Pod Insights Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas 314 | Karen Lloyd on the Deep Underground Biosphere About this episode There are living creatures dwelling deep below the surface of the Earth, as deep as we are able to drill. These hearty microorganisms are related to more familiar life forms on land and under water, but the operate and survive in ways that are quite different from what we're familiar with. They live off of nutrients that have penetrated from the surface, or sometimes off of pure electrons. Karen Lloyd is a scientist who has traveled around the world studying these organisms, as she explains in her new book Intraterrestrials: Discovering the Strangest Life on Earth https://press.princeton.edu/books/hardcover/9780691236117/intraterrestrials.
Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/05/12/314-karen-lloyd-on-the-deep-underground-biosphere/
Support Mindscape on Patreon https://www.patreon.com/seanmcarroll.
Karen Lloyd received a Ph. D. in marine sciences from the University of North Carolina. She is currently the Wrigley Chair in Environmental Studies and Professor of Earth Sciences at the University of Southern California. Among her awards are a Sloan Fellowship, a Simons Early Career Investigator, and a NASA Early Career Fellowship.
Lab web site https://lloydlab.utk.edu/ USC web page https://dornsife.usc.edu/profile/karen-lloyd/ Google Scholar publications https://scholar.google.com/citations?user=cwNS_2EAAAAJ&hl=en Bluesky https://bsky.app/profile/karenlloyd.bsky.social
Transcript 13,223 words · 9 speakers
Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
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1:10 Sean Carroll? Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. One of the things that we've talked about many times here on the podcast is the idea of looking for life elsewhere in the universe, on other planets or moons here in the solar system, like Mars, Europa, Titan, maybe on exoplanets further away. And there's a bunch of obstacles to finding life elsewhere. We haven't found any yet. We've had some hints of clues of things that might be life-related, but certainly nothing directly that could be characterized as life, partly because it's hard, right? Because you have to either fly far away or look very indirectly using some kind of signal, spectra, or even sample returns from some nearby planet.
1:55 Sean Carroll? But the other thing that is making it hard is that we're not sure what to look for. There are characteristics that life has here on Earth that you can hope to find somewhere else. But maybe life somewhere else is still life, but nevertheless is very, very different. And therefore, its characteristics or its signatures might be completely different. So you would think that one super obvious strategy would be to make sure that we understand life here on Earth really, really well if we're trying to understand the entire space of possibilities for what life could be. And to a certain extent, we know a lot about life on Earth, right? We have whole departments of biology and so forth in our universities,
2:39 Sean Carroll? all devoted to studying life on Earth because we don't have any examples of life elsewhere. But it turns out that there's still lots of life here on Earth that we don't know a lot about. And today's episode is about one kind of life here on Earth that we don't know that much about compared to what we really would like to know. Today's guest is Karen Lloyd, who is described as a microbial bio geochemist at USC. And just that description should tell you that there's clearly a lot going on here. She has a new book coming out called Intra-Terrestrials: Discovering the Strangest Life on Earth. And the basic idea is that Karen studies life that exists underneath the surface of the Earth.
3:24 Sean Carroll? So not just in the oceans or water or whatever, which counts as underneath the sea level, but there's still a surface below that. This is below the surface of either land or sea. Okay, literally in the crust of the Earth, sometimes kilometers deep. It turns out that as far deeply as we can dig into the Earth, we can find life. We can find little microbes, little bacteria and archaea, two different kingdoms of microbes, as Mindscape listeners have heard before. They're there. They're there. They apparently... Live longer and move more slowly. They're a little bit more senescent than life here on the surface of the earth, but they're there.
4:09 Sean Carroll? Their biochemistry is a little bit different. They can take advantage of different kinds of food and fuel sources. They move at different rates and they're very clever about using the resources that they have access to. So the fact that those things can exist here on earth certainly informs both questions about how life formed here on earth, the origin of life, but also what life might be like somewhere else. And it turns out to nobody's surprise that these interterrestrials are, they're related to the organisms that we know, don't get me wrong. As far as we can tell, we have not yet found an interterrestrial or a little microbe beneath
4:49 Sean Carroll? the surface of the earth that is completely separate from the rest of life on earth. But you're also not surprised that they're different, right? They've discovered different strategies, different evolutionary pathways that they've taken. So we're just beginning to study these little critters and we're learning a lot. And I think that that's going to teach us a lot about what life is like now here on earth, what life was back when it started, and what life might be like elsewhere in the universe. These are all very exciting questions and you're getting in on the ground floor here in this episode. So let's go.
5:42 Sean Carroll? Karen Lloyd, welcome to the Mindscape Podcast.
5:45 Speaker 03 Thank you so much for having me.
5:47 Sean Carroll? So you're telling me there are whole species of life forms dwelling deep beneath the surface of the earth. That sounds a little scary.
5:58 Speaker 03 I know, but it's not just like a couple of species, it's a lot of species, like billions of species. And furthermore, it's not just, you know, a couple of extra types of things that are related to E. coli, it's deep branches on the tree of life, whole phyla that are not found elsewhere.
6:18 Sean Carroll? Phyla being the plural of phylum.
6:20 Speaker 03 Yes. And to think about a phylum, I know this isn't something that, I know everybody like had to learn it in biology classes. I always learned King Philip came over from Great Spain, so it's kingdom, phylum, class, order, family, species. So if you go up that chain up to phylum, that's sort of like a very deep evolutionary branch. And so things that are in different phyla have very different ways of living. So I think, I always get confused about the animals, but I think that inverte, or all vertebrates are a phylum. That's our phylum. So basically us and turtles and everything with a backbone, we're the same phylum. So it's like we're discovering these new phyla, you know, tens of them.
7:05 Sean Carroll? I like that you, that you always get confused about animals, but you're, you're up on the little microbes that we have.
7:10 Speaker 03 I know. It's hard to make it all match. I mean, like, humans just showed up like five minutes ago.
7:18 Sean Carroll? We're nothing, yeah. Right. So before you even get to the little microbes down there, you know, how deep are we talking? What, what is it like down there?
7:27 Speaker 03 Yeah, so we can talk about different levels of deep because in some places, what I consider to be the subsurface starts pretty shallow. You know, if you, if you're at like a mud flat, you know, the stinky backside of a barrier island or something, and you like dig your toes down a little bit, I think you're already there. Because the question is, are you in a stable enough environment that's sufficiently remote from steady inputs of oxygen and light? And if you are, then you're in the subsurface. So I think it starts like a couple centimeters down or even millimeters in some places. But then as far as it goes, we don't super know. We've found life many kilometers deep down, but
8:12 Speaker 03 we don't have a lot of samples from things that deep.
8:14 Sean Carroll? When you say we found life, is this literally from drilling and, and looking? Or is there some other way?
8:21 Speaker 03 Yeah, so we've got sort of two main ways we can get at the deep subsurface life. We can drill down to it, which, as you can imagine, is incredibly expensive. And one of the best ways to get down there is to sort of have it be run by prophets. So if you can connect yourself up with a mining company, that's a good way to get deep subsurface samples. But another way is to wait for it to come back to you. So I do a lot of work where we use hot springs as like, it's real gross, but kind of like squeezing a pimple. You know, like when you, when you run two continents against each other, which is what happens in all of our subduction zones along a lot of our coastlines, you get things like earthquakes, you get things like volcanoes, and you also get things like hot springs because you create all this pressure.
9:06 Speaker 03 And with this fluid comes up the deep subsurface microbiome.
9:10 Sean Carroll? Okay. But so, again, what, I, as a non-GEO person, like, anything smaller than a galaxy, I think, is kind of, kind of weird for me to think about. So when we're kilometers, like, number one, how many kilometers deep do we know about? And number two, that's still the crust of the Earth, or are we down at a lower level?
