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Season 4, Episode 15 Looking For Life in Ancient Lakes

Season 4Episode 15Aug 14, 2020

As the Perseverance Rover flies toward Jezero Crater on Mars, which once hosted water, astrobiologists are interested in places on Earth that are similar to the rover landing site.

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Astrobiologist Kennda Lynch at her field site in Pilot Valley, Utah.

As the Perseverance Rover flies toward Jezero Crater on Mars, which once hosted water, astrobiologists are interested in places on Earth that are similar to the rover landing site. Kennda Lynch, scientist at the Lunar and Planetary Institute in Houston, Texas, has been doing fieldwork in an ancient lake location in Utah called the Pilot Valley Playa. In this episode she describes her recent discoveries and why she’s excited about Perseverance. She also explains how all life forms create waste products, even bacteria, that could leave tracers or “biosignatures” for scientists to detect. By looking at how microbes survive in extreme environments on Earth, scientists can explore the bigger question of how life could sustain itself on other planetary bodies like Mars and Jupiter’s moon Europa.

Jim Green: The Perseverance rover is on its way to Mars. In February, it will land in a fabulous area called Jezero crater.

Jim Green: It’s right there on that edge between the land and the ancient ocean.

Jim Green: What do we expect to find?

Kennda Lynch: There could’ve been a habitable environment in that watershed area that picked up some potential biosignatures and deposited into the delta and got preserved.

Jim Green: Hi, I’m Jim Green, Chief Scientist at NASA, and this is Gravity Assist. On this season of Gravity Assist we’re looking for life beyond Earth.

Jim Green: I’m here with Dr. Kennda Lynch, and she is an astrobiologist and a geomicrobiologist studying life in extremes. She works at the Lunar and Planetary Institute in Houston, Texas. Welcome, Kennda, to Gravity Assist.
Kennda Lynch: Thank you. It’s so great to be here.

Jim Green: Well, your current research really focuses on the studying of paleo-lake basins here on Earth, and so that makes you a perfect expert to be involved in the Perseverance rover since it’s going to Jezero crater and land on an ancient lake basin, doesn’t it?

Kennda Lynch: I would say it makes me one of several really good experts that are really excited at the fact that we’re going to Jezero.
Jim Green: Well, let’s first discuss what we know about the Earth’s paleo-lake basins.

Kennda Lynch: Absolutely. What we know about Earth lake basins is a lot of our paleo-lake basins, these were ancient lakes that were, in a lot of cases, very, very big, very deep lakes. For example, Lake Bonneville, where my field site is, was an ancient lake of the Pleistocene era, and at some point, at one point, it was a thousand foot in depth. It was very big, very deep, actually freshwater lake. But, over time, because it was a closed basin lake and we had climate change, the lake started to dry out. It didn’t have any outflow, so everything just evaporated.
Kennda Lynch: There’s many of these across the world that we study. There’s the Great Salt Lake here in Utah. Death Valley also has paleo-lakes in it. The Salar de Uyuni in Bolivia also has one. We have one in China. We have paleo-lakes in China in the Qaidam Basin. So all these big lakes dried into these amazing playa environments where we have all of these lake sediments, we sometimes have occasional very, very shallow lakes that can develop in these environments, but we have amazing microbial diversity that can be found in these lake basin sediments after the lake went away, and that’s what I like to study.

Jim Green: Well, what exactly are you looking for when you get these sediments?
Kennda Lynch: We’re looking at a couple of different things. Initially, we wanted to just try to understand what these ecosystems look like. There really hasn’t been a lot of research, believe it or not, in these kind of systems because people didn’t really understand that they could be very, very rich in life. So the first thing we do is we do a lot of heavy biology, so a lot of looking for DNA and trying to understand what we call the phylogeny. Who’s there, how diverse they are, what does the ecosystem, what do the microbial communities look like? A lot of the first work that I did was understanding who’s there and what they look like.
Kennda Lynch: Then the next thing we look for is how are they interacting with the environment, how are they interacting with the geochemistry, how are they living there, what are they eating, what are they breathing, how are they getting their energy, how are they interacting, all of these kinds of things. So we look for that, and we try to understand that.

Jim Green: Can you tell me about a particularly memorable experience you had out in the field?
Kennda Lynch: Oh, wow, there’s so many. I’m going to give you two quick little ones. When we were at the center of the basin where there’s an actual well that my colleagues had put in permanently, we found a little mouse hanging out in the well, just hanging out in the shade of the well, and he had somehow gotten onto the playa. But he was hanging out there during the heat of the day. Well, the next day, we came back to one of my boreholes that was about a mile away. That mouse was in my borehole using the borehole as shade. So he had, overnight, had gone that whole mile, mile and a half, and was using our borehole as a refuge for the day heat. It was very cute, and we got pictures of it.
Kennda Lynch: Then the second memorable experience was when we got our UTV stuck in some of the playa mud. That was a challenge.

Jezero Crater, Mars 2020's Landing Site

Jim Green: You know, the first mission to find perchlorates on Mars was Phoenix, but even Curiosity has confirmed that there are perchlorates but not everywhere. What are perchlorates, and tell us a little bit about how are they important?

