A conversation with Chris McKay from NASA and Ronald Oremland from the U.S. Geological Survey about ocean worlds and the search for life. This is the third episode of a mini-series about NASA and USGS collaboration.

Transcript:

Darryl Waller:You’re listening to NASA in Silicon Valley episode 80. Today we are continuing our collaboration between NASA and the USGS with a series of podcast episodes highlighting our work together. As we mentioned last week, the USGS center here in Silicon Valley is moving from Menlo Park to our very own backyard on Moffett Field, right next to Mountain View, California.

In this episode, we are talking about how NASA and the USGS are working together in searching for life on other worlds and in particular the plum of Enceladus, Saturn’s moon. “From orbit to core,” both NASA and the USGS are taking in numerous data points to better understand our favorite planet.

Our guests today are Chris McKay, senior scientist at the planetary systems branch here at Ames. You might remember Chris from past episodes from our podcast. We also have Ronald Oremland, project chief and senior scientist at the USGS water resources division.

As a reminder, we are a NASA podcast, but we are not the only NASA podcast. You can check them all out on NASA Casts, which combines all of the NASA podcasts into a single RSS feed that you can find on Apple Podcasts, Google Play, SoundCloud, or just plug the RSS feed into any podcast app of your choice.

You can even go to NASA.gov to find transcripts or listen to all of the episodes.

So without further delay, here are Chris Mckay and Ronald Oremland.

[Music]

Host (Matthew Buffington): Having Chris here – as I said before, our Jeopardy champion – returning champion. Always on the docket. But Ron, you’re new to this whole shtick.

Ron Oremland: Yes, I are.

Host: And so, tell us a little bit about yourself. How did – I mean, you’re not at NASA. You’re with the U.S. Geological Survey.

Ron Oremland: Yes. I came out here from grad school in ’76. I actually did a postdoc at NASA in Building 239. And then a year into my postdoc, a job opened up at the survey. And I just drove up the road and had a real job. So I’ve been there since 1977.

Host: Really? And that’s up over in that Menlo Park area?

Ron Oremland: Yes, yes. It’s a lovely campus. And now, things go full circle. We’re going to be moving back down here over the next few years. That would include my group. The Menlo campus is lovely. But we can’t afford to stay there anymore.

Host: Well, that’s a throwback to Ian Brosnan – another alum to the podcast. He spoke early on about NASA and the USGS I think my affectionate term “The orbit-to-core” of the federal government science. Looking from the orbit all the way to the core of the Earth to understand how it works. So you’ll be coming and joining us hanging out over here at Moffett Field.

Ron Oremland: If I’m still alive in four years hence, yeah.

Host: So between you and Chris, how’d you guys end up working together. How do you guys know each other?

Chris McKay: Well, I met Ron in 1980 when I came here as a graduate student in a summer course that Lynn Margulis organized called planetary biology. And then I came to Ames as a postdoc and have been interested in the search for life on other worlds. And the kind of organisms we’re searching for on other worlds are the kind of organisms that Ron studies. So we’ve been in contact on and off for decades.

Host: Oh, wow.

Ron Oremland: And it’s just by chance. Certainly, some of my interests have been along those lines. But that’s not necessarily what I was assigned to do at the USGS. And what I was assigned to do was contrary to my background – which was oceanography and anaerobes. They wanted me to do something with freshwater streams. So I made some compromises. And they really were interested in nitrogen cycling in freshwater streams. And at the time, the assay de nouveau was the acetylene block assay. You had acetylene. And you measure accumulation of nitrous oxide as a measure of denitrification – that’s loss of nitrate to molecular oxygen.

They wanted that information. And we stumbled on bugs that actually eat and ferment acetylene. That was a lot more interesting than the nitrate side of the story. And we sort of kept that going for a while. And then some colleagues over in Germany isolated a bacterium that was similar to ours. And they did this marvelous study over the course of the next decade or so where they isolated the acetylene hydratase and found that it is specific for acetylene. And we were left with this data on our bug that we really couldn’t reproduce. And we couldn’t publish in a microbiological journal. Because it was already taken by our German colleagues.

And so, I started looking up to the sky for some sort of, “Oh, god. Help me. What have I done? What should we do?” “Son, Ronald, there’s all these planets out here that have acetylene gas in them.” And so, I made a cock-and-bull story. And it got published. Carl Sagan actually reviewed it. And then it sort of sat dormant for a decade or so. And then NASA exobiology funded us. And we’ve kept it going over these years. So when this opportunistic of Orbit to Core came up – Chris has been interested in this story. And I’m interested in this story.

