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Kenneth A. Farley

Ken Farley

W.M. Keck Foundation Professor of Geochemistry;
Project Scientist, Mars 2020

By David Zierler, Director of the Caltech Heritage Project
December 19, 20, 23, 2022 and January 6, 2023

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Monday, December 19th, 2022. I'm delighted to be here with Professor Kenneth A. Farley. Ken, it's great to be with you. Thank you so much for joining me today.

KEN FARLEY: Happy to talk to you.

ZIERLER: To start, would you please tell me your title and affiliations here at Caltech and JPL?

FARLEY: I am Professor of Geochemistry, and I have a deep involvement with JPL but I have no official affiliation with JPL.

ZIERLER: Now, Professor of Geochemistry, you are the W.M. Keck Foundation Professor of Geochemistry.

FARLEY: Yes. Yeah, you should answer the questions!

ZIERLER: [laughs] Are you the inaugural holder of that Chair, or do you have a sense of its history, how far back it goes?

FARLEY: I believe I am not. I believe the first Keck Professor was Lee Silver. He became emeritus about the time I got the endowed chair.

ZIERLER: You are Project Scientist for Mars 2020. Is that an ongoing responsibility?


ZIERLER: Is that open-ended? How far into the future can that go? Is there a set term?

FARLEY: There is no set term. It is by mutual agreement. The mission has a logical stopping point in 2031 [laughs] so it being 2022, that's still quite a long ways away.

ZIERLER: Now, what happens in 2031, and is that related at all to Sample Return?

FARLEY: Yes, that's exactly right. Perseverance is scheduled to make a rendezvous with the follow-on missions to bring back the samples in 2031. It will also be about the time that the nuclear power supply on board Perseverance will be unable to really provide enough energy to continue to do operations.

ZIERLER: Are you involved in planning for Mars Sample Return?

FARLEY: I play an important part in the Perseverance rover mission as it interfaces to MSR, specifically in conversations of how we would have Perseverance interact with the MSR missions. I'm also involved in both motivating and explaining the science that is available in the samples that we have collected so far.

ZIERLER: I wonder if you could talk a little bit about just how important it is to get these samples back to Earth. In other words, what can't a laboratory roving around on Mars do that can be done here on Earth?

FARLEY: It's an enormously long list. This is why I agreed to be project scientist for this mission. My main interest is not in planetary science or in Mars per se but it is in geochemistry, and especially in the geochemical analysis of very small amounts of material. The history of samples being brought back from beyond Earth, especially with the lunar samples, it clearly motivates a lot of new thinking, a lot of new technique development, and a lot of really major discoveries. That of course occurred starting in the 1970s with the return of the lunar samples, but it continues to this day. The kinds of things that I am certain we can do when samples come back is to, for example, obtain radioactive decay-based dates for features on Mars. The key feature that we would love to date is when Mars climate went from being at least occasionally capable of sustaining flowing liquid water on the surface, to the incredibly cold and arid state that the planet is in right now. We think that happened about 3.8 billion years ago, or 3.5 billion years ago, but that has an uncertainty of about half a billion years.

When samples come back—samples that we have already collected—when they come back I suspect we will, in labs like those that exist at Caltech, be able to determine when that happened to within an uncertainty of about one million years. That will be huge in creating a quantitative history. By quantitative, I mean something that has a quantitative x axis [laughs] as time goes by. Right now, it's kind of just vague. That's going to be hugely important. The other one, which I will be very excited to see how it works out, is one of the central goals of the Mars 2020 mission is to look for evidence of life that might have existed on Mars when it had this liquid water at the surface, so when we think it was habitable. Today, it's too cold and too dry at the surface for any life as we know it, so it's not a great thing to be looking for. But in this distant time period from which we are collecting rocks, it looks like it was habitable. So, what is going to happen in the early 2030s is some scientist somewhere is literally going to be handed a rock, and told, "You go look for life in this rock, but recognize that it will not likely be life as we know it." Nobody has ever done that before. That is a very unusual thing to do, because we have not actually had samples that plausibly could have carried non-terrestrial life in them.

ZIERLER: When you say, "not like life as we know it," do you mean not DNA-based, not carbon-based, potentially?

FARLEY: I would say it is almost certainly carbon-based, only because even at the biggest stretches of the imagination, carbon has by far the best characteristics, and other kinds of life seem implausible. But DNA-based? To be determined. This is an interesting kind of question. You sort of hit right on it. Is DNA inevitable? If there is independent origination of life in various places in our solar system and beyond, is DNA so obvious, is its synthesis so straightforward, that everything would adopt it? I think the answer is you can't really start with that assumption. You've got to start with some other kind of assumption. That is, you have to define what life actually is and what it does, and look for evidence that that has occurred. Because otherwise, you'll potentially miss it altogether.

ZIERLER: Looking for signs of life in these Mars samples, your areas of expertise, the many fields that you represent, how will that contribute to understanding what these clues might tell us?

FARLEY: I call myself an isotope geochemist, which means that much of what I do involves the use of techniques that center around isotopes, across a diversity of scientific problems. In particular, my area of expertise is in analysis of the noble gases, and especially of helium. Helium is unlikely to tell us much about ancient life on Mars, but it may tell us about things like environmental conditions. It may tell us about time, distribution of time, things like that.

ZIERLER: A question I'm always trying to wrap my head around is, the drilling is only a few inches deep on Mars. How do we know, or how can we be confident that that is deep enough to give us samples that are interesting? Between wind erosion and radioactivity, why wouldn't we need to go down even further than that to be certain that we're getting good samples that have interesting things in them?

FARLEY: This is a great question. When I started as project scientist in 2013, we—NASA—were already committed to taking cores from a depth of about this long. In parallel, the European Space Agency was building a rover that had a two-meter drill. They were going to drill down to two meters, and you hit on why. They wanted to get away from the region that is being bombarded by radiation. This became an interesting comparison. Although at one level, I might say these are complementary approaches, in the sense that you are taking a sample from two meters below the surface, you by definition cannot see that sample before you acquire it, so you are flying blind. You hope that what's down there is what you're after. Perseverance, on the other hand, spends a lot of time driving around, finding the perfect outcrop, and then finding the perfect surface to actually take the core. So, there's a complementarity, there. There's another thing, which I learned very quickly at JPL, which was, we know how to drill a core that's just a few inches long. We don't know how to drill two meters below the surface, unless it is under very special circumstances of essentially sand on the surface. At the end of the day, Perseverance is now acquiring cores on Mars, and the European Space Agency rover still has not launched, and cannot launch for at least another six years. So, it is best to design something you could actually complete in time to make the launch.

ZIERLER: The idea of driving around and finding the perfect areas to take samples from, how do you know? It's a big planet. It all looks barren. What's good? What's not?

FARLEY: Oh, boy! You know it when you see it! We start out taking advantage of the enormous amount of orbital imagery that NASA has acquired over decades. We're not coming over a hill and discovering completely new terrain. We actually know what to expect. And, there is a fairly detailed understanding of the geology, which you should translate to, there's a fairly detailed understanding of the environmental setting in which those rocks were deposited, before we even landed. That's why we went to this landing site, because we knew that it was once a lake, with a big delta in it, where a river flowed into this crater, about three and a half billion years ago. We started with that, and we literally put circles on the map saying, "Hey, this looks like mud on the bottom of the lake. That is a fabulous place to go. Let's go see if that's what it is." That is how we have operated in the first two years of the mission, driving to locations that have these kinds of interesting geologic features. So far, we have largely confirmed our understanding of the geologic setting. Where we first landed, which we thought would be lake sediments, they all turned out to be igneous rocks. Fortunately, those were not the ones that had really attracted us. The ones that had attracted us were actually right up where the rover is exploring right now, which we have in fact confirmed that they were deposited on the bottom of the lake, which is a very habitable environment.

ZIERLER: To go back to the question about what you can know just from what the rover analyzes remotely versus what you can know with Mars samples being returned here on Earth, just to give a sense of scale, how much better is the instrumentation available to us here than what the rover can do, on Mars? In other words, when you look at that data coming in, what are the obvious question marks that just cannot be known until those samples come back?

FARLEY: I'll answer that in two different ways. The first way is just to talk about what kinds of instruments absolutely cannot be flown. It would surprise me if they can ever be flown. They include things like mass spectrometers. A mass spectrometer is an absolutely critical tool for many kinds of applications including the one that I mentioned earlier, dating. A mass spectrometer typically has components that weigh hundreds of kilograms. If you come down into the laboratories in North Mudd, you'll see probably ten of these instruments, with a magnet that is this big. You cannot make that smaller and not sacrifice the science. That's the first element of it; it's too big. The other is, it is very—sensitive. It does not want to be shaken at launch. It doesn't want to bang into the surface on Mars when it lands. It doesn't want to have to deal with temperature fluctuations of many tens of degrees every day. That's the first kind of methodology that I think probably can't fly yet is critical to many kinds of modern analytical science on rocks, whether that be things like dating, or even looking for organic molecules that might be evidence of past life. Instruments are just not capable of being flown or miniaturized to the point where they can be flown without sacrificing a lot of their capabilities. The other thing, which I think is maybe more fundamental—and I have definitely come to appreciate it, as project scientist for Perseverance—you arrive at Mars with the instruments that you thought to bring. You don't have the instruments that you suddenly think, "Wow, wouldn't it be nice if we had a this?"

ZIERLER: [laughs]

FARLEY: I can go down and find those instruments—they're in my colleagues' labs—but they are not on the rover. So especially as we seek evidence for life—and we have some limited capabilities on the rover for looking for potential biosignatures, things that might have been left by organisms, Martian organisms—the way you would approach it on Earth is you would make some kind of observation that got you interested. Maybe you see a collection of little spheres that are about the right size to be cells, or fossilized cells. You get excited about that. You say, "Well, that would be really neat." What you'd like to do is then use some kind of a tool to look at it microscopically. When I look at it with a resolution of a, say, scanning electron microscope, where you can see things that are down at the tenth of a micron or smaller than that, then you start to see structures that are at the scale of things that are—of microbes. But we don't have that capability. Then, what you'd want to do after you did that—say you saw some interesting concentric rings that look like cell wells. Then you'd say, "Whoa, is this stuff organic? What is its isotopic composition?" These are all sorts of things that you wouldn't know—I could have gone down a different path, setting up a different scenario with different instruments, but we don't have those instruments on board. You arrive with whatever you decided was what you should bring.

I don't want to downplay completely the instruments on board the rover. There are some very capable instruments, and Perseverance has made what I think is a remarkable advancement, a transition, in the exploration of rocks on Mars. All previous rovers that were making geochemical measurements were looking at either bulk compositions or compositions that were very coarse scale, where coarse scale means you might get one data point separated by a millimeter from another data point. That's very different from what we do in modern geochemistry where you make maps, at very high spatial resolution. Perseverance actually has the capability to make maps at high spatial resolution. That's a new capability. Instead of getting a bulk chemical composition, say, which is what Curiosity does, for example, we actually scan across the rock, and we make an elemental map. Hugely innovative result. You can see things that just there's no way you could have. That has been a spectacular success. It's an interesting and relatively slow evolution of instrumentation that can be flown, because it is very complicated to make these things work. [laughs] In my role as project scientist during development, there was a lot of watching the instruments get built, and trying to figure out, "Hey, is this going to work? Can we get this thing finished in time?" [laughs] It was a big challenge, and I think it paid off very well.

ZIERLER: Going back to the geochronology of Mars, three billion, three and a half billion year ago, is the going assumption that Mars kind of looked like the Earth did at that point, where we're talking about, maybe there's some very basic single-cell organisms floating around in the sea? Can we let our imaginations run wild and imagine that Mars had a thriving biosphere at a certain point, with plant life or animal life or whatever those analogs might have looked like back then?

FARLEY: Right. There's two ways you might approach that question. The first is, were the climatic conditions capable of sustaining what you just described, a surface biosphere. I would say the jury is out on that. There are people who firmly believe that there was a northern ocean, that the era of water on the surface was relatively long-lived—that is, potentially tens or hundreds of millions of years long. There are other people who believe it was there in an instant, that all of the water deposited and eroded features that we see represent freak episodes. One of the reasons this controversy exists is that nobody has been able to come up with any model that explains how liquid water could have been present for as long as the geology demands that it was present.

ZIERLER: What does that mean? Why would the geology "demand" in that way?

FARLEY: Because you can see that there was, for example, an open system lake in Jezero Crater, where Perseverance is. You can see this 40-kilometer-diameter crater had an inflow channel that cut a gorge into it. The crater filled up to several hundred meters deep of water, and it actually flowed out the other side. That's not "it rained one day." That is a lot of water moving around. We don't know for how long. This is one of the things that I find interesting just as an Earth scientist or a planetary scientist, is that there are many things that models tell you cannot possibly happen, until you go and you look, and geology says, "You know what? It did happen. You better go back and figure it out." There are lots of examples of terrestrial observations that led to new and important kinds of thinking about how things work, that the models, because all they could do is what you thought they could do, don't capture. That's one direction I might have gone. How long was this period of habitability? Was it short? Was it long? Obviously if it was short, it gets challenging to have a thriving biosphere. People will say—and I think they're probably right—that surface water is one thing, but you can well have subsurface life. We do have subsurface life, on Earth. Perhaps the way you should think about Mars is, it has a groundwater table. I think everybody agrees, even today, it has a groundwater table somewhere. It's deep down, but somewhere there has to be liquid water. Perhaps what happens is, life originated somewhere, and is now largely subsurface and maybe even was three and a half billion years ago. Then, when it got wet, if it was just a short period, it got wet, that life would emerge onto the surface, and then when it dried up, it would retreat, into this refugia below the surface. That's one whole way you might answer the question. The other way you might answer the question is to simply ask, "At an equivalent time period on Earth, what was Earth's life like?"

This has been probably the most interesting thing for me, coming into this field as a—astrobiology, geobiology; not my background. I didn't really know much about it. Most of my background is in chemistry, not even in any kind of geology, where you might learn about the history of life on Earth. So I'm sort of a newcomer to this, and one of the things I was fortunate enough to be able to do was go and look at the rocks that contain the oldest undisputed evidence of life on Earth, which are in a remote part of western Australia. We actually took a small team of NASA and ESA scientists out to this place, and I was really struck by the fact that when you find rocks—these are very old rocks. They're three and a half billion years old. They were deposited in a shallow lake or sea; we don't know the details of exactly what that environment is. There's very little such rock of that age that hasn't been so badly metamorphosed or fractured, destroyed in one way or another. Most rocks have experienced that; these rocks haven't. When you go and look at these rocks that were deposited in a habitable environment and have not been totally messed up by three and a half billion years of geologic history, life looks to be thriving. To me, that's pretty dramatic. In other words, if you find other rocks that were deposited in a shallow lake or sea at three and a half billion years ago, they also have life in them. There are no potentially habitable rocks of that age that don't have life in them. That says that by three and a half billion years ago, life had not only originated, but it had spread, and was ubiquitous. It would be hard to prove that, but you sure get the feeling, that that's the case. But up until about 650 million years ago, that life was very primitive compared to things that we are familiar with. Like plants. There may have been single-cell photosynthetic organisms that go back in geologic time, but the kinds of things that leave fossils that most people are familiar with, they didn't originate until something like the last half a billion years. So using your analogy of one (Earth), you come to the conclusion that life takes a while to develop these innovations. I don't know if that's a great argument, just stepping back from it. Like, well, okay, it happened once and it took a long time. Does it always take a long time? I don't know how you would ever know. But, if you were looking for life, you might as well use the one thing that you know, which is the Earth analog.

ZIERLER: You mentioned the likely existence of subsurface water on Mars today. Does it follow, then, that it is plausible that there is life below the surface of Mars today?

FARLEY: I'll make a statement that I think most people would agree with who have thought deeply about this—that if life ever existed on the surface, it likely expanded into any and every niche that it could, and likely still exists, if those niches still exist. Because that's the characteristic of life on Earth. It's kind of crazy to see where life exists, our life as it exists. It's everywhere! Life finds a way to get into these places and survive all sorts of horrible setbacks. It seems impossible to extinguish. I think this is one thing that most people don't remark on—that this planet has had uninterrupted habitability for at least three and a half billion years, and it has seen lots and lots of insults in that time period, really dramatic things. People get excited about the extinction of the dinosaurs; it was a big deal, but it was a blip in terms of the biomass of life on Earth. It was just a little short period thing, and then boom, life is back doing its thing. So, I think the argument is, if there ever was life, that it likely still exists in the subsurface. I think that's actually a really exciting proposition, and it's one thing that I think will—if when the samples come back, or even incredibly, if we are fortunate enough to discover something with Perseverance that people say, "Oh my gosh, that really does look like evidence of life," I think it will be a great motivator to then go and look for these subsurface refugios that likely exist for the simple reason that water exists in the ground and temperature goes up as you go further and further into the ground, so at some point you cross over the freezing point, and there must be liquid water there.

ZIERLER: There's no hope or excitement, though, that Mars Sample Return would find evidence of extant life, because it's just too surface-oriented?

FARLEY: I would say that is the consensus view, that there is so much radiation at the surface, and it is so cold and so dry, that certainly no life as we know it can exist there. People have done calculations that life as we know it on Earth, there are certain kinds of life on Earth that are adapted to dealing with high-radiation environments, and they spend a lot of their energy simply rebuilding themselves. But at some point, you just can't keep up with it. There's just not enough energy to be had to continually rebuild your structure against damage from radiation. I think most people believe, and I share this view, that the surface is sterile. This turns out to be a whole interesting separate topic of how safe is it to bring these samples back. I will be very interested to see how the next years unfold, with a combination of the science community, broadly defined, having to grapple with this question: How safe are these samples to bring back? Is there something on Mars that could hurt Earth's biosphere? That is a profound scientific question about the relationship between parasites and hosts, and that sort of thing, but it also has a tremendous element of public trust. All it is going to take is one person getting to the wrong media outlet saying, "These fools at NASA are bringing back something that will destroy us" and it gets picked up by—well, you know how it goes. Somebody has an axe to grind and they suddenly realize this is the way to do it, to drive a wedge through our community. Anyway, I'll be really interested to see how that comes out, and I'm glad that I am not responsible for navigating that particular aspect.

ZIERLER: To clarify, the concerns are biological, they're not radioactive, in terms of bringing samples back?

FARLEY: They are biological. I personally don't share those concerns. As I have heard other people say, I would eat a sample from Mars and not really worry about it. [laughs] But I do recognize that it is something that we need to take seriously, just to bring the public along.

ZIERLER: Thanks to Asilomar and the biosecurity regime that we have in place right now, is the concern then that there are different kinds of life forms for which our biosecurity innovations might not be relevant? I'm just trying to game out what the concerns might be for which we don't have an answer.

FARLEY: The first is, as we well know from things like Fukushima, the best-engineered things sometimes fail. The samples will be brought back—at least the current plan is they will be brought back inside a hermetically sealed secondary container. We are collecting samples into little sealed tubes, but those tubes have dust on the outside, and that has touched the potential—well, has touched Mars. Everybody agrees that nothing that has touched Mars can touch Earth's biosphere without being sterilized first. The strategy is to take those tubes and in space, seal them in another container, and then bring that back to Earth with a—I think the containment figure they are working with right now is a one-in-one-million chance of failure—it could be one in ten million—something like that. There are people who say, "That is still too high a risk." If something goes wrong, the spacecraft gets out of control and it—it sounds like the start of a science fiction novel—it crashes into New York City or something, and it opens up, maybe that's too high a risk. That's one element of it, is an engineered system which can fail. The other is that sooner or later, the samples will have to get out of containment if they are to be studied. At places like Caltech. I mean, we are gearing up to study these kinds of rocks, and we have been for a long time. Because you cannot build the kinds of labs that we have inside a BSL 4 facility, where you have to have like people in moon suits doing the work. You just can't do that. So, the expectation is that the samples will be sterilized, but that requires that you know that there is some lethal dose of something you can subject that life to, to kill it. There are people who believe that perhaps we don't know what the limits of life really are.

ZIERLER: But there is a playbook here, right? We have lunar sample returns. We have Don Burnett and the Genesis mission. What's different about Mars?

FARLEY: It is the first place that is plausibly habitable that samples have come back from. The lunar samples, never plausible that life could exist there. The Genesis samples, they were solar wind; no possibility of life there. The other thing, which I would say we should be humble, you look at how they treated the lunar samples to establish that they were safe—and they did take some precautions. For example, they fed some of the lunar samples to chickens. We can look back on that and sort of laugh, but I'm afraid that 50 years from now, people will look at what we do, and they will say, "Man, they didn't know what the hell they were doing!" [laughs] So, we do need to be very careful about knowing what the limits of our knowledge are. Just because you don't know something doesn't mean that it can't happen.

ZIERLER: The future tense affirmative that you're using here, you're quite confident that Mars Sample Return will happen? That's very much the trajectory that we're on right now?

FARLEY: That is the trajectory we're on. It wasn't, always. When I started as project scientist, we at JPL spent a lot of time designing the sample tubes to last up to 50 years, and we had no expectation that we would rendezvous with the follow-on missions. So, it has been a remarkable turn that NASA and now jointly with ESA, they're going full-bore. It's kind of remarkable that going full-bore has continued through the crises that we have experience, first with the pandemic and now with the war in Ukraine, which—it's a whole separate story, but it had a very negative impact on ESA, because ESA had collaborations with the Russians, which have now fallen apart. So it's remarkable that it's moving along, but there's an interesting thing, which is I think not widely known, which is, these missions have to execute, they have to launch by 2028 if they are to launch in this particular set of opportunities. You can get to Mars—without paying an enormous amount for a giant rocket, you can get there once every two years. Through 2028, those opportunities are good, meaning that if you launch, you will arrive at Mars at a favorable times of the Mars seasons. But after that, there's something like either six or eight years with no good opportunity. The reason that matters is, if you want Perseverance to play a role, which everybody does now, Perseverance is not going to be available—certainly is not going to be available—in 2036. The nuclear power source will no longer allow that. So, it either happens in 2028, they launch in 2028 plus or minus a little bit of time there, and the rendezvous happens in 2030 or 2031, and the samples come back in 2033, or my guess is this gets pushed back by another generation.

ZIERLER: What is going to change with another generation? Perseverance will still be inoperable in another generation.

FARLEY: Yeah. The point of that is, the design that is now well underway at JPL and at Goddard and all sorts of NASA centers and in ESA centers and Airbus and all these other places, that is a certain set of designs that require Perseverance, or you may have heard the follow-on missions are going to bring two small helicopters. That's a very specific design, and if you wait a generation, if you wait another ten years, my guess is you would simply scratch all of that and start again. That's not an unreasonable thing. Ten years is a lot of time in technological development. You don't want to marry technology which is no longer state of the art.

ZIERLER: Best-case scenario, we have mission launch in 2028, it comes back, really exciting stuff that is telling us all kinds of positive signs that there is extant—or past life, I should say—on Mars. Do you think that then creates both the political and scientific impetus for a next-generation mission that gets to the possibility of current life on Mars, subsurface? If so, what would that look like? Is that a manned mission to Mars? How do we do that next?

FARLEY: That's beyond my time horizon, for sure, but I think it would. Let us imagine a scenario in which there is very compelling evidence of ancient Martian life. I think that would motivate an effort to find subsurface refugios that could be investigated. I think that requires knowledge of where there is subsurface water. There are missions that have the ability to detect subsurface ice, that have been proposed and taken off the table. They're out there; they just haven't flown. Where there's subsurface ice below it, there's almost certainly subsurface water. How you would get there, I'm not sure I know. Does it involve humans? I don't know. I will say, being very honest, I cannot imagine finding the money to ever send humans to Mars. This is just as a spectator. I've really enjoyed being a spectator with the JPL engineers as they go about doing what they are doing. Perseverance, when all is said and done, it's a little over a $2 billion effort. The general risk tolerance, the willingness to say, "Okay, we're going to build this thing the best we can, but we're willing to accept an n% probability of failure"—n is at the few-percent level. For example, when we landed, the expectation was that we had about a 98% probability of succeeding. There was a 2% probability that we would land on a rock. You can't eliminate that. That's always a possibility. It can happen. That is much too high for at least most people's view of what you want to subject humans to. Humans need more like 99.9% or 99.99% probability of not getting lost. The thing that becomes very obvious is, each one of those nines is much, much more painful to get. To go from 99% to 99.9%, it wouldn't surprise me if that takes the cost up by a factor of five. Because there's just so many things that can contribute at that level. So, first of all, I don't think it is actually feasible from a money and politics point of view. I can't imagine that the United States would ever decide that it is appropriate to spend a large fraction of GDP, which is what the Apollo program did. On the other hand, and what I would say is much more exciting, and I'm a little bit disappointed that we haven't been able to get it across to the public—the era of autonomous investigation is just around the corner. I say that because the computer that is on board Perseverance, I don't know the exact date it was designed, but I believe it was designed around 2000.

ZIERLER: That's a long time ago in computation.

FARLEY: Yes! And in that time period, your cell phone became a fabulous tool. There are self-driving cars that can drive on a freeway. That technology has not arrived in space yet, but it will. Personally, if you put me in charge of NASA—please don't [laughs]—but if you did, I would want to get the public excited about what you can do with really, really capable robotic exploration. I know it's not exciting about having a person out there, it's not the same thing, but in terms of all the different places you could explore, and all the different ways you could explore it, the richness that you would get out of that is so much more than by sending humans. I just worry that if you send humans to Mars—in fact, somebody asked me this in a public forum. They asked me, "What do you think humans will be doing on Mars 20 years from now?" I said, "If they're there 20 years from now, they are going to be struggling to stay alive." That's about all they're going to do. Maybe that's why we do it? I don't know why we do these things. I don't know why we do the exploration. But I'm hoping that the public, especially the younger public, which is totally used to—we've been on Zoom all this time; they're totally used to seeing things on screens. The screen environment can be super rich, if you work at it. Anyway, that's my little thought about where exploration is going. Of course JPL is uniquely suited to take advantage of that. That is JPL's reason for existence. Hopefully that is something that happens in the next few decades.

ZIERLER: For all of the excitement and possibility for machine learning, autonomy, composition, that still leaves the fundamental engineering challenge of getting deep enough into the Martian subsurface to find signs of extant life. How do we square that circle, absent a manned mission to Mars?

FARLEY: I don't think a manned mission helps you solve that problem either, but—

ZIERLER: I'm thinking Hollywood, guys blowing up stuff.

FARLEY: Well, yeah, you could blow stuff up. I have seen notional proposals for drills, how you could drill in a much more elegant way than the first thing that you would think of. If you see how we drill oil wells—there are other ways that you can go about drilling. Or you might decide that the best place to look is beneath ice, beneath polar ice. The nice thing about looking under polar ice is you can actually melt your way through it; you don't have to pulverize rock and push it out of the way. This is the way a lot of work gets done, even in polar regions on Earth, is you just put in a heater, and trail a wire behind your heat source, and let it penetrate deeper and deeper. These are the same kind of problems that need to be overcome for exploring places like the Europa surface.

ZIERLER: Going back to the idea of the jury still being out about whether there was a robust biosphere and for how long, what about some of the theoretical arguments about what happened to the water? Where did it go?

FARLEY: Yeah. This is of course one of the things that the returned samples hopefully will be able to address. The leading explanation, which is a testable hypothesis, is that early Mars had a magnetic field. It had a geodynamo produced by the flow of iron metal in its core, just like on Earth. That shields the atmosphere from interaction with the Sun, just like it does on Earth. But then it would appear that that magnetic field ceased. We know there is no magnetic field today. When that happened? Unknown. One hypothesis is that happened around three and a half billion year ago, and then the atmosphere was simply eroded away by interaction with the ions from the Sun, so that the net result was to simply take the water, break it apart, and blow it back into space. The thing you look for, the reason that's a testable hypothesis is, it makes the prediction that rocks that are older than the period that had water will show evidence of a magnetic field. Rocks that are younger, in the period when the water dried up, they should have no magnetic field. So, one of the things Perseverance is doing is specifically collecting samples that will address that particular question. Once you know the answer to that, you'd also like to know, did that happen four billion years ago, three and a half billion years ago? When did it happen? Because then you can get at the question of why did it happen, what caused the dynamo to fail. I would say that is the leading hypothesis. In fact, that is the only hypothesis that I have heard articulated at a sufficient detail that I actually understand what it means.

ZIERLER: Very exciting, to think about the late 2020s, 2030s, what we might learn. It's pretty great.

FARLEY: Yeah, it's going to be great. It's going to be great. I'll be really excited to see all of that happen.

ZIERLER: Let's shift gears a little bit, just to get a sense of where Mars, JPL, fits into your overall research agenda. Here we are at the end of 2022. How much of your time is spent either intellectually or physically at JPL, how much of it is on campus, and where does Mars and everything Mars-related fit into the other kinds of things that you study terrestrially?

FARLEY: My main scientific interest besides Mars had been in the lab that I set up at Caltech when I arrived in 1993. That operation continues. I have a group that is actually larger than it has ever been before. Physically, I spend a couple of days a week on campus, and one day a week at JPL, and the other days at home, like most people. The ability to keep my research going after I became project scientist—I should back up a step and say that in 2004, I became division chair, which is a half-time appointment. I had prepared my operation, my independent research operation, to function with me working at half time as a research scientist, and the rest of the time working as an administrator. Then in 2013, just as I was finishing the job as division chair, I took on the project scientist role, which was also half time, until we arrived on Mars in 2021. So, I have been prepared for a long time, and I have been fortunate enough to hire some very good people to keep my lab running in my absence, and that continues. I have a group of three or four students and a couple of postdocs and a lab manager right now that continue doing the work that I've been working on ever since I was a graduate student.

ZIERLER: How far back does your interest in non-terrestrial geochemistry go? Can we trace this to your thesis, or is this really what happens when you become a Caltech professor?

FARLEY: It's definitely the latter story. I have always been very interested in instrumentation, and hands-on instrumentation. I would say sometime around 2010, JPL was interested in developing concepts for instruments that could be flown in space. As part of the joint JPL-campus interaction, there was a working group that got set up. "Hey, what could we do?" I got quite interested in that, and I essentially proposed an instrument to this group where you could date a rock, either on Mars or on the Moon. Either one of them would work. As I was doing that—that was in the run-up to the launch of Curiosity. John Grotzinger, who was project scientist for Curiosity, said, "Hey, we might be able to do this with the instruments that are on Curiosity. We might be able to date a rock that way. What do you think?" I looked at it, and he was right! The combination of instruments that were on board Curiosity could potentially be used for dating a rock. Dating is something that I had been interested in for many years. Of terrestrial rocks. I worked not at all on extraterrestrial samples or Martian samples. He encouraged me to write a participating scientist proposal. A participating scientist is a scientist who is added to the mission pretty much at the last minute, to do things which the main part of the science team had not been planning to do.

I proposed that, and it was accepted, and we tried that experiment, and it was really remarkable. It was the single most surprising thing that I think I've ever seen in my career, that I've been involved in, which is, we attempted to date this rock in Gale Crater, and we were using the ingrowth of argon-40 from potassium decay. I was basically going to be satisfied if we even detected argon-40, because there are a lot of reasons why that might not work. We measured the argon-40. Sure enough, there was argon-40 in there, so thumbs up on that. We also measured the potassium, and there were a bunch of calculations I had to go through. At the end of those calculations, I got an age of about four billion plus or minus 200 million years. And that is so obviously the right age. That's like, "Okay, it has to be, around this number!" That was just fabulous for a couple of reasons. First of all, it justified the whole effort to do this. That age was not quite good enough to move the science forward other than at a level of like, oh yeah, it's not—the age that we thought these rocks were, they're not terribly wrong. But what it motivated for me and I think for a lot of people is, there are things that you can do with new kinds of instrumentation that might be flown in the fututre. This runs a little counter to the whole sample return thing. There are things you can do, and with enough effort, we may be able to advance those capabilities.

One of the scientific goals that people always pointed at as being absolutely unforgiving of error is geochronology. You can take a picture of something, and if the picture is a little bit blurry; that's okay. If you go and you date a rock and you say, "Oh, that rock is seven billion years old," game over. Because you know it can't be older than the age of the solar system. So there are very concrete limits to what is acceptable, and the fact that this first measurement that we made with Curiosity was right down the middle where you thought it would be was pretty exciting. I got interested in that, and I participated in the Curiosity mission for about six years. Then, there was a very good alignment. I got into that because I was interested in designing this instrument, and then I got put on the Curiosity team. Then, because I had the experience working with the Curiosity rover and I also had administrative experience as a division chair, when JPL was searching—JPL/NASA—were searching for a project scientist for Perseverance, I was a good candidate. Because a project scientist's job, there is a lot of personnel management. Right now, we have a 560-person science team that I am nominally responsible for leading. [laughs] You don't actually lead 560 scientists, but you can get them pointed in the general direction of where we need to go. I was in the right place at the right time.

ZIERLER: Being division chair was good training for you?

FARLEY: Yes. I was in the right place at the right time, with the right background, and I agreed to do it. I had a bunch of interesting conversations with my faculty colleagues, some of whom were extremely negative, like, "You're going to commit your career to this, and you're not going to make it. You're not going to make the launch. The mission is going to get cancelled." Because that happens a lot. People put their heart into something for years, and then it gets cancelled. But I had come to the conclusion that I was sufficiently satisfied with what I had already done that if that happened, that was okay. As soon as I started doing the job, I really enjoyed working with the JPL engineers. What I saw immediately was, they're a lot like the Caltech scientists that I work with—super smart people, super dedicated—but they think in a completely different way. I had never seen the engineering way of thinking, and it was very gratifying to see how they'd come to me and—my role was to communicate to them, "Hey, here's what science needs, in order to be successful at collecting the samples" or working with the different instruments that are on the rover. I would explain to them what was important and what wasn't important, and they would go and try to figure out how to accommodate that. It was really fun to see the—things that seemed very obvious to me—"Oh, you would just do this"—for example, the sample tubes, the obvious thing you would do with these samples tubes, which must remain ultra-clean, the thing I would have done is, I would have put them inside a container with a little door on it. You open the door; you pull the sample out. Engineers hate doors, because doors can break and jam, so they invented this super clever thing that has no moving parts. That was really gratifying, to see how all of that worked, and to watch it go from the idea on a board to a flight device.

ZIERLER: Given the way that your career went in new directions as you developed these interests in non-terrestrial geochemistry, if I were to ask you as a postdoc, "What kind of scientist are you?"—"I'm a geochemist, I'm a planetary scientist"—however you might answer that, how different would that be with the question I'm now going to ask you—what kind of scientist would you call yourself? What's the biggest umbrella discipline that all of your research fits into?

FARLEY: I still call myself a geochemist, because this is what I love. This is where I can contribute. But I would say the other thing, as I mentioned early on, is that I'm technique oriented. That turns out to be an important statement, because I'm a generalist, in that the kinds of things I've worked on in my lab, not even talking about Mars, they range from using techniques that are in the lab, that we and others have developed—I can tell you things about, say, when mountain ranges formed, or when a glacier retreated, or the rate at which major climate change events have occurred. Those are completely scientifically unrelated, except for as they relate to a technique that exists in my lab. So, I'm very much a generalist. I feel like I can have conversations with people across a big range of scientific disciplines. That's really important both on the Mars job and also as division chair, to be able to actually talk to other scientists and feel like I know what they're talking about. I also think it's a very rewarding aspect of being at a place like Caltech, where there are people doing all sorts of really interesting things, and if you open your mind and participate with them in what they are doing, it's great. So, I still call myself a geochemist, but the thing about geochemistry is, it covers such a huge range of scientific topics. It is not a small box.

ZIERLER: Another label—of course in science there is the binary between theory and experimentation. Your work is pretty solidly on the experimentation side?

FARLEY: Absolutely, yes. My lab, or my group, for decades, has largely been driven by the capabilities in the lab, making measurements. Journeying into things like modeling—I've never done anything that is particularly theoretical, but journeying into modeling only when it is necessary to use or to interpret what we have done.

