Mars Life Explorer: The search for extant life on the red planet

Sarah Al-Ahmed: Is there life on Mars? Only science will tell. This week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society with more of the human adventure across our Solar System and beyond. Today we're diving into an exciting new mission concept, the Mars Life Explorer. Amy Williams, the science champion that helped make this mission a priority in the most recent decadal survey is here to explain why this mission is so vital and why we hope to send it to Mars sooner rather than later. Then Bruce Betts, the chief scientist of The Planetary Society, will join me for What's Up and a celebratory conversation about reestablishing contact with our beloved Voyager 2 spacecraft. Back in 1975, NASA launched the Viking 1 and 2 missions. These twin spacecraft, which each consisted of an orbiter and a lander, were poised to give humanity the most comprehensive look at the red planet yet. Before the landing of Viking 1, the only mission to operate on the surface of Mars was the Soviet Union's Mars 3 spacecraft, which touched down just a few years earlier in December 1971. Unfortunately, Mars 3 stopped working just two minutes after it touched the surface. But Viking 1 transmitted its first image from the surface of Mars on July 20th, 1976, and it was a site that no human had witnessed in such detail. We saw Mars as it truly was, a red and desolate landscaped, littered with rocks, but also infinite opportunities to learn more about our place in the cosmos. While the Viking landers recorded temperatures and analyzed the iron-rich Martian ground and conducted a bunch of chemical experiments, it was the landers in situ experiments to detect life that still puzzle scientists to this day. The mission introduced water with nutrients and radioactive carbon to Martian soil samples. If life existed, the hypothesis was that the Martian microbes would consume the nutrients and emit radioactive carbon. Strangely, that's exactly what the instruments detected, but when the soil was sterilized, the results vanished and the mystery deepened. Later missions discovered the presence of perchlorate in the Martian soil, leading to debates about whether this compound might have caused the positive readings as opposed to actual life. The results from Viking's life detection experiments remain inconclusive to this day, but the proposed Mars Life Explorer mission hopes to carry on that legacy. The Mars Life Explorer or MLE mission was announced as a priority in the most recent decadal survey, which was released in April 2022. The decadal survey is a report prepared every 10 years by the National Academy of Sciences, Engineering, and Medicine at the request of NASA. It represents the consensus opinion of leading experts in the field, specifically addressing the most pressing scientific questions facing the space community, and outlining a priority list of missions that can answer them. There are many missions on Mars trying to assess its past habitability, but MLE, like the Viking landers, hopes to take it a step further and answer the question of whether or not there's still life on the red planet to this day. Our guest today is Dr. Amy Williams, the science champion for the proposed Mars Life Explorer mission. She's an assistant professor of geology at the University of Florida with a specialized focus on the formation and preservation of biosignatures in terrestrial environments. She has been instrumental in the research that could reveal clues to potential life on Mars. Amy's been a member of the NASA Curiosity rover science team since 2009. She also joined the Perseverance team as the newest Mars rover banks precious samples of Martian material for future return to Earth. Her work with Curiosity's Sample Analysis at Mars or SAM instrument has allowed her and other scientists to explore the distribution of organic molecules on the Martian surface. Amy's research bridges the intricate connection between microbial life, the geochemical environment, and the rock record here on Earth. All of these things could help us recognize habitable environments on Mars and other worlds. She's here to tell us more about the MLE mission. Hi, Amy. Thanks for joining me.

Amy Williams: Hi, Sarah. Thanks so much for the invitation.

Sarah Al-Ahmed: This is a very nerdy thing to say, but I always love an occasion to dive into the decadal survey. I mean, there's so many wonderful proposed missions in there and I'm really excited to talk to you about this because it's cool to go to Uranus. There's a lot that we don't know, but finding life on Mars would mean so much to me and so many other people.

Amy Williams: I mean the kid in me, that's been my goal the whole time. So it's particularly exciting to be able to champion a mission concept study like this.

Sarah Al-Ahmed: What does that mean? You were the science champion for this proposed Mars Life Explorer mission. What is that role like?

Amy Williams: The science champion when you're already on the decadal and having these mission concepts studies go through the process is in some ways like pulling the short straw, but it's the best short straw ever. So the way that that works is that the decadal has the opportunity to identify studies that may have been overlooked or topics that have been missed during the course of studies for other mission concepts that feed into the decadal. And of course, this extends far beyond the Mars mission concept studies I went through to our whole Solar System. And so what we ended up doing was deciding that a mission concept study that had sufficient fidelity for science objectives, instrumentation and costing that could explore the possibility of extant life on Mars was really missing from the portfolio of options. And so in the end, it's a group effort and as science champion, again, it was sort of the short straw in that I became the point person, but there's certainly so much effort that went into it from folks on the decadal Mars panel as well as all of our study partners with JPL and beyond.

Sarah Al-Ahmed: How does it go from being this proposal that you submit to actually getting prioritized in the decadal survey?