And we circle in these various meetings with regard to Enceladus. Are the gases coming out? Is there a biological signal there? And my interest is the possibility that there’s acetylene there. Titan has acetylene. And well, we wrote this little get-together proposal. And here we are.

Host: Nice. And Chris – because I know you’ve been all over the world looking for the extreme bugs or microbial understanding how life lives in extreme situations here…

Chris McKay: Well, the connection to the work we’re doing here at NASA is, “How would we search for life on other worlds?” And in particular, our focus right now is on the plume of Enceladus. And we looked up Ron a few years ago when we got the data back from Cassini that showed that there was methane in the plume, hydrogen in the plume, carbon dioxide in the plume and possibly acetylene in the plume. And the question to him really was, “Could any of these things be made by organisms? Could they be consumed by organisms? Is there any biological signal here?” And so, the acetylene story is very interesting.

If there really is acetylene in the plume and if Ron’s organisms are living in Enceladus eating that acetylene, what would they be making? And there’s a very interesting answer to that question, isn’t there, Ron?

Ron Oremland: They could be making carbon dioxide. They could be making ethanol. They could be making acetate. And if there’s another group of organisms there – methanogens – those things lead to the production of methane. So we could be seeing bacterial poop coming out in the plume of Enceladus. And if that’s true, we should be able to pick up certain signatures that are characteristic of life.

Host: Well, this is the funny thing. You think of looking out under the stars and trying to see life on other moons, other planets, whatnot. It’s like we kind of have some good examples that we’re sitting on. Like the only example of life is here on this planet. So it behooves us to understand what’s going on here in some of these extreme situations and seeing how that relates.

Chris McKay: Right. So maybe the gases coming out of Enceladus are essentially swamp gas – the same sort of thing produced in a swamp by methanogens and anaerobic communities of microorganisms putting out gas. And that’s what we’re seeing. And they may be mixed in with non-biological gases. And so, we’ve got to figure out how to tell the difference. And Ron hit on a key point. When we fly through that plume and take samples, what should we look for? What are the signatures that would tell us, “Hey, there really are organisms living in here. And so some of this methane and maybe some of this acetylene is being worked biologically?”

Ron Oremland: It’s a very exciting time to be in this field. On the one hand, we have the results with Kepler and extra-solar planets and planetary systems. But we really can’t derive a huge amount of information from them that says, “Yes, there’s definitely life there based on the gases and proximity to the stars.” But who would’ve thought that in the outer solar system there are some really strong candidates for what Chris would call “habitable” worlds? Not necessarily “inhabited.” But habitable in the sense that all the ingredients for life are in the water that’s underneath the ice. That’s really, really exciting.

And in the case of Enceladus, it was discovered by the Cassini mission that these gases are coming out through these fissures in the southern hemisphere. I like to think of the analogy of Sylvester the cat saying, “Sufferin’ succotash! If you collect all the spits, you might find signals for life in there!”

Host: I think back to when I was a kid. And you’re learning about the solar system. And you always kind of thought of the planets that are so far out there that it’s just all ice. There’s not much out there. And so, for people who don’t necessarily follow all things NASA all the time, Chris, talk a little bit about what is different about these moons – these ice moons that are circling Saturn or Jupiter. How is it possible that anything could live that far out where it’s so cold and so far away from the Sun?

Chris McKay: You know, you’re right. It’s a surprise. When I was growing up, I also had the same impression of the outer solar system. Too cold to be interesting. Let’s focus on Mars. But as we’ve gone out there with spacecraft, we’ve discovered Europa and Enceladus and other moons with ice surfaces but oceans underneath. And that really changed the paradigm. There are oceans in the outer solar system. Who would’ve thought? But then, even more remarkable was the discovery of the plume of Enceladus where the ocean is coming out through the ice. So suddenly, not only is there an ocean. But it’s an ocean and we can get to it. We can analyze it.

And I was blown away by this discovery. This was a result of Cassini. And it really reoriented my thinking about, “What should we do in space?” And all of a sudden, my focus shifted to, “Let’s go to Enceladus. Let’s fly through that plume. And let’s smell that swamp gas and see what kind of organisms could be making it.” And it was really exciting to know that that’s the same kind of ecosystems that we can walk through in San Francisco Bay and in the muds of right here in Moffett Field. It’s a very familiar scenario. Microorganisms are making methane and other gases.

Ron Oremland: From my perspective, I wasn’t involved in any of this work. I was just a layman seeing it come on television. And to watch the results of the Cassini mission were unbelievable – really mind-bending. And then I really love the Huygens lander on Titan. And in some of the lectures I give, I say, “All right. If somebody gave you a few billion dollars and said, ‘All right. I want you to go out and get trapped in an orbit around Saturn and look at its moons and see what you can see. Then land a package on Titan. Soft land it so we can get some data.’ That’s an incredible achievement. Incredible achievement.” I’d love to see it done again.