9:31 Speaker 03 Yeah, so it's, we're talking about the crust. So the crust is somewhere 20 kilometers to 200 kilometers deep. And we, you know, we can make the sort of M and M candy cutaway pictures of Earth that I'm sure everybody's seen with the core is on the inside, and then there's the big mantle, and then there's that thin crust around the outside, which is actually quite deep. If you think about it from biological terms, you know, hundreds of kilometers is actually a lot of depth. But we've never actually drilled, like, humans have never drilled below maybe 10 kilometers.
10:09 Sean Carroll? Okay.
10:10 Speaker 03 Never. Like, for any reason, not just for biology. And that's something that I think hasn't really, it's maybe something you wouldn't realize because, like, oh, well, we know so much about the mantle, we know so much about the core, certainly someone has sampled it. Like, no, no one's ever been there.
10:24 Sean Carroll? So it's all indirect through earthquakes, geismology, things like that?
10:28 Speaker 03 Yeah, which is, I mean, not to put those down, they've created a beautiful image of what's down there.
10:33 Sean Carroll? Okay, but you need to actually dig down there. And have you ever, has any drilling ever reached a point where we can look at there and say, there's nothing living there? Or do we keep finding life forms along, all along the way?
10:49 Speaker 03 Yeah, it's always hard to conclude there's nothing living in a place.
10:54 Sean Carroll? Okay.
10:54 Speaker 03 Including Mars. You know, as far as I'm concerned, the jury's still out.
10:59 Sean Carroll? Okay.
10:59 Speaker 03 I don't think that we have found life on Mars, but I don't think that we have not, we have found definitive proof there's not life on Mars. So it would be the same thing for the subsurface.
11:08 Sean Carroll? Okay, we will, we will get to, we'll get to Mars, definitely, over the course of the podcast. But here on Earth, so it's entirely dark, obviously, down there where we're talking. Is there any flow of either water or are the sort of rocks kind of on super long time scales moving around in some way?
11:28 Speaker 03 Uh, yes, to all of that, depending on where you're looking. Because it, you know, what's underneath our feet is actually quite varied and kind of an interesting place. It's not a place that it's easy for humans to go, but if you're tiny, there's a lot of options. So on continents, there's aquifers, which we use for drinking water. There's even deeper aquifers that we would not use for drinking water because they're full of nasty chemicals and stuff that we don't want to use. But those things can be useful for microbes. So some of these aquifers, like for the ones that are capped by the Canadian Shield, have been isolated. That water is like billions of years old, that, the water itself.
12:11 Speaker 03 Which is crazy to think that liquid water has just hung out liquid for that long. So that, that's one possibility. There's other places where you get an influx of lots of energy, like these continental collision zones, so subduction zones or continental margins. Like, for instance, the, the Andes, that great, beautiful, super tall mountain chain that runs pretty much the whole way down South America on the west side, is driven by the Pacific Plate going underneath that continent. And that pressure sort of basically makes the volcanoes happen. And so... In the process of two continents colliding, there's a lot of activity and there's a lot
12:56 Speaker 03 of chemical reactions, there's tectonic reactions, there can be a lot of hydrogen produced through a process called serpentinization, depending on what type of rocks are being subducted. And that's a great reaction because it's just rocks and water and it makes everything you need to run life, which is kind of amazing. But then there's also the boring places too where nothing happens.
13:18 Sean Carroll? Oh, okay, good. That's something. But I gotta ask about the billion-year-old water. I mean, the idea of water being billions of years old actually isn't shocking to me in terms of the water molecule could be billions of years old, but you're saying that it has been preserved in liquid form, basically untouched for billions of years, which probably is shocking.
13:37 Speaker 03 It never became rain. It never became ice. It was never snow. It was never a cloud.
13:43 Sean Carroll? And why, in my simple-minded way, like, why hasn't this water all been squeezed out by now? Like, why is it still hanging kilometers below the surface of the Earth?
13:53 Speaker 03 Uh, that's more of a geol... I don't know. I don't want to venture too hard and like...
13:58 Sean Carroll? That's fine.
13:59 Speaker 03 Yeah, I want to not veer too far. I sort of have to work... I collaborate a lot with geologists who provide the context for this stuff, for the most part, for me.
14:12 Sean Carroll? Okay, good. But we can think of...
14:14 Speaker 03 All I understand, there's a big Canadian Shield sitting on it. It's hard to get out.
14:17 Sean Carroll? Yeah, that's perfectly plausible. So are there temperature gradients from place to place, or is it more or less uniform everywhere?
14:28 Speaker 03 Yeah, there's huge temperature gradients. And temperature is something that ultimately will limit life as we know it because it's some, you know, everything we know about so far is carbon-based life. And at some high temperature, you're not going to get carbon molecules holding together in the way that we know that they need to, to have life function. So that is going to be a limiter at some point. We just, you know, sometimes that gradient happens really shallow. Like, if you're standing in a volcano, it happens at your feet.
14:58 Sean Carroll? Right, so we do want temperature gradients, but we don't want the temperature to be too high. And you're saying that lots of the Earth's lithosphere, I guess, qualifies for that.
15:09 Speaker 03 Yeah, it's probably just too hot.
15:12 Sean Carroll? It's probably just too hot. And, OK, so what kind of coverage do we have in terms of digging deeply and looking for life forms? Have we sampled the whole surface of the Earth? Or is there still a great uncharted territory?
15:24 Speaker 03 It's a massive uncharted territory. I mean, it's just if you, I think people wonderfully are getting a good feel for how unknown the oceans are, and that is absolutely the case. We just don't know a lot about what's in the deep sea. And I work in the deep sea, and that's one of the mysterious places that I try to crack into. But when you study the deep sea, you can toss a bucket off the back of a ship and take a sample. And you can do that all day long, or you can do that for weeks on end and get lots and lots of samples of deep waters. I mean, it's hard to work in, but it's possible. We can't do that in the crust. We can't just like throw something over the side and like have it drop down because it's ground.
16:08 Speaker 03 So getting those samples is always going to be slower and more laborious than working in the ocean. And so we, I think it is just a fascinating frontier.
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17:31 Sean Carroll? And when you go to different places and dig and find some little microbe, do you find different kinds of microbes in different places? Or is there kind of a uniform population spread over the Earth's surface?
17:43 Speaker 03 Yes, to both. Like, all your options you're giving me, like, for all these questions, are like, yes to everything.
17:50 Sean Carroll? Yes, yes, yes.
17:51 Speaker 03 Because it's like, it's this whole world down there. It's like a second Earth buried underneath our Earth. So there are places where we see different types of microbes in different places. That is definitely true. There does seem to be some, like, endemic populations that are only found in the place that we find them. But we have a couple of weird instances, and I still have trouble wrapping my brain around this, but there are some deeply buried aquifer microbes that seem to have an unchanged genome all around the world.
18:22 Speaker 03 It's called the Sulforutis adoxiater. And I don't know why, I didn't do this work, this is my colleagues, but I've talked to them about it, and they're like, "Yeah, we don't know why either." We find it very unsettling.
18:32 Sean Carroll? We're gonna get the podcast transcribed, so could you say that name again more slowly?
18:37 Speaker 03 The Sulforutis adoxiater.
18:40 Sean Carroll? Wow, okay.
18:40 Speaker 03 It means, um, it means bold traveler.
18:43 Sean Carroll? Bold traveler. Well, because presumably the resources are very different down there, right? I mean, they're gonna be optimized for a very different environment than the bugs we have up here on Earth.
