Science Friday - Solar System Smackdown: Mars v. Venus, Mussel Mystery. Oct 9, 2020, Part 2

Episode Date: October 9, 2020

Solar System Smackdown: Mars Vs. Venus One of the fiercest hunts in the solar system is the scientific search for signs of extraterrestrial life—whether that’s in a methane ocean on Titan, under the icy crusts of Europa or Enceladus, in newly discovered subsurface salty lakes of Mars or, in the case of hypothetical long-dead fossils, in the rocks of ancient Martian river deltas. But just as the next Mars rover—equipped with life-sensing instruments of all kinds—is barreling toward the Red Planet for a February landing, comes news from another planet. A research team writing in Nature in September say they’ve found high concentrations of phosphine in the atmosphere of Venus. That much phosphine is not known to exist without help from bacteria—and researchers dating all the way back to Carl Sagan have suggested that the thick, acidic clouds of Venus would be a plausible place to harbor microscopic, extreme-loving life. Is this a good reason to send more missions to Venus? Or is Mars still the best candidate for investment of finite resources? Science Friday producers Katie Feather and Christie Taylor host this completely made-up argument about which planet is the best bet for finding life, with help from genetics and astrobiology researcher Jaime Cordova, and planetary scientist Briony Horgan. A Breakthrough In A Mollusk Mystery Freshwater mussels in the United States are having a bad time. It’s estimated that 70 percent of freshwater mussel species in North America are extinct or imperiled—a shocking number.  There’s a good chance you haven’t heard about this. Mussels aren’t the most engaging creatures, and they don’t pull at the heartstrings like easy anthropomorphised mammals. These mussels also aren’t the ones that wind up on a restaurant’s seafood platter. But mussels play an extremely important role in aquatic ecosystems, so scientists are doing their best to figure out what’s going on with their drastically declining populations.  Scientists recently discovered 17 viruses present in mussels in the Clinch River, a waterway in Tennessee and Virginia, where about 80,000 mussels have died since 2016. This is a huge breakthrough in a mystery that has plagued researchers for years—though it may just be one piece of evidence for a multi-dimensional decline. Joining Ira to talk about mussels in trouble are Jordan Richard, a fish and wildlife biologist for the U.S. Fish and Wildlife Service in Madison, Wisconsin, and Eric Leis, a parasitologist and fish biologist at the La Crosse Fish Health Center in La Crosse, Wisconsin. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Irafledo. A bit later in the hour, the mysterious case of the vanishing freshwater mussels, but first. You know, a little bit of healthy competition around the SciFri office is a good way to blow off some steam during these trying times and usually leads to some fun, nerdy arguments. Well, a few weeks ago, new research about two of our planetary neighbors got a few of our producers fired up. Katie Feather and Christy Taylor got together to hash things out in front of a live Zoom audience, and, well, let me just say there were no chairs thrown.

Thanks, Ira. Hey, Christy. Hey, Katie. Thanks for coming by all of our computers today. No problem. Thank you so much, everybody, for joining us via Zoom. Christy, you need to explain to the people here today why we're together in this segment today. Well, that's a great question, Katie. And it all started with a little bit of an argument, which is which planet should we, we personally, the staff of Science Friday, who get to travel to other planets, as you know.

Where should we go to look for life? Mars or Venus? Right. Because a couple of weeks ago, we got this news about phosphine being discovered in the atmosphere of Venus. And everybody in the office was like, oh, my gosh. And I got so excited about it. And then this news about salty lakes on Mars came out and people were like, oh yeah, Mars is still

around. People are still looking for signs of life there. Yeah. And as you know, I'm definitely on team Venus. I'm an underdog person. And I think it's really cool that this planet that's been more or less ignored by NASA for so long has had such a striking piece of evidence arise for something that we really can't explain, except possibly with the presence of a lot of little bacteria swimming around in the cloud, burping out this poisonous gas phosphine. Okay, but I'm just someone who doesn't really like a lot of excess hype around something that maybe doesn't deserve it. There's a reason why we started our search for life with the red planet. For one, it's much more Earth-like than Venus, which is basically a hellhole.

It's 698 degrees Kelvin on the surface. Two, there's a lot of very reasonable hope for living bacterial life on Mars in places like under the polar ice caps of Mars and in these new salty lakes. You know, I don't know that Earth really wanted to be a part of this argument, but since you're bringing Earth into this, You know that Venus and Earth are basically twins, right? Just slightly different, more hellish conditions. Venus is hot, it's high pressure now. But it's partly because Venus had this runaway greenhouse effect till the atmosphere is literally soup,

which I don't know if that sounds familiar these days or not. So what that tells me is that if we find life on Venus, we're also finding out something about a potential future that Earth could be dealing with and the kinds of life that may thrive in that future. Okay, here's my counterpoint to that. Since Mars is similar to ancient Earth, we can also observe what climate change is done to Earth by looking for signs of ancient life on Mars in rocks, which Mars has and Venus does not have. And you cannot understand your future, Christy, unless you look and understand your past.

