordingly, it's never about the sensitivity—that's a means to get you to the complexity—and you want to get to the complexity because that's where the fun stuff is, and that's where this is going to be an enabling technology for however anybody else wants to use it.

EILER: Yes. It's like taking—the spirit of geology, of being a geologist, is you stand here on the Earth, and it's infinite in its complexity. It's infinite in the depth of its history. Most of it is obscured to you, and you begin picking clues out of the environment, piecing them together, and looking across this landscape, where somebody who doesn't have a skillset would say, "Well, there's mountains, a lot like all the other mountains." No, they're unique. Everything about them is unique. I can learn their unique history, and I can relate it to the unique histories of those mountains over there, and I can put together a narrative story of this space that someone else might feel lost in. Taking that spirit and bringing it to the anonymous chemical world, all these molecules that blow past us.

Here's a way that I put this once at Frosh Camp, when I gave a sort of philosophical-level talk about all this stuff. I told them, there's a just-so story about the death of Julius Caesar, where it says, as Julius Caesar is collapsing and saying "Et tu, Brute" with his very last breath, he exhales a bunch of nitrogen molecules. Those are forever. They mix freely in the atmosphere. Every single breath you take, you are inhaling n molecules exhaled by Julius Caesar when he died. That's sort of a creepy—you should actually then think, "So you're telling me everything that ever died, I'm [laughs] constantly breathing?" Yes, I'm afraid so! But then the next statement I made to them is, well, which one? That particular problem can't be solved with isotopes, but that's the thought. I have all these molecules. They're all anonymous. They've all mixed together. Which one was it? Could I figure that out? I can't actually figure it out for nitrogen. Maybe I could figure it out for like his greasy thumbprint, or the proteins in his bones, or a strand of his hair. Things that have enough chemical complexity in them that their isotopic complexity is functionally infinite, now that's an answerable question. I wanted to make that reality appear. The basic physics that say, oh yeah, of course, it must be true—yeah, I'm sure anybody who wanted to think through the implications in a kind of wild-eyed way, this would have occurred to them. But then you have to make it happen in the real world. You have to be able to actually do it. And then it becomes exciting.

ZIERLER: The quest for complexity, this is not a religious proposition.

EILER: No!

ZIERLER: It's a scientific proposition.

EILER: Absolutely!

ZIERLER: But that requires then some level of intuition or theory. Without the instruments, without the sensitivity, you're not going to know what the complexity is. The question is, is it intuition? What do you know from your previous background that puts you on this monomaniacal or however you want to call it, like, "It's there! And I'm going to find it"?

EILER: It's just a reading of the original literature on the chemistry of isotopes. If you go back and just follow the thread of the first couple dozen papers about the existence and the chemistry of isotopes, you immediately see that there's an understanding that there is a diversity of isotopic forms of molecules. They tended to focus on simple things like methanol and ethane and things like this, but that every combination of isotopes in them, if you could generate that synthetically in the laboratory, would be a version of the molecule that manifests some unique property. They're all unique in their thermodynamics, in their kinetics, and so forth. Physicists and chemists for the first couple decades of the understanding that there is a chemistry of isotopes, they were focused on creating synthetically pure versions of these unique forms of simple molecules that differed in their isotopic content and then studying them. That basic idea—hey, every one of them is unique—take that, translate it into the natural world. None of them are enriched. They're all trace abundances, and yet they must be there. They have to be there. There's no chance that they're not there. What is the world doing to them? How are they being separated, created, destroyed? What are they telling us about their past? It seems to me like a very natural and obvious line of thinking just reading what they did. Then Harold Urey, who is sort of the founding deity of natural abundance isotope geochemistry, he clearly laid out the idea—you go out into nature and you study the proportions of these molecules, and they will read back for you things about history that you would never know otherwise.

ZIERLER: This is to say that if you could take that time machine and go back to Urey and explain this to him, it would make sense?

EILER: He would totally get it, if you could somehow get him to accept, "I can observe anything, at any precision." He would say, "No, you can't." You would say, "Don't argue with me about that. Let's just say that I can. If I can observe any isotopic form of any molecule to any arbitrary precision, then what?" I feel one hundred percent sure he would say, "Well, obviously, then you are unpacking the chemical histories and environmental histories of everything." And most of everything is organic, and so you're mostly doing that with the remains of life and the processes of life. I think for sure that he and his contemporaries would have understood that point. Some of the weightiest things that I read from papers in this era are where he tiptoes up to a practical, applied version of this thought and talks about specific examples for little simple molecules that have unusual isotopic substitution patterns. Just a sentence. Papers back then were very simple in a way. They tended to just have lots of throwaway lines, where you were expected to keep up. But contained in there are statements that are very much in line with what I ended up doing for most of my career. But the end of the sentence is always, "Well, too bad. The effects are too subtle. You'll never measure this. It's just impossible."

All you have to do is say, Look, this isn't religion. They're objects. They exist in nature. They have physical properties. They weigh certain amounts. They can be broken. They can be put back together. You can manipulate them. All you have to do is try. And try for real. Don't try just by saying, like, oh, I have this machine in my basement that was built for a totally different purpose. I wonder if that will do it. Of course it won't. It wasn't built for this. It's like asking if you can use a lawnmower to fly to Mars. It's totally inappropriate. Try for real, and of course you will succeed. In a way, once you have the thought, you're just now trying to reduce it to engineering, is all you're really doing. I always viewed this whole arc as being me reducing their ideas to engineering. I'm sure if they didn't spend time thinking about them, then many of the more granular details wouldn't have passed through their conscious thinking. But if they had thought they could measure these things, they absolutely would have thought this through.