18:53 Speaker 03 Yeah, yeah, there's not a lot of oxygen. There could be some oxygen, but for the most part, there's not much oxygen. And, you know, if you think about what drives the power's life up at the surface is the sun. I mean, pretty much everything flows from that. Even though we're not photosynthetic, we're absolutely dependent upon plants. But in the subsurface, there's no photosynthesis, there's no sunlight. And so all of that activity has to be fueled by chemical reactions. But the nice thing about the chemical reactions is that there's just a gigantic variety of them. There's just a ton of options, because if there's one thing they're rich in, it's minerals and metals and things that have a lot of redox power, so they can be oxidized and reduced chemically.
19:36 Sean Carroll? Okay. So, yeah, so tell us about what we know about the life forms. I mean, I guess, you said already, there's a lot of them. I mean, I don't know whether it's better to go by mass or by number of cells, but tell us how much life is down there.
19:51 Speaker 03 Well, we estimate, of course, these are, any of these big numbers would be estimates, are about 10 to the 29, living microbial cells in the subsurface. And they're small, so biomass-wise, they're not going to beat, you know, the total number of plants up at the surface, because plants are, plants are big. But, but really, it's a gigantic ecosystem. And to be as undescribed as it is, you know, it's a lot of cells. I usually say it's 10,000 times more than the estimated number of stars in the universe. What do you think?
20:27 Sean Carroll? Okay, that's good.
20:27 Speaker 03 Can I say that?
20:28 Sean Carroll? That sounds right, yes. That definitely does sound right. I think maybe 10 to the 23, 10 to the 24 is the number of stars, but I would have to look it up. So I think, I think you're on the right track.
20:36 Speaker 03 But then you have to say, like, what's a star versus one microbial cell?
20:40 Sean Carroll? That's right.
20:41 Speaker 03 Bifidolency is kind of interesting.
20:42 Sean Carroll? And are we, you know, when we, when we pull them up, I mean, sorry, let me, let's just be like, very down and dirty about what you do. Do you go to a oil well or something? And you like, put a little claw on the bottom of it? Like, how do we get a sample from down there?
21:00 Speaker 03 There's a bunch of different ways. One is to take a drilling ship and go out in the ocean. And basically this drill string, it's like, it's just a big pipe. It's like a big metal pipe with a really, really angry, angry looking drill bit on the front of it. And you put that thing down there and you basically like drill through whatever you need to drill through. And then you send down pipe after pipe. And if, if, if the drilling is going well, you can actually do advanced piston coring, which is where you make up, you detonate a little explosion at the seafloor and it forces, like a big stroke and it forces this pipe down further. And you can get like nine meters in just like a couple of seconds. And so that's, that's the cleanest sample because you don't need to actually drill and provide fluid and stuff like that.
21:45 Speaker 03 So that's, that's one way we get samples.
21:47 Sean Carroll? And this is done specifically for scientists like you? This isn't, you're not parasitic on something else?
21:55 Speaker 03 Again, yes to both.
21:56 Sean Carroll? Okay, yes.
21:59 Speaker 03 We do everything we can to get these samples. I, I will say, I don't know how much you sort of want to talk about current, current events, but we, we have, the Joydis Resolution is the name of the ship that we use to do this drilling in the ocean. And it has sunset. It was time for it to, to go. And the US was supporting that ship and the United States does not have plans to replace it. So China has built one, but we don't have one in the States anymore. That just isn't, it's a capability that we no longer have in the United States. And we've always been a leader in deep sea drilling, but it's gone.
22:34 Sean Carroll? There you go. Okay.
22:37 Speaker 03 Someone picks it up and saves us.
22:38 Sean Carroll? Well, you know, maybe this is, send the podcast out there and who knows what will happen. And then, so when you pull the sample up, what do you do? You bring it back to the lab?
22:48 Speaker 03 Yeah, you, well, usually if you're talking about at sea, you know, we have these labs on ships, basically. And so we, for these deep drilling operations, we split the core in half. And then you go down the length of it and you take sub samples. So it takes these, processing these samples is always slow and laborious and takes a lot of people. And you just kind of, everybody comes in with their different sampling equipment and takes their piece and they measure chemicals of all different sorts. They measure gases and then they take a microbial sample to grow things, a microbial sample to look at their DNA, their RNA, things like that. So we just try to, we try to measure everything we can when we get these precious samples.
23:28 Sean Carroll? And when you find little microbes from deep below the surface, are they, how related are they to the ones up here on the surface? Are they recognizable, or are they something completely alien-looking?
23:39 Speaker 03 So, at first, now they're recognizable because we have been digging there enough that we can compare them to each other. But when we first started getting them, you know, I, the, the ability to use DNA from the environment to infer what's living there is something that only came into popular usage in the early 2000s. So this was when I was a graduate student. And I got my first samples from deep sea mud from the Gulf of Mexico. There was a methane seep. I thought I was going to be studying the organisms that use the methane, because that's, that's the biggest signal that we see there. And I, I looked at the DNA sequences that I had, and they, they didn't look like anything
24:20 Speaker 03 at the surface. They didn't, I, I thought I was a terrible scientist. Like, I really was like, oh my god, I'm never gonna get a PhD, because I can't even do the simple task of figuring out who these, these organisms are. And then it turns out, it wasn't my problem at all. It wasn't me. It was that we were all collectively discovering new stuff. And, and nobody had ever seen it before.
24:42 Sean Carroll? So we actually have complete DNA sequences of these little critters?
24:45 Speaker 03 Yeah. So, fast forward to now, technology has really moved, I mean, we, our field has been moving really, really fast. It's very, I think it's very impressive. We can now pull out whole genomes from these little critters, without having to grow them. So we can look not just at their entire genome, we can also pull out all of their messenger RNA molecules, which, that is the molecule that basically says, okay, what proteins are gonna get made? We can pull out their actual proteins and see what they're doing. So we can infer their lifestyles from all of these biomolecules that we can pull out from, from, you know, deep sea muck.
25:22 Sean Carroll? And do they fall into the traditional categories? Bacteria, archaea, maybe viruses? I don't know?
25:28 Speaker 03 Uh, kind of, yes, definitely viruses, um, which are weird and hard to characterize. Um, but they are definitely fall into bacteria. Um, there are some that fall into eukaryotes. That's our branch. Definitely fall into the archaea. Um, but there is a branch of them that, um, has really upended our understanding of what things are. And this is, we've been calling it the Asgard archaea.
25:52 Sean Carroll? Oh, yeah.
25:53 Speaker 03 This is one of the groups that I was finding as a, yeah, it was one of the groups that I was finding as a graduate student and just like, oh God, I don't know what this thing is. Um, it has now been grown in culture by two labs so far. It may be more labs and I just don't know about them, but, um, Krista Schlepper's lab in Austria and Hiro Yuki Amachi's lab at Jamstek in, in Japan have managed to grow this thing. And so it's really amazing to have hypothesized of the existence of these strange primordial weirdos. And then it's like, am I doing this right? Is my inference right? And now they're actually growing them. And yeah, they, they are strange and weird and they're a little
26:34 Speaker 03 bit between the archaea and the eukaryotes. So that's why, that's my answer to your question. They're kind of making us question our, our divisions.
26:42 Sean Carroll? Well, I, I was gonna ask, uh, in what way are they strange and weird? So like, what does it mean to say they're halfway in between bacteria and archaea?
26:49 Speaker 03 Okay. So, um, well, they're halfway in between archaea and eukaryotes.
26:55 Sean Carroll? Archaea, uh, yeah, sorry.
26:56 Speaker 03 So if you, it, back to like intro bio classes, we all had to learn the difference between a prokaryote and a eukaryote.
27:04 Sean Carroll? Let's, let's imagine we forgot that. Yeah.
27:06 Speaker 03 That's what?
27:07 Sean Carroll? Let's imagine that we've forgotten that since then. Yeah. No, no. I mean, I, I might have had that lecture, but I'm also old. So fill me in.