ZIERLER: For your experimental work, in the lab, at JPL, what are some of the theories, in planetary science, in chemistry, that might provide intellectual guidance for the data that you're looking at? Or when might it be important for you to talk or interact with theoreticians in GPS or beyond?

FARLEY: You mean my lab at Caltech?


FARLEY: On campus?


FARLEY: I can give you an example. One of the things that my group has been working on since within days of my arrival at Caltech is I measure helium-3 in sea floor sediment. Helium-3 is a very rare isotope for a lot of reasons that I can tell you about if you want to know. But when you look at sea floor sediments, there is helium-3 in it, a surprising amount of helium-3 in it. By measuring the ratio of helium-3 to helium-4 and using it as a fingerprint, you can show unequivocally that that helium is from the accumulation of cosmic dust on the sea floor. These little tiny grains of cosmic dust, they acquire ions from the sun. They get produced by collisions in the asteroid belt or from active comets. Dust gets spewed out. That stuff gets gravitationally attracted to the Sun, and while it is going to the Sun, the ions that are coming out of the Sun—there's a lot of helium in the sun. It's not a coincidence of the name of these things; there's a lot of helium coming out of the sun. The helium implants in these little dust particles, and then they arrive at Earth. They get gravitationally attracted to the Earth, they pass through the atmosphere, some of them, without being heated enough to lose the helium, and those grains rain out, and then it accumulates on the sea floor.

And, who cares? Well, there's a bunch of interesting things you can do with it. One of the interesting things you can do is you can look for periods when there was an unusually high abundance of helium-3, which tells you that there was an unusually high abundance of cosmic dust. Why would that be? One of the reasons could be because two asteroids collided and made a lot of dust. Another reason could be there was a comet shower. A comet shower is produced when a star passes close to our solar system and the comets, prior to becoming active, are way out in the farthest reaches of the solar system. They are barely gravitationally bound to the Sun. A star passes by, gives them a little tug, and they become unstable in their orbits. This causes periods of several million years' durations when there would be millions of active comets. I'm telling you this story because we actually found evidence of such a thing. Theory tells you, tells astronomers, that these things must happen, but there was no record of them ever having happened. We actually found evidence that such an event occurred. It's still a little bit controversial, but I think the evidence is really compelling, that 35 million years ago, there was a period of intense cometary activity, making a lot of dust. Well, I worked with Konstantin Batygin. Do you know Konstantin?

ZIERLER: I do, yeah. The rock star.

FARLEY: Yes! He is a fascinating person. He's a theoretician. My student and I met with him and Francois Tissot, who is another geochemist, and we tried to interpret some of the data that we have, just from a theoretical point of view. We found another big cosmic dust event 80 million years ago and we're trying to figure out what caused it. Is it more likely to be from a perturbation of the Oort Cloud, which is what I just described, or a collision of asteroids? That's the kind of way that I interact. What's interesting about those interactions is that a theoretician loves to get some confirmation that their theory might be true, and so it's a nice kind of interaction that I enjoy, which is, "Hey, we've developed this capability. We're not really sure what it's good for. But we think it might be this." Then the theoreticians say, "Oh, yeah, that would be really cool if you can confirm that."

ZIERLER: You mentioned theory provides certain guidance. What about instrumentation? Does instrumentation itself provide guidance for your work? Are you involved in building the instrumentation, and does that actually help you frame the kinds of questions that you're after?

FARLEY: Yeah. I've done a little bit of work in design of mass spectrometers. I have done a lot of work in the development of what you might call the front end for the mass spectrometer. A mass spectrometer requires a very purified sample. It doesn't matter whether it's the kind of mass spectrometer I use, for noble gases, or if it's the kind John Eiler uses for stable isotopes for carbon dioxide, or doing geochronology, looking at heavy isotopes like lead. You must purify the substance you are analyzing or it doesn't work. I would say the thing that sets my lab apart from almost anybody else, probably anybody else in the world, is that the front end that I have, we have spent a lot of time designing and building that, and automating it.

ZIERLER: What does "front end" mean in this context? What is the front end of a lab?

FARLEY: I could send you a picture. It's a very elaborate set of vacuum lines, with lots of pneumatic lines and wires. The basic point of this—for the kinds of problems that I have been working on, it is necessary to acquire a large amount of data. For example, looking at fluctuations in the amount of cosmic dust in sea floor sediments, we have actually produced a record that goes back to about 110 million years ago with about 10,000-year resolution. You can do the math, how many samples. It's an enormous number of samples. We have built the automated system where essentially you just feed the samples in the front end, and you hit "go" and the data comes out the back end the next day. I spent a lot of time doing that. Then once you have a capability like that, you suddenly see that there are other kinds of problems that you can win that way. This is really important. Definitely something I tell the students that I'm working with—"If you're heading into a faculty position, you need to have something that sets your lab apart." Either you've got to be smarter than everybody else, you have to have an analytical capability that nobody has, you've got to be more creative than anybody else. The niche that I established is the ability to analyze very large numbers of samples. As a side benefit, you can then occasionally throw in other samples of things that you think might be interesting but you're not really sure. But what the heck, the lab is automated, so just throw the stuff in. As I tell my students, "If you go on a fishing expedition, sometimes you catch something [laughs], so you'll find something good!"

ZIERLER: This large amount of data that you need to work with, are you already getting involved in machine learning? Are there computational programs that can help you sort through what's interesting and what's not?

FARLEY: I don't generate anything like that kind of volume of data. That kind of stuff does happen down in the basement in North Mudd, with what John Eiler is doing. I'm watching it happen, but the data we generate, at the end of the day it is large for the kinds of work that we do relative to what other labs are capable of doing, but over the entire course of my career, it's probably 100,000 analyses or something like that, which you can fit on a hard drive, super easily. [laughs]

ZIERLER: You mentioned automating parts of the lab. We'll get to this in due course, but with the pandemic, when everybody went remote—your lab sounds very hands-on—were you able to keep it going, or did you have to shut things down?

FARLEY: We were able to keep it going, and this is actually a big success story of automation. I look at the other labs in geochemistry, and they were very person-intensive. They have big research groups with lots of students, where the students are there doing the things that we have automated. We have this wonderful space in the basement of North Mudd that John Eiler and I share. It has a whole bunch of mass spectrometers in it. It's this great big room. It's really nice, because there's almost always somebody in there. Except for during the pandemic, when we were told, "Oh, you can only have one or two people in there." Not great, to have all this stuff in there. But because the lab was automated, as long as we could keep sample preparation going, which we were able to do—my lab manager was able to just keep feeding the instrument. Every few days, he would feed samples into the instrument and collect the data. So, we suffered almost no slowdown in data production, which was nice.

ZIERLER: I want to go through some terminology, just to get a sense and to orient us for future discussions. Let's start first with noble gas isotopes. What are they, and for a high school student who might just get a sense that they are interesting, why are they so cool? Why do you study them to such a degree?

FARLEY: The noble gases are helium, neon, argon, krypton, and xenon. Some people want to include radon, but it's radioactive with a short half-life, so it's a totally separate problem. The beauty of these isotopes are that they have no chemistry. I will admit right off the bat, saying I'm a geochemist working on a set of elements that have no geochemistry, because they are completely inert, is paradoxical. But it's isotope geochemistry. The important thing is with the possible exception of krypton, all of these noble gases have isotopes which are produced by radioactive decay or related kinds of processes. The quintessential example, the one that you can point to and everybody will say, "Yep, super important, I get it" is that one of the central ways that rocks are dated is from the decay of potassium-40 to argon-40, in minerals like plagioclase, which is a ubiquitous mineral. Almost every rock you pick up is going to have some plagioclase in it. This is the way you date a rock. The fact that the noble gases are inert makes your life a lot easier, because you don't have to worry about, oh, the daughter product is going to—which in this case is argon—is going to react with something, and it's going to complicate what it does. It just builds up. So when potassium decays to argon, argon just sits there. It doesn't react with anything. The phenomena that occur, it limits what can be going on.

I've spent most of my time, probably at the 90% level, maybe even more, looking at helium. At a cocktail party, at least the cocktail parties that you see around Caltech, I will say, in a joking way, "I am the world's foremost authority on helium in rocks." People usually laugh, because they cannot possibly imagine why helium in rocks is interesting. But it is interesting, and it's interesting because helium is unique, among all of the elements, in that it is not gravitationally bound to Earth, and it's a gas. When the Earth was born four and a half billion years ago, it had some helium in it. It had some helium-4 and it had some helium-3. Over the course of geologic time, the helium, which does not fit into crystal structures in the Earth's interior, that helium was mostly released into the atmosphere through volcanism. That's where the atmosphere came from, from degassing of volcanoes. But helium is not gravitationally bound, so the helium-3—I'm going to just talk about the helium-3 now—the helium-3, which is not produced by—it's almost not produced; let's say very, very little is produced—by nuclear processes. That means that any helium-3 that the Earth accreted with is now gone, and very little was created after accretion. So the Earth is incredibly depleted in helium-3. That means when cosmic dust falls in from space, you can detect it! The stuff in space is basically the same stuff the Earth is built out of, so if you want to see meteoritic debris, it's very hard to see it if you don't have a very special reason, and the very special reason is that helium is not retained by Earth. Does that make sense?

ZIERLER: Yeah, yes.

FARLEY: So, if I go to a sea floor sediment, the helium-3, about 99.9% of it, I can prove is extraterrestrial. Helium-4, on the other hand, just the other isotope of the same element—these are two isotopes that are non-radioactive—helium-4 is radiogenic. It is produced by the decay of uranium. And uranium is everywhere. When I pick up that same sea floor sediment, the helium-4 is 99.9% derived from radioactive decay. These two isotopes, of the same element, in the same rock, they have two completely different sources. And there is nothing else like that, in the whole world of isotope geochemistry. There are not places where there are two relatively abundant isotopes that are totally unrelated to each other in terms of their origin. That means that there are lots of interesting things that you can study. I told you I look at the cosmic dust derived helium-3. One of the other major things that I do is I look at the ingrowth of helium-4 from uranium decay.

There's an interesting back story here, which is that the ability to date rocks, of course it has been a desire of Earth scientists going back hundreds of years. It's kind of remarkable if you look back into the early part of the 20th century, how big the uncertainty was on how old the Earth was. You would always hear these physicists holding forth that it must be this age, or it must be that age, but we really didn't know. When radioactive decay was discovered, in around 1910, there was an aside made by Rutherford that, "Oh, and by the way, after we discovered the alpha particle, we concluded that you can determine the age of a rock, from the ingrowth of alpha particles from uranium decay." Which is a remarkable statement for somebody that had just discovered radioactivity to say, "And by the way, you can date a rock." I always think this is just incredible. In fact, there were people who attempted to do this. They didn't get great results because they didn't have the instrumentation. But then, as a follow-on or as kind of an outflow from the Manhattan Project, mass spectrometers became widely available. I don't know if you know that connection, but the Manhattan Project was hugely important in innovation in mass spectrometry. Those instruments then flowed out to laboratories, mostly run by physicists, who then created the field of isotope geochemistry, including some very prominent people that were at Caltech in the 1960s, people like Clair Patterson, who determined the age of the Earth.

When they were starting to do this in the 1950s and 1960s, there were three techniques that people were aware of that you could date a rock with. One was the decay of uranium to helium. One was the decay of uranium to lead. The final one was the decay of potassium to argon. Different groups were pursuing these, and what they realized very quickly was that when you took, say, a granite, and you tried to date it, your uranium-lead age that you got was kind of the same as the potassium-argon age, not exactly the same but kind of the same, and the uranium-helium age was much younger. As an example, you could go and date a rock from the top of Mount Whitney, and you'd get a uranium-lead age of 90 million years, you would get a potassium-argon age of probably 80 million years, and you'd get a uranium-helium age of like 50 million years. The community at that time correctly recognized that this was because helium is lost from minerals. It's lost by diffusion. It's a little tiny atom, it's uncharged, it just migrates right through. This is common experience. You fill a helium balloon—and you come back the next day and there's no helium in the balloon anymore. The helium just migrates through all sorts of things, so maybe it migrates through your crystal structure. That was kind of the state of affairs.

Through a very strange set of circumstances, when I arrived at Caltech, I interacted with this guy, Lee Silver, and he proposed that I should try to do uranium-helium dating on this giant collection of apatite crystals that he had. Long story short, this turns out to be super important, very useful, because what we were able to show is that indeed, the helium is lost from apatite, but it isn't a random sort of a thing. At temperatures above 70 degrees, it is lost very rapidly. Below 70 degrees, and especially below 50 degrees, it is quantitatively retained. Why does that matter? It matters because if you go again to a place like Mount Whitney and you ask, "Where were those rocks when they formed?"—well, the uranium-lead age of that rock tells you when the granite crystallized. The uranium-helium age tells you how it moved up to the surface. It's very hot at depth. Temperature increases at depth by about 20 degrees per kilometer. So, to cross through a temperature, call it 60 degrees, that's when the helium starts to accumulate in apatite. So, what I can tell us is, that rock that is on the top of Mount Whitney cooled through 60 degrees, 50 million years ago. What's really neat is—so I take a whole bunch of samples going down—I've done this—going down the side of Mount Whitney into, say, Lone Pine. The ages get younger and younger and younger, because they moved up on a fault, and I can tell you when that fault was active. So I got pulled into measuring the helium-4 in apatite, and then developing all sorts of interesting methods for—just a practical matter; it turns out these apatite crystals are smaller than the head of a pin [laughs] so they're super hard to manipulate, and just, how do you do all of this stuff? We developed this methodology and applied it in lots of places. I have tons of collaborators from different places that we have gone and analyzed rocks. That's using the helium-4 that is in rocks. So, there's a lot of information content in helium in rocks.

ZIERLER: Looking at the interplay of dust that comes from beyond Earth, cosmic dust, and what is happening in deep sea sediments, is it a two-way street? In other words, are you learning things both about cosmic dust and the sea floor, or is it one or the other, mostly?

FARLEY: That is exactly right. It seems sort of surprising—you can play this game either way. Essentially what you have, for much of the time, is a relatively stable situation where the amount of dust that is coming in is constant. By this I mean over millions of years, there is only a little bit of a fluctuation. Then, there will be some huge event. One of the events that we have discovered is the destruction of a 180-kilometer-diameter asteroid, pulverized to dust in a day when it collided with something else. But most of the time, that is not happening. What happens on the sea floor, the right way to look at it is, for much of the time, you've got terrigenous sediment accumulating, so that is sand and mud from the continents, and maybe some skeletons of marine organisms, accumulating on the sea floor. Then at a constant rate, you've got the helium-3 coming in from the cosmic dust. The helium-3, because it's coming in at a constant rate, it can be used to determine the sedimentation rate. As an example, if the sedimentation rate is very, very low, the helium-3 concentration will be high, because it's not diluted very much by the terrigenous matter. Periods when the sedimentation rate is very, very quick, the helium-3 concentration will be low. It's just an inverse relationship by dilution.

There are times in geologic past where the sedimentation rate is unknown but important. One example that we looked at really early on is at the K-T boundary. This is when the large object—I won't necessarily call it an asteroid, because we don't really know what it was—but some large extraterrestrial object collided with the Earth, made the big crater in Yucatán. There were people who thought that the time gap in the boundary clay layer—have you ever actually seen the clay layer? It's sort of famous, many people have seen it —people that are interested in the history of science—it is a historically important discovery of the iridium in this clay layer. Coincidentally, it is in a very beautiful town called Gubbio in Italy, and it's in the mountains in Italy. You see these beautiful white carbonate sediments, and then you see this gray-brown layer that's about that thick, and then you see more of these carbonate sediments. What paleontologists had recognized, going way, way back, probably a hundred years, is that the organisms below this clay layer all looked like one kind of ecosystem, and then right above it, totally different. That led to a lot of questions. How is that possible? How much time is in that clay? Because everything else that people had looked at was sort of gradational. Like, this organism appears, and it evolves a little bit, and then it disappears, and some other organism comes and goes. This was like all the critters that were in the area below the clay, almost all of them are gone when you get above the clay. People wanted to know, how much time is in that interval? Could it be that there are millions of years of time in there? It's what we called condensed section. That for some reason, the tape recorder was running very, very slowly then, and not accumulating much.

This is kind of a weird thing you've just got to accept—when a large object collides with the Earth, it vaporizes releasing He to the atmosphere, and that helium does not get recorded. But He is accumulated from the steady infall of little dust particles. That steady infall is a clock.

We went and analyzed the clay, and there's almost no time at all in there. There's thousands of years in there, at the most. Which tells you that the organisms that disappeared were separated in time, by the ones right above it, by only a few thousand years. This was not a huge surprise. I think most people believed that statement was true, but it really put the nail on the coffin: this event was catastrophic and instantaneous. We've done this in a couple of other places, where there are similar kinds of uncertainties, mostly over dramatic climate change events. There are other periods in geologic time when the climate has changed very dramatically, and ordinary ways that you tell time in sediments fail, and so we've applied it. As it turns out, every time we've tried to apply this method, the answer is, "Yeah, it was really fast." [laughs] Climate can change really fast.

ZIERLER: A question about terrestrial locations. Whether it's the sea floor, whether it's the mantle, or the atmosphere, are you basically after the same kinds of questions? Is it the same science in different locations? Or are these really different areas of research in your lab?

FARLEY: They're totally unrelated, yeah. They do not overlap with each other, other than through the measurement technique.

ZIERLER: What is the connecting thread? It is the measurement technique?

FARLEY: Yep. And the set of capabilities—well, maybe that's not quite fair. It is the analytical capability, but it is also the experience of decades of working on this. Like when I say we go on a fishing expedition, I have a pretty good sense of what rocks should look like, and when they don't look like that—"Oh, that's interesting. We should find out why that is." It sort of feeds on itself. Once you've seen enough, you start to see things that are anomalous, things that stand out as being unexpected. So, it is a field in its own right. As an example, one thing that we have to deal with all the time, and I was actually working on this before we got on this call, is one of the puzzles of all of this is how helium stays inside rocks. Why doesn't it leak out more than it does? It's especially problematic, or the question is especially challenging, for these little cosmic dust grains. Cosmic dust grains, they're like three microns across, and the helium that is in them is thought to be implanted in the outermost about 50 nanometers, yet I could show you sea floor sediments that are 100 million years old that still have a ton of this extraterrestrial helium in it. How is it possible that the helium has not migrated more than 50 nanometers in 100 million years, when it leaks through almost everything that—manmade stuff like—if you use Pyrex glass, helium diffuses right through Pyrex glass. We are working to understand what is the nature of the interaction of helium with materials. It has its own—I would call it geochemistry, but then people say, "It's not chemistry at all. It's just physical interactions." But yeah, okay, whatever. [laughs]

ZIERLER: Does your work with the Earth's mantle, does that get you closer to geophysics or even seismology to some degree?

FARLEY: Yeah. How do people wind up doing the things that they do? The whole cosmic dust story, it's a really interesting trajectory in terms of it being completely motivated by interactions with specific people. I arrived at Caltech in 1993, so I'm just going on 30 years now, and I met Don Anderson, a very famous geophysicist, seismologist. His great interest was in the structure of the Earth's interior. What I had done as a graduate student, and the thing that got me hired at Caltech, is I had looked at helium coming out of volcanoes. I won't go into all of the details of how this works, other than to say that the general view that I carried with me when I arrived at Caltech is that the helium-3 that is coming out of volcanoes--which it is—is coming from some deep part of the Earth that has never gotten stirred up by convection. Somehow, for four and a half billion years, part of the Earth's mantle has been protected from convective overturn, which would have brought it up to the surface, made the helium-3 go into the atmosphere and get lost. At that time, among the geochemists this was a widely held view, but among the geophysicists, especially Don Anderson, it was, "No way. That's impossible. The entire mantle convects as a single unit, and you must be wrong about the origin of the helium-3." So Don made a suggestion. It was actually a brilliant suggestion—it turns out to be wrong, but it's still a great suggestion—that maybe the helium-3 that is coming out of volcanoes is nothing more than cosmic dust that rained out on the sea floor and then got subducted. Then, it mixes back into the mantle, and it melts, and it comes back in a volcano. So, it has nothing to do with a vestige of something that came from four and a half billion years ago; it's something that went down the pipe maybe a few hundred million years ago. I thought this was the dumbest thing I ever heard, in the sense that I was well aware that this helium was in the outermost 50 nanometers of these cosmic dust grains. I said, "No way is that ever going to be retained, on the sea floor!" Subduction takes tens of millions of years, from when the cosmic dust lands on the sea floor, to get all the way to the subduction zone, it's tens of millions of years at the very least.

I got an idea that I would go and look at old sediment—it was known that helium-3 was present in the uppermost layer of sediment, the youngest layer. That was actually discovered in 1964. It's amazing to me that nobody ever really pursued it. It was discovered in 1964. Somebody said, "Huh, looks like there's some cosmic dust helium here." Nobody really ever did anything with it. Then Don Anderson plowed it back up, and said, "Hey, maybe mantle helium-3 is from subducted cosmic dust." I said, "I'm going to disprove that. I'm going to go and analyze some old sediments on the sea floor today, but tens of millions of years old. I'm going to show that there's no helium-3 in them." Well, there's a ton of helium-3 in them, so I could not disprove what Don wanted to show. It looked like it was possible.

But I made those measurements, and in what turned out to be an incredible coincidence for me that completely changed the trajectory of my career, I was getting ready to write a paper that said, "Hey, you know what? It is possible that Don is right, that the helium is being subducted." Turns out for other reasons, that has to be wrong, but we don't have to worry about that now. But I made those measurements, and then Gene Shoemaker was visiting Caltech. He had been a Caltech professor. By this time, he was at the USGS in Flagstaff. I had been at Caltech, I don't know, six months? He bumped into somebody who said, "Oh, you should go meet the new guy." Which was me. He came over to my lab, and I showed him what I was doing, and he got really excited. Within like three minutes of my showing him the data, he got really excited, and he said, "We're going to go to Italy, and we're going to prove there was a comet shower." And like—"Okay! I'm in!" And that's what we did. He had the idea that the helium-3 was telling us about these big events that he had surmised were happening but he couldn't prove. It was a great set of interactions that are—really special. They're things that completely changed the trajectory of what I have done over the years, and I could easily imagine not having taken that path and doing something else completely different. So, sometimes there is a sense that science is inevitable, and I'm not sure, had I not actually taken that trajectory, I don't think anybody else would have picked this up. Now, there are other people that do it, because we actually demonstrated that there's reason to do it, but it sat from 1964 until I started working it in 1994, without anybody really doing anything with it.

ZIERLER: The question about what was happening with volcanoes, was that your point of entrée to atmospheric science, looking at what was happening in the atmosphere?

FARLEY: Part of noble gas geochemistry, at its largest scale, is to understand the geochemical evolution of the Earth. One of the things you get out of that is when and how the atmosphere formed. I have not actually been deeply involved in that part of it, but there are definitely elements of noble gas geochemistry that contributed to that question.

ZIERLER: You said that these are all totally separate areas of research—atmosphere, sea floor, mantle. It does sound like there have to be some areas—I mean, it's all one Earth, right? It's all one planetary system.

FARLEY: Yes, right. But to look at, say, how much time is recorded in a clay layer that is 65 million years old using helium-3, it doesn't have a lot of intellectual overlap with, how much helium-4 is there in an apatite crystal from Mount Whitney? They are just intellectually completely different fields.

ZIERLER: A technique question—chronometry. What is that, as it relates either to geochronometry or thermo-chronometry?

FARLEY: I'm kind of a stickler on this one. There are two words that commonly get used; one is chronology and one is chronometry. Chronology is a sequence of events spaced in time, and chronometry is a way to tell time. Chronometry contributes a quantitative element to chronology. Geochronometry, as it is usually said without any other adjectives put in front of it, usually means—it usually has the word "radiometric" put in front of it to mean, "I'm going to use radioactive decay methods to determine when a crystal formed." The classic way that people do this is with the decay of uranium to lead and zircons. Thermo-chronometry is the thing I was telling you about with the apatite crystals. The method is called thermo-chronometry; the result is called thermo-chronology, which is, what is the cooling history of this rock? What path did a rock take to cool on its arrival at the Earth's surface? Chronometry is the methodology, and chronology is the result. Often times, you would say, "I wish to develop a thermo-chronologic history of this mountain belt, and I will use thermo-chronometry to get at that."

ZIERLER: What role does nuclear physics play in your research?

FARLEY: Mm! That's a really interesting thing. If there's time, I'll come back and comment on instrumentation. But there's a similar thing that's going on with nuclear physics. I was very fortunate—my graduate career was very complicated, and kind of ugly at the end, but I did interact with a nuclear geochemist named Devendra Lal, who—I did not know it at the time when he was on my thesis committee – he had pioneered a lot of the things that are necessary for understanding the nuclear processes that lead to helium being where it is. That has played a really important role for me over the years, is to be able to talk knowledgeably. Here's one example. I told you that almost all helium-3 in sea floor sediments is from cosmic dust, but there is a little bit that comes from what seems to be a very obscure nuclear reaction, where 6-lithium captures a neutron, emits an alpha particle, makes tritium, and tritium decays to helium-3. This is actually not that obscure a reaction; this is how one class of thermonuclear weapon works, actually. The fission-fusion bomb works that way. But it makes helium-3. Lal worked through a lot of the physics of how to understand how that reaction works in nature. Where do the neutrons come from? How far do the neutrons travel before they get absorbed? How far does the tritium nucleus travel before it comes to rest? That has been super beneficial for me. He must have died maybe 10 or 15 years ago. But then Don Burnett had a very similar knowledge base, and I benefited tremendously, and continue to benefit, from going and talking to Don.

What I find interesting about this is—Don will tell you this directly—the knowledge that he has, a lot of it is seat of the pants, "I am just totally familiar with this," and I go in and I ask him a question, he'll give me an answer, and he will not be able to provide me a reference, because it was never a topic of sufficient interest to write up. Now what has happened is nuclear physics has moved on. They're all doing their thing at CERN, and they don't care about the energies that are typical of, say, cosmic rays, which are of great interest to geochemistry in general. So, there's a whole knowledge base that will disappear, is disappearing. That's unfortunate. I've tried to pick up some of it, but to have people that are deeply knowledgeable in things that at one point they were so central to the field, but now the field has moved on, and we have not replaced people like that. Interestingly, I would say the same thing about George Rossman. He's a mineralogist. Same kind of thing. He just knows everything about minerals. So, the two most important Caltech people in terms of moving my science forward were George, because he provided me lots of mineral specimens and understanding of what minerals do and how they behave, and Don, for telling me the similar sorts of things about nuclear phenomena.

ZIERLER: This is a statement about trendiness in science, not whether there are interesting questions that still need to be asked? There certainly are, and there could be students working on them, but it's a matter of trends or what's fashionable?

FARLEY: It's that, and it's also that there are time periods in the evolution of a field where there's a sudden injection of something from another field. For example, the mass spectrometry stuff, when it appeared coming out of the Manhattan Project, coming from physics, they were all about like, "Cool, look at this, you can see all the isotopes that are in there." Then the nuclear geochemists said, "Hey, this is amazing. You can determine the temperature at which a carbonate formed," or "You can determine the age of the Earth." The streams come together for a little while. Then the physicists go off and do something else, and they're no longer contributing, and the field continues, but then it is being driven by application people, people that know how to pick up the rocks and analyze the right rocks. You have to know both. You have to—"Which rock is going to tell me the story?" But those people don't drive the further development of the field. I think the fields are just so specialized that there are, like I said, these special moments when they overlap, and then they stop overlapping. The history of what we do is so dependent on those moments. Actually, going back to this issue of sample return, I think this is going to be one of those moments, when biology, which has had an incredible revolution over the last let's call it 20 years—an incredibly rich field. They don't need to go look to Earth science to find something interesting to work on. They don't need to look to planetary science. But there is going to be a period when these fields come together to look at rocks. I'm hoping there are things in them that are intriguing, that make people think, "Gosh, there really could be—that could be some kind of life. But how do we define life?" I'm looking forward to seeing that, because I think it is going to be one of these moments when things come together.

ZIERLER: You mentioned if we had time—we certainly do—about you wanted to go in a little more detail on, I think it was the helium.

FARLEY: I think what I was going to say is, I see the same thing happening with instrumentation. Until about five years ago, people that worked in my group, they needed to know what a resistor was, they needed to know what a capacitor was, they needed to know how to operate a soldering iron. Not anymore! Because you just buy stuff. Buying stuff is great, as long as somebody is selling the thing you need. We used to make stuff, or we had somebody working in the basement of the building who could make stuff for you. Now, we don't do that at all. There's an interesting thing that happens as a result, which is a homogenization of new research labs, because they simply buy whatever the big companies are selling. Like Thermo Fisher. Thermo Fisher sells everything! But what they're selling to you is the same thing they're selling to the other guy, and so you better have some other way to [laughs] define your niche, because it isn't going to be because you have a better instrument that you built yourself. Looking at the history of Caltech, where especially isotope geochemistry came from in the Wasserburg era—in the 1960s and 1970s, they invented stuff, and they built stuff, and that whole approach to our science is disappearing. It makes me sad, because I think even on a small scale, this is the way innovation happens. Without the ability to turn an idea into a piece of hardware that tests the idea, you're kind of stuck. I think many of the students that I see coming through, it's just not in their background to even know what a resistor is. It's sort of a funny thing. It seems funny to me! [laughs] Like, "How could you not know?" But then of course where would they have ever seen a resistor?

ZIERLER: Is it computation? Is it a generational issue where students are just much more comfortable with software than hardware?

FARLEY: Oh, I might even make the same comment about software, in that I don't see a lot of ability to code simple solutions to problems, because it's always easier to just—"Oh, I'll do it in Excel." Like, "Yeah, okay, well, that's great, if Excel does the thing that you want it to do." That particular bit might be a problem that is more unique to Earth science, which for good reason attracts people that are a little less happy sitting in front of a screen. [laughs] That's how I got into it. I didn't want to sit in front of a screen. But I really notice it in the hardware side. Like if you ask even people in my group that are using it all the time, "How would you have a computer turn a valve from open to closed, on the vacuum line in the lab?" I don't even think they would know how to phrase that question, whereas ten years ago, I think people would say, "Gosh, I think I need to have a digital output line, and maybe I need to have a relay." They wouldn't know what that means now. I'm trying to educate the students, mostly so that when they go out and make contributions in other labs or set up their own labs, they can do some of the stuff that we have been able to do.

ZIERLER: The concern, though, obviously—these are techniques that are really important for outstanding scientific problems. That's what you're upset about.

FARLEY: I think the thing that really I do find disappointing is the number of junior scientists who simply want to buy the thing and then run it. I mean, it's great. When a company makes a thing—like I have a mass spectrometer that was built by Thermo Fisher. It is a fabulous piece of hardware. I could never build anything as good. But the software is horrible, and I rewrote all of the software to drive the thing, with the collaboration of people in my group. I can make that thing do measurements that no one else can do. If you lose that ability, then you just do whatever the manufacturer thought you wanted to do with it. The manufacturer is in the business of making instruments and making money. They're not interested in tweaking out some little piece of performance that allows you to do the thing you want to do.

ZIERLER: These trends, part of it is just generationally, you probably grew up tinkering and building stuff, and not so much on video games. That's probably what this is all about.

FARLEY: Yeah, I'm definitely going to sound like an old guy, but when I was a kid, my father and I together built a Heathkit CRT and a Heathkit printer, to go with the first generation home PC.

ZIERLER: [laughs]

FARLEY: We had this giant box of a home PC, and we built this monitor for it, and then we programmed it in Assembly Language. It was fun! [laughs] It set me up really well. That's obviously not what people are doing today, nor should they be. I don't know how you fix the problem. Maybe it's not even really a problem. But it's hard not to step back a little bit and say, "We are losing something. We are losing a skill set." It's just like the nuclear geochemistry thing, that there's a skill set or a knowledge base that feels important, but not important enough that you want to commit people's careers to it. I don't know what the answer is.

ZIERLER: For the last part of our talk today, some more general Caltech and JPL questions, to round things out. To stay on the science, a subtext that has been running through our conversation so far is, just by virtue of you being at Caltech, your career went in all kinds of unexpected ways. Just to play the counterfactual, when you came to Caltech and you envisioned a research agenda, absent all of those outside surprises, outside interactions, what would you be working on? How different would it be, if you could draw that line from your original game plan?

FARLEY: What I had done as a graduate student was looking at mantle-derived gases in minerals erupted in volcanoes. That is what I proposed to do when I was doing the job interview thing. I did a little bit of that in my first couple of years, and I am glad I moved on to other things, because I look at where that field is today, and it really hasn't advanced that far. It's because it is a sample-limited problem. There are only so many volcanoes. If you are an analytical person, a person that uses analyses, like I am, once you have analyzed all those places, there's no point in analyzing it anymore; you're done. I think I did not recognize it at the time but that field was reaching that point. There have been some interesting improvements in capabilities, but they haven't fundamentally changed the landscape. The more interesting parts of that problem transfer to other kinds of geochemistry like the stuff that Francois Tissot does—other isotope systems, not with the noble gases. So, I probably would have been forced to go somewhere else, do something else.

One of the realities of running a research lab is you can't possibly survive on a single research grant at a time. You've got to have several things going. This is truly difficult, because if you become the expert on one particular thing, let's say the helium isotope composition of volcanoes, if you're really good, you could get a research grant, and potentially you could renew it cycle after cycle after cycle. There are people that do that, and I did that early in my career. But you need to have more than one research grant, and you could write another proposal to do something like that, but that program will say, "We're already supporting you. We're not going to support even more of the same. You've got to go do something different." Inevitably, you get pushed, when you are a technique-oriented person, you decide that—you've got a hammer, and it's a very expensive hammer, and you need to go find some nails. I think inevitably I would have been forced to do that, but I don't know where I would have gone. Maybe that's the way everybody's career works, that you interact with somebody who suddenly sets you in a new direction. For me, they happened sort of spontaneously. I wasn't looking to do something different.

ZIERLER: This trajectory, it's so classically Caltech, by virtue of its smallness, the very low administrative boundaries between disciplines. Did you appreciate that reputationally about Caltech when you joined the faculty? Were you open to the idea, "I'm at a kind of place where, who knows what I'm going to be working on decades from now"?

FARLEY: I don't think I thought that. I do remember very clearly when I got hired—when I got offered the job, there were several people who were retiring that were doing things that I was interested in. I talked to Ed Stolper. I called Ed, and I said, "Can you reassure me that you are not going to leave Caltech soon? Because you are the only person that is doing things that I'm interested in." He said, "Well, I will assure you that I'm not going anywhere. But you will discover there are lots of things that you could participate in." And he was absolutely right. I don't think I thought it. I did realize very quickly that Caltech was very serious about setting junior faculty up well. When Dave Stevenson was organizing my offer letter—after I had been told I would be offered a job, I came and talked about what it would take to set up a lab. Everybody told me, "Come prepared with a dollar figure, and you've got to be tough. You gotta hold the line on that dollar figure—‘I need this much money to set up my lab.'" I was all prepared to do that. I got toured around and talked to everybody, and it was very exciting. I was noticing like, "I'm leaving in about 10 minutes, and Dave has not yet asked me for this dollar figure." Just literally as he's shaking my hand as I departed, I said, "Dave, we haven't talked about what I need for startup." He said, "Just give me a number, and we'll give it to you. But in return, you have to understand, there is no excuse for failure, then."


FARLEY: This absolutely set the tone, and it is the right way to treat junior faculty, and it's one of the reasons why I think Caltech does so well in terms of tenuring such a large fraction. At least in GPS, we tenure a large fraction of people. Some of it is because we're—I think we are sufficiently capable of selecting people who are good enough. But then you give them resources, and you make them great. I think we select good enough people, and then we give them the funding it takes to be great.

ZIERLER: That's awesome.

