Chris Webster, Planetary Scientist and Laser Spectroscopist

For Chris Webster, there is no clear delineation where his engineering ends and his science begins. As one of the world's foremost laser spectroscopists, he builds instruments according to the science objective of the project at hand, and in turn, the findings from those projects help to inform the next phase of technological innovation in new generations of instruments.

Educated in chemical physics the at University of Reading, Webster went on to complete a PhD in molecular spectroscopy at the University of Bristol. Over his long and storied career at JPL, which began in 1981, Webster has demonstrated the utility of tunable laser spectroscopy to the study of Earth's ozone; his laser capabilities have allowed for greater understanding of gas and isotope ratios in Earth's atmosphere; and his pioneering miniaturization of laser instruments for planetary exploration have revolutionized our study of methane concentration and the presence of isotopes on Mars, Venus, Ceres, Saturn and Titan.

A self-proclaimed science "maniac," Webster's voracious curiosity means that he will be working at almost every hour of the day, and the prospect of a sleepy retirement is anathema. Instead, Webster envisions his subsequent years in continuous pursuit of innovation and discovery, and most important, to enable the next generation of scientists and engineers to push ever further to new frontiers, both metaphorical and physical.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Thursday, August 24th, 2023. I'm delighted to be here with Dr. Christopher R. Webster. Chris, it's great to be with you. Thank you so much for joining me today.

CHRISTOPHER WEBSTER: Thank you.

ZIERLER: Chris, to start, would you please tell me your title and affiliation at JPL?

WEBSTER: I'm a Research Fellow at JPL, and I'm in the Science Division, Division 32. I'm on staff in the Science Division. That's my current title.

ZIERLER: There's just the Science Division? I assume that's pretty broadly conceived.

WEBSTER: It is pretty broad. It has the usual oceanography, earth science, Mars, planetary, astrophysics, so it's really the division that houses most scientists. I think it's maybe 300 scientists total. They tend to all be PI level, meaning they're all writing proposals for their own support and others, or they're the heads of a mission, like Earth or planetary mission PIs or instrument PIs, or leading laboratory or field work studies. They're usually leaders in a sense by definition.

ZIERLER: Now, being a research fellow, is that simply an honorific? Does that come with responsibilities or additional research support? What does that mean to be a fellow?

WEBSTER: It's a great honor, of course, to be appointed that because they have a very strict criteria to get that position. Typically, they're senior research scientists already. It was created a long time ago. Gentry Lee, in particular, who's our top system engineer, he wanted to continue in his hands-on system engineering without being a manager. He worked, I think, with Charles to have the fellow position created.

ZIERLER: Charles Elachi?

WEBSTER: Mm-hmm. This fellow position was such that you could get the same salary, basically [laugh], that you could if you were a director or a manager. It was not to push talented researchers into management, and lose them into management. It's a way of creating more equity amongst technical people and managerial people.

ZIERLER: Let's go to your expertise now. First, on the science and engineering side, are you all on the science? Are there aspects of what you do that are engineering?

WEBSTER: Oh, very much. Basically, I'm fundamentally an experimentalist, and that's been my whole history. I'm hands-on. I'm either in the lab or I'm in the field doing fieldwork, balloons, aircraft, whatever, or I'm doing technology development. My overarching expertise is high-sensitivity detection, especially of gases and isotope ratios using laser techniques. I spend a bit of time developing instruments, building them, flying them to make measurements of Earth, polar, ozone, other things like that over the years, or proposing, and developing them, and operating them on Mars. I have an instrument on Mars, and one going to Venus, one being proposed for Saturn, etc. All that traces to this development over the decades (even before it came to JPL) of laser spectroscopy. I'm a laser spectroscopist with a focus on the applications, but I do not shy away from doing the science, and writing the first author papers of the results that we get.

ZIERLER: In terms of your educational trajectory, are you a scientist who took on engineering, or are you an engineer who took on science?

WEBSTER: It's not that simple.

ZIERLER: OK. [laugh]

WEBSTER: I wouldn't classify—

ZIERLER: It's all mixed in?

WEBSTER: It's mixed in. There are many great scientists and not so great over the years who do lab work, I mean, Tesla and all.

ZIERLER: Of course.

WEBSTER: It's entwined, even from Newton onwards. That separates us from the theoreticians who do theoretical modeling. We're people that make measurements or get to make measurements on other planets. By definition, we've been making measurements in the lab or in the field to establish that capability.

Laser Spectroscopy as Home Base

ZIERLER: Both for engineering and science. Is laser spectroscopy your home base?

WEBSTER: Yes.

ZIERLER: Let's just do some laser spectroscopy 101. What is that? What is laser spectroscopy?

WEBSTER: Laser spectroscopy covers a variety of techniques, but it's basically using the optical spectra, let's say. First of all, it partitions, whether it's gas, liquid, or solid. I focus on the gases, atmospheric gases, in particular. Then the laser spectroscopy can be—you use any wavelength, and that's from ultraviolet all the way through to infrared microwave, to detect those gases through, again, another variety of techniques: laser absorption that I use. You can do laser fluorescence. You can do laser emission. You can do optoacoustic, galvanic, all different detection techniques. I've worked on all those techniques and many wavelengths in my youth that the last decade or two decades, let's say, I've focused on infrared laser absorption as the technique.

ZIERLER: Now, the history of laser spectroscopy, was this already a mature discipline when you came of age, or were you part of that founding generation?

WEBSTER: It was it was a maturing area, that's for sure. I was very lucky when I came here in JPL in 1981, they had these new infrared semiconductor lasers, and they were very difficult to work with, etc., but they were the first tunable diode lasers that were developed. We had a colleague, Frank Tittel, who would put them in the lab, and shine them through cells. But I was actually the first person in the world to make an atmospheric measurement. It was on a balloon using these new infrared tunable diode lasers. I was lucky to be part of that pioneering application that today has just mushroomed, even within our own group. We have them on the Space Station, and fighter pilots wear them in their mask, the same instrument. We actually build them in my group.

ZIERLER: To monitor pilot health?

WEBSTER: Yeah, oxygen, CO₂, and water. Lance Christensen developed them for the Orion spacecraft that's about to take astronauts for the next round. Under the floorboards, we have versions of this little instrument that we developed for that to do, again, oxygen, CO₂. They can hook up their space suits to it, and get measurements too.

ZIERLER: Let's stick with the science. What are some of the science objectives that you've been after in the course of your career? What are the big questions you've posed?

WEBSTER: I don't think I sat around and posed big questions. When you're an instrument developer, it's an iterative procedure. You get results in the lab, and you wonder what it could measure, and you find out what the challenges are or what the big questions others pose. I'm just being frank here.

ZIERLER: Of course.

WEBSTER: You try to see if your technique is suitable, how suitable, could it address some of these? It's this developing synergy between your capability instrumentation and the needs, whether it's Earth science or planetary. As far as science goes, with these very early measurements in the '80s, there was a great need to understand the photochemistry of the upper atmosphere because everybody was focused on ozone in the midlatitudes. By flying this 3,500-pound instrument with liquid helium, it was a huge effort. We made the first measurements of NO and NO₂ in the stratosphere and ozone, of course. We could see the transformation of sunrise and sunset between nitric oxide and nitrogen dioxide during these transitions, and therefore map not only their abundance but their diurnal behavior with N₂0₅ as a reservoir. We were doing fundamental photochemistry that impacted the midlatitude ozone. This was before the ozone hole was discovered. We made some really excellent measurements and results and impact on that area.

ZIERLER: JPL was involved in Earth science as early as the early '80s?

WEBSTER: Oh, absolutely. In fact, we had some big players in that domain, and we were very much involved in the polar ozone crisis and loss and protocol. That came about, you probably know the story, Joe Farman from the British Antarctic Survey.

ZIERLER: Yes.

WEBSTER: He went down there, and he said, "There's no ozone." NASA said, "Oh, what? The TOMS satellite says it's fine," because they had a couple of errors in the code that just replaced the low ozone with normal values. That was in 1985, I believe. But when they took that code out of the satellite, the ozone hole had actually started in 1978, so we were already seven years behind it. NASA, the Earth sciences started putting money into developing aircraft instruments. I developed my instrument. It got smaller, at only 150 pounds now, and it went in a pod with 28 other instruments into the U-2, or ER-2 it's called. But it was the same plane that was shot down with Gary Powers in the '60s, a spy plane. But we put it into that, and we flew into the polar regions, the South Pole, the North Pole, out of all over the world but especially Sweden, Kiruna, and Bangor, Maine. The pilot would make these eight-hour trips, come back, and we'd download our data and look at it. This tunable laser spectrometer that I had, it was pivotal because it measured hydrogen chloride, which is the principal reservoir of chlorine in the stratosphere and in the ozone hole region, etc. At the same time, Jim Anderson's group at Harvard was measuring the active chlorine, the chlorine monoxide. As we flew into the hole, we could see this beautiful anticorrelation between the reservoir, stable HCl that we were measuring, and the reactive, radical chlorine monoxide. That began to tell us where the chlorine was coming from that potentially was attacking the ozone. It took the brilliance of Susan Solomon to postulate that it was on polar stratospheric clouds, these nitric acid hydrate clouds that form in the very cold descending vortex. That was an absolutely way-ahead-of-its-time prediction, and it turned out to be true. I should also point out, before that, when chlorine was recognized from chlorofluorocarbon sources as the potential culprit for the ozone loss, we had Mario Molina at JPL. He's the scientist with Sherry Rowland who first postulated and showed in the lab that chlorine could attack ozone, so that work was all done. It's a very exciting time. JPL had other groups. They had Barney Farmer who had an FTIR looking up or the sunset, sunrise. Joe Waters was coming into strength, and developing his Microwave Limb Sounder to look at multiple species simultaneously. JPL actually played a huge role in the measurement capability that contributed to the understanding of the ozone hole, and also eventually the Montreal Protocol, and the policies that went into place. That's often underplayed because there was NOAA, there was Harvard, there were other groups involved, but we were very much involved—a lot of the Earth science funding went into the polar ozone issues. That was the big budget in those days, in the '80s and 90's

ZIERLER: This is all to explain that you develop the capability, and then you see what it could be used to measure, as you were explaining?

WEBSTER: Yes.

ZIERLER: You're sort of opportunistic. You're not thinking about the science first. It's the capability first?

WEBSTER: I think, yeah it's true. That's true. In fact, even in those early days, I developed a miniature version of this, the laser multi-passes in a little gas cell, and we actually had it on the Huygens probe of the Cassini mission. But it had to have a Joule-Thomson cooler, which is high pressure. They were worried it would blow up, and destroy the probe. We only survived Phase A, and then they kicked us off, basically—and rightly so, in hindsight, now that I understand flight projects. From an early time, even the '80s, I had one eye to the planets too, because of the capability, and it was recognized. If I may say, the tunable laser technique is so powerful and in demand for the in situ measurement, you know, sniffing gas in front of you or in a cell. It's not a remote sensing. It's so in demand because the other technique is mass spectrometry. Mass spectrometry, you have a spectrum by mass, but there's nothing you can do about the fact that carbon-13 is 100 times less than the parent carbon-12, for example.

