As scientists continue to explore the Earth, they’re discovering life surviving and even thriving in extreme environments. What hints can this give us about what we might find as we search for life on other worlds?
Two miles underground, strange bacteria are found thriving (Princeton University)
Facts About Tardigrades (Live Science)
5 Extreme Life-Forms That Live on the Edge (National Geographic)
Cold-Loving Bacteria Offer Clues for Life on Mars (Live Science)
Life Below the Limit (Astrobiology Magazine)
You Should Know About This Chernobyl Fungus That Eats Radiation (Popular Mechanics)
Life On Earth’s Ceiling (Astrobiology Magazine)
Martian brines might sustain life, study finds (Cosmos Magazine)
NASA InSight (NASA)
If life exists on Titan, it’s even weirder than we thought (Popular Science)
Methanogens: pushing the boundaries of biology (Portland Press)
Cyanobacteria: A Precious Bio-resource in Agriculture, Ecosystem, and Environmental Sustainability (Frontiers in Microbiology)
Red-Spotted Toad (National Park Service)
The Bizarre Planets That Could Be Humanity’s New Homes (The Atlantic)
Space Opera by Catherinne Valente (Bookshop.org)
Molecular Structure of a Mineral/Water Interface: Effects of Surface NanoRoughness of α-Al2O3 (0001) (The Journal of Physical Chemistry)
What is a hydrothermal vent? (NOAA)
Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast Episode 586: Life as we know it: Habitable Exoplanets and Extremophiles. Welcome to Astronomy Cast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always is Dr Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey Pamela. How are you doing?
Dr. Pamela Gay: I am doing well.
Dr. Pamela Gay: I am doing well. We determined yesterday that North America is filled with hobitsees because Canada has first Thanksgiving in October, and we have second Thanksgiving here in America –
Dr. Pamela Gay: – or United States. So, yes I enjoyed second Thanksgiving yesterday.
Fraser: I’ve made the case in the past. I really think that folks in the US should adopt the Canadian Thanksgiving holiday. The weather is better, so the travel is easier. It’s just all-around a better time of year to hold – to attempt to bring an entire family together to one location. I – just take it under advisement.
Dr. Pamela Gay: This year I’m okay with having as many barriers as possible to prevent people from getting together, but –
Dr. Pamela Gay: – in future years I’ll consider your offer.
Fraser: So, before we get going on this week’s episode, I wanna let people know that I’ve made a slight change to what I do with Universe Today and the newsletter. So, for people who may or may not know, I let anyone use content on Universe Today for any reason whatsoever. So, if you wanna take our article and republish it on your website, be our guest. If you wanna use it on your newsletter, go ahead. If you wanna use it for the script of your radio play, you have my permission. Only the words. Not the pictures. We don’t own those. We own the words. We don’t own the pictures.
But I put the Creative Commons license on every page on Universe Today as well as the newsletter, just to make it really super clear that you have our permission to use our content. And so, when you see my articles stolen on some other website, it’s not possible to steal my articles. And that is a huge thank you to – especially to the patrons, who I’m able to then pay for the writers. And the writers are all – understand that this is the way this rolls. And all we ask is that if you are going to use our content, that you give a link back to the original source.
But most importantly, show who wrote the article in the first place. In this modern age, the only thing that we can really rely on is our personal reputation. And one of the things that I really wanna do with Universe Today, is help writers build a name for themselves and a reputation in an industry that really doesn’t have a lot of job security, even from me. So, I’ll pay them for now, but also I would love it that they can have – build a name for themselves so that in the future they can use that as their portfolio. And so if you take their article and you don’t give them credit, then you’re stealing their future.
Dr. Pamela Gay: Yeah. And we release everything here on Astronomy Cast and CosmoQuest the exact same way. We really believe in, basically, open licensing. Get the information out there and promote the people creating the information.
Fraser: Exactly. So, there you go.
Dr. Pamela Gay: And if you create something really cool, make sure you get our attention so that we can see it, and we’ll lift up what you do as well.