Amy Williams: So I will start out by saying as science champion, I did not know that MLE, as I like to call Mars Life Explorer, had been prioritized until the decadal was released. So it was as much of a surprise to me as to anyone else, although I had played such a role in shepherding it through this process. So what we do is that each panel was able to recommend to the decadal steering committee new mission concept studies to supplement those that were already in existence. What we ended up as a panel discussing were a suite of concepts that coalesced into the recommendation to study Mars Life Explorer. What we ended up doing was doing the study and then it had to go through what we call trace, which was sort of this independent costing and risk study that was meant to say, "Did your mission concept study cover all of your bases and does it really fit in your cost box and your risk profile?" And so what ended up happening is that all of basically the New Frontiers missions as well as Mars Life Explorer and the other Mars mission concept studies went through, were ranked and prioritized by the steering committee. And the Mars Life Explorer mission was the one that was ranked as the highest priority next medium-class mission for Mars after Mars Sample Return.

Sarah Al-Ahmed: That's got to be so exciting to get the news along with everyone else. Do people just start calling you randomly like, "Did you hear?"

Amy Williams: It's an interesting situation to be in where as a member of the decadal, I'm bound to make sure that our cohesive decadal story comes together, comes from my mouth. The private discussions have to stay private, the discussions about what really goes into something like this. So it's both exciting to have the opportunity to champion this mission both in the decadal process as well as afterwards now that it's prioritized, but it's definitely a team effort. And so I like getting the calls, but I also want to share the wealth because this was a humongous team effort.

Sarah Al-Ahmed: Absolutely. I went as far as downloading the actual white paper on this and looking through it. It is a massive amount of effort that you and other people had to put into just proposing a mission like this. But I'm glad because we've dedicated so much time to studying Mars, thinking about its past habitability, but we've had so few opportunities to search for existing life there now, this extant life. So what are the primary objectives for the Mars Life Explorer, or MLE, which I think is a much cuter acronym than most missions get?

Amy Williams: I know, I know. I'm a big fan of it. So yeah, our objectives for this mission, and I like to step back with the whole arc of Mars exploration. We have Viking, we have the life detection experiments that flew on board Viking and the discussion that surrounds the outcomes of those experiments. So I think that a large portion of the community has come to say that those experiments would've benefited from the knowledge that we've gained in those subsequent decades. So perchlorates are an issue for looking for organic matter and metabolisms the way that those experiments were meant to run. We didn't know to expect that when we sent Viking. And so thinking about the whole arc of Mars exploration. You have Viking, you take a step back and say, "Okay, Mars is not quite what we were expecting, so how do we start exploring it?" You look for the water with the Mars Exploration Rover, you look for the carbon with Curiosity, and then you look for evidence of ancient life with Perseverance and you send those samples back to enable us to do really profound and I think paradigm shifting science, but that still leaves you with that next step. We're looking for ancient life now, how do we look for modern life? And I think what's really important is doing that in the era before we send humans to Mars, which is certainly a priority. And there are so many, I think, variables in that next major leap for humanity that we really need to invest in understanding whether there are still not only habitable niches on Mars, but inhabited niches. So that's a whole big round wave of me coming around to our science objectives for MLE. The first of our four objectives is to search for evidence of extant life. So that would be looking for organic molecules, non-equilibrium gases and isotopic signatures that could be indicative of a biological origin. Now, short of finding your evidence for life, which of course would be profound and incredible and requires so much confirmation, secondary confirmation, there are so many other things that MLE is able to do. MLE is a life detection mission but so much more because we're also looking at habitability of a particular environment we really haven't been able to explore before. And that is the near subsurface ice in the Martian mid-latitude. So with a two-meter drill, we would be able to assess the habitability of that environment, looking for the things that life as we know it needs to survive. And then once you have this incredible two-meter borehole, you can for the first time quantify from that down borehole thermo physical property suite, which we haven't done before. And this would be within ice and ice-cemented regolith. And then our fourth objective is what has actually driven one of the goals of lasting an entire Martian year, and that is to be able to determine the processes that preserve, modify and destroy ice in that particular environment. And so that would enable us to go through a full Martian year, look at how water flux from the subsurface in the atmosphere occurs and really help us to get better constraints on that kind of exchange in an environment we haven't explored before.

Sarah Al-Ahmed: Understanding those ices could be very key to understanding whether or not there's life on Mars currently, but also could deeply impact future habitability of Mars for humans. But when people come to me and say, "Are you excited about humans going to Mars?" I always try to take a step back personally because this question of whether or not life already exists there is so important to me, and it could be deeply impacted. If humans go to Mars before we actually answer this question, it could permanently change our ability to answer that. I don't think people take that into account very often.

Amy Williams: I mean, I know that the goal would be as minimal impact as possible. And when you say, when people ask, are you excited about humans to Mars initiative? The answer is yes, but... There's the excitement, but then there's also, I think about humans have not a great track record of when we explore new places, what that impact is on that new place. I think that even in the last several decades really, we've come to recognize that the human microbiome is a robust, diverse and resilient community of microbes, that we can do everything that we can to keep that from getting out in the wild as it is on Mars. And yes, the communities that could survive on the near surface, I mean it should be very limited to almost non-existent, but it's Pandora's box. You can't close that if you do let something out to the wild and it is able to evolve and contaminate the Martian environment with terrestrial life. So not to say one way or the other about the benefits and drawbacks of humans to Mars, but I think these are the things that I know people are thinking about and we should continue to think about to do this in the most responsible way.

