Did we find signs of life on Mars?

- In the summer of 2024, NASA's Perseverance rover was exploring Jezero crater on Mars. - So you could set the scene here. It's the site of an ancient lake. It's not there anymore, but there once was a lake here. - Katie Stack Morgan is the project scientist of the Perseverance rover. She's kind of like the brain that coordinates all the different parts of the operation. And in 2024, they sent Perseverance into investigate a little outcrop of rock in the crater. - And when we got there, the outcrop, I would say didn't look particularly unusual. I mean, rocks on Mars are shades of red and gray and often pretty dusty. - But as the scientists went through some pictures, Perseverance was sending back. They noticed an unusual rock. We see in the images these totally weird features that we called leopard spots because they look like leopard spots. What is otherwise a red rock has these little white spots in it. And each of the white spots is surrounded by a dark rim. And we thought, whoa, I mean, this is unusual. You don't see this in most rocks that you look at on Mars. We had some of our scientists look at these leopard spots and say, hey, this looks like a kind of feature that I recognize from here on earth. And it's one that involves microbial life and it's found in sediments like what we're seeing here in the channel. And so that got sent around and said, hey, you know, these things, if they form on earth, typically have a biological origin. - And as Perseverance sent over information like chemical analysis of this rock, scientists found more tantalizing clues. The data suggested that there were organics like carbon and two specific minerals that here on earth can be the byproduct of tiny living microbes. It was all pretty exciting. - We were like, whoa, okay, like we've got organics. We've got this interesting chemistry going on. So we actually took a eyes closed, heads down vote of the science team to see whether people thought this was a potential biosignature. So fortunately I got to see 'cause I called for the vote so I got to see what happened. And there were a lot of hands raised in the room. - So intriguing. Now, if life did create these minerals, it probably did it something like three and a half billion years ago. - We do not currently have an expectation that there is life in these rocks today. - And this remote analysis of the leopard print rock is not definitive proof that there was once microbial life on Mars. There are, for example, other ways that these particular minerals could be produced without life lending a hand. But this month, a peer reviewed paper came out saying that it is at least plausible that this leopard print could be a sign that life once lived on Mars. It is potentially a biosignature, a trace left behind like an old dinosaur footprint or a fossilized worm burrow as a trace of ancient life here on Earth. The best way to get more certainty would be to bring samples of this rock back here to Earth where we could then study them more closely. - If we bring these samples home and we find evidence of life in them, I mean, I think I will have considered myself having contributed something worthwhile to humanity. But until then, this is still a pretty cool step towards maybe finding alien life out there. - There are a lot of things about this job working on a rover mission that are like any job. But then every once in a while, you get kind of like pulled out of that. And then you're like, oh, wow, the things that I'm working on have the potential to change paradigms for how we think about life in the universe. - Here at Unexplainable, we have been interested in Perseverance's quest for a while now. And so in light of this new finding, we wanted to share an episode from our colleagues, Brian Resnick and Manding Wen all about the search for life on Mars. - For ages, scientists have looked at Mars and just wondered, anybody home? - 200, 150 years ago, if you asked the average person who understood the concept of planets in our solar system, do you think that there is life on other planets in our solar system? Their answer would almost certainly have been yes. - This is Lindsay Hayes. She's a NASA astrobiologist. And she explains just for a lot of scientific history, people really just assume there was advanced life on Mars. - The science community was looking at Mars, not asking the question, are there Martians? But what are the Martians like? And what do they do? And how are they living on their planet? - And it wasn't just a few fringe scientists, really big thinkers were in on this idea. - Percival Lowell, H.G. Wells, Alexander Graham Bell were all folks who read about Mars and wrote about life on Mars and conditions on Mars. - In particular, the astronomer Percival Lowell, he hypothesized that an advanced civilization had built these canals on the surface of Mars. And these wild ideas just stuck around for a long while. Lindsay told me about newspaper clipping from 1915. - After the outbreak of World War I, there was articles that were essentially like, the Martians can probably see we're at war. And they probably think, what are those human beings doing? 