Fraser: Yeah. So, in the past I’ve guaranteed you will never get a copyright infringement message from me. Now, I am legally bound to not be able to send a copyright infringement to you. So, all right. Let’s get into this week’s episode.
As scientists continue to explore the Earth, they’re discovering life – surviving and even thriving in extreme environments. What hints can this give us about what we might find as we search for life on other worlds? All right. This is of course one of our favorite topics. Life in the universe, where is it? Isn’t it funny that people always accuse us of being part of the vast conspiracy that’s hiding the search for life in the universe? And it’s literally most of what we talk about.
Dr. Pamela Gay: We want there to be life, humans. We want it to be out there. This is our deep – I’m a sci-fi lover. I really am. Let’s go meet those aliens. The smalls ones that can’t hurt us. But first of all, you can’t trust a scientist with a secret most of the time because we get too excited about we do. And we periodically drink alcohol and yeah… you can’t trust us.
Fraser: It’s like that discovery of phosphine on Venus. It was the worst kept secret in all of space and astronomy. We all knew what was coming even though it was all under embargo. Not a secret. But anyway, that’s a – we’re kind of rabbitholing as we do. So, let’s talk about the – I don’t know. I feel like it’s – I always use this term golden age, but once again weirdly we’re in this golden age of astrobiology. And yet astrobiology has not done the one thing that it’s supposed to do.
Dr. Pamela Gay: I’d say renaissance. We’re at that –
Dr. Pamela Gay: – point –
Dr. Pamela Gay: – where we’re coming out of the Dark Ages of everyone being told, “You can’t talk about this. You can’t think about this. We won’t fund this.” To the, “We’re gonna go looking for it. Let’s everybody think about it.” Everyone. It’s a renaissance of astrobiology. And in part, it’s driven two-fold by the realization – There’s water on Mars. It’s briny, but it’s there. And the realization that you can’t dig, burrow, dive, or travel anywhere on our world and not find some sort of life there.
Fraser: So, you’ve got this conflict. On the one hand, you’ve got life reaching into every nook and cranny of the entire planet…pretty much no matter how extreme it can be. And then on the other hand, you’ve got those conditions starting to show up on other worlds in the solar system.
Dr. Pamela Gay: And so, as we start finding life in the weirdest of weird places, we find it harder and harder to imagine that life hasn’t come to find a way to fill all the super weird places on other worlds. What’s your favorite form of extreme life?
Fraser: Sure. So – well I mean, there’s a couple. But the – I mean obviously everyone wants to talk about tardigrades. But the one that I like are the Pompeii worms which are the – so, at the bottom of the ocean – you’ve got the hydrothermal vents that are blowing water out into the bottom of the ocean. And they can range in temperature from 30 Celsius up to about 200 Celsius.
And so you get these worms…the Pompeii worms…which will – which build these tubes that attach to the hottest – the black smokers. And at the bottom of the worm’s tunnel, it’s about 150 to 200 Celsius. And then at the top of the worm, it’s about 50 Celsius. And so the worm can handle this change in temperature from – its entire body has adapted to handle this change in temperature from the – right where the water is pouring out of the – out of the black smoker to the top where it’s mixing with the colder seawater. And it keeps its face side up, and keeps its butt side down.
But it’s an animal. It’s not just a cyanobacteria. It’s an animal that is able to handle just a ridiculous environment. There you go. That’s my favorite.
Dr. Pamela Gay: Okay. Okay. That is a thing. So, for me it’s the life that they’re finding two miles under the surface of the Earth as folks go digging for gold in Africa. They have found down in some of the South African mines – crustaceans, flatworms, random arthropods just hanging out two miles beneath the surface. No light. Just termites. That’s one of the things they’ve found down there.
Fraser: Termites miles down.
Dr. Pamela Gay: And the idea that you can have an entire ecosystem two miles under the Earth in the soil… it’s just absolutely amazing.
Fraser: That’s incredible.
Dr. Pamela Gay: Yeah.
