Astrobiologist with NASA Ames Research Center
Dr. Christopher P. McKay holds a PhD in AstroGeophysics from the University of Colorado, Boulder and his research interests focus on the evolution of our solar system and the origin of life. He studies life in extreme conditions that are similar to what exist on Mars, including the Atacama, Namib, and Mojave Deserts and the dry valleys of Antarctica. He has been a co-investigator on several instruments that have flown to Mars and is active in planning future Mars missions, including the proposed Icebreaker Life mission.
The following interview was conducted at the Desert Studies Center in the Mojave National Preserve near Baker, CA in March 2012. It was at the end of a week-long field study of biological soil crusts in the Mojave Desert conducted by researchers from the California State University system, NASA Ames, the Astrobiology Institute, and several other groups. I was there as a practicing science teacher through my participation in the Mars Education Challenge sponsored by Explore Mars, Inc. At the time of this interview, the Mars Science Laboratory (Curiosity) was on its way to Mars. NASA was developing the Space Launch System with a plan to send it and the Orion capsule to a small asteroid as a test mission.
David Black 0:48
Thanks for being willing to do this.
Chris McKay 0:50
David Black 0:51
Okay, so first question. What’s your background? How’d you get into astrobiology and into working with NASA, NASA Ames.
Chris McKay 0:59
I think got interested in astrobiology, it wasn’t even called that, when Viking landed on Mars. Here was a very sophisticated spacecraft, lands on Mars searching for life, and the signal that it sends back to Earth can really be summarized as, well, all the elements needed for life are here, but there’s no evidence of life. I took a sort of “lights are on but nobody’s home” message. I got real interested in that I was a student at the time, started following up on what does this mean for Mars, and that got me into life and then started sitting in on microbiology classes. And then NASA Ames had a summer program for students and I went there for the summer and that really got me involved in the astrobiology perspective. And as a result of that summer program, I ended up doing fieldwork in Antarctica and that got me turned on to life in extreme environments and how places on earth could be used as models for life on Mars. And I’ve been doing that ever since.
David Black 2:03
What did you study in college?
Chris McKay 2:05
I was in graduate school at the University of Colorado and I was in an astrophysics program. And when I entered graduate school, I had no idea that I’d end up veering toward astrobiology. It was – it sort of took me by surprise.
David Black 2:19
Is it more correct to say astrobiology or exobiology?
Chris McKay 2:28
Well, in the late 90s, they decided to invent something called astrobiology, so that they could go to Congress and say we have a new program give us more money. So, conceptually, it’s the same thing we’ve been doing for many years.
David Black 2:42
What are the differences, if any, between astrobiology and exobiology?
Chris McKay 2:52
Well, there’s a lot of overlap between what used to be called exobiology and what’s now called astrobiology. I – I think the difference is semantics, at least in terms of the things I’m interested in, it didn’t change. I was interested in what we now call astrobiology starting as a graduate student in the in the early 80s. So there’s been a continuity of intellectual pursuit in terms of what I’ve been working on. And we used to call it exobiology and now we call it astrobiology, whatever.
David Black 3:24
So lately, though, the public attention and – and at least some hope seems to be rising that astrobiology will soon be achieving real results.
Chris McKay 3:35
There’s a lot of growing interest in astrobiology and I trace it back to a couple things. First, the discovery of the nature of the early universe and star formation and dark matter all those things. Second, the discovery of extrasolar planets, planets around other stars and then finally, there was also coming back from Mars, including the Mars meteorite of many years ago, which has since proven to be not as scientifically valid as we once thought, but it sparked interest in the notion of life on Mars. And then, right on the heels of that announcement came a series of Mars programs, rovers and the Phoenix lander, which really continued to capture the attention and keep the spotlight on Mars.
What’s our best chance for finding evidence of life outside of the earth?
Well, there’s three places where we might find evidence for life, Mars, Europa, the moon of Jupiter, and Enceladus the moon of Saturn, those three places. I think it’s a fair bet on which one is going to be the most likely to give us a first sign of life. Mars is close. We have evidence of water but it looks like the evidence of life may be hard to get to. Europa, we have clear evidence of water, but it’s deep below ice, it’s not clear we’re going to get access to any evidence of life on the surface anytime soon. Enceladus, much smaller, maybe younger in terms of its biological activity, but the samples are coming out in a plume and we know there’s organics in there. So it’s interesting as well. It’s hard to predict which of those three worlds is going to be the one that’s going to be most interesting.