You know, I'm hearing a lot of fear of the unknown. I'm hearing a lot of hesitancy about trying something new. And I don't think that's a good rationale for making decisions about scientific exploration. Aren't we supposed to dive into the unknown and be excited to discover things that we can't see or explain from here? It just feels too safe to be looking at Mars, honestly. It's not necessarily safe. It's just like I'm more of a completest. So I feel like we haven't completed the job of Mars and found everything that we need to find.

And in terms of, you know, scarce resources and manpower and time and things like that that NASA has, I feel like we just need to kind of wrap up our exploration of Mars before we move on to, you know, other more quixotic projects like exploring. Venus. Katie, it's not quixotic, though. You know, the European Space Agency has a craft that's flying by Venus in like a week. So we may even have more data without having to do anything new, you know, even sooner than we'll have anything from Mars, which, by the way, perseverance isn't even getting there until February. Okay. Well, I'm okay with, you know, the concept of, you know, the meme with the girlfriend and the boyfriend and the boyfriend's looking back at the other girl. I'm, like, really cool with sticking with Mars, like sticking with the one you know, and then the other

girl and that meme can be Venus and the dude's just kind of like looking back at it being like, hey, what's up back there? Just checking out the situation back there. But really, you know, sticking with Mars, you know, the one you know. Katie, are you calling me a distracted boyfriend? Yes, distracted boyfriend meme. That is what the situation is. What meme is your planet like, Christy? My plan is not like any meme, Katie. But if you want a pop culture reference, we do have Carl Sagan on our side. He was proposing back in 1967, more than 50 years ago, that we should be considering the clouds of Venus as a potential habitat for microbial life forms. And who are we, Katie, to disagree with Carl Sagan?

Well, there might be a reason why we didn't follow Carl Sagan's advice all the way back then. But I'm just saying it's unlikely we're going to be able to answer this question without pursuing both planets, which we're probably not going to be able to do with equal vigor and seriousness. So, you know, the question is, do we switch tax and learn more about the signs of life on Venus? Or do we stay the course and persevere? Get it, Christy? with Mars, and we're just going to have to imagine that NASA's out there listening to this debate because, you know, we don't actually control the funding over there or have anything to do with

their decision making, but we'll pretend that, you know, they care about what we have to say. I know NASA's listening in my heart and I'm sweating a little bit. Well, you don't need to sweat because the whole point of this conversation that we're having right now is that we need help from experts to help us make this decision because we're just science communicators. Yeah, that's true. So what I'm going to propose, Katie, is that we phone a friend and bring in some friends to help us out. Yeah, we've each brought a researcher to the discussion to help us argue our talking points in favor of our chosen planet. Joining me is Brian E Horgan. She's an associate

professor of planetary science at Purdue University. That's all the planets because she's an expert in all the planets. And yet, she's here with me to talk exclusively about how Mars is great and why we should be going there to look for life. All right, Brianie, nice to meet you. You seem pretty cool. I am going to bring in my friend, and his name is Jaime Cordova. He is a PhD student at the University of Wisconsin-Madison in genetics, but also astrobiology, and this will be important later. Stay tuned. He is also, as of 2019, a solar system ambassador for NASA's Jet Propulsion Laboratory. So that's an ambassador for the solar system. So I would say he is also pretty cool. Okay, welcome both of you to the show. Thanks for talking some smack with us.

Thanks for having us. Great. Thanks for having me. This is great. Okay, so Briani, we're going to start with you. This whole argument started because of new research about both these planets. So why don't you give us the case for Mars with regards to these salty lakes? Yeah.

Well, so on Mars, we have a lot of evidence that there might be liquid water that's stable at or near the surface of Mars today. And that new salty lake study is a great example because it's a new result showing that there might be ponds of liquid water under the South polar ice cap of Mars, which could be a habitable environment that life could live in today, which is really exciting. So how would we know, though, if, like, what would we need to kind of do to see if those habitats were conducive for life and if there was life actually there? We've got to go, right? That's the whole, we've got to go and explore.

So it would be awesome to go send a drill or something to the South Polar Cap. It'd be great to go look at some of the sediments and things that are coming off with the South Polar Cap to see if there's anything there. It's something we could definitely do with the kind of technology we have today. Okay, very good point, but I really want Jaime to step in into my corner in the Venus corner and talk more about this phosphine finding, which was pretty exciting, but maybe not well unpacked for everybody. So why is phosphine such an exciting possibility for Venus, especially when we're talking about the clouds? First, I'm going to clarify that the researchers

who published the phosphine study made really clear that the finding of phosphine does not necessarily equal the finding of life. So we haven't found life yet, that's for sure. But the reason why it's so interesting is because at least here on Earth, the only types of chemistry that we know of that can make phosphine is either we make it in the lab or some form of anaerobic bacteria. Even with anaerobic bacteria, we don't really understand the mechanism that they make phosphine.

That was really the reason why the phosphine detection was so exciting. It's possible that it could be life. It's also possible that it could be some form of unknown chemistry that we just don't understand. Now, the reason why it's so exciting is because the clouds are actually the area where we feel that life could exist there. And that's because the clouds, unlike the surface of Venus, which is really a lot like hell, clouds of Venus are a lot more comfortable, at least to some forms of life. See, I'm going to agree with you there. You know, the surface of Venus, a lot like hell.