ZIERLER: Less what? Less dense?

WEBSTER: Less in amplitude, the signal, or the number of molecules. But the signal, especially, that you record is 100 times weaker, by definition. With the optical techniques, there are so many infrared, let's say, bands, you can find bands that overlap to such an extent that you can pick up weaker rotational lines of a given, the parent, CO₂ that overlap or in the same region as the stronger lines of the carbon-13. When you record your spectrum, the carbon-13 and carbon-12 lines are a similar size, and electronics loves that, ratioing lines to get the isotope ratio. We have that advantage, but also all the mass spectrometers, and you can see that from the Cassini results for the low simple gases, methane, ammonia, and water, of low mass on a mass spec, generally they're all stomping on each other, and especially if you start adding neutrons to make isotopes, that the overlap is very difficult to do carbon, hydrogen, and oxygen isotope ratios of the mass spectrometer because of that. Whereas in the optical region from 1 to 15 microns, you have so many rotational lines in so many infrared bands, and so many wavelength choices, you can choose your region to have unambiguous determinations with no interference, despite large differences and abundances, whatever.

ZIERLER: Now, when we say laser spectroscopy, is it only one kind of laser, or are you utilizing a variety of lasers?

WEBSTER: There are, of course, a variety. I've worked with a variety: liquid lasers, gas lasers. I've done it all in some ways in my earlier days. But the technique that's so important for planetary science that's my focus now, and was important for Earth science, are semiconductor infrared lasers. They're tiny. A whole package is the size of a dime, so they're small devices. Within that structure, there are several. There's tunable diode lasers. There's quantum cascade lasers. There's interband cascade. There's a variety of engineering ways of developing the little junctions that produce the light. But these are all infrared. They're all 1 to 12 microns, which is a huge range to choose lines from.

ZIERLER: Have you ever talked with Amnon Yariv about semiconductor lasers?

WEBSTER: A long, long time ago. I'm sure he wouldn't remember me now. He was a pioneer, without a doubt.

ZIERLER: Now, when you say planetary science, does that include the Earth? Are you looking at all planets available to study, or is there a different research agenda as you apply it to Earth and to other planets?

WEBSTER: I think not. Earth now is so well covered by the remote sensing, the remote sensing has taken over. In situ sensing is really all about local measurements. Although there has been that synergy in Earth science over decades, remote sensing now has got so good looking at not just clouds but looking at canopy tops and foliage and other aspects of the Earth and dust that for Earth science, I would say, it's matured into remote sensing, principally. For the planets, however, it's all about proposing missions. The missions can only take small instruments. They can only take a certain mass. They're very limited in what they can do. While we still go to planets and do orbital measurements, they typically cannot have the same capability the Earth has. Then there are clouds, for example Venus, sulfuric acid clouds, or Saturn. You can't often see below that too. A lot of the planetary missions focus on probes. These are in situ, one-hour probes that go down, and they have the combination of the mass spectrometer, which is absolutely powerful and unique for noble gases, what Ken Farley has worked on, which are the most important measurement in a planet today, noble gases. My instrument cannot measure it in a million years. There's no—

ZIERLER: What does it lack?

WEBSTER: The noble gases do not have a change in the dipole moment. In order to have an infrared transition, you need a change in the dipole moment. Microwave, you just need a dipole moment. Infrared, you need a change in it through vibration, typically, to be infrared active and, therefore, to have spectral lines. Most of these probes now have the combination of the mass spec and the TLS, tunable laser spectrometer.

ZIERLER: What planets have you studied or, more properly, what missions have been going on that have allowed you to explore these techniques?

WEBSTER: We had a miniature tunable laser spectrometer from JPL on the Mars '98 mission. That was our first attempt at getting isotope ratios.

ZIERLER: You were right there at the beginning?

WEBSTER: Oh yeah, I was there since '81, so the beginning of time—

ZIERLER: [laugh]

WEBSTER: —with Dave Paige at UCLA. He was the PI on that. Randy May in my group was a lead on that. The Mars 98 'crashed, as you know, before it hit the surface or as it hit the surface, and so that was lost forever. We kept proposing. We had all kinds of this. I probably had 100 proposals for Mars or Mars airplanes. We had Mars—

ZIERLER: This is the climate orbiter you're talking about, not the Polar Lander?

WEBSTER: No, the Polar Lander.

ZIERLER: Oh, it was the Polar Lander.

WEBSTER: Remember, we're in situ. We need to get on the surface, and sniff the atmosphere with the mass spec so, yeah, it was the Polar Lander. Then we had aircraft proposals from various institutions, and sondes and drops and rovers that came and went. We proposed things that would drill down in the ice layers, and do the climate record, like we do on Earth, with oxygen-18 or D/H ratios to tell you the climate history of Mars. These were all proposals that never got selected until we teamed up with NASA Goddard, Paul Mahaffy's group, and proposed for the Curiosity rover. That was our big start, if you like. We were selected as part of the SAM suite on Curiosity. This was the first time JPL had ever built a flight tunable laser spectrometer, so we had our [laugh] trouble. NASA selected us at less money than we asked for, and then we got in trouble, and we ended up costing more. We were a four-channel instrument. We ended up being a two-channel because of mass. The mass was so tight, we lost a third channel for 150 grams. That's how tight the mass on that rover was, the budget of allocations. We got on the Curiosity rover and, boom, we did spectacular science—the SAM suite as a whole did. Ken Farley did his pioneering age dating. We've had organic detection. A whole variety of incredible high-impact science from SAM along this in situ suite. The TLS focused on, for the first time, measuring the carbon and oxygen isotope ratios that tell you about atmospheric escape through the different ratios. We also looked at rocks, and measured the D/H in rocks. First time it's ever been done on another planet in situ. Looking at this Hesperian mud and clays, the D/H ratio was such that it told us that if Mars began looking like Earth with standard mean ocean capability—and today we know through escape processes, it's severely depleted—we got the point, another point on that curve that allowed us to say that three billion years ago, just, Mars had already lost half of its water. That was a huge scientific result there. TLS also did the atmospheric methane, which was hugely interesting, controversial, shocking, and remains that way, I would say.

The Mars Methane Controversy

ZIERLER: What's the controversy?

WEBSTER: It began because Michael Mumma and others through remote sensing and telescopes thought there was 500 parts per billion methane that became 250 that became 120. It kept halving every AGU meeting. But there were no measurements of it at all. It was shocking that there'd be so much methane on Mars. Generally, the excitement was if it's there in the atmosphere today, it's got to be recent compared to the billions-year history. Everybody was excited that it was through methanogenesis or some biological method, just like on Earth. Most, 90% of the methane on Earth is from marshes and termites. Biology, basically, is produced through biological processes. That was the excitement. We got to Mars, we landed, and we had a little bit of methane in our foreoptics that we had to subtract out, which it was an easy subtraction, and still is. But, nevertheless, we made three or four or five measurements, and we said, "There's no methane on Mars." We were the first people to report that, and it was shocking. I'd give talks, and the press were just, "Say it isn't so." People were very upset. We published in Science a paper with a two-sigma upper limit of 1.3 parts per billion compared to this 40, 60, 100 part per billion that previous Science papers had reported. That was really shocking. But as time went on with Curiosity, we had two, maybe three occasions where we saw five parts per billion. That became a spike, which again got a lot of excitement. Then after two or three years, we went to our enrichment run, which is when you suck the Mars air in, and you pass it over a CO₂ scrubber, and the methane goes straight through. If you do that for two hours, you effectively enrich the methane or your capability of detecting it. We went into this regime where we could see .1 part per billion methane.

As we went year after year, we created this apparent seasonal cycle to the methane. It seemed to peak in the summertime, and it seemed to be lower in the springtime. That was the first step. A lot of controversy because it's a weak seasonal cycle, but it seems to be reproducible every year. We get our highest values of half a part per billion, and our lowest values of .2 parts per billion. It's not a big effect, but it seems to be repeatable from year to year. Kevin Zahnle and a couple of others went on the warpath that the methane was coming from the rover, and in particular from our foreoptics. We've had to spend some time showing that there's not a hope that any of those foreoptics molecules could make it into the cell, because they show no degradation with many, many years on the surface. When you suck that air in the Curiosity rover, you have winds of one, two, five meters per second, and you're sucking in for two hours. The sheer number of molecules that we ingest is tens of thousand times more molecules than we actually have in the foreoptics, even if they were all to escape, which they haven't because we measure them. That's been pretty much put to rest. But there's still this nagging worry that something on the rover somehow creates the methane that we ingest. But, again, no one has any ideas what could possibly create that much methane that is blowing in this meters-per-second wind as it's ingested, and still has half a part per billion.

ZIERLER: Has anybody discussed the possibility of detaching the instrument, and letting the rover go away—

WEBSTER: No, no, no.

ZIERLER: —to fully put to rest—?

WEBSTER: It couldn't be done.

ZIERLER: Could not be done?

WEBSTER: No. We're right in the belly, and we're bolted in there forever. Since that time, the Europeans put the ExoMars into orbit, and they started making measurements, and they said there is no methane and, I mean, no methane at parts per trillion. They have never detected methane. On the downside, they struggle to get below 10 kilometers. We're only a meter above the surface. They struggle to get below 10, and sometimes they can get a few kilometers.

ZIERLER: It's not a slam dunk?

WEBSTER: It's not a slam dunk the fact they see nothing. However, now you come up with a theory, as we did with great people like Sushil Atreya and others working on this too. We came up with the postulate that the methane we see is microseepage from the surface, and the dynamics people told us that the mixing or boundary layer, which is high during the day, there's a lot of—the molecules are kissing the surface, literally, and tumbling and mixing well. But during the night, that boundary layer descends to only a meter above the surface, so it traps the continuous microseepage, and concentrates it, and that's where we see our half-a-part per billion. It's a result of it being concentrated. The problem with that though is that if you say there must be other sources, not just Gale crater, and you—even at those low levels, because methane has a lifetime of 300 years, eventually it should dilute into the main atmosphere, and it should be detectable, maybe 400 parts per trillion. But you can't just have a permanent source of methane and, with that kind of capability for the Europeans, they should be seeing some background level, even if it's small, but they don't. In the end, we thought, "Hmm, what can we do that's different?"