27:14 Speaker 03 Yeah. So eukaryotes have a well-defined nucleus. So they have all their DNA that sits inside an organelle. They have well, we, sorry, we are eukaryotes. We have well-defined organelles, one of which is a mitochondria, which is the powerhouse of the cell. So if you look at, we tend to be bigger, our cells tend to be bigger. And so if you look at a eukaryotic cell under the microscope, you'll see all of these little organelles within it that do different functions. And it's a very complex cell and it always breathes oxygen because we're all dependent on oxygen, although we can also do some fermentation. Um, we need oxygen or we die. All eukaryotes, that's, that's true. Well, there's some protists that are exceptions, but, um, then you compare it to the bacteria in the archaea.
27:57 Speaker 03 And they don't have the structures. They are sort of like little bags of goo. That's sort of how they're characterized in our textbooks. They have nuclear condensation, like their genomes are in a specific region, but they don't have a house around them. They don't have organelles. They're just, they're simpler. It's kind of, everything is out and floating around, and they're not as organized. Okay, that's, that's like where we were until we discovered these ones, these Asgard's, that we first saw this in the DNA. They have the DNA for the cytoskeletal elements that we use as eukaryotes to make all these organelles.
28:38 Speaker 03 So just, just with bioinformatics, with the DNA, we all started saying, hey, it looks like these things actually could have organelles in the same way that eukaryotes do, but they're not. They're archaea. And one of the, one of the things that we know about how we got these organelles as eukaryotes, these mitochondria that we have that help us to breathe oxygen, is that we definitely got those. Some ancestor of ours picked those up by taking in an alpha proteobacteria. They, that we know for sure. So the question is, who ate the alpha proteobacteria and became a eukaryote? And to all appearances, these are the direct descendants of that ancestor
29:23 Speaker 03 before it picked up the alpha proteobacteria that turned into mitochondria and became a eukaryote. And so they retain a lot of these features that we thought were only in eukaryotes, but now we're finding them in archaea.
29:39 Sean Carroll? So the archaea, the sort of standard archaea are like the bags of goo, but these Asgardians have the DNA to make
29:48 Sean Carroll? Compartment, uh, substructures within themselves, but they haven't yet gotten to the point where they have the mitochondria and are full flown, full blown eukaryotes.
29:59 Speaker 03 Exactly, exactly. And so, since they have these elements that we thought were only present in full blown eukaryotes, the question is, well, what in the hell are they doing with them? Why, why do they have them? You know, we, we know about them like running an endoplasmic reticulum and a Golgi apparatus and a mitochondria. What are they doing with them? And so figuring that out has been fascinating. We still don't really know, but now the first images are coming out from these cultures and they are using them. They have structure. They, they're tiny. They're like, they're the width of visible light. Like they're the amplitude of visible light. That's the size of their cell. And, and they've got arms.
30:41 Sean Carroll? So, and, and they're only so far found beneath the surface.
30:49 Speaker 03 Uh, they are, there's one report that's out that someone found them up in the surface waters. So what I've learned is anytime you think you've nailed down where something is and isn't on earth, it's gonna say, screw you. Yes, I don't care. I'm nature. I'm gonna do what I want to do. But they're not for the most part. I, if you, if you, if you look at somebody's gut microbiome, you will never find this one. I don't think that they've colonized us.
31:16 Sean Carroll? You will find, sorry, will you find both bacteria and archaea in our gut microbiome?
31:22 Speaker 03 Okay, absolutely. All the, all the methane that comes out of cows, that's all produced by archaea.
31:28 Sean Carroll? Okay. So, I mean, naively, since I can be naive, this is not my job. So, um, it sounds like this is a step along the way from archaea to eukaryotes.
31:39 Speaker 03 Yeah, I would say it absolutely is.
31:42 Sean Carroll? Yeah. Okay, good. And, and I love the mystery now that they, cause, cause biology, you know, evolution doesn't let you carry along all this extra equipment that you don't use, right? And so we're looking for the usefulness of it. Uh, I mean, one obvious usefulness might be it's hard to live down there. You know, tell us about the, the sort of ecosystem that you have. Like what, what do you, what do you eat? What do you drink? Where do you go for fun if you're a couple of kilometers below the surface?
32:12 Speaker 03 So these guys, for the most part, are the places where we find them in highest abundance tend to be marine sediments that got buried thousands of years ago or longer, where nothing much has happened at all. So like, if you can think about your, your life, what it would be like if you're on a particle, you fall to the seafloor, other things fall around you, and then nothing really changes. You get diffusion. Diffusion is where you go for fun. It's like, hey, we got a hydrogen molecule this century. That was exciting.
32:42 Sean Carroll? Slow-paced. It's a, you know, it's a sleepy town.
32:47 Speaker 03 It's a very sleepy town, but it's a huge ecosystem. So it's like, well, what are they all doing? Why are they all sitting there doing nothing?
32:55 Sean Carroll? So where do they get their nutrition?
32:57 Speaker 03 From, so, well, we're not totally sure, but the biggest form of nutrition would be what got buried with them. So the organic matter, the dead plants and dead phytoplankton that got buried with them, they just basically eat it super, super slowly. So it's like, if you got given a pizza and then said, this is all you're getting for the rest of your life, make it last. So that's, that's kind of how they live.
33:26 Sean Carroll? And there's definitely an idea that all of the time scales are much slower, right? You know, there's, there's no rush when you're down there, and I guess that makes sense because your resources are stretched a little thin. You don't want to use them up too quickly.
33:41 Speaker 03 Yeah, you can't, you can't rush. You know, if you, if you're late for a meeting and you want to run to that meeting, you may not run as quickly if you didn't eat breakfast.
33:51 Sean Carroll? Right.
33:52 Speaker 03 You know, these guys have, have never had breakfast. They can't, they can't speed up. So they're just kind of chill.
33:57 Sean Carroll? So how, how quickly do they reproduce, for example?
34:02 Speaker 03 We don't know. Well, okay, we know about the cultures. So in the cultures, they will divide, every cell will divide every couple of weeks.
34:13 Sean Carroll? And how does that compare to things we see up here on the surface?
34:16 Speaker 03 Insanely slow. Like every, all the bacteria, like normal microbiology, like when you talk to a microbiologist and say like, oh, you've got a culture. How long does your, your culture, what's the cell division rate of your culture? They'll usually say something like, oh, it's really fast. It divides every half hour like E. coli, or they'll be like, oh, it's such a pain in the butt. It takes two hours to divide. But you still, it means that you can start a cell culture at the end of the day, go home, go to bed and come back the next day. And then you'll have a nice, fully grown sample waiting for you to work on. And that's true for the vast majority of things that we study in lab, including the archaea. You know, I used to work with a, a methanogen that grew at 100 degrees Celsius. So extremophile, tough place to live.
35:01 Speaker 03 It ate hydrogen and breathed CO2 and made methane from it. And so I would make this culture that was perfectly clear. It looked like a terrible place to live and I would throw it in a vat of boiling water. And then the next morning I would have this like happy growing culture so fast. So it's not, it's not that archaea can't be fast or obviously we know bacteria are fast because that's where all the pathogens are. These guys, they're never going to get to that big turban culture. And they're only going to divide once every couple of weeks. So the idea of performing experiments on their physiology in the way that we would for something that we can grow quickly in lab is, is a, is a non-starter.
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36:23 Sean Carroll? And this once every couple of weeks is in what is presumably ideal circumstances for them.
36:28 Speaker 03 Oh, yeah.
36:29 Sean Carroll? You're giving them food and whatever, so maybe underneath the surface, they're actually waiting even longer.