FARLEY: I don't know other institutions that can or will do that.

ZIERLER: As division chair, what perspective did you appreciate, not just about GPS, but in your interaction with other division chairs, Institute-wide, about what makes Caltech special?

FARLEY: Hmm! It's interesting, in that where I thought that question was going—the answer I was going to give you was cohesion, the cohesion of the GPS faculty. I'm a little worried that the pandemic has eaten away at that. But in GPS, it is a remarkably cohesive group. It was eye-opening to me to see that it isn't that way across all the divisions. It's a very special thing. It's a hard thing to figure out how you get it, or how you keep it. But then in terms of what makes the institution work, as division chair, I thought it was remarkable that we would be—we, the IACC, so the division chairs, the president, and the provost—there are eight of us sitting around a table, and each new hire at the faculty level gets discussed in a pretty rigorous way. I think almost all of the time, the IACC voted in favor of a candidate that was being brought through by a division chair for a faculty position. But just the mere fact that there is this very small group of people who take the job seriously, and not some giant structure of deans, and this, that, and the other thing—I just found that part really incredible, that that's the way the decision-making works. It's sort of a fearless kind of operation, in that we'd be looking at hiring somebody, and "Oh, yeah, this person is going to need 50,000 square feet, and they're going to need $2.5 million in startup." You look at the provost, who is probably thinking, "Oh, crap! Where am I going to get that?" [laughs] But the provost always says, "Well, if this is what it takes to be great, we're going to be great, and we will find a way to do it." Then of course the other part of it usually goes to the president. Like, "Okay, we have to go figure out how we're going to find a donor [laughs] to give us this money." Again, there's sort of a fearless search for somebody who is going to be able to provide. So I think the part of it that I saw, that I would say makes it work, is just the super compact administration. It's not tiers of middle managers. You go straight to the top. We only have six divisions. We don't have 60 departments that are all competing against each other.

ZIERLER: Last question for today. To bring it right back to the beginning of our talk, the Caltech-JPL connection, from your vantage point, what have you learned about how the sum really is greater than its parts, in terms of what both JPL and Caltech can achieve together?

FARLEY: Looking at it from the other side of the fence, with the engineers, they—well, with the JPL-ers; let's call them that—the people who work at JPL, they are extremely proud to be part of Caltech. They're proud to be part of NASA, but being part of Caltech is special and sets them apart from other engineers that work at NASA centers. Other NASA centers don't have this kind of connection. I think it really drives home the point that—there's this inspirational slogan on the wall of the director's office that says, "Dare Mighty Things." I think they look at campus and they see, "This is what those guys are doing down there. They're doing LIGO. They're doing all these fabulous things. We can do that, too." From that point of view, that's great. The other is just the practicality of many of us as faculty members realizing that there are things that we want to do that are much bigger than we could do individually. Some of those things can actually be done with JPL. Like Mark Simons, really interested in using satellites for things like geodesy, so he can do what he wants to do. The climate group, they can actually get a really direct connection to space missions that are generating high-quality data. Everybody has access to the data, but to be that connected to the people that are designing the instruments, it's like you're plugged in at the source instead of waiting at the end of the faucet for the little drops to come out. That part of it is great. The other part of it for me was to have a connection with people that could figure out how to turn ideas into instruments. As you've gotten a feel, that's important to me. When we were in that first phase of when I got drawn into working with the folks at JPL, I wouldn't have the faintest idea of how to build some of these things, but they were like, "Oh, yeah, this is the way you do it." So, I know a lot of people that realize dreams that they would never be able to realize without that connection.

ZIERLER: This has been an awesome initial conversation. Next time, we'll go all the way back, learn about your father, his interest in computers, and so much else.

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Tuesday, December 20th, 2022. It is great to be back with Professor Ken Farley. Ken, thanks again for joining me.

FARLEY: Thank you.

ZIERLER: Today we're going to go all the way back to the beginning. I loved how you mentioned working with your dad to build a computer. Let's start with your parents. Tell me a little bit about where they're from, where they grew up.

FARLEY: Several different places, but mostly in New York City and Washington D.C.

ZIERLER: Which ones, in which areas?

FARLEY: Mom in New York City and my dad in Washington D.C. They met in college at George Washington University.

ZIERLER: What were their professions when you were a kid?

FARLEY: My mom, for many years, worked as a technician in a biomedical lab. My dad, early on, when I was young, he worked at UCLA as a physicist. When I was about seven or eight years old, he took a job with Xerox as a principal scientist.

ZIERLER: Did your dad have a PhD in physics?


ZIERLER: What was his research area?

FARLEY: This is a little bit funny; he worked in nuclear physics. What he did for his PhD thesis was to determine the half-life of thorium-232, which interestingly is a quantity that I use all the time in my research, since that governs the rate of the production of helium-4, by alpha decay. I have never cited his work, because shortly after he finished his thesis and determined the half-life of thorium-232, somebody did it just a little bit better than he did [laughs], and got the number that goes in the big book of such quantities.

ZIERLER: Growing up, you were definitely around science. You got exposed to academic science from an early age.

FARLEY: Yeah, I think there wasn't much doubt that both my brother and I would be scientists when we grew up. That seemed obvious to both of us.

ZIERLER: Your dad was at UCLA. Were you born in Los Angeles?

FARLEY: I was. I was born in Santa Monica.

ZIERLER: You were there until, you said, age seven?


ZIERLER: Where was Xerox? Where was the relocation?

FARLEY: It was just outside of Rochester, New York. Interestingly, what my dad worked on when he was at UCLA, he was a soft money scientist and he did a lot of work related to the Apollo program.

ZIERLER: Oh, wow.

FARLEY: In 1973, when the Apollo program suddenly vanished, after being successful, it was not a great field to be a soft money scientist in, so he took a real job, at Xerox.

ZIERLER: What did he do at Xerox?

FARLEY: I don't know. He didn't really talk about it very much. But I am guessing it had something to do with the perfection of toner.

ZIERLER: He didn't talk about it not because this was like national security stuff; he just didn't share?

FARLEY: No, it was not something he brought home with him to discuss.

ZIERLER: Did your mom have an educational background in science? Was that her trajectory also?

FARLEY: Yes. She had a master's degree, I believe in chemistry.

ZIERLER: Did you recognize or did it seem pathbreaking for your mom, just generationally, to work in science? Did that seem sort of ordinary to you, or special?

FARLEY: It seemed fairly ordinary. She was a technician, and I think that was not that uncommon. At least I met several of her coworkers, and they were also women, so it didn't seem surprising to me.

ZIERLER: You grew up in Rochester? Through high school, you were in Rochester?


ZIERLER: Did your parents or family ever note the weather differential, moving from Los Angeles to upstate New York?

FARLEY: I don't remember my parents commenting on it, but boy, my brother and I sure liked the change. We loved going to a place with a lot of open space, and snow, and playing in the woods, that kind of thing.

ZIERLER: You went to public schools, Rochester Public Schools?

FARLEY: Interestingly, we were in a suburban town called Webster, and Webster is where Xerox had its big research and development facilities. So, although it was out in the countryside, it was a lot of science and engineering folks in my high school. [laughs] All of my schooling. It was a great place to go to school. I got a really good public education.

ZIERLER: For you, was it always going to be more on the math and science track when you were thinking about colleges?

FARLEY: Yes, and I was pretty on the fence between wanting to go into chemistry and wanting to do something like oceanography. When I applied to go to college, the two places that I applied, one was Yale, and the other was UCSD, which has a very strong oceanographic program, which is where I wound up going for my PhD.

ZIERLER: Were there space programs or missions that you followed closely as a kid? Anything that might have planted a seed for what you would become interested in later on?

FARLEY: I can just say, I do remember when the Viking landers landed on Mars, and I remember my dad came home from work and we watched the pictures show up on TV. They kind of scrolled across the screen. I feel like the screen [laughs], the bit rate was so low. I don't remember anything other than, "Wow, my dad came home to watch this! This must be important!"

ZIERLER: Why ultimately Yale? What was interesting there? What was happening there that attracted you?

FARLEY: I'm not really sure I put a lot of thought into it. As I said, it came down between UCSD and Yale, and I got into both. I had been speaking with a Chemistry professor at UCSD, and he said, "You'd be better off coming here as a grad student." That made a lot of sense to me. I have appreciated that I did go to a liberal arts college and picked up a lot of stuff that I would not have picked up along the way in any other way.

ZIERLER: That was exactly my question. USCD would have been more of a technical education for your undergraduate?

FARLEY: Yeah. I guess. I didn't go, so I don't know, but looking back on it, the experience that I had at Yale, there was a big element of things other than science and math.

ZIERLER: How focused were your interests in chemistry right as a freshman? Did you have a nuanced understanding of the kinds of chemistry you wanted to pursue?

FARLEY: No, not really. By that time, my brother was already in grad school at Harvard as a chemist. I knew pretty much what he was doing. I hadn't actually thought about a specialization at all. I had assumed that I would actually be doing pure chemistry. I didn't stumble into geochemistry until quite late.

ZIERLER: Pure chemistry would mean what, just sort of a more generalist approach?

FARLEY: No, as opposed to geochemistry.

ZIERLER: I see. Did you have any exposure to geochemistry, or did you take geology courses as an undergraduate?

FARLEY: I didn't until my senior year. In my senior year, I had started to see—actually, I guess it was in my junior year—that maybe I wanted to spend more time outdoors. It was a good opportunity—in the summer after my junior year, when I was starting to work on the senior thesis project, I started out working in a chemistry lab, which I look back on and it was in the sub-basement, a windowless sub-basement dungeon, and I did not really like that. I wound up through literally just talking to a professor I knew, a meteorology professor who I had met, whether there were any opportunities in that kind of field. He wound up advising me to go and talk to a geochemist. That person, that professor, his name was Karl Turekian, he talked to me for about five minutes and said, "I've got to make some phone calls. I'll get back to you." He made some phone calls to establish that I was not actually failing out, and he agreed to take me on as a summer intern. That's how I got pulled into geochemistry.

ZIERLER: What were some of the experiments or laboratory experiences that were really formative for you as an undergraduate?

FARLEY: After I started in that lab that summer, there was a research cruise going out of Hawaii that was being led by another professor, a UCSD professor, who then ultimately became my thesis advisor. The person that I was working for, this guy Karl that I was working for, said, "Hey, you should go on that research cruise and get to know the chief scientist on that cruise. He's somebody that you might want to do your PhD with." I had a very interesting trip in the summer. I went on a research cruise that sailed out of Honolulu. We did some water sampling, and we also landed on a handful of very tiny volcanic islands that are out to the north and west basically of Kauai, places nobody ever goes because they're wildlife preserves, and collected rocks. That was fabulous. I loved doing that. That's kind of what I wound up doing for my thesis. That was a great adventure. Therefore, I got to know that professor, whose name was Harmon Craig. Then in the spring of my senior year, he invited me to go on another cruise, which was amazing. This cruise started in Auckland, New Zealand, and went through probably 20 different islands, in the Solomon Islands, in Papua New Guinea, places where it is extremely rare for anybody to show up. We would sail up to these islands, and get in a Zodiac, and go ashore, and the people that lived there, they would come running down to the beach excited about seeing—literally seeing white people. [laughs] It was very fun. Collecting volcanic rocks. Some of the rocks that we collected on that trip became part of my thesis work. That was a very big connection between what I was doing as an undergraduate, getting a chance to see what graduate school would be like, and also working with this very well-known geochemist named Harmon Craig. That kind of sold me on going to grad school at UCSD.

ZIERLER: Did you stay connected to UCSD through undergraduate since you already had that point of contact at the beginning, and you had that option—"Come to us for graduate school"? Did that remain in your mind?

FARLEY: Partly. I don't think UCSD did. I did want to get [laughs] back to California. I liked California. It just was a better fit for me. I spent a lot of time outdoors, and definitely in thinking about going to grad school at UCSD, I was thinking, "Yeah, there's a lot of great places to be outdoors in California." Not so much in Connecticut.

ZIERLER: Was it in California, when you went back for graduate school, that you got into ultra-marathoning?

FARLEY: Ultra-marathoning actually didn't start until I was division chair, so that didn't start until many years later.

ZIERLER: Were you always athletic, though? Did you like to do sports and things like that?

FARLEY: I liked to hike. I definitely liked to go camping and hiking. I wasn't a particularly serious athlete.

ZIERLER: It was really from your senior year that you got focused on geochemistry?

FARLEY: Right, and so I wound up in grad school with very little background in geoscience at all. Literally I had taken one class in meteorology, and one class that was very specialized but intriguing called "Geochemical Methods in Archeology." I was quite fascinated by the fact that you could, for example, pick up a stone tool on, say, Easter Island, and you could establish that that stone tool did not originate on Easter Island; it had been brought by the Polynesians from somewhere very far away. This is the way that it is well-established that the Polynesians traveled from island to island. I thought that was fascinating, that the rocks tell you a story like that.

ZIERLER: I know UCSD is a relatively young school. Were the professors there part of the founding generation of geochemistry?

FARLEY: The people that I worked with definitely were. At that time, Scripps had a very strong program in isotope geochemistry, including people who studied things like lunar rocks, and also in stable isotopes, which is the technique that gets used, for example, to determine climate histories, and also in noble gases.

ZIERLER: Tell me about the game plan when you got to San Diego. Who did you want to work with? What did you want to focus on?

FARLEY: I arrived assuming I was going to work for this guy Harmon Craig, who is a very famous—even at that time, he was a very famous geochemist. He had established a lot of the basics of stable isotope geochemistry. He had come from Harold Urey's lab. Harold Urey is sort of the founding physicist of a lot of isotope geochemistry. Harold Urey was also the advisor of just a whole collection of the greats in geochemistry. They kind of launched all at about the same time in the 1950s and 1960s. Harmon Craig, when I started, was a notoriously difficult individual. I naively assumed that I could deal with it. I started in that lab, and like most students, I wasn't really sure what I wanted to do, but unlike most students, I didn't really have very much background to understand why you would want to do some of the things that were being done. So, I flailed around on various kinds of research projects that were not related to noble gases. They were other things that were going on in the lab that I worked on. Then ultimately I wound up working on gases trapped in bubbles in crystals in volcanic rocks. I really enjoyed working with the mass spectrometers. Pretty quickly, that became my thesis.

ZIERLER: Do you see any value, looking back, in not having a strong background of geosciences at the beginning of graduate school, and needing to learn that stuff as a graduate student, not from your undergrad experience?

FARLEY: I'm not sure that I would say it was an advantage that I didn't know it, but I would say it is an advantage—or at least it felt to me like an advantage—to come in being confident that I understood chemistry and physics pretty well. This is a relatively common sign when we admit students; they will come in with a similar background. I encourage that. I think it is useful to come in with a strength that is other than in the field that you are ultimately working in. In many ways, it is easier to come in with strength in chemistry and physics and learn geoscience than to have strength in geoscience and then be told, "Oh, by the way, you've got to go take an undergraduate chemistry class at Caltech."

ZIERLER: [laughs]

FARLEY: Taking an undergraduate chemistry class at Caltech can be quite daunting.

ZIERLER: And you did that?

FARLEY: I didn't do that. Well, when I started at UCSD, I had to catch up on geoscience classes, which tend—there is a lot of qualitative material in geoscience and in oceanography. There's nothing wrong with that. Some people kind of roll their eyes and think it's not real science. But boy, if you want to understand, for example, the way ocean circulation works, there is a very technical mathematical description of it, but then there is also just a lot of basic qualitative understanding that is important. I think it's easier to learn that than to go and actually try to learn all the really hard-core stuff, and also, by the way, be working on your thesis.

ZIERLER: As a prelude to developing your dissertation, as you read up on geosciences generally and applied that to geochemistry, what were the big questions in the field? What were the exciting projects potentially to work on, to make contributions to?

FARLEY: In the lab that I was working in, the thing that attracted me the most was measurement of helium isotopes. This goes way back in my career. Partly because at that time, there were literally only two or three places in the world where helium-3 could be measured routinely. It's a hard measurement to make. It requires a dedicated instrument. At that time, there were two broad things that were going on that are closely related, and I was interested in both. I explained last time that the helium-3 that comes out of the Earth is a vestige of the helium that the Earth accreted with, four and a half billion years ago. There are two things you can do with this. One is you can learn about the geochemical evolution of the planet over four and a half billion years. And it was pretty clear even from the first analyses that were made on volcanic rocks—this is very surprising, that any of that helium-3 had survived. Because the general view was the entire planet had circulated through this giant convection system that brings the solid rock of the Earth's interior—it flows. It flows up to the surface, it melts, it erupts, it degases, it subducts, and doing that for four and a half billion years, running that big circulation system, it was a surprising discovery that any helium-3 survives. It is still surprising that any helium-3 survives.

ZIERLER: The theoretical basis for why that is surprising, I wonder if you could just explain that a little bit.

FARLEY: It is important to understand that a lot of geoscience does not derive from, "Let's sit down and think about this, and then go do an experiment." It starts with, "Let's analyze this rock and see what's in it. Oh my gosh, there's this helium-3 in here. Where could that possibly be coming from?" Here's actually how this worked, because this follows the other pathway. I was going to tell you, there are two pathways why helium-3 is interesting, or was interesting, at that time. One is about the evolution of the Earth's interior. But the thing that was really motivating a lot of the work that was going on in the lab that I was working in, at the time, was very different. There was a set of experiments that were done in probably 1969, something like that, that showed a very surprising thing. They were accidental. It was not the purpose of the observations. But Harmon Craig took a bunch of water samples from the ocean and discovered that there was more helium-3 in those samples than one could account for. The way you would account for any helium-3 that was in there is there's a very tiny amount of helium-3 in the Earth's atmosphere. Helium is in solubility equilibrium with the ocean, so the ocean has a little bit of helium-3 in it, also. But what he showed is that—he had something like five samples, and there was one sample from 2000 meters' water depth, where there was a little bit more helium-3 than you could account for with dissolved atmosphere. It had an unusually high ratio of helium-3 to helium-4 compared to the atmosphere. I don't actually know what his thought process was, but he made a most spectacular suggestion that this helium-3 was coming out of volcanoes on the sea floor. It was coming out of the Earth's interior at volcanoes on the sea floor.

That turned out to be the key thing that then drove a lot of exploration of where this helium-3 might be coming from. In particular, it contributed to the discovery of hydrothermal vents on mid-ocean ridges. You're probably familiar with black smokers. You get this 300-degrees-centigrade water blasting out of the young volcanic rocks on the mid-ocean ridges. That's where the helium-3 is coming from. Shortly before I arrived in that lab, a postdoc working in that lab had made measurements very close in on the mid-ocean ridge, proving that that is where the helium-3 was coming from. Took a whole bunch of water samples at different depths across the ridge, and when you plot it in a contour map, it looks exactly like a smokestack plume, that you can actually see the hot water coming out of the ridge, with just a very high amount of helium-3 in it. It comes up, it cools, it reaches neutral buoyancy, and then it blows along in the prevailing current. So, that's cool. It establishes conclusively that the helium-3 is coming out of mid-ocean ridges, and it is actually a way to prospect for large hydrothermal vent fields. This is a way that then others went on and found other hydrothermal vents simply by looking for these big plumes of basically the "smoke" that is the helium-3 rich signal.

But more importantly, this helium-3 is a tracer of deep ocean circulation. At that time and still today, the circulation in the deep ocean is very hard to characterize, because it is extremely slow. Unlike the surface ocean, where you can put in a float and just watch where it goes—on a one-year timescale, if you put something in the Gulf Stream, you'll see that it travels a thousand kilometers—if you put a neutrally buoyant drifter—and this is some of the work that we did when I was a graduate student on some of these cruises—if you actually put something that floats at 4,000 meters' water depth, floats neutrally, and there's a way to trace where it goes, what you see is it moves really, really slowly, and also it's not like it's in a river; instead it winds up doing these very slow orbits. It moves one way for a while, and then it moves another way. It is responding to things like tidal interactions. So, it's very hard to use an active tracer like that. But the helium has been coming out of the ridge for probably forever, and so it has averaged, it has integrated, over a long period of time. This was of great interest to oceanographers who were seeing for the first time what the direction of the flow was.

There were some very surprising and unexpected features of that flow that were motivating a lot of the research cruises that I went on. Many of the research cruises that I went on did two different things at the same time—collected water samples to map the distribution of the helium-3 blowing across the ocean - or through the middle of the ocean, and as long as you were out there, you might as well stop at these volcanic islands and pick up some volcanic rocks and learn about the other thing, which is the composition of the Earth's interior. I'm not sure exactly why I was more interested in the rock part of it; probably because it gave me an opportunity to spend time outdoors on volcanic islands in the Pacific. [laughs] But that became my thesis work. Again, going back to something I said before, the key thing for all of this is that there is so little helium-3 in the Earth's atmosphere that you can see these tiny—I mean, in the scheme of things, the injection of helium-3 into the mid-ocean ridge is tiny, but you can see it, because there's so little helium-3 in the atmosphere.

ZIERLER: I'm just trying to think if we can possibly connect the dots historically. Of course, the Scripps Institution is one of the centers for the plate tectonic revolution in previous decades. Was there an infrastructure in San Diego that sort of had missions to the ocean, thinking about the mid-Atlantic ridge, things like that, that connected to the research that was available for you?

FARLEY: Yes. Scripps, at that time and still today, had a research fleet, and that research fleet was deeply involved in proving out plate tectonics. Also in acquiring deep sea sediments and trying to unravel what is recorded in deep sea sediments in terms of things like climate change. It's a big program that covers everything from physical oceanography—that is, the mathematical description of fluid flow—all the way to empirical observations of fluid flow of the type that I described. Then also—historically—I don't know how it acquired this strong program in isotope geochemistry, but that was applied to all sorts of things, including lunar rocks, which had of course nothing to do with the ocean. I think it's an example of when you start nucleating a strong group; it attracts other people with other interests because it's a hotbed of activity, and then you just go wherever your capabilities lead you. That I would say is probably where I—well, I'm certain—that is where I picked up the technique-oriented approach to geochemistry, where if you've got an instrument that does x, you do everything you can with that instrument. There were several different labs that were configured that way, that you could study the Earth's interior, you could study ocean circulation, you could study the Moon. The relationship between them is always you come back to the kind of measurement you make in the lab.

ZIERLER: I wonder if you could explain data gathering for your thesis. What came from field work? What did you do that was strictly laboratory-oriented?

FARLEY: Most of my thesis work was on rocks collected from volcanic islands, and many of those volcanic islands were not amenable to any detailed field work because they were absolutely covered with jungle with no trails. So, many of the samples that we collected were literally cobbles on the beach, which in some ways is a no-no; you should never collect cobbles, because you don't know where they came from. But it is basically your only choice. So, there was not a big field component, other than to collect those rocks. As an example, one of the major parts of my thesis was studying two small islands off the coast of Chile called the Juan Fernández Islands. I was on a cruise. We collected rocks from there, maybe 60 or 70 samples, many of which were beach cobbles, some of which were in cliffs exposed at the beach level. Brought those back, and the analysis must be made on olivine crystals. If you've ever looked at a basalt, it's typically a gray rock, and it very often has these green crystals that can be up to three or four millimeters across. Those green crystals are olivine. It's also the gemstone peridot. So, crushed up the rocks, separated out those olivines, sometimes picking them with a tweezers, which is quite a painful way to collect a gram of material. Each one of those crystals is like a milligram, so you'd collect a thousand of them with a pair of tweezers. Then, ready to do the analysis, we'd crush up the olivine. In vacuum. So we have a vacuum chamber, we crush it, and we purify the released helium and introduce it into the mass spectrometer to separate mass 3 from mass 4 and to quantify them. This is exactly the same methodology that we use in my lab today, so it's a pretty standard approach to liberating gases from bubbles which are in these olivine crystals.

ZIERLER: Returning to a topic from yesterday, the importance of instrument-building, the importance of really understanding the machine, not just using what is off the shelf to do the science, did you really develop that in graduate school, or does that come from earlier?

FARLEY: I felt pretty comfortable developing capabilities in the lab when I was a grad student, but where I really picked up the thing which was I think most beneficial is after I finished my PhD—which is in itself a saga—I finished my PhD and I took a postdoc at Lamont-Doherty Geological Observatory, which is part of Columbia University. There, I worked in a lab that was also primarily interested in oceanography, but they were very interested in automation. I just thought that was spectacular, because that completely resonated with my liking to play around with computers, and the very gratifying idea of telling a computer to do the work—so, much of my graduate work, I would have to, for example, come in both days of the weekend, turn a few valves, do a few little things. Then during the week I likened myself to an automatic sprinkler controller. You turn this valve, you wait a little while, you turn another valve. It doesn't make you feel great as a grad student if all you're doing is like looking at a stopwatch, turning a valve, when you could go to Home Depot and you could buy something that did that. Then when I went to Lamont, they had figured out how to make the computer do all of that. Which I loved. I was a postdoc there, and then I came back to California, got my job at Caltech, and implemented a lot of that. I spent a lot of time, actually, making sure that all of my lab could be as automated as possible.

ZIERLER: To go back to developing the thesis, do you have a clear memory when you had a compelling argument or a finding, and that this was going to be significant, what you were working on?

FARLEY: Yeah. There were really three different directions that I was working on. The work on mantle helium, I think it was useful, it was interesting, it was similar to what a lot of other people had found. I also collected and was given additional samples from Samoa. Samoa is a volcanic island chain. These rocks were very unusual, and they remain unusual to this day, in that they were absolutely filled with bubbles. That was really useful, because to measure helium, you don't need many bubbles. To measure other noble gases, you need much, much more. The reason for that is pretty simple. If you want to measure, say, neon—and if you thought helium was obscure, neon is even more obscure, but it tells a really interesting geochemical story. Unlike helium, the heavier noble gases—neon, argon, krypton, and xenon—are all gravitationally bound to the Earth, which means they are in relatively high abundance in the atmosphere. Why does that matter? It matters because if you are trying to see neon that it is in a tiny bubble, you are surrounded by a sea of contamination of neon in the air, and it is very hard to get rid of it. Helium doesn't have that problem, because helium is not gravitationally bound, so it doesn't have a high concentration in the atmosphere. These Samoan samples had enormous concentrations, and we set off to measure the heavier noble gases in them. Those were really the first window for understanding what the neon and the xenon—those turned out to be the most interesting things that we got out of it—what the neon and the xenon look like in the Earth's deep interior. When I gave a job talk at Caltech, that was the thing that people were most interested in.

ZIERLER: You said finishing the dissertation was a bit of a saga. Was that related at all to your mentor's style?

FARLEY: Yes. [laughs] Yeah. He was an extremely difficult person. When I started, there were about 12 people in the research group, and we joked that we all got our ration of shit, but because there were 12 of us, the ration was pretty small. By the time I was in my fifth year, it was just me. The whole group, for various reasons, had departed. So it was very difficult. He was hyper-critical, and very controlling, and did not like independence. I was actually trying to collaborate with somebody external to UCSD, and he did not like that. Anyway, we had this huge blowup, and I literally said, "The hell with it. I don't care if I don't get a PhD. I'm not going to put up with this." And I walked out. My fifth year. I felt like I had been so obviously wronged that I thought that the administration would come to my rescue.

ZIERLER: Did you go to the dean?

FARLEY: Yeah, went to the dean. The dean basically said, "You should finish your PhD with someone else, and whatever you produce, we will say is good enough." At that time, I had established a reputation as being a good student. People knew that I was doing okay. The story turns out to be relevant; it's not just complaining about the way I got treated as a grad student. So, I did that. I went and worked in another lab, and endured a lot of unpleasant interactions with Harmon Craig. Initially he said, "Hey, you can't use any of the data you generated in my lab; you can't use any of that for your thesis," ultimately—I don't know if somebody put the screws to him or what, but ultimately I was able to use it. But I was pretty discouraged. This is a story that I tell students who worry greatly about their personal relationships with their advisors and mentors—I was clearly in a very bad situation from that point of view, and even considered going to do something else. I looked around for where I might be able to get a postdoc. I basically finished my PhD—while I was doing that, in this other lab that I went to, I learned some additional useful new skills that served me well in the long run. But when I was looking for a postdoc, I applied to a postdoc at Lamont, and my reputation had preceded me, and a very well-known geochemist there named Wally Broecker, who was famous for having done a lot of the first work to understand the way geochemistry records ocean circulation and how you could show that the ocean had circulated differently—he's one of the first people, or maybe even the first person, that coined the phrase "the ocean conveyer belt," which is key to understanding the way heat gets transported on Earth. Anyway, he had heard about me, and he asked me to call him when I applied. He didn't do anything that was of direct relevance to what I was doing, but he said, "Anybody that is this much of a pain in the ass to Harmon Craig is okay with me."

ZIERLER: [laughs]

FARLEY: And he offered me a postdoc! Just because I was a pain in the ass to my advisor! That was the step that I might not have been able to make, that I did make, by just [laughs]—just by reputation.

ZIERLER: Being the last man standing out of the 12 graduate students until you had your own breaking point, what does that say about you? Is that just a higher threshold of pain? Were you not around because of all the field work? What might explain the fact that you were the last?

FARLEY: I was the youngest. [laughs] I was not able to move on. It turned out, and it's not an excuse, but Harmon had cancer, and he was slowly winding it down. He was an extremely difficult person so I'm not going to excuse him for it, but I did learn a lot, about how not to treat people. There's two ways you can go with this—what you might call the abused child syndrome, or you just say, "I am never going to do that." I definitely learned "I am never going to do this," in two ways. I'm not going to treat people that poorly. But also, I am not going to make science the only thing in my life. Because that's what it was. When he was in his closing years, he didn't have anything else. And it is very hard, and I will attest to this now that I am where I am right now and almost 60 years old, it is very hard to stay on the leading edge. I'm not sure why it gets harder as you get older. Maybe it's because you have more other kinds of responsibilities you've got to deal with, or maybe it's just when you're 25 years old, you've got a lot more energy, or something. But, you've got to be okay with letting it go. I watched both Harmon and actually several other well-known geochemists get to that stage and get bitter. Instead of saying, "Hey, I helped start all of this," it was more like, "Those people aren't giving me the credit I deserve for doing this or that!" It's unhealthy, super unhealthy. So, it was a useful lesson for me. The other lesson I got from it is, people that are sort of mean and nasty, they probably don't want to be that way. [laughs] They probably don't have any choice; it's just the way they are. Which I think served me well over the years, to just deal with people that were being difficult.

ZIERLER: Maybe it's a philosophical question, but can you be a great academic scientist if you're such a jerk as a mentor? Are those things so intertwined that it's impossible to be one without the other?

FARLEY: You have to be a jerk, or you have to not be a jerk?

ZIERLER: No, no. If you are a bench scientist and you don't have mentees, you can be antisocial and miserable and do great science. But for a professor, who is charged with running a group and mentoring students and shepherding them through the process, can you be considered a great scientist if the science is great but the mentorship is awful?

FARLEY: Unfortunately, yes. [laughs] There are plenty of examples of people who are—unreasonably difficult. I say that carefully, because there is a level of being difficult that is important. To be a scientist, you have to be tough. There's no choice. You have to be, because people are going to challenge your ideas. If you wilt when somebody challenges your ideas, you're never going to succeed. And, you have to work hard, because there are other people who are going to work hard, and if you're not going to work hard, unless you are brilliant—which most people are not—you gotta have something. Sometimes that's hard work. Sometimes it is just committing a huge amount of time. Those things are important, and an advisor has to basically say, "If you want to succeed, this is what you have to do. If you don't want to play this game, you can get your PhD and you can go do something else. But if you want to be an academic scientist, this is what it takes." There's a level of doing that.

Then there's the level of—I definitely saw this when I got to Caltech—another famous geochemist with a very similar background, and a very similar personality, being a very difficult person, Gerry Wasserburg—probably even more famous than Harmon Craig—extraordinarily difficult man. When I arrived, Caltech's GPS division was in a very challenged position. It had a reputation, especially in geochemistry, for having intense infighting between fiefdoms led by professors. I arrived, and I was the only untenured faculty member. For the entire time I was an untenured faculty member, I was the only untenured faculty member in the GPS Division. I got tenure before we hired somebody else, so I was on my own figuring this out. I actually think it served me really well when people like Wasserburg would come in and say nasty things to me. I would just shrug my shoulders. I had already learned how to deal with this. By far, the way you deal with it, you don't gratify it. You just ignore it. If somebody wants to come and insult you, you just [laughs]—just go on about what you are doing. Unfortunately you can be extremely difficult and get away with it, if you are really good.

ZIERLER: Maybe this is more of a generational question, but academic culture today, it at least strives to be more sensitive to the student experience, that there are more resources available when there are these challenges. The behavior of your graduate mentor, were these the kinds of things that just wouldn't fly today, or unfortunately, would they, because they're not like sexual harassment, or racism, or the really overt redline stuff that absolutely wouldn't fly today? How would you understand that, if these were the kinds that you were coming up on circa 2022?

FARLEY: I think a lot of them would be allowed to continue. I think there might be more attempts to steer people away from doing that. But for better and for worse, a tenured faculty position, once you have tenure, if you are succeeding, it is very hard to redirect what a successful professor does. There are very few levers. Now looking at it from the administrative point of view, there are very few levers to do that. Perhaps the only lever that is obvious is that when you write a research proposal, you have to explain how you are going to mentor students, and how you have mentored students in the past. I have yet to see that people that are difficult get penalized in review. If they come in with a great idea, and a great track record for turning their ideas into important products, I think they still get rewarded. I do worry about that. It's not a great situation. There are definitely people who push very, very, very hard, and sometimes they produce fantastic students. I have heard people say that this is necessary, this is the way you create a fantastic student, is you put them into a very difficult situation, and you force them to perform so they learn how to do it.

ZIERLER: Yeah, but difficult is not toxic. There is a difference.

FARLEY: That's true. You can definitely go too far.

ZIERLER: The road not taken, that dramatic moment when you thought maybe you would just leave the program altogether and not get your PhD, do you have any idea what you might have pursued? Would you have left science, also, maybe?

FARLEY: Probably not. I don't know what I would have done. What I was looking at, at the time, was something like environmental consulting. I'm very glad I didn't go that route, but that would bring together in a similar sort of way the things I was interested in, which is outdoors, environmental stuff, and chemistry.

ZIERLER: The educational trajectory—Yale, San Diego, then postdoc at Lamont—where is Caltech in all of this? Had you considered Caltech as an undergraduate, graduate, or postdoc? Did you visit? Were you aware of its reputation?

FARLEY: I didn't know a whole lot about it, because the direction that I was looking, when I was a graduate student, areas that I was most interested in, were oceanic rocks, so islands on the ocean or rocks on the sea floor. In terms of isotope geochemistry, the folks at Caltech, very well-known isotope geochemists, but they were not primarily focused on that. There were people like Patterson, very interested in meteorites. He then also became very interested in lead contamination of the environment, so not something I was very close to. Lee Silver, super interested in the geochemistry of the continents. Same with Hugh Taylor. Wasserburg was interested in meteorites and the Moon. So, they were not really doing the things that I was paying attention to. When I finished my PhD, by that time I was engaged, and my wife was also a graduate student at Scripps. She wasn't quite finished, but she moved with me to New York. We packed all our stuff up in my pickup truck, and we drove out of San Diego, and then up I-15 through Cajon Pass. As we were going up Cajon Pass, we both said, "We are never coming back to Southern California." I look back on that, and it's sort of ironic, but the reason I said that is, one of the things that was amazing and very sad is when I started as a graduate student—I sound like a really old guy—when I started as a graduate student at UCSD in 1987, all of North County, San Diego, was open land. It was great! You could ride your mountain bike everywhere, and you could park near the beach. By the time I finished my degree in 1991, it was all built out. It was like this sea of condos and traffic. It was so overbuilt. Then the graduate students couldn't afford to live near the beach, and so we were having to move farther and farther east and commute. Anyway, I hated that, and it just seemed like Southern California was just sprawl everywhere. I said, "We are never coming back [laughs] to Southern California." This position I had at Lamont was a five-year position, and I had been there only a few months when Ed Stolper called me and said, "You should apply for our job." I knew a little bit of Caltech's reputation at that point. I talked to my advisor at Lamont, this guy Wally Broecker, and I said, "I don't think I'm going to apply." He looked at me like I was an idiot, and he said, "Absolutely you need to apply. You don't have to accept the job, but you need to apply."