We came up with the idea. We did a night-day-night sequence with a few days apart. We went nighttime. We saw a half a part per billion as usual at the peak that season. Then a day or two later, we made a daytime measurement. We saw nothing. Sorry, did daytime first, we saw nothing. Then we went to the night, a day later, and saw half a part the billion, and then nothing. We proved that most of our data had been collected during the night that this apparently seasonal methane detection is nighttime methane, and it's not present during the day. We invoke mixing and the arguments about the boundary layer, etc. However, because they still detect nothing, we have to invoke fast heterogeneous type chemistry that's shortening the lifetime of methane. We still need a destructive mechanism to get rid of the methane we are detecting, because otherwise they would've seen it in orbit. That's the remaining controversy, and it's not solved, and it won't be solved for—

ZIERLER: Mars Sample Return will not resolve this?

WEBSTER: No. They have no capability to make any measurements at Mars. They're just going there to grab those samples. SAM and Curiosity is, I say, the last. Because of the Mars Sample Return, and the budget required for that, it's going to have a huge impact on not just Mars but on planetary science. On top of that, the Mars program is sort of declining, meaning that there's great interest in the outer planets now and the satellites. Those two factors, the Mars Sample Return budget, which is growing every year, and the need to go further out or to other planets, means it's unlikely there'll be another Curiosity to make any of those in situ measurements for at least a decade, I would predict.

ZIERLER: Let me ask, way far out, whatever that next mission is to Mars, do you see your research contributing to the two biggest questions as they relate to Mars, both the presence of life extant or past, and, way out into the future, the question of habitability, where a human base on Mars might finally solve this question?

WEBSTER: The life on Mars thing is very difficult, as you know. It's hard to go to the Atacama Desert or somewhere on Earth, and detect life and prove it.

ZIERLER: [laugh]

WEBSTER: If you go to a chalk quarry, it's quite hard to find a fossil.

ZIERLER: [laugh]

WEBSTER: It could happen, but it's unlikely. We've detected organic molecules, precursor molecules, so that's a good basis. Perseverance has also now detected organic molecules. Ken Farley's the person to ask that question, [laugh] by the way. There's a lot of fundamental or the building blocks for the potential for past life on Mars, but actually detecting hardcore evidence? The Allan Hills 84001, whatever, was very controversial. Remember the microfossils? That's generally thought not to be accepted right now.

ZIERLER: But in terms of its science objectives, is laser spectroscopy, is it geared toward looking for life, or can it be?

WEBSTER: It can only look for signatures in things like isotope ratios. If you were to look at the carbon-12, -13 ratio on Earth, typically it's 2% to 4% depleted because of the contribution of photosynthesis in plants. There are isotope ratios, especially carbon, that can be indicative of biological contribution.

ZIERLER: It's a piece of the puzzle?

WEBSTER: It's a piece of the puzzle, but there's no single measurement that can verify life detection.

ZIERLER: The question of habitability, figuring out is it even feasible to have a semi-permanent human station on Mars, does this research contribute to those questions?

WEBSTER: Not directly, but we have, for example, we have those same spectrometers that are going to the moon to do in-situ resource utilization.

ZIERLER: This is Trailblazer.

WEBSTER: No. It's—I've forgotten the name of it [laugh]—Light-something.

ZIERLER: We'll come back to it.

WEBSTER: Flashlight or something like that. But, yeah, there's many of those. They're useful for looking at oxygen generation. Just like we measure astronauts breathing, the laser spectroscopy is very good for looking at production of oxygen on Mars. That's more of an industrial commercial application. SHERLOC has this Deep UV laser fluorescence. Instead of scanning the laser, and looking at gas absorption, they have a fixed laser, and they look at the resulting fluorescent spectrum, for example, and they can detect organics. But detecting organics is still a long way off. Even going back to the carbon isotope ratios, people always say, "Can you see the carbon-13 of methane?" Because methanogenesis, the bacterial biological production of methane, should produce highly depleted carbon-13, because microbes are lazy. They want to use the 12. Why use the heavier 13? People have often asked that. But others, Bethany Ehlmann, a lot of geophysicists, geochemists have pointed out that even the basic serpentinization, the other methods of producing methane through rock chemistry, can also produce depleted carbon-13. Even that signature has been taken away from us, if you like, by the ambiguity of the result, so even that is not a test for the presence of biology let alone life, well, the same thing.

ZIERLER: Now, where beyond Mars have you done non-terrestrial science?

Next Stop Venus

WEBSTER: The instrument on Curiosity has been highly successful for 12 years, pretty much. The data we've collected, whether it's rocks or gases or isotope ratios, has been really, as I said, high impact. We're very proud of that, and proud to be part of this teaming JPL with Goddard that's produced this. With that same team, we were now selected on the Venus mission, the DAVINCI probe to Venus. We're actually selected. We're beginning.

ZIERLER: What's the timing on that?

WEBSTER: I think it's 2029 launch—

ZIERLER: Oh wow.

WEBSTER: —something like that.

ZIERLER: Not too far off.

WEBSTER: It's not too far. Let's see what—yeah, something like that.

ZIERLER: This is to hang out in the atmosphere? This is a landing?

WEBSTER: No.

ZIERLER: It's too hot, right?

WEBSTER: Yeah. This is a mission that will go to Venus, and have an orbiting capability, somewhat simple, obviously. But the main component of the mission is a probe with a parachute. It's going to be released at the top, go through the sulfuric, and as it goes down, with ingesting, we're going to sample the vertical profile of gases. We're going to measure CO₂, of course, SO₂, OCS, CO, all the major components. We're also going to be measuring their isotope ratios as we go down too. Once it hits the surface, it may survive for an hour or so before it melts, but it's mainly the vertical profile. Most important, the mass spec will focus on the noble gas isotope ratios, which are key to the planetary evolution and migration. As important as TLS is, and as capable as it is, if you had to go to any planet, and could only do one measurement, it would be noble gas at relative abundances.

ZIERLER: Because you can infer so many other things from noble gas measures?

WEBSTER: Yes, exactly, and they're very robust against change and other aspects from primordial values, apparently.

ZIERLER: DAVINCI, the whole point is it needs to beam up its data before it hits the surface and melts?

WEBSTER: Absolutely, yeah. Now I should point out the Russians were all—

ZIERLER: It was their planet for a long time. [laugh]

WEBSTER: They crashed on the moon recently.

ZIERLER: Yes.

WEBSTER: But they landed in '76, I think it was, and apparently it lasted two or three hours on the surface before it melted. There was a time they were the leaders in that area. We find this'll be the first time we're back to Venus. We've proposed this six or seven times. That's the nature of these planetary missions. You've got to propose them to death, and eventually you might get selected.

ZIERLER: Chris, what about the outer worlds, the icy planets, the satellites of Jupiter and Uranus and Saturn?

WEBSTER: Again, we are proposing right now. We're on two proposals for the next round of New Frontiers, for example. There'll be six or eight or ten proposals to various bodies. But the TLS is on a Saturn probe. This is a similar thing to the gas giant Saturn, and it will go through the atmosphere, a one-hour descent. It's a hydrogen-helium atmosphere, so it's very different from Venus, and it's challenging. We're also on an Enceladus lander, so this is to land on Enceladus, and do what SAM did so well on Mars, that is, we have a helium tank, and we heat up rocks. The helium flushes them over the mass spec and the TLS, and we measure gases released, including isotope ratio. It's to go there and sample the surface, the ices, ammonia, methane, other things on the surface to look at the composition, and hopefully get a handle on the history of the Enceladus plumes and their composition, and things like that. They're two proposals. Then I've been attending a Uranus flagship development with a JPLer leading us. That's way down the pipeline. But, for me personally, they're limited because I'll be 80. I'm 70 now. I'll be 80 when we get to Venus, and I'll be 92 if the Saturn mission gets selected. That's why I have protégés who are much younger than I am to take over that.

ZIERLER: Diet and exercise, stick around. [laugh]

WEBSTER: Yeah, exactly. That's going to be hard.

ZIERLER: When in your career did you take on both the terrestrial, the Earth science, and the planetary science? Did that happen in tandem? Was it that you got to JPL, and you saw there's a whole solar system to explore?

WEBSTER: I think both of those. It happened in tandem. I was exposed to these, like the Cassini mission, or somebody, I don't know who, said "Could you do anything on that Huygens probe?" That's the way things happened. My upbringing was such that I was not somebody who gazed up at the stars, and always wanted to go to Mars, or anything like that. That was never my passion.

ZIERLER: Let's trace that story.

WEBSTER: [laugh]

ZIERLER: Your family background is Scottish?

WEBSTER: Yeah. My mother was English, and my father Scottish. He was a coal miner in Scotland, and we eventually moved down to England.

ZIERLER: What were your parents' experiences during World War II?

WEBSTER: They were on the latter end of it. They were actually in Egypt, east of Suez. That's where they met. But my mother would push her sister in a pram during the Blitz, so she was a young girl, and terrified of that. She found one of her relatives in a cupboard holding a baby that was still alive, but the mother was dead. Oh, so horrible experiences. This was the Blitz time. My father and mother came. He was in the Royal Air Force, but he was a mad, crazy, brilliant, redheaded fighter. He would fight, and would have these massive bicycle chain fights at one point. They wanted to punish him, and they sent him to the furthest outpost in Britain. It was this little Island of Anglesey in Wales, and that's where I was born, because my mom was pregnant at the time. I'm technically Welsh but should have been Scottish like all the other four brothers and sister—three brothers and sister. We were brought up in South London. At 10 years old, I had a traumatic event happen that made me fail, quote, my eleven-plus. I was a smart kid, but things went south for me.

ZIERLER: Eleven-plus determines where you go to high school?

WEBSTER: In those days, in the '60s, do you go to grammar school and therefore have a chance of going to college—we call it university—or do you go to industrial, you know?

ZIERLER: It's a white-collar, blue-collar fork in the road?

WEBSTER: Absolutely, and very important. I didn't make that, but I was fortunate. I went to a rough school in London [laugh], but I became top of the class every year. I got the book, the prize every year, and that did so much for my ego and self-esteem and confidence, more than being mediocre at a grammar school, as we call it. I succeeded. I became the first kid in the history of that school to go to university, for example. Now, at that point, they wanted to cane me in front of the whole school because I was a terrible practical joker, smoker, thief. We were bad kids, me and my brothers, for a long time. French and English literature were my loves at the time. My brother had just started doing microbiology. He went to grammar school, my older brother, at Reading. My father said, "You're bloody well going to Reading, and you're going to do chemistry like your brother."