'Cause they're probably so much more advanced, they probably don't have war. - The thing is though, we couldn't really figure out whether there were Martians until we just got an up close view of Mars. So starting in the 1960s, NASA sent a series of spacecraft to fly by and take a look. - In 1965, the unmanned spacecraft Mariner 4 flew past Mars 6,000 miles above its surface. It's single camera took photographs that were startling. - We realized not only did the canals not exist, but Mars is a lot less hospitable than we thought it was. - Mars is a desert. It's rough and pockmarked with craters. It's desolate, dead. - It certainly wasn't inhabited by the Martian pacifists. It's not only not inhabited by advanced life. It is pretty hard to imagine how life would really be continuing on the surface of Mars. - There were no obvious signs of life on Mars, but that didn't end the search. - Mars is a planet that continues to show us just enough to keep us intrigued. Mars is still the most similar surface environment of any planet or of any body in the solar system. There's still an atmosphere there. It still gets a good amount of sunlight. It's still intriguing in the potential. - In the decades since the Mariner missions, we've sent landers to Mars and orbiters and rovers to land on the planet. And we've collected a lot of information. We've realized that those scientists from a hundred years ago, they were just asking the wrong question. The question isn't who are the Martians? It might be when were the Martians? The quest to find signs of ancient life on Mars is to ask some of the biggest questions possible about life and how it began and how it begins. It could help us understand life on our own planet, where it came from, and perhaps even weirder, show us that it didn't even start on Earth at all. So that's what we're going to talk about on this week's show. Was there ever life on Mars? And how would we know if we found it? - You're looking at a kind of world that hasn't existed for millions of years. It hasn't existed. - Millions and millions and millions. - It's almost as if time forgot this place. - Is there life on Mars? - There's a whole universe out there, Steve, beyond anyone's comprehension. - Since the 1960s, scientists have found evidence of a lost Mars. This was a Mars billions of years ago where there were rivers, lakes. - Mars is a very different place today than it was four billion years ago, but you can see evidence of what it was like four billion years ago. What you see are things like, what looks like the remnants of a huge river delta, which indicates not only did you have water flowing, but you probably had lots of water flowing over a long period of time that continued to deposit sediments. - A lot of the evidence of this lost Mars comes from on-the-ground work by rovers, like the Curiosity, which has been driving on Mars since 2012. - There's a sort of standing joke. Oh, scientists have discovered water on Mars again. You know, NASA has discovered water on Mars again. - Water is essential for all life as we know it. So that water could have had life. Even if it was just microbes. And that life could have settled into the sediment of some Martian river delta. And then that sediment could have turned to rock, preserving that evidence that life existed. And those rocks could just be up there waiting for us to find them. But it's not guaranteed. - Not only did life have to exist for long enough to sort of spread and take a hold and be something that was enough happening to be a process, but it also had to be preserved. And then it had to be preserved in a place that we can find. And so there's a certain, you know, needle in a haystack aspect to this as well. - It's a real long shot. But the best way to figure out if there is some life preserved in those rocks is to get those rocks here on Earth. And so in July, 2020, NASA launched Perseverance, its latest rover to explore the Martian surface. - Launch sequence to start. - What's really cool here is that Perseverance is the first rover that's specifically collecting samples to be studied here on Earth. It's kind of like getting moon rocks back for the first time. These samples will be game changers. Possibly our best shot at answering the question, was there life on Mars? - The skies look great. There is little wind. - The destination, Jezero Crater. This is a place where billions of years ago, a river emptied out into a lake. It dropped sediments, rocks, and potentially life. And this is the exact sort of place where signs of life could have been preserved. - That is true. Go Atlas, go Centaur. Go Mars, 2020. - But first Perseverance had to survive a really dangerous journey. - Five, four. Engine ignition, two, one, zero, and lift off. - It wasn't the seven month flight through space that was so dangerous, but actually landing on Mars. - They have confirmation of entry interface. Perseverance is currently going 5.3 kilometers per second. Had an altitude of about 120 kilometers