ZIERLER: Now we can pick up where we left off last time. You've done it. You've engineered. You've gotten it to where it is. It's now out there in the world. Here you were explaining [laughs] in the community, the gentlemen's delusional agreement that we're all going to say stuff and recognize that we don't know what's going on, and you come in and you're Professor No. Just, no, you don't care. You're just saying no. Here's where we're going to pick up. What was the response to the no? And ultimately, you don't want to just say no; you want to get everybody to yes. How do you do that?

EILER: Exactly. How do you do that? You have to write approximately ten papers that none of them can write and that present a mode of argument and a type of data that is just sharper logically, involves real hypothesis testing, quantitative interpretation of data. Elevate the game of how people are approaching these problems. You do it with one paper and you make a bunch of people who have worked on this for a while angry, and other people confused. You do a second paper; now you start to catch people's attention. You get to five papers, and now somebody wants to hire one of your students. You get to ten, and now there's a body of work, and people can look at it all together and says, this is a new way of doing this. They have gotten somewhere. They not only told me that my paper from 20 years ago was crap. That didn't feel good! But now they've done something positive that I have to react to. If I'm still mad, I go and try and disprove it.

Fine. The interpretations of these things are always going to be subject to revision and testing and all that stuff. But once they're reacting, you've won. It means now the idea that I can bring complexity and quantitative science to these questions and pose and falsify hypotheses, it's not just a game of me having a pet idea and saying it over and over again. That's dead. That to me is the victory in this field. I think we're basically just there. The first paper that I think is very high visibility, it was published in Science—not the fake Science but the actual Science—and involves sample return materials and all this stuff, this comes out on the 22 of December. It has been presented in talks and things before, but until something is in a paper, it's not real. I think that will be—there's older papers. There's another half dozen or dozen papers on the same basic subjects that predate it, but they're all in the technical literature. They're not aiming at the broad scientific community of astronomers and chemists and everybody else who reads Science and is looking for something fun to read while they're waiting for their coffee to boil or whatever. That broader community is going to confront these ideas. They'll have all kinds of reactions to them, but they will react. That, I think, is the proof that you've actually changed something, is people having to respond.

ZIERLER: In Science, the idea is you want to reach the astronomers and the biologists and the chemists.

EILER: Yeah. I have very mixed feelings about the short-format journals. They're not well-edited. They're losing control of their own process because they're oversubscribed and understaffed. They have all kinds of problems. But if you are trying to do something rhetorically new that reaches many, many people and causes them to look at something and then make a leap of imagination and picture how it connects to what they study, it's very helpful to have a publication in a place like that. That's the main reason I'm excited about it. It's a good paper, and the student who did it did an amazing job, but the main reason I'm excited about it is the idea of somebody leafing through the magazine who has absolutely—maybe they're a biologist, maybe they're in medicine, maybe they're an astronomer, it could be almost anything—and they see this thing, and they're like, "What? What are you talking about?" Half of them will not figure out what we're talking about, and the other half, it will plant some seed. "Somehow this connects to me. I study objects, matter, molecules, something; somehow this relates to what I am doing. I wonder how I would do this. I wonder how I would test my own ideas with these kinds of measurements."

That to me is the full fruition of the whole thing, is a broad scientific community that gets, "Oh, I can use this tool in an infinitude of ways." If you care about things that have chemical bonds in them, then this is for you. That, I think, is where you take the growth of this sort of field and you take it out of the hands of one person and it becomes everybody's.

Putting Scientific Revolutions to Good Use

ZIERLER: We're in the middle of it now. I don't know if you've ever played around with Thomas Kuhn and the notion of scientific revolutions and all of that. Are we in a paradigm shift, as he would define it, right now?

EILER: That's a good question. I try to maintain a healthy schizophrenia in my own mindset about this. On one hand, I do have a Vision, capital "V," about why I'm doing what I'm doing and how big I want it to get.

ZIERLER: Part of it is you don't want people to have this gentleman's agreement of self-delusion. That's not good science.

EILER: Yeah. But the other half is, don't get out ahead of yourself. I don't want to spend the last active decade of my career out over my skis talking nonsense. There has to be rigor. There has to be serious-minded self-evaluation, self-criticism. Anyone who is a laboratory scientist, you have to kind of be an Eeyore to be any kind of good laboratory scientist. You have to look at a measurement you just made and say, "Eh. I doubt it." If that isn't your reaction to something that you just observed, you're not a good observer. You need to look at everything that you create and feel a little uncomfortable, and go back and refine it and test it and repeat it. The same goes for experiments. That also has to be part of this, and not everybody who gets interested in this subject as it spreads will have that attitude but I have that attitude, and everybody who is good at it will have that attitude. That keeps you tethered down to the Earth. What does it mean to be talking about the nature of scientific revolutions when you are also looking at a spreadsheet and going, "Nah"?