Kennda Lynch:
So perchlorates are what we call chlorine oxyanions. It’s a chlorine atom surrounded by four oxygen atoms, and it’s a really, really, really big oxidizer very similar to oxygen, so it gives the same kind of energy release that oxygen does. In fact, here on Earth, we use perchlorates as part of solid rocket fuel because when you light it up, it really gives a lot of energy that helps our rockets take off. People experience perchlorates every day in things like firecrackers. But we also know that perchlorate occurs naturally on Earth and, of course, on Mars. On Mars, we see more perchlorate on Mars than we see anywhere on Earth, and so it’s this incredible potential energy resource that life could use to generate energy and sustain an ecosystem.

Kennda Lynch: The other reason, which is not as exciting, but perchlorates on Earth, they can be toxic to humans, so we want to understand perchlorates so that we can make sure that it doesn’t affect our astronauts when we send them to Mars, so that we can mitigate the perchlorates and make sure that they don’t make our astronauts sick when we send our first human mission to Mars.

Jim Green: This field site that you went to, the Pilot field site, where is it at, and why did you choose that?
Kennda Lynch: So Pilot Valley Basin is a part of the Great Salt Lake Desert, which basically encompasses most of northwestern Utah. Basically, once you get past Salt Lake City, the rest of it is the Great Salt Lake Desert, and Pilot Valley is a sub-basin of that desert that actually because of how it’s nestled in between two mountain ranges is off on its own, it’s all Jeep roads to get there, it’s not that easy to get to. So there hasn’t been a lot of anthropogenic input onto Pilot Valley, whereas other basins in the Great Salt Lake Desert, they do a lot of salt-mining, a lot of economic geology. Pilot Valley has been off on its own and pretty much left pristine.
Kennda Lynch: How I found this environment actually very much relates to the Phoenix mission and our discovery of perchlorate. I was working with Dr. Sam Kounaves, who was a Co-I on Phoenix at the time and is one of my long-term mentors and definitely a wonderful, wonderful scientist. I was working with him on his sensors, his wet chemistry sensors, and during the Phoenix mission, I was in grad school and he called me. He called me and I think he actually might’ve called me from JPL and said, “Kennda, do you know anything about perchlorate,” and started me down this road about looking at perchlorate and microbes that can use perchlorate.
Kennda Lynch: The following summer, I was driving to Ames Research Center to start my Harriet Jenkins Predoctoral Fellowship summer portion. I was driving through Utah and looking at the Great Salt Lake Desert, and I had done all this research about perchlorate and where it lives in the Atacama, and I’m looking at the Great Salt Lake Desert and I’m like, “I wonder if there’s perchlorate here. That would be kind of a neat environment to study.” So I wrote a little mini-proposal to get the summer internship money the next summer from my school, and I went out and did a field expedition, and literally it changed my whole direction of my dissertation. It just keeps getting more and more interesting and more and more fun every time we go out there.

Jim Green: Well, there are other places in the solar system that we were thinking of looking for life, like Europa. Are you doing any research on Earth that relates to Europa?
Kennda Lynch: Definitely some of the work that we’re doing in my basin. One of my recent research papers that just came out last summer, where we basically documented our first discovery of perchlorate reducing microbes cohabitating in an area there was actually also naturally occurring perchlorate, something that’s never been documented before. So, now, we have a relevant Earth analog ecosystem to learn about how perchlorate reducing microbes can live in what on Earth is an extreme environment but would be more of a normal environment on Mars or Europa, living in a brine or a salty environment in Mars and Europa.

Jim Green: I remember that once you did a talk called “All Life Poops.” Does that mean that even bacteria has waste, and could we find traces of that in any of the samples that we bring back, whether it’s from Mars or flying through the plume over Europa?
Kennda Lynch: Yep, indeed. All life takes in energy and creates waste products or, for lack of a better word, poops, and it is indeed often these waste products that turn into biosignatures or possible biosignatures of life. For example, we’re breathing poop right now. We are breathing tree poop. Oxygen is tree poop. So oxygen, molecular oxygen, is a potential biosignature that we look for in extrasolar planets. So, absolutely, poop can be a biosignature.
Jim Green: Wow. You’re absolutely right. I just never thought of it that way.
Kennda Lynch: I know. It’s so funny. When I show kids, some of them go… and try to hold their breath. They’re like, “I don’t want to breathe poop,” and I’m like, “Don’t have a choice.”
Jim Green: You need that. You need that, okay?
Kennda Lynch: You need that poop.
Jim Green: That’s what makes different types of life coexist together, and in fact, we need that oxygen production from our plants.
Kennda Lynch: Yep, absolutely.
Jim Green: Just as they need the CO2 production that we create.
Kennda Lynch: Yep.
Jim Green: So that’s what creates a biosphere is that important relationship between the different species of life.
Kennda Lynch: Exactly.