ZIERLER: You thought you were not ready for it?

FARLEY: I did not want to go back to California, and I did not want to deal with any more assholes. I was perfectly happy. I had just started. My wife and I had actually just bought a house in Bergen County, New Jersey. And, she was pregnant. This did not seem like a great thing, to just pick up and move, and I was not that keen on moving her, again. But I decided, "Okay, I'll apply." I got invited out for an interview, and it was very memorable to me that it was in the middle of March. New York in March is gray and muddy, and there's no leaves on the trees [laughs], and March in Los Angeles is beautiful. Everything was green, and Pasadena is not the creeping sprawl of a lot of Southern California, so I really liked it. I got toured around, and Caltech looked like a pretty good opportunity. I had a really good opportunity, and then I got offered the job and wound up taking it.

ZIERLER: Your explanation for why Caltech wouldn't have been an option during your educational trajectory, emphasizing that it was really not part of oceanographic research, I wonder if you appreciated the history that Frank Press, for example, coming from MIT, tried to get the Seismo Lab—and that Caltech, in its Caltech way, said, "That's not our thing. We're not going to do that." I wonder if you appreciated that self-consciousness to the kinds of things Caltech would get involved in, and the ways that it wouldn't, and if that weighed on your decision-making in terms of joining the faculty where you had all of these oceanic interests in mind but maybe Caltech wasn't going to be as centrally involved in that as you may have needed it to be.

FARLEY: Right. As I mentioned the last time, I was worried when I accepted the job that the only person that was working on things that were similar was Ed Stolper, and maybe a little bit Wasserburg, but I already knew I didn't want to have much to do with Wasserburg.

ZIERLER: His reputation preceded him. You knew about his personality?

FARLEY: Oh, yes.

ZIERLER: Because that was just known in the field?

FARLEY: Oh, yes. I have often pondered why the handful of really great isotope geochemists of that generation were all extremely difficult people, but they were. His reputation was well-known. In any case, the interesting thing that happened to me after I arrived is I had started—I built my hammer; I built my lab—and was then looking around for, what else could I do with it? I already told you I got involved in looking at the cosmic dust on the sea floor, which originally was to get at this question of where this helium-3 coming out of volcanoes actually originated, but then turned into looking for major events in the history of the solar system. I also got involved in dating these apatite crystals to learn about the formation and history of topography, so the formation of mountain ranges, working largely with Lee Silver. Those are things that I don't think I would have done had I not been exposed to the big diversity of things that happen at Caltech. The difference really was a lot of the people that I worked with at Scripps, they were completely focused on working on the ocean, and they didn't work on the continents. That's why it didn't occur to me to work on the continents. But then I got to Caltech, and there were a lot of people working on the continents, and a lot of interesting things happening on the continents [laughs]!

ZIERLER: When Ed Stolper first reached out to you—I don't know if you ever talked to him at the time or later on—how he became aware of your work? Was it really well-cited at that point? Were you giving a lot of talks? Would you have been known?

FARLEY: No. I know a couple of things about it, because Ed tells the story, and Ed is a—he remembers everything.

ZIERLER: Yes, he does. [laughs]

FARLEY: What he told me was that—at the time, when I got hired, I only had two publications, and I had not given a whole lot of talks. But I guess Ed had either a grad student or a postdoc named David Bell. Ed struck up a conversation with him after an American Geophysical Union meeting and said, "David, did you see anybody interesting at the AGU meeting?" David mentioned that he had seen me. Ed looked me up and decided that he should encourage me to apply. So, it was purely because David Bell put in a good word for me.

ZIERLER: When you got here, tell me more about, first of all, the job talk. What was asked of you? I know that Caltech, when they are considering a new faculty hire, they want to see, is this going to be a faculty member who is going to make a massive impact on the field. Were you aware of that expectation? How did you respond to it?

FARLEY: Fortunately, I came in with a very low desire for the job. As I told you, it was, "Yeah, okay, I'll learn how to play the game." That would be my first real job interview, or my first faculty position interview, so—"I'll just learn how to do it." I was asked to give two talks, which I think is pretty standard. That was straightforward, for me to take the two chapters of my thesis that were most straightforward to explain, and work through it. I went and talked to each of the faculty members. I did not talk to Wasserburg, because Wasserburg was on sabbatical, but I did talk to a whole bunch of other people. It didn't feel like they were—testing me, but I also felt like when we did—typically, the way these things go, much more happens in the one-on-one conversations in people's offices than when you're giving the job talk. And it definitely felt like they were wondering, "Okay, this guy knows how to measure noble gases, but what's it good for?" This is sort of the corollary of, I was working at an oceanographic institution where people knew very well what you do with helium-3, I show up at Caltech, where people are not doing that, and they're like, "Well, why would you want to do that? Maybe you should do something else." So there was a fairly deep skepticism, and Ed also told me that it was expressed very clearly, like, "This is not a growth field. This is not a field that you can expect this person to work on for very long, so you better test them and see if they are interested in other things, so that when they run out of things to do with measuring helium, [laughs] they could still do something useful." I do remember that kind of conversation, like, "Well, what are you going to do in the long run? What do you want to do in the long run?" I think like most people, I had no clue what I wanted to do in the long run. I didn't arrive with something that looked like a research program that could last more than a few years. But apparently that was not enough of a negative. I think they must have discerned that I could at least hold my own for a few years, and then after that, it is definitely the general structure of the way that Division works and continues to work to this day is, don't try to pin people down. Don't assume you know anything about what they're going to do. This goes to the thing that I was saying yesterday, that you put people in an environment and give them opportunities and give them resources, and then you just watch where they go. You don't try to tell them where to go. They will go to wherever there is something that is interesting, if you have selected the right person. That's definitely what it felt like for me, that I had a tool that would keep me going for a while, and then I just went off in all these different directions. I still happened to use the same tool, which was very convenient. That's basically how that worked.

ZIERLER: So, just into a great postdoc, you buy a house, baby on the way; why ultimately did you pull the trigger? Was part of the attraction the difficulty in going to Caltech and forging this on your own, and having that lack of certainty from the other faculty members? Was that attractive as a challenge to you?

FARLEY: There was a little bit of that. There was also something that was very obvious—that this was the big league. This is the job offer, in terms of being able to start my own lab, with very little postdoc experience. Being a postdoc is a scary time, especially when you're married and have a kid, because you've got this responsibility to a family, and also thinking this is the step, this is the really big step that you make, that you either stay in the field and—it sets where you're going to go in the long run. This offer was as good an offer as I was ever going to get, in terms of being able to start my own lab. So, it just looked like it was the right opportunity. By that time, I had also begun to see that Southern California wasn't so bad. The thing that was bad, that I did not like about it, is—and I think this probably remains unfortunately true—being a grad student, you don't get paid enough to not be kind of miserable. As a faculty member, you at least have a hope of having a nice home, and not having to commute long distances. I feel very fortunate that I started at Caltech before it just became impossibly expensive, so until about ten years ago, I lived probably two thirds of a mile from campus and every day, I biked to work. You can't beat that. That was great.

ZIERLER: You sold the house in New Jersey right away, or you hedged your bets, you hung on to it?

FARLEY: I finished a year of that postdoc, partly to allow the lab to be renovated, which is an interesting story that I'll tell you in a second, and also for the instrument that I needed to get—they're purpose built, and they're built on demand. Both of those things needed to be running in parallel with my finishing up the postdoc. So, I stayed probably a year in total, so another nine months after that, which meant my first son was born in Bergen County, so he's a New Jersey boy. We drove across the country when he was three months old.

ZIERLER: [laughs]

FARLEY: There's a funny story that the lab space that I was allocated was on the third floor of North Mudd. It's not a lab anymore; it is now offices and a hallway. At the time, it was Clair Patterson's clean lab. You know Clair Patterson's story?

ZIERLER: Of course.

FARLEY: His clean lab was his sanctuary, and it was, as he claimed, the cleanest place in the world, for lead. He had an office right across from that lab. So I show up, I'm walking around through the lab—I guess he was retired, or at least not working in the lab anymore—but he was clearly not happy that I was taking over his lab space. So, he started out as—he was not a fan. He was not a fan of my coming. Ultimately, it was fine. There were a lot of barriers in that lab to keep the lab clean, but what was fascinating is when they pulled those barriers out, everything was rusted and falling apart. Which is a very common problem, as I have come to understand, in clean labs—that there's a lot of acid vapor in those labs, because you dissolve things, like rocks. The trick is to keep all that rust and stuff contained. But once they started pulling down the walls, the walls were all falling apart, which is sort of odd. I have two other interesting stories to say about Clair Patterson. He was a very unusual person. I don't remember when he died, but he was clearly withdrawing at that point. I went to my first faculty meeting, which was probably three months after I arrived, and I'm sitting around with the other faculty members in the Buwalda Room, and we are in the middle of a planning exercise, these things you do every five or ten years, where you go around the room and people talk about what area we should be studying. I'm sitting there, and it was very interesting to listen to people say, "Oh, we should do this kind of seismology" or "We should do this kind of geology." Then it came to Clair Patterson, and he stands up, and he said, "You have got it all wrong! We should be studying the human brain!" And then he sat down. And I'm like, "What!? He said we should study the human brain!" [laughs] Later, I went and asked Ed, "What was that about?" He said, "Oh, that's just Patterson. That's just the way he is." He definitely thought we should all give up doing any kind of Earth science and we should all study the human brain. Which was quite weird. The other thing that happened is while I was inspecting my lab as it was getting built, his office was right across the way, and I could hear him shouting into the telephone, "I don't want your award! I don't want an award!" He had been offered some award for having the most highly cited paper ever in Earth science, which is the "age of the earth" paper, and he was shouting that he didn't want an award for it. Like, "Okay! [laughs] I get it. This is a very unusual person."

ZIERLER: When Dave Stevenson said this amazing thing to you about, "Just name your number," what was your response to that? Did you ask for more than you otherwise would have? Did that put more pressure on you to get it exactly right? How did you respond to that open-ended invitation?

FARLEY: It was a huge relief, actually, because I understood what I wanted, and the hardest part, by far, when you're trying to set up a lab, is you can think of the big-ticket items, but what is very hard to think of is all of the little things that, if you were in an existing lab, they have, or they can borrow from somebody. I was having a hard time making the list of all of that stuff, so to not have to worry about it, to basically just put in a number that would cover it, was great. I didn't change what I asked for. I asked for a single mass spectrometer, and the components for a vacuum line. Back in those days, the big-ticket items, you also got co-funding from NSF, so I wrote an instrument proposal which ultimately got funded.

ZIERLER: Whose space did you take over, or was it a new building?

FARLEY: That space was Patterson's space. My new lab went into Patterson's space. I stayed in there for, oh, I don't know, six or seven years. The interesting thing that was happening at that time was that there was a big collection of really important geochemists, and they were all retiring, or dying. Patterson retired, Wasserburg retired, Silver retired, Epstein retired, Taylor retired, and all of their space became available. When we hired John Eiler, John was looking around for space, and he and I together decided we should co-locate our labs, as the two young geochemists. That's how we ended up in the basement of North Mudd is, "Let's just share a big space, and take advantage of things that we will need together." For example, I bought all the tools, so there's a giant tool rack down there, and if you need tools, it's all there. It's more of an intellectual thing, actually, to always have people around. That was very different than much of the way geochemistry worked in the fiefdom era, where it was sort of legendary that Gerry Wasserburg put a door in the hallway in front of his lab, because he didn't even want people anywhere near his labs. You could come in and work in Gerry's lab, you'd go through this door in the hallway, and then you'd never see anybody until quitting time, so you never had to interact with anybody who wasn't part of the lab group. We were definitely trying to break that mold by now having a big shared space, which now Alex Sessions is also part of.

ZIERLER: This faculty response that maybe your area of expertise will keep you busy for a few years, did you agree with that? Did you defer to the gray beards? Or did you say, "No way, there's way more here than you are appreciating"?

FARLEY: I wasn't told that until probably about the time I got tenure [laughs], so I didn't have to know what people were saying. But I got pretty lucky, I think, in that the two new things that I worked on, which were this cosmic dust thing, and the helium in apatite thing, pretty clearly within the first few months of working on them I could see that they had a lot of opportunities in them. There were a lot of different directions to go. And, for both of those fields, for many years, I had the field to myself. There was nobody that was geared up to do it for any number of reasons. It was different than I think a lot of the way junior faculty get started. They come up with a good idea, they start something, they write a paper on it, and pretty soon other people are competing with them, and it's hard to build on it. I had the luxury of many years, and still today on the cosmic dust measurements, that there are very few other people that could do it. So, I don't have to rush. I can lay out a plan and not worry that I'm going to get scooped on it.

ZIERLER: Did you set up your lab in a way where new research opportunities would be easier to take on? Or in the assistant professor years, is the idea that you should be hyper-focused, and you should make your mark in this particular area?

FARLEY: That is a common question. Are you better off really nailing something, or being diverse? We always advise the junior faculty, "You have got to do something great in one field. If you are just average in a whole bunch of fields, that's not going to be good enough." I don't know that I really thought about it. Because one of the things I got told, probably by Dave, and probably by Ed, is, "Just do you thing. Do not worry about tenure. It's not going to help. Just go do your thing. If you need help, you need resources, you need advice, we are here for you." That I think is a really good piece of advice. If you try to game out what it is going to take to gain tenure, I don't think it's helpful. I did have a little bit of a panic in that this purpose-built instrument took a year to get manufactured. The first thing that happened to it was just before it was going to be shipped, something bad happened in the factory, and they had to start again.

ZIERLER: Oh, no!

FARLEY: They expedited it, but it still came about six months late. I was freaking out, as a junior professor will do. The clock's running, and I'm not doing anything. What I wound up doing in that time, I had all these vacuum lines and the computers getting ready to go, and I spent six months writing code to automate the lines, automate the lab. Remarkably, we are still using a lot of the pieces of that code. It's something I never would have done otherwise. If I had had the instrument, I would have cobbled together some good-enough code and then started analyzing samples, because that's how you make your mark. But it turned out to be quite beneficial to invest the time in the automation, because you harvest the benefit for years and years and years after you do it. So, if you're going to automate something, automate it at the beginning, not at the end. [laughs]

ZIERLER: That's some serendipity, actually. It worked out that it was delayed.


ZIERLER: In terms of staying focused, what was the game plan? What was there to build on from both your thesis and what you had done at Lamont up to that point?

FARLEY: The thing that I continued to work on, which was the thing that was most obvious—I continued to work on those rocks from Samoa, made some additional measurements on them. But I think from the perspective that I just mentioned, where people thought, "Hey, you're going to run out of things to do," that is indeed exactly what happened, in that I couldn't see how to make the measurements any better, because these were an unusual set of rocks that didn't provide any information about how you would find more such unusual rocks that had lots of bubbles in them. It was not obvious how you would ever set out to find more of those. So I think I came to my own realization that after a few years of doing this, I had done pretty much what I could usefully do. I was very glad to have these other two projects take off pretty quickly.

ZIERLER: Which projects? What were these?

FARLEY: Looking at cosmic dust. Shortly after that is when I had the interaction with Don Anderson, with Gene Shoemaker, and was off and running on that. Then, for working on these apatite crystals, it was kind of an interesting interaction about that. I was working with Lee, and Lee was sort of a grand old man. Even at that time, he was a grand old man. He only died I think last year, at some very old age. He had this collection of mineral separates. It's sort of surprising, but one of the biggest impediments to studying rocks is the need to separate out pure minerals from rocks in which they are in low abundance. This mineral apatite, it's about 100 microns across, and it probably constitutes a tenth of a weight percent of a granite, but you have to separate out that mineral if you want to work on it. Lee had invested many years of his life doing those mineral separations, so he had this room that was filled with little bottles of apatite grains and zircon grains and titanite grains, and they were just all up on acks on the walls. I sort of felt like I was humoring him when he would say, "Ah! You could analyze these rocks!" It didn't seem that interesting to me.

But then I met the student who became my first graduate student. The details of this don't matter, but he was working on a problem that involved looking for fission tracks. Fission tracks, it's a very unusual decay mode in uranium. Some very tiny fraction of uraniums, instead of emitting alpha particles, they fission spontaneously; just like uranium-235 does in a nuclear reactor, except for it does it spontaneously. The student was looking at apatite grains. He was working with Brian Wernicke. He was looking at apatite grains that have these fission tracks in them, and he was using it to date the crystals. I had never done any kind of dating at that point. I walked by, and he introduced himself to me. His name was Richie Wolf. He introduced himself to me and told me what he was doing. He says, "I'm looking at these apatites, and I'm counting the fission tracks to figure out how hold this apatite is." I had never heard of this. I went back to my office, and I had literally just been doing a calculation where I needed to know, when uranium decays, how many alpha particles does it make compared to xenon isotopes that it makes, and the xenon is made by fission. I just literally had been doing this calculation about the ratio of alpha production to fission decay of uranium, and here is this student who is counting the fissions, and it pops into my head, "Wow. There's ten orders of magnitude more alpha particles than there are fission tracks. If he wants to date that by counting the fission tracks, he should just measure the helium." This was my introduction to helium dating, which as I told you before had been proposed long, long ago, and it had never been made to work. I went back and I talked to Richie, and I said, "Richie, maybe we should try to measure the helium in these. It's super easy to do this in my lab." We went down and found Lee Silver, who had this trove of apatite crystals. We said, "Hey, we want to see if we can date them." Lee had a great idea. He said, "Let's go look at Mount San Jacinto." If you know San Jacinto, it's a big mountain right outside of Palm Springs. Have you ever gone on the tram that goes up the side of Mount San Jacinto?


FARLEY: It's fabulous. You ascend from probably just around sea level up to 9,000 feet. It's this sheer cliff, made out of granite, that Lee had sampled many years ago and had separated out apatite. I didn't really know why Lee picked this place for us to do our first project on, but he did. We dated those, so we measured the helium and the uranium, and it's easy enough, if you know the decay rate, you know how fast the alpha particles are being produced and you know how much is there, you get an age. From six or seven samples on this slope, this cliff on the side of Mount San Jacinto, it was obvious that there was something important going on, because if you plotted the sample He ages against elevation, it was a perfectly straight line, with the oldest sample at the top being something like 50 million years, and the youngest sample at the bottom being something like 20 million years. Perfectly straight line in between. Nature doesn't make straight lines if there isn't some basic phenomenon that's important. That basic phenomenon is that that mountain is being levered upward, and the apatites that are at the top of mountain cooled and started retaining helium before the ones at the base. So, you actually get information on when and how fast that mountain range was being produced. It was a fabulous success, right from the get-go. Richie did his thesis on that.

But there's an interesting thing that is commentary on the way the world works. I wrote a proposal to do that, to develop this method, which fortunately, I was very ignorant—totally ignorant, actually—of the many fruitless attempts to use this method to date formation ages. We're not getting at the formation age of those rocks; we are getting at the cooling history. Previous work had been trying to get at the formation age, and it was disastrous. It was not useful, because everything was too young. I wrote a proposal to do this, to the geochemistry program at NSF, and it did not fare well in review. I still have it around somewhere in my office. One of the reviews said, "Farley is dumpster diving." I'm like, "Ooh. That's not good." It didn't get funded, so I was kind of discouraged. I ran into Brian Wernicke. Brian is a geologist. He just recently retired. I told Brian what I was interested in, and he thought about it for a minute, and he said, "I have a great idea. We are going to go and study the Sierra." And he wrote a proposal to a geology program at NSF, and basically said, "There's this new method. We don't know if it works, but it might answer this question that people have been interested in for a hundred years: how long has the Sierra been a high standing mountain range?" There's a lot of reasons why people have asked this question, and I'll get to the answer in just a minute. So, he wrote this proposal, and instead of being reviewed by geochemists, who are all super skeptical of each other, it went to a bunch of geologists who said, "Well, I don't know if that can work, but if it can, it's really important." And, it got funded.

We then embarked on this study of the Sierra, which involved a serious helicopter assault, all the way from the area around the Kern River, in the very southernmost part of the Sierra, all the way up past Yosemite, the helicopter going into wilderness areas and national parks, so there was a lot of permitting that was required to do this. But we analyzed those samples, and they basically showed the kind of pattern that Brian had predicted we would see if the Sierra were old. Basically what we were able to show is that the two biggest canyons in the Sierra, which are Kings Canyon and the San Joaquin River Gorge, those are very deep, very wide canyons, and they have been there for at least 60 million years. The only way you get a deep wide canyon like that, you have to have a river that is cutting into the rock, and the only way a river can cut into rock is if it is high-standing. You don't form a canyon below water, under water, or under sediment. That demonstrated what is now widely accepted, that the Sierra in the distant past, so 60 million years ago, were not necessarily a mountain range, but they would have been the leading edge of a high plateau that extended all the way from the Sierra to the Wasatch Mountains outside of Salt Lake. This was a high plateau, much like the Altiplano in Peru, that has since collapsed. Anyway, it was a super interesting experience for me to collaborate with somebody who knew what to do with a method. This is one of the things that I have really enjoyed that I mentioned yesterday, that it's fun messing around in the labs, thinking, "Can I do anything with this?" and then discovering people that have good ideas, like Lee's idea to go look at Mount San Jacinto, and then Brian's idea to do it in the Sierra. You get brought along for the ride. For many years after that, I was collaborating with people from all over that had similar sorts of ideas, for things to try. That was great. That was a really fun experience.

ZIERLER: The concern that maybe you would run out of stuff to do in the way that you initially set up your lab, did that influence your ability or willingness to take on graduate students, where there is that five-year commitment to keep them busy and not run out of problems to solve on? Or did branching out into these new fields make those concerns go away?

FARLEY: The biggest stressor on a junior faculty member is the inevitable uncertainty of when funding is going to run out, and you absolutely cannot live your life that way. You just have to say, "Something good will happen." I definitely felt that. The biggest place where I saw it when I was trying to hire a lab tech or a lab manager—"I can't commit to you because I only have funding for the next two years." Well, that's a real turnoff [laughs] when you're trying to recruit somebody, to tell them, ‘Well, you might have a job for only two years.'" You just have to get good with assuming that it's going to work. This is definitely advice that we give to junior faculty members—"Do not worry about this. If you have a shortfall in funding, we are here for you." I definitely got that. I didn't need it, but I got the reassurance. So, I didn't really worry about that. I did not have, and have not had, many graduate students. I have always worked with a small number of students. I think the total number of people who would identify themselves as my graduate students is probably 12 or 14, or something like that. I have always run a relatively small group.

ZIERLER: The older designation at Caltech—when you became associate professor in 1997, is that tenure? Is that what the associate professor meant at that point?

FARLEY: No. I came up for the midterm review—you get an initial—I think it's a four-year contract, so you come up at the end of your third year. I was promoted to associate professor, without tenure, but then I got tenure the year after that.

ZIERLER: Is that standard? Like at Harvard, associate does not mean tenure. Is that how it was at Caltech, also?

FARLEY: No, that was unusual even at that time. It was for some sort of practical reason that happened. I don't know why it happened that way. [laughs] Anyway, it came quickly, and so I got through the tenure period without [laughs]—in unusually short order. Partly—and this is just honest—this is something that is very hard to do when you have multiple junior professors, because they are all competing with each other in some way. But as I said, I was the only one, and so there was no, like, "How is so and so going to feel if we give this guy tenure?" It doesn't happen very often, but it was a moment in time where it worked.

ZIERLER: Where was John Eiler in all of this? As you explained, you were sort of the two young guys at that point. Had he already gotten tenure?

FARLEY: No, he started probably right about then, right about 1997. He was a postdoc working mostly with Ed, and we were watching him, thinking, "Yeah, he probably would be good for us to hire." We let him search for jobs for a long time before we hired him, but it was a good hire. He's a great colleague.

ZIERLER: Now, this vow that you asked Ed Stolper to make, that he was not going anywhere, what was the timing of that? Was that before you got tenure?

FARLEY: That was before I even accepted the job!

ZIERLER: I see. When you did get tenure, did that open up the kinds of things you'd be able to work on? Did that free up those concerns about achieving great things in a specific area?

FARLEY: It didn't really change anything that I was doing, because I think I did believe, when I got told "Don't worry about it"—it was definitely for sure a nice pat on the back, but I don't think it felt like, "Okay, now I can do other things." I was already doing—I don't think I changed what I was working on at all.

ZIERLER: Was there a job talk for the tenure decision?

FARLEY: No. It would be relatively unusual for that to happen, at least the way that we work.

ZIERLER: How was it communicated to you? Division chair, provost, how do you get the news?

FARLEY: I must have heard it from the division chair. I don't actually remember.

ZIERLER: Clearly did not leave a mark, though. Not a big deal.

FARLEY: No, no. Like I said, it was nice, a nice pat on the back.

ZIERLER: At this point, by the late 1990s, where is JPL? Is it already on your radar, or when does that happen for you?

FARLEY: I did not work at all with JPL until at least ten years later.

ZIERLER: Oh, wow, okay.

FARLEY: I don't remember for what purpose, but I went up to JPL, and there's a really big difference between the feel of the Caltech campus and the feel at JPL, not the least of which is you can't even get on JPL without having a badge, and if you don't have a badge, you have to get escorted everywhere. Honestly, that is a challenge, and it's kind of off-putting. So, my first few experiences there were a bit off-putting. I kind of like it where you can just wander around down the hallway and not worry about having a badge. Culturally, it's so strange, that we're a single institution, and in one place, we walk around and talk freely, and in another place, there's a lot of locked doors, and you can't get on the lab. It's culturally very different.

ZIERLER: In the late 1990s, as we did a tour of your research agenda, where there's the mantle, there's the atmosphere, there's the sea floor, had that been pretty much set at that point, that you were focused on these three areas, or what was not yet part of your agenda at that point?

FARLEY: That's about right, that those were the main things I was interested in. I wound up at about that time—actually it was in 2000, because I remember I took a sabbatical—I took really my only sabbatical in 2000, and I went to the University of Melbourne. I met somebody there who became a collaborator that I still work with to this day, who is very interested in dating of iron oxide, which is something that had not previously been datable. If you go especially to the tropics and you see red soil, that red is all iron oxide. It's a very insoluble phase. The reason you get those red soils is, everything that can dissolve does dissolve, but the iron oxide stays. I had started working with Paulo Vasconcelos on that. That then started a whole new research direction, where I got interested not in deep-seated rocks that come to the Earth's surface, but what is actually happening at the Earth's surface. That has two different components to it. One is the uranium-helium method, so the iron oxides accumulate uranium, or have uranium, and they accumulate helium, so we can date them. The other thing which we found along the way, more or less accidentally, is that those iron oxides also have helium-3 in them. You wonder, why would they have helium-3 in them? The reason they have helium-3 in them, which is now very clear, is when a rock is within about one meter of the surface of the Earth, it is subjected to irradiation by cosmic rays. Cosmic rays are high-energy neutrons—at least at Earth's surface they are neutrons. That's not true in space, but at the Earth's surface, they are enormously energetic neutrons, and when those neutrons collide with target nuclei in a rock in the uppermost meter, they will shatter the nucleus that they interact with, and one of the particles they make is helium-3. This has been known for a long time. Actually this cosmogenic 3He was discovered in rocks in the the lab that I was in as a grad student, while I was there, in about 1986,

What we discovered is that these iron oxides also have helium-3 in them, and we use it to date how long they've been at the Earth's surface. That led to what I think is one of the coolest things that we found, which people still scratch their heads at. Everywhere on the Earth's surface above sea level is either eroding or being sedimented. It's just the way it works. If you are above the area of sedimentation, water flows across the surface and erodes. If you are below that region, you get sedimentation. People have studied erosion rates using this production of isotopes by cosmic ray irradiation. I hope it makes intuitive sense that a rock—here's the easy example that people use, and some of the work that we did, unrelated to what I'm talking about right now. So, a boulder in a moraine. If you want to know when that moraine was produced, you can essentially translate it into a question of, when did that rock first get exposed to cosmic rays? Because that rock was born somewhere deep in a mountain, and a glacier plucked it out and pushed it to the front, and then the glacier retreated and left those boulders there. If you could determine the cosmic ray age, you can determine when that moraine was produced.

I did some of that work. I had several postdocs working on that. Then I started working on these iron oxides, because that tells you about something different. That tells you about erosion rates. People had looked at various places for, where is the lowest erosion rate on Earth. That's really not the way it's phrased, but as an ancillary thing, people had come to accept that the two most slowly eroding places on the entire Earth are the Atacama Desert, where there are places where it has never been recorded to rain, so it's hyper arid, or in the dry valleys in Antarctica, which is hyper arid and super cold, so there is no liquid water possible on the surface. It's frozen pretty much all of the time. We got involved in looking at the erosion rate of these iron oxides in Brazil, and we went to an iron mine right on the boundary between Bolivia and Brazil. It is this high-standing plateau. It sticks up 200 meters above the surrounding jungle. It's very weird. It's the Paraguay River Basin. It's a very prominent plateau. We established that the erosion rate of this plateau is the lowest erosion rate of anywhere in the world, much lower than the Atacama Desert, much lower than the dry valleys. That is just because the way erosion works in those kind of environments is the rainwater falls, and anything that can dissolve does dissolve, but the iron oxide is so insoluble, it just sits there. Which was a really interesting discovery, because then it explains why these plateaus are standing. There's a whole bunch of these plateaus in the tropics, and this is the way they get produced. They get this cap of absolutely insoluble iron oxide on the surface, and then because the rainwater can't do anything to it, can't dissolve it, it just sits there. These turn out to be important because they are the major source of iron ore. The world's iron is mostly mined on these plateaus. [laughs] So, interesting contrast. Anyhow, I did get involved in a completely different sort of direction that I continue to work on, which is learning about the geomorphic evolution of the Earth's surface using both cosmic ray irradiation and this technique for dating the formation of the iron oxides.

ZIERLER: You mentioned computers of course were important for your lab at its inception. What were some of the computational advances, circa late 1990s or early 2000s, that might have allowed you to do either new things or the same things better?

FARLEY: Much of what I do does not require really high-end computation. What I do is not driven by that at all. But the thing that has been enabling for me is the ever-increasing ease with which you can interface hardware to software. Being able to automate the lab in the early days, you had to know a lot about—you'd get a little terminal strip at the back with a bunch of wires, and you'd have to figure out, like, where do I put this wire, and how do I tell the computer to put a voltage on that wire. All of that stuff has gotten super easy today. It's literally plug and play. You get the thing, and you plug it in, and there you go. That has made life a lot easier. But not a lot of computation, really.

ZIERLER: You mentioned you have to hope for the best in terms of funding. Around the time you got tenure and shortly after, what were some of the big shots in the arm in terms of getting the support that you needed to do all of this work?

FARLEY: Absolutely the Packard Foundation Fellowship. These are spectacular. I don't know if there's anything else like it.

ZIERLER: Do you know if they have a long history with Caltech?

FARLEY: Yes. Do you know about Packard Fellowships?

ZIERLER: I've heard of it, but I don't know much.

FARLEY: They're worth knowing about. I can't remember how many they give out. It might be something like 40 a year. They're called Packard Fellowships in Science and Engineering. At least that's what they were called; I don't know what they're called anymore. They still have them, for sure. They interact with something like 40 major universities that do research, and they let those universities identify their top two candidates. So, it isn't open to just everybody. There is an internal competition within those 40 institutions. And the pressure to nominate the best people, which you can imagine across all of science and engineering at Caltech is very competitive. You have to be, I think it's younger than 35, something like that, and less than five years after starting. It's definitely a young person, junior person, award. They let the universities do the first-order cut. Then, I don't know exactly how they do the next one, but in my memory, Caltech has always gotten one of those. I got that in something like probably 1997. The thing that's really great about these is they just give you a chunk of money. They don't ask for a detailed explanation, a budget. You write a proposal, but it doesn't have to have all of it. Writing a federal research proposal, it's just all these things you have to have, and then you ask for a certain amount of money, and your reviewers say, "That's too much. Give him half as much." This is just a big chunk of money, and you can do whatever you want with it." That's a level of trust that is very useful. I think the year I got it, even back then, it was $575,000, which was huge. No overhead on it, or some tiny amount of overhead on it. That is a big, big award. With that, I actually acquired a second mass spectrometer, expanded my lab, and supported more people. The biggest expense by far is people. In any lab operation, after you've gotten the initial build of the lab taken care of, it's the ongoing supporting of people that costs money. To be able to say, "Yep, I've got money, it's in the bank, come and work with me," that's great. It was really super helpful.

ZIERLER: Do you remember the terms of the award, how much and for how long?

FARLEY: For some reason, I think it was a five-year award, and I think it was 575 [i.e., $575,000].


FARLEY: They're still doing it today. You could look up what they're doing. They have an annual meeting at the Monterey Bay Aquarium, so you meet the other Fellows. I actually met a guy that was part of the class—they called it a class—the year I started, one of the members of that class about six years ago won the Nobel Prize. It's a good collection of people! [laughs]

ZIERLER: You added a second mass spectrometer. Was that so you could do more of the same, or this was for new research?

FARLEY: It was within the same vein of what I was talking about, but it was a more modern—had additional precision, stability, took advantage of new electronics. It wasn't fundamentally new, but I did keep both instruments going, and I actually kept my original instrument until about three years ago. The original instrument that I acquired in 1994, I kept around until about 2017. It was kind of remarkable that it was still working. That's why everybody in the lab needed to know what a resister and a capacitor were, because they had to get in there and fix it!

ZIERLER: You mentioned it was ten years later when you really got involved in JPL. We'll talk about that in subsequent discussions, but I'm just curious, 1997, 1998, we have the proof of concept of a viable rover program on Mars. If you could just search your memory, did that register? Did you think, "Maybe there's something there, maybe there's real science that could be done on Mars"?

FARLEY: Nope. Did not register with me. But what did register was probably four or five years later—we'd have to go back and look exactly when it was—but there was the first talk about sample return. That seemed interesting to me. The things that I am most interested in, for which I have unique expertise, I couldn't imagine that those could be done with a rover. But I could imagine that samples that could be brought back would be very useful. I think most people that do the kind of stuff that I do, broadly defined, would resonate with that statement—that bringing samples back, then we can all play the game. The early rovers, they have some analytical instruments, but they are not of the caliber, they don't have the same capabilities that laboratory instruments do. Many of us would say, "Bring the sample back. Then you're talking." I think in about 2003 was the first serious attempt, that I am aware of anyway, to develop sample return. There were several different ideas about how sample return from Mars might actually be done. In hindsight, it's probably good that those things didn't fly because they were what you might call grab-and-go. They were to just simply pick up a sample and bring it back. Whereas what we are doing now is much more like going into the field and searching for the right rock.

There's kind of an interesting aside—it appears that the Chinese are going to attempt to beat the NASA/ESA collaboration to be the first to return a sample from Mars, but they are going to do it by grab-and-go. If they do it, they are literally just going to land, scoop up some dirt, and fly it back. Anyway, that's what was being talked about around 2003. Even that would be pretty exciting, to actually have something that you knew exactly where it came from. Also probably about that same time was the realization that there are meteorites that originated from Mars in the collection. This is something that Ed Stolper contributed to. I think that was probably discovered sometime in the late 1990s, or at least definitively understood, that there are rocks in the collection that have come to Earth from Mars. If you're going to do grab-and-go, why don't you let nature do grab-and-go? So it's kind of good that that thing never came to fruition. That was the first time I remember thinking about it. Then by the time I became division chair, and we were trying to figure out how to allocate the Moore Foundation money—you remember, Gordon Moore—I can't remember what the number was; it was some extraordinary amount of money that Gordon Moore—

ZIERLER: Six hundred million.