ZIERLER: [laughs]

EILER: You have to hold both of these thoughts in your mind to get anywhere. Is it revolutionary in the sense of what we understand about the laws of physics and the nature of the chemical bond? Absolutely not. It's a use of those things, a use of the revolutions that occurred in sort of second-wave quantum mechanics, so sort of mid 1930s refinement of quantum mechanics, and it's what it said about the nature of electrons and chemical bonding, the nature of chemical energies. I'm not revolutionizing that; I'm using that. It's also not like the first time anyone sequenced DNA, or the first time anybody did an x-ray of the DNA structure. That's the discovery of a very specific and significant thing that exists out in nature that no one has ever seen that suddenly explains all kinds of weird, emergent behaviors. That's a revolution. It's more like—the best analogy with what I'm trying to recreate is the moment—I don't know if I've drawn this analogy with you before in the course of these discussions, but I like to think back to the sort of mid-1970s to early 1980s, when the concept of DNA sequencing was first really becoming a practical reality. Imagine you went back then, or to just a couple years before then, and you said, "Tell me about DNA," and everybody would tell you about Watson and Crick and blah-blah-blah, and the double helix. And you say, "No, no, no, no, no, no. I'm not interested in that. Tell me about my DNA. I want to know specifically the sequence of my DNA. All of it." And they would say, "You're an idiot. That's impossible. This is stupid."

ZIERLER: [laughs]

EILER: "No one will ever know. It's unknowable." Well now, it's like basically free. Like you can just know everyone's genome completely in no time at all. That is the reduction of a concept to engineering, and then the building out—it trivializes it, but then you create this capacity—if I reduce the ability to see something infinitely complex, if I reduce that ability down to engineering and now it's in my sights, and then I get to refine it and refine it and refine it forever, it means you're looking at something infinite that you never got to see. So it has tremendous utility, and implications, and an infinitude of people interested in an infinitude of problems can find ways to adapt that to their purposes for useful, new applied science or engineering. It can be revolutionary in the way that you do science, without being a Kuhnian revolution of science. I'm not actually changing my mind about what isotopes are. I just want to figure out how to use them to read the world in a different way, in a more sophisticated way.

ZIERLER: This contrast between trying to think about revolutions and then being Eeyore in the laboratory, you're articulating a famous parable in the Talmud that says, "Everybody should carry two pieces of papers in each of their pockets, one piece of paper says, ‘The universe was created for me'—

EILER: [laughs]

ZIERLER: —and the other piece of paper, ‘I am but a meaningless speck of dust.'"

EILER: [laughs] Perfect!

ZIERLER: That's the balance that you need.

EILER: Yes. I love that. That's very good! Okay, next time I tell the story, that's how I'm going to tell it.

ZIERLER: [laughs]

EILER: That's exactly right. I feel sorry for scientists who don't have both of those pieces of paper. I truly feel sorry for them. Because they have all the human potential, and all this material potential that surrounds us in the modern era, and they're either lost in their flights of fancy or they don't realize that they have wings on their back and can do things. They believe themselves to be stuck. And you're never stuck. No one is ever stuck. It's sort of like the old story of Planck's advisors telling him that basically physics is done, and then he turns around and launches quantum mechanics, and now physics is completely reborn. It's sad to imagine going to work as a research scientist and feeling like you are limited in your zone of movement. "This is my job is to be here, and all of the things I explore are highly predictable, and I'm basically just turning the crank on something that I already fully understand"—that to me is sad.

ZIERLER: Where are we now? There's the ten papers. That's what's really going to move the community. You mentioned this one paper coming out hot off the press next week. Where are we in the ten papers? Are nine to be written?

EILER: No, no, they already exist. I've now done this three times in different stages of rolling out this isotopic structure business. The first time I did it, it was half deliberate, half feeling my way forward. Then the second time I did it was a refinement of the first time. The third time, this time, I was very purposeful about it because I had been through this before. Basically the outside world that looks at a technological innovation that involves some new mode of observing, measuring, almost everyone looks at it and yawns. There's a million methods. There's a billion different instruments. We sit in this environment that is just crawling, overflowing, with technology and methodologies, and it's just a cacophony. You can't keep track of it all. Most of it falls away. People are bored with methods and seeing new methods. And yet you have to create a paper trail that explains what you're doing. If you haven't created these unnoticeable papers, then as soon as you do something significant, people will be rightfully skeptical. They won't understand what you did. There's no length of supplementary information that can really lay it all down. There will be no history of work that proves that you actually are chipping away at something, you're replicating things, you're being deliberative in your development of what you're doing. You have to create a kind of pre-story. It's almost like [laughs]—here's a good nerd comparison!—J.R.R. Tolkien was asinine enough to write The Silmarillion, okay? He knew it was ridiculous. He knew it was a terrible book. No one wants to read this book! Only people who like force themselves ever read this book. I've read it, of course, like eight times.

ZIERLER: [laughs]

EILER: [laughs] But it's ludicrous, and yet it had to be written, so that when he sat down and wrote his famous books, when you pick them up and read them, assuming you don't hate that kind of thing, there's this sense of depth. Just everything you read, you have this feeling like the person who's writing this believes that they know much more about this than they're saying. If that's fake, you know it. You feel that it's fake. It has to be real. He has to have actually written The Silmarillion somewhere and hidden it away in his desk. Only then do you believe it. So, you have to begin by building up boring papers about chemical physics, boring papers about how mass spectrometers work, calibration studies, little proof of concept applications that are setup jobs, where you measure something in a new way but you kind of knew what you had to find, like there really wasn't much of an option, and then you show that you found it; you didn't find some crazy thing. It's like if everybody in the world is dressed up like a clown, you don't know when you're at the circus. So you have to show a lot of normal things, and then when the circus comes to town you pay attention.

