Planetary Radio • Jul 15, 2020

How Perseverance will Search for Life on Mars

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Kenneth williford

Kenneth Williford

Perseverance Deputy Project Scientist and Director of the Jet Propulsion Lab’s Astrobiogeochemistry Lab

Perseverance, NASA’s 2020 rover, leaves for the Red Planet in just days. Deputy project scientist Ken Williford tells us how it will look for signs of past life where there was once a Martian lake. He’ll also take us through his Jet Propulsion Lab facility where scientists are learning how to recognize the evidence of long ago biology here on Earth. Comet NEOWISE is still lighting up the northern hemisphere sky. Bruce Betts knows where to find it. We’ve also got great new prizes for the space trivia contest.

Installing Perseverance's Sample Tubes
Installing Perseverance's Sample Tubes A team of engineers and technicians installing sample tubes into the belly of NASA’s Perseverance rover. These tubes will be used to collect and store samples of Martian soil for future return to Earth.Image: NASA/JPL-Caltech
Perseverance with samples on surface
Perseverance with samples on surface NASA’s Perseverance rover will store rock and soil samples in sealed tubes on the planet’s surface for future missions to retrieve, as seen in this illustration. Future missions must retrieve and return the samples to Earth.Image: NASA/JPL
Diverse exposed surface mineralogy around the Jezero delta
Diverse exposed surface mineralogy around the Jezero delta A preserved river delta in Jezero crater, Mars as imaged by the Mars Reconnaissance Orbiter. The colors denote the presence of different types of materials formed or altered by water.Image: NASA / JPL / JHUAPL / MSSS / Brown University

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What and when was the last flyby encounter of a comet by a NASA spacecraft?

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What do the following have in common? The Venus atmosphere near the surface of the planet, and some coffee decaffeination processes.


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Mat Kaplan: How Perseverance will look for life on Mars, this week on Planetary Radio. Welcome, I'm Mat Kaplan of the Planetary Society, with more of the human adventure across our solar system and beyond. Strictly speaking, I should have said how Perseverance will look for past life on the red planet. There's so much more to this story though, including how the study of ancient life on Earth is preparing us for the quest on Mars. Ken Williford is deputy project scientist for the rover mission that is now set to launch on or shortly after July 30th. He'll take us inside Perseverance and into his fantastic JPL lab. We've also got two contests to finish this week, along with your opportunity to win one of two ultra-cool new Planetary Society T-shirts. Bruce Betts will also tell you how to see Comet NEOWISE.

Mat Kaplan: With so much going on, we'll make this week's dip into The Downlink very brief. Want to see how astronauts on the International Space Station caught the comet? That's the lead image in the July 9 edition. It's followed by headlines about the ongoing troubles of the mole on the Mars InSight Lander, the next road trip for the Curiosity rover in Mars's Gale Crater, and new findings of more metal on the moon than was thought to reside there. You'll find lots of links to learn more about these and many other stories at Here's the word of the week, Astrobiogeochemistry. More, if you want to save time, ABC. It's the field and the opportunity that brought Ken Williford to the Jet Propulsion Lab a few years ago, and it helped prepare him to help lead all science activity that will be conducted by Perseverance.

Mat Kaplan: That science will include the collection of samples for eventual return to earthly laboratories, even as the big rover conducts its own analysis. As you'll hear from Ken, Perseverance also carries instruments and experiments that will bring humans one step closer to visiting the red planet themselves. Get ready for an absolutely fascinating exploration of this mission and the search for ancient life that it will undertake. Ken and I talked online a few days ago.

Mat Kaplan: Ken, it is an honor to welcome you to Planetary Radio, especially now when we are days, or, at most, a couple of weeks away from the launch of Perseverance toward the red planet. Thanks for joining us.

Ken Williford: Yeah, it's good to be with you, Mat. It is a very exciting time.

Mat Kaplan: Let's start with the obvious, what's the current status of the spacecraft, and that Atlas V rocket that is supposed to get it on its way toward Mars? I mean, the delay was from the rocket, right? Nothing to do with Perseverance.

Ken Williford: That's right. There were a few issues with, we call it the launch vehicle, with the Atlas V rocket and associated equipment, but everything I've heard so far suggests that the issues are under control and everything has a solution and we're on track for a July 30th launch. I just saw a little bit ago someone sent me a picture in an email from down in Cape Canaveral nighttime shot of our spacecraft, all buttoned up inside the fairing, being rolled out to the pad and ready to go up on top of that big rocket.

Mat Kaplan: Does this mean that RTG, that hot radioactive package, is it already installed in Perseverance so it's ready to power up when the time comes?

Ken Williford: Actually, that's a good question. I believe it is not. And I can't tell you actually all the details just because I don't know of the exact step by step sequence to getting everything ready for launch. But I did hear today, our project manager talking about a dress rehearsal with the RTG. And so, I believe that must either be done before they lift it up and put it on the rocket, or even after it's already up there, they put the RTG in last.

Mat Kaplan: If I remember correctly, with Curiosity, it was not installed until very shortly before launch. So, I bet you're right about that. Before we talk more about Perseverance and what its job will be on Mars, I noted that you lead a lab at JPL that I'm embarrassed to say I'd never heard of, until I started to do research for this conversation, even though its name is as simple as ABC. What is the Astrobiogeochemistry or abcLab that you lead at the Jet Propulsion Lab?

Ken Williford: Yeah, well, you have to run in certain circles to have heard of the abcLab, I guess. But, we do have a lot of collaborators around the world, but they tend to be organic and isotope geochemists doing similar kinds of work. But our mission really, in the lab at JPL, is to study the processes of formation, preservation, and then the detection of signs of life and planetary evolution in geologic materials, if that sounds like a mission statement. It is, and it aligns... It's what I came to JPL to do originally, now going on about almost eight years ago, and it was always with an eye towards supporting Mars sample return, and what we call typically, return sample science. And so, that's the type of science you do on Earth, eventually, with samples that are returned from other worlds.