Sarah Al-Ahmed: Absolutely. It would be a really beautiful thing to learn that maybe there's some connection between life on earth and life on Mars in the past, and I want to know these answers before we introduce complications to that.

Amy Williams: Yep, that's a good way to do it.

Sarah Al-Ahmed: Yeah, which is why we should prioritize missions like this. So I'm really glad that this is something that we're thinking about very carefully and already have some cool ideas about how to accomplish. Since we're already working right now to gather samples from Mars and bring them back to earth, why is it so important for us to also do this science at Mars? Like do in situ research? Why would these two things be different? We determine the answer to this question with those Mars samples?

Amy Williams: No, we can't. And that's one of the big things that I do like to remind folks of is that Perseverance's collecting samples for return to earth with Mars Sample Return that could have the potential to house ancient life biosignatures, not modern. I can only imagine the concerns that there would be about trying to bring back something that might actually be alive. That is a whole nother podcast for you to speak in to. So the thing about Mars exploration that I like to point out, especially to my students, is imagine that you are the Martian and you're coming to explore Earth and you land in the Atacama Desert, or we're at the University of Florida, so land in the Florida Panhandle. What you see is a snapshot of such a limited environment that trying to draw conclusions for an entire planet based on those snapshots, I mean, we must recognize how limiting that is. So when we talk about in situ exploration, bringing samples back and getting the insight that we're going to get from Mars Sample Return, like I said before, I think it will be profound and paradigm shifting and beyond informative, but you are getting a snapshot of an ancient, aqueously impacted environment. You are not looking at ice-cemented anything. You're not looking at the environment that MLE would look at. And so really it's a case of every data point is incredibly valuable in our exploration of other worlds. And if you think back to Viking, we sent these missions, we landed, we successfully scooped up the regolith, and lo and behold, there are perchlorates that actually messed up our experiments. Imagine everything that we learned with every single mission, all of the detail and nuance that we never expected or anticipated or didn't realize how important it was for another world. All of that feeds into every mission that we run to any planetary body. And so that's why I think it's important. As we continue our exploration of Mars, you have to have in situ exploration and you have to have it in different locations, so you get at least a little bit of a better idea of what that breadth of environment really is.

Sarah Al-Ahmed: I love that you keep bringing up Viking because the results from those tests were so interesting, and for literally decades, I've been wanting someone to go back and try to attempt something similar. How has our technology evolved since then that's going to allow us to really kind of determine more of these answers? Because I'm not even sure we understood at that time that even on Earth there are perchlorate-eating microbes and stuff. Our understanding has advanced so much in the last few decades.

Amy Williams: Absolutely. So I don't even think in the '70s... We are just starting to understand that archaea are a separate domain of life. We weren't sequencing microbes yet. There's so much about our understanding of the diversity of life as we know it just on earth. We've come so far in subsequent decades. I think one of the really neat things about the MLE mission is that we've built this instrument agnostic mission. Meaning that to meet our requirements, fit in our cost box, understand our risks, all of that, we leveraged a lot of really high-heritage instruments and landing systems and the whole nine yards for MLE with the understanding that in the subsequent decades until MLE would launch, you're going to see instrument maturation. You're going to see improvements in our technology that may enable us to do much more than we anticipated when we built this mission concept. One of the really cool things for me that sort of links all of this Mars exploration is that we had to study a particular suite of instruments just to see where you are with risk and costs and weights and energy and all of that. And so, one of the boxes that we fit into was flying something that has a mass spectrometer. So we've seen mass spectrometers on Viking, on Curiosity. There's one flying on ExoMars. There's one going to Titan. And of course, this technique has been used in other Solar System exploration. And so it's fulfilling to me in some ways that you're seeing a technique that we leveraged with Viking and got really interesting results that necessitated a lot more exploration for us to really understand why these things turned out the way that they did. And now you would be sending what is the great-great-great grandchild of those technologies on Mars Life Explorer to again look for evidence of extant life, but with so much more information about the environment, again, the nuance of the geochemical system that we just didn't have previously. So we're leveraging high-heritage instruments, but MLE was built to be a mission that can accommodate new instrumentation, new techniques that might enable us to search for extant life inhabitability in these shallow subsurface ices.

Sarah Al-Ahmed: So we can't actually say which specific instruments are going to be on this, but what are kind of the instrument categories that are going along with us to help us do this research?