If you were to design a probe yourself, where would it go and what would it do?
If I was building a probe in the McKay Rocket Company, we would fly through the plume of Enceladus, get a sample, analyze it for biological organics, and bring that sample back to Earth.
How would such a mission be able to bring back samples?
Well, the hardest part of such a mission is the long trip going to Saturn and then once you reach Saturn slowing down so that you can fly through the plume, at a relatively slow relative speed so that you don’t destroy the samples from the impact velocity, and then the long trip home bringing the sample back home. So those are the challenges on such a mission. They’re things we know how to do, that just require fairly complex systems to do it.
What are some recent concepts for exploring whether life can survive on the moon and Mars?
We are working right now on a concept to grow plants on the moon. Well we want to do is just send seeds and just grow them for a week or so so that they germinate. So that’s our first step germination under lunar gravity and lunar radiation.
So the sample would be sealed?
That’s right. The sample would be completely sealed. When we landed on the moon, water would be injected and the seeds would start to grow.
With Earth soil, Earth water, and seeds, right?
We probably wouldn’t use soil, we probably use a filter paper and the seeds would be impregnated into the filter paper. And when we landed on the moon, a little jet of water or earth, water would be injected into the container, and they would start growing, the only thing we’d be testing is growing in lunar gravity and lunar radiation, everything else would come from Earth, the air, the water, the chamber, the plants would all be Earth, but it would be growing in the lunar environment. And what we’d have is thousands of duplicates growing in the Earth environment for comparison.
What would be the advantage of doing that?
Chris McKay 7:37
But it would tell us whether plants can grow in lunar gravity. We don’t we don’t actually know that right now. We know plants can grow in Earth’s gravity. And we know that plants can grow although differently in zero gravity, but we don’t have any data at intermediate gravities, Moon or Mars gravity. And that’s we are assuming that plants will grow fine, we assume that Mars gravity or moon, gravity will be all right. But we don’t know that. So it’ll be the first direct evidence of that effect. And in addition to the gravity, there’s the radiation environment. And there’s some speculation that gravity and radiation might somehow have interacting effects, which could alter patterns of development. And growing a plant from seed will be the first test of that.
David Black 8:27
And then ultimately, to do something similar on Mars?
Right, once we’ve demonstrated that we can do a plant growth plant germination experiment on the moon, I would then push for doing it on Mars. It’s further, it’s harder, more expensive, but it’s ultimately the place where I really want to grow plants.
Given how difficult it is to get this kind of funding from NASA, using the support of private corporations is the future of space exploration. What are some of the possibilities and some companies you’ve worked with?
I think that that space exploration is in transition right now. It’s in the transition from a completely government dominated government controlled enterprise into a mode where government is a customer, but one of many customers. And the private sector is providing Launch Services to ships, the airplanes the equivalent of. And so we’re moving into a system where companies will provide the rockets, and NASA will be a customer on that. There may also be a mode in which cost of experiments get down low enough that we can look for private sponsors, we can go to a foundation and say, Would you be interested in doing a plant growth experiment, and the costs may come down to the point where private foundations could support those kinds of experiments.
For example, X PRIZE sponsoring the next moon landings.
Exactly. An example of all this is the Lunar XPrize where Google is putting up significant money to sponsor companies to do organizations to do lunar missions. That’s a definite change in paradigm from the way we used to do lunar missions, which are all always state space agencies. Government funding,
Would you be in favor of a quick and dirty sample return mission to Mars?
Chris McKay 10:30
Well, to me, the first sample return mission should be a simple one, it should land it should grab some soil and it should bring it back and it should do the whole thing quickly, easily and in one opportunity, and at low cost. After we’ve done it once a simple one a demonstration and engineering tests so to speak, then we can do more complicated, more sophisticated missions. But if we set our sights too high, we’re never going to get there. We need to set our goal for simple, near term sample, the same way we did rovers, the first rover to Mars was the size of a shoe box, and just went a few meters. That was it. It couldn’t have couldn’t do much it didn’t have high scientific goals. But then the next rover was bigger and more capable and our rovers even more bigger and more capable. And then we have to take the same approach the sample return, the first sample return, gotta be simple, direct. And then from there, we build up the capability to more.