Ken Williford: In this case, the work in my lab is very specifically dedicated to preparing us to work on samples from Mars, that we hope one day will come back. And we're most interested in looking for signs of life. In this case, it's ancient life in generally very old rocks, rocks that are most typically in my lab hundreds of millions of years to several billion years old. And some of them are the oldest sedimentary rocks that we have on Earth. And we're studying some of the earliest Earth environments, some of the earliest evidence for life on Earth. But then, another theme is looking at the interactions of living organisms on planet Earth and the nonliving systems, the geologic systems, looking at the coevolution of those things, especially at times of great change.

Ken Williford: So, we're interested in studying mass extinction events and other things like that in the lab. But generally, everything we do is with an eye toward refining the techniques, we call them the interpretive contexts, or just building the scientific context necessary to understand all the great data that we hope to extract from samples that come back from Mars one day.

Mat Kaplan: When you look back at the most ancient era of life on Earth, when life began, or, at least, not long after, my understanding is, you don't see a lot of fossils. Are we learning to detect the past presence of life in other ways, which are probably going to be useful on Mars, or we hope will be?

Ken Williford: Yeah, that's right. There are fossils, I would say, extending back to as far as the good, I would say conclusive record of life extends on Earth, which, in my personal view, is to about three and a half billion years ago. There are signs of life that have been reported in rocks older than that, back to about 3.8 billion years ago or potentially older, depending who you believe. Everything older than about three and a half billion years is generally quite controversial and plagued by a lot of ambiguity, because the rocks have been so heavily altered at that age by the forces of tectonics on Earth. But we have this record starting at about 3.5 billion years ago, expressed best in Western Australia, a place called the Pilbara, but also some places in South Africa.

Ken Williford: We do, in fact, see fossils all the way back, and they are not the kinds of fossils that most people are used to thinking about, certainly nothing like a dinosaur bone, but not even a trilobite, if you're familiar with that, or any kind of clam fossil, this is a long time before the evolution of animals and even plants. This was a time, and in fact, most of Earth history, the vast majority of Earth history, really, the entire planet was populated only by microscopic microorganisms. Now, sometimes those microscopic organisms, these are bacteria, and similar organisms called archaea, single-celled organisms that sometimes group together in colonies.

Ken Williford: Most people would be used to seeing pond scum as bright green stuff at the edge of a pond, and that's exactly the kind of stuff we see preserved in rocks, in other fossil versions of pond scum, are what we see preserved as the earliest best evidence for life on Earth in these three-and-a-half-billion-year-old rocks in the Pilbara in Western Australia. And we call these things stromatolites. Imagine a gooey layer of pond scum, and then you have some mud and silt and sand flowing in covering that gooey layer, getting trapped in that gooey layer of bacteria, and then the bacteria grow up and over that layer of mud and sand, and the whole process repeats over and over and over again, until you build up this wrinkly-layered structure, that then gets buried and turned into a fossil. A long time later, some geologist comes around and digs it up.

Ken Williford: And that's the kind of thing, honestly, that's sort of the holy grail of what got our eyes peeled for with Mars 2020. That's the kind of thing that could be detectable with our rover. And we are certainly going to explore the environments in Jezero Crater, where, if that ancient lake was inhabited, and if it was capable of producing pond scum, we are going to go to the rocks, particularly on the edge of that lake, where that stuff would have concentrated and fossilized, if that lake was inhabited. So, that's one of the types of things we're most excited about March 2020.

Mat Kaplan: I want to mention that I watched most of your fascinating 2017 von Karman lecture at JPL about Perseverance, but in that, you had an image of a section of stromatolites. We'll link to that lecture, of course, from this week's show page at How big a dance will you do if Perseverance finds stromatolite in Jezero Crater?

Ken Williford: It will be quite a dance. I'm picturing the Michael Jackson Thriller video or Saturday Night Fever combined on steroids. That would be a very happy day, if we see anything that looks like those stromatolites in Australia. Of course, that said, when the dancing subsides, we will all get to the task of making sure we can confirm a shape like that is actually something important and was actually produced by life. And it's a very tall order. So, even with the oldest evidence for life on Earth, the scientific community finds it challenging to come to strong agreement. When any new paper is published, pushing back the record of life and putting a case together that life emerged maybe early than we thought, it's hard to get agreement.

Ken Williford: And usually, it takes years, sometimes decades, where many different scientists have to go and look at the same rocks with all sorts of different techniques. Sometimes the story changes over the years as we learn more in different things, and even more so, as you can imagine, for Mars. So, it's such an extraordinary claim, it would be such an extraordinary claim that life once existed on Mars, that it will certainly require extraordinary evidence. And that's why we think it'll be critical to get those samples back to analyze them, no matter what we see really on the surface of Mars with 2020.

Mat Kaplan: Well, thank you for paraphrasing that quote from our co-founder, Carl Sagan. You have made me think back to a time when I did a little dance, not too many years ago, I got to hold a tiny fragment of that famous piece of Mars known as Allan Hills 84001. I remember when the announcement came, I was so thrilled that when NASA announced that microfossils had been found in this meteorite from Mars, I had to pull my car over to the side of the road and get out and do a little dance. Wasn't long before that conclusion was called into doubt. Good science can be so disappointing sometimes. What have we learned since then? How will we avoid getting it wrong this time? Or, did we even get it wrong that time?

Ken Williford: Well, I think it's a great example, the Allan Hills meteorite, and in a sense, I might not be where I am, having made it through grad school, funded by the NASA Astrobiology Institute largely, working on a Mars rover mission at JPL, had it not been for that work on Allan Hills. As much as we point to it as an example of jumping to conclusions or maybe getting something wrong, I really encourage people to go back to that paper, or go to the paper, the McKay et al., 1996 paper, that was the original report, and there's a lot of good work to be found in that paper. And often, that study is used, I think, oversimplified, and we look at those images that are pretty famous of these worm-shaped features in the rock.