The others of all the papers—there's actually like 20 papers or more; there might even be 30 papers now at this point—many of them are basically just technology papers. They explain elements of the methods. There's a central paper that is now six years old that I wrote. Then there's a bunch of things that's my group members have written. That's a pile of sort of technology papers. Anybody who gets interested, or who doubts what we've done, or questions how it was done or whatever, it's all there. There's hundreds of pages of it. They can go pore through it. They can learn the background material. There's like a review paper on this stuff. All of that is there, without really the intention that anybody will start there. It would be weird to start there.

Then there are papers that are applications papers, but they're quite technical. Studies of molecules out of meteorites, and then laboratory experiments of controlled chemical reactions that create molecules that you find in meteorites. As little closed just-so stories that have lots of experimental replication, comparison with other kinds of methodologies, really hemming in the range of what answers were possible, and then showing. Then in the end we took a nanomole of this analyte, some amount that's not analyzable by any other means, and we measured its isotopic structure, a thing you could really not see any other way, but it's in a context where the answer makes sense and everybody understands that it makes sense.

The Centrality of Credibility

ZIERLER: The duality here, these hundreds of papers, they're valuable in and of themselves, but they're also about credibility for what ultimately you're trying to demonstrate.

EILER: They're about having credibility but also about earning credibility. The credibility has to be real, otherwise it blows away in the wind. I'm not saying that there's no mistakes in the papers that we've done. Maybe this new Science paper has a bad measurement in it or whatever. These things happen for all kinds of reasons. But it won't be because we were lazy or we didn't explore what we were doing. It will be because of some little idiosyncratic problem that you can quickly fix. Establishing a substantive, serious-minded credibility, that's a huge part of getting people involved, but it's not the trigger that makes them jump in. The trigger is an applied paper where you can remove the word "mass spectrometer," you can remove the word "isotope," and you still care about what was learned, so that the methodology falls away and you just see the impact. You have changed your mind about something out there in the world. That's the reason why people look at something new and say, "I wish that I could answer questions like that in my subject area." Then, they turn to the reference list and they go, "Oh! There's 20 papers that tell me how this is done and show me in all kinds of other contexts where it has been tried before." Then, they're with you. Then you've got them. That's how you set the hook.

ZIERLER: This might be a very crude question, but on the concept of building credibility, what role does membership in the National Academy play? Is it a boost? Does no one care?

EILER: That's a good question.

ZIERLER: Ultimately, isn't the purpose—the scientific purpose, not the patting-yourself-on-the-back purpose—but membership to the National Academy, it's sort of a shorthand for the credibility that all these papers demonstrate?

EILER: It conveys a level of credibility. Membership in the National Academy is supposed to be about service. That's what it's for. You are supposed to be a member of a group that performs service to the interests of the nation in examining and writing reports about and advising on scientifically relevant subjects.

ZIERLER: But the ticket to get in is the scientific –

EILER: But the ticket to get in is credibility that exists on multiple dimensions. You have to be creative, impactful, people believe that you're substantial, you know what you're talking about, your work isn't going to get blown away tomorrow. A lot of different things come into play, some of them sort of ineffable. What do you think about the creativity of another scientist? It's hard to defend what you think about it. It's just a feeling that you have. That's definitely there. I don't think that being a member of the National Academy by itself convinced anybody to pay particular attention to what I was doing. It's more like you get to talk to more people. It's very easy for me to forge new collaborative interactions with new communities. I think that's part of it, is that they kind of know, well, this is a person who comes from that part of the world and has a kind of blessing on them that only two or three of those people have, and so I'll talk to this one. It means you don't really have to work that hard to convince people to answer your emails, to talk to you at meetings, invite you to conferences and things like that. That I think is the real value to your continued career, the selfish value—access to people, where they will spend ten minutes paying attention to you before they make a rash judgment or decide to just ignore you and go off to get a cup of coffee or whatever.

ZIERLER: We'll bring the conversation closer to the present. COVID hits. Your lab is a very physical lab. You've got to be there. Was there any aspect that you had an automation capability or you said to your group, "We've got a ton of data and we have plenty to do on our computers at home"? What was the impact? What happened to your lab?

EILER: The major impact was maintaining a community culture in the group over Zoom and through occasional interactions in the lab. The labs were available. You could go into them. You just had to go in sort of alone, and masked, and things. You couldn't really interact with each other very well.

ZIERLER: Your lab is a multi-person lab when it's operating normally? There's people in there, they're schmoozing, it's all—?

EILER: Yeah, people are constantly interacting down there. My first thought was honestly mental health. The people in the group—when I'm at home, I'm busy. I have a lot of responsibilities. I have both my kids, and my wife, and all my animals and everything, living at home. The property is complicated. I have a lot of hobbies and crazy nonsense. I'm perfectly busy. I have no problems. But many of the people in my group are living alone, or with one or two roommates. They're isolated.

ZIERLER: Even harder, some are international students, many miles away from home.