Jim Green: So, Kennda, what about Perseverance is getting you really excited? When that lands in Jezero crater, what do you want it to do?
Kennda Lynch: I am so excited about what we call the bottomset deposits. These are these really, really fine deposits, really fine grains. They’re usually mostly made up of clays and carbonates on Earth. They’re really small particles that deposit in the lake basin and at the front of the delta that can make these great sediments where we can preserve organics and biosignatures. I am so excited for Perseverance to go and start taking a look at those particular deposits in the crater.

Kennda Lynch: We’re going to have some of the best chances of finding preserved organics in those deposits because that’s an environment on Earth where those kind of lake bed deposits or delta deposits, we know we get a lot of concentrated carbon that gets preserved and stabilized very well in those kind of deposits. So I’m really excited about the bottomsets.

Jim Green: It’s right there on that edge between the land and the ancient ocean, and this river was dumping into that when this impact occurred and created this huge crater we now call Jezero.

Jim Green: Would you think we might be able to find some biomolecules if you’ve got complex carbon, a material that we’re also finding? Is there a hope that we could do that?

Kennda Lynch: You know, I really do think so because what’s really amazing about these bottomset deposits is that because of the lake environment and the fact that we have this delta, it could come from potentially different habitable environments within the Jezero crater area. It could’ve come from up in the watershed, and the watershed is that area where all the water that developed on Mars in that region flowed together into one big river or stream and deposited the water and the sediments that created the delta. There could’ve been a habitable environment in that watershed area that picked up some potential biosignatures and deposited into the delta and got preserved. It could’ve come from the lake itself.

Kennda Lynch: Or it could’ve been preserved from a transitional habitable zone like I study, this subsurface environment where there’s groundwater moving through these sediments after the lake’s gone, and there could’ve been a subsurface ecosystem that could’ve lived there for a time before water retreated even deeper into Mars, and there could’ve been life that could’ve left some potential biosignatures there. So we have three different potential habitable environments that could’ve left biosignatures in these deposits, so I’m so excited to see what we can find out when we get samples from there.
Jim Green: You bring up something I hadn’t really thought about, but, indeed, with that lake over time being eroded away and then the atmosphere becomes very thin, that’s going to draw groundwater out.
Kennda Lynch: Yeah, especially since we know now that groundwater was a significant part of the hydrology on Mars, that that’s going to be a really important environment for us to start to try to understand. Again, I’m so excited to see what we’re going to be able to find out.
Jim Green: Well, you’ve also been involved in education and diversity efforts in what we call science, technology, engineering, and mathematics or STEM as an acronym. Can you tell us a little bit about what your efforts are and what you’ve been doing in this area?

Kennda Lynch: I am a lifetime member of the Girl Scouts. I was my mom’s first girl scout, and my mom worked on the professional staff, so I grew up in girl scouting and giving back and reaching out and educating. Yeah, I’ve just been doing it my whole life, all through college and undergrad. I have mentored so many students while working as a full-time engineer. I’ve done a lot of school presentations. And in grad school, I’ve mentored students and taught classes.
Kennda Lynch: Right now, I’ve got three students I’m mentoring, two directly at the LPI, one indirectly with a colleague who’s asked me to mentor one of their students of color, and I’m very excited to be able to do that. I also do a lot of STEM outreach with our education and public engagement department here at the Lunar and Planetary Institute.

Kennda Lynch: I’m a Ford Fellow, so I interact with that community quite a lot and try to help with efforts to increase diversity, equity, and inclusion across the space sciences and just STEM in general

Jim Green: Well, I personally want to thank you for all that activity. I enjoy talking to the public and talking about the fabulous science that we do. You just can’t stop me, and I’m just delighted that you’re doing the same. Well, Kennda, I always like to ask my guests to tell me what was that person, place, or thing that happened that got them so excited, that enabled them to become the scientist they are today, and I call that a gravity assist. So, Kennda, what was your gravity assist?
Kennda Lynch: Well, there was so many people along the way, I can’t recount them all, but what I will tell you is that my biggest gravity assist, the one that just makes me well up right now is that my first summer internship at Kennedy Space Center, I was a space life science training program participant. I won’t give you a year, but it was way back when, when the shuttle was flying. It was my first entry into the space world that I’d always wanted to be a part of, and I got accepted into that program. The biggest gravity assist for me was seeing my first shuttle launch.

Kennda Lynch: They let us go out to this place called… They let us go out and watch the shuttle launch at Kennedy, and I got to see one of the shuttle launches, and that first shuttle launch and watching that spacecraft go into the air and hearing the noise and watching the alligators jump out of the water because it was so noise for them was just so inspiring and just… I couldn’t believe that at 20 years old I was there, and I could be here and that I was a part of the space industry finally. So that was definitely one of my biggest gravity assists that kept me going.
Jim Green: Well, that was wonderful. Well, thanks so much for joining me today. I’ve really enjoyed our discussion.
Kennda Lynch: Me, too. Thank you so much for having me.
Jim Green: Well, join me next time as we continue our journey to look for life beyond Earth. I’m Jim Green, and this is your Gravity Assist.


Lead producer: Elizabeth Landau

Audio engineer: Manny Cooper