Ken Williford: But the study was about much more than that, and it was actually, I think, a pretty nice template for the kind of approach that we take today, where we look for combinations of lifelike shapes. Sometimes in geology, we call them textures, or morphologies, but basically, lifelike shapes in a rock, that are combined with or co-occur with in space, lifelike compositions. So, chemical compositions. These can be the elements that are the chemical elements that are important to biology. There's this super important shortlist that we often call CHNOPS, C-H-N-O-P-S, but there are certainly quite a few other elements that are important to life. And then, biologically important minerals. The seashells around us are made of calcite or aragonite, our teeth and bones have apatite, hydroxyapatite, phosphate minerals, carbonate minerals, sulfide minerals, iron oxides, and so forth, minerals that tend to hang out in the presence of life.

Ken Williford: They do so often because they represent metabolic substrates. All animals, ourselves included, use one very specific type of metabolism, aerobic respiration, where we take in organic matter, breathe in oxygen and harness that energy, that very energetic metabolism. But basically, any chemical reaction that you can imagine, that involves what we call redox chemistry, oxidation reduction chemistry, and rusting is a great example of that, turning iron into iron oxide, any chemical reaction like that, there's some microbe living off of it. So, there are so many different types of metabolisms, and those different metabolisms, when they're expressed in the environment, lead to the precipitation of different minerals that can be preserved for billions of years.

Ken Williford: So, that's important, we look for those, and then we look for lifelike compositions in terms of molecules, the organic molecules. All life that we know of is carbon-based, we'll often hear about, "Yeah, but what about silicon-based life or other..." And there are all kinds of possibilities, but when we talk about looking for ancient life on Mars, where we're looking, first, at least, for life mostly as we know it. So, for carbon-based life that would be built of organic molecules and use liquid water. And so, going back to that original Allan Hill study, if you take a look at that paper again, you'll find that they were using a bunch of different cutting edge techniques to look at those concentrations of elements and minerals, and in some cases, molecules, that co-occurred in shapes that were interesting.

Ken Williford: So, it's actually not all that different, the approach we use today. Now, that said, you're right, that I think the consensus view is that the interpretation that that evidence that represents evidence of ancient life on Mars is not really there in the scientific community today, but it launched that study, and similar things around the same time launched a whole new conversation about astrobiology and the search for life on other planets. The NASA Astrobiology Institute was founded not long after that. And again, like I said, that paid for a lot of my PhD and put me where I am today. So, I certainly look at that study as really critical step along the way to where we are today.

Mat Kaplan: It just reminds me that even when science may have a disappointing result, it leads to, often leads to terrific progress. You're talking about that paper from 24 years ago. You look back 44 years to Viking, and its first attempt to find biological activity on the red planet. We have learned an awful lot since then, right? I mean, including about the sorts of, yes, life as we know it, but still, extreme life as we know it, those so-called extremophiles.

Ken Williford: That's right. Clearly, Viking, and you mentioned Carl Sagan earlier, those heady days around the time that I was born actually. And Carl Sagan has long been one of my scientific heroes, and I remember watching the entire Cosmos series in high school, and just being so inspired. Yeah, Viking was a huge step. But again, as you said, we have come a long way, and so, I often say that Mars 2020, with our core objective to directly seek the signs of life, is doing something in astrobiology that I think has not been done this seriously since Viking, really. So, after Viking with largely negative results from the biology experiment, you and your audience will be aware that there was one part of the biology experiment that produced some ambiguous results that even some folks today think might have pointed to life. But again, the consensus is not there, and generally, people think the biology results from Viking were negative.

Ken Williford: There was a real low in Martian surface science after that, until Pathfinder and the era that we're in now of the Mars rovers. But there was this stepwise approach, starting with follow the water with MER, to MSL, which so brilliantly took a more nuanced approach to habitability, finding evidence for habitable environments, that went beyond the binary presence or absence of water. And again, they did that beautifully, to now what we're doing, which will follow in those footsteps, and of course, we'll be following the water all the way to this lake, ancient lake in Jezero Crater, we'll be using a lot of what we've learned from the approach that MSL and Curiosity took to understand the habitability of that environment, but then we'll take that next logical step, which is to directly seek the science of ancient life, in a way that I don't feel was, at least, as explicitly done by past missions.

Ken Williford: Now, that links us to Viking. But of course, we have to understand there's a very important distinction between our mission and the Viking mission, and that is that Viking was primarily looking for evidence of extant life. So, those biology experiments were looking for life that was alive at that time or had recently deceased in the Martian soil or the Martian regolith. Our mission is to look for signs of life in rocks that are very, very old, in rocks that are older than the ones that I talked about earlier, where the oldest evidence for life on earth is. So, these are between three and four billion years old, closer to four billion years old. These are very old rocks deposited at a time when Mars was much more Earth-like than it is today, and where we have excellent geologic evidence that there was abundant liquid water on the surface, which tells us that the atmosphere must have been very different, much thicker. We believe there was probably a magnetic field, and that the planet was much more active and dynamic than it is today.

Ken Williford: And so, we're taking the approach of looking through that window which is three and a half billion years old, to see if we can determine whether life existed back at that time.

Mat Kaplan: Though, I imagine, you and the rest of the science team wouldn't complain if one of those cores that you'll be pulling up, if something tiny crawled out of it, within view of one of the cameras on Perseverance.

Ken Williford: True, true enough. That would be exciting indeed. And while I say that's clearly not part of our mission is to... If you wanted to design a mission to look for extant life on Mars, and it's a great thing to think about, it's certainly not impossible that life currently exists on Mars, but it's almost certainly, if it does, it's almost certainly in the deep subsurface. And so, it's a very different set of instruments and set of technologies that you would send to Mars, if that was your goal. And so, that is not our goal. But that said, when the samples come back someday, clearly, one of the most important things that will happen will be to look for any evidence of extended life that they might contain. And so, no doubt, there will be work done to determine whether there is evidence of extant life in our samples, it's just that our strategic approach is not to optimize our capability to answer that question.