David Black 11:28
The current plan for a Sample Return scenario is too complicated?
Chris McKay 11:35
Too complicated – too complicated, too expensive, and it’s never going to happen. And that that kind of logic of this complex sample return mission derives from a notion that we’re only going to do one would be like saying, well, you’re only going to ever get one rover on Mars. Well, then, of course, the rover ends up having to be a big giant, fancy rover that does all these things, but that’s not the way we do things. It’s not the way we’ve done things and it’s not the logical way to do things. A logical ways to do something small and simple first, and then build on that experience and do ever more complicated missions. Why? Why wouldn’t we want to take that same approach to sample return?
David Black 12:12
We’re sending a very complex rover now.
Exactly. This is the fourth rover to go to Mars. We would not have sent this as the first rover.
So we’re out here in the middle of the Mojave Desert. Why are we coming here to study astrobiology?
Chris McKay 12:34
Deserts are particularly relevant for the study of life on Mars because Mars is a desert world. So when we study deserts on Earth, we see many of the chemical and biological processes that we think are happening on Mars. We see oxidants in the soil, we see challenges in the preservation of organic material, we see life trying to adapt at very low levels of moisture. These are all themes that keep occurring when we think about life on Mars. And so deserts in a way provide us a way to hone our analytical skills, test our instruments, learn what we’re doing. So when we go to Mars, we have a better idea of how to proceed.
So this desert is a feasibility study.
It’s like a training study. We’ve tested out Mojave, if we can’t get it to work in the Mojave, we’re not ready to send it Mars.
David Black 13:24
So we’re looking specifically at these biological soil crusts. In what ways would they point the way towards what we could find, especially on Mars?
Chris McKay 13:37
While we could imagine that at one time, Mars was wet enough that biological soil crusts could have formed. There also, these crusts are also very interesting here on Earth in terms of maintaining, maintaining the desert surface. And we there’s many things we don’t understand about these crusts and about their distribution. So they, they’re fascinating directly and one of the things that happens when you study deserts, as you realize how interesting they are. And so we start asking questions that are specific to the desert. And maybe we lose a little bit the connection to Mars, but we always come back to it eventually. So the soil crust is a good example of that we’re sort of following a lead here in the desert, On these soil crusts, what’s controlling them, where do they grow and why. And eventually, we’ll bring that lead back around and connect it to Mars.
David Black 14:27
Other types of very primitive slow growing life, and we talk about anaerobic bacteria and desert varnish will help us understand the possibilities.
Chris McKay 14:38
Well, they’re all in that same category of things that are living in desert environments and very low levels of water and, and are developing and using interesting ways to conserve water to grow in low water, and so on. So we’re trying to study the whole range of these kind of desert organisms. Right now we’re focusing across previous expeditions here, we focused on the hypolithic algae growing under the stone, again, it’s a model. We study though we study it for its own interests, we do try to apply it to Mars. But we’re not walking around with Mars on our mind all the time. When we’re in the desert, we’re studying it as a interesting system, worthy of interest in respect and study intrinsically. And then once we understand it, we can then apply that knowledge to Mars and past life on Mars. But to really learn about the desert, we have to immerse ourselves in it directly, and then only later pull that knowledge back out and apply it to the Martian case.
David Black 15:37
So the idea that bacteria or some simple form of life might live under a rock or under a layer of varnish or in a symbiotic community is something we can apply directly to our search for life on Mars.
Chris McKay 15:52
Well, first we have to understand it. First, we understand what’s going on in the desert here. Then we draw more general principles. So it may be that none of these ecosystems we studied here directly apply to Mars. But we learn general principles which we can then apply to Mars about how life developed strategies to grow in dry environments. So it would be a mistake to come out the desert and look at a habitat or a rock and say, Ah, that could exist on Mars. I think the analogy is more subtle and more and at the same time deeper than that. So we come to the desert, we study life in this dry extreme, we develop a deep understanding of how life survives in dry extreme. And then we try to apply that deep understanding to Mars and we may not follow the exact detailed path that we’re observing in the desert here. But we may still follow the same general principles. It points to directions and how to look what kind of instruments to send and that sort of thing.