Amy Williams: I talked about we have these four objectives. There were a couple of different baselines that we could have followed, and we picked one that was studied, but we have an idea of how all of these others, both the baselines and our threshold mission would fit together. And so for the intent to look for extant life and modern biosignatures, we talked about flying an instrument that can look for organics. So that would be like SAM or MOMA or drums, maybe pyrolysis-GC-MS with laser desorption for those who fluently speak mass spec. Taking evolved gas analysis, which is something that's flown on multiple missions. Having a way to measure trace gases, so like a tunable laser spectrometer, and then a way to measure isotopic signatures as well. So again, with that TLS, tuneable laser, we'd be able to do that. So you would be flying something like drums or MOMA to accomplish several of those goals. Those are names of instruments, but they're truly instrument suites that can accomplish all of those goals. And then when we want to look at habitability in the subsurface down to those two meters, we're talking about ways to look at mineralogy and amorphous phases, elemental chemistry in organic and small organic ions. So you're looking at something like the CheMin instruments on Curiosity. So there's instruments like CheMinX, which is being developed or a new version of MECA, or using evolved gas analysis. So it's really nice that we have all of these instruments that have flown or a very high TRL because they are just on the cusp of being ready to offer new opportunities for instrumentation. One of the things that should be explored before MLE would fly would be this two-meter drill. So there's a two-meter drill on ExoMars, and we can talk more about the benefits of getting into the subsurface and away from that harsh environment in the Martian surface. But with MLE, one of the really neat things is that we would have these ways to measure temperature and conductivity profiles down the borehole, downhole imaging, just opportunities that we haven't had to look into the subsurface of Mars. And then our fourth objective, looking at the modern climate, looking at water flux between the subsurface and the atmosphere and looking at weather for a year. We're flying basically like a version of Meta with temperature and pressure sensors and a sonic anemometer. And so we have all these opportunities to leverage these high-heritage instruments to accomplish these objectives. But in the full report, we highlight a suite of things that you could do, you could fly that would fit in the box, whatever that cost and size and energy box is.

Sarah Al-Ahmed: Is this going to be one of those missions that's powered by solar panels?

Amy Williams: Yes. Yes. So one of the things about keeping your costs down is flying with solar panels. And I was rereading the report recently, you know when you turn in your dissertation and then you're like, "I can't look at this again for a while."

Sarah Al-Ahmed: Yeah.

Amy Williams: This is maybe how I felt a little bit about the report. So reading through it again, and it said something about, "As the current InSight mission has taught us," and I was like, "Oh, InSight."

Sarah Al-Ahmed: Oh, RIP InSight.

Amy Williams: But it's true whether it's a current or former mission, that InSight in Phoenix has taught us a lot about how to have static landers, how to protect our energy resources. So there's been discussions about how you might modify something like an InSight platform in order to be able to clear your solar panels. So yeah, this is a solar-powered mission, and there's this trade between how high of a latitude would you land at versus how big do your solar panels need to be in order to enable you to survive a full Martian year. So the objectives A, B, and C, which is modern life, habitability, down borehole, thermo physical properties, all of this can be done in a matter of months in the way that we studied this mission concept. But that full year with our weather and climate and water vapor monitoring system is going to give us so much really granular insight that we just couldn't get otherwise. Rovers are great for roving, but as I hear from my environmental atmospheric colleagues, they say, but then you're getting information from different places all the time, and sometimes it can be hard to connect those data points to give you a sense of how things are changing in one particular location.

Sarah Al-Ahmed: And I think a lot of people were really sad when the InSight mission stopped working, but I just want to remind everyone it worked as long as we planned for it to work. You don't necessarily have to nuclear power everything. Solar panels are great, and if they get covered in dust, we planned for that. So that's okay.

Amy Williams: I know. Didn't InSight go several extended missions? Not only did it go as long as we planned, it went longer. And that is one of the hard things I think about mission work, at least in my experience, is these missions have lifetimes and it's tough to see them get to the end. And it's also tough... We were getting really incredible seismic data right at the edge there, so we always want more. I think it is in part, it's just maintaining expectations. This mission has a lifetime, and we're just going to have to meet that as best we can.

Sarah Al-Ahmed: Yeah. But I'm all down for anthropomorphizing these spacecraft and getting attached to them. It's okay to feel sad when they stop working, but it's okay.

Amy Williams: Yes, yes.

Sarah Al-Ahmed: We'll be right back with the rest of my interview with Amy Williams after this short break.

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Sarah Al-Ahmed: There are some very specific environments that we're looking at for this kind of spacecraft. Do we have any idea of landing sites that could be good for this?

Amy Williams: There are a couple of options and regions that we have talked about in the mission concept study, and the biggest thing would be finding an area where water ice is within a meter of the subsurface, and we have a two-meter drill. So the intent would be you'd have at least a meter of ice-cemented regolith that you would be able to drill through to get at our objectives for the mission. So there are a couple of different places that could be explored. We talked about places like Arcadia Planitia, these kind of mid-latitude regions and some of the indicators that we would have ice within a meter of the subsurface. So first there's been really successful THEMIS modeling that's shown us where ice should be within a meter of the subsurface across wide expanses of the Martian mid-latitudes. And we also have actually orbital information, so images where impacts have actually exposed ice in the subsurface. And so you have these little windows of ground truing to help us understand what the distribution of that subsurface ice is. So there are a couple of different places that have been identified, but we did not focus on this is a landing site that we must go to because there is a lot of opportunity and the latitude and where we would land.