Ken Williford: This question is about, how did Mars evolve as a planet? What can we learn about our solar system's evolution broadly, the evolution of terrestrial planets broadly? And then, the broader question, was Mars ever inhabited?

Mat Kaplan: Ken Williford has much more to share with us as we begin the countdown to the Perseverance Mars rover mission. I'll be back with him after this break. I want to come back to your lab, or rather, your lab's website. And I hope that people will take a look at it. It's fascinating. I especially enjoy the little tour of your lab equipment. You've got a lot of cool toys, by the way. What in the world or what in any world is a CEM Mars6 microwave-assisted extraction digestion system?

Ken Williford: Right, yeah. Okay. It's interesting that you found yourself concentrating on that. Yeah, we are extremely fortunate to have some very fun toys to play with. I hesitate to call them toys, lest our funders get angry with us. But certainly, we relate to them just as an excited kid would on Christmas morning when we get a new one or we get an upgrade. It's just as exciting as I remember the newest transformer being when I was a kid.

Mat Kaplan: There you go.

Ken Williford: So, the CEM extractor, the Mars6 device that you talked about, this is a device that's basically a very fancy microwave. This is a microwave-assisted extraction device. And we primarily use it to extract organic molecules from rocks. We will take a rock sample from the field, it is, say, two-billion-year-old mud stone from an ancient Lake, let's say, and we believe it has organic matter in it, and that organic matter consists of the dead bodies of the bacteria that were living in the surface of that lake and fell to the bottom. And then the molecules that they were made of, some of them polymerize into a gooey substance we call kerogen, but some of them remain as something like oil, we would call it in my lab, bitumen, but it's basically oil. We study both of those organic substances, kerogen and bitumen.

Ken Williford: The bitumen often has a lot of great information in it about the original organisms that produced it. So, we use an organic solvent basically, imagine something like alcohol, we just pour, it's really methanol and dichloromethane, into a Teflon tube and seal it up. And inside that tube is also several grams of rock powder of that mud stone, and then we heat it up in the microwave under pressure, and that organic solvent extracts the bitumen, gets that oil into it, and then we filter the whole thing, and now we have our solvent in a vessel. We evaporate away the solvent, leaving behind this sort of oily film, and then we do some chemistry on that and we eventually put it into our GCMS or a gas chromatograph mass spectrometer, which tells us about its molecular composition.

Ken Williford: So, we look at the structure of the individual molecules that make up that organic matter, many interesting things are preserved. Some of the typical things we call steranes and hopanes, and these are molecules that are produced. They sit inside the cell membranes of eukaryotes like ourselves. Algae and plants and animals, inside every cell membrane, they have these molecules called steranes. We're familiar with cholesterol, that's an example of this, and it regulates membrane rigidity. And so, these little membrane building blocks, basically are stripped down to their basic organic skeletons, their hydrocarbon skeletons, and then they can be preserved for billions of years. And then we can measure them in the lab and determine that, "Hey, look, there was some kind of algae here living in this lake," and we make other measurements on those molecules and learn more and more about what types of life was living in those different environments and what sorts of metabolisms they were using.

Ken Williford: And also, you can extract information about what the planet was doing at that time. If you, say, measure the same thing through a time sequence that's preserved in a long drill core, for example, we can measure the isotopic composition of different molecules and learn something about how the ocean and atmosphere were behaving over time.

Mat Kaplan: It really is utterly fascinating. You make me want to visit and look over the shoulder, your shoulder, shoulder of your colleagues in the lab and watch as this works. But, I mean, you'll see where I'm going with this, because you have all these wonderful machines and a fair number of human hands to make them all do their work properly, you don't have that luxury on Perseverance. Now, the suite of instruments that it carries is simply awesome. But, I mean, if you were to think about what Perseverance is capable of doing on its own, I don't even know if it's fair to ask this, but what percentage of the capabilities of labs back here on earth like your own, are going to be carried by Perseverance to the surface of Mars? I expect pretty small.

Ken Williford: Yeah, that's right. I mean, I certainly couldn't put a percentage number on it, but I think it's totally fair to say that it's a tiny, tiny fraction of the full capabilities of the laboratories of planet Earth. I mean, there are so many things we can do here on Earth, when we don't have to worry about the mass and volume constraints in the harsh environments of space and of the surface of Mars where the temperature swings are enormous and where it's impossible to go and repair these things. I mean, think of a synchrotron, one of the types of instruments that we like best to study the record of ancient life on Earth and plenty of other things, involves putting some type of microscope or spectrometer at the end of a beam line, that itself is the product of acceleration of electrons and production of X-rays in a ring that's the size of a city block or more.

Ken Williford: And so, this synchrotron radiation allows us with different analytical techniques to get an extraordinarily high spatial resolution and signal to noise that we could not otherwise achieve. Now, there's no way, in fact, I hate to say never this or never that, but in fact, I will say, we will never fly a synchrotron, at least in this form that I'm describing, because you'd never do that. If you were able to do that, you would sooner build a synchrotron on Mars than to fly it there, right? Now, of course, it's possible that we could find some radically new technology that would allow us to do the same thing in a smaller package, but we don't have that yet. And even then, just by definition, anything you send to another planet, you're always going to be able to get more, have more diverse capabilities if you bring a sample back to the scientific home of humanity, which is planet Earth.

Ken Williford: So, as you said, yeah, there are extraordinary capabilities that represent pretty major advances in interplanetary science on Perseverance, relative to prior missions. It's often asked, do we have to make major sacrifices in instrumentation to do what we're doing to move Mars sample return forward? And it's certainly true that the space that on the Curiosity rover, that is taken up by the SAM and CheMin instruments, those large spaces inside the front of the rover, where you have these extremely capable analytical laboratories, that space on Perseverance is taken up by what we call the adaptive caching assembly. And it's this sort of robot within a robot that looks like a little bottling plant, and it stores the sample tubes and it processes the sample tubes et cetera.