from the surface of Mars. - The landing was called the Seven Minutes of Terror. It took about seven minutes for the spacecraft carrying the rover to go from the top of the Martian atmosphere to landing safely at the bottom. And all the while, it had to slow down from around 12,000 miles per hour to well, you know, zero. - Our current velocity is about 5.36 kilometers per second and an altitude of about 67 kilometers from the surface. - A lot could have gone wrong. Mars is so far away that any command NASA sent to the spacecraft took several minutes to get there, which meant they just couldn't pilot the spacecraft in real time. It had to land itself in a very rough landscape. - The parachute has deployed. - The navigation has confirmed that the parachute has deployed and we're seeing significant deceleration. - But the spacecraft was just too heavy to land by parachutes alone. So NASA needed to use a special maneuver called a sky crane to get the rover down to the surface. - Sky crane maneuver has started. About 20 meters off the surface. - When the spacecraft was just above the surface, it fired thrusters so it was hovering. And then that really heavy 2000 plus pound rover was lowered down from the spacecraft by cables. Once it was on the ground, the spacecraft detached the cables from the rover and then blasted away so it wouldn't fall on top of it. - Touchdown confirmed. Perseverance safely on the surface of Mars, ready to begin seeking the stand of top flight. - Perseverance has been on the surface of Mars for more than a year now, looking for that perfect rock that might contain evidence of past life. But how do you choose those rocks on a planet full of rocks? How do you find that needle and that enormous haystack? We wanted a firsthand perspective here, so we did something fun. We sent producer Mandy Nguyen to Mars. - Well, I didn't technically get to Mars, but I went to the next best place. So what we're looking at is what essentially looks like a large sandbox with rocks of different sizes. - I went to the Mars yard at NASA's Jet Propulsion Laboratory in Pasadena, California. And this is where I met Morgan Cable, a research scientist on the Perseverance team. - We can position these large rocks and boulders as obstacles to be able to test the autonomous navigation of the Perseverance rover. - So this is almost, sometimes it functions as an obstacle course. - That's exactly right. - The Mars yard is the best place to test the rover without going to space. It's supposed to be like the Martian landscape itself. Dusty, rocky, and full of boulders. - Well, you wouldn't see the trees in the background or hear the birds chirping. But yes, this is essentially what you would see. And maybe in the evening, close to dusk or at night, you might look up and see a little blue dot in the sky and realize that that's where everyone else who's ever lived in human history has been. It's right there, that tiny little blue dot. And you can-- - And maybe there wouldn't be construction on Mars. - Yeah, I know. There is some construction going on here. - Let's walk back inside. - Okay. - Morgan led me into a small warehouse in the Mars yard, which is where the rovers are. But these aren't the actual rovers that end up on Mars. They're exact replicates. So we have a copy of the Mars Perseverance rover right here. And that allows us to run all sorts of tests, diagnostics, to do some experiments here that might be perceived as a little bit too risky to try on Mars, because we can very easily make repairs here, and we can't really do that quite as easily on the red planet, at least not yet. - Can we go look at the rover? - We can totally go look at the rover. - Amazing, that's good. - Look at the rover. Perseverance was kept behind these red velvet ropes, kind of like what you'd see at museums. But we weren't allowed to go closer than about six feet, because the static electricity humans generate could tamper with the instruments on the rover. - Okay, can you describe to me what we're looking at? Like it's, this is really big. They are really big, right? - Perseverance kind of looks like a huge Wally. It's car-sized, seven foot tall, 2,200 pounds nuclear-powered, with an extendable arm and a drill attached to it. It also just looks so rugged, like the six wheels. I mean, I guess this is the sort of thing ready to just exist on Mars and drive around. - All of the instruments work together to be able to give us a more complete picture of Mars' geology and its potential for astrobiology, which is what excites me the most. - The actual Perseverance rover, not the copy, is all the way on Mars now, but it can't get around all on its own. That's where Camden Miller comes in. - I am a rover planner, aka rover driver. - Even though Perseverance can navigate to a specific spot on its own, it still needs constant guidance from scientists and engineers like Camden to determine exactly where it should go. - Every Mars and morning will point its antennas at Earth and listen for commands and receive the commands, and then once it receives them, it'll start executing