FARLEY: Yeah. Actually in the sub-basement of Arms, we built a facility that has several ion microprobes, which are really high-end instruments for analyzing many different things on very tiny samples. We built that in preparation for sample return. Now, of course sample return did not happen, at that time, but it puts us in a good position for samples that come back hopefully ten years from now.

ZIERLER: You were director of the Tectonic Observatory for a year. I haven't heard of it. What is the Tectonic Observatory, and is that a short-lived directorship for you?

FARLEY: That was interesting. I learned a little bit about the way the world works, with that. That was one of the two things—I think it was only two things—that the GPS Division had supported from the Moore Foundation funds. There was this facility that I just mentioned in the sub-basement of Arms, which I was very intellectually close to, and then there was the Tectonics Observatory. The Tectonics Observatory was an attempt to bring together geophysics and seismology, geology, and especially the kind of geology called tectonics, and geochemistry and geochronology, which is how I came to that. This was a big chunk of money. I don't remember what the budget for the Tectonics Observatory was, but it was a lot, for this group of people, this group of faculty that they identified. Then there was a bit of round-and-round about who should be the director, and what should the director do. Should the director actually direct, meaning, "Okay, I'm making a decision. Here's what we're going to do"? Or, was the director simply going to be the person with the sharp knife that cut up the pie, and "You get your piece, and you get your piece"? It was a very contentious experience, watching this play out, because it was a power struggle. When it came time to decide who was going to be the director, I guess it must have been Ed Stolper went and talked to all of the people that were part of it. And I was everybody's second choice.

ZIERLER: [laughs]

FARLEY: I was nobody's first choice, but I was everybody's second choice.

ZIERLER: Wouldn't it have made more sense for a Seismo Lab person to run it?

FARLEY: It certainly would have made more sense for it to be somebody that was more front and center in that field. I was kind of peripheral to it. This is when I was doing a lot of the work that I was telling you about, looking at the uplift history of mountain ranges, and so I was working with Kerry Sieh, who was part of this, with Brian Wernicke, a whole bunch of people—Jean-Philippe Avouac. I was working with them, and they sort of knew me, and so I got asked to do it mostly just get it going and try to ease the creation. One of the things that I learned—it's really bad when you offer something great, like this giant chunk of money, and it makes people unhappy. That's what this was starting to do. You offer up this thing that should make everybody happy, but they're not happy. I took that to heart. If you're going to offer up resources, then it needs to be in a way that does not create unhappiness. It's not a great thing about human nature, that people feel that way. Anyway, I started in that position. I don't know that I would have succeeded in that position, because I did not have a vision for what it should be. I think that's why I was everybody's second choice. It was like, "Oh, yeah, we'll tell him what the vision should be." I can be reasonably independent, and I can be reasonably penetrating, when people propose what they want to do, even if it's not in my field." This is what I was telling you about, where I feel like I'm technique-oriented, so I actually have the ability to follow along in a lot of different fields. Anyway, I started in that position, that must have been in 2003. But then I got asked to be division chair, and so I stepped back from that.

ZIERLER: For the last part of our talk today, as prelude to when you were named division chair, were you closely paying attention to Ed Stolper's style as division chair? Did you have a sense that you were next in line and you should pay attention to what he was doing?

FARLEY: That became obvious to me probably two years before he finished his ten years, which is at least traditionally the longest time you ever do it for. I was an obvious candidate. It is something that many people cringe when I say it, but it was a challenge that I thought would be interesting. I would not want to say I wanted the job, but I was perfectly happy to take the job when it was offered to me. I say that only because for some reason if you say that you think you could do a good job and you would find it interesting, then people look askance at you, like there's something wrong with you, like maybe you aren't a serious scientist or something like that. In any case, I was paying attention, and I did admire a lot of the way Ed ran the Division. I think he was very good at obtaining resources for the Division, and he was also very good at breaking up some of the really bad behavior of the fiefdom era. I actually watched some of what were very hard conversations with some difficult faculty members, and because of my own experience, I'm like, "Yes! You can't behave that way! You cannot let people behave that way!" He got in there and basically told them they couldn't do it. He told one professor who decided that the "thou shalt not smoke" in—this is sort of amazing—in the even older days you could smoke in these buildings [laughs], but there was a faculty member who thought the no smoking rule did not apply to him. There was a battle, and the chairman won. [laughs] So, yeah, it was good to see his style. I did like his style, and I was learning from him.

ZIERLER: On the concept of fiefdoms, what about the Seismo Lab? That's not a fiefdom as a professor, but institutionally—one of the stories, when it was brought in from the mansion, from the San Rafael Hills, was that it was something of a fiefdom off of campus, and that as an impetus to bring it into the fold of GPS, it really needed to be relocated to South Mudd. Was the Seismo Lab considered a fiefdom in a different way than the professors?

FARLEY: There were definitely people who perceived it that way, because there was an unclear way that you could be made a member of the Seismo Lab. That caused some frustration, for example with Kerry Sieh, who—he's a paleoseismologist; should he be in the Seismo Lab? Should he not be? Should he be given space over there? I personally didn't really see it that way, because it didn't threaten me in any way, didn't threaten my existence in any way. I very much admired some of the things that at that time they were able to do, and I suspect they are still able to do, which is to have a collection of students who move very freely between different faculty members for doing their thesis work. They managed to collectively guide their students, and that's very enriching, if you can do one project with one professor that logically leads up not to another project with the same professor, but to "Oh, this other guy knows how to do this thing that is the answer to the question that I just raised with this first project." They do a really good job at that, and I think it makes the students very broad in what they are doing. If you look at where most of the faculty that we hired, many of them came through as graduate students, so in a sense it is a little bit incestuous, but it is a remarkably successful program.

ZIERLER: When the decision comes, it is as simple as the current division chair names his or her successor, or is there a more formalized nominating process?

FARLEY: The typical way that it works is that about a year before the transition, the acting division chair solicits input of who are the logical candidates. Sometimes there are meetings. For example, there were meetings that I was not invited to because it was clear I was a candidate. The faculty met, and then they provided input to the provost, so maybe the provost actually tasks somebody to report, who are the candidates and what are their strengths. Then I think that individual, whoever is tasked to do it, makes a recommendation, and then it goes through the administrative part of it.

ZIERLER: Last question for today, and we'll build on this in our next talk. In the way that you admired Ed's leadership, what he had done for GPS, when you decided to take this on, what aspects of the division chair for you did you see as caretaking—that GPS was in good shape and it was your responsibility to continue in that trajectory—and where were there obvious areas for improvement that you would be able to take on?

FARLEY: There was definitely an element of, "The Division is in great shape. Don't you dare break it." There was a visiting committee that might have even said something like that, like "The Division is in pretty good shape, and the key goal is not to break it." Just like with the Tectonics Observatory, I did not start with a vision of what we should be, other than we should be the group of people that we are. I wanted to do the job. Like I said, I'm a little reluctant to say that, but I was willing to do the job, because I totally believed in this group of people. I would not say most of them were my friends. They were my colleagues. But I knew that the vast majority of them were really excellent scientists, and I felt like I could do something to facilitate what they wanted to do. Because there was a lot of money coming in from the Moore Foundation, we were in good shape financially, so I did not have to deal with any sort of big problems, other than the inevitable need to keep replacing people. When we in the GPS Division go to hire somebody, it's not like when let's say Engineering wants to hire a mechanical engineer, and they put an ad out and they get 250 candidates, and surely one of them is going to be good enough. It doesn't really work like that. If you put an ad out for a seismologist, in any one year, you might not find anybody you like. So, it's quite an undertaking, and it requires a lot of patience. Sometimes you go years without actually hiring anybody. That was the situation in geochemistry, that when I got hired, they had gone, I don't know, five—they were doing a search for five years before I got hired. So, there is the need to continually rejuvenate the faculty, even though most people in the GPS Division, or at least many of them, spend their entire career, as I expect I will. No reason to go anywhere else. So there's not much turnover, but even the turnover that there is, with people spending 35 years there, you still have to replace people. That was an area that seemed obvious to me that there would need to be attention.

ZIERLER: On that note, we'll pick up in 2004. We'll see what happens next!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, December 23rd, 2022. It is great to be back with Professor Ken Farley. Ken, once again, thank you so much for joining me today.

FARLEY: Thanks.

ZIERLER: Today what I want to do is pick up right when you become division chair. Now, on the personal side, the timing was, as you mentioned last time, you started to get into ultra-marathoning when you became division chair. Was that related? Did you need some kind of an outlet from this new level of responsibility at Caltech?

FARLEY: I'm not sure I started for that reason, but it definitely became a really good way to just clear my head and eliminate any kind of stress that was associated with being in the administration.

ZIERLER: What does it take to become a member of the club? How do you become an ultra-marathoner, either officially or not officially?

FARLEY: The basic entry point is to run more than 26.2 miles. I started with a 50K, pretty quickly went to 50-mile, then went to 100-mile.

ZIERLER: Did you have this natural ability? Were you aware of this and you never put yourself to the test? Or was there a lot of training involved before you got to that point?

FARLEY: Oh, I think anybody can do it. You definitely have to train, for all sorts of things. The one that was most obvious for me is, you have to figure out how to be able to eat, while you're running. It's a peculiar thing to pick up a sandwich and start running with it [laughs] and eat it at the same time.

ZIERLER: How does it work in terms of strength conditioning versus aging? Are you able to keep up your performance? Does it go down? Do you actually get better the more that you do it? How do those things work?

FARLEY: For me, the experience was, you get better for a while, and then usually what happens is you get more ambitious. And unlike most road marathons which they differ from each other subtly, ultramarathons, because they mostly occur on trails, can range from flat and smooth and simple to extremely mountainous. I pretty quickly gravitated to the extremely mountainous ones. The big challenge there was just to keep going. It's kind of hard on the body, though, to keep doing that, year in and year out.

ZIERLER: What does that look like on your knees after all of these years?

FARLEY: I'm not sure there's any implication on my knees. This is something people often ask, and I'm not sure that that's true. A lot of people say that, and I don't know any ultra-marathoners who have, for example, had to have knee replacements. That doesn't mean anything; it's just anecdotal. I will say, however, I did wind up in the hospital with kidney failure [laughs] after one race, and spent four days recovering from kidney failure. So, that's more of a direct risk.

ZIERLER: Is that dehydration?

FARLEY: Yes, it's dehydration, and then also the release of a lot of muscle tissue breakdown that clogs up the kidneys.

ZIERLER: Are there running shoes, running sneakers, that are ultramarathon-grade, that are different from shorter races?

FARLEY: Yes, for sure. You definitely want to have heavier-weight shoes that give you a little bit more support and cushioning for beating yourself up on trails for hours and hours and hours.

ZIERLER: What does the training look like? Is it solo? Do you have like a Sunday morning group? What does that look like?

FARLEY: Everybody is different, but my approach was to run by myself. I actually really enjoyed that, and I learned all the trails in the San Gabriels. We had this big fire in 2009, the Station Fire, and it burned a lot of the San Gabriels. Then the Bobcat Fire a couple of years ago. I think there are a handful of people in Los Angeles that actually know the areas that have burned, because the trails go way back in there, and a typical San Gabriel trail is three miles of very, very steep ascent. You've got to climb three or four thousand feet, and then you get over the crest, and you get down into the canyons, over the top. It was heartbreaking when that burned, because those were my favorite places to be. I'd get out there and just get into the Zen of the thing.

ZIERLER: What does the recovery look like? Have you visited those trails recently?

FARLEY: After the 2009 fire, the recovery has actually been pretty good. It was really interesting to see what kinds of trees burned and didn't come back, and what kinds of trees seemed to burn and then came back over the course of a few years. Not too surprisingly, all these enormous oak trees that I thought were dead were just singed, and it took them a couple of years later to really leaf out and come back. A lot of the imported pines, they burned and they didn't come back. So, it's a change.

ZIERLER: What do competitions look like? Do you participate competitively?

FARLEY: I haven't for the last few years, because unlike the division chair job, with the project scientist job, it is very hard to find the time to get out and do the training. For a 100-mile race, a typical training is to run at least a few weeks at 100 miles a week. On trails, it's really tough to go more than three miles an hour. That doesn't sound like very much, but when you're climbing or descending on rocky trail, that's a pretty good pace. So to train 100 miles a week, you're committing 30 hours a week to do that. That's a lot. Then, the typical kind of race that I liked would be in the mountains somewhere. My best time at 100 miles was slightly over 24 hours, and my longest time was 43.

ZIERLER: Because the project scientist position is open-ended, do you envision at some point getting back into competition?

FARLEY: I'd like to. It will be interesting to see whether now that I'm almost 60, whether I have the same ability to do it, and the same drive to do it. I'll tell you, though, I often related the Mars 2020 job to an ultramarathon. I even brought that up once at a big review that we were having at NASA headquarters. Because it's very similar, in the sense that if you are running a 100-mile race, you have to not think about how far 100 miles is, or you will never finish. It is always, "I just have to make it to the next aid station," which is typically no more than four or five miles away. "I only have to make it the next four or five miles." Then you get to that point, and you say, "I only have to go another four or five miles." When you start with a handful of people on something that you know will take a decade just to get to the launchpad, and then another decade to execute, if you are impatient, if you are thinking about getting to the finish line, you'll never make it. So, it was very useful for me to have that perspective. Also, there were many times along the way when we ran into technical problems, where we ran out of money. I said directly to the folks at NASA headquarters who were reviewing our progress and worrying about our budget that one of the things about an ultramarathon is—or even a regular marathon, I suppose—you put together a great race for the first, say, 90 miles, and by god, you don't want to fail in the last ten miles. If you put all of that effort to get in 90 miles, then you have to keep going, no matter how bad you feel, or how little money you have to finish the job. You have put in so much already; don't screw it up.

ZIERLER: Wow, that's a great metaphor. I love that. What you said about time management, that actually gets me to what I wanted to return to when you became division chair, and that is, how you carve out the time to maintain an active research agenda when you do become division chair. What was your approach to that? Was it like Fridays? Was it two hours a day? How did you do that?

FARLEY: This was a big deal for me when I was thinking about taking the division chair job, because the thing I enjoyed most about being a scientist was working in the lab, actually getting in there, putting my hands on hardware, putting my hands on samples, and having the joy of wondering, "Hey, I wonder what's in this sample. I wonder what it's going to tell me." And then doing the work, and then watching the data come out of the computer at the end of the experiment, and thinking about it. That's why I became a scientist. It's why I enjoyed being a scientist. Giving that up to take an administrative position was hard. There are things that, just as a practical matter, have to happen. I had to have somebody that could actually keep the lab running in my absence, because a lot of what I did in the lab was to simply keep it running. I was the one that knew all of the details of how the instruments work, and a lot of the code. As I mentioned earlier, it was the code that I had written, or my group had written over the years, but I had always paid close attention to it. So, the first was just a practical matter of finding somebody to keep the lab going, and I was fortunate to be able to do that. It is a benefit of the division chair to be able to get some support to allow the research career to continue. Frankly, if I didn't have that, I would not have taken the job. Especially when you're not sure if you're going to enjoy the job, unless you're close to retirement, you don't want to shut down your research operation. Caltech makes it possible to be able to keep the lab going, financially, at least at a reasonable level.

ZIERLER: That means what? Hiring a research scientist?

FARLEY: For me, it was hiring a lab manager. I did have to transfer a lot of those kind of responsibilities to a lab manager. I also then had to work more with students and postdocs to let them do the practical part of the work. Before that, I had had relatively few students and postdocs because I did enjoy doing a lot of it myself. Then spending about 50% of my time being division chair, I just had to let that part of it go, and let the students do it. That's a whole different sort of experience, and it worked out well.

ZIERLER: I wonder if ironically that's better for the students, when, whether you like it or not, you have to pull back.

FARLEY: Yes. I did often tell the students before that job that there are a lot of different ways you can interact with an advisor, and you should think carefully before you choose an advisor. I'm the kind of advisor who is going to be looking over your shoulder every day, not because I don't trust you, but just because I want to share in the excitement of whatever you are discovering. There are other advisors who will say, "Well, here's a topic. What do you think?" and talk about it for a couple of weeks, and then say, "Come back in a year, and tell me what you've got!" [laughs] That's definitely not my approach.

ZIERLER: When you became division chair, did your research group shrink? Did it have to?

FARLEY: I don't think it changed very much. Typically I would have a group of three or four people. It was always a small group. It stayed about that size through that time period.

ZIERLER: Something interesting you said in a previous conversation—your recognition of how cohesive GPS was. To the extent that you can compare it with other divisions on campus, what's the root of that? Is it because the disciplines just fit well together in a way that maybe EAS doesn't? They just have a far broader, more diverse set of disciplines? Is it the history? Is it the division chairs that came before you? All of the above? What makes it so cohesive in your perspective?

FARLEY: That's a really good question, and something I think I definitely thought about, and had long conversations with the previous division chair, Ed Stolper—"What is it that makes this work?" I think it's a little bit of everything that you just said, but there are some things that are directly important. At least among the divisions at Caltech, the GPS Division is unusual in that it is all clustered very tightly together physically on the campus. We have a collection of buildings that are all right next to each other, and interconnected by doors that make it easy to not have to go outside, to go and see your colleagues. So, I think physical colocation is important. Now that we are hopefully nearing the end of the pandemic, I think we've seen what kind of damage not being physically present has had. It has been hard on the cohesiveness of the group. That's the first thing, that we are collocated. The other thing, which I didn't really understand until I was division chair, is that to be a Division of Geological and Planetary Sciences, within our field, broadly defined—geological and planetary sciences—this is a diverse collection of people that in many other universities might well be dispersed among different departments.

There might be a geology department and, say, a planetary science department, even an astronomy department. Some of the people that we have in GPS would be astronomy. So, it's a lumper rather than splitter model for divisions at Caltech. But just from a practical point of view, to have a Division of Geological and Planetary Sciences equal to, in terms of the interaction with the administration, to be treated as an equal with Engineering and Applied Science, or Biology, or Chemistry, that is really unusual. The Division is large, compared to the competition, and I think that is partly one of its reasons for success. When you have a group of people that are feeling successful—being a top-rated program in, say, for graduate school, or even broken down at a research level and say geophysics or geochemistry, we have been top rated for a long time—that is partly because we are treated as equals with whole other major research disciplines. It's easy to be enthusiastic and positive when you feel like you are succeeding, as opposed to when you are struggling. I think that's one element of it.

The other is sheer force of will of previous division chairs to prevent fragmentation and to prevent tribalism. Tribalism is, I think, a serious impediment to—here what I mean is that if you identify primarily as a geophysicist and not as a member of the Division of Geological and Planetary Sciences, it makes it harder to actually watch out, as a whole, to what we are doing. If you take the tribal approach you may be far more concerned with, "Hey, are we going to get the next hire?" or "Are we going to get the next faculty position, or is it going to go to geobiology?" That is a very unhealthy way to do it, from the sort of federation point of view, the division point of view. So, there's a big effort to stay focused at that level, at the higher level of the health of the division, and not myopically just looking at the sub-discipline.

ZIERLER: Being treated equally, what are the metrics? How do you know that? Is it an interpersonal thing? Is it dollars and cents? How do you know you're on the right track in terms of feeling like you're being treated equally, at the Institute level?

FARLEY: The most visceral one for me is, my first day on the job and I go to a meeting of the IACC, which is the collection of division chairs, the president, and the provost, to make decisions about what the Institute is going to do, for example, to vote on a new faculty appointment in physics. The chair of the Division of Geological and Planetary Sciences has the same vote as every other division chair. That may not sound like very much, but that's a pretty powerful position, and it also works at the same level of watching out for the health at the Institute level. We're a tribe in the Division of Geological and Planetary Sciences, too, that's different than, say, the Chemistry tribe, but that's the place where you come together as a group and try to look at the health of the Institute. I think the experience that I had is, being treated as an equal makes you far more willing [laughs] to take on that kind of conversation, as opposed to saying, "I need to get mine." That part of it is really important.

ZIERLER: Both personally and at the Institute level, what are some of the challenges and pleasures of weighing in on hiring decisions when you're looking at a candidate in a field that you have no idea what they do, really?

FARLEY: You just hit the nail on the head, that some of the appointments, you could kind of understand them. I could kind of understand them. Like, "Okay, I get a sense of what this person is doing." Then there were others that we would just laugh at, as we were evaluating, in string theory or in some exotic mathematics or something. We had no idea. [laughs] Often times even the division chair who was presenting the case to hire somebody in their division didn't really know what this was all about but everybody said it was good. But we all tried. If you don't know the field, then you have to read the letters carefully. That was definitely a challenge. The other part of the challenge is to try to distinguish somebody who has the potential to do something extraordinary versus somebody who is doing well but who may not break out into new areas. That is what I found most interesting, is listening to my fellow division chairs try to navigate that question. Even if you don't know the details of the field, trying to figure out, "Okay, what is this field? Is this field likely to have a breakthrough?"—that's really interesting, too, and gratifying, to be part of that. Otherwise I would have no idea what interesting new things were coming along in different disciplines than my own.

ZIERLER: On the question of hiring, thinking back on your own experiences when you were the only assistant-line professor when you were hired, what were the demographics of GPS at that point? What opportunities did you have to make new hires and to help some of the older generation retire?

FARLEY: We were actually in pretty good shape, in the sense that there were people that were retiring at 70. There was and I think largely remains a commitment to retire by age 70. That is obviously not required by anybody. You're not even allowed to really talk about it. But the tradition, which I think is part of this recognizing that the health of the whole is important, when you reach age 70, you should retire. And people were retiring, so I did not feel like we needed to push people out to make more appointments. We did need to think about what areas we wanted to go into, and how we were going to find space for people, but from that point of view, it was clear that over the course of a few years, we could make multiple hires. That's about as fast as the GPS Division can make a hire. I mentioned the last time that we can't just put an ad out and get 250 candidates, of which you can be sure that half a dozen are going to be hirable. It's just not the way it works. The fields are small and specialized, so it takes years to go from starting a search to actually having a hire.

ZIERLER: If the actual hiring decision takes place at the Institute level, is it the division chair's job to bring those candidates to the IACC for consideration? You're going out, you're assessing who is available, who to bring forward for consideration?

FARLEY: The way it works in GPS, and I think this is true probably across the Institute, is you need to get permission to establish a search, or that there is a position available. You have to establish that by interaction with the central administration. Then you task a committee, often dominated by people in the general discipline that you're hiring in—if it's say in geology and you want to hire a geologist, you task the geologists and a few other folks to add some diversity into that group. They come back with a recommendation. That then goes through an entire process involving all of the GPS faculty, and then the division chair takes it to the IACC. What I learned from that, and this was true for many different things that we had to do—hiring, tenure, awards, all of these kind of things—the division chair is responsible for holding forth to the rest of the group, who are of course very smart people, they're all faculty members, but they're not in your field, and one of the big challenges, and the thing that I actually feel like I got pretty good at, is how to take some piece of science that somebody was doing, either somebody you wanted to hire, or somebody that you wanted to give tenure to, how to take what they have done and explain why it is important, for very smart people who are not in their field. I learned how to be a generalist, I think, and this has helped me a lot in working on the Perseverance job, too. I have a very similar sort of task, talking to a lot of stakeholders, a lot of very smart engineers, who have no idea why you would do the different things that we are doing. If you try to explain it as you would to your colleague down the hall who is an expert in the field, these people that are a little farther away from it, their eyes will glaze over. I became very good at that part of it.

ZIERLER: GPS's relative smallness, both within Caltech and among Caltech's peer institutions, how does that cut both ways, in terms of recruiting? In other words, for much bigger departments that might have, for the next rising star postdoc, that person may or may not be attracted to working with people who are very similarly expert in their field of research, how does that work for GPS? Are there enough people in GPS where you can look at anybody and say, "There are people here that you can work closely with?" Or is it more like, "You're going to come to Caltech, and you're going to figure out what areas you're going to do on your own, and you're going to branch out into new disciplines, because that's just how we do it here." I wonder if you can explain broadly how that works from a recruitment perspective.

FARLEY: I'm not sure I got the first part of that question, but the one comment that I would make is that unlike at least most of the other divisions at Caltech, the GPS division is not small compared to its competitors. This is why it is a great place to be. Because as I was indicating, we are equals with Engineering and Applied Science, and while we are smaller by probably a factor of two, I think in a lot of universities, the Geological and Planetary Sciences would be smaller by a factor of ten. In absolute terms, also, it is a big group of people. To have between 30 and 40 faculty members in this area, that's big. A fraction of them are joint appointments with other divisions, so we have strength coming from chemistry, coming from engineering, that contribute to an overall strength. This is a thing that Caltech is capable of doing because it is small. It's not hard to establish joint appointments across divisions, to share students. It's a relatively frictionless system, and at least when speaking to my colleagues at other institutions, that is not the case. So recruitment, say, for a new professor, that issue that it's small is a big plus, for a lot of reasons that are less to do with what is your diversity of academic fields. Because as I said, we are large from that point of view. As an example, I would say Berkeley is a competitor in many areas. If you want to drive to work at Berkeley, you park your car, and it's a 20-minute walk to get to your office. No matter where you park around Caltech, [laughs] it's not a 20-minute walk to your office. These are just subtle things that make it special.

ZIERLER: I'm not sure if Jeroen Tromp ever shared this with you, but he relayed this amazing story about his determination to come here, which resonates quite strongly with what you said, and about how Caltech supports its junior faculty. He said he had this vision to create the next generation of high-powered computing for geophysics, and he wanted to do this at Harvard, and they just were not interested. He came and shared this vision at Caltech, and the provost said, "Yeah, that sounds great, let's do it," and it was as simple as that. As division chair, from your own experience, from hearing about Caltech's culture, how could you contribute to perpetuating this amazing support that young faculty members can get?

FARLEY: That support of course has several different flavors. The first is just financial resources and space, which at some level are strongly correlated. If you need to, you renovate old space and turn it into new space. I remember very well when I became division chair that Jeroen and Ed had made a plan for the new computer, but we had an empty room in the basement of South Mudd that we needed to fill, so we needed to acquire money to do that, and we needed to get the space all fixed up to do that. Those are the usual challenges of the division chair. One thing that was really interesting for me was shortly after becoming division chair, the approach to fundraising changed from a kind of centralized model, as I understand it, where there was a relatively small number of very large dollar-figure donors, like Gordon Moore. Especially when Jean-Lou Chameau came along as president, there was a big effort to try to broaden the base and distribute the activities of fundraising. So, one of the things that I needed to do very quickly is figure out how to be a fundraiser, which did not come naturally to me. As I was just saying, I feel like I could communicate with people about why something is exciting, but I had a very hard time making the ask. Once you get to the point where you've got somebody excited about something, you say, "By the way, could you give us a couple million dollars?"—that part was hard.

As part of this effort to acquire financial resources for the Division, one of the things that the divisions created at that time, under the direction of President Chameau, was what were called chairs councils. These are collections of donors that were identified by and then brought along by the division chair. To seed this effort, we were assigned trustees to help us with this task. The trustee that was assigned to me and to the GPS Division was Ted Jenkins, who had no background in geological and planetary sciences. He had taken a class or he had gone on field trips with a legendary Caltech geologist, Bob Sharp, and he remembered them fondly. He and I had lots of conversations about how to create a group that raises money, and when I basically confessed to him that I found this difficult, he explained to me that I had it all wrong, that from a donor's point of view, you are doing them a service. You think you're asking them for something but in fact you are giving them an opportunity. That really made a difference to me, to realize, yes, many of these people have enough money; they are looking for something good to do with it, and you are helping them. That made it a lot easier, once I got to that point. So, acquiring financial resources that you can provide, in many cases it is to the junior faculty, who have expensive visions for things they want to do—sometimes it's more senior faculty—that is a big part of letting people dream their dream. Since I knew we were going to talk about my time as division chair, I was thinking about, what would I say about it? Did I have a vision for what I wanted to do? I didn't really have a vision for what I wanted to do, but I had definitely by that time already seen that there were a lot of really good ideas among the faculty, and my goal then really became to sift through those and try to support the ones that I was convinced would lead to something big and unusual, and then to try to acquire funds to do that.

ZIERLER: On the question of working with benefactors, I'm fascinated—the Seismo Lab's long and unfulfilled quest to secure an endowment, if you took a stab at that, if you have any insight into why, after all these years, in light of its phenomenal success, its world-leading research, why is the Seismo Lab still not endowed?

FARLEY: I don't know. Maybe people don't want to have their name associated with disasters?

ZIERLER: That's interesting.

FARLEY: At the end of the day, that's really the bottom line, I think. I don't really know. But I think being honest, the way big-ticket fundraising works at a place like Caltech, for something that is not immediately sellable, like "We want to build a building in which the cure to cancer is going to originate"—many of the things that we do in GPS are not like that. And not many of our alumni have an enormous amount of money. We didn't invent semiconductor lithography. We don't have people that have gone and made billions of dollars. But there are people that are interested in what we do, and the way fundraising really works for large-ticket items is the central administration just needs to say, "Hey, we need you to do this. This is important at an institutional level." That's what is great about having a committed set of trustees and donors, is they can be steered to things that aren't necessarily the thing that they are personally most excited about. But when the president says, "The most important thing you can do for us is this," I think that matters a lot. We have had experiences like that, where money has arrived. The big example that happened early on in my time as division chair was a generation of funds from Ron Linde to renovate the Robinson building, which had been an astrophysics building. It's right there in the cluster around the GPS buildings, so it was a very logical building for the GPS Division to acquire and then put its environmental science program in. I don't know the details of how that ask was made, but I think there was a fair bit of, "Hey, we really need this building. This is our highest priority." It happened, and we centralized environmental science in a single place, and then actually grew it, made the program bigger.

ZIERLER: In terms of conveying that environmental science is a central priority, was that part of the overall push at Caltech toward sustainability research?

FARLEY: Yes, but it predates that name. Getting this group centralized and stronger predated my time as division chair. It was pretty obvious by when I started in 2004 that this was an important area to be in, to understand. This is also an area where a fair bit of thought needed to go into what Caltech could do that was unique and special. Because as we talked about in our earlier conversation, it is very hard to compete with, say, the National Center for Atmospheric Research, or an oceanographic institution that has 150 people working on this problem, so we had to pick and choose and figure out what we could do that was special. We were obviously not going to try to compete at that level. That was a challenge, there. Then the whole sustainability thing, which then branched out from understanding the way the Earth works to figuring out how you go lightly on the land, that is a growth that came later.

ZIERLER: In 2006, with the transition from David Baltimore to Jean-Lou Chameau, as division chair, are you more involved or aware of those processes than regular faculty members would be?

FARLEY: I was certainly aware, more, that the process was happening, and I think unlike many faculty members, I was unsurprised when we were told we were able to hear who the new president was, but I was not involved at any level in the selection process.

ZIERLER: In 2008 when the financial crisis hit, how did that affect GPS? What were some of the most important things for you, just to keep the science going?

FARLEY: That was a real learning experience in a lot of ways. Research grants were not that negatively impacted, and pretty quickly there was stimulus money coming in. I forget the name of the act, but there was some bill that actually shoved more money into, say, NSF, which is the largest funder for the GPS Division. That wasn't a huge hit there, but there were lots of challenges of money coming from the central administration. It's important to understand the distinction between money that supports research—so a research grant that I get supports my students or my postdocs, maybe my lab manager, but it doesn't do anything to cover the Institute's costs other than some overhead. It doesn't cover a large fraction of a faculty member's salary. It doesn't cover all of the administrative support that we get, the administrative staff, all that sort of stuff. The Institute was definitely scrambling for money, then, and in my opinion made a bunch of stupid decisions about transferring costs from the central administrations to the divisions. But the divisions have no way to raise money, so it was quite a painful and challenging thing. That's fine; it's good to do these things every now and then and try to understand where you are spending money on things that you didn't know. As an example of something that the central administration did, they used to actually deliver the mail directly into our mailboxes, but as part of this downturn, they decided they would simply drop it in one place, and the division could hire somebody to put it in the mailbox. Well, that doesn't change the cost of doing anything; it just transfers it from one place to another. That was a frustrating thing.

But the thing that was more interesting to me was trying to do the thing you hear about, which is "Don't let any crisis go to waste" or something like that. We had built up, under the control of the Division—the division administrator and the division chair—administrative staff whose skill set no longer aligned with the way faculty members went about their work. We had administrative staff who were hired partly, years ago, because they could type quickly. Well, that's really not a skill that's that important anymore. Almost nobody, when I was division chair, was writing by hand on a sheet of paper and handing it to their administrative assistant to type. We had people that could do things like go to a travel agent and get you a ticket for something, but nobody does that anymore. So, we had collected a bunch of people whose skill set was wrong for the modern world, and we had more of them than I personally thought we needed. Because if you can do that all yourself, and you can do it efficiently—and doing travel, you're far more efficient if you can just click, click, click, click, and be done. By 2008, that was already clear that we could be doing that. But it was very difficult to make any changes in that area. There's just an enormous reluctance to—there's no way to sugarcoat it—to lay people off, to just say, "You don't have the right skill set anymore."

We did that. We did manage to slim the division some. But there were people who were extremely negative about that. That that is not the purpose of the institution. Even in a time of crisis, you protect everybody that works for you. I understand that mentality. I also felt like in the long run, you've got to do the right thing for the division and for the institution, and that may be not doing the right thing for some particular individuals. But this is something I have definitely seen, even going forward into the Perseverance job, that there's two different ways to look at an organization. One is, you need it to be as efficient and as effective as possible, and the other is, it's a family, and we're all doing our thing together, and you don't throw a brother or a sister out on the street just because times got difficult. I found that to be both challenging and disheartening, to feel like I was doing the right thing, and then to get negativity for it.

ZIERLER: On the flip side of laying people off, of course, is hiring. Jean-Lou Chameau really tried to—as you said, there's opportunity in crisis—to make hires, particularly when competing institutions might not have been. Was GPS able to make some recruitments during the financial crisis as a result of this Institute mentality?

FARLEY: I don't actually remember the timing, but GPS did not have trouble recruiting, except for in some specialized areas. Hiring a seismologist, we are the center of the universe of seismology. If you want to be a seismologist, you want to be in the Seismo Lab. If you're an isotope geochemist, you want to be at Caltech. So, we have it a lot easier than a lot of the other divisions. The area where that is not true is in environmental science, for reasons that I just talked about. It's not a huge institution, doesn't have a giant reputation, so that has been a struggle. I don't recall any interactions that happened specifically over this particular period, where we became a better, more attractive group because we were not retrenched. Whatever retrenchment we had, it was short-lived.

ZIERLER: Besides the director of the Seismo Lab, are there any other similar positions in GPS that have that director title within the Division?

FARLEY: Not with that level of visibility. There are directors of centers. There is a director of the Linde Center, for example. That's environmental science. Those, you hit on an interesting topic, which is, what are those positions? What are they for? What do they do? The only one that had a budget where the division chair would simply hand over money to another person to distribute was the Seismo Lab, and that was historical, and honestly it was a little bit awkward, because the director of the Seismo Lab then had authority over allocation of resources to a group of faculty that made it different than, say, if you were a geologist or a geochemist. Like, "Why are they being treated differently?" It's something that you have to pay attention to. I mentioned this earlier—you don't want discretionary money to make people unhappy. It has a real potential to do that if people don't see why decisions get made. You've got to be transparent about it, and you've got to treat everybody fairly.

ZIERLER: I asked about bandwidth during your time as division chair, both for students and staying in the lab. What about just in terms of generating new research ideas, new things to work on? You're just relying on the areas that you already know, and there's time to do more work on them, or are you actually able to come up with new ideas, as division chair?