My dreams of being an artist fizzled, and I ended up at Reading, and I did chemistry, and I have to say I didn't enjoy it. I wrote these long essays to the professors, telling them how they could make their classes more interesting and appealing to people. I was frustrated at that. But I was very fortunate at the next step because, let's see, I had my bachelor's degree in chemical physics, and then I got interested in valence theory and atoms and molecules. That was quite fascinating to me, so I applied to work with Charlie Coulson, who was the biggest name in Britain at Oxford University. He wrote the book on waves and wave theory and everything in those days. But he died the month before I was about to arrive, and they said, "You should work with Richard Dixon at Bristol. He's the head of theory." I went to Bristol to do theory, but I didn't know that he was an experimentalist who was heading the theoretical department. Within a week or two, he took me down into the bay, and he had received the first dye laser, liquid dye laser, and gas lasers in England. They'd just been invented and produced. This was probably 1970-ish, '74 maybe, '77 or so. I helped him unpack it and set it up in the lab. That was the beginning of my whole career in experimental science because I soon discovered, as he did, that I had the magic fingers for tweaking up lasers, and getting the power and the wavelength. I'd had a background at Reading doing spectroscopy for projects. But I fell in love with this lab work using these lasers. That was the beginning of the career change, if you like, from the earlier [laugh] interest in arts.

ZIERLER: What were the science objectives at the lab at Bristol?

WEBSTER: I'm sure they could provide some to you, but the research group we were in was trying to test various theories, for example. Again, we did spectacular high-visibility work again, looking at things like this weird Duschinsky effect in chromyl chloride. Quantum theory fascinates me. The idea that at these tiny scales, molecules can only rotate or vibrate at certain frequencies is mind-boggling. Why can't it go at any frequency? It's mind-blowing. If it wasn't for the quantization of energy, we wouldn't have any spectra. If we didn't have any spectra, we would know nothing. We wouldn't be able to do anything in life. We'd be so restricted. When you think how spectroscopy contributes to everything in our lives, we wouldn't know what the sun was made of even, early on. I would say the department were looking for things they could measure that would challenge the basic understanding of quantum mechanics, angular momentum, and the theoretical understanding of observed spectra. By the way, the implications go all the way to astrophysics.

ZIERLER: Of course.

WEBSTER: JWST would just see a rainbow. There'd be nothing to report if it wasn't for that. It's a really powerful observation, this unusual behavior at very small scale results in such a powerful tool for human beings to reveal the whole universe in front of them, and in front of their nose too.

ZIERLER: What was your thesis research at Bristol?

WEBSTER: Mine was in three parts. I was the first person to measure the dipole moment of a molecule in an excited state. Dipole moments are usually done by microwave in the ground electronic state, but by using a dye laser, and moving—it was hydrogen. It was H2CS via formaldehyde. By exciting it, you could measure the dipole moment too, and that tells you about transitions. I did the Stark effect, that was, for the first time. Optoacoustic. We developed this technique. It was really, again, at the cutting edge, where you shine your laser through a little cell of gas, and instead of having a detector, and looking for absorption lines, you put a microphone on the cell, and you listen for the sound as you tune through the lines, because all the energy the molecules absorb, it degrades to translational sound energy. We hooked up a microphone—there were others that were pioneering this at the same time—and started recording spectra. Really sensitive. This was incredibly sensitive. We could look at things like S2O and these other gases important in planetary atmospheres, and then the fluorescent spectra, chromyl chloride. It had sort of three experimental parts, I would say.

ZIERLER: Were they separate? Were they all related to a bigger theme?

WEBSTER: They were related to the bigger picture of how visible electronic spectroscopy can help develop theories and inform us about various processes. But they were in some ways separate studies.

ZIERLER: What year did you defend?

WEBSTER: 1977 I was 24 years old—

ZIERLER: Oh wow.

WEBSTER: —getting a PhD. I had to tell my kids that—

ZIERLER: That's a fast PhD.

From the UK to Paris to USA

WEBSTER: In England, it wasn't, so that was more normal in England, especially in those days, three years. If you didn't get it in three years, and you were in your fourth year, you were kind of a slacker—

ZIERLER: [laugh]

WEBSTER: —and then they would give the master's degree. In those days, it was a consolation. They wouldn't give you a PhD. You can have a master's. It was a different world. At 24, I had that, and I went to Paris to do a postdoc, this time looking with more in the ultraviolet, looking at these weird molecules like rare gases. We talk about noble gases that bind with alkaline metals when they're hot, but they don't exist when they're cold. They're called excimers and exciplexes.

ZIERLER: What institute in Paris?

WEBSTER: It was the Paris Observatory at Meudon where Rodin was born, and stuff like that. That was the most beautiful time of my life [laugh] because—

ZIERLER: How was your French?

WEBSTER: C'est pas mal.

ZIERLER: OK. [laugh]

WEBSTER: The Observatory's surrounded by this big, high wall, and we lived in this little bois de Chaville or the little woods of Chaville, a little studio apartment. I was married by then; no kids. I would get on my bike. It had a motor on the front, a velomoteur, and I could take a shortcut to the wall, dust myself, jump over the wall when the guards and the Alsatians had gone by, and go into my lab. Otherwise, they made you go this one—it's a one-mile driveway up the main gates. It's so splendid. They had a beautiful lake there. We had two-hour lunches, and five-course meals for lunch. It was a two-hour lunch period. The Europeans, they know how to enjoy life and science. Whereas I was, I'll say, shocked, but Americans work so hard in every area.

ZIERLER: Who was your mentor in Paris?

WEBSTER: I should say at Bristol, it was Professor Richard Dixon. He's world famous. He literally wrote the book on spectroscopy. I've been very fortunate to have these great mentors, if you like. François Rostas and his wife Joelle, they both worked there. They were both incredible scientists too.

ZIERLER: A husband and wife team?

WEBSTER: Yes, and that was very normal in the same lab. I guess the Pasteurs[?] established that. I had a wonderful time there. Then I gave a talk in Edinburgh on this, and this kind of charming professor invited me to go to Stanford. He said, "Why don't you come to Stanford?" I thought OK. He'd just left Columbia, Richard Zare or Dick Zare, again, a huge—probably the most famous chemist in the United States, certainly at the time. He was a big name. I came to Stanford with my first child, a newborn, and took up doing again, I did isotope—

ZIERLER: This was a faculty appointment at Stanford?

WEBSTER: No, a postdoc, second postdoc. GTE Sylvania and others, they wanted more efficient light bulbs. We figured out if we could enrich the 196 component of Mercury, they would work a bit better through various electronic processes. I did that. We actually increased the efficiency by 10% of fluorescent light bulbs, which was huge, by the way. That was an application science. We developed these optogalvanic techniques. I did that with Charlie Rettner, that we could create ions as you scan through a gas, and measure photodetachment thresholds. All the physics community were excited about that. I did more laser stark and laser optoacoustic, laser optogalvanic, and all different wavelengths. Again, I had this great, rich experience in multiple wavelength regions, and multiple techniques of all different laser sources. Then after two years there, I applied for jobs, as anyone would, and JPL gave me an offer. I married an Englishwoman. We had this six-month old Genevieve[?], my daughter, who's now 40. I was earning $5,000 a year. That was my postdoc salary. This would be 1980. That was it. JPL gave me a letter that said $700 a week. It was $36,000 a year. We were in shock.

ZIERLER: [laugh]

WEBSTER: We were dancing around the room. We couldn't believe it. She kept making me call JPL and say, "That 700, is it a month or is that—?" "No, that's a week." We had to keep calling them. "No, that's $36,000 a year. Is that what you're saying?" We were just blown away. But now, of course, you realize it doesn't go as far as you think it does.

Joining JPL

ZIERLER: Now, were you looking at faculty positions also at that point, or did you want a lab kind of environment, like at JPL?

WEBSTER: It was sort of mixed. But I would say, a few years later, I was seduced a little bit about the possibility of going to—in fact, actually, I think it was 1993. Our kids were growing up. I'd been doing a lot of fieldwork. I'd been all over the world—New Zealand, Sweden, you name it, Hawaii—all over the world, making these aircraft measurements, and it had an impact on my marriage, obviously, to some extent. Round about then, I was offered a professorship at Cambridge University because of the Earth science measurements capability. But my wife convinced me to stay here, and it was a year later I found out her reasons [laugh] weren't of the scientific nature. She was involved with someone else—

ZIERLER: Oh.

WEBSTER: —and she didn't want to leave. That choice was made for me. But I do believe in serendipity, and I think it wasn't the wrong choice. They were both good choices. Staying at JPL allowed me to get on a Mars mission, which is a lifetime achievement, if you like, for anyone, or a privilege for anyone. It ended up being a good thing either way. But JPL can be very appreciative of their staff.

ZIERLER: Were you able to buy a house right away when you joined JPL?

WEBSTER: We did because I got £5,000—or dollars, let's say—from England from my parents, who were later in their career. That was a down—where we bought a house for—I was mad because we paid 130,000 for it in Pasadena, and my friend bought one for 126,000, and we thought we'd been cheated.

ZIERLER: [laugh]

WEBSTER: It was a rip-off. We bought a little house in Northeast Pasadena that sold at a loss after this tremendously awful divorce, I mean, insanity. That's another subject. Eventually, I married a second time with two more kids, one of whom has serious mental health challenges. That ended up in divorce, so I've been married twice, and divorced twice. Now, the last 10 years, I live alone and love it. I rent an apartment in Montrose, so I have a very low—

ZIERLER: A simpler life?

WEBSTER: —overheads. A simpler life, yeah, a small apartment. It's the best. It's the happiest I've been.

ZIERLER: What was your original appointment at JPL? Were you in the same directorate that you're in now, the Science Division?

WEBSTER: Yes, I was in the same division. I was appointed, and then I was doing very well with the Earth science. Dan McCleese, who was a young up-and-coming—becoming division manager, he actually saw in me some leadership skills, I guess, and he made me a group supervisor, and broke up this big group I was in. That's when I really blossomed, if you like. He was the one who made the changes that allowed me to take leadership for a group. But things at JPL have changed from those days so much. For research, it's very different.

ZIERLER: Less bureaucracy back then, I imagine.

WEBSTER: That too. First of all, at division parties, we'd all have scotch and any alcohol you wanted in the division office, and we'd keep whiskey in our offices for visitors. [laugh] This is in the '80s. Everybody smoked in their office. I became a section manager, and had to put out a fire because somebody who should be nameless set fire to their office with their pipe.

ZIERLER: [laugh]

WEBSTER: They were different days. Barney Farmer would tell me in the mid-80s, when you wanted to travel somewhere to a conference, you went down, your secretary got your tickets, you went to the JPL helicopter pad there, you get on the helicopter, and they would drop you, whether it's LAX, on the other side of the gate, next to the plane. You'd hand them your tickets, and walk up the stairs.

ZIERLER: Life was good. [laugh]

WEBSTER: A different world, for senior people, I guess. I never had that. But I was thinking more in terms of in the scientific and research domain, so in the '80s and '90s, a lot of the leadership was embroiled in these demigod-like leaders. We had these massive scientists, men and women, who led research groups of 10, 20, 30 people. Barney Farmer was a good example. Joe Waters was one of the last of that domain, for example. The group leaders also were the rainmakers, meaning, they wrote the proposals; they got the money from headquarters; they negotiated with headquarters. It was very much these empires. Joe had the whole of the seventh floor of our building, for example. But there were many like that: Reinhard Beer, Joe Waters and Lee Fu in oceanography.