EILER: Some are international students. All of them are at a stage of life where this was supposed to be a moment where they are firing this big booster rocket in their life that's going to launch them to their midlife career existence, and suddenly it's not just under threat, it's just in disarray. What does that mean to them? Then they have to deal with all the stresses of sitting and staring at their computer screen all day and seeing all the chaos. It wasn't just COVID. The election was total chaos. The fires all over the place were total chaos. Late summer, early fall, 2020, it was just an unbelievable cortisol creation factory. Everybody was stressed out. That was my main thought, honestly, was what do I do—I can't solve this for any of these people. That's not in my capacity to solve this, but I can help in some way. One of the ways is trying to maintain a sense that we are still a group, you are still a student, we are moving forward. Every week we're moving forward and something is happening.

You have to give people things to do or help them—honestly, I don't pitch projects to people. I don't like doing that. I prefer to either just through conversation with people come up with shared interests, or to more subtly manipulate them [laughs] into wanting to do what I want to do. I don't really like to say, "Okay, now your job is to do this." But I had to come up with ideas of projects that were scholarship, modeling, things that they could do that were productive, had lasting value, and they could do where they were. Basically everybody spun up a project that was of that nature. Then limping back to life in the lab. I had my own project that I started doing for my own sense of engagement in science. I wanted it to be not just me taking over one of my students' projects. I wanted it to be unique, just for me.

Sexaquarks and Dark Matter

ZIERLER: This is the dark matter search?

EILER: This is the dark matter search thing, which—this reinforces the serious-mindedness—we did not discover any evidence of dark matter.

ZIERLER: [laughs]

EILER: I guarantee you—

ZIERLER: You're in good company!

EILER: —I did not detect a single ion of something that was a dark matter hybrid, to the best of my knowledge. But it was a lot of fun.

ZIERLER: How did you get involved in that?

EILER: A colleague named Glennys Farrar—

ZIERLER: Oh, yeah! I know Glennys!

EILER: How do you know Glennys?

ZIERLER: At NYU!

EILER: Incredible.

ZIERLER: She's a famous physicist!

EILER: Yes, she is a famous physicist.

ZIERLER: And a Caltech alum!

EILER: She's a Caltech alum. She actually has a deeper history at Caltech than just being an alum.

ZIERLER: Could have been tenured faculty here.

EILER: I know. And she told me the story of how she became a not-tenured faculty member at Caltech, and it's not a great story.

ZIERLER: No, it's not.

EILER: It is not a great story. But luckily her life turned out great, and she's a wonderful colleague, brilliant person. She just got into the Academy this last year. So, Glennys calls me up. I don't know who told her that—I do all kinds of crazy things with people. So like the discovery of quasicrystals, if you know what quasicrystals are—

ZIERLER: Paul Steinhardt.

EILER: Paul Steinhardt! Quasicrystals were first proven to be a natural extraterrestrial material in my lab. I didn't stay engaged with it after that, really. Paul Asimow got involved in doing experiments and things, so I sort of stepped back from that. But the initial thought of, hey, is there somebody out there who will throw tens of thousands of dollars of resources at something really stupid-sounding? Eiler! Eiler doesn't care how much money he burns! Have him do it!

ZIERLER: [laughs]

EILER: And it's exactly right. If it's a creative idea, and more importantly the people seem fun to talk to and interact with, I'm in. So, Glennys called me. Somehow somebody told her I might help her. She had a theory of how dark matter existed as a mass roughly two AMU particle, the sexaquark. Because it has six quarks in it, plus it's fun to say sexaquark!

ZIERLER: Certainly.

EILER: If you can get up in public and say "sexaquark"—

ZIERLER: [laughs]

EILER: —and look at the audience—

ZIERLER: [laughs]

EILER: —and wait for them to blink, that's good. That's good stuff.

ZIERLER: [laughs]

EILER: She had a theory that these little things accrete to the Earth gravitationally and then stick to common nuclides and create—I guess you have to call them isotopes, because they are of different mass but have the same proton number, so they are isotopes, but they are not isotopes for the reasons the other isotopes are isotopes. If these things exist, they are isotope-like, but they're very rare, like a part per billion, and they could have a mass that's quite different from any of the known isotopes. That combination of things means if anybody saw them by accident, they almost certainly didn't recognize them. They would have seen them as some little blip that can't possibly be a nuclide. So, how will we systematically look for them? That was my passion project for the pandemic. That was me doing science therapy for myself in the same way I was trying to organize it for the students and postdocs in the group, just to have something productive you could do in the lab in addition to all of this nonsense that you do on your computer when you can't be in the lab.

ZIERLER: Did the assumption of a potential capacity in your lab follow the same intellectual progression of sensitivity to complexity? Is there a complexity approach to dark matter that you were hoping to unlock?

EILER: Sort of. Actually what I found engaging about the dark matter search is, first of all, just learning, just being a student of that field. Not in any deep way—I'm never going to understand the high-energy physics stuff that Glennys does—but just to know the take-away messages and be able to talk about the variables and things that she talks about. And then to integrate her thoughts about the cosmology of dark matter with geology. Because her starting point was, if this is true, if these particles exist, they form a kind of atmosphere around the Earth that is gravitationally accreted to the Earth. The particles are buzzing around but they're gravitationally bound so they can't really fly away. They will inevitably encounter common nuclides, and when they touch the nuclei of them, they could have scattering reactions or they could bind. She had a variety of different ways to calculate how this would work in detail. Unfortunately, everything we know about the Standard Model, according to Glennys anyway, leads to a very wide prediction in the mass of the sexaquark and the binding energy it has with nuclei, and the efficiency of capture on different atoms. It could have been that it captured on almost anything, and if it captured on one thing, then there's a limited supply of these particles, so then it won't be captured on other things. The atoms compete with each other. Atoms in the Earth are not homogeneously distributed, so you have to understand the chemical structure of the Earth to know, for each value of the parameters for the sexaquark, where it would end up bound.