David Black 16:54
The big question of course, is would we know what life is if we ever saw it?
Chris McKay 17:03
This is one place where Earth analogs fail us. Here, we’re searching for life and its life like us. It’s the same DNA baseline that we see everywhere else. On Mars, we don’t know if it is going to be the same DNA base life. In fact, we hope it isn’t. We hope it’s something different, the more different the better from my point of view, and then there’s the problem of how do we recognize it? How do we analyze it? And that’s something we can’t learn studying, first, models. In fact, quite the opposite. Studying Earth models tends to point us in a direction, it’s probably wrong, because we focus on using methods like DNA extraction, which is what we’re doing today. And those methods are only going to look for Earth life. So we end up training ourselves with methods that are specific to Earth life. And so we have to consciously make an effort to realize that those methods will not be what we necessarily want to use on Mars.
David Black 17:56
So if we put aside some of the definitions of what we Life has to have, like before DNA and so on and make a more general rule.
Chris McKay 18:09
We have no idea if there’s a general chemical rule for life, some molecule all life has to have. It’s very hard to make general rules when you only have one example. So I think our approach has to be one of ignorance, we have to say, we don’t know what it is we’re looking for. We just need to look, and we need to be systematic in the search. And if we see something that we can’t explain, and it looks like a pattern that could be biological, we have to be prepared to see that even if it’s not the same pattern we see here on Earth.
David Black 18:40
Is that part of the reason why Mars Science Lab, they say, you know, we’re really not looking for the possibility of the molecules being associated with life, which seems kind of a strange way of putting it.
Chris McKay 18:53
But I think part of the reason is, is the rover, the Mars Science Lab rover doesn’t really have the capability to make a convincing case for life even it’s there. It has a capability to detect organics, and that will be very interesting. And it may lead to missions that follow up on that, that will have direct and definitive instruments to search for life. But it does not have such instrumentation. So it can give us very interesting results. They can tell us whether organics are present, and might even hint that they could be biological, but it’s very unlikely that it will make a definitive case that there was life here is life here on Mars.
David Black 19:32
But this is the next step. stepwise trying to do the whole thing.
Chris McKay 19:40
Well, the way I like to think of it is the previous missions have established that there was water, liquid water, they just sort of follow the water strategy. Okay, we’ve done that. Check on the water. What’s the next step? Next step is search for organics. Water is what life lives in, organics is what life is made of. So we have established I think that Mars had water and throughout early in its history and in periods throughout its history. The next step is to see if there’s any organic because that’s what life is made of. The step after that would be to search through those organics for signs of biologically produced organics, MSL, the Mars Science Laboratory won’t really be able to take that step. But if it finds organics, then one could imagine a follow on mission that would search through those organics to find evidences of evidence for a biologically produced organic, like DNA is an example of organic molecule that’s clearly biologically produced. Proteins, complex proteins, enzymes, things like that as well, whereas simple amino acids may be biologically produced, maybe not.
David Black 20:48
Would it need to be a sample return mission?
Chris McKay 20:51
I don’t think so. I think you could do a definitive life detection mission using this approach of looking at biomolecules organic molecules on Mars. Sample returned be much easier and more powerful. But I think we could do it in situ as well.
David Black 21:28
Why is that important?
Chris McKay 21:32
I think there’s two reasons we’re searching for life. One is to address the fundamental question, philosophical question, deep scientific question. Are we alone? Is there life beyond the earth? Is the universe full of life? Or are we just some oddball situation here? But there’s also a second question, a practical question, which is, are there other ways to do life? We have on earth one example of biology one example of a genetic code, one example of a way to make proteins and structural molecules. There may be other ways. And if we could discover another example of life that does the same sort of processes with a different set of chemicals or different set of organics, that may give us deep insights into the nature of life that we may never get by just studying the one example we have. And that insight may prove very useful in very practical ways. In – in terms of all of the technologies and science that rest on biochemistry, think of medicine, think of agriculture, think of disease control, think of pesticide controls, think of all the things, the technologies and aspects of our life that are rooted in our understanding of biology. It’s vast, it’s enormous. And if that understanding is broadened by having two examples of biology that could have very practical, important implications. So there’s two answers to wide search for life, one philosophical and one practical.