them. - But figuring out when that Mars and morning starts can lead to some issues. - When we landed, we were living on Mars time for about two months. - One Martian day is about 40 minutes longer than an Earth day. So keeping up with Martian time is like shifting two time zones every three days. - So yeah, the schedule gets a little crazy when you're living on Mars time. One time, me and my two roommates, we were all sitting at the dinner table, and I tend to wake up earlier. I was even waking up early on Mars time, and so I was eating lunch. My other roommate who was on Mars time was eating breakfast, and our other roommate who wasn't on Mars time was eating dinner. We were all sitting at the table eating different meals at the same time. - All of these scheduling workarounds can sometimes make driving the Mars rover seem like a chore. - I think I was on shift one time, and we were looking at these pictures of the ground in front of the rover, and it was just nothing but pebbles. We were like, wow, this is a really boring workspace. It's just nothing but pebbles. Then it dawned on us. It was like, we're looking at rocks on another planet. We're calling it boring, what's wrong with us? Holy crap, we're driving a rover on Mars. - So Camden's controlling the rover, but when he wants to know exactly where to look for signs of life on Mars, he has to talk to scientists like Morgan. - We're exploring different sedimentary layers, and we're looking at changes in composition as we go through those, just like a geologist would here on Earth. - Morgan specifically works on an instrument called Pixel, one of the attachments of Perseverance's robotic arm that analyzes the makeup of Martian rocks. Pixel is basically a very fancy x-ray that fires at rocks, and when those x-rays interact with the actual atoms in the rock, they fluoresce. And in doing that, we can actually give you a map of what kinds of elements are in that rock. - The only way we'll know for sure if any of this is life, or at least points to life, is if we're able to look at rock samples up close and back on Earth. With all the equipment, scientists couldn't pack onto the rover. We have to bring the rocks home, because sometimes what seems like life at first might not be life at all. - You might have heard of a particular Mars meteorite that was collected here on Earth in Antarctica back in 1984. It was called ALH84001. - Basically, a chunk of Mars was ejected into space by some sort of impact, floated around for a while, and eventually crash-landed onto Earth. - We were able to cut that meteorite open, look inside, and we saw some structures that looked an awful lot like cells, tiny little worms, but they were much, much smaller than the width of a human hair, very, very tiny. And just by your eye, you would say, "Oh, that looks like a worm, that looks like life. That must be life." - Scientists thought that they had actually discovered tiny Martian life inside this meteorite. But now, many scientists think that what looked like fossilized bacteria was actually shaped by geochemical interactions between water and rock. - That's why whenever we search for life or evidence of life in other places, we don't just rely on one thing. We don't just rely on an image that might trick our eyes. We don't just rely on one chemical technique that could potentially be confounded by something that we don't fully understand. - It's also possible that we might actually find life in these rocks and not recognize it. It just might be too different from life on Earth for us to identify. But for us to have the best possible shot, we need to get the rocks back to Earth. - All of those bits of information need to be collected together and analyzed as a whole for us to really be confident that we have made what I think would be civilization-level science of finding out for the first time in human history that we're not alone. - Perseverance can't get the rocks home on its own. So NASA and the European Space Agency have plans to retrieve the samples with a different spacecraft sometime after 2030, which would be the first time we've ever taken Mars rocks all the way back to Earth. - This whole journey that perseverance is on, what if it all works? What would it mean to find evidence of life on Mars? Best next. - Every day, the president faces tough choices. - We sat in the Oval Office and helped President Biden grapple with those decisions. Now we'll help you make sense of today's national security stories in our new podcast. - This is the Long Game. I'm Jake Sullivan, President Biden's National Security Advisor. - And I'm John Finer, Biden's Deputy National Security Advisor. - Each week, we'll explain the national security stories shaping our world and how presidents make those big decisions. - The first episode drops on Friday, November 7th. - Search for the Long Game wherever you get your podcasts. - From the Vox Media Podcast Network. - Support for the show comes from one password. Even if you're careful about security, there's no way to tell that everyone in your company is. Not everyone is built