You're not going to find any life there. But then there's also these clouds, which we can't see through. And that's one of the reasons why we chose Mars over choosing Venus to start our search many years ago and looking for life. So Brian, you help us understand the many times that we've gone to Mars. What have we, like, turned up so far there? That's really promising. Yeah, we've actually only gone to Mars once to look for modern existing life. And that was the Viking landers back in the 70s.

And since then, you know, we didn't see any obvious evidence for life because we kind of landed in a dry, dusty part of Mars that we now know, maybe it's in a really habitable environment. But since then, NASA has been taken this totally new approach to try to understand when and where life may have existed on ancient Mars. And the when is really important because as you mentioned before, you know, Mars, we think very long time ago, billions and billions of years ago, used to look a whole lot like Earth. At one point it's passed, it had rivers, lakes, maybe even oceans that could have been a habitable environment where life could have lived.

And so what NASA's been trying to do for the past 30 years is slowly build up a huge database of knowledge about, you know, okay, first, was there water on ancient Mars? Yeah, we know that. The Spirit Opportunity Rover showed us that water was present. Then, okay, were those environments habitable? We're not just, did they have water, but did they contain the building box, blocks of lights as well? And that's what the Curiosity rover has shown us over the last eight years on Mars. And now with the Perseverance Rover, now that we know that, in fact, there were these, you know, abundant, habitable environments all over ancient Mars, billions of years ago, we're actually going there to look for signs of ancient microbial life

in the rocks. And so that's really what the search for life on Mars today is really about is looking for signs of ancient life trapped in the rocks. So we're talking about ancient life. We've sent all these craft looking for ancient life. But I really want to take our attention back to modern life because that seems like where it's at. And in that case, Jaime, isn't Venus like overall a better candidate? Yeah. Venus is definitely a better overall candidate in that case. I mean, sure, Venus is hell-like, but I mean, at least it's not dead like Mars. So, I mean, sure, you've got the salty lakes, but, you know, are you really going to be able to access those salty lakes under those poles? And I think, you know, some of the other, there is some evidence.

There are some models that show that Venus likely had, you know, a continuous presence of water for two to three billion years, which is enough time for life to have arisen there. whereas opposed to Mars, as far as I understand, it really only has climate models only showed episodic times of water. That being said, yes, odds are that there is a better chance for existing life in the clouds of Venus because the conditions are still right there for some forms of extreme life that we know some examples here on Earth. We have to take a break now, but when we come back, the planetary smack talk continues with our guests. Brian E Horgan, Associate Professor of Planetary Science at Purdue University and Jaime Cordova, a PhD student. at the University of Wisconsin-Madison in genetics and a solar system ambassador for NASA's Jet Propulsion Laboratory in Pasadena, California. This is Science Friday. I'm Katie Feather.

And I'm Christy Taylor, continuing our debate over which planet has the best chances of turning up life, Mars or Venus. And joining me on Team Venus is Jaime Cordova. He is a PhD student at the University of Wisconsin-Madison in genetics and a solar system ambassador for NASA's Jet Propulsion Laboratory in Pasadena, California. And joining me on Team Mars is Brian E. Hogan. She's an associate professor of planetary science at Purdue University. And just to note, this segment is being recorded with a live Zoom audience, where Science Friday listeners can ask their own questions about Mars and Venus and help decide

the winner of this debate. Okay, so, hi, May, we were talking about ancient versus modern life earlier. But let's say I'm out shopping for planet with living organisms on it. what's going to be on that list of requirements for life? So you need a source of water, which Venus has some water vapor in the clouds that was detected in the, I believe in the 80s. And because of the sulfuric acid that is in the clouds, the sulfuric acid characteristic of it is that it's very hygroscopic. So basically it's able to water attaches to it, which means that, you know, there may be some extra water available that we're not necessarily aware of. You also need energy.

So, for example, a primary source of energy here on Earth is the sun, photosynthesis. There is enough energy that reaches the clouds of Venus that's been calculated to be roughly about the same or, if not a little bit more than the photosynthetic energy that reaches the surface of the Earth. And then the last thing that you need would be some certain elements that are really needed by life. So schnapps, carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. And some days you need a little more schnops than others. But so you not only do you need schnops, but also, you know, there are other elements that are necessary. For example, iron is another element that that's necessary for life. And we know that these six or seven elements are present.

They've been detected at least once in the clouds of Venus. We know somewhat about their abundance, but their actual bioavailability. So is it actually something that's available to life? We're not totally sure yet. But that's why we need to send more missions to Venus. All right. Well, Brian, we have some work to do in terms of tearing down this argument about Venus. So I need to ask you, do researchers really think that they will actually find life in the clouds of Venus? I mean, how promising does this phosphine research look to you? And then also, you know, we have perseverance coming up. And what kinds of evidence could perseverance turn up that would, if for those who are still, you know, team Venus might tip the scales and make them team Mars? Yeah, well, I'll say Venus is just, I think it's so fascinating, right? I'm definitely team Mars and Venus is really cool. I have to it, right?