36:33 Speaker 03 That's right. That's what we think. And so, we're trying to get at how quickly they grow in these natural systems. And we can get it in a couple of ways. We can look at how much energy they have available, because we can measure all the chemicals around them. And we can measure how quickly those chemicals go away, because we can see that the sediments are layered. So the sediments act like a recorder tape, like a time recorder tape of how these things are used. And so, we can, basically through differential equations, figure out the rate at which this food is being used by the whole community. And then, when we run those numbers and calculate exactly how much energy everyone has to go
37:15 Speaker 03 and rush to their meeting, or whatever they've got to do, it is 1,000 to 10,000 times less than anything that's grown in lab would be able to survive on. So, it's like, there's probably lots of errors, and there are definitely errors in our calculations, because we're inferring things. But when your conclusion is, you know, 10 is like 3, 4 orders of magnitude off from what you know, then you can be off by 2 orders of magnitude, and you're still right. So, basically, what all this means is that they're not growing.
37:55 Sean Carroll? They're not growing at all. They're very slow.
37:57 Speaker 03 Which is crazy.
37:59 Sean Carroll? Do I remember correctly that when a bacterium divides, maybe this is true for archaea as well, they're not exact, exact duplicates, the 2 offspring, but one is like the older one and one is brand new. Is that correct?
38:13 Speaker 03 Yeah. Yeah, because a lot of bacteria will make an old pole, so that it's a polar cell division. And you put all the old proteins and stuff on the old pole, and so you end up, you don't have to spread that stuff to a daughter cell. You can make a fresh daughter cell with younger proteins, and that's a good strategy.
38:31 Sean Carroll? So, in principle-
38:33 Speaker 03 I don't know if they do that or not.
38:34 Sean Carroll? A bacterium could die of old age.
38:38 Speaker 03 Yeah, they should.
38:41 Sean Carroll? If you just keep accumulating all the old stuff on one side and making everything new. So, so some of these, is it mostly bacteria that you're getting up from down there? Mostly archaea?
38:55 Speaker 03 Um, we used to debate a lot about that. And then I basically, we never settled it and we just kind of got bored of the debate. We stopped doing it. That used to be a really hot topic, but it's funny how like everybody runs after something. I think it's, it's pretty clear that there's a lot of both of them.
39:10 Sean Carroll? There's a lot of both. Okay. But we can imagine that some of them are, you know, in this sense that bacteria could die of old age or whatever. Some of these critters are very, very old. You know, maybe they haven't been dividing every week. They've been dividing every year or whatever.
39:25 Speaker 03 Yeah. It's, I mean, that's, we're not dividing at all. I mean, they have to replace broken parts. Like you can't, you can't maintain a cell for thousands of years without any effort into keeping it put together. And one of the things that we measure to, to actually make measurements of this is, um, do you know about the chirality of amino acids?
39:47 Sean Carroll? I do, but let's imagine that not everyone else does.
39:49 Speaker 03 Okay. Okay. So, um, so chirality is basically just handedness. So you can have the same molecule, but you turn around sort of what, what face, uh, different, um, parts of the chemical are sticking out of. So it, it functioned chemically, it's the same. It doesn't have any different chemical function, but it can be distinguished by something that can recognize the handedness and, and chirality is handedness because our, our two hands are chiral. They all have the same fingers, but you can't perfectly overlay them, um, because the front and the back are different. Okay. So that is also true for amino acids, which are what make up proteins. For some reason, this is still one of the big mysteries of life.
40:29 Speaker 03 All of our proteins and all the proteins in all life as we know it has one handedness. It's one type of chirality. So if you take a living organism like a person or a cell and you kill it so that it can't do any maintenance to itself, it will naturally revert to a random mixture of the two types of chirality of its amino acids.
40:54 Sean Carroll? I know that.
40:55 Speaker 03 Just from the background, yes, just from the background. It's a great little time recorder of how long it's been since something has died. Of course, this process is super slow, so you need something. This is not useful in forensics. This is useful for things that have been dead for, you know, millennia. We can measure the ratio of the two-handedness of the amino acids in these sediments, and we can see they're keeping them alive. They are not letting everything go to this random mixture of the two hands. So it means that they are maintaining themselves. But to maintain chirality, to maintain membrane integrity, to keep your DNA intact, to do
41:36 Speaker 03 all these maintenance things to make your body whole, you don't necessarily need to actually undergo cell division.
41:44 Sean Carroll? Okay, good. So my... Go ahead.
41:48 Speaker 03 So when we make estimates of growth rate, it's not necessarily making new cells. It's the amount of time we estimate it takes to make, to recreate your body so that you are intact.
42:01 Sean Carroll? So for at least some of these microbes, they're basically sitting there doing what to a person would look like almost nothing. They're just sitting there. They're not even dividing. They're not moving. They're not going anywhere. But you're telling me that at the micro level, they're still engaging in self-repair?
42:20 Speaker 03 Yeah. And, you know, and sometimes I'll have, you know, when I explain this to people, sometimes people will say, "Well, why study them? They're just dying. They're not..." But, you know, I mean, we are too.
42:31 Sean Carroll? We're all dying. That's no reason.
42:34 Speaker 03 Yeah. Everybody's on their way, you know? So what is happening in their lives? It's just their lives are potentially lasting for millennia.
42:44 Sean Carroll? Right.
42:45 Speaker 03 So what does that life look like?
42:47 Sean Carroll? Is there some possibility that these are the longest-lived organisms on Earth?
42:52 Speaker 03 I would say there's a good chance they are the longest-lived organisms on Earth.
42:56 Sean Carroll? If only they could talk.
42:58 Speaker 03 I know.
42:59 Sean Carroll? What stories they could tell. Well, they're probably underground all the time.
43:02 Speaker 03 Arms. You can teach them sign language.
43:05 Sean Carroll? So you say that some of them survive off of the detritus that sort of seep down from the surface world, but maybe others don't? Are there clever little microbes that are just living off of the chemicals?
43:23 Speaker 03 Yeah, for sure. So there's a really cool background thing that happens everywhere in Earth's crust for free, which is radioactive decay. And so there's tons of, when Earth accreted, we ended up with a lot of radioactive elements. And I'll say this for your listeners because I'm sure you know this, Sean, but radioactive elements are ones that spontaneously fall apart. And when they do that, they release a little bolus of energy of different sorts. And so no matter whether it's alpha, beta, or gamma type of radiation, when that interacts with pure water, it will, some of it will split apart the water into hydrogen and oxygen.
44:03 Speaker 03 And this is not by and large a very exciting process that's going to make us a lot of hydrogen that we can pull out of the ground because it's for our own energy, just simply because it is a slow process that's happening in the background all the time. But if you're already a slow microbe, you can actually live off of the radioactive decay of water, which is kind of cool.
44:27 Sean Carroll? I mean, you're telling me there's a race of subterranean dwellers in the dark that live off of radiation. So this sounds like a movie.
44:36 Speaker 03 Yeah, I'm telling you that.
44:38 Sean Carroll? Happily, they move very slow, so they will not be invading the surface world anytime soon. And I think I remember reading that you said that some of them go so far as to basically live off of electrons.
44:51 Speaker 03 Yeah, for sure, because that's what a chemical reaction is. You know, if you had to take organic chemistry, which I bet you loved, because everybody loves organic chemistry, then you always pushed electrons. You draw those little arrows to move electrons onto something and then, you know, pop the next electrons onto something else until they can be stable on oxygen or something like that. So chemistry that changes the redox, or even non-redox chemistry, often involves the movement of electrons. Certainly, in a redox reaction, it's a movement of electrons. So there are organisms that just cut to the chase and don't deal with the diffusion of chemicals. They just literally move electrons through appendages that are basically tiny little wires.