Ken Williford: But it's also true that out on the end of the arm, we have two very advanced new instrument platforms called SHERLOC and PIXL. And these are both spatially resolved instruments of a type that we have never had on a previous space mission. These things both are analogs to instruments that we use, like instruments we might find on a synchrotron or in labs back on Earth, where we can simultaneously extract that spatial information and the compositional information. So, where at the same time, we're looking for lifelike shapes and lifelike compositions. And both instruments raster or move a beam about the diameter of a human hair over an area about the size of a postage stamp, and they create a map of chemical composition.

Ken Williford: And so, you're now resolving spatial information in the compositional heterogeneity that we were not otherwise able to do in past missions. So, whereas the APXS instrument on the Curiosity rover averages the elemental composition over about, say, a square centimeter, PIXL will map that elemental composition over about the same area. So, it's a big advance.

Mat Kaplan: It actually creates an image, what is the advantage of having that spatial revolution rather than, as you said, just averaging out what the radioactive activity finds?

Ken Williford: We will often talk about in the scientific community and we deal with it in my lab, the difference between what we call bulk analysis or spatially resolved analysis. And they absolutely both have their strengths. Bulk analysis is often cheaper and much faster, and you can get a higher throughput measuring those average compositions. And sometimes you actually want to know the average composition, because it allows you to not be biased by this or that thing. You really just want to average over a larger area for certain questions. But spatially resolved analysis, which is almost always technologically more difficult in labs back on Earth, sometimes more expensive to do, and requires more careful sample preparation often, so, it can be slower, but the amount of information, the information density is so much larger in this case.

Ken Williford: And the key thing here is spatially resolved analysis like we will achieve with PIXL and SHERLOC on Perseverance, allows us to simultaneously look for lifelike shapes and lifelike compositions. So, it's not just, do we see a composition that indicates life? It's, is that composition that indicates life, is it arranged in a shape that itself indicates life? Another way to say is we're looking for spatially correlated compositional heterogeneity. Some folks say life tends to be clumpy, it has little bits of this over here and little bits of that over there. So, those are the types of things we're looking for.

Mat Kaplan: In your von Karman lecture, you pointed out, as you zoomed in on a bit of stromatolite, a little wave view, a little bit of filament, and you said, this is the kind of thing that gets people like you excited.

Ken Williford: That's right. Yeah. And that is something that I'm not sure in that case it is a fossil microbial cell, but it looks very much like what we call microfossils, which, in younger rocks, microfossils can include little protists like foraminifera and little single-celled animal-like things. In the much older rocks that certainly that will study on Mars and the much older rocks on Earth, these microfossils are even smaller, and these are individual fossilized bacterial cells. And so, they're often tiny little spheres or filaments, that are one to 10, say, micrometers in diameter. So, very, very, very small. Smaller, in fact, than anything we can resolve with any instrument on Perseverance.

Ken Williford: And so, in order to see these things, not only are they smaller than what we can resolve with the instruments that have ever flown, by the way, on any space mission, they require some very careful sample preparation. And the image I was showing you there or showing in the lecture, was of what we would call a petrographic section. It's where we cut a piece of rock, basically glue it to a glass slide, and then cut away as much of it as we can, and then grind it down until it's thinner than a sheet of paper, and then polish it to a mirror finish, so we can shine light through it and see these little features that are inside of it. So, those are the types of techniques we'll be able to do with the samples when they come back from Mars, and it opens up many new analytical possibilities.

Mat Kaplan: And again, I'll recommend that listeners check out that lecture that you delivered about three years ago. It's a great additional background to all of this, with the advantage of your great slides. While we're talking about images, Jim Bell was my guest a couple of weeks ago, we talked about how his team's Mastcam-Z will integrate with the other instruments carried by Perseverance, some of what you've been talking about. How important is that imaging on a bigger scale, the kind of stuff that Mastcam-Z can do, in the search for past life on Mars that Perseverance will be taking on?

Ken Williford: It's absolutely critical. I mean, it's just absolutely fundamental to what we're doing. And the Mars rovers are often described as robotic geologists. More than anything, the Mastcam on Curiosity and Mastcam-Z on Perseverance are like the eyes of that geologist. I mean, they really are a pair, a stereoscopic pair of imagers just like our eyes, about six feet off the ground, like a fairly tall geologist cruising across the surface, looking around and doing that most basic activity that a geologist does in the field, which is to look at the shapes, the colors, and the textures, and the structures that she sees around her, to understand the basic processes of formation and alteration that led to those rocks in the exploration area.

Ken Williford: So, they really are our first weapon there as we explore our environment.

Mat Kaplan: Everything that you've been talking about just is more evidence of what a complicated machine this rover is. You mentioned that sample handling system, which is just a mechanical marvel. I mean, to me, it seems more like robots within robots, within a robot, but one more level of complication. Do you ever worry about all those moving parts in that harsh environment?

Ken Williford: Yeah, you're right, it absolutely, it's robots all the way down, right? A robot within a robot, within a robot. And to say nothing about the follow-on missions, I mean, it's a very similar situation there, just the number of robots involved boggles the mind. But I try not to worry about that. There are certain things that are outside of my control, which is nearly everything. And I just don't walk down that path of worry, in that case, instead, I think about my colleagues, just incredibly talented engineers at JPL and all the other organizations that have supported us to put this thing together and to get it into space. It's been really a highlight of my career to work with the people who are so creative to come up with these designs, but then to make them happen.