I mean, Venus, I like to say it's literally shrouded industry. So, you know, the phosphate detection is, I think, incredibly important because it tells us that there are weird things going on on Venus. That would be really interesting to find out. Now, is it life, right? I think there was a recent paper that just came out suggesting it could actually be from volcanoes spitting out crazy gases on Venus. But on Mars, I think it's important to think about, okay, so we're postulating this one environment on Venus, right? the clouds of Venus. But on Mars, man, we have thousands of different unique environments that have persisted over billions of years from four billion years ago all the way till today.

Some of these we've actually shown were present and had water present for at least millions of years. The Curiosity rover has been driving through hundreds and hundreds of meters of stacks of ancient lake muds that were deposited in this long-lived massive lake that was almost 100 miles across. So we do know that there were these persistent environments on Mars that we know could have supported life because we found all those the schnops, the carbon hydrogen, oxygen, nitrogen, phosphorus, and organic materials in those muds. So Mars, in some way, you know, I think it is,

as far as these things go, which looking for life is very risky, right? But as far as these things go, Mars is a pretty safe bet. We know it has all the ingredients for life and the places where life could have lived. So perseverance is building on that, right? So perseverance is going to actually take these really amazing instruments that we're going to go look at the rocks at, you know, very high resolution,

signs of these ancient microbes trapped in the rocks. And so, you know, we're hoping to find things like organic molecules in layers and other kinds of shapes that would tell us that they were laid down by microbes. Like, for example, the kind of thing we would love to find is evidence of ancient microbial mats growing on the shores of a lake in Jesro Crater where we're exploring. That would be amazing. And the kinds of things we see from orbit and Jesro Crater where we're landing, we see evidence of this enormous delta that formed when this lake was present in the crater for a very

a long time. We see evidence of beach deposits where these microbes could have lived. And so we're hoping with perseverance will actually be able to see the details that will tell us that, yeah, life might have lived here. We have a listener question that I think is a good one for Jaime. First, we have a question from a listener, Sochi. Do we have any species on Earth that could help us understand possible cloud life forms? And then hold that thought because I also want Andrea Walker, had a question that sort of is related to that. My question was about, about the atmosphere of Venus having acid in it. Why is it that it couldn't be,

that couldn't be the basis of their kind of life as opposed to our kind of life here on Earth that is based on water? So that's a great question, and I do want to front that with Jaime, you told me that Venus has a negative pH when we're talking about the acidity of Venus. So this is some serious acid.

Yes, yeah, so the sulfuric acid, so there's a lot of sulfuric acid in the clouds. you're looking at a pH range of about negative 1.5 to 0.5. Admittedly, when I first started doing this venous work, I didn't know that there was a negative, that there was such a thing as a negative pH. So that was a surprise to me. Now, to answer Sotrude's question,

if there are terrestrial bacteria that could potentially survive, though these are called extremophiles. Extremophiles are bacteria that are able to survive in extreme environments. So for example, you've got thermophiles, which like really hot environments. In fact, some thermophiles, if you take them out of hot environments, they die. You have halo files, which love a very salty environment. And you also have some that really like acidic conditions.

You also have some that enjoy really basic conditions. So we definitely know of organisms here on Earth that have that capability. The issue is that for Venus, you'd have to have something that's known as a poly-extremial file. So that would be a bacteria that's able to withstand a more. multiple extreme conditions. Now, there is, there are a couple of candidate organisms that we consider may potentially be a good analog. One, for example, and I'm going to butcher the name, is Assypacillus ferroxidants. Basically, it's a very hardy extreme file that can live in low pHs and can also live in high temperatures. So that's one example. Now, to answer Andrew's question,

in terms of if there's so much sulfuric acid, is it possible if they could be using that? Yes. So, Well, the sulfuric acid tells us that there has to be sulfur in there somehow, right? And there are sulfur species there in the clouds. We do know that there are some metabolisms here on Earth that some extremophiles use, that use sulfur and different sulfur species to produce their energy. So I mentioned earlier photosynthesis is one way of producing energy. There's also something that's called chemosynthesis, which is essentially not necessarily using light, but using different chemical elements to gain their energy.

And this is something we see in the hydrothermal events at the bottom of the ocean because no sunlight reaches. I still feel that signs of ancient life on Mars are pretty fascinating and do qualify as like good evidence and a reason why we want to be in Mars. But let's just say for the sake of argument that we are talking about, you know, signs of modern life. There is something that Mars has that's equivalent to phosphine on Venus. And one of our watchers or listeners right now, David Rossiter, has a question about that. Hey, everybody. Yeah, we've for several years now had evidence of methane on Mars.

And I understand that also could be an indication of life as well as a geological cause as well. Can you all comment on that, please? And I'm going to throw that one to Brini first because she's our Mars teammate. So, Brianie, what about this methane on Mars? could that be also a sign of modern life on Mars? Yeah, it could. The reason why it's exciting to detect methane on Mars is because it's not stable in the Martian atmosphere of a long time periods.