Sarah Al-Ahmed: Are we aiming for places with ice because we're just looking for life as we know it, which requires water?

Amy Williams: So the other fun thing that we put into the mission concept study is that there are of course, plenty of places that have been proposed for the search for modern life on Mars. The deep aquifers, even higher latitude sites, like think about where Phoenix was, or lower latitude sites with signs of recent water [inaudible 00:30:44]. So the mission is not meant to preclude going to one of these sites instead, but we basically had to select a design point to complete the mission concept study. And so we went with mid-latitude ice. It's something that we haven't done before. It's leveraging instruments and technologies that we know work or we're about to fly in the cases like this two-meter drill where ExoMars will have this experience that we can leverage for MLE. There are lots of places one might look. When you're thinking about habitability, having liquid water does appear to be pretty important for life as we know it. And so with MLE and the mid-latitude ice, it's not that we expect to see any melt in those regions, but the modern mid-latitude climate seems to control sort of an unstable nature to the subsurface ices. And so that actually could lead to putative episodic melting. Perhaps you have life that would normally be in the spore-like state and it can reanimate when there's liquid water and then it would go back into a dormant state. So these are all just the possibilities that have been kicked around about whether organisms could survive over long timescales in a dormant state. And would we be able to then detect them with MLE? And that's the hope and the goal.

Sarah Al-Ahmed: In a recent week, I was actually talking with someone about the axial tilt or obliquity of Mars and how much it changes over time and how it could lead these places with ices to melt and that could have all kinds of interesting impacts on surface features, but also on this possibility for life. And even just this last week, I think it was some organism on earth they found that had been frozen in the ice for like 40,000 years and they just kind of melted it out, gave it some heat and some water, and it was fine.

Amy Williams: Yeah, they were worms too. I mean, we're not even talking about bacteria or archaea. We're talking about complex multicellular eukaryotes that are reanimated after 40,000 years. It's incredible. That's where, as an astrobiologist, every time I hear something like that, yeah, it's really cool and exciting, but there's a part of me that's like, "Yeah, I'm not surprised." Maybe a worm, I'm more impressed I would say than I'm when I hear about a bacterium. The ability of life... As Jeff Goldblum said, life will find a way. I think that our eyes are still being opened to the ability of life to survive and thrive in really incredible environment.

Sarah Al-Ahmed: But in order to get to this place and actually test the material to see if there's any life, we have to be able to drill down into this ice. And we have attempted to drill on Mars before. We've been successful with some instruments, but the most recent attempt with the InSight mission did not go according to plan. We tried to hammer down into the soil and it just resisted all of our efforts. So what kind of lessons did we take from that that could help us in this case?

Amy Williams: Yeah, this is one of the questions that I've gotten recently, and the short version is this two-meter drill is totally different design, technology, and implementation than the mole was. Sometimes we do technology demonstrations and they're demos for a reason. You expect them to do something and sometimes they do fabulous, and sometimes Mars throws a curveball at us. With the MLE two-meter drill, this is very similar to ExoMars. And so this is a technology that in some ways leverages the drilling capabilities that we've developed for Curiosity, which is only maybe six centimeters into the subsurface. We're feeling very confident because again, you're leveraging really high-heritage technologies that have been tested in a variety of extreme environments. So we have every expectation that you would be able to get that two-meter drill down to its full depth. With MLE, what we built in is a couple of different degrees of freedom. So that say, where you land, and again, this is the challenge for the lander, where you land is where you're. But with these degrees of freedom, we can actually pivot the arm around, the drill arm, so that you can... With theater's big boulder in your way, you have quite a bit of space to move so that you could access and get a full two-meter drill into the subsurface.

Sarah Al-Ahmed: And I imagine too, that the material you would be drilling into would be very different from the material that InSight encountered because you're specifically targeting ice regions. So we know what ice is like here on earth. Maybe that'll make it a little bit easier to do experiments.

Amy Williams: Yeah. And some of the tests that have been done with specifically these two-meter drills and the way that they're designed, they take them down to the Antarctic dry valleys and drill into this material. That's what we expect that subsurface to be like on Mars. So it lends a lot of confidence to the ability of these systems to really be robust just to survey that environment and be very successful.

Sarah Al-Ahmed: I read that this is a rotary hammer drilling technique. How does that work?

Amy Williams: Anyone who's done a home improvement work might be familiar because you can a variety of this that's meant for terrestrial work, but it has both a hammering capability as well as a rotating capability. So it's meant to help you get through harder materials. It's like what we see, especially on Curiosity or if you're coring with Perseverance where we have the ability to dial up basically the effort that goes into drilling through a rock. You don't want the rock to win because you've broken something on your instrument or on your rover or your lander, but we have the ability to... If you have drill through a rock, unfortunately to get to two meters depth, you would be able to dial that up and penetrate that material. And then if you're going through ice-cemented regolith, you would hope that that would be a little bit more giving to the drill system. So yeah, rotary percussive is just a way to accomplish several different ways of getting into your full core depth.