There were these very larger-than-life leaders who led groups, and they had their own engineers, their own technicians, their own secretaries. Even the secretarial support was very group-oriented and very different. JPL didn't like that as they became more oriented towards flight project structure. It's like the flight projects, it's all about requirements and margins and process. That sort of funneled into the research, and they didn't like—because when someone like me or Barney or Joe had a problem, we went up to the ninth floor, and got what we wanted. We were very powerful people. The management in between was regarded as management that was in the way, of bureaucrats. That changed with Charles. He shaped it to give more power to the—even though that's—Charles Elachi was a great example of that earlier—that's how he, his group, his leadership, his capability. As time went on they, they—this nebulous they—didn't like these powerful kingdoms or queendoms, whatever you want to call it, and they said about dismantling them. The groups were broken up. People today have supervisors that have nothing to do with their subject matter. A group supervisor is more like a bureaucratic link; not always but often. It's very different. The people who normally would've been in my group are now in five different groups, and they all have group supervisors that are not in the same field or different. It's very rare. If you have a group now, it'll have four or five scientists who have little money. It's all spread. Everything's spread through multiple accounts, multiple PIs all in one group. Before, the head of the group was the strength, and everyone else's salary depended on that person and their career and their future, everything. That's probably the biggest change I've seen in time. I'm not saying it's better or worse. It's very different now.

Focus on Atmospheric Science

ZIERLER: Now, your immediate focus was atmospheric science when you got to JPL?

WEBSTER: Yes. It was always the balloon measurements for the ozone-related chemistry, and then the aircraft for the polar ozone in particular. Then we did a lot of tropical transport and other issues, looking at methane, N₂O, other things, and then the planetary missions, atmospheric or heated-up rocks that produce atmospheric gases.

ZIERLER: Do you remember the exchange or the project that pulled you into planetary science, what that opportunity was?

WEBSTER: I would say the Huygens probe interest, which somehow fell in my lap in terms of me thinking about it, I don't know if I thought about it or someone suggested it. I honestly don't remember. That was in the '80s. But that got me interested in that, and then Mars was a natural—people would mention, "Could you do this on Mars?" I'd look at it, and then go, "Methane, yeah, we can do that easy."

ZIERLER: Let's stay on Huygens probe for a second. What was the question for which this instrument could be of use?

WEBSTER: It was very simple. It was, again, like all these subsequent themes, was the atmospheric composition. What are the main components of the atmosphere of Titan, and what are their relative ratios? In the end, a lot of these planetary missions for the gas measurements, they want to know the elemental ratios to see how they compare with the sun. Did it all come from that same basically accreting body, in other words, or was there other factors, migration or other, you know, came from a different source other than the fundamental services? You want to measure the ratio of carbon to nitrogen to oxygen for phosphorus, etc., and is it the same as the sun? Sometimes it isn't. Titan is very different, for example.

The way to do that is to say, OK, in the first half of the atmosphere, it's mainly CO₂. If you can measure the carbon, the CO₂ represents the carbon amount in some extrapolate. On Saturn, for example—sorry—on Uranus, for example, it's a challenge because you can only go down to 10 bar before everything croaks, 10 atmospheres of pressure. You link with a satellite, as you mentioned, trying to get the data back goes to hell in a handbasket. But the problem is on Uranus, for example, the atmosphere isn't well mixed till you get below 20 bar and 30 bar, the higher pressures. Even though you can measure gases, they don't necessarily represent the core elemental ratios. That's true for Saturn, it's true for Venus because we go all the way there, and it's true for Mars. But Mars is impacted by all the escape, and the moon definitely. But the escape process have spoiled all the isotope ratios, if you like. You have to look at rocks that were formed in these liquid river beds four billion years ago, whatever. Sorry. I ran around that question a little bit. [laugh]

ZIERLER: Not at all. You mentioned how things changed under Charles. What about his predecessor, Ed Stone? What was he like in terms of the administrative culture at JPL?

WEBSTER: I know he was extremely highly regarded. He was seen, like Charles, as a friend of scientists. For example, with my Mars instrument, there was a time we were over mass and over budget. To set an example, the call was to kick the TLS off the mission because they didn't want all the other instruments to make the whole mission grow, which it ended up doing anyway. But that wasn't just instruments. There was a call, but Charles saw the importance of the science that TLS could produce. That was the number one thing. Everyone else was ready to get rid of it. Charles saw that methane and the isotopes was so important, and he had advocacy from other scientists. That was a good example. Ed Stone was the same. He was a superb scientist and leader. I remember getting a couple of medals from him [laugh], I think. But, to be honest, in one's earlier career, you're so focused on your work and the research that you are less appreciative of management, and the role that management plays. You tend to see them as standing in your way, or stopping you from writing a proposal, or you don't really understand the big picture till quite later in your career where you can put all the pieces together.

ZIERLER: From Huygens, was it a pretty seamless transition to Mars? Was it obvious what your capabilities were in planetary science?

WEBSTER: I would say from a measurement point of view, yeah. But, again, even with Curiosity, even with all my—I've led 100 balloon—and these are these massive, 200 ft, bigger than the Eiffel Tower balloons, 4–5,000 pound payloads, what the astrophysics do. I've led at least 100 of those and aircraft missions with my instruments PI over decades. But even with all that experience, I was very naïve when it came to flight instruments, mission, planetary mission—

ZIERLER: What are the big differences?

WEBSTER: —space flight. As I said, it's about the practices, the margins, especially, that's on schedule, and cost. We had Tom Gavin and Gentry Lee and others who created this framework centered around system engineering that turned around—and Firouz Naderi was part of that too—that turned around the losses on Mars. Remember, we missed the planet, and crashed and stuff, where you didn't have a good record. But through, again, the names I mentioned, through creating this framework for building flight instruments, and missions, it put this protocol into place that is very demanding on budget and schedule and design. We were used to building an instrument, and flying it. We actually set fire to that plane once, our electronics. It was burning in the pod when it landed. [laugh] In those days, you could fly it, and if it didn't work, you could fix it.

On a planetary mission, you can't do that. It has to work. But centered around that are these massive design principles. Even a connector on an electronics board, it has to have a certain number of empty pins at certain reviews. For a preliminary design review, 30% of your pins have to be unused; a critical design, maybe 10%; a launch, 5%, in case you have to add additional wires. Those small details, all the testing, fly as you test, test as you fly, everything has to be done that way. Then the operating temperature range is large, and the non-operating. Your electronics has to suffer currents that are double, triple what they would be. When the electronics is built, it can withstand voltages that are double what it's designed for, and triple sometimes. Currents too, every component, so unlike your washing machine that can blow a fuse, these things are so robust that very rarely you'll see any electronics failure, for example. Everything has to be tested in thermal vacuum chambers, as you know, for missions. It's very demanding. I learned a lot through that experience. Now with the Venus Mission, I know exactly what's going on. But the number one thing I could say I learned, that's about ownership. You've got to allow people to own their part of it, so you can't micromanage. For us, Division 32, I'm the Project Element Lead, or the PEL they call it. It was a different name for it, for the instrument. But Division 38 are responsible for the build, so they are responsible for building that. I'm involved all the way. I'm involved in calibrations, of course, and requirements, setting requirements, and all that. But just on the Venus, they want to use completely different electronics. I told our system engineer, they have to make that decision. They have to own it. We have to support them. We can't push them in a different direction. I've learned that over the decades that people have to own a piece of the action that they can call their own. That's the only way they come through, and take responsibility and accountability. It works. It's worked. I'm not a micromanager, but I'm definitely in the lab testing everything myself.

ZIERLER: What was the first project that got you involved in Mars research?

WEBSTER: I wouldn't say I was involved in Mars research until we started getting data, and then it was scientific research.

ZIERLER: Where was the data coming from? I was developing the instrument. I was more focused on developing the technique to make the measurements. But because of my scientific lean and publication record—I've had a very good publication—I've always recognized the application of this technique or that is really powerful and needed. But I've always written first author papers on the results, especially in Earth science, and certainly on Mars too. That's always my goal. But I wasn't involved, and I didn't know a lot about Mars when we were even proposing the instrument. I picked it up as I went along because I knew we could measure A, B, C, and I could see how that fit into it. But you don't really understand Mars until you have real data, and you apply it to real models. It's not that there was some particular scientific goal for the Mars program that I wanted to solve. Again, it was a different iterative process. I take great pride in making the first measurements of something, and going for the big picture, the most important measurements. I'm less interested in measuring an isotope ratio to a slightly better precision than it was done 10 years ago. I want to make the first, which is what we've done, and that's what we're trying to do on Venus and Saturn.

ZIERLER: Were you part of Mars Polar Lander from the beginning?

WEBSTER: It was a difficult time because I was going through this crazy, crazy divorce from my first wife. It was totally insane. My postdoc Randy May and I, we were a team with the other engineers who worked on the balloon missions, and the aircraft was getting established too. We were all spread very thin. Randy got involved with Dave Paige, and we had this young student came to work in our lab called Laurie Leshin, for example.

ZIERLER: Ah. [laugh]

WEBSTER: I think, yeah, she was a student of Dave Paige. I think she was a graduate student, maybe. She came, and started learning about the technique in our lab too. Randy took a lot of the leadership on that. I was pretty broken, although I still had a research group of 25 people or whatever to run.

ZIERLER: You were distracted?

WEBSTER: I was distracted, to say the least. But that was probably the first real opportunity. But I'd been on proposals. We're always proposing for Mars. With every proposal, you learn a little bit more, you learn a bit more. You hone it. You say, "Oh, they really want to get oxygen-18." You look at what you can do and then, most important, you have to establish it in the lab. You have to get a cell, line it up. These multi-pass cells were all new at the time. We helped develop them, and put a certain calibration gas, and then show that you had a sigma[?] for noise just for yourself before you could shoot off your big mouth about it. I'm very meticulous about requirements. The requirements for our Venus mission are pages, because I have to specify not just the uncertainty, but is that one sigma, two sigma, when you say, and what's the time? Is it in over five minutes, over one minute, and how much gases are going to be there? We're very careful about signing up to a requirement that we know we can meet, and we can meet with a margin of a minimum factor of two. Otherwise, I won't sign up to it. I have to, in the lab, literally and personally, put that gas in there and say, "Yes, this instrument can measure to that level of precision, therefore, the flight version will, so to speak."

ZIERLER: Do you recall any misgivings or concerns where you could reverse engineer what happened wrong with Mars Polar Lander?