FARLEY: During that time period, I think I just fortuitously had several really spectacular students and postdocs who really were able to put things together. But in terms of generating new ideas on my own, this was definitely a lull. If I go back and I look at what I was working on through that time period, I could see a lot of it was continuing on in areas which we had momentum already, and not bringing in a lot of new stuff. To be honest, this was always in the back of my mind, probably because of other division chairs, as I watched them cycle off and back into their faculty positions, some of them retired, and some of them were faced with, "Wow, I have to spin up my research group again." It's a pretty daunting thought if you, for example, have let your research grants be reduced. I always kept my research grants going, but not at the level that I had been. It's very daunting. I had been watching that, and wondering, "What is it going to be like when I go back?" But it was clear that by 2014, I would be done, because it's a no more than ten-year job, and I decided that I would stay for the full ten years. In the later part of my time as division chair, I had gotten involved in the Curiosity mission, and then as I mentioned earlier, I wound up getting the project scientist job in 2013. So I had already seen, "Oh, that's my future. That's where I'm going to go. I will simply trade off the administrative time that I was doing as division chair, for the time working with the JPL engineers building up Perseverance."

ZIERLER: These spectacular postdocs and graduate students that you were fortunate to work with, what stands out in your memory? What were some of the projects that they were working on that were really so good?

FARLEY: The most important thing, which ironically literally just the last few days I am revisiting and trying to take the ball a little bit further along—we had been working on this idea of thermo-chronometry for years, and there had always been a few things that didn't quite fit. The combination of a postdoc and a student, not working together but working separately, had both been approaching this problem from different directions, and suddenly it became clear, "Wow, they are seeing two sides of the same coin." It was just fabulous, to see it come together. The basic idea that we had been missing was, we had done all of these experiments to understand the temperature at which helium comes out of apatite. That's the basis of thermo-chronometry. What the three of us—the student, the postdoc, and I—all realized together was that when uranium decay happens, the crystal gets modified by radiation damage. We figured out not only that this phenomenon exists, but we figured out how to quantify how it affects Helium diffusion and model it and package it up in a tool that the community could use, and has used. This little burst of activity in about a two-year period led to a couple of papers which are now amongst my most heavily cited papers, because they not only explain a phenomenon, but they explain how you use it and provided a tool that the community uses. That was pretty gratifying.

ZIERLER: At the five-year point, is that when you make the determination whether to re-up for another five years as division chair?

FARLEY: Well you have to say whether you're willing to be considered. I will say this is an awkward dance. What you don't want to do—and I definitely heard Ed Stolper's opinion on this, and I shared it—you don't want to be in the position of saying, "Yes, I'm willing to be considered" and then get turned down. That's just kind of a slap in the face. You would be better to simply step back. So, when the time came, I sort of asked around, like, "What do you think? Do people want me to stick around?" There was general interest in having me continue, and so I put my name out there, and there were meetings which again I was not invited to, where the decision got made to offer me another term.

ZIERLER: Did you think about not doing it yourself, that there were other things to work on? Obviously there was enough there that you enjoyed it, that you wanted to continue?

FARLEY: By that time, I had found the parts of the job that I felt I was good at, the parts of the job I enjoyed. I don't know that I said this directly, but the thing that I look back on as the thing that was rewarding, and it's rewarding even still today, is I had enough resources to allocate to projects to get people started on doing things. Some of those things are fabulous. Some of them have gone a long way, and it's a way that as an individual in a small research group, I never got to see. I got to participate in helping science happen at a much bigger level than you could ever do as an individual professor unless you're heading up some gigantic research group. I enjoyed doing that, and I wanted to continue to do that. There is an element of, "I know this job, and I don't know that anybody else right now is the right person to take that over." By the time I was at ten years, I was over that part of it, and ready to move on. [laughs]

ZIERLER: I'm curious your perspective on your administrative relationship with Ed Stolper. It's this unique situation where you succeed him as division chair and he becomes provost. I can see it might cut both ways. It might be very close, because of the fields and the things that you've done. Or, you both might have felt like there was some space that was needed there, so that you could be your own division chair. I wonder if you could reflect on that.

FARLEY: That's a really good point. It was made even more complicated by the fact that Ed is a friend, and he was largely responsible for my getting hired, so there's a little bit of personal relationship there that makes it hard. I think he and I both worked to have an administrative relationship that didn't look different from the way he interacted with the other division chairs. I never really got into a situation where I felt like he and I diverged in what we thought was the right thing for the Division, and I would say that is at least in part because I'm quite aligned with his thinking about what the Division should be, coincidentally. So it was not a major source of friction, I don't think, at least not for me.

ZIERLER: An overall question about the research that happens in GPS, specifically when you are division chair. What is the rough breakdown of terrestrial-based research versus non-terrestrial based research? And just in terms of trendlines, have we seen an interdisciplinarity, where people are getting more involved going both ways?

FARLEY: In my time as chair and continuing forward, one of the important things, one of the things that became very obvious was going to be important, was extrasolar planets. In many institutions, extrasolar planets are part of astronomy. That's true partly at Caltech. There are astronomers who are interested in extrasolar planets. But there were also people within the GPS Division who were interested in this topic. We worked very hard with PMA to build strength in this area. I think when you look at our planetary science group, it includes people that are involved in what you might consider to be very classical planetary science, actually looking at planets in our solar system in great detail with space missions, and there are others who are looking more broadly at extrasolar planets. That was an area that grew over this time period. A related area is the growth of satellite geodesy. That is an Earth-centric science that is facilitated by space missions. That area grew with people like Mark Simons getting deeply involved in that.

ZIERLER: I'm curious what your perspective was on Mike Brown and the killing of Pluto, when you were division chair, what that meant for GPS, and specifically all the public interest, all the media attention on this issue.

FARLEY: That was very fun to watch, and to listen to him. He and I are almost exactly the same career stage, got hired at roughly the same time. It was fun for me to watch him have his—well, multiple moments of discovering things. The Pluto thing, as he will tell you himself, scientifically, it really doesn't matter. What you call things, it doesn't really matter. What I found more interesting and continue to find interesting is he and Konstantin think that there's another planet out there that could be quite large. I just find that amazing, that there are these subtle clues out there that are totally different than the way other planets were discovered where you just look in the telescope and you're like, "Oh yeah, there it is." To actually see all these subtle clues and be acquiring more clues and looking for it, I find that very fun to be able to watch from nearby.

ZIERLER: I thought to ask because Mike considers himself, of course, an astronomer, and yet he's in GPS. As division chair, because there is such a strong inclination towards astronomy, does that forge relationships with PMA in ways that might not be there otherwise?

FARLEY: For sure. There's a lot of interaction there, over hiring of people who—I think where there's a lot of potential is hiring people who, in astronomy—before I say that, let me—the individual that you might hire in astronomy to study extrasolar planets is different than the individual that you might hire in GPS, to study extrasolar planets. As an example, many of the astronomers that have been hired over the last few years, and even starting when I was chair, who are looking at extrasolar planets, they are telescope gurus. They know how to make a detector that is super sensitive, or has whatever characteristics there are. They are technically superb with instruments. We wouldn't necessarily want such a person in the GPS Division, because that's not our thing. Our thing is not building telescope instruments. It is actually interpreting data. For example, we have Heather Knutson, who is really interested in the atmospheres of extrasolar planets and what they can tell you about the characteristics of the planet. She uses the kinds of techniques that those astronomers are developing. This is a place where making that link is really important. The technical people can go and discover the planets and tell you something about what they have seen, but then it takes people that actually understand planets themselves to take it the next step. This is a fruitful thing, that Caltech has put together. Partly because it has quite a few people in both of these areas, with an incredible strength in Earth-based telescopes, of course, and with strength in planetary science, it was natural to move in that direction.

ZIERLER: In your second term as division chair, you were at Caltech for long enough, it's amazing that it's only at this stage in your career that you start to get pulled into JPL. What is the origin story there? How did that happen?

FARLEY: I'm trying to think of how this happened. There was a group that was developing new kinds of mass spectrometers. Those instruments appeared to be capable of making measurements better than the kinds of instruments that were sitting on the floor in my lab. JPL's primary interest is making flight instruments. I looked at it and thought, "Wow, you could probably compete with a laboratory instrument here." I got engaged in that, and we jointly developed some and explored some capabilities of them. That's what got me in the door, and actually to see how the place works. That logically led to the thing that I mentioned before, where it must have been sometimes around 2010, maybe, where JPL was very interested in trying to understand where the next generation of flight instruments, what they might be, and also to be looking for flight instrument PIs. One of the challenges of JPL is if they wish to lead an instrument development that goes on a mission or a mission itself, they need leadership. They need people who can lead the science. The chief scientist at the time was organizing meetings that ultimately got supported by the Keck Institute for Space Studies, which was a fundraising thing that appeared at about that time to support these activities, to provide money on the boundary mostly between the scientists on campus and the engineers on the lab, to develop new instruments. In thinking about how to do this, we actually pursued some new kinds of capabilities for dating rocks beyond the Earth, and as I mentioned before, that's how I got sucked onto the Curiosity mission, and then just went from there.

ZIERLER: What were some of these advances in mass spectrometry? What was going on at this point?

FARLEY: The JPL group was working with an instrument called an ion trap. The huge benefit of an ion trap as a flight instrument is the instrument itself is about the size of your thumb. The electronics, you can put in a shoe box, and they use less energy than a small lightbulb. If you compare that to what sits on the floor in my lab—as I mentioned once before, it's like half a ton, and it uses a huge amount of energy. There's no way it could be flown. And it's super delicate. They were exploring the capabilities of measuring noble gases with this very tiny instrument. What the JPL group had been able to do was to take the theory—the theory of these instruments has been known for some time—but to actually implement the physical construction of the thing, first of all in a way that was precise enough that you could realize the big benefit. And the big benefit that I was looking for was the ability to measure helium-3. Helium-3 is very hard to measure because you need the ability to separate it from other species of the same mass. Unfortunately, the hydrogen-deuterium molecule, HD, is everywhere, where you're making a measurement, and it is very close in mass to helium-3. They were designing an instrument where they thought they could make this separation, and then do all of these things where you could make it really, really tiny. Ultimately, that instrument, I was a PI on a proposal to fly that instrument on the Europa Clipper mission. It was not selected, and in hindsight I'm very glad it didn't get selected [laughs] because being project scientist for Mars 2020 and a PI on an instrument on Europa Clipper would have killed me! [laughs] But that's where that actually led to. Getting to see how JPL operates and having JPL learn about me is I think why I wound up being offered the project scientist job and why I took it.

ZIERLER: The Mars rover program, in sequence, going from essentially proof of concept with Sojourner, do you feel like the timing was such that the science objectives of Curiosity were well enough developed that it was that and not Spirit and Opportunity for you to get involved? In other words, was there not enough science going on with MER for you to have gotten pulled in? Is that part of the story as well?

FARLEY: I don't know if I would say not enough science, but not enough science of the type that I could contribute to. As I think I said in the very first conversation we had, I call myself an isotope geochemist. Spirit and Opportunity had no capability for measuring isotopes. They could measure elements, but not isotopes. The important new addition to Curiosity was a mass spectrometer with the capability to measure isotopes, the SAM instrument. When I looked at that, I thought, "Yeah, that's a game I can play. I understand how to do that, and I can do something that takes advantage of the skill set that I have." As opposed to having to relearn everything. I think that is actually one of the things that is very important, that we are seeing, first with Spirit and Opportunity and people like John Grotzinger. John got involved in that because Spirit and Opportunity had cameras of sufficient resolution and mobility sufficiently good that he could be—the same scientist he is on Earth, he could do that on Mars. And that was totally different.

There's a thing that is happening, which I'm really excited about but it has some downsides, too—Mars is being transferred from planetary science to something that looks a lot like Earth science. Planets used to be studied in a very characteristic way with orbiters that used spectroscopy, and things like gravity, magnetic fields, and it was a discipline that you used on planets. The tools that are being brought to bear on Mars, starting with Spirit and Opportunity, and then especially with sample return now, these are all the same skills that Earth scientists have learned over the years. So, many of the capabilities and know-how and thinking is coming from people that were trained as Earth scientists. That's really different. That's a new thing, and it creates this challenge, where if you look, for example, at where the people that are on the Perseverance mission, where the faculty members in the GPS division who are on the Perseverance mission, where are they intellectually within the Division—I'm on the mission; I'm a geochemist. John Grotzinger is on the mission; he's a geologist. Now I'm using those terms in a technical way. This is where we identify our intellectual home. Woody Fischer, he is a geobiologist. Mike Lamb, he is a geologist. Bethany Ehlmann, planetary scientist. So, we have one planetary scientist and the rest of the people spend most of their time studying the Earth. What is happening is that skill set that we learned on the Earth is now becoming enormously relevant for understanding Mars. This is a bit of a disruption. The kinds of things that you used to be able to do to be a successful planetary scientist are no longer the things that are happening, in many ways, on Mars. When samples come back, this will be complete, that all of these tools which have been developed for, for example, studying the ancient Earth, they are exactly the tools that will be brought to bear to study ancient Mars. I'm really excited about that, because it's a very rich background to bring. But like I said, it's also a disruption, in that the community is going to have to change. The community that studies Mars is going to have to change. And change is always challenging.

ZIERLER: The fact that Curiosity had science objectives that were within your area of expertise in the way that Spirit and Opportunity did not, what does that tell us just more generally about the expanding science objectives of the entire NASA JPL Mars mission?

FARLEY: One of the things I was surprised by when I became project scientist is how the arc of Mars exploration was planned. I generally believe that science seldom follows an arc that you can predict. But what was clear is that JPL and NASA had developed this plan. Once the rovers were established as the way to explore Mars, this idea that gets phrased as "first, follow the water." So, the first orbiter missions established that the surface of Mars was—what appeared to be evidence for flowing liquid water. That was extremely controversial. Put a rover on the ground, and prove it. Well, Spirit and Opportunity showed beyond any reasonable doubt that there had been flowing liquid water on the surface. Curiosity furthered that. The next step in this trajectory after "follow the water," meaning establish that there was water—Curiosity was tasked with establishing that that water was habitable. And the very first place that Curiosity investigated in detail is a place called Yellowknife Bay. It turns out to be a lake deposit with neutral pH fluid, and relatively low salinity. If that environment had been on Earth at the same time that it was on Mars, it would not only be habitable, it would have been inhabited. That's a very powerful statement to make. But the next step in this arc is the objective of Perseverance to look for signs of ancient life, and therefore motivate sample return.

What I find amazing about this is, there were people at JPL who thought this through, 20 years ago. They said, "This is the arc we're going to follow. First we have to do this. Then we have to do that. Then we have to do this last thing." Perseverance and Mars Sample Return are sort of the apex of this process. In one sense, it is enormously successful, in that it has motivated a lot of very important exploration. I have my own reservations that I think many of the people in similar parts of the MSR and Mars 2020 team feel—that we have been tasked to look for evidence of ancient life. At one level, that is a great scientific goal. At another, it is potentially barren, meaning it is very possible that Perseverance discovers nothing that looks like ancient life, and it is possible that the rocks, when they come back, will show no evidence of ancient life, and one might say that this entire arc was ill-conceived, and it was not a good investment. But that misses the point. The point was ultimately to get samples back in the lab where we can answer lots of questions. That's one of them.

So whenever I am questioned about, "What are you going to do if you don't find evidence of life?"—well, one answer, which I don't particularly favor, is, "Well, we turned over the wrong rock. You've got to go back to Mars and you've got to turn over a different rock. You just keep turning over rocks until you find something." Well, that's not science. That's not the way science moves forward. But what we would be able to do is—and I believe we have already set this in motion—we have sampled rocks from a potentially habitable environment. Again, repeating the same thing I said about Curiosity, I believe that the rocks that we have sampled in Jezero Crater, if they had been on Earth at the very same time, they would have been inhabited. If we don't find life there, that is an important statement about the ubiquity of the origination of life. Also, there is the potential to look to see what prebiotic environments look like. Make no mistake; every environment on Earth, by three and a half billion years, already had the imprint of life on it. So finding evidence of what the prebiotic conditions were is impossible on Earth. So, that's an important part of it. But I think that I find as sort of a slam-dunk reason to have done this arc, is to understand how Mars climate works and how it worked in the distant past, what the magnetic field did, what are the ages of all of these great features that we see. What that does is it turns, in a similar way to what I just said in terms of the scientists who study Mars, it will turn the history of Mars into a much richer quantitative tapestry, much more similar to Earth, than what you would ever get from just flying orbiters and looking at the ground from an orbiter.

Basically, this arc was all about seeking life, but many people knew—it was the way to further this other set of goals. There's a little bit of an interesting decision-making process—let's put it that way—that government uses to explain why it chooses to do what it does. One of the ones that seems to be quite easy is to tell the public, "We're looking for signs of life beyond Earth." Most scientists that I interact with are not that interested in that question, because they don't know how to approach it. They are far more interested in other kinds of nitty-gritty questions about the way planets work, or what the history of planets has been. But that's much harder to sell. So, we kind of hide behind that. I don't think that's the healthiest thing in the world. I watch my colleagues in other fields, like LIGO—LIGO does not try to say, "We are looking for signs of life." Or CERN, looking for the Higgs boson, they don't try to explain it. They just have to deal with the fact that most of the public isn't going to be able to understand it. It's a decision that gets made, and I think in some ways it doesn't do justice to what the science really is.

ZIERLER: Isn't another problem with the approach of, "Well, we just have to go and turn over another rock"—what you were saying in a previous conversation—if there was life on Mars in the past, like on Earth, wouldn't it be everywhere? Isn't the power of extrapolation fairly powerful to say that if we've looked at a sufficient—however you define sufficient—number of examples, if there's no evidence here, we don't need to haunt ourselves with the idea that we didn't look in this corner of the planet or under that boulder over there?

FARLEY: I think I agree with that, subject to one consideration. There is no rock record on Earth between about 4.5 billion years ago when the solar system formed, and I think the oldest rock which is not completely messed up by metamorphism is something like 3.6 billion. On Mars, there are rocks from that time period. The reason that matters is, I think, if there was a terrestrial rock record that was perfect, going all the way back to 4.5 billion years ago, you might well find rocks that had no life in them. Those rocks have been destroyed, and so they don't pollute our thinking about Earth. As soon as you see good rocks, well-preserved rocks, they have evidence of life in them. On Mars, that may not be true. One might then say, "Well, there was no life at whenever Jezero Crater formed, but maybe it formed just after that. Maybe life originated just after that, so keep looking." But that's not a strategy. It's holding out hope for something happening that I don't think should motivate what we do.

I guess the question is, what is the objective? Why did this arc motivate people? Why would 20 or 25 years ago, when people first started saying, "First we're going to do this, then we're going to do that, then we're going to do the other thing"—it was all about looking for signs that life might have existed on Mars—what is it that excites people about that? I'm not really sure I understand the answer. This is kind of a philosophical question about why we do the things that we do. In many ways, it's not that much of a science question. Let me play devil's advocate here, which is, I could imagine, and maybe I even think it personally is likely but I cannot defend it—I think it's likely that there has been life on Mars, and it may even still exist there today. I can't prove that, and it's just an instinct. But, we bring these rocks back, and we will find some degraded evidence, meaning degraded by three and a half billion years of radiation, and we say, "Yep, that looks like there were microbes living on Mars." How do you take that to the next level? Like what do you do with that piece of information? As I have indicated before, I think there are some really interesting scientific questions that you then have to grapple with, that you could be grappling with now, like, "What is life? How do you identify it?" I can't remember whether we had this conversation, but there are people who believe that there is non-DNA based life on Earth, shadow life. It's a fascinating possibility. So, there's already reason to be wondering about, maybe there's life as we don't know it, on Earth, already. I do wonder what we will do with that piece of information, in contrast to—all of the other things which I said, I know exactly where they go and how they start answering some of the puzzles of the way the solar system works, or how our solar system works, and that kind of thing.

ZIERLER: I'll just note editorially, the philosophical question, "Why do we do this?"—it brings to mind George Mallory, the Everest explorer. He was asked, "Why do you want to climb it?" "Well, because it's there." The other three-word quote that comes to mind is of course Charles Elachi. It's, "Dare mighty things." It's because it's there, and because we can. To counter the tenor of the rhetorical question you posed—"Well, what do we do if we don't find life there?"—isn't another powerful statement simply that if we don't find signs of life on Mars and we have proven our capabilities to look for it as well as we have, isn't that in and of itself also a powerful statement, about potentially how unique life on Earth is? In other words, Mars, with a fairly similar geologic record, where the logic, the thinking is, "Well, if it happened on Earth, it should have also happened on Mars," if we don't find any evidence of it, it is to me at least a very powerful statement potentially of just how unique Earth is.

FARLEY: Yeah, and sometimes, when I'm giving a public talk, I will say the following: that until about 15 years ago, I think most scientists and certainly myself included, if we were asked, "Does life exist beyond Earth?" most of us would have said, "No." No scientific rationale for that; we would have said no. I think if you ask that same group of people—myself included—today, "Do you think life exists beyond Earth?" almost all of us would say, "Yes." What has changed has nothing to do with Mars. It has to do with the fact that there are billions of planets, and it just becomes statistically far more likely. That's not science, either. What is hidden in there is a supposition, and that supposition is that life is rare, its origination is rare—or maybe it's habitability is rare; I'm not sure which, one or the other. But if you put planets out there, life—if you give life enough opportunities, it will originate. I don't know how you make progress addressing that as a scientific question: what is the ubiquity of the origination of life? One way to do it is effectively what you just said. Go to a place where you think life could have existed, and see if it does. Mars is such a place. If we show that there is no sign of life in Martian rocks, of a time when it would have been habitable, then at least you know it is not 100%. You've looked at two places, Earth and Mars, and honestly, on any kind of timeframe that I can foresee, our timeframe, that's about all we're ever going to be able to do. I don't think we're going to be able to develop capabilities that can tell us whether life exists on exoplanets. So this is going to be a very slow process. Well, you can at least move forward and change from a statistic of one, the Earth, to a statistic of two, Earth and Mars. [laughs] So, it's slow progress, but I think that's an important way to look at it, that a negative result is at least a useful negative result. It says something about the ubiquity of life.

Now unfortunately, there's a whole other thing, which I find fascinating, which is the possibility that life has been exchanged between Earth and Mars. It sounds like a kooky idea but it's actually not that kooky. There are more than 100 meteorites in our collection that unambiguously originate from Mars. A Caltech student years ago showed that those fragments of Mars that are in our collection were never heated to a sterilizing temperature in their transit from Mars to Earth. That raises the possibility of life being exchanged. So if we do find evidence of life, the next question you have to ask is, is this an independent origination, or is it panspermia? It's not my field, but I think this is a great thing to ponder—how could life have been interchanged among planets?

ZIERLER: Just in generational terms, the idea that none of us today will live to see the question of whether we can figure out life on Earth on exoplanets, but we have Mars right now. What about the icy worlds? What's the timeframe there?

FARLEY: When I look at that, I see—an idea, that there is liquid water below the shell of ice. I see a shell of ice that is kilometers thick, and I see a hope that somehow that water can get out and onto the surface and still record evidence of that life. If that doesn't work—and we'll learn a little bit from Clipper; we'll potentially learn from the geysers on Enceladus—but if it isn't visible on the surface, we are a long way away from being able to penetrate that ice and see what is below. I just don't see that happening in a 50-year timeframe. To go to Europa and bore a many-kilometer hole through the ice to put an instrument in the ocean, that would be fabulous. It also just doesn't seem like it's in the cards in anything like the middle term.

ZIERLER: Did you have an official title or affiliation with Curiosity?

FARLEY: Yeah, what's called a participating scientist.

ZIERLER: What were your first impressions of JPL culture?

FARLEY: I didn't really see much of JPL culture on that mission because I was working on the science side, working with the science team, which is multinational. I saw more of the JPL side when we were working on the development of this mass spectrometer and developing a proposal for the Europa Clipper mission, and then for sure when I started in 2013 as project scientist for Perseverance. As I mentioned earlier, culturally it is very different. It is different as a practical matter, with you've got to go through security and wear your badge all the time, and many of the doors are locked. Even people who are working there, I can go through this door, but I can't go through that door. That is very different than campus. The other really big cultural thing is that on campus, it is normal, and in fact it is even encouraged, to think about a problem that you can make incremental progress on. Hoping for big progress, but work on something year after year after year. Sometimes it goes slow, sometimes it goes fast. Every scientist will tell you that. You're going along, and then something drops in your lap, and you suddenly make a huge leap forward. It typically doesn't come in steady progress. Very different than JPL. JPL is mission-oriented as NASA is mission-oriented. For NASA, a mission has a timeframe, and you've got to get it done on that timeframe, and if you didn't get it done on that timeframe, you hang it up and move on to the next thing. That is really different.

There are scientists at JPL, and some of them spend a lot of time working out, say, a proposal for an instrument for a flight mission, and they'll spend years putting together the prototype of this thing and then writing the proposal, and then maybe they get the proposal funded to develop it a little bit. Then they submit it for the mission, for example Europa Clipper, and it doesn't get selected. Okay, well, done with that! It's really different. To be a scientist, it makes it much harder. Because you have a timeframe; you've got to make it work. If you don't make it work on this timeframe, okay, you're done. Whereas a lot of the ideas that I work on, or I see my colleagues working on, like I said, it's incremental progress, until it's like, "Wow, okay, had the big breakthrough, and wow, this works great." You can just stay at it for the long term. That's just different than JPL.

ZIERLER: As you were explaining, as division chair, the challenge of generating new ideas, what was the transition process like? If you could just think about your publication list circa 2010 to 2012, when did Mars research really begin to be a large part of the things that you were doing, not just in your JPL world, but in your Caltech world?

FARLEY: My first paper that was truly about Mars was the attempt to date the Martian surface using the SAM instrument on a Curiosity rover. I think that came out in 2012 or 2013, something like that. There were several other papers that I had a student working on, looking at other aspects of data coming from Curiosity. But it was not a big component of what I would consider to be my research time. As participating scientist, I think it supported maybe a month a year of my salary, and that would give you some idea of what my level of commitment to it was. But when I became project scientist, this is not a road to publications. Being a project scientist of a mission that is starting with a blank sheet of paper is not a road to publications. I'd have to go back and look, but I think the first publication about the Mars 2020 mission probably for which a real scientific paper describing what the mission is going to do, that probably came out in about 2018. It wasn't until about two months ago that a paper that I led actually described science from the mission. That came out in September of 2022, and I started in early 2013, so that's nine years with no scientific output from it. There are a few papers describing what the mission was going to do, but the first real science that came out that my name was on, and which I made a major contribution to, it was nine years. So, this is not a way to generate a lot of science. I knew that, and I was okay with that. Totally fine with that.

ZIERLER: The nine-year timeline, is part of that just the happy fact of how long-lived Curiosity is, that it just keeps going and that there is more science to get from it?

FARLEY: Sorry, that was on Perseverance. I was being sliced too thin, so I stepped back from Curiosity. Those positions called participating scientist, they're kind of an add-on to the mission, and when I stepped back and released the funding that I was getting, presumably they went and hired somebody else to try other new things on Curiosity. I haven't worked on Curiosity for maybe five years.

ZIERLER: For the last part of our talk today—and our next talk we'll pick up—we'll sort of step back one year in the chronology, when you start with Perseverance. When it was time, when you were coming up on your ten years as division chair, when you looked back, when you reflected, what you were proud of what you accomplished?

FARLEY: Ah! Yeah. I had mentioned that when I started, I had been admonished something like, "It's working great. Don't break it." So the thing I was most proud of is I think it was still working, when I got through. But there had been some challenges. I mentioned that we acquired what became Linde + Robinson, and now it's just called Linde—the Linde Center, the Linde Building. One of the interesting challenges culturally is that the Environmental Sciences Program was cross-divisional and had a sense of independence, historical independence, that made it hard to digest into the same model that the rest of the Division operated under. I don't think we ever—although that program is scientifically great, and a lot of that happened in the time that I was chair, I certainly don't claim credit for the science, but for facilitating it, it was an important thing that I think I contributed to. The challenge is to keep the cohesion going, even though you're bringing in essentially a new tribe, and that tribe has a historical independence. That's the plus and the minus of that.

One of the things that I supported using division funds early on was John Eiler's research to do something completely different than almost anybody else had really thought of with stable isotopes. I'll just give you the one example, which was a real payoff. John got interested in the idea that if you looked at calcium carbonate—you can stop me if you already know this—but in calcium carbonate, it has been known since Sam Epstein's day—Sam Epstein was a Caltech professor—that the oxygen isotope composition, the ratio of O18 to O16 in the calcium carbonate, is a thermometer. You can learn what temperature that carbonate formed at, as long as you know the oxygen-18 to oxygen-16 composition of the water in which it grew. That becomes a problem the farther back in time you go. It's okay for short time periods, but when you go back long time periods, it is very problematic. What John did is he looked at the idea that you could take advantage of the fact that the CO3 group in calcium carbonate has a carbon and an oxygen. Following up on something that was I believe suggested by the real pioneers in stable isotope geochemistry, people like Harold Urey in the 1950s, they recognized that the relative affinity for a carbon-13 to marry an oxygen-18 instead of an oxygen-16—the heavy carbon going with the heavy oxygen, or the light carbon going with the light oxygen—that that itself is an internal thermometer. Then you wouldn't have to know the composition of the water.

John had this idea, and it required the development of new instrumentation, and it required money to develop that instrumentation. Over the years, I provided division funds to really make that happen. Because that's so close to the stuff that I do, I feel really good about it, I understand it, and I don't think it would have happened in any other way than in the Caltech way. John was able to get the resources to do it, he was able to convince the manufacturers of these instruments—"Hey, here's a new thing. Caltech is backing me on this. Can you build this instrument for me?" It has been a huge advance. I think most places, the professor would have gotten that idea, the institution would have said, "Good idea, go write a proposal," it wouldn't have gotten funded because there's natural conservatism in the funding of federal grants, yadda yadda yadda, and it never would have come to fruition. I think that's a big success story.

ZIERLER: In all the ways that especially in recent years Caltech has tried to become a more diverse and inclusive institute, were people talking along those lines? Was the language of DEI in the air when you were division chair, or is that more of a recent development?

FARLEY: We definitely didn't use those words, and to be honest, we have to start with a potentially—even in 2004 when I started, we knew very well that we had a problem, most glaringly with the fraction of female faculty. Also a very non-representative racial makeup. The reason why I point at the male-to-female ratio is because it is easy to look at the statistics and show that we are way behind where the pool of applicants is. For racial diversity, that isn't really true. Geological and planetary sciences, broadly defined, they are not very diverse, even in the student pool, and especially in 2004 they weren't. We were definitely aware of this, had lots of conversations about what we were going to do about it. I'll just make the observation that progress is slow. Progress must be slow, unless you do away with tenure. Caltech, as I mentioned earlier, at least in GPS, many people, myself included, spend their entire scientific career as a Caltech professor. I started at Caltech in 1993, and I think it very unlikely I will leave before I retire, so I will have done maybe 35 or 40 years, not giving an opportunity to create diversity. If you have that situation, and you are not going to expand, then turnover will be slow, and diversification will be slow. It doesn't matter whether that's for racial diversity or male-female ratio diversity, or anything. So, we've made progress. We're still not there. But we were definitely talking about it.

The kinds of conversations that I thought were maybe more interesting, other than, "Hey, we have a problem, we should do something about it," there were interesting conversations about, "How do we use the Caltech model, or at least the GPS model, to solve this problem?" That model involved bringing in promising postdocs and getting the first shot and seeing whether they will succeed. GPS has a model that I would say is dear to the hearts of all of us, that we hire junior faculty members. There are very few senior hires that have been made over the decades. There are a few prominent ones like John Grotzinger. I was responsible for recruiting John, and it was quite an unusual thing for us to do. In other divisions, there is no such consideration, and you can simply poach a prominent professor from another institution that brings you the diversity that you wish to have. The interesting part of that is, have you done anything good for the world, if all you are doing is you are solving your problem at the expense of somebody else? Some other institution now has one less element of diversity. So I felt good, and I still feel good, that the right way to do it is to create opportunities and use them. But I'll also be honest and say it's kind of remarkable that, at least when I started, there were still faculty members who held very deeply sexist views. At least from my perspective, the overt sexism and racism is completely gone. Good riddance to it, but it was surprising to me, especially in my early days, like, "Oh my gosh, did that person just say that?" These things take a long time to wash through. For the reason that I just said, we are challenged to change quickly.

ZIERLER: Last question for today. In the way that when you became division chair, the overriding advice you got, or marching orders as it were—"Don't break the Division"—as you were handing the baton to John Grotzinger, either by your personality or by the situation as you saw it, was that the same kind of advice that you passed on?

FARLEY: Oh, yeah. It's not a surprising piece of advice. I think the approach that I used as division chair is probably obvious. I didn't have a vision for what it should be. I didn't think that I had any ideas that were any better than anybody else's ideas of what we should do. I think most people really like that. I definitely know departments where a department head has a vision and tries to implement it. I think the Division likes being in control of their destiny instead of having it told to them. No doubt when John started, his goal was to sort of keep that going. But I would say there were already elements that were going to make that challenging. The Division has gotten bigger, and it has brought in these new tribes that make it a bit more challenging. There's this underlying debate that happens at the Institute level—"What is the right size of the Institute?" I would say it is common for Caltech presidents to arrive and say, "We need to get bigger." If you look at some of the things that David Baltimore did in his early days, some of the things that did not go anywhere, like the acquisition of the Saint Luke property, these were ideas that we could make Caltech bigger. I don't think most faculty members really want to see that happen. But it becomes then a challenge of we are nevertheless growing bigger, and how do you accommodate that. It's an interesting challenge to not always be growing, not solving your problems by growing. John has overseen some growth, and that is a challenge. But yeah, I think the general advice is, "We've got a special thing. Don't mess it up." That's a whole separate conversation, but sailing into the pandemic, John was faced with a lot of—all of us were faced with challenges that I think really shook everything that we do.

ZIERLER: Next time we'll go back 2013, the beginning of your relationship with Perseverance. We'll go from there.

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, January 6th, 2023. It is great to be back once again with Professor Ken Farley. Ken, as always, it's great to be with you. Thank you for joining again.

FARLEY: Thank you.

ZIERLER: Today we're going to pick up right at the transition point in your career from division chair at GPS into your increasing involvement at JPL. First, to set the stage, would you say that being division chair broadened your interface, your interactions, that might have made those growing collaborations, interest at JPL, more possible than otherwise might have been the case?

FARLEY: I would say that the experience I got as a division chair was to understand better how JPL functions. JPL is a very intimidating place. I had some interaction with them as a junior professor, and it is intimidating just even getting access. Because I routinely was interacting with JPL-related issues and spending time with the director and various other folks from JPL while I was division chair, I began to understand better how it worked, and it became less intimidating. As a practical scientific matter, I don't think it made much difference, but I at least understood the way the place functions, which is very different from the Caltech campus.

ZIERLER: By being division chair, just with that greater purview around GPS, did that get your mindset into a less terrestrial place? Did that help in terms of thinking about where you might contribute in Mars exploration?

FARLEY: Not really. JPL does a huge amount of stuff that is terrestrial, and I would say I actually knew more about that, over the years, and less about the planetary part of it. When I started on Curiosity, that was when I really got engaged with the planetary science activity, which then was driven by this capability that seemed very similar on Curiosity to what I have in my lab. That was the natural connection into it. It really was through this technique rather than a broader interest in planetary science.

ZIERLER: How well-developed was Perseverance planning by the time you joined around 2013?

FARLEY: It was completely notional, and there were a handful of engineers who had been working on it for a few months. I was brought in very early. With that said, though, the expectations of what the mission was going to do and how broadly speaking it was going to do it, was well-established. As an example, there was a very strong desire to do what is called build to print, which is take the Curiosity vehicle, take those plans, and rebuild. This is very important, because one of the things that Curiosity had to come to terms with when it was being developed, that the Curiosity team had to deal with, is lots of different ideas. "Well, we can do it this way. We can do it that way." If you look at the evolution of the vehicle that was being built that ultimately became Curiosity, it had a bunch of different manifestations. In contrast, we started with build to print. We also started with the idea that to the maximum extent possible, we were going to use leftover hardware from Curiosity. That set the ground rules and actually was hugely enabling in the sense that we could focus on the new things, and not worry about the simple functionality of having something that could be mobile on the surface of Mars. All of that was at least understood what needed to be done. I will not call it easy, but I will say it was at least understood how to do it.