Sarah Al-Ahmed: This is going to be the deepest we've ever dug into Mars, right?

Amy Williams: Yeah, yeah. So with ExoMars going earlier and of course assuming all goes well, yeah, then the two meters would be the deepest that we have accessed into the Martian subsurface. The difference of course between ExoMars and MLE being the kind of substrate and the materials that we're trying to access, although of course the search is filled for life. And I do like to bring people back to Curiosity and the first time that we drilled into the subsurface there. And so this was at the John Klein area, this was at the foot of Mount Sharp. You tell someone to picture Mars, they're going to picture a red ball, a red planet, oxidized iron. And all of our experience and expertise led us to think you're going to drill down into this oxidized red material. And one of the coolest things is just within the first few millimeters of getting into the subsurface, we got into gray reduced rock. So that oxidized red Mars, the red planet, it's just a veneer in so many places. It's just really skin deep for a lot of regions of Mars. And so think about how our whole understanding of Mars changed within a couple of centimeters of drilling of subsurface and extrapolate that to what we're going to be able to learn by going two meters into the subsurface. It's going to be amazing. And one of the cool things about going down that deep is that you are looking for materials, organics, minerals, things that are effectively protected from the harsh radiation environment at the surface. So we know that the radiation environment is destructive to organics. We know that there are some organics in the near surface that do survive. We've detected them with Curiosity. And so, one of the questions is how much better protected are they going to be at one meter's depth, at two meters depth? Are you going to be able to see more complex organics that can be origin diagnostic? Meaning can you tell that they came from life or that they came from macromolecular carbon from a meteorite buried for 4 billion years? These are the kinds of things that we would hope to be able to address with that down core sampling scheme that comes with Mars Life Explorer.

Sarah Al-Ahmed: When we do actually start testing these, say we did find some cool signature that could indicate life. How do we know that we didn't accidentally just bring some hitchhiking microbes along with us?

Amy Williams: That is always the concern, isn't it? So we are following the planetary protection requirements that we've used with Phoenix with a bio barrier when you're accessing materials, as well as the level of stringency required for Mars Sample Return so that you are quite, quite, quite confident that you are not contaminating your sample with terrestrial life. When it comes to organics, that's one of the challenges of getting something organically clean. It can be extremely difficult. So not only do we not want to contaminate Mars with terrestrial microbes, but when you're trying to collect a sample of something and say, these organics that we see are indigenous to the rock and not from something we've introduced, we have several steps to make sure that that's the case. And that can include solvent washing and radiation and different ways to remove not only life, but organics from the interior workings of instruments to make sure that they are incredibly clean. And you can also carry blanks, different kinds of controls and tests to make sure that what you're detecting is indigenous and not something you brought with us.

Sarah Al-Ahmed: Once we actually do test these, if we did find something interesting, how would we verify that? If we just do it enough times, does it tell us that maybe this is real because I'm sure everyone would be really excited, but how do you know for sure?

Amy Williams: That is always the challenge, and different groups have tried to come up with ways to say, what would it take to feel confident in saying that you've detected evidence for life? I don't feel that there is a consensus among the astrobiology community much less the planetary science community. So of course, being able to repeat your experiments is one thing to make you feel a little more confident. Honestly, as science champion for this mission, if we picked up a hope pain or something that we only know it from life on earth... I don't even know right now actually what it would take for me to say, "Yes, definitely." I mean, that's so compelling, but the challenge that I face is that you can't step back from saying that you found evidence for life on Mars, right?

Sarah Al-Ahmed: Yeah.

Amy Williams: Because that's paradigm shifting. That means so much to so many people. That means that we're not alone in the universe. That means that there are multiple genesis of life potentially on these different worlds. What does that mean for life outside of our Solar System? There is so much to unpack in that discovery, and that's part of why we explore the way that we do, but you can't step back from it once you say it. And so to feel confident, I think that you do need repeat experiments. You might have to send another mission to further investigate, interrogate those samples. Maybe you send humans. There's a lot to unpack there. Luckily, it's for our upcoming generations of scientists and our upcoming instruments and techniques and flight systems that can enable us to do this hopefully with a conservationist mindset. Protect what's on Mars, protect ourselves, but also help us to understand are we alone in the universe? And looking at our nearest neighbors, I think one of the best ways for us to try to address that question.

Sarah Al-Ahmed: It's interesting because I wonder if we did find this evidence of life how it would impact future human exploration, because on the one hand, you could say, well, maybe we don't send humans for a while until we figure this question out. And on the other hand, you could say, humans might be able to do this science way better. Maybe we send them to figure out this answer.

Amy Williams: I'm so torn on it because it's such an incredible question to address. But you're right. Maybe it's like in 2001: A Space Odyssey. You're just like, "Don't go near Mars now that you know there's life there," that kind of thing. There's a lot to unpack there, and I do think that it takes really honest and candid conversations about what it means to find evidence for life beyond earth and how much we would want to engage with that life once we find it.