Radiation and things will actually break it down, and it's not stable over scales. We think of like 10,000 years. So the fact that we see methane today means it's being produced by something. So the big question is, what is that something? It could be interactions between water at relatively high temperatures and rocks underground producing the methane, or it could actually be life living probably as well underground. Either way, that tells us that there's a potential habitable environment underground in the crust of

Mars. That's another place we've thought about looking for modern life on Mars, not just in these salty waters at the surface, but also in these probably cozy, warm environments underground. And so the methane might be telling us about those deeper environments on Mars. Well, Christy, I know that we're going to go to the question about how do we investigate these two planets? next. And I think this is where Venus is rather weak, and Mars is pretty strong in this case. So we have yet another listener, Vladimir Pittman, who has a question about that. Hello. Thank you. About investigating Mars, I'm just wondering, like I said, the capability of sending a probe there that would last long enough to provide samples if we'd be able to return with samples

or it would be something that just collects evidence from the cloud. Do we have the capability to actually get to the surface and keep a probe there long enough to collect samples. Sorry, so you meant Venus. Venus, yes, Venus. Yeah, and Jaime, I know, like, I have this theory in my head. Like, we can, like, maybe at least, like, send a big ladle past the clouds of Venus or something like that to, like, scoop up cloud stuff, as they say. But I think you had a better vision for how this would actually work.

Yeah, so I'm going to backtrack real quick and say that there actually has been nothing that's been detected at least once. on Venus. Whether it's a sure result, we're not totally sure, but there has been nothing that's been detected in the clouds of Venus. I'm just gonna throw that out there. But to answer the question, yes, we can investigate,

so we can investigate Venus in the sense that, basically it's, I believe it's called Hot Tech if I'm remembering correctly, but basically what it is, it's this technology that's able to, or new batteries, new systems that are able to last for a lot longer. Now, and that's for the surface, in terms of the clouds, What would be really cool is if we have balloons, for example, or aerobots, which is sort of like a drone in a sense.

There are some proposals for doing this. In fact, the Russians already did that with the Vega balloons in the, I believe in the 80s. So this is known to be done. That would be ideal, at least in the sense of habitability, or coming from a habitability standpoint, I'll leave the geologist to want to do the surface. But I mean, it's still important to understand the geology because that tells us a little bit about the ancient climate of Venus. But at least for the atmosphere, it would be cool if we can, you know, collect samples from the aerosol samples from the clouds. And not only do that once, but also do it on its very temporal and spatial resolution.

So at different latitudes and different times of the Venusian Day. So that would be ideal. And yes, we can do that. Just as a reminder, this is Science Friday. I'm Katie Feather. And I'm Christy Taylor. Talking to planetary Smackdown specialists, Jaime Cordova, and Brian E. Hogan about which planet is best to look for life. All right. I feel like I've heard enough, Katie. What about you?

Yes, but I want to make some final arguments in favor of Mars. In one case, we definitely have ancient life on Mars. In another case, we could have even modern life on Mars. We've been investigating Mars for longer, and we know how to get there pretty easily. We've sent a lot of things there to investigate. We could even send humans there possibly in the future. And we have perseverance on the way. So in terms of when you measure, you know, the potential evidence that we might find with, you know, and I very heavily weigh this, the feasibility of all this of getting there and looking for this life on Mars,

I think Mars should be the winner in this case. I rest my case. Well, I wasn't prepared to summarize my thoughts. So I'm just going to tell you what I like about Venus, which is that it's been neglected. NASA actually even has drafted what a mission to Venus could look like. They just didn't go forward from the proof of concept. So the research is already out there, and we just need to stop doing this whole sunk cost fallacy situation and get excited about something that could really redefine how we understand life to be. I mean, and I think, Jaime, you would make the point that we don't even understand like 1% of the bacterial life on Earth.

I mean, we don't, we don't understand 99% or at least some estimates say that we don't understand 99% of bacteria on Earth. So just because we haven't found something that is absolutely exactly like something that could live in the clouds of Venus, doesn't necessarily mean that we, doesn't mean that it doesn't exist. All right. And Brian, I'll give you the last word for team Mars. Finish Strong. Well, I got to say Mars. So we're really excited about not just understanding.

whether or not there was life on Mars, but what can that tell us about the origin and evolution of life on Earth, too? And I think that is so incredibly powerful to be able to study a planet where you can not just understand, is there life there today or was it in the past, but how does it relate back to how we came to be, which I think is really, really cool. I think we have had some really great arguments on both sides. And we did pitch this as something where our listeners get to decide who the winner is. So hopefully everyone can see the poll that is up on their screen right now. Again, And this is a you decide situation. You heard the arguments from both sides. You had a chance to ask some questions. There is a representative from NASA and a trench coat in this audience. So now is the time to vote. And don't just like listen to Christy's sympathy plea for Venus, how it's the underdog planet. Think about all the time that we've invested in Mars. We should just stick with our current girlfriend instead of looking behind us at the girl that's passing us on the street. My last point to that, Katie, is that you know that in that meme, the wrong girl is wearing the red dress. And what is a red planet? It is Mars. So if we're going to go with

meme language here, I finally have a good rebuttal for that. Okay, the voting is done and our sci-fri colleague Diana is here to announce the results. And the winner of the poll is Mars. Oh, my very slight margin. Congratulations, Team Mars. Well, thanks everyone for listening so closely. Hi, I'm going to ask you to say something nice about the other team, since you are the polite loser in this situation. All right. It's okay.