Not only does the Earth have a definite chemical structure, it has a definite chemical dynamics, a kind of residence time, a turnover time of chemicals, a stirring or mixing of one part of the Earth into another. You also have to understand that, to know how would such a signature be diluted. So now what elements do I start looking at? Where do I look? I might miss it in one sample and find it in another because of the nature of their geological histories. That kind of reasoning was not part of Glennys's thought process. She was focused on a kind of simpler vision of what the Earth is. It's this static object and it has an atmosphere and then everything else. So, trying to make that more nuanced, make better choices about where we measure things and what we expect, what are our predictions that we're trying to confirm or refute, that part required a thought process from a geologist. I felt like I wasn't just there—I would have been happy to just go and make measurements for Glennys. That would be fine for me. But I also got to be intellectually engaged in the process.

ZIERLER: If it worked and you found it, it would have messed up your whole thing about geology being great because there's no Nobel Prize.

EILER: [laughs] Maybe you're right! Honestly, I don't really care. Probably the funnest part of my interactions with Glennys is we had regular meetings on Zoom and stuff—we met now and then— and I would show her the latest thing—"Oh yeah, Glennys, I did my work on krypton last week, and I found a candidate peak, and here it is. Here's the raw data." And Glennys's top of her head explodes—"Oh my God, we found the sexaquark. That's exactly what we thought it would be. It's just the right concentration. It's just the right everything. And you're telling me you don't know how to explain it." I was like, I don't know how to explain it today. We'll see, okay?

The whole search process for me was we look across the mass spectra of various elements and identify features that we know exactly what they are, and features that we understand them to be artifacts of how the instruments work, and then "other," things that are inexplicable by anything that we know, and then to hunt them down. What are they, really? If they are Glennys's famous sexaquark, then I will find the existence of one in one place predicts the height and location of any other version of that element's isotopes binding with the sexaquark all across the mass spectrum so I can immediately test and go and look. We went through this process multiple times, and every time, the candidate species turned out to be a weird atmospheric contaminant. The worst one was—oh my gosh, this one we got really close, because we found multiple candidate peaks that were all in the right position to all be sexaquark-bound versions of a noble gas. It turns out it is an industrial chemical that is in the atmosphere well-mixed at like parts per trillion abundances.

ZIERLER: Oh, wow. There's your sensitivity! [laughs]

EILER: Yeah! And when they liquify noble gases out of air for commercial purposes, they cryogenically purify it, but it's not pure-pure, and so it concentrates weird contaminant compounds that have low freezing points. It was just one of those things, a sulfur-oxygen-fluorene compound that just exists in air. We figured out that that's what it was, and Glennys hated that. [laughs] But she's philosophical enough she can put up with it.

ZIERLER: The chapter is closed for you, or are there future dark matter searches for you?

EILER: Oh, no, there's more to be done. I am supposed to visit her this spring and maybe give a colloquium or something at NYU. My daughter went to NYU so I also used to go to Manhattan pretty often. That will be fun, and we'll spin up some next thing. All we did is we disproved—the sexaquark cannot be—if it exists, it cannot be outside of a certain bound of mass and binding energetics and things like that.

ZIERLER: It's productive. You just cross another one off the list.

EILER: Exactly. All we're doing is painting it into a corner, and maybe when we paint it into a corner we decide it's not there.

ZIERLER: Is there greater opportunity—I mean, this is like the holy grail of physics—dark matter, dark energy—should there be more similar collaborations? Should geochemists, geologists be more engaged in this?

EILER: I think so.

ZIERLER: We don't know what 95 percent of the universe is made of. Kind of a big deal, right?

EILER: It is a big deal. There have been a couple of searches that are qualitatively like what Glennys and I did, but not as deliberative. They basically were people looking for very extreme versions of the same idea, people looking for so-called WIMPs, which are really massive particles—

ZIERLER: That weakly interact.

EILER: Exactly. Basically, Glennys's hypothesis is a variant of the WIMP hypothesis, where it's not massive—it has the mass of the deuterium nucleus, as it's 2 AMU. Most people who look for these things, they're basically looking like, "I wonder if there's a version of hydrogen that weighs 500 AMU." That's basically the kind of question they're asking. Those really extreme versions have been disproven for a subset of elements from a subset of materials, but the idea that you would look really carefully in the mass ranges of normal nuclides and consider where in the Earth you collected them and the dynamics of how such particles could accrete to things, I'm not aware that anybody looked at it like this.