Sarah Al-Ahmed: Yeah, it would be a really sad thing if we accidentally went there and impacted life on another world in a negative way. We never want to do that. So I'm really glad that there's so much thought being put into it because if we did find life on another world, it would not only be the biggest discovery ever, but it would be really important to protect.

Amy Williams: It would be. And I always view this because we're still, of course, in the stage where we're not sure. We are searching for life beyond earth, but for me as an earth scientist, as an astrobiologist, what that means is in my search, it actually helps me to have this conservationist mindset for earth and life on earth. It helps me to recognize the uniqueness and preciousness and fragility of life on earth in my search for life beyond earth because we haven't found it yet. Doesn't mean it's not there, but it's not as ubiquitous, at least in our little neck of the woods here as it might've been. And so without that data point, it just makes me look back at our world. How do we preserve and protect what appears to be a very unique system?

Sarah Al-Ahmed: Absolutely. It's funny we're investing all of this time and energy into answering is there life elsewhere? And it's a big, big question, but it underscores how amazing our planet is and how much effort we should put into protecting life as we know it here. Because can you imagine if you're an alien and you came across Earth? It would be the biggest discovery ever.

Amy Williams: That's right. That's right. Flip it around in your head and think someone else is looking for life beyond their planet. What does Earth look like to them?

Sarah Al-Ahmed: There are a lot of different missions that are proposed right now. There are several other things that were also prioritized by the decadal survey, including the Mars Sample Return mission. And we're currently facing some issues with funding for Mars Sample Return, and I'm wondering if there's any concern that this lack of funding could also impact this mission or drive it into the future even further.

Amy Williams: Some of the things that were discussed, we talked about how would Mars Life Explorer operate? One of the big things is it's a medium-class mission, not a flagship. It was in part the timing, the cost and everything. It's designed to not launch. That means it's designed to not even move forward in phase A until we are moving out of peak MSR spending. Recognizing the importance of Mars Sample Return to not even the planetary community, but just science. It's incredibly important. So recognizing the need to honor that prioritization by the last couple of the decadal surveys while also keeping the Mars Exploration Program moving in a forward direction. So with MLE, one of the things that came out is that there would actually have to be a bump in our budget in order for MLE to fly. Certainly what we're hearing now with stresses about funding for Mars Sample Return, it does all kind of get passed down the line. You cut funding here, something else gets trimmed. Will MLE ever fly? One of the things that we pushed for, making clear in the mission concept study is the desire to perform this mission prior to sending humans to Mars. If we're looking at sending humans to Mars, we're looking... I think one of the more recent estimates would be in the 2040s. Then you're looking at launching in the 2030s for MLE and completing this mission before that happens. Then you're looking at phase A, stepping all the way back into what? 2028 maybe. So everything propagates downstream, doesn't it? So pushing MSR in one direction or the other certainly impacts the rest of the planetary science portfolio. Again, I can just say I recognize the importance of the science that Mars Sample Return is going to accomplish. And so my hope is that there's a way to enable science for everyone and to keep our science budget healthy and to keep our funding levels healthy, not just for our generation of scientists, but all the people who will come after us.

Sarah Al-Ahmed: I'm happy to work at an organization that literally spends most of our time gathering people together to try to advocate for missions like this, because it would be a phenomenal result if we could send this there and actually get the answers to these questions. And I guess the one bright spot is that if it gets delayed, our technology will get even cooler, so.

Amy Williams: That is a way to think about it. Yeah, it's always a balance of improving and maturing technologies versus how much further do you push these opportunities out, especially if you have something that's almost like such a big step in our timeline, like sending humans to Mars. So that again, is something you can't step back from once you do. So you need to make sure you cover all your bases before you take that next giant leap.

Sarah Al-Ahmed: Well, thanks for seeing that gap in our priorities in the decadal and stepping up to try to make this a priority because we need people to advocate for these kinds of forward-thinking missions that would completely be a paradigm shift for the way we think about ourselves and the worlds around us. Well, thanks for joining me, Amy, and for this really cool mission concept. And fingers crossed, everything goes well with Mars Sample Return, and then you can come back when we're actually about to launch this Mars Life Explorer.

Amy Williams: Would be incredible. I'd love to see MLE fly into the sky.

Sarah Al-Ahmed: Thanks, Amy.

Amy Williams: Thanks, Sarah.

Sarah Al-Ahmed: In some ways, I like to think that this question of whether or not life still exists on Mars is part of why The Planetary Society exists. Our co-founder, Carl Sagan, helped design and manage the Viking missions to Mars and choose their landing sites. But the cost of the Viking program, along with the Voyager probes that launched in 1977 almost ended space exploration as we know it. Policymakers in the United States perceived a lack of public interest in space, and they used this as an excuse to slash budgets. Can you imagine, no public interest in space? In a time where new space images beam to my phone from the Martian surface across a deep space network, it seems almost inconceivable. But that's why Carl Sagan, along with the NASA Jet Propulsion Laboratory director at the time, Bruce Murray, decided to build a grassroots advocacy group to prove that there was public support for planetary exploration. They teamed up with JPL engineer Louis Friedman, and on November 30th, 1979, they founded The Planetary Society. The rest as they say is history. But if the Mars Life Explorer mission does one day land on Mars, it will be because of space fans and advocates like you who helped keep the torch of space science and exploration burning. Right now there are a few space missions that could use your help, including Mars Sample Return. If you live in the United States and want to add your support to these missions, you can visit our action center at planetary.org/action. We have quick and easy forums that'll let you contact your representatives in Congress and voice your support for these missions in less than two minutes, and then you can go get yourself a little treat for being a good space advocate. Now, let's check in with Bruce Betts, the chief scientist of The Planetary Society for What's Up. Hey, Bruce.