David Black 23:01
We would have to rewrite all the biology textbooks.
Chris McKay 23:04
That’s a minor inconvenience compared to the information we would gain by having a another type of life – Life 2.0, I call it, to study.
David Black 23:15
Imagine that kind of a revolution in biology would almost be like the revolutions in astronomy.
But it would be very interesting it would be like, if the only star we could ever see was the sun. And suddenly, we could see other stars. And we could see many different types of stars, we have more than one star to study.
So suddenly, we realize there’s a whole range of stars.
Exactly, exactly. Things that would be very hard to deduce by just studying one star, like the sun, even if you could study it in a lot of detail. It’s very hard to do that. Science is data driven. And with biology, we have only one dataset, we need more than one data set.
Okay, so final question. In the future if we could go anywhere and have the budget to do anything besides going back to Mars with a biological test rover or a sample return, which would be kind of a sequence you would see, what places you would want to go?
Chris McKay 24:21
Well, if I was pushing permissions, I would push very hard for an Enceladus mission. Here we’ve got a plume water organics coming out of what looks like a habitable environment in the subsurface of Enceladus. Samples right there in space – grab and go. I would push hard for that. I would push hard for a Mars mission. That’s a sample return and then human exploration. I think we need to move we need to move toward human exploration on Mars very quickly. I think because human exploration will open up questions that we can’t open up any other way. They’ll explore the planet in ways that we can’t really achieve completely with robotic missions and they’ll address questions like “Is Mars a place where humans can live?” Obviously, it’s a question that needs humans on site to address.
I’ve heard if we cut down the time for Mars – I know that this is a topic that is way out there – SpaceX is talking about the possibility that we would cut the cost down and they’re working on it.
Chris McKay 25:28
I think it’s gonna be many years before we send humans to Mars, I think we will first set up bases on the moon because it’s much closer, we’ll learn how to stay on the moon. First, we know how to go to the moon. We really already know how to go to Mars. We don’t know how to stay. We don’t know how to stay on the moon. We don’t know how to stay on Mars. I think we need to learn to stay on the moon first, just like we learned to go to the moon first. Once we’ve learned how to stay on the moon, we can then go to Mars and stay on Mars.
So now we’re ready to send humans back out into deep space to an asteroid. You think there’s a use for an asteroid mission?
Chris McKay 26:08
I think it’s interesting. It’s a – it’s a, it’ll be our first trip out of the earth moon system where we have to deal with deep space. And so I think it’s a it’s a good it’s a good mission to plan. It is not a long term activity. It’s a base on the moon might go 100 years or base on Mars might go several hundred year and asteroid mission is sort of a training so it might last three or four years, but that’s it. I don’t think we would ever set up a base at an asteroid or something like that.
At this point we ran out of time for further questions. I thanked Dr. McKay for graciously granting me this interview.
In the years since, NASA has abandoned its plan to use the Space Launch System to go to an asteroid and has instead decided to return first to the moon with the Artemis missions and establish a lunar orbiting station called Gateway which will support a full-time base on the moon and provide us with the experience needed to send humans on to Mars. Curiosity landed on Mars in Gale Crater as planned and is currently exploring the clay deposits of Mt. Sharp. It has proven that the water in Gale Crater was neutral in pH and could have supported life. The Mars 2020 Rover (Perseverance) launched last month and is on its way to Mars and a landing on Feb. 18, 2021 in Jezero Crater. It has the instrumentation to search for actual life, past or present, and will cache samples of soil for future return to Earth by a European Space Agency Fetch rover. It also carries the Ingenuity helicopter demonstrator.
Elon Musk and SpaceX continue to achieve remarkable milestones as the Crew Dragon capsule has carried the first astronauts to the space station this May and safely returned them two weeks ago. The Starship prototypes are making continued progress, and the Falcon Heavy system has also been launched which can carry large cargos into orbit. The Space Launch System is behind schedule and over budget but making progress.
A Europa Clipper mission has been approved by Congress, and the Cassini probe that discovered the plumes rising from Enceladus has now been crashed deliberately into Saturn. No mission is yet planned to gather samples of the plumes of Enceladus for return to Earth.
Transcribed by https://otter.ai