45:35 Sean Carroll? In the sense that they're like conductive materials that electrons can flow through, yeah.
45:43 Speaker 03 Yeah, exactly. And they're made of proteins that have basically conjugated. So metals work by moving electrons through a conduit where it can move, it can flow. And biological material can also be put together in such a way that electrons can flow through it as well. And so these cells do it.
46:04 Sean Carroll? That, yeah, that is, it's impressive that they can do that. And it's a reminder that it's not the energy that matters, it's the free energy, right? It's the gradient from place to place. Like, just being in a hot environment is not enough, but these little critters are clever enough to take advantage of disequilibria somehow.
46:24 Speaker 03 Yeah, and I think that's one of the things that I'm personally have gotten out of all of these things, is that a lot of the specifics that we attribute to being necessary for life, oxygen, light, you know, space to move around, fast growth, dying after 100 years or 1,000 years, like, none of that is necessary for life. What's necessary for life is what you just said. You gotta have gradients of free energy that you can exploit.
46:52 Sean Carroll? And they're all over the place. I mean, and maybe you need water also? Water seems pretty important.
46:57 Speaker 03 Yeah, it seems pretty important. Yeah, I think you need water. I definitely wouldn't say that you don't need water. But you don't need nearly as much of it as we normally think. You know, we're finding life in ancient permafrost that doesn't have a lot of liquid water because it's mostly in the form of ice, but they still seem to maintain their cell integrity there.
47:18 Sean Carroll? Okay, so maybe we can go back to this question of how they fit into the tree of life. I mean, there's this fun possibility that we've discovered a stepping stone, a missing link between archaea and eukaryotes, but is there more to say about the origin of life or at least like last universal common ancestor kinds of questions?
47:40 Speaker 03 Yeah, I mean, one thing that we're finding with all these things is that they are made up of the same stuff that the rest of us are. So we still haven't removed ourselves from the world of DNA, for instance, which is kind of interesting. You know, we're finding all these extra branches on the tree of life, but they're still using DNA. So at least for life as we know it, DNA seems to be primordial, the last universal common ancestor. It's hard to say where life started from these, but I think they definitely tell us how life has differentiated in a way that we haven't seen before, just how you can end up with the eukaryotic branch.
48:20 Sean Carroll? So, okay, so that's like something that happens after you've already differentiated into bacteria and archaea and other things.
48:30 Speaker 03 Yeah. Oh, you want me to go back to like non-life to there is life?
48:35 Sean Carroll? Why not? We're getting late in the podcast.
48:37 Speaker 03 Why not? I know, I talk about it in the book. It's something that absolutely fascinates me and I can't stop thinking about it, but at the same time, it's hard to really pick a hypothesis that I like because I wasn't there. And we don't know. But one thing that I find helpful is to think about thermodynamics, just simply because, you know, water for sure, but these gradients seem like there's something that is so important. But it's not just having the free energy, it's also about how quickly that free energy can be released through abiotic processes. Because if if it's gonna go, like if that chemical reaction, it may yield you tons of
49:21 Speaker 03 energy and you have a beautiful gradient setup and your free energy is great. But if that if somebody lights a match and the activation energy is is overcome abiotically, that reaction is just gonna go. And that's not what life is good at. Life is better at slowing down the, I'm sorry, speeding up reactions that are blocked for some kinetically blocked, so they're going a little bit too slow. Life can speed up those reactions. But it's there's something interesting about how life does this. And it gets to the second law of thermodynamics, which means that entropy has to increase in an open system.
50:01 Speaker 03 And so life, it seems, is super, super good at making entropy. Just really, really good. And like better than so if you use the burning match example of like methane and oxygen, like we use methane to heat our houses and that creates a ton of heat, that creates a ton of entropy. But if you take that same, you know, squirt of methane and same amount of oxygen and you feed it to a growing culture of a methanotroph, they're gonna make this structure and they're gonna make a society, they're gonna support other organisms, they're gonna the total amount of entropy that gets produced by these organisms is gonna be so much more than you
50:45 Speaker 03 get from just that flash of heat when you when you light a match. And so I that is that I don't have the answer for how life started. I wish I did. But but when I think about it, I just think about this fundamental quality of life in that it stretches out the the free energy acquisition from reactions in ways that do a better job of creating opportunities for entropy production than without life, which is not exactly like a pithy little definition of life that you could like put on a bumper sticker. But, but I think it explains a lot of why life is so complex.
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52:33 Sean Carroll? I think it's actually a super important point because we said, life is not just about having energy, it's about having free energy or gradients or something like that. And now you're saying, and furthermore, it's about, it's kind of about having batteries, right? It's about having energy that doesn't just get released and burned too quickly. Life is sort of making use of the slowness to fuel itself. I don't know if life is keeping it slow or speeding it up, but it is certainly generating entropy.
53:03 Speaker 03 Yeah, and it speeds up individual reactions, you know, like just something that does have a big activation energy like methane and oxygen, you would need to light a match, you know, to have that reaction happen. So it's, it's kind of like it's a catalyst that will make those two things react, but they react much more slowly with more entropy production than it would if you got over that activation energy with just a flame.
53:26 Sean Carroll? I often hear people say, you know, life is working against the direction of entropy increasing by making things organized. And I try to tell them, no, no, no, it's parasitic upon entropy increasing. We need entropy to increase. That's what life is.
53:41 Speaker 03 Parasitic. Maybe we're collaborative, though. But that's it. It's basically like, we need, we need that entropy, you know, we need. I think that it's the opposite of, I know that argument that you're talking about, because I've heard people make it as well, that we're somehow swimming upstream and we break the laws of thermodynamics. And like, no, that's ignoring heat. You're ignoring heat.
54:05 Sean Carroll? It's kind of important, yes.
54:07 Speaker 03 Yeah. I mean, there's also.
54:10 Sean Carroll? Go ahead.
54:11 Speaker 03 Well, I think that there's sort of like a different definition for entropy in the informatics versus in thermodynamics. And so in informatics, it's often used as a measure of just disorder, whereas in thermodynamics, disorder is just a subset of entropy, and it can mean other things as well.
54:32 Sean Carroll? Yeah, it's complicated because there's that factor of temperature that comes in there when you try to relate entropy to heat. And it's confusing, and people will write books on it, and I'm sure they do. But, okay, that's an insight on what life is and what it does. And it's certainly borne out by the experience of, I can't believe we didn't use the word yet, intraterrestrials. That's the title of your book, yes.
54:58 Speaker 03 Intra-terrestrials.
54:59 Sean Carroll? Underground. Does it affect your pre-existing credences on different theories about the origin of life? I mean, there's metabolism first, and replication first, and all these things.
55:12 Speaker 03 Yeah, or RNA first, you know, that it started with information. That's another idea. And the idea that it's RNA first is based on the fact that our RNA as a molecule kind of does all the different things that we need to in a cell. It's sort of like the pre-differentiated molecule. So I think there's a lot of, there's a lot of good, good possibilities in RNA as the, as the beginning factor. But I I think that if you look, if you think about life as this entropy-producing phenomenon, then you can, you can see the continuum with lawn life a little more easily. Because we have organized structures, you know, if you're gonna make the, our straw man argument that I think we both disagree with, that life beats, beats entropy, beats the
55:55 Speaker 03 law of thermodynamics because it's organized, you know, look at a whirlpool as a river moves down, you know, a moving river, if there's a rock, it's gonna create this eddy, and it's a structure. You can see it, there's, there's boundaries to it, you can say what's in the eddy and what's not out, not, not in the eddy. But none of those water molecules are alive, and they're not talking to each other. They're just obeying the second law of thermodynamics. They're just like increasing entropy in a way that they have to. And so, life is kind of doing that too. It's just, we are, you know, the example that I write in my book is that we do the same thing, we're, we're making eddies in the, in the stream, except we realize that we can make a whitewater rafting company based on those eddies.