Bruce Betts: Hello.

Sarah Al-Ahmed: Hello. I'm just in a really good mood because after weeks of not being able to communicate with the Voyager 2 spacecraft, we just got a signal back, so we're back in contact. I'm so excited.

Bruce Betts: Oh, it always comes back. It's like cockroaches.

Sarah Al-Ahmed: Like cockroaches.

Bruce Betts: Except good. I mean, that's kind of a big difference.

Sarah Al-Ahmed: I was really actually impressed when we lost contact with that spacecraft knowing that they had already built in a system that would automatically point back to Earth if we'd gone long enough. It's cool that we got contact back by August, but I could have waited for October happily. I mean, not happily, on the edge of my seat, but there was this moment during my first time at the Jet Propulsion Lab in Pasadena. They have this visual display that shows when information is coming down from spacecraft, and when Voyager 2 pinged back information, it was so slow compared to all the other data coming in. I literally watched that thing, pointed it out and just laughed my head off.

Bruce Betts: Yeah, amazing what a few billion kilometers will do for your data rate. It's just amazing of the low power transmitters and that they can communicate with it at all. I mean, it's just incredible.

Sarah Al-Ahmed: All right, let's move on to this week's random space fact.

Bruce Betts: [inaudible 00:53:08]. Oh, so I was thinking. I was thinking planets, Solar System, moons. What's the closest moon to its parent planet? It's Phobos. Phobos at Mars is the closest to its parent planet, just a mere few thousand kilometers, 6,000 something kilometers away, and which leads to all sorts of funny things, some of which I've talked about before long ago, but it's orbiting in about eight hours, and Mars rotates in about 24-plus hours. And so it actually, even though it is orbiting not retrograde, it functionally from the surface looks like retrograde. What am I saying? I'm saying instead of everything rising in the east like we're used to, it rises in the west and sets in the east because it's actually zipping faster than Mars is rotating, and it's pretty groovy. It's also inside... Because it's doing that, it also will meet a fiery fate in 50 million or so years when it enters the Mars atmosphere.

Sarah Al-Ahmed: We got some really great comments from people this week. Some people have still been sending in messages to our email, so thank you. I really like that. But we'll also be looking at messages that come in through our member community online for our episodes. I had to read this to you, Bruce, because we've just moved our trivia contest out of the show into our member community. As is tradition, Jean Lewin had to write us a poem, and this time it's about your trivia contest. So Jean Lewin wrote us: "Without a word, he ponders. Facts swim across his mind. Nothing passes past his lips, but we feel he seeks to find. A query for the masses no longer cast by pod; small, but still important. He smiles and gives a nod. Each week he posed a challenge, but a habit's hard to break. Does his thirst to pose a question that weekly trivia can slake?"

Bruce Betts: Wow, that's very cool. Thank you, Jean.

Sarah Al-Ahmed: Oh, I love it. And of course, as the show has already aired, our new space trivia contest and our member community has begun, this week we're trying something different with a multiple choice question, so good luck everyone. And the prize is really cool. I hope everyone enjoys this new iteration of the contest. I don't know if people know this, but we have 20 years of Planetary Radio shows just sitting around for free on our website. So if you don't want to scroll all the way back in Spotify, you can always go to our website, planetary.org/radio.

Bruce Betts: Cool. I will do that right now. I'll see you in several weeks.

Sarah Al-Ahmed: Just get lost. We should calculate that. How long would it take you if you straight binged Planetary Radio? How long would it take you to listen to the whole thing?

Bruce Betts: A long time.

Sarah Al-Ahmed: But all right, everyone, if you're enjoying the show, please take a moment to go online. Leave us a little thumbs up or a rating wherever you listen to the podcast. It'll really help us reach out to new audiences so they can enjoy the show along with us. And if you want to, please jump into our member community and send us little messages or email us at [email protected].

Bruce Betts: A thousand-plus hours. I mean, it's like half a work year.

Sarah Al-Ahmed: Yikes.

Bruce Betts: All right, everybody, go out there looking for the night sky and think about lying on the grass and the mild sunshine and rolling back and forth, scratching your back. Thank you and goodnight.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week to talk with the members of the team that detected water vapor in a planet-forming disk with the James Webb Space Telescope. It's a really cool result. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by our life-searching members. You can join us as we support the space missions that help us unravel the mystery of whether or not we're alone in the universe at planetary.org/join. Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is arranged and performed by Pieter Schloser. And until next week, ad astra.