ZIERLER: Building on that infrastructure where the engineering is already there, how does that enable the possibilities for the science objectives of Perseverance?

FARLEY: The major consideration that I was involved in early on was, what sort of scientific instruments generally speaking are going to be useful for this. I did not participate in the selection of instruments. It's a little bit strange that the instruments were selected by an external team who was not responsible for actually fulfilling the science objectives. I think there's a problem with the structure, where I was deemed to be conflicted, because I was associated with an institution that was submitting proposals. This is not a smart way to do things, to have the person who is overseeing the science not be involved in the selection of instruments. Nevertheless, the instruments were selected. Once the instrument selection was done, then the goal, the major objective that I had, over quite a few years, was to make sure that those instruments could be successfully realized, and that they had very clear capabilities that would survive the development process. It is perhaps not obvious, but some of these instruments were proposed that had never been built. It is very easy to imagine, "Oh, yeah, it's going to do this, and it's going to do that, and it's going to do the other thing. It's going to work perfectly." That's not the way it works. Much of my job was just to make sure that as inevitable development problems occurred, that we could stay focused on the key capabilities and make sure that those capabilities were realized.

ZIERLER: It does beg the question, if you had the opportunity to select those instruments, would you have selected anything different? Would it be reconfigured in a different way?

FARLEY: It's probably not politic of me to pass judgment on that. We have the instruments we got, and they are serving the team well; let's put it that way. I think that's the safest thing to say. There are two other major areas that were new, that we needed to develop, and which I think from looking at what my responsibilities were during the development phase were much more core. One was the development of the sampling system. That had never been done before. The idea of collecting a rock core was always the objective, but how are we going to do that? And how are we going to seal the sample tubes? What would be good enough, in terms of cleanliness, being free of terrestrial organic matter and terrestrial microorganisms? How would we prove that they were good enough? That was a very large focus. The other reality that became apparent to me was that we were being asked to do something that seemed very challenging, is very challenging. We were going to be Curiosity in terms of doing scientific exploration and using the rover instruments, where we were going to explore the landscape and learn all about it, and by the way, we were also going to collect samples for MSR. That's effectively two different missions being stuck together. All of this has to be done in the amount of time that is available on the rover, so being efficient and staying focused, right from the get-go, it was clear that it was going to be a big challenge.

ZIERLER: From those first notional moments of your involvement, when are you named project scientist? Is that right out the gate or that is something that develops over time?

FARLEY: That was the title I was given as soon as I was offered the job.

ZIERLER: From that moment, what was your sense of how much this would take over the rest of your research agenda?

FARLEY: Since I was offered that position in 2013, it was clear that in 2014 I was going to complete my term as division chair. I felt comfortable with a 50% time appointment. The expectation was that that would continue. There's always the risk, a very real risk, that development will not come to fruition, that there will be something; Congress doesn't approve the money, something goes wrong, the mission gets cancelled, whatever. I was committed to staying the course at a 50% time commitment. As long as it was going forward, I was going to be a part of it. We survived all of the challenges of development, and there were times when there were major issues that we managed to get through. But towards the end of that period, so in, say, 2018, 2019, I could see that I could actually do science. That period was not doing science. There was zero scientific publications of mine that came out of that. It was all about making sure that the rover could do the things that it needed to do. The payoff of that investment is, get on Mars, and be one of the explorers that is helping guide the mission. Towards the end of the development period, the big carrot became, "Oh yeah, let's get to Mars." That's what motivated me from there.

ZIERLER: For those years, where does that leave your research group? Are you able, does it make sense, to take on new graduate students at this time?

FARLEY: I had become pretty efficient during the time as division chair, in keeping my group going on 50% time. The 50% time on Perseverance was different in the sense that much of that time, close to 50% of the time, I was not on the campus; I was at JPL. My time was not my own. Almost all of the division chair jobs, you can do them whenever they fit into your day. But one of the cultural differences between the non-academic side of campus and JPL is JPL functions on a daily schedule of meetings. It's a bit intimidating to look at a calendar where pretty much every minute is scheduled, meeting after meeting after meeting. That's just not the way you go about your—it sounds a little bit like classes on campus. And yes, classes do work like that. But in terms of the research life on campus, at least the way I run my operation, I'll work on this for a little while, and I'm going to get distracted, and I'll work on something else, work in the lab and work on data for a little bit. It was a very different sort of thing. "I am not here. I am not available, because I am up at JPL." In that time period, my group remained pretty much stable size. It began to grow towards the end, I think partly because I acquired some very talented people in the lab who were able to not only take on the instrumentation but actually work on the intangible group dynamic. Part of the role of the leader of a research group is to be a social leader, to encourage everybody and to help everybody when they have challenges, and to get them to understand basically what they are doing, not from the technical point of view, but just from the big picture. Like, "Okay, we're all working together on this thing." I was able to acquire a lab manager who was very good at filling that part of the role that I could not do because I was away so much.

ZIERLER: What about graduate students who might be interested specifically in Mars? Would that have been a new class of grad students and postdocs who would be motivated to work with you during those years?

FARLEY: That's an interesting question. When I was on Curiosity, I had one graduate student who I think was quite successful. But in general, I make the observation that it is very, very challenging for graduate students, maybe a little easier for postdocs, on missions like Perseverance or Curiosity, because there are literally hundreds of team members, and at least 100 graduate students, maybe more, who are all trying to use mission data to further their thesis work. There's a very intense competition. That's the first thing. You've got to identify a piece of the pie that you can own. Because when you're a graduate student working on a thesis, you can't be the 20th author on a paper. You're not going to get a thesis approved if you are the 20th author on every element of your thesis. You have to have a thing that is your own. That's hard, to identify what that will be. The other is, there is a very substantial risk that the mission will end prematurely, and especially during the development phase, during the time when I was in development for Perseverance, having a student working on Perseverance just didn't make any sense, because there was no guarantee that they would ever get any data. I don't have any students now that are primarily involved in Perseverance. This one graduate student I had on Curiosity, as I said he found a niche and we got some interesting data pulled together and interpreted and wrote some papers on it, but it is a very challenging aspect of a mission.

ZIERLER: I wonder if you could describe the reporting structure for the mission. As project scientist, who do you report to, and then who are your direct reports?

FARLEY: In terms of who reports to me, at JPL I had two deputy project scientists for a time, who are JPL-ers. It has since been reduced to one. It's a former student of John Grotzinger, a former Caltech graduate student named Katie Stack Morgan. She and I work very closely together, and when I had the second deputy, the three of us basically divided the landscape so that we could keep the job manageable. Then also in my group at JPL were a team of what we call investigation scientists, who are a JPL-er who is a liaison person between what we called the Project Science Office—that's the group that I headed up—and the scientific instruments that were being built. Most of those instruments were not being built at JPL; they were being built elsewhere, by a team of people who are not associated with JPL. The communication is always challenged when you have a group of people that are working elsewhere on a complicated piece of hardware. The idea is that we could have one of these investigation scientists who would be responsible for being the liaison. That was my group. It was a handful of people, and we were fulfilling those roles.

Now I'm going to answer your other question, because it made me laugh when you asked it. My reporting path—being a professor is a strange situation, because you don't really report to anybody. Maybe you report to your division chair, but your division chair does not come looking around once a week to see what progress you've made. Maybe you will meet once a year for an hour and just talk about what you have been doing, and any challenges or discoveries that you have made. Then what is especially odd—towards the end of development and now, I'm supported between 80% and 90% time to do the Perseverance mission, which is my central focus. I am not a JPLer, so JPL does not have oversight over this, and this is not really something that anybody on campus has oversight over. I have often pondered that nobody is actually providing guidance.

This is a challenge, because one of the very curious things that we got into during development—as I told you, we were focused on preparing samples for Mars Sample Return, but we were not allowed to talk about that. We were not allowed to talk about it because Congress had not yet approved the follow-on missions to bring the samples back. There's a very clear guidance that everybody gets given, to not get out in front of Congress. Congress needs to make decisions, and if you say, "We are building this rover for Mars Sample Return, which is going to require two more missions in the future," you are getting out in front of Congress. So we didn't talk about this, which means that to a very large extent, we had to figure out what we were doing, from a scientific point of view, in the background, with nobody providing instruction, like, "Yes, do it this way," or "This is the most important thing." We had to figure it out on our own, which gives one a lot of autonomy, but also when there are challenges, you kind of scratch your head and say, "Am I doing the right thing here?" [laughs] That has been an interesting aspect of the job, to be kind of on my own for a lot of it.

ZIERLER: That begs the question, with that relative lack of structure from you going up top, where does that put somebody like the director? What was Charles Elachi's involvement in the early years?

FARLEY: I think he was very much engaged with the engineering part of the mission, just because making sure that the implementation succeeds is a big element of it. We met with—we would be the project manager—the project manager is the equivalent of the project scientist but on the engineering side, and they have responsibility for the construction of the whole thing—we would meet with Elachi once a month. I would say Charles's great contribution was, if you brought to him a problem—"We need this" or "We need that" or "This rule is causing us a problem"—he would go and get it fixed. He was very responsive. But in terms of the details of what we were doing, that's just not what the director does. The director doesn't get involved in weeds, at that level.

ZIERLER: What about in the transition from Charles Elachi to Mike Watkins? Obviously very different people, very different leadership styles. Did that change things for you at all?

FARLEY: Yeah, because Elachi's background I think was in radar, and he had a vision for what the lab as a whole could be, but he was not a rover expert. Mike Watkins had done a lot of the development and the early operations of Curiosity, so he knew a lot, and he had very strong opinions about how it should be done, opinions that I did not share. To some extent, when you have a conversation with somebody who doesn't really know the details, you can own the conversation, but when you're discussing something with a leader or somebody you need to respond to, who does know the facts, it becomes a little more challenging to find the answer. There were several examples of this. One of the interesting things that occurred during development was the—I will just call it the imposition of the Ingenuity helicopter on the mission. The Ingenuity helicopter was not part of the scientific payload. It was not selected, at that stage. It was added later, with, as far as I could tell, no consideration for what it would do to the science mission. The Mars 2020 project had a very strong opposition. It sounds weird, but the project management side did not want the technical complexity of getting this helicopter on board, and the science side—me—we didn't want this because it was going to consume time on Mars that we felt like had been already—we had a set of scientific objectives that we were challenged to meet, and we didn't need additional months of operation of Ingenuity to get in the way. It was clear, starting with Charles and then continuing with Mike Watkins, that this was an institutional priority, to have this helicopter, and the answer was basically, "Yeah, we understand it is going to have a negative impact on science, but so be it." Which I found quite frustrating.

ZIERLER: I wonder if you can talk a little bit about what guidance, either at the day-to-day level, or strategically, that the Decadal process plays in formulating the science objectives for the mission.

FARLEY: The Decadal Survey that prioritized Mars Sample Return was hugely important in simply getting the ball rolling. I think that came out in 2013, that that was prioritized. The whole MSR campaign, starting with what became Perseverance—that's not what they called it, of course—but that nucleated what was called the science definition team which was a collection of scientists that envisioned broadly what Perseverance should do. That got that ball rolling, and then they created a document that then was provided to the Mars 2020 mission. We stuck close to some of it. Other aspects of it, we were not able to follow as closely. The confirmation of strong support, or the demonstration of strong support for MSR was very important early on. Because at that time, there was I would say a very strong community of people that wanted a Europa mission. If you look at the decadal survey, it isn't clear that both of them are supportable, and the decadal survey prioritized Mars Sample Return over Europa. NASA managed to support both missions. I think that is, in the long run, going to be a giant challenge—a giant financial challenge and a giant challenge on personnel at JPL. It has been, and will continue to be. But fortunately, we got to the launchpad and made it to Mars, so we're doing our thing already. More recently, just within the last year or so, the decadal survey came out again supporting the follow-on missions to bring the samples back. So we have gotten very good support, which is really important. The scientific community wants to see Mars Sample Return happen. Which I think is useful to take the temperature of the science community, but it's very important to show to Congress and to NASA itself, "This is what we should do."

ZIERLER: I wonder if the budgetary situation—2011, 2012, coming out of the financial crisis—if appetite or excitement over Mars Sample Return really made what would become Perseverance more viable than it otherwise might have been.

FARLEY: The way I understand it—and this is consistent with what I saw but I was not in the room at the time—as you might recall, the landing of Curiosity was a—the media run-up to that, the whole "Seven Minutes of Terror" video, the whole "Dare Mighty Things," this was out there. Then it was just a spectacular success. Obviously technically it was successful, but it engaged the public in a way that hadn't been seen in a long time. NASA successes are spread out over time, and this was deemed a—even though it was simply a technical feat; it didn't actually accomplish any of the scientific objectives of the mission—it was necessary to have it happen, for sure, but you couldn't tick the box that we had now done the thing that we set out to do; we have done something on the way. But the feeling of, "Wow, this is really successful" was immediately followed by, "What's next? We've got to get started on what's next, because it takes years of development to do what's next. How can we capitalize on this success?" The whole MSR thing, Perseverance with a build to print of Curiosity, as a first phase of it, that was a big part of it. I don't know the details of how the budget actually worked in the early days. I didn't pay that much attention to it. It's clear that the Science Mission Directorate is a small part of the entire overall NASA—with the human program. It is a small player, but it is one that gets frequent attention. I think that's a big part of how the resources get allocated.

ZIERLER: This is as much a leadership question as a science question. As project scientist, obviously you have your area of scientific expertise, but the overall science objectives for the mission go beyond where you're the expert in the room. How do you delegate? How do you figure out who to trust? Where do you need to read up on this or that so that you're the expert yourself? How do you manage all of that in areas that are outside your wheelhouse?

FARLEY: These investigation scientists were part of that. Once we acquired the instruments, which occurred in 2014—a year after I started, we had a team of scientists. It's interesting in that that team of scientists were associated with their investigation and less with the overall mission. They had a set of things that they wanted to do, which they were very expert in. So, we had a ready pool of experts to reach out to, but their objectives were not necessarily perfectly aligned with the overall objectives of the mission, which as I said had this component of sample return, as opposed to a purely curiosity-driven exploration. I'll use the awkward phrase that the Curiosity mission is curiosity-driven. When the team is interested in looking at this rock, they can spend as much time as they want looking at it. We can't do that, because we must get on with sampling. Our central reason for existence is to provide the samples for MSR. In dealing with those experts, I also had to recognize that in some cases their objectives are well aligned with my overall objectives, or in some cases they aren't. It took some time to figure out how to balance those two things, and getting advice from people.

ZIERLER: What level of institutional partnership was there with the European Space Agency in at least the early years of Perseverance?

FARLEY: ESA is not a substantial player. There is European involvement through the French space agency called CNES, which I don't know what CNES stands for. They provided support for one of our instruments, the SuperCam instrument. Also, Norway and Spain. Norway, Spain, and France, through their national space agencies, provided instrumentation. But ESA itself was not and is not a major player in Perseverance.

ZIERLER: What does that mean in terms of ESA's role in Mars Sample Return? Is that something that develops later on in the narrative?

FARLEY: Yeah. Through an agreement between NASA and ESA, they are partners from the get-go on the follow-on missions, and they are responsible for building one element of the follow-on missions. They are building the orbiter which will capture the orbiting samples and bring them back to Earth. They are actually building that component. That's right from the get-go, they are partners, and that's a new development, and a necessary development to broaden the international interest and spread the cost more broadly.

ZIERLER: When you started, it was notional, it was just an idea. When did Perseverance begin to feel real for you? Was it with the acquisition of the instruments in 2014? Would that have been it?

FARLEY: No, because they were still on paper. I would say once every few weeks, I would walk over to the spacecraft assembly facility, so the giant room that the things are on the floor. The first time it started to feel real is when the build to print items, and especially the items for which there were many spare parts around, when they started to come together on the floor. The first thing that came together on the floor was the descent stage, the thing that actually allows the spacecraft to land. To see all of that hardware and see how big it is—it's not just a little sheet of paper—you're like, "Wow, that thing is huge!" And the little people are walking around the thing, out there on the floor. I did not go on the floor, because you have to be all bunny-suited to do that, but there's an observation platform with windows, and I would often go there and look in. It was very fun to watch the pieces come together. That's when it started to feel real, when the hardware was actually in place. Some of it appeared to go very quickly because the parts were assembled elsewhere and then brought, and bolted on. Some of it grew very quickly. That was very fun to see.

ZIERLER: What were you most personally excited about with the scientific instruments? In the duality of you have these outside-looking-in interests because you care about what this thing is going to find, regardless of being project scientist, just wearing your professor's hat, wearing your researcher's hat, what was most compelling to you as the science objectives were coming into focus?

FARLEY: The thing that I get excited by, because it's the everyday thing, is the images that we get back from the Mastcam-Z camera. In the first few sols on Mars, that camera produced this just spectacular mosaic that for me was immersive. It was like, "I am on the surface of Mars." That was great. That's an essential part of the science, is just images. It may seem in some sense low-tech; we cannot survive without the detailed images that we get, mostly from that camera, but from a few of the other cameras as well. In terms of my area of expertise, the instrument that I was most closely following was the PIXL instrument, which uses x-ray fluorescence to produce an elemental map of a rock, which is conceptually similar to what we do in a typical terrestrial laboratory setting. Interestingly, that instrument and its companion instrument called SHERLOC, both being built at JPL, because they were new there were many challenges in their development. For example, the PIXL instrument, it uses x-rays to interrogate the rock. It's x-ray fluorescence. The development of a flyable x-ray tube turned out to have lots of challenges along the way. There were multiple steps where you had a little bit of a fear. "Is this going to materialize or is it not?" The sister instrument, the SHERLOC instrument, which uses Raman and fluorescence, to identify minerals and to identify organic matter, it actually got to the point where it was so technically challenged and so over-budget that it had a cancellation review, which is NASA's formal way of saying, "Should we cut our losses, jettison this thing?" We had to fly to Washington and assess whether it was worth continuing. Ultimately it was decided that we could continue on with some cost-control measures. That actually underscores the inevitable conflict between wanting confidence that you are going to be able to build the thing successfully, and wanting to not go over budget. [laughs] Of course the budget that is involved here is orders of magnitude more than I had ever been involved with before, and as an individual investigator, you do not go over budget. When you are building a giant multi-billion-dollar spacecraft that must make a launch date, sometimes you go over, and you just hope that you are going to be forgiven [laughs], that in one way or another you're going to get bailed out. It's a very different mentality, and kind of interesting to watch.

ZIERLER: As the prospect for astro-biological research on Mars becomes more and more real, what role do you play—the platonic ideal of the project scientist—in the expectations game, in communicating the science about the feasibility of finding life, current or past? What role, what interface do you have with the broader public, who obviously is very engaged and interested in this kind of question?

FARLEY: It is one of the central roles of the project scientist to be out there, interacting both with the big technical machinery—so that is, all the JPL engineers, they want to know what the science is. With the NASA stakeholders, and when I say that, I mean the headquarters folks, who are not necessarily scientists but need to understand, because they have to go advocate in Congress. There's that role, and then there's also just public outreach. I've been involved in a lot of school groups, and astronomy clubs and that kind of thing, giving presentations on this topic. You hit on what I think is the interesting challenge of the mission, which is, it is easy to say to the general public, "We are seeking evidence of life." That's the tagline of the mission—"Seeking evidence of ancient life." Of course they might first not actually hear the word "ancient," and they might be thinking we are looking for things that are alive today. We don't believe that there is anything alive on the surface of Mars today. Maybe below the surface but not on the surface. I found it challenging to not oversell that part of it, so to explain why we were looking in the ancient past. When you are looking in the ancient past, you are almost surely talking about microbial life, and not advanced life. At some level, when you say, "we are seeking evidence of life," that is not a scientific objective. That is an exploration objective, and it is a fine exploration objective. It is a motivating exploration objective. It's the kind of thing that is easy to get people excited about. But it's also important to translate it into a scientific objective.

The reason you want to translate it into a scientific objective that has value whether you confirm or refute the existence of life, you want to be making scientific progress. You don't want the answer to be, "Uch, that whole effort was a failure because they didn't find evidence of life." We started worrying early on—we who are considering the science—"How do we pitch this so that we are not deemed a failure if we don't find evidence of life?" The right way to look at that is—and we started organizing the thought process this way as soon as the landing site was selected—we are landing, and did land, at a landing site that has all of the characteristics that we believe are necessary for life, as we know it—not fanciful life, but life as we know it, should have been able to exist in this environment. On Earth, at the same time, in the same environments, life was thriving. So we are going to go to such a place on another planet. If we don't find life, that says something. That's important. We looked in the most habitable place, at the most habitable time in the history of Mars, in the distant past. If we don't find life, that is an important statement to make. That's different from, "We're going to go grab a rock, and maybe it has life in it," which would always have the answer, "If you didn't find it, you need to go back and look somewhere else." If we don't find evidence of ancient life in these rocks, I think we will seriously need to consider that perhaps there is no life there, because this is the place it should be found. If we don't find it, that's important. That was an important thing for me to get across, to turn it into a scientific exploration. I should also add to that, even if we don't find evidence of life, we are potentially finding evidence, and especially when the rocks come back, of what prebiotic environments on the surface of a rocky planet were like. That is impossible, as we were talking about in an earlier session, to do on Earth, because those rocks are gone. That's how I was trying to engage with the whole astrobiology thing, turn it into a more science-based question.

ZIERLER: If the operating assumption is that there is no extant life on the surface of Mars, is there Martian geology, and does this influence planning for Perseverance, where there is potentially access to caves or other openings where the rover can get access to, that's sub-surface, to potentially collect samples of rocks that have not been blasted by wind and radiation?

FARLEY: No, and there's two reasons for that; one is practical and one is scientific. It wouldn't do any good—it's not just radiation that you need to get away from, although that is a big deal. Anywhere that the rover could get to would be cold and dry, and the cold and dry alone is adequate to rule out all forms of life that we presently know about. When we talk about subsurface life, people are usually thinking about deep subsurface, hundreds of meters below the surface, possibility at the water table, and a cave would not be such a place. That's the sort of science answer. The other answer is a whole interesting other thing that needs to be considered, which is planetary protection. Planetary protection involves two things that are quite different from each other but get lumped together in one name, so I want to distinguish them. There is what is called forward protection, and there is what's called backward protection. Forward protection is protecting Mars from contamination by terrestrial life. Backward contamination is bringing anything that is alive on Mars to Earth. One protects Earth; one protects Mars.

Mars 2020 is not worried about backward protection, because Mars 2020 is not bringing the samples back. The follow-on missions have to deal with that. It is a big deal. And it is potentially a dealbreaker in terms of cost and complexity. But for forward protection, we were involved in a lot of the forward protection, and it's interesting to contemplate for a minute what the purpose of forward protection is. There are people who will naively believe it is an altruistic thing, like we should not contaminate other planets. That's not why Mars is considered to be protected, or why there is an international agreement that Mars is protected. It is to protect the science. It is to explore Mars free of terrestrial contamination so that if we find evidence of life, we can be reasonably sure it is Martian and not terrestrial contamination. But what was interesting about this during the development is there's an independent—or at the time, there was—an independent organization responsible for ensuring that Perseverance would not contaminate Mars. They're part of NASA, but they had veto authority on many different things that we were trying to do. Some of what they were demanding that Perseverance do, we could not do—we could not successfully do the mission—and this created a lot of infighting at NASA, between the development team at JPL and the group that was responsible for protecting Mars. In many ways, the planetary protection scheme that was being developed was not modern, in that—of course one of the amazing discoveries of the last few decades is how much life there is that cannot be cultured. All of this work that is done with meta-genomics, where you take a little droplet of sea water and discover that there's 50 billion different organisms living in there, most of which are not culture-able—well, NASA was still working under a very old-school view of life, and they were making requirements based on that. In any case, that was very much an anxiety-producing situation, where the Planetary Protection Office would make statements like, "You must do this," and the JPL engineering side would say, "Can't do that." As an example, they wanted us to bake the rover, the entire rover, at temperatures beyond the melting point of plastic, and there is a huge amount of polymer materials on the rover. We just had to find a way around that. Eventually, a compromise was reached, but [laughs] it was a pretty stressful part of the activity.

ZIERLER: I can't help but ask, the Ridley Scott film in 2015, The Martian, with Matt Damon and Jessica Chastain visiting JPL and all of the media attention. Were you involved in any of that, from a PR perspective, from a science advising perspective?

FARLEY: No. That movie made a big impression on a lot of people, and it set expectations I think in some ways that we are having to roll back.

ZIERLER: Oh, yeah. I mean, it makes it look like it's totally feasible to go and work on Mars.

FARLEY: Or that you can rove for 1,000 kilometers. No. At least in the present day, we cannot rove for 1,000 kilometers. The other one, which we hear about a lot today, is those scenes of the dust storm at the beginning, when the rocket falls over—yeah, Mars doesn't do that. There are very high wind velocities on Mars, but the atmospheric density is only 1% of Earth at sea level. So if you were in such a wind storm, you would barely notice it, because there's just no atmospheric pressure behind it. And it doesn't lift sand and bury things. As we're putting our samples down on the surface of Mars in this first cache, almost every time I give a public presentation on this, somebody says, "How can you be sure they aren't going to get buried?" They're thinking of that scene in The Martian where everything gets buried, so I've got to clarify that one for them. Undoubtedly, things like that are great for the public. This brings up the whole issue of what the relationship is between the robotic exploration of Mars and the potential for human exploration in the future. Obviously I think most people, when they think about this, they consider NASA going to Mars with human beings. That's a whole different level of operation than robotic exploration, but at least robotic exploration is setting the groundwork for how this can and should be done.

ZIERLER: On the point of some future potential for human exploration, what were some of the science objectives as they relate to terraforming, or oxygen production on Mars?

FARLEY: [laughs] Yeah, not terraforming. We are not terraforming. We have never talked about terraforming. But we have demonstrated technologies that could be of use for human exploration. The most obvious one is the MOXIE instrument, which has as its central objective, which has now been successfully achieved, to take in CO2 from the Martian atmosphere and convert it into oxygen. So, a "live off the land" kind of approach where on the surface of Mars, one can acquire large amounts of electricity from solar panels. If one had the feedstock to make something you need, then you should do that, so you save the mass of transporting it to Mars. The MOXIE instrument was a small-scale demonstration that you could take electricity and atmospheric CO2 and make oxygen. That was one element of it. There are two other things which are important features of Perseverance that are related to that. One is the weather station called MEDA. It is important, especially for landing materials on Mars, to understand what the atmospheric conditions are like. The landing is very much influenced by atmospheric conditions. Perseverance has a weather station that acquires such data that will be useful for developing models, that will ultimately I think someday be like weather models on Earth. Now, without having lots of data, they are more model and less data-based. The final thing is there is concern that the Martian dust is hazardous either to humans, possibly because of its very small grain size it could be problematic to inhale the dust, and possibly because it could be very sharp and may damage, for example, fabric of suits that people wear. So, one of the objectives of sample return is to bring some of this dust back to be characterized so that risk is understood better.

ZIERLER: When the Ingenuity helicopter program was announced, I know it was a surprise. It was not part of what you were planning for. Were there new science objectives, or did that change anything in your role as project scientist as a result of adding the helicopter to the package?

FARLEY: No. The Ingenuity helicopter was built as a technology demonstration, not a science instrument. It has no science requirements and has no real science capability. That's not what its function was. Its function was to simply demonstrate that controlled flight was possible.

ZIERLER: Is that basically like what Pathfinder did in 1997? Is it the same basic idea?

FARLEY: In terms of it being a technology demonstration?


FARLEY: Yeah. I think many people look at it in the same spirit, which is, "Wow, little Pathfinder led to lots of additional missions." I think Ingenuity has already demonstrated the same thing, since one of the major strategies for bringing the samples back could involve helicopters.

ZIERLER: Exactly on that point, if we could just engage in a thought experiment, how you go from Pathfinder to Perseverance and to sample return of what comes next. Demonstrating the proof of concept of helicopter flight on Mars, how might that be a game-changer for the kinds of science that can be done on Mars?

FARLEY: I am not wildly optimistic about helicopters. I am perhaps a curmudgeon in this area. Scientific instruments are heavy. They require manipulation of materials. It isn't clear to me that a helicopter can ever be made large enough to do that. The atmosphere is extremely thin. At least in the current manifestations of both Ingenuity and the follow-on helicopters, there is a ground element that is associated with it. In the Perseverance case, it's a rover. In the follow-on mission case, it's a lander. You still need to build the whole big infrastructure that goes with the helicopter. You don't just fly a helicopter to Mars and it does its thing by itself. It still needs the ground support. So it's not a panacea. I think in terms of what the future exploration of Mars entails, helicopters will play a role, for example by allowing, if they can acquire cameras that are of sufficient resolution and quality to provide images that are comparable to what we get with the instruments on the rover, they will be able to survey large areas in places that you simply cannot go with a rover, and that's spectacular. That's important. But if you want science instruments, I think you are still going to have to interact more closely with the surface than at least any helicopter I've ever heard of is going to be capable of doing.

ZIERLER: Are there elements to the Martian atmosphere that are sufficiently interesting, and the capabilities of a rover are by definition too limited to get at what's going on x number of feet or meters above the surface, for which a helicopter could be useful?

FARLEY: I don't think so, because the atmosphere is well mixed. There are good questions that you would want to know the answer to, like what is the concentration of methane in the Martian atmosphere. It is a very controversial topic, with different answers coming from different investigations, done in different places. So, there are things you may wish to do, but I think the right way to handle that is to get an instrument on the surface that can analyze in a way that everybody is confident is getting the right answer. The data that are being acquired are mutually inconsistent, and part of it is because people are unsure what the instruments are actually measuring.

ZIERLER: The development of Europa Clipper, the Clipper mission, was that useful, to just watch this thing develop, in parallel?

FARLEY: [laughs] My head was so down in the weeds on Perseverance that I did not pay any attention. I continue to pay almost no attention to Clipper. I was a PI on an instrument proposal for Clipper, for which I am very glad [laughs] I was not successful. That would have been way too much. Clipper is still in the development stage at this point, so it has a much longer time horizon than Perseverance had. I'm definitely glad to be living the dream of doing the science mission now, and not still being on the ground waiting to launch, and then do ten years of cruise to get to the destination.

ZIERLER: Do you have a memory of when the term "Mars 2020" came into common use? Is that just words, or does that actually change what otherwise would be known as the Perseverance mission or the Perseverance/Ingenuity mission? What is the relevance of Mars 2020?

FARLEY: On day one, that was the name. I think this was a not very subtle warning from NASA headquarters, "Thou shalt launch in 2020. Come hell or high water, you're going to launch in 2020." We took that seriously. A failure to make the every-26-month launch window is a very expensive and embarrassing outcome that Curiosity went through. This was the warning from headquarters—"Here's the name for your mission, JPL. You go and build this thing. And by the way, the name tells you when you need to launch." [laughs]

ZIERLER: The obvious follow-on question—it's February 2021. What is the chronology, and what is your role in reorienting NASA's expectations that it might be called "2020," but that ain't happening in 2020?

FARLEY: Well, it did happen in 2020, right? We launched in 2020. Is that what you mean?

ZIERLER: Oh, I'm thinking of—oh, yeah, no, no, no. It did happen.

FARLEY: We made it. We made it. And it is a whole miraculous thing that we made it, with the pandemic coming down on us, but we made it. It actually shows you where the focus is. The focus is on, "Just get it off the ground." This sounds more negative than it is meant to be, but really, the bleeding stops when you light the rocket, meaning the financial bleed. Honestly, it has to be that way. NASA headquarters' central role is to feed money to projects and get them so that they can do their thing. As soon as you have left Earth, there is no going back. You cannot spend any more time developing. It's over. The reality is, most of the money gets spent in the development phase, so clearly they were more interested in the launch date than in the landing date and anything that might happen after we land. That's how that name came on.

ZIERLER: That's a really important point. Because I was thinking in terms of February 2021, the landing, but really, as far as NASA is concerned, it's really "Get it off the ground in 2020."

FARLEY: In the summer of 2020, yep.

ZIERLER: Tell me about the months leading up to launch. July 2020—what kept you up at night?

FARLEY: A lot of things, a lot of challenges came together at that point, not the least of which was the pandemic in the spring of 2020. But starting in the fall of 2019, we started to discover problems with the sample tubes. The parts had already started being flown to Florida for the launch. The last thing that we were going to send was the sample tubes. The team was having trouble manipulating the sample tubes through the robotic system that handles it, called the Sampling and Caching System, and they were having trouble making the seals seal. The tubes have a seal in them that is a hermetic seal, and that's very important to not let gases out of the sample tube. I would say this was bordering on a crisis, because this is the kind of thing that you could have to slip the launch for, if we were unable to make the robotic system work. The stress level was rising very quickly. The thing to understand about a problem like this is, you do not have time to completely re-engineer everything. You have got to make do with what you have, if you're not to slip. You also don't have time to get root cause of whatever your problems are. You need a good enough understanding of the system to let you move forward. This did two things. the first thing it did is, the engineering team decided that one of the things that was causing problems was baking the sample tubes to high temperatures. Originally, we were planning to take the sample tubes up to 350 degrees C, in air, to burn off any organic matter and any microbes that might be on it. This is the gold standard for how you clean something; you fire it. Engineers did not want to fire it, for fear that it was doing something that was making it hard to seal the tubes. So very late in the game, we had to adopt a completely different cleaning protocol, and I'll return to that.

The solution to the sealing problem was interesting. We had a whole pile of sample tubes, and a whole pile of seals, the little plugs that go in the tubes, and they literally found, by trial and error, this seal fits in this tube [laughs], and it doesn't fit in this other one. It's understood why that is, so it isn't quite so random, but we actually then had a mapping, and we only took the tubes and seals that mated. That was not too painful a solution. But the cleaning got pushed into the pandemic period. So, during the spring of 2020, what I call a really heroic group of people at JPL—I was not among them—were tasked with cleaning these tubes, using very hazardous solvents. Rather than firing, we decided that we would clean with hexane. Hexane is extremely flammable, it is not something you ordinarily want to work with, and it has to be done under ultra-clean conditions. And it has to be done during the pandemic. It was very challenging. Then at the same time, we had to prove that they were clean enough. We would not launch if they were not clean enough. We had a requirement that they be clean. There was a group of analytical chemists at JPL who were tasked with analyzing those. That was by far the worst several months of the mission, is getting through that. It caused a lot of infighting of how we were going to do it. Ultimately, we met the requirements. I think we met the requirements pretty easily. It was a mad dash to get it done, and get those things sent to Florida, and literally installed into the rover just before the rover got placed on the rocket. We just barely made it.

ZIERLER: When COVID hit and nobody knew what this would mean, the extreme disruption, there's only so much that you can do remotely, were you concerned on an existential level, for the mission?

FARLEY: It seemed pretty iffy that we would make the launch. At that point, everything was going well, so I think the worst case is we would have slipped. The Europeans were building a rover on the same timeframe, and they did ultimately slip. They were unable to keep up their program at the level that was necessary. We managed to keep it going and make the launch, but I have no doubt, if the pandemic had come six months earlier, we would have not made it. We were close enough that by putting in a big effort, we could get over the hump and get to the launchpad. But the closing year of mission development I think inevitably is a mad scramble. Fortunately for us it was only the last six months of the year when the pandemic was happening, so the first six months of the year we could be scrambling full-bore.