Ken Williford: I mean, we have the sort of key challenge or key benefit from another point of view of working at JPL is navigating the science engineering language boundary. It often feels like, we come from different countries, and it can be frustrating at times. But the beauty of the engineers is they actually get it done. The joke is the scientists are always trying to break it and make it do more than it can, or they always want more, and the engineers are just trying to hold us back. Whereas we dream up every possibility in the realm of science and come up with all the fun stories, but the engineers make it work.

Ken Williford: I've learned so many times during my experience on this mission about the kinds of sacrifices that need to be made and you don't always get everything that you want, but it's in the interest of getting something and making it work and solving a problem that it's just absurdly hard, if you really think about it, what we're trying to do here. And so, my hat goes off to all of them and I try not to worry.

Mat Kaplan: It does seem like you guys on the science team, you discover the miracles and they build them.

Ken Williford: That's right. Yeah, we need each other, for sure.

Mat Kaplan: Before we leave Perseverance, there are two or three other instruments on that rover, which may not be as directly involved in this search for past life, but they do seem to pave the way for us delicate humans to follow the robots to Mars. Can you mention a little bit about that role of Perseverance and how it will be helping to make it a safe place for us men and women?

Ken Williford: Yeah, absolutely. I mean, I personally think that's a very important part of what we're doing. I'm a huge fan of human spaceflight and I'm very inspired by the idea of one day, a human being flying to Mars and standing on the surface, picking up a handful of Martian regolith and grabbing a few rocks and bringing them back to the ship and flying back to Earth to tell us all what that felt like. I mean, that idea really inspires me, and I know it inspires a lot of people in this country and in the world. And so, I look forward to when we can one day see that happen. Some of the things as you said, some of the things we're doing on Mars 2020 are very directly related to that. So, we have the meta instrument contributed from Spain, which is a weather station. Measuring the weather conditions is obviously relevant to future human explorers.

Ken Williford: We have the MOXIE instrument, which converts carbon dioxide, which is abundant in the Martian atmosphere, into oxygen, which is very rare at Mars, in the atmosphere, anyway, but would be vital to human explorers. Obviously, human explorers could breathe oxygen, but a critical piece of getting humans home safely is having an oxidizer for the fuel in the rocket that will get them off the planet surface and back home. And all the better, so much the better if they don't have to bring all that oxygen with them from Earth, and can have it made for them on the surface. And so, that's what MOXIE does is to demonstrate on a small scale, something that can be scaled up later to support human spaceflight. And then RIMFAX is an instrument that's contributed by Norway, and it's a ground penetrating radar.

Ken Williford: This technology has been used in the past in orbit, and currently in orbit around Mars, but never on the surface. We plan to use RIMFAX mostly to look at geologic structures in the subsurface. But one application for ground penetrating radar in the future could be to look for ice or water in the subsurface that human explorers could use. So, those are the specific things that we're doing, but in a broader sense, everything we learn about Mars, prepares us better, I would say, to send humans there and get them home safely.

Mat Kaplan: It is all thrilling. We are all looking forward with such excitement, enthusiasm to that launch. And then, out there in February of 2021, those seven minutes of terror that we experienced with Curiosity, where are you going to be when Perseverance makes that descent down to the surface?

Ken Williford: Yeah, well, it's an interesting question. Certainly, I will be either at JPL or very close to JPL. I imagine I'll either be on lab, we call it at JPL, and I really hope there's a way for us to do that safely, to be there together as a team. But, as we all know, it's such a strange time in the world right now with the coronavirus, and so, it can be hard to get those groups of people together in a small room that we're all familiar with, jumping up and down and yelling and screaming with joy at a successful landing. I don't know what it's going to look like, honestly. And it may look very different than that. And so, I might be at home with my family watching this on the computer, and that'll be okay, too.

Ken Williford: No matter what, we're going to be together in spirit, at least, and I'm definitely going to be connected immediately. I'm sure I'll be texting with my best friends on the mission and in phone calls, and at the very least, celebrating what I hope and expect is just going to be another one of those great days where we can all be proud of what we've done together.

Mat Kaplan: Well, I'm going to share that hope with you, and I'm going to go beyond and hope that we are back in a big room full of people, thousands of us who watched Curiosity make that dissent, and we were jumping up and down and cheering. I'll only say, this time, let's hope it's a big room full of vaccinated people. But one way or another, we'll be following along with you, Ken. I got just one other question for you, and it was obvious from your von Karman lecture, I think it's obvious from this conversation, you clearly enjoy sharing what our boss, the Science Guy, calls the passion, beauty, and joy, the PB&J of science. Is this as important to you as it sounds like?

Ken Williford: Absolutely. Yeah. I mean, I was just talking with some of my colleagues earlier about exactly this question, and I can tell you that, for myself, the opportunity to do this kind of thing and to talk about science with other scientists, but especially with non-scientists, is as important to me as anything. I love so much being able to talk about these things and share ideas and communicate. So, I appreciate this opportunity and it's great. I look forward to many more.

Mat Kaplan: Ken, it really has been a great pleasure. Thank you so much for joining us here on Planetary Radio. Ad astra, ad Aries, looking forward to all that great science that Perseverance will start doing in February of next year.

Ken Williford: Yeah, the pleasure is mine. Thank you so much, Mat, and look forward to talking to you about it again when we're on the surface, maybe.

Mat Kaplan: Oh, please count on that. I hope you'll be back, and maybe before then. That's Ken Williford, he serves as the Deputy Project Scientist for the NASA Mars 2020 mission, Mars 2020 rover that we now know as Perseverance. He is also the Director of the JPL Astrobiogeochemistry Laboratory. Bruce Betts joins me next.

Bill Nye: Greetings, Bill Nye here, CEO of the Planetary Society. Even with everything going on in our world right now, I know that a positive future is ahead of us. Space exploration is an inherently optimistic enterprise. An active space program raises expectations and fosters collective hope. As part of the Planetary Society team, you can help kickstart the most exciting time for U.S. space exploration since the moon landings. With the upcoming election only months away, our time to act is now. You can make a gift to support our work. Visit, your financial contribution will help us tell the next administration and every member of Congress, how the U.S. space program benefits their constituents and the world.