I mean, unfortunately, Venus is used to being ignored. But I will say, I will say that regardless of Venus didn't win, Mars is still a really cool astrobiology target. Venus is a really awesome astrobiology target that I think we should investigate further. but I think it really in, you know, in understanding any sort of planetary body is really useful for astrobiology.

And Brianie, can you believe we did it? We pulled Mars to the finish line. We got a winner on our hands. But what would you like to say about Venus? Well, I really am a Venus fan. I think Venus is a fascinating planet. And I really hope we get to send new missions there to try to understand what it used to be. I mean, Venus, we really have no idea what its history was.

It could have been totally Earth-like a few billion years ago. and what happened? You know, something really dramatic happened to Venus to change it. And, you know, what does that mean for the history of life? And so I am extremely excited for what I hope are all the new missions, NASA will send to Venus in the next decade. Thanks so much to our planetary experts for playing with us today. Thanks for having me. Thanks for having me. This is great. Brian E Horgan is an associate professor of planetary science at Purdue University. And Jaime Cordova is a PhD student at the University of Wisconsin-Madison, studying genetics, and a solar system ambassador for NASA's Jet Propulsion Laboratory in Pasadena, California. For Science Friday, I'm Katie Feather.

And I'm Christy Taylor. Thanks, Katie and Christy. And you can watch the entire video of this Smackdown and sign up to find out about sitting in on a future Zoom interview on our website at sciencefriety.com slash events. We're going to take a break. And when we come back, we'll put on our detective hats and dive into a mollusk mystery.

Scientists trying to figure out why freshwater muscles are dying at apocalyptic rates. Coming up after this short break, stay with us. This is Science Friday. I'm Iroflato. And now it's time to dive in to a mollusk mystery. Freshwater muscles in the U.S. are having a really bad time. It's estimated that 70% of freshwater muscle speech, she's in North America are extinct or imperiled. That is a shocking number.

There's a good chance you haven't heard about this. Muscles aren't the most engaging of creatures, right? They don't pull at the heartstrings like a fuzzy little mammal might, and these are not these saltwater muscles that arrive on your seafood plate. But muscles play an important role in aquatic ecosystems. So that's why scientists are doing their best to figure out what the heck is going on here. and why their declines are so drastic. And now scientists have a lead to this great mystery.

Joining me today to talk about these muscles in trouble are my guest, Jordan Richard, a Fish and Wildlife Biologist for the U.S. Fish and Wildlife Service in Madison, Wisconsin. He's also a Ph.D. student at the University of Wisconsin. And Eric Lees, a parasitologist and fish biologist at the La Crosse Fish Health Center in La Crosse, Wisconsin. Welcome both of you to Science Friday. Hi. Hey, glad to be here. Jordan, when did it become apparent that freshwater mussels were having a bad time?

Well, it's been apparent for well over the last hundred years. They've really had a whole series of issues. It started with pollution and the Industrial Revolution, and then river impoundment. Then they faced pearl culture harvest where people would just harvest them by the thousands just to see if they had a pearl in them. And then before plastics became big, mussels were actually the number one source for shirt and clothing buttons so people would harvest their shells just to punch out little circles for using buttons. So they already had their own huge share of issues. But then more recently, we've

started noticed what we call these mass mortality events or die-offs. And it's really been kind of a mystery. More recently, in the Clinch River in Virginia and Tennessee, we saw this seasonal mass mortality that started back in 2016. And the clinch is kind of the crown jewel of aqua biodiversity in the southeast. There's 133 species of fish and 46 extant species of mussels in the Klins River in its tributaries alone. So it's really worrying to see mass mortality in one of these biodiversity hotspots. Are we talking about a specific kind of muscle that's dying off in that river, or are they overall not doing well? The ones we're seeing die in the big numbers are actually one of the most common species. So it's not one of the 20,

federally endangered species that lives here, but it's the common one that we've kind of counted as our bedrock of the muscle community. They're always around. They're always abundant. And they're always providing those critical ecosystem services that muscles give us. So it's really worrying to see a big proportion of the total number of muscles dying when you lose a species like this. Yeah, to have a die-off in the most common species, you're going to be losing the greatest number of muscles. Exactly. They're also one of the largest of muscles come in all shapes and sizes. When you lose 80% or more of the pheasant shell biomass, that's the specific muscle we're talking about, you're actually losing a quarter or a half or even more of the total

muscle biomass in a given stretch of the river. You know, I mentioned at the top that these are not the muscles, the saltwater muscles that people eat. Give us a crash course and why these freshwater mussels are important for the environment. So I always start with the analogy of a healthy function ecosystem is like a house. And in that analogy, muscles are the foundation. So they play these critical roles as ecosystem engineers where they're filter feeders. And so they live down in the bottom of the river where a lot of the biomass, the river is concentrated. So you picture classically fish are swimming around in the water.