It's the kind of thing that could and should be done again. I'm truly agnostic about whether that would be productive or not. It's pretty common when you work on scientific questions that are of interest to a variety of people for somebody to want you to guess. Will you find life on Mars? That's like the closing question at every seminar about this sort of thing. Will you find dark matter? That's not my job, and I have totally internalized that it is not my job to guess. It is my job to look for falsifiable—make predictions, have expectations for certain scenarios and test them, and if it fails, it fails, and then you move forward. I just don't like the mindset of—because that mindset leads to pet theories, and I hate pet theories. Pet theory science is just—every time I meet somebody who's got a pet theory, I'm like, "That's too bad. You're a joker." [laughs]

ZIERLER: You've got ten papers. [laughs]

EILER: Exactly.

ZIERLER: We can take a victory lap here and wrap it all up. I want to ask one question that's retrospective, and we'll see if we can tie it all together. There's where you come from and your academic pedigree and how that translated to your feelings of dislocation as a postdoc here, and the very funny story of how you got your lab started and figuring out what you wanted to do. Then there's this amazing record of not caring, which is like foundational to everything, coupled with really high-impact, game-changing discovery. How do you make sense of all of that, and it is transportable to anyone else? Now that you're a senior colleague, now that you're a mentor to students.

EILER: This is a good question. I feel like one of the most important things—every scientist who I find interesting to learn about and get to know, their personality strongly informs the way that they are a good scientist. It's not just whether they're smart or not. It's the decisions that they're making. Why are they making those decisions? The way in which I don't see too many people who I think are that much like me—in my experience I'm either unique or very unusual—is to me this entire thing, the entire scientific enterprise, my entire career, in the end it's not personal to me. It really isn't. When I have said this to colleagues who are friends or who are close enough that we talk about what we think about our jobs, they actually don't believe me. Because they'll see, oh, when I go give a talk, I'll be animated and I seem excited. Yeah, I'm excited.

ZIERLER: You're passionate but you don't take yourself too seriously.

EILER: Yeah, or also there is—I have never identified with my job so strongly that I consider it to be a paramount feature of my identity. If I woke up tomorrow and I did not have this job, I would move on. I would absolutely find something to do that day, and the next day, and the next day, and the next day. It would be fine, assuming I could afford buy stuff I like to have to eat. That's really true. That means that I can approach the details of the job as—the parts that are fun are a game. They're a very complicated game. They're a very interesting game. Just because something is a game doesn't mean it's trivial, but it doesn't define me. I don't have to succeed at this or that to be myself. It's just a thing I have decided to take on, as a game, that I like, that I enjoy, that I can see my way to the end of. And that's enough. There are other things that are bigger than this. My family is bigger than this. It's so conventional, it sounds sort of trite, but it's really true. It is informed in part by having a life-threatening disease that my daughter had when she was very young and I was very young. Formative experiences like that. Then an arc of decades of caring for a disabled person, it changes the way you view your work when you're at the office.

ZIERLER: It shifts what is truly important.

EILER: Totally! And it compartmentalizes it enough that I think it puts you in a different mindset. If I'm doing something that I think is nonsense, it's for the money, okay? I'm here because they pay me! When I go to a committee meeting or I write an NSF report or whatever, that's just because they pay me to do that, and I need money to like buy a house and stuff like that. When I'm doing something that I think is intellectually challenging and fun and important, it's because it's a great game. It's a really good game, and I want to play it, but it's not me. I am not that thing. If it fails, it's okay. If it stops, that's also okay.

Fearlessness as Antidote to Mediocrity

ZIERLER: The key takeaway here is that having that attitude naturally would lead a lot of people to mediocrity, and that's not where your science is!

EILER: No, I think out of that comes a kind of fearlessness. It's unusual for colleagues who are friends to describe each other to one another, but the one thing that a close colleague of mine once noted about me was that I was fearless about the nature of problems I would take on. I understand why he said that, but also, like, why would you be afraid? What's the worst thing that happens? All of this is fine. There's lots of scientists. There's lots of problems. We're making progress. The world is moving forward. It's okay if your thing that you tried failed. That's fine. Just be real about it. Be serious about it. Play the game right. If it fails, it doesn't matter. You'll play again tomorrow. You'll do something else.

ZIERLER: Which is why it's almost like—from a cosmic humor perspective—no one else could have been handed the lab that you were handed as a junior faculty and did what you did with it. Because you didn't care.

EILER: In a way I didn't care. I care in the sense that it's important to my value system that I do it right. It not important that it succeed in a certain way or lead to a certain outcome. That to me was never really important. And to make sure that there's always a sense of play and engagement with ideas that are truly interesting ideas. It's like writing your own novel or something like that. You don't want to write it about things that are boring. You want to write it about things that are fun, interesting, engaging, and emotional. You want to have it be rich! But it's still a book that you can put up on the shelf when you're done. That is always how I've felt about this whole activity.

ZIERLER: Finally, John, we'll look to the future. Whatever the number is, ten years left as an active faculty member—another number is, talking about these last ten papers, it's your third time doing it. Is there a fourth? Do have a vision of the fourth?

EILER: There are a couple areas of application that I would love to see happen and probably requires my involvement or help to do well quickly that include biomedical applications, certain kinds of forensic applications. These are things that they're not my discipline but I care about the outcome. I think that it will matter if there are biomedical applications that are useful, certain kinds of disease diagnosis and things like that. That's something that I value the outcome enough that I want to make sure that it occurs, and that has to be done by spinning up collaborations with people who actually understand what's going on.

ZIERLER: This gets you involved with EAS and the Merkin Institute and things like that?