56:40 Speaker 03 And so, we work within the, we dam the stream, upstream of it, and work with the people controlling the spillover to make sure we have just the right eddy, and then we build ourselves a boat so we can have a great time like flipping in and out of the whirlpool. So, you know, think of all the entropy that's produced there when you buy the photo that they shoot of your family going through this whirlpool, you know? Just, we, we are so good at creating opportunities for further entropy production that are so much bigger than what was there. And that, to me, defines the cutoff between life and non-life. Because, when is it? An RNA molecule's not alive, an RNA world wouldn't have really been life.
57:24 Speaker 03 You know, people can replicate nucleic acids in a laboratory bench, and nobody says that they're God and created life.
57:33 Speaker 03 But to me, it's got to have that feature of making extra opportunities for entropy.
57:38 Sean Carroll? I don't have any dog in the fight about the origin of life, but I know that there are those who, the metabolism first folks, who say that, yeah, this sort of complicated network of chemical reactions that is increasing entropy came first, and later it figured out how to replicate itself using RNA. And that sounds like that's quite a miracle occurring there. But then the RNA folks say, well, there's RNA, and they figured out how to put themselves in a compartment and build an engine and repair themselves. I'm like, that's also kind of a miracle occurring. So I don't actually know what to think.
58:11 Speaker 03 Yeah, I mean, in some ways, I think it's a little bit of a philosophy question. What do you consider to be alive? You know, I think we can all agree that a whirlpool's not alive, but I think we can also see that thermodynamically, it's on the continuum with life.
58:23 Sean Carroll? Yeah.
58:24 Speaker 03 So where do we draw that line? And that's just, that's for our own hearts to decide.
58:34 Sean Carroll? That's perfectly fair, but there is, once we draw that line, there's an answer to the question, literally, where did life start? Do you think that there's some chance that life started deep below the surface? Or is that just, life is so good at taking advantage of opportunities that it eventually drifted down there?
58:54 Speaker 03 Yeah, so either one is possible. I want to say clearly, like, I don't know. Obviously, no one really knows. But, and I know this sounds a little on the nose because I'm a deep subsurface researcher, but I think the deep subsurface is a great place to form life. I mean, if you think about energy gradients at the surface, they're really harsh, they're really extreme. I mean, we have found all sorts of ways to mitigate the damaging effects of our energy gradients up at the surface. We, our skin makes protectants. We put sunscreen on. You know, we need to protect ourselves from this high blast of energy we get from the sun. And oxygen, the same thing. If we didn't have enzymes running around detoxifying the oxygen that we're dependent upon, we wouldn't be able to live
59:38 Speaker 03 in this high oxygen environment that we do. But in the subsurface, things are slower, the gradients are more varied. You do have some high-energy gradients, but they're never going to be like sunlight-high energy. And so you do, I mean, I guess maybe this is an argument for the metabolism first camp. You get all of these overlapping energy gradients. And so you can imagine these networks sort of forming in a way that they would just get blasted out energetically and possibly physically by impacts from other celestial objects.
1:00:12 Sean Carroll? I actually, I like this. I don't think I've ever thought of it this way before, that here on the surface, there's a lot of resources for life, but there's also a lot of dangers. And so you might think that, oh, the resources are so abundant that maybe this is where life began, but you gotta, when you're a primitive life form and you haven't accumulated all those defense mechanisms, the dangers are really important. So maybe like the slow world down beneath the surface where you have time to develop some structure would be a good place to look for the origin of life.
1:00:45 Speaker 03 Yeah, it's like a nursery. You know, you can take somebody who's gonna be like a fantastic leader of a nation, but they can't, they're not gonna do it when they're three months old.
1:00:54 Sean Carroll? Right.
1:00:54 Speaker 03 They gotta figure out how to like eat first.
1:00:58 Sean Carroll? Does that have implications for looking for life elsewhere? I know that you've already, you've already mentioned Mars. I told you we'd get back to Mars. So Mars, Titan, Europa, wherever, like is this opening up possibilities that the astronomers or the NASA folks haven't really taken seriously yet?
1:01:19 Speaker 03 I wouldn't say they're not taking it seriously. I think people are, well, I hope people are pretty well aware that even though we don't see evidence for a lot of abundant life at the surfaces of these extraterrestrial bodies, planetary type bodies, their subsurfaces are definitely fair game, especially Europa. Why should I, I wouldn't put any one over the other because Europa has liquid oceans underneath the ice cap. This is very well known. This is very, very well established. And so when I hear liquid ocean, I just think there's gotta be energy gradients that are exploitable by something. So I would be shocked if we didn't.
1:02:00 Speaker 03 Find life on Europa and Mars, too, doesn't have these modern liquid oceans, but it does have these really evocative whiffs of methane that show up every now and then. It used to be very controversial, but now that we have better monitoring, like they're they're real, like there are methane whiffs that appear every now and then. It doesn't mean that there's life, but if there was life underground, that is absolutely what I would expect to see in their atmosphere.
1:02:26 Sean Carroll? Maybe say more about the methane whiffs. Is this like a sort of volcanic kind of thing?
1:02:32 Speaker 03 Could be. Their volcanoes have been dead for a while and they're really just in one place. The really big difference between the subsurface of Mars and Earth is that we have plate tectonics and as far as we can tell, they never really did. That's why they have the biggest volcano in the solar system, Olympus Mons on the Tharsis Plateau. And that's just so big because nothing ever moved across it. It's just been blubbing up for a long time. But I don't see why that couldn't support subsurface life just the same way that our volcanoes do on Earth. You don't necessarily need plate tectonics, I think, to support subsurface life. The fact that, you know, methane is so great because so many of the reactions that we know about that happen on their own
1:03:16 Speaker 03 without sunlight on Earth create hydrogen and carbon dioxide and formate. And these are the chemicals that are pretty much all these methanogens need to make energy. Of course, then they need things like metals and nitrogen and oxygen to like put their bodies together. But that stuff is all on Mars. That stuff is not as hard of a question to answer.
1:03:37 Sean Carroll? I mean, there's still the huge question of how difficult is it to make that first leap into life? I mean, you're you're making a persuasive case that the conditions on Mars or Europa allow for life to exist, but it had to start somewhere. That I have no opinion about whether or not that's easy or hard.
1:03:57 Speaker 03 Well, it could have started in one of our two planets between Mars and Earth and transferred. You know, we've been we get rocks from Mars all the time and they could have life on them that seeded Earth. So that's that's definitely a possibility.
1:04:10 Sean Carroll? Is there any chance in well, there's this idea that has been floated of a shadow biosphere that there's some there could be at least living organisms that are not related to all the other living organisms. It sounds like that's not what you're seeing.
1:04:27 Speaker 03 No, that's absolutely possible.
1:04:29 Sean Carroll? Okay.
1:04:30 Speaker 03 For sure.
1:04:31 Sean Carroll? But you haven't seen any yet. You don't have any evidence.
1:04:33 Speaker 03 I haven't seen any, but the methods that I use to look for life would miss them.
1:04:39 Sean Carroll? Okay.
1:04:39 Speaker 03 So when I go looking for life in weird places, I use DNA. So if you have a shadowed biosphere that doesn't use DNA, I would, I would miss it with my methods.
1:04:48 Sean Carroll? Okay.
1:04:49 Speaker 03 So, yeah, that's still on the table.
1:04:52 Sean Carroll? Would you be able to find something that had the wrong chirality of amino acids?
1:04:58 Speaker 03 Um, I, yes, I would. Yes. If I'm using the right, I mean, that's not a technique that I do all the time. You know, it's only to ask a specific question, but yeah, we could, we could see, we can detect proteins that are made from amino acids that would have the wrong chirality, for sure.