ZIERLER: An overall question about these seven years in planning for Perseverance, for the launch—is the concept of Mars Sample Return sufficiently dynamic that it's influencing the science objectives of Perseverance? Or is it still too pie-in-the-sky, and Perseverance is going to do what it's going to do, and figuring out Mars Sample Return is sequential, but it's really too far out in the distance to affect the tactical, day to day of Perseverance planning?

FARLEY: That's a really interesting question, because until about 2018 or even 2019, we were working under the assumption that the follow-on missions, if they happened at all, were somewhere in the distant future, and there was going to be no interaction. We had been given our marching orders, "Collect the samples. Set them on the ground. Set them on the ground, because otherwise you've got to get them out of the rover. You don't want to do that, so set them on the ground." We had developed our whole plan around that notion. Then, it became clear that NASA and ESA were jointly interested in expediting the process. For some technical reasons, if they don't launch by 2028, you've got to wait another decade or so. So the plan that NASA and ESA adopted was to launch in either 2026 or 2028, and they now know they're going to launch in 2028, plus or minus a little. What that did is it suddenly completely changed the landscape, because for a landing around 2030, Perseverance could still be functional, and a functional rover is worth a lot to minimize the risk of the follow-on missions, and to make their job easier. As it has come to pass, Perseverance is the primary plan for getting the samples to the lander. The long-range plan is that Perseverance will last until 2030, and in 2030, Perseverance will literally hand off the samples to a fixed lander that has the rocket on it. What that suddenly does is it says that the success of MSR depends on the long-term survival of Perseverance. That's a big challenge. The rover was not designed with that in mind. It may well last that long, but it was only tested—the definition that we were working under had three Earth years, so we had to basically—the engineers at JPL had to guarantee that the rover would last three Earth years. That's not the same as lasting until 2030. It's almost two and a half times longer. That's one element of it.

The other element is more practical and much more involved me, and the role that I have. It was one thing to say, "Yeah, someday these samples will be picked up." It was easy for people to say, "Yeah, let's not pay that much attention to it, because someday maybe it will happen." Which is not something I ever shared; it was always dear to my heart to get the best samples we possibly could. But suddenly when it's clear that NASA and ESA are focused on this, they are making it a top priority, and big money is being spent, every day we are working on Mars we are thinking about getting the best samples we can, because we can see our colleagues at JPL and elsewhere, building the thing. That's both a little frightening—like, if we don't succeed in getting them good samples, then that whole operation, even if it is technically successful, is not scientifically successful. It's intimidating at that level. But it's also gratifying, because we have collected samples, and we have recently gotten the first level of endorsement from the science community—"Your samples are worth bringing back." It's a nice feedback, that we're getting approval of that, but it is a completely unexpected to me turn of events. I had thought during much of the development phase that I may well not live long enough to see the samples come back. Now, it seems at least, if all goes well for me and for Perseverance, and for the follow-on missions, I will live to see them come back. Which would be really interesting to see.

ZIERLER: In light of the longevity of Curiosity, talking about Perseverance lasting for three years, both in terms of the expectations—not just minimal expectations, but really if Curiosity has been healthy for this long, why not Perseverance as well—what are the expectations from a planning perspective on what Perseverance can do, if it lasts until the 2030s? What does that mean in terms of planning the science for Perseverance?

FARLEY: When we selected the landing site—and by we, I mean the science community; it wasn't me personally—the science community, broadly defined, had this series of workshops, and identified two different types of geology that were both close together at Jezero Crater. The Perseverance science team proposed, "Let's marry these together. Let's do part of the mission in Jezero Crater, and part of the mission in the highlands around it." That would really satisfy both camps that were advocating at the workshop. So we knew, right from the beginning, that our plan was to do what we were initially calling kind of facetiously "the mega mission." I'm careful not to use that name, because that sounds overly ambitious, but what we are doing is an extremely ambitious thing, in that we are planning, we have a route laid out, we have science targets laid out, for a 50-kilometer traverse. We knew from the get-go that we were going to need to move quickly to make it up to where now we are planning to meet the follow-on missions. So everybody is now sort of signed up to this very ambitious plan. But we always knew, even before we knew that MSR was coming—once we selected the landing site, we knew that we were going to do this ambitious plan.

ZIERLER: Tell me about launch day. Where were you? What was it like?

FARLEY: Launch day. I was in Florida. That was a very strange experience, because I also went to Florida for the Curiosity launch. There were people everywhere for the Curiosity launch, and I, like many others on the Curiosity team, sat on bleachers. There were probably a thousand people in the bleachers that I was on, and you could see other bleachers in other places around the launch site where people were sitting. Anyway, it was super—people come to see the launch. For the Perseverance launch, in the pandemic, there was nobody. It was super strange. Kennedy did not allow any just standard visitors to come. You had to have special reason to be there. I was fortunate enough to be able to go to the launch and participate in what they called the VIP briefing, which was in a much better place than the bleachers. It was actually in a building that was like a five-story building with a view out to the launch pad, at relatively close range. I gave a literally 30-second scientific presentation to a bunch of politicians and other NASA center directors and stuff like that. The launch was spectacular in the sense that we just barely finished that presentation, partly because the politicians were allowed to speak, and you know, they don't know how to, like, keep it short. I was looking at the clock thinking, "We've got to wrap this up, because we've got to get outside to see the launch." We made it outside, and we were standing outside for, I don't know, it couldn't have been five minutes, when the launch window opened—PSHHH, they launched the rocket. It was amazing to get it off in the first few seconds of the launch window.

What anybody will tell you about the launch is the disconnect—you're quite a long ways away, literally miles away from the rocket, because it's not safe to be any closer, and you can see the fire coming out of the back of the rocket, and you can see the rocket move, but you can't hear anything. The rocket is already well in flight before the sound arrives, and the sound practically knocks you over. Even at multiple miles range, the sound practically knocks you over. That was spectacular. It was a great thing. It felt to me like, "Oh, we made the launch. Great." But everybody talks about how you're not out of the woods until you go through the final set of steps and leave orbit. The first step is to get into orbit, and then you get on the trajectory to Mars. There was an anomaly that turned out to be an absolute nothing, but we lost contact with the spacecraft relatively early in this process. Within the first, I don't know, six hours, we lost contact. Of course I had no idea what was going on other than everybody saying, "Oh, we've lost contact." I'm thinking, "Wow, this could be over." Long story short, it was just there was something that was set up incorrectly, and they were able to fix it quickly. But it was a moment of, "Oh, crap."

ZIERLER: [laughs] As project scientist during the transit phase, what is your interface? What are your responsibilities during this period?

FARLEY: At that point, it was clear that a mission was very likely to happen—we made it to launch—and very likely to happen soon. So, the goal was to do team training, to get the team ready. We had about six months to get the team fully prepared for all the complexity that is involved in operating the mission. We were working fast and furious on that. Of course, for many of us, the whole way a rover mission operates is very foreign. It takes a completely different mindset of working on a very peculiar cadence, and at least initially, working on Mars time. Team training was the goal.

ZIERLER: What was landing like?

FARLEY: I thought that landing was going to be stressful, and I somehow got into the, "This is going to be fine." And, it was. It was fine. It was more than fine. I was not nervous about it. I thought I would be, but I wasn't. Then, of course the really spectacular thing, which was also the result on Curiosity—to go through the experience of knowing that by the time you were hearing anything about doing atmospheric entry, the spacecraft has either landed or not landed. It's over. There's nothing you can do. I always like to point out to people, when you see the movies of the people in the JPL facility, they're not controlling anything. They're just listening. They're passive. There is nothing they can do to fix whatever is going on. It has either worked, or not worked by the time the signals are coming in. That's a little bit of a weird experience and forces you to have kind of a Zen—since absolutely, by definition, I cannot do anything, you just get into that. At least I got into that sort of acceptance mode. But then for me, the really amazing result is the first images. That's when you say, "We have a mission. Not only did we land, but the instruments turned on, and there's the first picture." There's a picture of some sand, and a rock. Like, "Yeah!" That was great.

ZIERLER: What's the time progression? You have landing, and then when do the first images come through? How long after?

FARLEY: Minutes. Minutes. Yeah. The other really exciting experience about this—that was a great success. Then we localized where we were, and there was a little bit of, "Huh! Not where we thought we were going to be." We landed well away from where we thought we would. In a fine place, but that was a surprise. Hours later, while we were still receiving data from the spacecraft in its first day, there were a relatively small number of people in the operations facility when we first started getting the still images that ultimately made up the video of entry, descent, and landing. So we were standing around, and all of a sudden, people are just looking at the screen. All the engineers are just looking at the screen. Because the images that were coming back were clearly going to make a spectacular movie. There's a whole set of cameras during entry, descent, and landing, looking up at the parachute, looking down at the rover, looking up from the rover at the descent stage. The images were so spectacular. That was a great moment, to see that. For a very modest expense, the addition of those cameras was just a gigantic success, because it allowed you to actually experience what that was like, the whole winching the rover to the ground, and the dust flying up, and—it was great. To be there in the first few minutes when those were coming down was great.

ZIERLER: From that instantaneous gratification only minutes from landing to images, what about the science? When does the rover start doing science? When do you kick into high gear?

FARLEY: This was always a challenge of the mission, is the need to do commissioning. You've arrived on Mars, but you're not really ready to do anything. You've got to check out that everything works, and there is a very careful slow process to make that happen. To be honest, it's quite a frustrating process to be on the science side, waiting. Bit by bit, piece by piece, capability by capability, we slowly took over the rover. That commissioning phase lasted about three months. Then, as soon as we finished that, we did the Ingenuity technology demonstration flights. So, science was in the background for a good four or five months, at the early part of the mission. We weren't doing nothing; we were taking really great images. But in terms of being able to decide, "Today the rover is going to do this," we were not able to do that until about four and a half months into the mission.

ZIERLER: If you can compare—you're in the middle of it now, so you really can't take a retrospective view—but the seven and eight years as project scientist before landing, and now, almost two years since landing, how do you compare the day to day, the stress levels, how much you need to be at JPL? What is it like? What is the life of the project scientist pre-launch versus post-landing?

FARLEY: We definitely moved to a completely distributed model. That was always the plan. I spend only part of one day a week at JPL to interact with the engineering side. We always knew that we would be distributed, but of course the pandemic came along and made that look like a very wise choice. As a practical matter, I spend much more of my time sitting in front of a screen than I was before, where I would go in and talk with the engineers every day in person. That's a big change. The other big change is the nature of the role. I spend much of my time trying to keep the rover doing science, and doing science that best meets the science objectives. As you might well imagine, if we have 500 science team members, we have 500 different ideas of what the rover should be doing. The central goal of the project scientist and the associated people—my deputies, and the people that work with me—is to keep us doing the highest priority tasks, those tasks which best align with the mission's goals, and with this long-range plan of the mission. Some of that is getting the science team to focus on the key objectives, not just anything and everything. There are many different things that we could do, and we cannot do them all. There has to be triage.

On the engineering side, we have this different goal than any other Mars mission, maybe any other mission, period, has ever had; we have a place to be, in the very distant future, with a thing to have completed—collected all the samples. We know where we have to be, and we know what we have to have done by then. Mission success requires that. So, we need to keep moving. In many ways, the engineering side, their central goal—they will say their bottom line—"Keep the rover safe." Now, they know we need to meet the science objectives—they're not negative about that—but when there is an issue that puts the rover at risk, they will want to slow down. Sometimes, the risk aversion is too great, in my opinion, so I have to spend my time arguing for why what they call an epsilon risk—an epsilon risk is an extremely tiny risk—and that we should take that risk, because it will save us a lot of time. There's a fair bit of that, that goes on. My role is much more day to day making sure that works, and especially my deputy, she is in the trenches every day watching how all of that is going. It is a very complex piece of human machinery, the way all the scientists and all the engineers come together, every day, to do this thing, and optimize. It would be easy to not optimize—you could just let it happen—but the optimization is the central role that we play.

ZIERLER: I asked you to compare those eight years versus the previous two in your role—the intensiveness being at JPL as project scientist. What about your bandwidth, your responsibilities, maybe even your expectations as Caltech professor? Have those changed at all in the past two years, now that Perseverance is doing its thing?

FARLEY: Yeah, I stepped back from teaching altogether in 2019. I'll teach a seminar class or something like that, but I have stepped back from that. Kept my research going, as I've talked about. That has not been a huge impact. But I have definitely felt removed from my community, the community that I had been associated with for decades before that. I think everybody feels a little bit of that, or maybe a lot of that, from the pandemic, but for me it's sort of a double-edged thing. I got the pandemic remoteness, and I've got my daily life is remote, working with the science team and with the engineers.

ZIERLER: You were teaching up until 2019?


ZIERLER: What changed in 2019? Is that just because it's so intense before launch in those two years?

FARLEY: Yeah. Effectively, I have a research grant to do the project scientist job that is paying a large fraction of my salary. As I indicated a minute ago, there are things that I have to do at certain times, and I can't control that. I can't say, "Nope, I can't do it at 2:00 tomorrow. You all have to reschedule around me." It doesn't work that way. You have to be there. That doesn't really work very well with teaching, because sometimes those commitments will appear on short notice, and you don't want to have to tell your class, "Hey, sorry, we can't have class tomorrow because I have to go to this meeting." So I stepped back from that, and at least for now, that is the current state of affairs of my involvement with teaching.

ZIERLER: Is that hard for you? Do you like teaching? Do you miss that aspect?

FARLEY: I'll be honest and say that I think my strengths are not in—I think I'm an okay teacher; it isn't what I have a lot of passion for. So I have not missed it. I probably could do it, and trade off something else. I could trade off some of my research time. But that's just not what I feel like I am best at. I like working with small groups of students, I like working individually with students, and I like working on the bigger kinds of things like being division chair or being project scientist. In terms of classroom teaching, that's just not my passion.

ZIERLER: What about your own research separate from JPL, separate from Mars? How has that been affected one way or another in the post-landing phase, these past two years? Have you been able to get more done? Are we going to see you as lead author on publications start to tick up again?

FARLEY: I have always kept research that I myself was leading—analyzing samples myself, writing papers, even sole author papers where I was the only one involved in it. I've had to let a lot of that go, until literally the last few months. Now I've gotten back into it. It's pretty fun to dig up some old data and try to make progress on it. In some ways it was good to step back from a set of problems where I just wasn't making progress anymore, step away from it, and come back and look at it with fresh eyes and realize, "Oh, yeah. I missed that. Here's the key. It was sitting here in front of me all the time." I'm enjoying getting back into that, and I think I will be able to continue to do that. I'm not sure what my long-range plan is at multiple years, but at least for now, I think I can keep both of these going at a reasonable level and still drive some of my own scientific interests in terrestrial studies.

ZIERLER: That's to say obviously you've kept up with the literature in the areas that are most important to you.

FARLEY: You hit on a good point. I think it is inevitable that people in my career stage—it is hard to keep up, even if you are plugged in 100%. There are certain things in which I have a very well-developed niche that I pay very close attention to what people are doing, and then a broad area of things that I wish I was better connected into. But this is what you have students and postdocs for. They can dig in and say, "Hey, you need to read this paper. This is really important," and tell me which way the wind is blowing on different scientific topics.

ZIERLER: On the niche that's really most important to you, that you have stayed on top of, what is that? What do you prioritize for the precious time that you have?

FARLEY: Helium in rocks. [laughs] That's my thing, helium in rocks!

ZIERLER: Back to the basics.

FARLEY: Yes, I could show you all of my notes of helium in rocks that I was working on earlier this morning! [laughs]

ZIERLER: Let's bring it right up to the present, then, Ken. What is going on in the field right now? What's your involvement?

FARLEY: The thing that I am most interested in personally right now is just asking the basic question, "How is it possible that helium remains in rocks?" It clearly does, and it tells us a lot of information about a whole bunch of different things that we talked about before. But one of the things that has become obvious to me is that it's really hard to understand why the helium is still in these rocks. This is made obvious, for example, when people do molecular dynamics simulations, and they show that helium should diffuse out very quickly. I'm trying to understand why this is. I think it actually says something pretty basic about the way helium interacts with solid matter. I found some inspiration for this in a completely unexpected place—that the industry that works with nuclear reactors has a problem that they get helium in their containment structure, and in their fuel rods, that destroys them. This is because neutron irradiation transmutes some elements into helium, and it turns out they know very well what's going on. The helium doesn't get out. It doesn't get out because it forms little bubbles. I'm actually thinking that this is the key to understanding this question, so I'm working on some both experimental studies and some modeling to try to understand that. The thing I like about that is it draws together a lot of the things that I work on, helium in rocks, just getting at the mechanistic reason why it all works.

ZIERLER: Do you see this purely in a basic science context, or is the nuclear industry going to be interested in this? Is there some consulting work that might happen?

FARLEY: I have thought about that. There's an interesting renaissance that is happening both with nuclear power and potentially with fusion reactors. Although it is definitely true that fusion reactors are cleaner in some view, they are actually much worse for this helium embrittlement problem. I have actually been thinking about, yeah, maybe I'm going to learn something here that is of value to this problem. Right now, that industry has a huge amount of money to invest in this otherwise piece of minutiae, which is the behavior of helium in materials [laughs], and so they have lots of data. It's on substances that are very different than I care about. A metal is a fundamentally different kind of material than a mineral, which is under most cases an ionic solid. They do behave differently, but I'm trying to find the connections between them.

ZIERLER: The helium issue that you have identified with fusion energy—the media reports right now are breathless, of course. This is going to solve all of our problems. Is there a bigger challenge here from a geochemistry perspective that is not getting reported?

FARLEY: Well, there is, and this is probably not what you mean, but in the long run, I think the accepted wisdom is that fusion will require helium-3 as a starting feedstock. The question is, where are we going to get helium-3? There are people who say we need to go to the Moon to mine it. I'm not sure whether you've heard this, but this is one of the stated reasons for building a base on the Moon—to mine helium-3 that is on the Moon. I'm actually quite interested in assessing whether this retention of helium in minerals, whether there are opportunities to not have to go to the Moon, which is of course an extraordinarily expensive way to do anything. If you have to go to the Moon for it, it's going to cost you a ton! [laughs] Can you do it with terrestrial materials? This is the area that I would say is my niche.

ZIERLER: Is the Moon so abundant in helium-3 that that's not even a fantastical idea, just from a resource perspective?

FARLEY: It's fantastical from the point of view of what the infrastructure would look like to bring it back, but it is a gigantic resource. In much the same way that people will say, "We should mine an asteroid for platinum group metals"—you could do it, but boy, when you look at the cost—if a launch costs $400 million, which is the number that I hear for launching Perseverance, if that's how much it costs, yeah, you've got to really want it. If you spent $400 million looking around on Earth, could you find what you're looking for? I think the answer is possibly yes. So I've gotten interested in that aspect of it, also.

ZIERLER: What is it about the geochemistry of the Moon? Why is helium-3 so abundant and so easily accessible once you get there, that might not be the case on Earth?

FARLEY: This is just the same reason why the cosmic dust grains have helium in them. Ions are streaming out of the sun, and they're bombarding the surface of the Moon, and there are some minerals, that for reasons that are not obvious, that are part of what I'm looking at now, they very strongly retain that helium. The mineral that is on the Moon that people are focused on is a mineral called ilmenite. My guess is it is forming little helium bubbles.

ZIERLER: Now that we've worked right up to what your current interests are and where things might be going in the future, for the last part of our talk I want to ask some retrospective question, and then we'll end looking to the future. First, I don't know if you saw—it just came out yesterday—the cover story for Nature is about how science has become less disruptive in the 21st century. It's a meta-analysis of scientific papers over the past 20-plus years. The basic conclusion are trend-lines, that science has become less disruptive and more incremental. It's based on this meta-analysis of all scientific papers. I'm not sure if you've had a chance to look at this yet. It's making a lot of waves. In your own experience, does that sound right to you? That science, however we might define it, has become less disruptive?

FARLEY: No. I guess I'd have to see how you define the whole thing, but sure, we can look in the distant past, and we can say, "Oh, yeah, the whole issue of the quantum nature of matter, obviously that was huge." Plate tectonics. Huge paradigm shifters. The completion of LIGO, that was huge. The discovery of gravity waves and where they're coming from, that's huge. The discovery of extrasolar planets, huge. So, I'm not sure how you would say that, other than inevitably if the scientific enterprise grows—and it has been; the scientific enterprise is enormous—it's an interesting question to ask whether a smaller scientific community would still make those big discoveries, and I think the answer is probably yes. That by adding more and more scientists, you get more and more incremental science; maybe that's an unpopular statement to make, but I think it is inevitably true, that the bigger the enterprise is, the more people who are doing incremental science are brought into doing it. So I don't believe the general statement, and I also think it is a very dangerous thing to assert, because it sort of implies the end of science, and I just think that there are discoveries—when there's a breakout discovery, you don't know. You don't know when it's going to appear. To imply that, "Oh, yeah, we're done with everything," feels to me like you might just miss the whole future.

ZIERLER: The spirit of ambition that made the discovery of gravitational waves, for example, is that still there? Is that one of the reasons why you have cause for optimism, just on the interpersonal level, the things that scientists are reaching for?

FARLEY: I think so. I think it's still there. The people that I interact with, they're all trying to do great things. They're not doing incremental things. Or at least if they are doing incremental things, they are with a purpose. "If we can get through this incremental set of—if we can understand this a little bit better, it's going to allow something." It isn't polishing a cannonball, getting a little bit better. At least the people I associate with, that is not what they are trying to do. Of course, it's hard. It's hard to make a fundamental discovery of importance. Because anything that was easy would have already been done. That doesn't mean that we should lower our standards or expectations of it.

ZIERLER: This is great to hear, because as you can imagine, there's a lot of hand-wringing going on over this article right now, so I'm glad there's some pushback.

FARLEY: Yeah, I'll have to read it. There are interesting questions about what's the right size of the scientific enterprise, and I don't feel like I have any special insight into that. But working at a place like Caltech, you've got a large collection of very ambitious, spectacular scientists and engineers. I'm going to see a different part of it, perhaps, then the entire community as a whole would see.

ZIERLER: Finally on to our retrospective questions. Pre-JPL, pre-Mars exploration, what do you see as your most significant contributions in geochemistry?

FARLEY: I would say the two things that I feel like my group has identified that are important and will remain so are the development of geochronology based on the ingrowth of helium. That's a relatively large field. For geoscience, it's a large field, and the early work that we did is all foundational for that, both from an interpretational point of view and from a methodological point of view. The other, which much more came out of left field, is this ability to identify cosmic dust in sea floor sediments to learn about a whole variety of different things, including major events in the history of the solar system, like periods of enormously enhanced cometary activity. It's still the only game in town for that. Those are really the areas where when I look at it, I think, "We made an important contribution here."

ZIERLER: Given the size of the geochronology field, how it has grown in relative terms, what has been surprising as the field has grown and it has not all been as a result of what you've done? How have people taken this in areas that you might not have anticipated early on?

FARLEY: I have to say that the thing that has probably surprised me the most is there are a relatively small number of people who really enjoy figuring out the details of either an analytical method—like, "Okay, how can we do this?" and then goofin' around in the lab to make it happen. I love doing that. That's what I really love. There are relatively few people that do that, and there are relatively few people who want to find new ways of doing things, or discovering new things together by just saying, "Huh. I wonder what would happen if we analyzed this, this way?" I have been fortunate enough to have a lab that can do that, and to have students who enjoy doing that. Much of what we do will be analyzing something, and then scratching our heads, like, "What does this mean? Is it important?" I don't see a lot of that. Maybe this plays to what you were talking about a minute ago. In terms of the ability to develop capabilities in the lab and enjoying doing that, I think maybe that is an experience that I alluded to before, where the ability to make things, or to write code that does things, I think a lot of that has atrophied, and maybe it has reached—the generation of people who built stuff when they were kids, like built little radios and stuff like that, that's probably my generation, and it is passing. You can't buy a lot of these things. In the financial climate we live in, you can no longer have somebody on staff that can build. In the early days when I was at Caltech, we had a guy that could build stuff. That's what he did. You'd go and say, "Hey, can you build this thing?" "Sure!" He'd come back three weeks later with the thing. We're losing that sort of ability.

ZIERLER: What are some of the big unanswered questions in the cosmic dust research? Where does the field go from here?

FARLEY: I would say the thing I am most interested in is that there has been a real change in our understanding of the early history of the solar system. We used to think that comets would look like extremely primitive things that condensed in the outer reaches of the solar system, because that's where they're found now. We have found evidence that I think is very compelling that there were several periods of enhanced cometary activity because a star passed close to the solar system and released the comets. Other people have argued against that, because the chemistry of those objects does not look like this view that the outer reaches of the solar system are super primitive. Well, there is a new understanding that has come on in about the last ten years that the formation of the giant planets in the early period, within the first few million years of the formation of the solar system, actually flung lots of objects from the inner solar system to the outer solar system, such that they are not super-primitive things. I think there is going to be some interaction there, where we are potentially learning about what comets are actually made of, by looking at these periods of enhanced dust flux, because that dust is bits of comet. I'm hoping we can bring that together. Right now it's a pretty controversial area, but it involves a lot of nitty-gritty geochemistry, and using the helium-3 really as a tool to find bits of ancient cosmic dust that could have originated from a comet, before we actually get return of material from comets. We have material that was captured from a comet, but that's not an Oort Cloud comet, it's not a comet that came from way far out, and the total amount of mass that was acquired by—this is from Stardust—the total amount of mass acquired by Stardust is micrograms. [laughs] It didn't acquire a lot of material. I'm keen on how all of that is going to go, and I'm interested in working with some of my colleagues that know about that, on the planetary side, people like Konstantin.

ZIERLER: I wonder how different a proposition it is for me to ask you to reflect on your contributions as they relate to all of your work at JPL. In other words, in thinking about your contributions in geochemistry, it's fairly straightforward to look at where you've made an impact in the field, where your group has been working at a foundational level, whereas at JPL, so much of what you do is enabling future generations of discovery which might not be so apparent in the here and now. On that basis, what do you see as your scientific contributions? What science has already been done as a result of all of your JPL work? And where are you forced to take a longer-term perspective that "The real science is going to happen x number of years beyond when I'm active in the field"? How do you think about those things?

FARLEY: That's a fair question. For Curiosity, the ability to have dated a rock, or the successful dating of a rock, it's an important milestone that I think is a contribution, that people will take note of, and have taken note of. For Perseverance, much of what I have done so far is synthesizing what other people have been doing on the mission. That's the role I play. But I think the thing that motivates me, and that I hope I have been successful, is keep the focus on those samples. Getting the best samples, keeping the science team going, and not spending too much time worrying about something that ultimately is not that important. There's a funny thing that I deal with in my head all the time. You can come up with a range of different numbers, but I estimate that the rover costs a million dollars a day. That is a huge responsibility. You could walk around the Caltech campus and ask people, "What is the cost of your research compared to a million dollars a day?" and it is always much, much, much less than that. So we are spending a lot of money to do this. If for no other reason, my goal is to keep everybody focused on the right things, and the engineers finding the right balance between risk and reward, with the goal of getting the best possible suite of samples back.

To be honest, I think this is a role that I feel like I am in a good position to play, because I don't need any scientific publications right now. I don't need to spend a lot of time establishing my track record. I think I've already done that. So I can focus on the thing that feels like, this is the biggest contribution I can make, is when all is said and done, MSR is likely to be somewhere between eight and ten billion dollars, including Perseverance and the storage of the samples, and there are not many places where I as an individual, or any individual, can play such a major role in ensuring the success of that project. That's really what 30 years from now I am hoping that people say, "Hey, they did a good job keeping Perseverance focused on getting the good samples, because look at these samples that we got!" They may never understand the challenges that were involved in doing that, that the natural state of affairs is to slow down and not push things. Whether it's the science team to keep moving, or the engineers to keep moving, they may not understand that, and that's okay, but if they just look at the samples and say, "Wow, this was a success," that's my major goal.

ZIERLER: To go back to that word "enabling," you're focused on enabling future science. That's the perspective that's most important right now.

FARLEY: Right. We worry not only about the kind of efficiency that I talked about, but as a geochemist, I'm very interested in, "Oh, we should get the geochemistry data on this rock that we're collecting." But the reality is that that rock comes back; anything that we learn with the rover is going to be superseded by anything we get with terrestrial laboratories. So I find myself in the peculiar position of saying, "Okay, we've got enough geochemistry. We have to answer the questions that can only be answered when you're on Mars." Some of them are just alarmingly simple in concept but hard to do. As an example, it is a general rule that a rock that is above another rock is younger. It has to be. That's the principle of superposition. If you brought back samples of each of those rocks, there's no way you could figure out what their relative age is, if you didn't do it by taking the right picture. So, much of what I keep asking the team is, "Have we gotten all of the data that you cannot get when you bring it back to all the fancy labs on Earth?" Which is not the geochemistry, it's not the stuff that I love; it's really field relationships that allow you to understand how the rocks relate to each other. That's kind of a weird aspect to it, that the thing I feel like I have to keep making sure we're not making a mistake is not the area I am most familiar with.

ZIERLER: Finally, to round out the discussion, some forward-looking questions. If we can think about, in rough terms, a ten-year plan. You're 60 now, most Caltech faculty retire at age 70.

FARLEY: I'm not quite 60!

ZIERLER: Oh, I thought you said you were 60. You're on your way to 60?

FARLEY: I'm pushing 60.

ZIERLER: You're pushing 60. So, roughly ten years, if you're comfortable stating your intentions, do you want to be project scientist for as long as Perseverance is viable?

FARLEY: I definitely want to stay in that role as long as it is useful and interesting to me. Useful to the overall effort, and interesting to me. I think anybody in my position would be looking at how to bring in the younger generation of people to take on the responsible jobs. I can see routes that would involve my being still closely involved but maybe not be a project scientist, taking care of some of things that I feel like I am in a good position to do, because, for example, I've established my career. I'm not trying to prove anything. So I can step into the background and do the things that need to get done, that I can do, without having to worry about whether I'm seen as the person who is the leader. I don't need to be project scientist, but I still feel like at this point, I'm adding value. I think that's maybe what most people would say, but that's the thought. I'm not going to be one of those people that stays a professor until I'm dead. As long as I live a long time, I don't think that's what is going to happen. I will retire at some point. And unlike some people, I suspect when I retire, if I'm going to retire, I'm going to be done. That's kind of a weird thing, because this is our lives. For many of us, being a scientist is what we do, and what we have done, for years and years and years, every minute of every day. So if I retired, but didn't step back from that, what does that mean to be retired? I don't know how that computes. If I'm going to retire, which I think I will, it will be to say, "Okay, ready to go do something completely different."

ZIERLER: In ten years, if Perseverance is still going strong, are you confident that there is still interesting science that it can do?

FARLEY: Oh, in ten years? Yeah. We'll be definitely pushing the limit on even the power source. Curiosity has lasted that long, but it is really starting to suffer from lack of energy from the nuclear power source. I'm not going to stay longer than ten years. I will not stay past handing off the samples to the follow-on missions, if I last that long. [laughs]

ZIERLER: In stepping back from the day to day, whatever that looks like, do you think before you retire, before you embrace something entirely new, is that specifically to allow more bandwidth for some of your geochemistry work, things that you might want to be involved with in a more intensive basis?

FARLEY: I haven't really thought about it at that level of detail. Right now, I'm just taking it as it comes, and there's still a lot of interesting things happening on both sides. The really fun thing about the way Perseverance works, and will continue to work, into the future, is we started out on the crater floor, totally different kind of rocks, and we got at the delta front. We found igneous rocks on the crater floor; we found what look like sediments deposited on the bottom of the lake in the delta front. Those are the two areas that we have explored in the first two years. In the next year, starting very soon, we'll start looking around on top of the delta, where we expect to find river deposits, so those are something new. Then we'll cross that area, and then we'll look at rocks on the crater rim, which will be totally different. So, there's always some new thing on the horizon that completely resets everything. Everything you thought you knew, yeah, erase that, because here's something different. That's a really fun element of it that will keep bringing me back.

ZIERLER: On the question of when to retire and doing something new, my understanding is a lot of professors are more than happy to retire at 70 precisely because no one is kicking them out. They can continue doing the science. Do you feel like the timing for you might be different, that you might want to stay an active faculty member for longer, if you are committed to that clean break whenever you feel it happens?

FARLEY: I don't really know. When I finished the division chair job, or was close to finishing, but before I accepted the project scientist job, I did think about doing something else altogether different, and in particular, getting involved in science policy. I think there's a lot of important things that scientists can do to help policymakers understand arguments that are complex, or even to cut through the crap that surrounds so many policy-relevant scientific issues. I feel like I am good at that. I feel like I am good at explaining scientific concepts, even if they aren't my field. You don't have to be an expert on climate change to be able to talk about climate change and cut through the crap that is flung out there. I feel like I could be good at that, and I think that's the kind of thing that I did consider in the 2013-ish time frame, like, "Maybe I should go and do that." Not because I was not interested in the science that I was doing, or that I thought that there was no more to be done, but just that seems like an interesting challenge. I still think that that is something that I would like to do, and I think a 70-year-old could easily do that, and then leave the big, exciting science things to the next set of generations that can work on it.

ZIERLER: Is there a science policy aspect that Caltech could or should be more involved in, if that's something for you to pursue from within a Caltech professorship?

FARLEY: That's an interesting question. Of course, there are limitations of what you can do, or should do, with the Caltech name attached to it. On the other hand, it immediately gives you credibility. It gives you a lot of credibility. I haven't really thought through that element of it, and it isn't clear to me that being emeritus wouldn't get you the same kind of cache in the scientific conversations that could follow.

ZIERLER: Finally, last question. If you'll indulge me, a scenario—they wheel you in, at the ripe old age of 90-something, when the Mars sample returns comes back. They've analyzed it, there's a press conference. What do you hope that press conference will be about? What do you fear that press conference would be about?

FARLEY: Well, the fear is easy. We think we are collecting ultra-clean samples. There's no reason to believe this, but it is possible that somebody we'll open those tubes and see that, "Oh my gosh, something has shed into all of those samples." For example, Curiosity has had a problem with Teflon coming out of a bushing on the drill and getting into the samples. I hope we don't have something like that. [laughs] That would be—embarrassing. I don't think that's likely. What I hope comes out of it—well, the thing that would really be spectacular is some kind of evidence that is incontrovertible evidence of an independent origination of life. That's just such a huge thing. I can't remember whether I said this before, but the thing that discovery of Martian life would really drive home for me is this idea that not only are all people basically one people, but all life on Earth is one life. We are one thing. And then there's another life, and that life is entirely different, and we should treasure our life, because this is all us, but there's other life. I think this is what's going to happen. If and when we find life somewhere else, I think one thing that should happen is we should all take a look at ourselves—and I mean human beings, and plants, and animals, and fungi—and recognize we are one special thing. We came from one unique event that's different than another unique event that created life somewhere else. Anyway, you got me on my philosophical thing. This is what I think is going to happen when we discover life elsewhere, and I would love it if opening those samples, we look at it and people say, "Oh my gosh, there is life, somewhere else, and it was very close by, all along. Right there on Mars, it was just right close by."

ZIERLER: In the way that there is a narrative sequence that gets us to Pathfinder to MSR, do you think the next mission after MSR will really need to wait for that confirmation of evidence of life on Mars before we can conceptualize what comes after sample return?

FARLEY: There are many scientific questions that people wish to address that don't relate to the life question. I think we have done the best that can be done looking at the ancient life question. There is no better place to go, or no better tool to use than Perseverance, to go and address that question. So, yes, at some level, if you want to go down that road, we need to see what we learn from that to go any further. But there are lots of other questions that could be pursued. And of course if the humans are in fact going, bringing along a suitcase full of science instruments is a nothing. If you have to get the people onto the surface and back, you have to build a very big thing, and so they can bring science instruments. That may well be the motivation in the future.

ZIERLER: We'll have to see. It's a big open question.


ZIERLER: This has been a terrific series of conversations. Thank you for spending all this time with me. It's phenomenal to capture this for the historical record. Thank you so much.

FARLEY: Yeah, this was fun!