EILER: It could be here. It could be Merkin. I have a colleague at the Salk Institute who wants to do this. There are other people who want to start doing these sorts of things with me. Once they begin, they will take on their own life. It's not like I have to go and do all of this. I just have to teach people how to do this right, teach them the concepts, teach them the tools, teach them how to interpret things, then once they get it they will take it and run. That is something that I would like to see happen and I will contribute to, but it's not like I need to be the first author on some paper about cancer diagnosis or whatever. I just want to make sure that it begins, and begins in the right way, and gets in the hands of people who will know what to do with it.

ZIERLER: After a lifetime of geochemistry, is part of it filling a hole about societal impact, helping people?

EILER: No. I value helping people, but it's not like filling a hole. It's more like this is an obvious thing that needs to happen, should happen, is probably inevitable that it will happen, and it will happen sooner and better if I help it.

ZIERLER: What do you bring?

EILER: I actually understand how the measurements get designed, made, interpreted, in a broader way than I think anybody who is just reading papers and trying to jump in will do. But there's other things as well. Figuring out how to do this whole field on solids, that's a big thing to me. I think I have a pathway to doing it. In a way, there's less at stake than there was five or six years ago, because five or six years ago what was at stake was, can this happen at all for complex molecules, for most of chemistry? Can it be done on solid materials is a big question, but honestly it's like big with a lowercase "b." It's a thing that will be very impactful in application, but conceptually it's the same thing. I'm excited about it happening, but there's less at stake in terms of the scientific content of it all.

ZIERLER: You've set up a platform that it sounds like there's probably no room or interest for academic leadership, like division chair, dean, provost?

EILER: No, I don't want to do that.

ZIERLER: You're going to come up in conversations.

EILER: Yeah, I'll have to deal with this in the next year or two when we have another transition. I wanted to be chair eight or nine years ago at our last significant chair election, and was not chosen, and that was probably for the best for everybody, because I got to then do the most important part of my career without a lot of distractions. You could say, oh, well now you're closer to being done and you're older, so now is the right time. I don't know. Our best chair ever in my experience became chair at 40.

ZIERLER: This is Ed?

EILER: This is Ed. The people who were really incredible chairs before him—Bob Sharp, for example—they became chair at like 40-something. The fact that I'm now 56, that's not qualifying. That's almost disqualifying, okay?

ZIERLER: [laughs]

EILER: Moreover, I feel like it just doesn't play to my strength. The nature of the job has evolved as well. It's not as fun as it was 20 years ago. Just observing, as an outside observer of what it means to be a chair, the Institute has evolved in ways where it's not the job that it was. That influences my thinking.

ZIERLER: This is bigger than GPS? This is about Caltech? Maybe it's even about higher education.

EILER: Yeah, all of the above. But then the counterbalancing factor is, I think it's really important for the culture of our division that whoever is chair needs to be somebody who appreciates, likes, enjoys exploring every branch of science that is contained in our division. That's hard for us. We have everything from astronomers to biologists running culturing labs. We have this tremendous diversity of people. How do you maintain an interest in and an appreciation for all of it? It's not that common. I don't want to be chair, but I hope that that person who is can do that. That's all I have to say.

ZIERLER: You've set up a two-pronged attack here [laughs]—"I'm too old, and I have too much interesting great stuff to do." Those sort of are fighting with each other, but it's the perfect diversion for any invitation.

EILER: The two people in our division who I think almost anybody who really understands our faculty would say—we don't have to say they were the best but they were among the best, in terms of their intellects, their character, their scientist impact, their breadth, their vision—Peter Goldreich I think is like way up at the top, and Dave Stevenson. They were both chairs, but they were both chairs under duress for a year and like two years, respectively. They never signed on for the arc of life careerist chairmanship stuff. I think partly I could be very good at that job in ways that I think matter, and very bad at it in ways that some other people would think matter. I refuse to be serious in the right way.

ZIERLER: [laughs]

EILER: I won't—do it. I won't edit myself and shape myself. You get what you get, and don't get upset. I am not going to change who I am for that role, at all.

ZIERLER: And now you've alluded to what might have been more fun about the job in previous generations.

EILER: Exactly.

ZIERLER: We walk on eggshells around here now.

EILER: Yeah. In some ways I'm not a serious person. In other ways I am a very serious person, but in some ways I'm not a serious person, and that's who I am. That's who you're going to get if I'm the chairman.

ZIERLER: [laughs] Buyer beware!

EILER: Exactly. Basic things like money—I don't care about money. I care about the fact that I can buy food and that my children live in a nice house, but beyond that I never cared. That includes the budget for my lab. That includes the budget for the Division. That includes all manifestations of money. It's not interesting to me. Do you want me to be in charge of [laughs] the Division's budget? That sounds like a really bad situation! As far as I'm concerned, money in the sciences is just a big pile of stuff that you burn and then you get some more and you burn that, and you just keep going. Meanwhile, as that is happening, important things occur over in the other room.

ZIERLER: It has worked for you as a professor.

EILER: It's great as a professor, so far. At some point I'll hit the wall and there will be nothing left to burn. But I don't know if that's a great attitude for a chairman. Somebody else, somebody more serious, would be better at it, these days.

ZIERLER: John, I want to thank you for spending all of this time with me. It has been awesome. I appreciate it.

EILER: Yeah, thanks so much for running this show!

[END]