Host: Well, the thing that I get a kick out of is it seems like in all the extreme areas of the planet Earth – whether it’s near lava, or in the bottom of the ocean, or near an acidic – life seems to find a way, to steal a Jeff Goldblum quote. Life seems to find a way. Seems to be the tale on this planet, at least.

Chris McKay: Well, life does seem to live in a lot of exotic places. But one of the interesting things about Enceladus is that environment is not extreme at all. Inside that ocean, the conditions – we think – are sort of like the conditions in the sediments that Ron studies. It’s pretty cozy. The organisms are very happy and merrily producing gases like methane. And doing things like eating acetylene and so on. And so, we can find analogs for these methanogenic ecosystems literally right next door.

Ron Oremland: The advantage of Enceladus is that because these materials are being spat out into space, we don’t have to drill through kilometers and kilometers of hard ice. So that’s the real allure. The other aspect that should be mentioned is Enceladus is really far away from the Earth. If there’s life under that ice, it would be what we would call a “second genesis.” Because in the case of Earth and Mars, there’s been exchange of materials. So you can always invoke, “If there’s life found on Mars or was found on Mars, it might’ve come from Earth or vice versa.” It’s not out of the question.

But in the case of Enceladus or Titan, they’re so far away that it would have to be formed independently. And if that’s true, there’s probably a lot more life way out in our galaxy and in the universe than we would imagine.

Host: So talk a little bit about – what is the day to day? How do you guys work together? These two government agencies, but you have teams working together going back and forth. How does that happen? How does that work?

Chris McKay: Well, what are we going to do? And this new project, what we’re going to do is that we’re going to take the data that Ron and his team produce from these ecosystems that they study. And then ask the question, “How could we build instruments on our spacecraft that would detect that? What are we going to detect?” Like, for example, if we posit that there are methane-producing organisms, what other compounds would they produce besides methane that might be indicative of their presence? What should we look for? What kind of biomarkers? And if there’s acetylene-consuming organisms, what are their byproducts?

So if we find acetylene, what do we look for as the indicators that organisms might be consuming? So Ron has been doing that research on Earth in his ecosystems for Earth reasons. These are interesting ecosystems to Earthlings. And we’ll just take those results. And then map them into our strategies for spacecraft exploration.

Ron Oremland: That’s one aspect we’ve been working on for the case of acetylene. If you have microorganisms that grow on acetylene, the acetylene that doesn’t get eaten would be enriched in Carbon-13 relative to Carbon-12. Because microorganisms like a light diet. And then the products that they would spit out – which would be acid aldehyde, ethanol acetate – those would be enriched in Carbon-12. They’d be even lighter. And then if there’s other microorganisms in this ecosystem like methanogens, they would consume these precursors and make methane that’s even lighter.

So we may be able to have a viable search for life looking at stable isotopic composition of some of the gases that are emanating from a place like Enceladus. That’s one strategy where we would meet. The other is a bit more practical and down-to-Earth and has a USGS component into it. We also discovered that these acetylene bugs are involved in the degradation of human-made or anthropogenic contaminants. And it’s specifically the case in trichloroethylene. The chemical degradation of trichloroethylene gives off acetylene gas. And these types of microbes that we study aggregate where acetylene is being formed. And they consume that gas.

And that actually enhances the process of biological and chemical degradation of toxic compounds like TCE. And in fact, NASA Ames Research Center has plenty of contaminated TCE here as a legacy of all the aircraft cleaning going back to the days of the Navy and dry cleaning as well. So there’s many things to study here. It’s a really good place.

Host: Is this kind of a normal thing? Of different government agencies working together? Have you guys been – it seems like such a natural thing. But you don’t see it as much.

Chris McKay: In this case, it’s facilitated by the fact that we’re close together.

Host: Yeah, proximity.

Chris McKay: Menlo Park’s not far from here. And these guys are now going to become even closer. And also by a shared interest. Ron has had an interest in the space connection of his work. And I’ve had an interest in the Earth connection of our work. So I like methanogens here on Earth as well as on Titan and Enceladus. So there’s a natural link. I can’t think of any similar link with other federal agencies – at least in the work I’m doing.

Host: Yeah. I remember chatting with Ian about some of the work going through. Of how it made sense if you have – you know. You think of NASA, you typically think of these big satellites that are looking at Earth. And it’s kind of taking the big-picture scope. But then, some of the data from USGS of tags on animals or other little things – it’s almost tiny. You’re getting some itty bitty granular data. But at the same time, getting the big picture data. But with their powers combined, then you just have a much better understanding of the world.