1:05:19 Sean Carroll? And, and we haven't found any yet, or you would have told me.
1:05:22 Speaker 03 Right. But like I said, you know, in terms of like the real exploration, like discovering new things, that tends to happen through DNA. It tends not to, to happen through, through looking at other molecules.
1:05:36 Sean Carroll? Okay, that's true. So, so it might be there, is what you're saying?
1:05:39 Speaker 03 Absolutely.
1:05:40 Sean Carroll? All right.
1:05:41 Speaker 03 Yeah, 100%.
1:05:42 Sean Carroll? I will, uh, look out for the news alerts.
1:05:45 Speaker 03 Which I think is fascinating. I mean, I think, I think it's, if there's one thing I've learned from this, this career adventure that I've been on, is that there can be stuff out in nature that you never would have imagined existed, and you have to be open to finding it.
1:05:59 Sean Carroll? Yeah, no, no, no. And, and you made a good case also that we haven't explored much of what is down there yet.
1:06:04 Speaker 03 That's right. Yeah, there's a, yeah, it's all on the table.
1:06:08 Sean Carroll? Uh, in, in the, in the theme that everything is connected and all life is connected, is there, you know, um, traffic between the subsurface life and the, the surface world? Like, do they rely on each other or notice each other at all?
1:06:24 Speaker 03 Sometimes. The answer is always yes to all the possibilities that you just presented.
1:06:31 Speaker 03 Some of them, you know, like these ones that are buried in marine sediments, as far as we know, they're totally dependent on the stuff that we that we produced in our rivers and, you know, ran off and or fell down from the phytoplankton in the open ocean. We think that that is what's supporting those communities. And so they are, they are dependent on our detritus. They're dependent on our leftovers and our trash. But the ones that are using the energy gradients that happen, whether we influence it or not, would not be dependent on any of that stuff coming down.
1:07:03 Sean Carroll? Okay.
1:07:03 Speaker 03 And there's probably a mixture of both types in almost every ecosystem.
1:07:07 Sean Carroll? We do have an effect on the world, you know, in various ways, trash included.
1:07:11 Speaker 03 We definitely matter. We definitely, yeah, sometimes our trash is good. They like our trash. And they they come back up to us, too. I mean, they're they're basically like determining what's happening with our redox state of our crust. And the redox state of our crust determines our mineral deposits. It determines how much oxygen is available in the atmosphere. So in terms of how they affect us, you can't underestimate the importance of these organisms on us over over the course of Earth's history. They they have made the world that we now use.
1:07:43 Sean Carroll? Is there any chance we could put them to work further? I know that we have, we're messing with our climate in sort of dangerous ways. Is that something that people have wondered? We could, you know, eat up the extra CO2 in the atmosphere or something?
1:07:56 Speaker 03 Yeah, it sounds kind of crazy, but they could actually do that for us. You know, if you think about, if you really take our climate problem down to like its sort of dumbest explanation, there was a lot of carbon in Earth's crust. Humans, because we're great at producing entropy, took all that carbon from fossil fuels and natural gas, and we are putting it into the atmosphere. And that is causing an imbalance that is causing problems for for us. So putting that carbon back down underground makes a lot of sense. That's just in some ways reversing what we've done. We can't just like make fossil fuels out of it, but we could maybe stick it underground. And so that is happening. Iceland has a
1:08:37 Speaker 03 Company that is doing this, they're capturing CO2 out of a energy production plant and piping it underground and it seems to be working a little bit.
1:08:47 Sean Carroll? Okay.
1:08:47 Speaker 03 They also did this in Louisiana on one of these test wells and that caused some problems because it's not just like an empty Tupperware container that they're sticking this carbon down into, there's things living down there, that's what we're learning about the intraterrestrials and some of the ones in some of these wells are producing methane out of it, which is not, not what we want because that's not actually going to sequester the carbon.
1:09:10 Sean Carroll? Yeah, it doesn't help.
1:09:12 Speaker 03 Yeah.
1:09:13 Sean Carroll? Okay.
1:09:13 Speaker 03 So we don't know, we're, we're working on, that's, that is something that I think that our field can be very helpful for going forward is if, for any, for any technology that is trying to sequester carbon and draw down CO2 in the atmosphere by sticking it underground, call up a microbiologist before you do that and make sure that it's actually going to stay there.
1:09:33 Sean Carroll? Very good point, call up your local microbiologist.
1:09:36 Speaker 03 Call your local, yeah, because they're doing extension work.
1:09:39 Sean Carroll? In the, so for the final question, let, let's imagine that we're in a happy world where science is extraordinarily well-supported by society and you can imagine the experiment or experiments you want to do. I mean, again, I think you have a compelling case, there's a whole bunch of living critters under the ground that we don't know anything about, that's something we can go look for. What would we do? What would, what, how would we actually experimentally or observationally learn more about these things that we're not doing now?
1:10:10 Speaker 03 I think we need to attach ourselves to a lot more drilling. You know, that is the most expensive way that we have of getting down and so we, you know, we do talk to companies, you know, there's a lot of different companies in oil and gas and in mining who are excited to have scientists learn what they can and that's been incredibly helpful to our field. But just being able to direct the drilling ourselves, drilling a borehole costs a million to $10 million.
1:10:37 Sean Carroll? Okay.
1:10:38 Speaker 03 And so that's something that needs an actual investment, it's often an international investment, but that's, that is absolutely the thing I would say is we need to go down, we need to be able to control the, the places that we drill and the things we drill into, which, you know, we have been able to in the past and, and I don't. I don't want to be flippant about this. Getting these drilling proposals funded is highly competitive. You have to be really good and really know what you're doing to get one of these projects. So it's not like we were being willy nilly. But now that that program is over in the United States, we don't do that anymore.
1:11:12 Sean Carroll? Is there at least a feeling in the field that things are taking off? That, you know, this is a new, exciting area? Do people recognize this?
1:11:22 Speaker 03 Yeah.
1:11:23 Sean Carroll? Okay.
1:11:23 Speaker 03 Absolutely. Like within those of us who are studying this, I mean, I cannot overemphasize the majesty of these two groups who have managed to culture these guys. I really didn't think it was possible. I mean, not that I would say that. I really didn't know if it was possible. But the fact that they've managed to do it has really changed my view of how we can interact with these organisms. And it turns out we can actually do more with them than I ever would have thought possible. And we need more of that. So we just need to replicate what they're doing and get the rest of these things in culture and start studying all of these things. That's going to take a huge effort.
1:12:03 Sean Carroll? And you promise along the way not to release a new pathogen that will wipe out all eukaryotic life on Earth?
1:12:10 Speaker 03 Promise is a big word.
1:12:13 Sean Carroll? Plan.
1:12:14 Speaker 03 There's an interesting, in terms of like fears on that notion, I don't know if you know this about Archaea, but that entire domain of life has no pathogens. It's one of the greatest mysteries of Archaea. They commensal, they live in our guts, they're with us all the time, and for whatever reason, they've never decided to take advantage of us.
1:12:33 Sean Carroll? So viruses and bacteria, obviously like super pathogenic when they're in the wrong forms, but Archaea, just like right along and they're chill?
1:12:42 Speaker 03 Yeah, they just, you know, they're lovers, not fighters.
1:12:46 Sean Carroll? All right, don't let them know that. They're going to start exploiting this loophole that they didn't look into before.
1:12:51 Speaker 03 Yeah, exactly.
1:12:52 Sean Carroll? Karen Lloyd, thanks so much for being on the Mindscape Podcast.
1:12:55 Speaker 03 Yeah, thank you so much for having me. Interesting conversation.
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