But a lot of the things that live in the river, snails, crayfish, muscles, and macron vertebrates and all the things that fuel the food chain, they all live down in the bottom between the rocks. And so what muscles do is they filter everything that's flowing down the river in the overlying water column, and they take it in and they filter it. The water gets decontaminated. They have really great properties for detoxifying a lot of compounds for people and other animals. So they're cleaning the water, but they're also taking in nutrients and sources of organic carbon, processing them, and then depositing them down in the sediment where all these other creatures live. So they're simultaneously cleaning the water and then fueling the bottom of the food chain in the river. And then when they die, their shells persist for decades, and they make really great habitats.

They add a lot of complexity. If you go out on a shoal and you start picking up shells, you very quickly find a lot of little fish and crayfish and snails and other small muscles. All sorts of things depend on those nooks and crannies that you get when you have a healthy muscle ecosystem on the shoals. Let me go to the mystery of why freshwater muscles are declining, and you have a lead, right? possibly a virus or viruses? Is that right? We do. After a lot of hard work by a lot of people, we really clamped down and put on our epidemiology hats to investigate this thing because it's really tricky to figure out what's going on. Do you need to look at all the species? Is it just this one that seems disproportionately affected? And so what we've found now is a novel virus that's

tentatively named Clenched Tensovirus I. And it is strongly associated with the mortality, which means that in our sampling over time, we've collected sort of a case control design where we have healthy muscles and then muscles that are dying from these sites and other sites scattered around the watershed. And we do all sorts of next generation sequencing and build out virus genomes of novel viruses

that have never been seen before and then use our statistical tools to see which ones are the most associated. And so we described 17 new viruses and freshwater mussels from the sampling, but one of them was, 11 times more likely to be found in sick muscles compared to healthy muscles, and orders of magnitude, higher viral loads were found in the sick muscles. So it's a really strong association

at this point. Eric, do you have any idea why the viruses are attacking now? What is happening in the environment? It's difficult to say what's happening now. From the sick muscles, we observed less bacterial diversity, and we saw species that were commonly secondary, pathogens. So they're known to infect other animals, including fish, later after there's already a primary infection established. And we also found a bacteria that was associated with contaminated soils and had the ability to degrade hydrocarbons. So we're not sure if there is some sort of contaminant persisting there and this bacterial species is some sort of biological indicator. But it would be possible that there are changing conditions or possibly things in the environment

that would allow for this virus to kind of gain a hold and cause disease, but that's something that will continue investigating. Tell me about how you would do this sleuthing on this. Which part of the muscle are you actually looking at when you try to figure out if it has a virus? Is it blood? Does a muscle have blood? Where do you look for it? So the muscle does have blood, and it's called hemolymph.

So they have an open circulatory system, so it's not a closed circulatory system like you see in humans. And we basically take the blood or the hemolimp from the adductor muscle. So we crack the shell open slightly, and we use a needle and a syringe to slowly draw the blood out. And it looks sort of watery, but you can see these little particles in it. And the hemocytes are basically their blood cells. You can kind of see them in the hemon solution. Why has it taken so long to crack through this mystery of why freshwater muscles are doing poorly?

Well, part of the reason is that we've kind of needed a technology like Next Generation Sequencing. And so Next Generation sequencing has been used in human medicine, and we kind of needed that to trickle down to applications in fish and wildlife health, where we could have a tool where we could see all the viruses that could be present in a sample. And so that's really been the foundation of our analysis. Another part of it has been that there hasn't been a cell line established from freshwater mussels that we can use to try to isolate these viruses. So from a fish population, if we think a virus is infecting fish, we can take tissue from those fish and homogenize it and dilute it and put it on the fish cells that we have growing in the lab in plastic flas. And so if the virus was in that population of fish, it would hopefully

infect those cells, and we can observe that. And it's called cytopathic effect, where the virus is basically infecting the cells and lysium. And so once we have that, we know that we have a highly concentrated, more purified form of the virus that we can use for downstream applications like molecular analysis, electron microscopy, or even in vivo trials, where we take that virus and expose otherwise healthy fish to the virus to see if it is indeed pathogenic. And that's something that we haven't had with freshwater muscles. And so we've been, it's really more of a guessing game for us. We've been trying to isolate the virus through using the hemolent samples that we have, where we know the dental virus is present,

and we put that sample onto either fish cells or mosquito cells in an effort to get that virus to replicate. So you've really had no muscle memory to work from this? That's for sure. Jordan, we're talking so much about viruses these days. Do you think that this is a relatively good time for this news about muscles to come out? Yeah, I think it's really made communicating what we've been finding and working on a whole lot easier because everyone sort of had this forced primer on virology 101 and not just

the basics of viruses, but sort of how a viral infection unfolds. I was sort of thinking about it earlier when you were asking about why are we just seeing this now and why might this be happening? It's it's part science and part philosophical question. You know, like, why is COVID happening right now? It's a whole series of factors, but it's been so much easier to talk about what we're finding and the intricacies of it because everyone knows a lot more about virology than they did 12 months ago, especially things like comorbidities and the fact that, you know, in a population, the mortality isn't going to be 100%. There are very few viruses like Ebola where the mortality rate is close to 100%.