Fraser: And not to mention, you’ve got the…the life forms like cyanobacteria and various kinds of fungi, and of course the tardigrades, which recently were sent to the International Space Station. They opened up the pod bay doors and they kicked those life forms out into space, like someone was playing Among Us. And a year later they brought them back in and checked them out, and many of them not only survived but thrived.
Dr. Pamela Gay: The only thing that is found to readily kill tardigrades is Google phones. There was an experiment a few years ago where Google was working on a phone that had a modular design and you could buy different modules to put together to build the phone of your choice. And one of the modules they had available had a little tiny digital microscope and tardigrades. And this really bright light came on whenever you wanted to see your tardigrades. And it was discovered that the rapid desecration that these critters went through trying to escape the light would kill them. So, expose them to space. Expose them to what you will. They will live. Just don’t put them in your cell phone.
Fraser: Right. So, let’s talk about then at this point based on the current thinking from astrobiologists, how far – how extreme is life here on Earth? Where can you be sure to find it from region to region?
Dr. Pamela Gay: So, you can find it out to temperatures as high as 200 degrees Celsius which is one that broke my brain. You can find it as cold as -25 degrees Celsius.
Dr. Pamela Gay: You can find it at PHs greater than 11. You can find it at pHs as low as -0.06, which is not something I knew the pH scale did, but apparently it does.
Fraser: It goes into negative numbers?
Dr. Pamela Gay: In some of these acidic mine drainage and volcanic springs, basically the scale gets broken.
Fraser: It’s like the magnitude scale for stars.
Dr. Pamela Gay: You can find it basically in high pressure environments where the pressures are 1100 bars, not millibars. Bars pressure down in the depths of the Mariana Trench. You can find it in highly selenic environments, which is part of what gives us hope for Mars. So, here they’re finding, basically, put as much salt as you can into water until it’s super saturated solution and you can still find life.
And then you find things at highly dry environments out in the Atacama Desert, in the McMurdo Dry Valleys of Antarctica. And then as I said, deep in the crust of the Earth we also have radiation eating bacteria that have been discovered with nuclear power plants. And then there’s all the life that is just happily living in the hot acidic springs, happy as happy can be with the high metallicities. So, like cadmium, cobalt – all these things that would happily kill most life – there’s still an extremophile capable of being happy with all those metals.
Fraser: Right. And that’s just on the surface of the planet. You can up into the atmosphere, pretty much to the ozone layer, and find bacteria and other animals suspended, flying around happily in the atmosphere. Really it’s just like as soon as you get above the ozone layer and the radiation is too intense, that’s where it stops. Crazy.
Dr. Pamela Gay: And that’s pretty much what it takes…yeah…yeah.
Fraser: So, then let’s take that. So, now that we know that life can handle all of these extremes, let’s map that to some of the places in the solar system where we think we might be able to find similar environments.
Dr. Pamela Gay: So, Mars is the low hanging fruit. This is a world that we know has water. We believe it has liquid water that’s extremely salty. This is a brine that could exist below the surface. There are caves, lava tubes, other geologic features, that can protect life from the radiation if it needs to be protected from the radiation of space. So, it’s quite possible that there is cave life on Mars. Subsoil life on Mars. We don’t imagine it’s big. This could be a lack of imagination on our own part, given what’s found in gold mines. But currently, it’s perfectly reasonable to imagine that there’s bacterial life there.
Fraser: Unless there’s something really surprising, you could take a scoop of this briny material underneath the surface of Mars, pour it here on Earth, and it would – give it sunlight and or some form of energy, and it would probably quickly be colonized by some form of life from Earth.
Dr. Pamela Gay: And rather than doing that and potentially committing genocide of some perfectly happy microorganism, I’d much rather take an actually functioning version of the mole on insight that has a microscope and light source, and let it dig and look around and see what it’s capable of finding.
Fraser: You just have to be able to get down a couple of kilometers below the regolith on Mars, which is not going to be easy.