Ron Oremland: Well, Chris and I have never actually collaborated previously. But we have common interests. And we’ve known each other over all these years from meetings. I know what he works on. He knows what I work on. And then this Orbit-to-Core competition came in and said, “We really need to put our heads together. Not just for the funding, but because we do have common interests.”

Chris McKay: That’s right. We’ve referenced each other’s papers before. This’ll be the first time we’ll have produced a paper together.

Ron Oremland: We’re under the gun, Chris. That’s right.

Host: And so, what is the timeline? What are you guys looking at? How do the next couple months or even years of working on this to look for you guys?

Chris McKay: Well, for the proposal that we’re funding now, we’ll probably try to wrap that up within about six or seven months. So that’s – but this hopefully is the start of a long-term collaboration with microbial ecologists from the survey – Ron and his colleagues – and people like me at Ames who are interested in life detection. Life detection is a growing activity at NASA Ames. It’s a growing focus here. This is exactly the sort of collaboration we need to provide a scientific basis for that search. So this is the start. And I think this joint activity will outlive both Ron and me.

Ron Oremland: Speak for yourself.

Host: So Ron, tell me a little bit or talk a little bit about how this all relates to the origin of life, and some of these microbes, and some of these things. How does that kick off our understanding that we have?

Ron Oremland: Well, I’ve got to tell you a little bit more about how these ideas come about. And it’s not by sitting down smoking a pipe and thinking really deep thoughts. At least, in my case, it’s by serendipity. We made a discovery. It’s by human circumstance. Some of our data, we got scooped. And we had to think of another reason for publishing the data to another forum. So that got us into this exobiology idea that on an early Earth, if you use the Miller-Urey model of all these organic compounds that are being sparked or exposed to high energy photons from the Sun, they form more complex systems. Which eventually form more complex organics and rain down. And somehow, life jumps out of that.

If methane is subject to attack by photons from the Sun, it breaks apart and forms methyl groups. Which form back on themselves and eventually start forming things like acetylene. So we could hypothesize that once, on the early Earth, there might’ve been an appreciable concentration of acetylene in its atmosphere just as there is now in Titan or some of the gas giants in the outer solar system. But it’s not there now. It’s there at very, very, very low levels. Much lower than methane. But it’s there. But nothing like it could’ve been at the dawn of life four billion or so years ago.

So this enzyme was discovered – acetylene hydratase – in these particular bugs. And it’s specific for acetylene. It won’t do anything else with analogs that are triple bonded. So the conundrum is, “Why is this still possible? Why do we have organisms that can eat acetylene?” So I said, “Well, somehow, it’s survived four billion years. There’s got to be a reason for it.” Now, we’re starting to think that there are other sources of acetylene that we’re not seeing that are natural from unsaturated organic compounds. But the revelation my colleagues at the USGS and also at the University of Alabama have made is that when we now enter the word “acetylene hydratase” into one of these computer databases, we get thousands of hits. Where only a year ago, we maybe had five.

And further scrutiny of this point finds that a lot of those gene hits are viable candidates for acetylene hydratase. So coming from classical microbiology, we had maybe two or three species for these last 30 years that we said, “Well, okay. These guys are typical of what was crawling out of the primordial mud.” But it seems to be in the genome of thousands of microorganisms. The reason we know this is because the technology of genome sequencing has increased. And the computer now sees all of these things. And we don’t see it. But you ask the computer – the all-wise Hal from 2001 –

Host: Nice reference.

Ron Oremland: It says, “Yes, David. David, there’s plenty of acetylene and hydratases out there. Open the pod bay door, please.”

Host: And how does this play into your world, Chris?

Chris McKay: Well, if we find, for example, now acetylene in the plume of Enceladus, then that becomes an argument – as Ron was just saying – that these molecules could’ve played a key role in the start of life on Earth. And if they’re present in the plume of Enceladus, maybe it’s encouraging for life. A second related point of that is some of these organisms of interest – like methanogens – trace back to very early in the evolution of life on earth. They were there at the beginning, as far as we can tell in terms of looking back to the common ancestor. And so, again, the kind of ecosystems we’re seeing in Enceladus are encouraging in terms of the possibility that life started there.

Host: So for folks who are listening, if you want to reach out to either Chris or Ron, we are @NASAAmes on all the social media platforms you can think of. And we’ve been using the hashtag #NASASiliconValley. We also have gone analog and have a fancy phone number. That is 650-604-1400. So call and leave us a message. And we’ll figure out how we can throw that into the next episode. But thanks for coming on over.

Ron Oremland: A pleasure.

Chris McKay: Thanks for doing this.

Host: This has been fun. alH

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