It's going to be viruses but also bacteria and underlying health. And that all ties back into sort of the river ecosystem. Is the river healthy already? My healthy muscles in a clean river be able to fight all viral infection better than those in a polluted river. Those kind of details could be really hard to talk about, especially since no one's really talked about freshwater muscle viruses before. But everyone has this nice parallel that the entire world's staring at as we talk about it.

I want to pick up on that last point that you just made, because it's interesting. There are some creatures that go through massive die-offs that people have really strong emotional reactions to, like polar bears or orangutans, for example. And muscles aren't exactly the cuddly, easily anthropomorphized kinds of animals. How do you get people to care, Jordan, about muscles? It starts with just making sure that people know muscles exist. They're such cryptic little creatures. Most of the time, when you're seeing muscles in a river, what you're actually seeing

are those shells of muscles that have already died and have remained in the ecosystem and serve as nice nooks and crannies for other things. But all the live muscles dig themselves down the bottom of the river. And so we have muscles the size of salad plates where they're buried so deeply in the river that you might only see a quarter of an inch of them sticking up out of the bottom of the river. And so it starts to just explain that they exist. then getting into all the really cool ecosystem services they provide. I mean, they truly make

the world a better place for people and all other animals around them, like cleaning water, processing nutrients, stabilizing riverbeds. They're just so important. It's kind of like the foundation of your house. You got to have it. Yeah, that's very interesting point. Let me remind our listeners that I'm Ira Flato, and this is Science Friday from WNYC Studios. In case you're just joining us. We're talking about a muscle mystery, the die-off of freshwater mussels. We think it might be a virus of some kind, talking with Jordan Richard, Fish and Wildlife Biologist for the U.S. Fish and Wildlife Service, and Eric Lees, parasitologist and fish biologist at the La Crosse Fish Health Center in La Crosse, Jordan, Richard is in Madison. If we eat muscles that come from saltwater, marine muscles,

Why are we not eating muscles these freshwater muscles if they're the size of a dinner plate? Well, for one thing, a lot of these freshwater mussels are very long lived, some of them up to 100 years. And so for the same reason that they're useful to us, we also don't want to eat them. They clean that water by bioaccumulating the toxins and things that are passing by in the river water. And so if you're eating a large old freshwater muscle, one, it's going to be really rubbery, tough, and not taste very good. And two, you're going to pick up every contaminant that mussels ever drank in for the last 80 years. Aren't the saltwater muscles eating the same sort of toxic and cleaning the saltwater environments? They are to a certain extent, but the freshwater muscles are more directly exposed to all of the runoff that we have.

There's a famous quote, and I hope I'll get it right, but they say that rivers are the gutters down which run the ruins of continents. And so another way of putting it is that rivers are like the veins of the entire life on a continent and muscles are frequently known as the livers of the rivers. So just like sometimes we avoid eating liver because, you know, it's a toxin processing center. You want to avoid those muscles. I love it. The livers of the rivers. You know, that's how you can tell people about how much trouble the muscles are in by coming up

with a phrase like that. Yeah. To be fair, I did not come up. up with that one, but I really love to use it. It's probably my snappiest one liner for why everyone should love muscles. And it's a good one. Eric, do you have a hope that we can reverse the course of how poorly muscles are faring right now? Maybe we should use that phrase a little more often. Definitely. We're hoping to develop diagnostic acids. We're working on it right now that'll be used to find healthy populations of muscles that we can then target for use in repopulation and

restoration efforts. And what do we still not know about? muscles, Jordan, that would really help crack this mystery about the disease that's killing them. So many things. But to really get to the heart of the disease matters, we really need some measures of basic freshwater muscle health. It's something that you take for granted in human health, and we even have things like fish health, where we can take a blood sample and we can run it through analyzers, and we know what the parameters should look like. And people, everyone knows that 98.6 is the right temperature. And if you're above or below that, there's something wrong. We don't have any sort of numbers like that for muscles. We can't easily take their temperature,

so to speak. And so another piece of what we're working on is these metabolic assays to figure out how can we quickly and effectively measure whether a given muscle or a population is doing well, is struggling, is facing some sort of health issue. It's a real black box that we're all untangling at once as we dig into these viral mysteries. Eric, same question to you. What would you like to know that would really help to crack open this mystery? I think the distribution of the virus and just the other viruses that could be present in the environment as well.

Once we find out the viruses and other diseases that are important in muscle health, then we can work to not only limit their spread, but again, select healthy populations that can be used to restore the impacted populations. That's quite interesting. That's about all the time we have for today. I think we all learned a lot about freshwater mussels, the liver of the river. Jordan Richard, a fish and wildlife biologist for the U.S. Fish and Wildlife Service in Madison. He's also a PhD student at the University of Wisconsin. Eric Lees, a parasitologist and fish biologist at the LaCross Fish Health Center in LaCross, Wisconsin. Thank you both for taking time to be with us today. Thank you, Ira. Thank you. You're welcome. Oh, this week on the Science Friday Vox Pop app, we want to know if your dreams have changed since the start of the COVID-19 pandemic. We want to hear about it on the Science Friday Voxpop app wherever you get your apps.

Have a great, safe weekend. I'm Ira Flato.