Bill Nye: Then you can sign the petitions to President Trump and Presumptive Nominee Biden, and let them know that you vote for space exploration. Go to today. Thank you. Let's change the world.

Mat Kaplan: Time for What's Up on Planetary Radio. It's the special extended edition of Planetary Radio. We're answering two, count them, two contests today.

Bruce Betts: What!

Mat Kaplan: I know, it's never been heard of before except maybe once, I think. Anyway, that voice you heard incredulously there was Bruce Betts, the Chief Scientist of the Planetary Society. Welcome back.

Bruce Betts: Thank you. What!

Mat Kaplan: What up?

Bruce Betts: There's this comment. We talked about it last week. You've been stuck under the fog and clouds, haven't you?

Mat Kaplan: I've tried twice. Socked in, as they say.

Bruce Betts: So, Comet NEOWISE has turned out to be pretty groovy, especially for those using binoculars and taking pictures. There's some gorgeous pictures on the web. You can't see it naked eye. I don't expect it to look quite as stunning as in the pictures with your eyes, but it's still pretty darn cool. And will depend on how much light pollution you've got as to whether you're able to see, how much of the tail you may be able to see. Or, it may depend, for Mat, on weather clouds follow him around. So, how do you see it? It's passing into the evening sky, by the time this is coming out. That's the best place to look forward. The farther north you are, the better. So, in our neck of the woods, Northern U.S. and Canada will do better than lower, but it's getting higher in the evening sky each night.

Bruce Betts: And if you're in the southern hemisphere, look online for pictures, because, sorry, that's all you're going to see. So, look to the northwest, low in the northwest over the coming few days, and the comet will be there below the Big Dipper, below Ursa Major. It'll be rising higher in the sky each night, but it'll also be getting dimmer as it gets farther and farther from the sun. So, it's a trade-off. You're going to want to look probably an hour or so after sunset, because that's the trade-off between it being higher in the sky and the brightness of the sun. I do encourage you to find an online finder guide because it is moving from one night to another and it'll help you find it. It is not streaking across the sky as shown in most cartoons, just a little tip there. Anyway, it's up.

Bruce Betts: And if you're looking in the evening sky, look over in the east just a little later and you'll see bright Jupiter with yellowish Saturn nearby. A couple hours later, middle of the night, Mars coming up, and in the predawn sky, Venus dominating the predawn east, getting higher as time goes along. Good stuff. If you don't have clouds and if it makes feel any better, Mat, I'll retell my story. I spent 12 nights on three trips at Palomar Observatory long ago, and every night was cloudy.

Mat Kaplan: I do feel better now. Thank you.

Bruce Betts: Feel my pain, let it soothe you.

Mat Kaplan: Share your pain. Yes, thank you.

Bruce Betts: We move on to this week in space history. It was a big week. First humans walking on another world, Apollo 11. In 1975, Apollo-Soyuz took place, with the U.S. and Soviet Union meeting up in space. And then, 1994, we watched the first fragments of Comet Shoemaker-Levy 9 slam into Jupiter.

Mat Kaplan: 51st anniversary of Apollo 11. Hello to Michael Collins and Buzz Aldrin out there.

Bruce Betts: We move on to random space thought.

Mat Kaplan: That's the Kuiper belt trying to make me feel worse, I think, by hissing at me.

Bruce Betts: Just for you, mat, I've got an all comet show. So, comet tails can some times be as long as the Earth-sun distance, as long as one AU.

Mat Kaplan: Wow, stunning.

Bruce Betts: And they always point away from the sun, even when it's headed away from the sun. That one I've used long ago. But, good to keep in mind, tails are leading as Comet NEOWISE heads away from the sun. We move on to the trivia contest where we have, not one, not three, but two contest answers. Where shall we start, Mat?

Mat Kaplan: Let's start with the joke.

Bruce Betts: I asked you all to make up a LightSail joke. And we would subjectively, using all of our wisdom and judgment, pick a winner. And I know we did great, Mat, because I've looked at them. Tell me more.

Mat Kaplan: I will, I'm just thinking about our judgment and wisdom, which we probably did use 100% of, between us. We probably have 100%.

Bruce Betts: No wonder my brain is tired.

Mat Kaplan: All right. So, here it is, folks. Thank you to all of you who submitted, you did entertain us, every last one of you, but we don't have time to give everybody. I'll read a couple of runners-up. Robert Johannessen in Norway, "Two LightSails were crossing the asteroid belt on their way to the outer solar system, when one got hit by an asteroid. The other LightSail said, 'Chances of you getting hit by an asteroid were more than this joke winning anything.'"

Bruce Betts: Turned out to be right.

Mat Kaplan: And the other one from Mel Powell in California, he actually submitted a whole bunch, but here's the one that Bruce and I liked the most. He said he wanted to come up with something funny about how LightSail 2 changes direction, but all the jokes he thought of were too tacky.

Bruce Betts: Tacky. Tack like a sailboat. We tack ever twice in orbit.

Mat Kaplan: He said, "That's the one that hurts Dr. Betts the most. Sorry." All right. We couldn't really narrow it down to just one. So, we have two winners.

Bruce Betts: Of such craziness, Mat, such craziness.

Mat Kaplan: They're both going to get Planetary Radio T-shirts that you can find at the Chop Shop Store, But guess what? We're going to throw in two coupons for pints of Ben and Jerry's ice cream. In particular, of course, we hope you can find Boots on the Moooo'n, the flavor that we talked about a few weeks ago, the one they came out with, in honor of the appearance of Space Force, the new Netflix TV show with Steve Carell. Well, we have a couple of these left. And if we get them out quickly, I think they're only good for another couple of weeks. So, we'll try to get them right out.

Mat Kaplan: Here's the first of our winners, Jean Lewin in the state of Washington. And he also submitted, I think, 10 different jokes, but here's the one we like the most, "Why didn't LightSail invite Earth's atmosphere to the party?"