Dr. Pamela Gay: Well, it’s unclear that you have to get that deep down before you start finding liquid water beneath the surface. So, if it’s just a few meters down, things are gonna be really different. But that’s Mars, which is a fairly inhospitable place that doesn’t have a real atmosphere, that doesn’t have vast amounts of subsurface water that isn’t trapped in minerals or frozen. It appears to have a lot of subsurface glaciers potentially. But, while life is found in desiccated ice, it’s not the easiest environment.
Dr. Pamela Gay: If you want an easier environment, there’s the worlds of Titan and Europa. And with Europa, we have a icy shell that is perhaps only a couple of kilometers thick in a few places, and then reaches down to huge depths and perhaps has its own forms of the Mariana Trench. These places that have smokers…that have geological heat sources down beneath. And there’s some amazing artwork that has been done, and even used by NASA showing sea cucumbers and other multicellular organisms that are complex, living in that watery environment. We can imagine these things. We don’t know if they’re there. But we can imagine them. And that’s awesome.
Fraser: And I mean, and that’s even a more direct comparison that there is absolutely places on Earth that are environments that are very similar to that. And Earth life forms would be glad to inhabit those kinds of landscapes. Now you mentioned Europa, and of course is all to Enceladus. But you mentioned Titan. I mean Titan is like Europa, but it’s got an extra cork, which is, that it’s got all these hydrocarbons on its surface to add to the complexity of it.
Dr. Pamela Gay: So, Titan is a giant moon of Saturn. It’s surrounded by a rich methane atmosphere. It has liquid ethane and methane, forming lakes on its surface. It’s at this combination of temperature and gravity that allows that methane, ethane to have a water cycle just like water has here on Earth…showing that triple point of being able to exist as a gas, as a liquid, and as a solid.
Now, with that triple point of methane creating a methane cycle within the atmosphere, you have to start thinking about methanogens. A form of life that once occupied are own planet in vast amounts. And it has a different metabolism. It’s not out there looking for oxygen like we are. And that may make it possible for methanogens to exist. And there’s been some evidence that the chemistry of the atmosphere of Titan isn’t balanced out in a way that we can necessarily explain well. It doesn’t appear to be in chemical equilibrium.
So, as with so many worlds in our solar system, we find ourselves saying things like, “There’s either some geological process going on that we don’t know about” – which I can guarantee that is happening, or there is life…or both. There is a geological process we don’t understand, and, there is life.
Fraser: Now we’re, – I mean this is us talking about Earth based extremophiles, worth life as we know it. And then finding that in other places. And so, there could be an entirely different kind of ecosystem on Titan that is using a different kind of liquid solution for the chemicals to be able to mix around with.
The solvent here on Earth is water, and that’s why we’re always looking for water. There could be all manner of different life as we don’t understand it – flavors out there, which is totally different. But even in its current situation, because Titan has this vast water ocean underneath, because it has all the chemicals for life on the surface, there could be some kind of mixing that’s going on…from surface, to under the ice. And that’s exciting.
Dr. Pamela Gay: And this is where it gets so frustrating that we have the technological abilities to start going and looking, but it’s extraordinarily expensive and also extraordinarily hazardous to any potential life that might be out there. So, we want to go looking. But at the same time, the more things we try and land on Titan, the more likely we are to carry our own life there and accidentally set off some sort of a genocide that we never intended.
Fraser: Yeah. And I guess that’s why these experiments where people are spacing various extremophiles to find out how they handle it, and finding that they’re doing just fine. Thank you very much. Is showing us that Earth’s life is far more resilient than anyone really ever gave it credit for and that we do have to be careful when we start to explore these other worlds that we’re not – and we’ve joked about this in the past, right? That every time you just take a sample of Orio, like huh. More cyanobacteria and water bears. That’s weird. It’s tardigrades and cyanobacteria everywhere we look across the solar system. I wonder how they got there. It’s like Veigar.
Dr. Pamela Gay: Keep your tardigrades to yourself, people. Keep your tardigrades to yourself.