WEBSTER: Mars Polar Lander crashed. But the Curiosity one, yes, the instrument instruments are not perfect, so there are—

ZIERLER: No, but I mean what caused the crash? Do you recall?

WEBSTER: Oh, I'm not involved in that. We were—

ZIERLER: Yeah, that's totally different.

WEBSTER: We were an instrument on there. We were just bummed out in general. But I understand it was to do with jiggly feet, meaning, they had these little micro switches on the lander. I think there were three of them. There could've been four. Somehow, one of them jiggled as it was coming down on the jets, and it sent a closure signal to the software that said, "If I see any one of those feet closed, we're on the ground." It shut off the jets, the descent jet, and then it free-fell and crashed. I believe that's the story. Now they're more careful about knowing when they've touched down. It was a touchdown micro switch, something as simple as that. But on Curiosity, there are things—the instrument work, as I say, it's extreme…it works just like it did when it was delivered. It's unbelievable, the fact that that laser can scan once a second for millions and millions of times, and be in exactly the same place with the same lines, etc. That's the flight project practices and design principles for you. However, there were things that weren't perfect. We hadn't realized till we integrated with SAM and we launched that we had a resistor set wrong on a circuit. Instead of these beautiful Doppler-limited absorption lines, they have a little ring on the side, which is just annoying, and you have to fit it, and it's distracting, as you say. There are always things in hindsight, so we've learned a lot that we can apply to the Venus.

ZIERLER: When Charles Elachi was named director, did that change things at JPL? Did you feel a difference?

WEBSTER: I think people were very excited because he was so accomplished as a scientist at the time. Personally, he was the most wonderful leader you could ever hope to have. He was our Science Division manager. You could walk into his office anytime. He was always in a good mood. He was always excited about everything. He was always very generous. But if he didn't want to do something, he very kindly and diplomatically told you he would think about it as something, but he never lied to you or anything. He made the decisions, obviously, or he wouldn't have become director. He could make the hard decisions. But he was such a great friend of scientists all over the world. Every scientist knows him and loves him. I have to say, I can't imagine or have ever heard a bad word against him, he was so good. He helped me a lot, like, he did save that instrument. It's because somewhere in the back of his—

ZIERLER: For Curiosity, you mean?

WEBSTER: Yes. Somewhere in the back of his mind, he envisioned the success of that. It was a JPL instrument, and it still is. We're the only show in town for that whole instrument technique. He must have foreseen it not just working, and producing good data, but he must have foreseen the future business—the Venus missions, the Saturn missions, Enceladus, the Titan missions—that if we could create this capability, it would have this business capture, which it has now, and Space Station and all the other space applications we're developing. It could be on the next Mars helicopter. He had that foresight, and he had the scientific community he was so richly a part of. Laurie is too, but she has a lot different connections too with her experience at Washington and NASA Goddard and the universities she's worked at. It's a different flavor. But she's certainly an established, highly respected scientist like Charles was.

ZIERLER: With Charles's emphasis on climate science and sustainability and things like that, did that change or magnify your research capabilities for Earth science in the early 2000s?

WEBSTER: I would say, I'm sure it did, certainly. He was a big proponent of remote sensing. He wrote the book on that.

ZIERLER: Right, literally. [laugh]

WEBSTER: He helped with the Joe Waters and the other microwave techniques, MLS, etc., and the MISR and NSCAT, all the different scatterometry. He was obviously in Firouz too for ocean topography and stuff like that. I was very lucky because I believe it was Charles made me director of Microdevices Lab for two years. I've forgotten when that was. I was a group leader, as I said, but I was a section manager for two or three years, so I had a section of all these big-named problem people that I had to deal with. I was very young. That was a difficult time.

But the Microdevices Lab, I believe it was Charles that pushed me to do that. I was program manager for Firouz for all of solar system instruments, all of JPL, all of them. We had the Diviner with Dave Paige. We had a M3 on the moon, and proposing for JUICE, and the Perseverance rover instruments. Then I also became the director of Microdevices Lab. I had three jobs. I had Curiosity, MDL, and the program management, which was a big job too. They were busy times for me. But Charles and Firouz were pivotal in supporting me, if you like, and encouraging. I would look back, and say I've been blessed to have such incredible bosses over the years, right from my PhD days and postdoc days, and JPL certainly too. That's part of the reason I've stayed here too. Don't get me wrong, you don't always feel appreciated at JPL, but there are times when they come through for you, and you feel good about it.

The Excitement of Curiosity Data

ZIERLER: Do you have a clear memory of when Curiosity was starting to send back data—

WEBSTER: Oh, absolutely.

ZIERLER: —and this was really good science? What was that like?

WEBSTER: We were all in the auditorium there, and Laurie was there. In fact, there's a picture where we've all got our arms around each other, the SAM team. We were all the SAM team. All you could see, and I didn't quite get it, but it was like a shadow of the rover. It was the first image sent back, and everybody's clapping. I thought, "OK, I better clap too."

ZIERLER: [laugh]

WEBSTER: I wasn't quite sure what the hell we were looking at, but everyone seemed excited. It's this weird silhouette of a rover on the surface. I remember that very much. But those first few months were very difficult for me in particular because all the science team was at JPL. They're in that auditorium every day to look at the initial results. This is what Perseverance did, and all these big missions. Then they go back to the institutions, and behave a bit better. But those first two months or whatever, they're all there. Of course, we produced isotype ratios for CO_2, and everyone's jumping all over it. "Are you sure you've done this? Have you done that?" By the way, the numbers we came up with for the isotope ratios, to this day, are the same numbers—

ZIERLER: Oh wow.

WEBSTER: —and CO₂. We came up with 46 per mil, which is the published average now. For that, it was awesome. But the methane—oh my gosh—was a nightmare of hostility and frustration. Part of the issue was we have this laser. It scans through the cell to a detector, and we pump it out with turbo pumps. We ingest the Mars air, and we look for the methane absorption. The deeper they are, the more methane. It's a very simple technique, very simple, except the lasers pass through this foreoptics chamber that has reference cells for isotope ratios, onboard calibration, and another optics in it. That reference cell, the O-ring leaked slightly, so they called it Florida Air. We entrained some Earth air with its methane parts per million component in that cell. Even when you pump out your sample cell, you see a little methane spectral very clearly, so you have to subtract that. That became a nightmare for me because everybody wanted to know now, "Well? You said there was methane." The uncertainty was two parts per billion with this direct technique. The enrichment later got us much better measurements. But in those early days, we were just doing direct. The uncertainty was two parts per billion. They only gave us a couple of spectra. Then we had to extend the number of spectra to average and get better. You're learning, and then the subtraction. I remember Gentry Lee stood up, and said, "Who's doing your statistics for you?"

ZIERLER: [laugh]

WEBSTER: Statistics? There's only eight points. But fortunately later, on we got Ken Farley involved. He analyzed it to hell. But in the end, we were fortunate to have him on board because he added credibility to that same number that I didn't, because I was very broad in many areas too. Ken is so amazing, superb, as you know, and meticulous. He added credence to the measurements we were getting, so he helped us. Then he pushed for the enrichment. He was a powerful voice in getting this enrichment going. Then the benefits for that were huge. But those early days were difficult because one day, it looks like there's zero plus or minus two, and then the next day we'd say, "It could be as much as eight." When you're subtracting spectra, the noise, the scatter on the points, so we had to get more points together to lower that standard error. Then people would get up, and say, "A measurement isn't meaningful unless it's five standard deviations," which they were wrong, of course. Then, believe it or not, half these scientists didn't know the difference. A standard deviation, no matter how many times you measure something, it never changes the scatter. But the standard error is what's important. It goes down the more times you measure the standard errors, you divide by the number of samples. That's what we would quote, and people would go, "There's five standard dev…" what the hell are you talking about? [laugh] It became stressful for me because, again, we were getting our first results. The press were all over us. That was the big story, was Mars methane, on Curiosity. I was under a lot of pressure. In the meantime, we had Caltech Professor Grotzinger, the head of Curiosity, before Ashwin.

In the meantime, he's a geologist, so he wanted it to all be about geology. He was actually upset that methane was getting all the attention. [laugh] The first methane paper I wrote for Science, I had the word biological and abiological. Sushil Atreya and all these big names were on it too. I remember Dan McCleese got upset. He said, "You can't use that word." I said, "We're just describing the possibility." "No, no, no."

WEBSTER: It was a tough time as a planetary PI with that real-time pressure on you from the team who were trying to learn it themselves, and were frustrated that you gave them a slightly different answer the day before. It's like this isn't a sign. This isn't a peer-reviewed publication we're talking. From the project itself, it was all about rocks. That's the truth. From the press, the press were—my gosh, you should see. I've got some clippings. They had, "Say it isn't so," and "Curiosity finds no methane, bummer." Even Vanity Fair and all these magazines had it on.

The Question of Methane and Life Beyond Earth

ZIERLER: What would finding methane signify? Why all the built-in hope?

WEBSTER: With methane in the atmosphere, you have the potential that it's produced by biological activity today, present biological activity, the potential. We now realize it can also be produced by inorganic. But with no methane, there's no potential signature. It's a potential. That's why people look at other planets looking for methane too. Certainly, there was a lot of orbiting—so it wasn't just Michael Mumma who used a telescope, and said there's tens of parts per billion methane. There were European—the Italian satellite PFS was in orbit. They said, "We've averaged over six billion spectra, and we have an average of 10 plus or minus five parts per billion," which nobody believed but we had to. Then you look at it, it was all noisy, and everybody said, "It's noisy." The Italian PI would say, "No, no, no, it's patchy."

ZIERLER: [laugh] Patchy.

WEBSTER: He made a big deal at the conference. He said it was patchy, not noisy.

ZIERLER: Chris, would this apply to the potential of there being subterranean life on Mars if there are caves or caverns, water down there? If there was life there, would the methane that they theoretically produce, would that be blocked from coming to the surface to be detectable by the rover?

WEBSTER: We know there is methane trapped in big reservoirs in the ground. It's certain because of the known geological processes before you add bacteria. Just geologically, we know there are big reservoirs of methane, just like on Earth. That's why the idea of micro-seepage is not far-fetched. It's actually quite believable that you would have fissures and cracks. That's why that part of it holds pretty well. But whether all or part of that methane is associated with bacteria is a complete unknown, even if we are ready to believe there are reservoirs of ancient methane there. Then heading towards your habitability in that, I'm much more skeptical than Elon Musk, I guess, [laugh] these ideas of domes and that, if we survive that long, if the human race is still around in 50, 100 years. It's not clear to me either. But on Mars, it's the radiation that's the biggest challenge. That's why caves become important to have some kind of shielding. But in the end, I still have a tough time believing that there are a sufficient number of diversified human beings who would want to be 1 of 100 people living in the first domes. It's hard enough living in New York.

ZIERLER: [laugh]

WEBSTER: You go to a dome, there's only 100 people at the beginning, or 1,000, and you're stuck with them. My thing that's going to be that human nature doesn't like being entrapped, even if it's a large dome, and air conditioned, and whatever else. I don't see that's viable in the long term. I think people would rather live on a dying planet with radioactive waste than they would go to a pristine dome on another planet. You'd have to be pretty focused on prolonging the human race or something, and I don't think people are that magnanimous. I don't know.

ZIERLER: I asked about the transition from Ed Stone to Charles Elachi. What about to Mike Watkins? How did things change under Mike Watkins' directorship?

WEBSTER: Personally, I get on with everyone, by the way. Mike and I, I got on well with Mike. He was actually a very good Science Division manager for me.

ZIERLER: Before he left for Texas and then with his retirement?

WEBSTER: Oh yeah. He was a good division manager, and he was very important on Curiosity. He was the very experienced flight hardware hardnose that you needed. Somebody had to kick ass and bang the table, and Mike was good at that. He wasn't a particularly large person, but he was very intimidating to a lot of people. He has that look about him, as you know. [laugh] He was frustrated with JPL. In fact, he was actually very critical of JPL management at the directorate level. He was openly critical about it, so I'm not telling you anything others would.

WEBSTER: He left to Texas, and we thought that was the end of it, kind of thing. The whole lab was in shock when he was appointed director. But, in hindsight, I would say, the main reason was that they had Perseverance under development.

ZIERLER: They needed him for that?

WEBSTER: They needed a hard-ass, tough director with experience on a major Mars rover, and no one else could do that. He was the right person at the right time. I think that's why.

ZIERLER: Did you contribute to Perseverance at all?

WEBSTER: No, not at all, no; a couple of review panels or something, but no.

ZIERLER: Is that because there was not a laser spectroscopy component to Perseverance?

WEBSTER: That's true. There is a laser Raman SHERLOC instrument. I was involved a little bit in the early days, but that's taken care of.

ZIERLER: Given all the drama about Curiosity and methane measurements, wouldn't it stand to reason that Perseverance could help to address that?

WEBSTER: It would stand to reason, but they have no capability of measuring gases. They shine this laser on a rock, and if it glows at the right wavelengths, they detect organics. The mass spec on Curiosity, the quadrupole mass spec, detected organics already. Many of them are named organic, so we can actually identify them. In its best case—again, I'm being a little unfair here—it's like how many more times do we have to have a new story that says Mars was wet and once had a water-rich past? It's like everyone keeps discovering that every year. It's insane to me. Perseverance probes differences between their landing place and Gale, but the fundamental result is that Mars once had pebbles and rivers flowing. That was established almost from orbit before Curiosity. [laugh] It's amazing that this keeps becoming a big new discovery on Mars.

ZIERLER: If you had opportunity to rebuild the instrument for Curiosity, knowing all of the controversy that would come, would you change anything? Is there a way to make it more bulletproof in terms of what the data tells you?

WEBSTER: We could make it more sensitive, but the truth is we're not limited by sensitivity.

ZIERLER: That's not the issue?

WEBSTER: Even if we could make it so sensitive, it could measure carbon-13, the carbon-13 ratio, as we said, is ambiguous. It doesn't tell you if it's biological or not anyway. You get that with the methane too. But not really, I don't think so.

ZIERLER: The mystery remains?

WEBSTER: Yeah. I would just say that Curiosity detected organics in the soil, a centimeter, in a drill sample. I actually gave an interview with CNN or whatever, but I pointed out that a centimeter below the surface was seeing organics. I said, "Imagine what you might see if you could drill down a meter or two, like the Europeans want to do on ExoMars," or in caves, as you say, or whatever. That would be exciting. But I don't think that question's going to be answered.

ZIERLER: As you already indicated, Mars Sample Return is not useful for this question.

WEBSTER: It's useful for a lot of related questions.

ZIERLER: Are you involved at all with planning Mars Sample Return?

WEBSTER: The only thing is they're going to take these capsules. They're like shotgun shells or whatever. They have to pick up the capsules or D-size battery, whatever. But they said, "Oh, on the way out there, we can fill it with our own capsules," let's call it—I forgot what they call them—"and let's put an instrument in them. Chris, can you make a TLS in one cc that can make measurements. Of course, they're going to put a pressure gauge in the temperature measurements. What the heck does that tell you? But in those small volumes—I said, "You can't do anything that's worth measuring." There's a limit to people who pull out their cell phone and go, "Oh, I want an FTIR smaller than this." It's like, yeah, easy to say. But generally, sometimes you can make things smaller, and maintain science measurement capability, but there is a limit. They were asking me to develop an instrument that had one cc. They said, "You have an additional electronics board this big. What can you do scientifically?" They're very demanding, of course, too. Anyway, they're hoping to have that capability. The Mars helicopter too, that was a great engineering feat, end of story.

ZIERLER: Because it was a proof of demonstration. It wasn't there to do science? It was planned as a technology demonstration.

WEBSTER: It was, and it was great. It was a great achievement. But, again, it's like that has taken every story for the last five years, and will continue to, because people are fascinated with this. The next generation Mars helicopter could carry better instrumentation. It could conceivably fly up to these wet spots, if you want to call them that, and get important measurements. That's the hope. The tech demo was important for the next generation. But I suspect Mars will become those kinds of small CubeSats, micro landers. We're going to go to the little micro networks, nanotechnology, microtech.

ZIERLER: After the enormity of Mars Sample Return, Mars science is going to become smaller?

WEBSTER: Personally, I don't think it can afford to do anything. Curiosity and Perseverance are two $3 billion missions, and Mars Sample Return is $5 to $10 billion.

ZIERLER: Is there also a diminishing return in terms of what these enormous missions can teach us that we don't already know?

WEBSTER: Absolutely, I think so. It's going to be hard for any future mission to build upon what SAM—and, by the way, when I say SAM, I should say Curiosity. They have all kinds of other very important instrumentation. But that was the ultimate chemistry lab, if you like, that went there. You could repeat it, but you wouldn't learn anything that we don't already know because Mars is all about time. It's about billions of years. We've made our measurement here. Making a measurement next to it a few years later, you don't learn anything. The only thing would be to go to a different place.

But we've done that with Perseverance. I see future Mars missions as being small, and the next rover having to wait for significant improvements in measurement and instrumentation. I see that's 10 years away, at least 10 years, before another substantial rover. Now, the Europeans are going to put ExoMars. Yes, it's going to drill, and they'll get some interesting geological results. Ultimately, you've got to find a microfossil or something to really have real definitive proof of life on Mars in the past. Finding a bunch of pebbles and streambeds, that doesn't answer that question. It says, yeah, there was water on Mars. There were rivers. Now, you and I know, with all those ingredients, there should be life, even statistically. But to prove there was life is—

ZIERLER: You might not get it from a few centimeters down?

WEBSTER: You might not either, and it's going to be a difficult challenge.

ZIERLER: Chris, you mentioned it before we hit record, but for the record, when Laurie Leshin came in as director, you were just blown away, as you were telling me—

WEBSTER: Everybody was.

ZIERLER: —of her capabilities. Tell me about that. What was it like when she joined, or rejoined, I should say, JPL as director?

WEBSTER: I think she brought about this air of excitement to the lab, and hope.

ZIERLER: She's contagious in that way?

WEBSTER: Yes. Yeah, she is. But just pure excitement and hope that you rarely feel. And again, I was at a different part of my career, but I would say lab-wide, people were extremely excited, from technicians, engineers, scientists, administrators, managers. People were excited because she had a close history with Southern California, as I mentioned, Dave Paige, and JPL. She's—

ZIERLER: A student of Ed Stolper.

WEBSTER: Yeah, she was, that's correct, at Caltech. The first time we did our evolved gas heating up rocks in SAM, it was TLS data and mass spec data combined, she was the first author of that paper, and that was an extremely big achievement. It was the first time a rock had been heated on another planet. Give her credit, she led that, took the leadership. Scientifically, she's highly respected alone, and then you look at her management positions. She's always been very cordial and very nice to everyone. Now, there are those who would say that she's always been ambitious. I think she may even admit that to you. Her career was more carefully thought out, as far as promotions and her move to Headquarters. I think she was deputy director of Goddard at one time. Those positions, in hindsight, they looked like an incredibly well-crafted—

ZIERLER: [laugh]

WEBSTER: —route to the top, in a sense. Charles had that too. He had that ambition because he had his multiple master's degrees. I don't know.

ZIERLER: How was your science affected by COVID? Did you slow down? Were you able to work from home?

WEBSTER: Oh no, see, I work seven days a week. I'm a maniac. I'm obsessive about science, about everything. I'll go out and party and have a good time, and come home at midnight, and get on my computer, and start calculating stuff. I'm very intense, devoted, especially in your later years too. COVID came along, and it was great to see the freeways empty and all that. But we started working more at home and, to be honest, I think we all got used to it, and we realized, oh my gosh, I can get more done. We actually could, because you spend time at JPL at the coffee bar, and chatting. Especially for scientists now, that changed. I spend much more of my time working at home in my little apartment. It's so convenient and easy and more productive. When I come in, I don't come in to sit in my office. I come in to work in the lab. I come in a day or sometimes two days a week even; not even that. I come in, and I'm doing lab work, and then I go home, analyze it, and you get into that swing of it. See the Venus Mission, it's all online, Saturn, they're all proposal stuff, that's all online. Nobody cares where you are in the world.

ZIERLER: Are you still managing people at this stage in your career?

WEBSTER: Not directly, which is the best type of management. It's where you can affect [laugh]—

No End in Sight for the Passion of Science

ZIERLER: Yeah. You're not writing performance reviews anymore?

WEBSTER: Yeah. A new Project Scientist once came to me and we had a frank talk about the way JPL works. He was somewhat concerned because he didn't have people under him or a budget. But I reminded him he was the most powerful person on that mission. Anything he wanted, he could get; anything he could do. The answer to that is, as you know yourself, that it's not about having formal people that report to you; it's how you can influence others. My position right now, I'm on staff of the Science Division. The head of the Science Division is Shouleh Nikzad. She would be a good person to interview. She came from Microdevices Lab. I knew her there for a time. She's brilliant too, and a wonderful boss for me. But I have nobody who works for me. I don't directly control budgets, but I bring the money in, and I go talk to somebody, and things happen. It's the best job in the world. I'm less reluctant now to take on postdocs and that because of the overhead and the work. I'm more inclined, I tend to mentor younger people, give them advice, nudge them, recommend them for awards. I have Amy Hofmann who works here with John Eiler's group at Caltech. She's my protégé for the Venus-Saturn mission. She's brilliant. She's a mass spec person, which is perfect for this combination technique.

Then I have Sona Hosseini, who was a key speaker at Firouz's funeral. She's a brilliant young Iranian-American who's developing a heterodyne spectrometer, so I help her with her lab work and proposals. I have Lance Christensen, who's leading all these commercial applications mentioned earlier. We have TLSs everywhere now. I just wanted to say it before we end and that is that for me now at 70, and at my stage of my career, I feel really fortunate and good to have contributed what I feel is—I think I had a great career, and a very rich experience, and rich, especially not focusing on one topic. I was able to diversify, and all that, and interact with all these incredible institutions, colleagues, all the rest of it. But right now, I'm hoping my retirement plan is to work and then die. It's that simple. It's a two-part plan. My plan is to—

ZIERLER: There's no off to the fishing boat for you?

WEBSTER: No.

ZIERLER: Nothing like that?

WEBSTER: That'd be so boring. Now work is so exciting. I wake up in the morning still, after all these decades, excited and rushing to get to my computer or to do a calculation I've thought of in my sleep, or whatever else. The work still excites me. It's very detailed, a lot of programs, and plotting, and error budgets, so it's very—what's the word—cerebral, in some way, so that's very nice. But I was going to say that it's all about legacy when you're my age, and you're at that stage of your career. Even though I'm going to work till I die, I'd be lucky if—I mean, you're lucky, as Firouz showed us, if you live for another day, things can change. But I have heart disease and other issues, so I'd be lucky if I get to see that Venus mission at 80, 82, whatever I'll be. But that said, it's all about legacy, so it's about developing the next generation and—

ZIERLER: Enabling the technologies?

WEBSTER: Yeah, exactly, and enabling JPL's leadership. See, all the tunable laser spectrometers for any mission, they're all proposed by us. Goddard gave up on developing them, because the partnership is so good. They realized they're the mass spec leaders in the whole world for flight, from Jupiter Galileo to the Titan Dragonfly. You name all the missions, they're Goddard mass specs. TLS is the JPL thing, if you like, too. The combination is mind-blowing. But it's important for these missions—Saturn, Titan, whatever, Enceladus—all these planetary missions that TLS—I want to die knowing that it's continuing to grow. It's a selfish reason but legacy is very important—

ZIERLER: Not at all if you're thinking about making sure that the science survives.

WEBSTER: Yeah, exactly, that too.

ZIERLER: Chris, for the last part of our talk, I'd like to ask a few retrospective questions. This is just to put it all together. What do we know now as a result of the techniques that you've developed, the science that you've done? What are the big takeaways, both for planet Earth and for other planets?

WEBSTER: That's a big question.

ZIERLER: Absolutely. It's why I save it to the end.

WEBSTER: But I have nearly 200 papers—

ZIERLER: [laugh]

WEBSTER: —that detail all that.

ZIERLER: Yeah, but you can establish a composite.

WEBSTER: I think the most—

ZIERLER: What do we know about—let's start with Earth. What do we now know that we didn't at the beginning of your career?

WEBSTER: Right, and maybe wouldn't, I would say. You mean because of my work—

ZIERLER: Yeah—

WEBSTER: —not in general?

ZIERLER: —or even not you specifically but what you've contributed to.

WEBSTER: Yeah. I would say the most, the highest impact results would be, first of all, establishing the chemistry and the chemical mechanisms of ozone loss, both at the general thinning at midlatitudes, and in particular the polar ozone loss, how the ozone hole is formed, how it was formed, what are the chemical interactions, and thereby establishing the modeling, the correct modeling of that process, and therefore being able to mitigate it into the future, you know, that it is healing slowly. That's all a result of that work, that understanding. That was probably the first one. Then another one would be establishing water isotope ratios for looking at Earth atmosphere cloud formation. We were the first people to measure water isotopes, by the way, in Earth's atmosphere. That was a paper in Science too. We could look at the deuterium-hydrogen ratio in clouds, cous clouds. We could tell if they were lofted up from below, they would look like ocean water, or they grew in place where the deuterium would be very depleted. That paper, we established the formation of cirrus, or we certainly contributed to understanding where cirrus clouds come from, how they formed, simply by this technique, looking at water isotopes in and out of the clouds over Nicaragua, I think it was.

Then on the planetary, it would have to be Curiosity, making the first measurements of the carbon-13 and oxygen-18 isotope ratios in carbon dioxide, the bulk of the atmosphere, and establishing the enrichment of those because of the escape of the lighter, so establishing, confirming, if you like, through detailed measurements that Mars has lost its atmosphere over time. It's consistent with that already established theory, but it's quantitative check marks, a bit like Ken's work on the lifetimes. Then, of course, the methane has just—establishing there appears to be a seasonal cycle to the methane, there appears to be a diurnal variation, and coming up with a feasible explanation of micro-seepage and surface containment that's consistent with the measurements. But there's a lot remaining to establish with the controversy of that whole measurement.

ZIERLER: Chris, what about Caltech as an asset for you, teaching here for a short amount of time, interacting with Caltech professors, how has that been a force multiplier for your research?

WEBSTER: I would say, I think if we, if JPL existed, and Caltech wasn't here, I think that the scientists at JPL would feel very much more isolated and more like, let's say, industrial scientists. What's the word? Applied science, almost. Even though JPL scientists don't—and, again, this is a generality—don't have as much direct interaction with campus, the very existence of it here, and the knowledge that it's here, and the visibility, in other words, everyone knows they've all been here, and so they all know what it's like, we know how famous it is, I would say that is a huge encouragement in the work we do.

ZIERLER: It's almost like it exerts a psychic force on JPL?

WEBSTER: Exactly. It's a psychic and maternal force too. There's that alone. That's one area, and then knowing that you can come down here, and talk to people, and chat with people. But I think there's a feeling that our admiration for Caltech professors isn't always reciprocated for JPL senior scientists. There's an underlying concern, and I think we've seen it in our chief scientists who are often Caltech professors. We have a position called senior research scientist, which through a massive review process and massive references, you have to prove that you are the equivalent of a full-time professor at a major university. That is done through those very processes and established. But we don't always get the feeling that Caltech feels that way, and it's partly because—I'm being very frank here—Caltech professors are aware of their—

ZIERLER: Status?

WEBSTER:—their status, their superb leadership, and they are, they're the best in the world. There's no question about that. They're very aware of that, and they seem more reluctant to bestow that same fortune on JPL scientists. That's just the truth. It's always been a—

ZIERLER: Two-tiered system?

WEBSTER: I don't know if it's two-tiered, but it's blended. There's two tiers that are somehow blended there. I don't think Caltech professors care about it, if they even—

ZIERLER: Who's to say that they're even aware of it?

WEBSTER: Exactly. JPL scientists are aware of it, even if it's undercurrents.

ZIERLER: This is a perception issue?

WEBSTER: Yeah. It's almost like I wouldn't say insecurity is too strong a word. But, yeah, it's like you secretly worry if your parents love you, or something like that.

ZIERLER: [laugh]

WEBSTER: It's that kind of feeling.

ZIERLER: Do you think the fellow designation that we talked about at the beginning of our conversation, does that address that or does that attempt to address it? Is it like the equivalent of a named professorship?

WEBSTER: No, because a lot of the fellows are engineers and not scientists. A lot of them are superb for engineering; some, I think, even administration or management too, or some other related business, and stuff like that. That doesn't address that. The fellow is an unusual position because once you get it, there's no established perk, so to speak, or funding. They do have a mentorship, so there's a tiny amount of money that you can have a junior person charge to, but you can't charge more than 10% of your time. It's something. But the most important thing that comes with it is in your own mind. It's to do with the Caltech Honor Code, the JPL Honor Code. It's to do with once you have that title, you have to set a better example, and you have to be more forgiving. You have to be more accommodating. You have to be more accountable for your actions. All those things go into it. It's such a prestigious appointment that you psychologically take it very seriously, and you act differently. The appointment has more effect on you, and the way you hold it, than it does on other people, I think too.

ZIERLER: Finally, Chris, last question, looking to the future. You already mentioned the goal is to enable the science, to live, to see that you've enabled the science for the next generation. Hopefully that happens in the next 10 years. What's the game plan? How do you ensure that, or how do you maximize the potential that that's actually going to happen?

WEBSTER: That's a tough question. I'm not sure I could answer that easily. It's because science, there's just as much politics in science as there is in politics.

ZIERLER: Of course.

WEBSTER: It's unbelievable.

ZIERLER: Science is a people enterprise, like anything else—

WEBSTER: Exactly. [laugh]

ZIERLER: —for better and worse. [laugh]

WEBSTER: It's quite revealing, though, as you get older and wiser, and you see there's politics in everything, and so you understand why there's so much controversy with climate change or global warming.

ZIERLER: Maybe I can reframe the question like this. What's standing in your way? The science is excellent. It should happen. It's important. That's self-evident. What's standing in the way that those truths, the self-evidence of them, it shouldn't happen on its own? What's the push that needs to happen?

WEBSTER: The push, fortunately, it doesn't rely on me. It relies on the whole planetary community, and they're very good at making that push. But there's a limitation. The realities are—and rightly so—there's a limit on the budget. We talked about Mars Sample Return sucking up all the funds, so the budget and the opportunities. As a mentor, my biggest challenge is you have these young people in planetary science, and somehow you've got to let them understand that if they're one of the lucky few, they might get their instrument on a mission in the next 25 years. My main focus as a mentor is to encourage parallel path science. You've got to be doing lab work, fieldwork, or Earth science, something related, where you're publishing papers every year. At the same time, you cannot just say, "I'm waiting to go to Jupiter."

ZIERLER: That's a needlessly empty career, is what you're saying?

WEBSTER: Exactly. If you're interested in developing or even answering planetary science questions, you've got to either be associated with an ongoing mission or one that's going to get there. But trying to get your instrument, which is how instrument scientists view it, on a mission in 25 years, and then, "Oh, Chris was lucky he got on Curiosity." I've been twice lucky, so I'm double-blessed with the Venus selection. But it does take decades. But the budget is realistic. It has to be. Everything, it's all a balance. It's not something you can complain too much about. NASA get a reasonable budget, and they partition it. But the problem is there's many mouths. The astrophysics and physicists are very vocal, as you know, especially here at Caltech. The Earth scientists too, everybody has a hand in that card game.

ZIERLER: It provides focus for you at this stage in your career though?

WEBSTER: Yeah, it does, but I recognize that things are difficult. They're always more difficult. They're more challenging. Everybody has disappointment in their careers. Everybody has milestones or opportunities lost and opportunities taken. It's a smorgasbord of actions, and that's true for the future too.

ZIERLER: Who knew there'd be so much Shakespeare in planetary science, right? [laugh]

WEBSTER: Exactly. [laugh]

ZIERLER: Chris, I want to thank you so much for doing this. It's been a wonderful conversation.

WEBSTER: Thank you.

[END]