Bruce Betts: "Why? Because it was such a drag." Earth's atmosphere, it's a drag. That it is a drag.

Mat Kaplan: No, no, you don't have to explain it, it's no good. And then, maybe not surprising, the only one that we teased you with last week, Steven Trolinger or Trolinger's Joke, we'll repeat it here, "Where does the LightSail sleep when visiting?"

Bruce Betts: "The photon." Photon, I just have a bad habit of explaining jokes. Sorry.

Mat Kaplan: Stephen and Jean, congratulations. We will try to get those right out to you. At least, we'll try to get the coupons right out so you can enjoy your Ben and Jerry's. And thank you again everybody for entering. We can go on to the other contest.

Bruce Betts: I asked you, what do the following have in common, the Venus atmosphere near the surface, and some coffee decaffeination processes? How did we do, Mat?

Mat Kaplan: More or less moderate response to this one, respectable, but I think it threw a lot of people. A lot of people talked about how difficult it was to correlate these two things in a Venn diagram of coffee, Java, but they worked it out. Here's a response, not from our winner, sorry, Maureen Bence in Washington State, it's a good week for Washington, but still a good way first to get started, "Steaming hot Venus in my sad decaf brew possess a common connection known as CO2." How close is she there?

Bruce Betts: I would have to say, that is a correct answer. I was looking for more, but I didn't specify that. So, indeed, they both share carbon dioxide, at least, one of the decaffeination processes. But what's I think super cool, super cool, is that they also share another detail. Did anyone else bring that up?

Mat Kaplan: Yeah, a whole bunch of people did, actually. Then we even got some explanations of it from some people. It happens that our winner did not specifically mention it. Is this the supercriticality that a lot of people wrote to us about?

Bruce Betts: Wow, that's super. I like hearing you say that, Mat.

Mat Kaplan: Supercriticalifagisexpial Venus.

Bruce Betts: Yes, the carbon dioxide near the surface and actually the bottom several kilometers of that Venus atmosphere, pressures and temperatures are so high, the carbon dioxide is supercritical. And this supercritical carbon dioxide is also used in one of the decaffeination processes. For those who don't know, the supercritical state is when the temperature and pressure are above the so-called critical point, where distinct liquid and gas phases do not exist. It's just one supercritical goodness.

Mat Kaplan: Thank you for that. I'm still not giving the winner here, we're going to tease it out a little bit longer, so I can read this response from David Deardon in Utah, "Supercritical fluids combine the solvating power of liquids with the low viscosity of gases, but are in between state that is neither gas nor liquids," as we just heard from Bruce. "Supercritical chromatography was largely developed here at BYU by Dr. Milton Lee. Any ads? Love the show." Well, thank you, David. Nice work there. Okay, finally, and I think I wasn't just trying to mislead you, I was mistaken. I think I said, I referred to our winner as a he, nope, it's a she. It's faithful listener, Laura Dodd, up in the far northern reaches of California.

Mat Kaplan: She is a past winner but it has been about two years, by my records. She said, "Both the near surface atmosphere of Venus and a coffee decaffeination process involve lots of carbon dioxide. The other similarity is that I don't want to go anywhere near either one." Congratulations, Laura. We're going to give you your choice of either, of Jim Bell's most recent new books, either, Hubble Legacy: 30 Years of Discoveries and Images, or, The Earth Book: From the Beginning to the End of Our Planet. Both of them look great. I mean, I've actually got The Earth Book and I can definitely vouch for that one. The other one, I can only go by what I've seen online and it seems to be well loved. We'll check in with you, Laura. See which one you want.

Mat Kaplan: I got a couple more for you, Michael Unger in British Columbia, and John Guyton in Australia, and others who, like Laura, complain that if you could only get decaf there, they never want to go to Venus.

Bruce Betts: That could be the scariest thing about the Venus' surface.

Mat Kaplan: Dave Fairchild, our poet laureate, put it a bit more poetically, "Pressure down on Venus is an atmospherics too, mixed sulfuric acid and a lot of CO2. CO2 will make a decaf sure to leave you placid. Most would say, however, they would rather drink the acid." I like that. All right, thank you, everybody. We're now ready to move on.

Bruce Betts: Back to comets. ESA's Rosetta spacecraft was of course very successful studying a comet, getting there in 2014. But here's your question, what and when were the... what and when was? What and when was the last flyby encounter of a comet by a NASA spacecraft? Go to

Mat Kaplan: You have until Wednesday, July 22nd, at 8:00 A.M. Pacific Time, to get us this answer, and get a load of this brand new price. We've never offered either of these before, and if you win, you'll have your choice. It's back to the Planetary Society store, you can get there most easily from It's at, that's where all the great stuff is from Chop Shop. But he hosts our merch. You can either get the 40th anniversary T-shirt from the Planetary Society, which shows the actual location of all of the planets at the time, I think it was November or December of 1979, where all those planets were when our three founders created the Planetary Society.

Mat Kaplan: Or, if you choose, we're bringing back a classic, it's the original Clipper logo for the Planetary Society, that was our logo for so many years. You can have your choice, either the 40th anniversary, or the Clipper logo T-shirt, that blast from the past, if you win this one. And that's it, we're done.

Bruce Betts: All right, everybody, go out there, look up in the night sky and think about your dogs running with their tails in front of them, just like a comet. Thank you, and good night.

Mat Kaplan: That's just too good.

Bruce Betts: Only when they're going away from you, of course.

Mat Kaplan: My hat's off to you, not my tail, my hat's off to you. That's Bruce Betts, he's the chief scientist for the Planetary Society, who joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and it's made possible by its members who know we are the Martians. Join us at And if you're enjoying the show, tell your friends about us and tell strangers by leaving us a quick rating or a review. Thanks.

Mat Kaplan: Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Stay safe and well, ad astra.