Fraser: Yep. So, we’ve talked about the water environments on Mars. We’ve talked about the ocean worlds of Enceladus, Titan, Europa. And in fact, probably all of them. Ganymede, Callisto, Pluto even maybe. So, let’s talk about Venus as a place for extremophiles.
Dr. Pamela Gay: And we are still waiting for final word on was the phosphine detection solid or not. So, we understand do not add us that Venus may or may not actually have phosphine detected in its atmosphere. So, it is possible that in the convective circulation of droplets in the atmosphere of Venus, you can end up with a life cycle such that droplets that seed around small haze particles. Those haze particles might be spores.
And as the droplets form around this haze, the drops can get lofted up into the atmosphere gathering more moisture around them as they do, and creating larger and larger droplets that sometimes collide allowing different spores from different droplets to interact as they become life forms rather than just desiccated spores. Capable perhaps of reproduction of exchanging genetic material and eventually as this material lofts up, well, the cycle brings it back down causing it to desiccate back out and rejoin that haze layer.
Now, in this kind of a life cycle, the life is airborne its entire existence. It’s small. It’s confined. It’s a temporary drop. But this isn’t something unfamiliar to us. Well, we don’t normally look for life cycles of desiccation and rehydration in our own atmosphere. We do see it in deserts where there’s life forms that completely desiccate out. Things as complicated as frogs, that then as soon as it rains will reemerge. Will go through their life cycle in rapid fire, having tadpoles in puddles and then desiccate back out again.
Fraser: That’s amazing.
Dr. Pamela Gay: Life finds a way.
Fraser: Yeah. Now, we’ve talked about the environments that we know of here in the solar system. What are some extreme environments that we don’t have, but other worlds around – potentially the Milky Way?
Dr. Pamela Gay: Well, one of the most exciting results for me although I don’t think I really realized it in the moment, that came out of the AAS meeting we were at in Hawaii last year, was the realization that tidally locked worlds are capable of having habitable atmospheres. Where it is possible that there are places in that amazing wind storm that water can exist at the surface. That temperatures can be reasonable.
Fraser: Yeah. It’s funny, I did an interview last year with someone who works on this and sort of having this conversation. And the expectation is the front, the side that is tidally locked is gonna be completely bone-dry, incredibly hot. And then on the back side of the planet it’s gonna be completely dark and totally frozen and then the only place it will mildly habitable would be just this edge around the Twilight Zone of the planet. And the researcher said, “No, no. It’s the whole planet facing side, because of the air circulation – the winds. It’s redistributing the heat away from the front side. It would be like a jungle on the one side of the planet that – where the sun never goes down, with high winds.”
Dr. Pamela Gay: Yeah. So, there you have basically a requirement that everything acts more like a willow tree. It needs to bend and be able to sustain the constant storms but that’s not something we’re used to. But it’s something that’s possible. And anyone who’s lived in Chicago understands what this feels like.
Fraser: Oh, so maybe it’s not just possible but it’s like Chicago, or more.
Dr. Pamela Gay: Yeah. Exactly.
Fraser: Jungle Chicago. But then another possibility is worlds that are all water. Or at least are – they have oceans that are hundreds of kilometers deep and no land whatsoever.
Dr. Pamela Gay: And this is actually fairly easy to understand and has been the imaginings of science fiction writers. I just finished reading the book Space Opera, which is a delightful romp and I highly recommend. And one of the things that just kind of gets commented on in passing is, life from watery worlds has it so much harder becoming spacefaring. Not just because, well, when you live underwater it’s harder to see the stars, but when we fly into space we have to carry our atmosphere with us. Now, imagine that we were dolphins and had to carry all of our water with us as well.
Dr. Pamela Gay: So, that becomes much harder to do.
Dr. Pamela Gay: So, those worlds may not be as spacefaring as we might wish.
Fraser: And even not as nutrient-rich. Because –
Dr. Pamela Gay: Right.