for it, which is fine. You just need the right tool to make passwords simple for everyone. And Trellica, by one password, makes security simple for every single employee on every application. Trellica, by one password, inventories every app at your company and it assesses risks, which lets you enforce best practices all around. On top of that, you can figure out what apps you should or shouldn't be paying for. You can reduce unnecessary costs by analyzing app usage data to get rid of unused licenses and redundant apps. Trellica uses a self-serve app hub. So whenever people need access to a new app or tool, that whole process is super simple. With Trellica, by one password, you and your employees can feel good about secure, flexible app access. Take the first step to better security for your team by securing credentials and protecting every application, even unmanaged shadow IT. Learn more at onepassword.com/unexplainable. That's the number one, password.com/unexplainable. I'll lower case. Support for Unexplainable comes from Wondery and their new podcast, Lawless Planet. The global climate crisis has front lines on every corner of the planet, filled with uncomfortable truth and often terrible acts. Lawless Planet, the new podcast from Wondery, tells these stories almost like a true crime podcast. From the depths of the Amazon to small town America, host Zach Goldbaum investigates stories of conflict, corruption and resistance. Each episode takes you inside the global struggle over Earth's future. It's got mysterious crimes, high stakes operations, billion dollar controversies that reveal what's truly at stake and the everyday people affected along the way. You can follow Lawless Planet on the Wondery app or wherever you get your podcasts. And you can listen to new episodes early and add free right now by joining Wondery Plus in the Wondery app, App of Podcasts or Spotify. - Wally, Wally. - Unexplainable. We're back. Hey, Mandy. - Hi. So you went on this really fun field trip and I'm just jealous. You saw this perseverance clone up close. - Yes, I did. And it was so incredible. - What do you think will happen if all of this works and we get these rocks back? - I mean, I think that's gonna be such a huge deal. Like we've never deliberately gotten rocks back from Mars. And, you know, if they could tell us anything about if there was life there, I think that'd be like, as Morgan said, like civilization defining science if we were to find anything. - What do you hope? Do you hope there was life? - I mean, of course, I think that'd be so exciting. That's like the big question, right? That like years and years and decades that people have been trying to figure out. - And it's more than just the answer to is there life on Mars. Lindsay Hayes, the astrobiologist in NASA I was talking to, she was telling me about like getting a sample of life on Mars could really teach us about where life on Earth comes from or just like where life comes from in general. - You know, to me, the reason that I am interested in the search for life, it has to do with this concept of how interrelated life is on Earth, right? All of life that we know of on Earth is all related. - You and I are related to each other. You know, if you go back on our family trees far enough, however many thousands years, we'll find an ancestor in common. And that's true of not just humans, but like, you know, at a certain point, there's a common ancestor between a human and a chimpanzee, you know, going further back. And even further back, there's a common ancestor between a chimpanzee and a fish. And then going back, you know, there's a common ancestor between a fish and bacteria. And Lindsay has this really epic question. Knowing that all life on this planet seems to be all related to each other, what would life on a different planet be like? - If we found an example or a specimen that showed there was used to be life on Mars, like her big question is, well, is that life related to life on Earth? Like, does the life on Mars share a common ancestor? - At which point, wow, that means that, you know, maybe life is created in one place and then sort of spreads between planets or moons. - It could be we're related to Martians, which is, whoa, how are we related to Martians? If that's the case, maybe life didn't start on Earth at all. Maybe it started on Mars. And then somehow like, got here. She used the term, like, planet swapping spit. Like, as the planets are forming, maybe, you know, a bit of an asteroid blasts off a chunk of one that has some life on it that goes into another planet. I mean, weirder scenarios can come from there. Like, what if life didn't start on Mars or Earth, but somewhere else? - Ooh, spooky. - Spooky, like, where did that life come from? But then, like, every answer to this question is epic because if it turns out the life on Mars is somehow different or like too different to have a common ancestor with life on Earth, then maybe that means, like, life spontaneously started there. - Which means that life is so fundamental, a process of the universe, that you can have two different life-generating events in the same solar system. And that, you know, totally changes our perception of life. But also, is it like us or is it something completely different, right? Is life a fundamental process that happens any time there is a habitable environment? - And in that case, it might mean that any time the conditions are right for life anywhere in the galaxy, around any planet, like, life will just form because that's what it does. So, that is just such a woe for me that, you know, if we do get samples back and, you know, as you were describing there, you know, a lot of converging lines of evidence and we kind of reconstruct a picture of whatever this ancient, probably microbial life was, like, we really get really close to the question of all questions of, like, how does life start? - So, if we were to find life in these little rocks, we'd either be related to Martians, potentially, or it could just be the beginning of finding a lot of more life everywhere. - And this is also, like, a cool thing about the overall missions on Mars is that the surface of Mars is really old. It's, like, billions of years old. And so, anything we find there is going to be just so old and so ancient and just, like, older than anything we can find on Earth. So, we might even find, like, an earlier form of life than has ever been discovered on Earth, like, something even more primordial. - Wow. (both laughing) - I don't know. Yeah, it's really kind of, like, I love this contrast of, like, a lot of these answers can be figured out from just, like, a handful of rocks. Like, isn't that wild to you? - Yeah, that's super, super wild to me. I mean, now we just have to play this waiting game. We're not gonna know till probably, like, 10 years or so. - Why so long? - I mean, so, the sample return missions still have to be planned. Someone needs to send a rocket to collect those rocks and bring them back. Right now, the rover's just carrying all of them. But eventually, they'll have to decide where to place these samples on the surface of Mars so that they can be picked up later. There's no definitive, I think, timeline on that yet. - Yeah, that's kind of funny. It's like interplanetary FedEx needs to come and pick them up. - That's basically how it's gonna be. But I keep, you know, like, there's so much work involved into this project. I keep wondering, what if we bring all these rocks back? We spend all this time doing all this work and scientists look at it and they don't find anything. - You know, it's funny. That's the question I asked Lindsay. And she just told me that, well, she just would want to look somewhere else on Mars. - You know, there's the question of like, you know, it took me 100 tries to make the light bulb and it's not that I failed 100 times, but I found 100 ways not to make a light bulb. You know, it's a similar kind of thing, right? And so, you know, let's keep looking. Let's see what else we can find. - I think I really get Lindsay's persistence here. It's like every answer to the question, was there life on Mars is just so perspective shifting. It's so close to that big question of why are we here? Which is why like, she would want to go back again and again and just try to find the evidence of life. And, you know, maybe there won't be, but it seems worth it to look. - The search for life is never going to be an easy thing, but the questions that you learn, even if you don't answer, was there life here? The answers you find can tell you a lot more about planets and about the solar system and about life. - It's just so cool to imagine that on this rusty colored world, amid dust and billion year old rocks, there is this lonely robot on this mission. You know, kind of completing a dream that scientists have been thinking about for hundreds of years. - Well, I mean, it's also not so lonely. When I think about perseverance on Mars, I think it's really easy to think about it as a lone rover traversing the desert landscape, the rocky red, you know, ground. But after going to NASA and speaking to the scientists, I can't help but think about all the people and all the history that is behind this rover and how, like, yes, it's kind of, in a way, alone on Mars, but it's not truly alone. One of the things that Morgan said to me was that with the perseverance, it's almost like we're extending our senses to the red planet. And so, to me, this rover is a part of us, but across space, you know? - I love that. (soft music) - This episode was reported and produced by Manding Nguyen and Brian Resnick with production help from Meredith Hoddanot and Bird Pinkerton. It was edited by Catherine Wells with additional edits from Meredith and me. I also scored the episode, mixing and sound design from Christian Ayala and fact checking from Richard Seema. To read more about some of the topics we cover on the show or to find episode transcripts, check out our site at vox.com/unexplainable. If you have thoughts about the show, you can always email us at [email protected] or you could leave us a review or a rating, which we'd love to.