Fraser: – because you may not be able to have a way that the teleguric layer, the mineral layer can interact with the water layer. That as you go deeper, and deeper, and deeper, the pressures of the water get higher and higher and hotter and hotter, that it turns into sludge. It turns into this high pressured gloop that then you don’t get this nice mixing with the minerals down at the bottom of the ocean. And so it could exist, but it might actually be very difficult to get that life going.
Dr. Pamela Gay: It all depends on what the topography is and what the situation for volcanic vents is. As long as you have volcanic vents that are out gassing and oozing and spitting out metals, you’re in a better position. But if you have a geologically quieter world, it’s gonna be a hard go.
Fraser: Yeah. Yeah. And so, too much water is a bad thing. Absolutely fascinating and I – it’s exciting that we’ve got all these worlds to practice on here in the solar system before we can then start to turn our telescopes on other worlds around the Milky Way and try to see what’s out there. Yeah. Incredible. All right. Pamela, thank you so much. Do you have some names for us this week?
Dr. Pamela Gay: I do. And this Thanksgiving week, I have to admit it hit me particularly hard just how amazing it is to have all of you out there. Right now in the United States, they’re estimating that something like 40% of the people in our country are having food scarcity issues.
Dr. Pamela Gay: Where they don’t know where all their meals are coming from. And I realized that because of everything you people out there do to support us, we’re paying Richard. We’re supporting all of our staff at CosmoQuest: Aviva, Beth, Ally, Annie. We have Fraser’s able to support his amazing staff of young science writers and Chad. And everything you do. You are actually making it possible for people to know where their next meal’s coming from, know they can pay their bills. And we’re able to get through these crazy times because of your donations.
Fraser: Yeah. And just a reminder, neither of us take a salary from the Astronomy Cast. We don’t get paid for this. We do this to – because we’d probably just be yapping about space and astronomy to anybody who’d listen. But we do this to communicate and to share this information, but also to try to give people work.
Dr. Pamela Gay: And there’s not a lot of jobs for science writers right now. So, thank you for allowing us to science and to support a bunch of people who help us science. So, I would like to thank this week – I wish I could go through it and thank all the hundreds and hundreds of you. But I don’t have time for that.
Dr. Pamela Gay: So, I’m gonna thank Dean, Naila, Sean Freeman who’s Blixa the Cat, Bart Flaherty, Gabriel Gauffin, Shawn Humber, Ryan James, The Air Major, Nial Bruce, Kimberly Rieck, Frode Tennebø, Alex Raine, Justin Proctor, Daniel Loosli, Neuterdude, Joe Wilkinson, Claudia Mastroianni, Eran Segev, Matthew Horstman, Thomas Tubman, Kseniya Panfilenko, David Gates, Paul L Hayden, Omar Del Rivero, John Franswell Rajae, Arthur Latz-Hall, Mark Gwendi, William Lower, Jay Alex, Alex Anderson, Mark Steven Rasnake, Jeremy Kerwin, Brent Krenop, Bruno Leitz, Tim Gerrish, John. Just John. Michelle Cullen, Brian Kilby, Marco Larossi, Dustin Ralph, Martin Dawson, Rachel Fry, Anitusar.
Fraser: Thank you everybody. And we will see all of you. We’ve got four episodes coming up on Lunar Exploration. So, buckle up. It’s gonna be a – if you’re excited about the moon, we’re gonna cover it from North to South pole. All right.
Dr. Pamela Gay: And what’s awesome is there may be a star ship hop while we’re talking about it.
Fraser: Next week?
Dr. Pamela Gay: Yeah.
Fraser: Okay. Yeah. That’d be great. Unless they cut into our ratings. Okay. See everyone next week.
Dr. Pamela Gay: Bye-Bye.
Dr. Pamela Gay: Astronomy Cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy Cast is released under a Creative Commons Attribution license. So, love it. Share it. And remix it. But please, credit it to our hosts: Fraser Cain and Dr Pamela Gay. You can get more information on today’s show topic on our website: astronomycast.com This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon.com/astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox, and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast.