Watermands, lost piglets, tartar grades. They go by many names, but I think the one thing we can all agree on is that they're pretty much indestructible, right. I mean, these poor teeny tiny creatures have been exposed to all manner of unpleasant stimuli in the lab. They've been frozen to near absolute zero, heat it up to way past boiling, irradiated, squeezed at pressures you'd experience one hundred and eighty kilometers below earths surface, exposed to the vacuum of space, and
shot into sand bands. If tartar grades ever become large and sentient and start looking for retribution, we are in a lot of trouble. But the good news for tartar grades is that they survive most of these experiences surprisingly well. How do they do it well? That's what we're going to discuss today, and by the end of the episode we'll answer a question that has no doubt kept you up at night. Are those tartar grades that crash landed on the Moon in twenty nineteen still alive? Let's find out.
Welcome to Daniel and Kelly's Extraordinary Universe.
Hi, I'm Daniel, I'm a particle physicist, and I don't like a lot of biology, but I do like hearing about critters that only poop when they molt.
Wait wait, wait, we'll back up that. I'm Kelly Wiersmith, a biologist. Did you just say that you don't like a lot of biology?
You know, there's a reason I'm in physics. The biology is all weird and messy. I mean, it's wonderful and fascinating, but sometimes I just feel like there aren't really any hard answers.
Well, well, you guys haven't reconciled quantum mechanics or general relativity yet, how dare you?
But there is a hard answer. We don't have it yet, but I think one day eventually humans or some clever aliens will figure it out. Biology, I just don't even know if there's an answer.
I mean, I can't argue with that. I'm not sure there's an answer for a lot of this stuff either, But I still think that's exciting. And also, I will note that you said that they only poop when they mold. There are probably more than thirteen hundred species of tartar grades. I don't know that it's true that all of them only poop when they vote. I think some of them might just poop like the rest of us.
All right, well, I'm fascinated. I want to hear more about it, because I'm sure there's an answer to at least this question of when do tartar grades poop.
I mean, it's going to depend on the species. But yes, all right, so we had an amazing listener question. Let's go ahead and listen to that.
Now, Hey, Daniel and Kelly, question about tartar grades. Those little water bears. Just curious what is it about them that allows them to survive in basically any environment. I've heard that there's even some on the Moon. As far as I know, NASA has an engineered little spacesuits that small. So yeah, just curious what is it about their physiology that allows them to survive?
Thanks?
Also, go Virginia.
Okay, so first off, I laughed out loud imagining NASA engineering tiny spacesuits for the tartar grades. That was amazing. Thank you for this question, and go Virginia. Woooo.
I'm sorry this question is disqualified. I mean, obviously they have no credibility from the.
Get go, Daniel, I did ten hours of research for this episode. We are not dropping this episode.
And did you discover that you have to be a tartar grade to enjoy the climate of Virginia.
Everybody enjoys the climate of Virginia. Tim and I agree on that. At least. There was a little bit of snow falling the other day and I felt highly festive. And I know that there are some places of California that have snow, but only some.
Well, you know, tartar grades can live on the Moon, they can live deep underwater, they can survive when it's dry, they can even survive Virginia winter.
Well, hold on, can they live on the moon?
I don't know.
That's the whole point of this episode, trying to find the answer to that question. So should we dig in, Yes.
Kelly, tell us what are these tartar grades, what do they look like, where do they stand in the context of all biology, and what do we know about where they can actually survive?
Okay, all right, well, so it'll take me an hour or so to give you that answer. But let's start with reiterating that there are probably more than thirteen hundred species. In fact, it's under Kingdom Animalia. There's something like thirty phylum and tartar grade they're their own phylum whoam and so there's a lot of them, right, But usually you're like, tartar grades do blah blah blah, as though there's just one species, but there's a lot more than just one species.
And the fact that they're so high up in this tree of life. I mean, it's not just like bile'll just like to organize things because they don't really understand them. It tells us something about.
Like wait, wait, wait, let's listen to the particles episode and you're like, I don't know how we categorize these things, so anyway, little hypocritical.
But no, seriously, I think when particle physics is feeling is when it's just doing taxonomy. If we're just doing botany, then we don't really understand anything. It's when we're doing philosophy, when we're linking things together, we understand how they work underneath. That's when I think we're really making progress. But what I want to ask you.
I think we need both. We'll move on.
But what I want to ask you is how we should interpret where people have put tartar grades in this tree of life. The fact that they're so high up, does that mean that they're really their own kind of thing. They're so different from everything else, or they have their own weird history or both.
Let's go with both, and let's talk about why they're so unique awesome. All right, So, first of all, these are tiny little guys. They're multi cellular. They got lots of cells. Big ones are about a millimeter long, so about the size of a period. They have this hard outer cuticle, and because it's hard, that doesn't grow with them, so they have to molt the way like nematodes, and some insects will mold the way snakes shed. Because snakes
are awesome. What's get snakes in there? You probably don't even like snakes, do you, Daniel?
You probably don't like like that's an outrageous thing, like, oh yeah, snakes, rats and cockroaches. You don't like any of that, doa Daniel?
Do you not like those things? Daniel?
Well, I mean I wouldn't want to like snuggle up with them. You know. It's not like if I see a bunch of the my bed, I go ooh cozy. You know. They're not in the same category as like kittens and bunnies for sure.
All Right, all right, I won't disagree with that, but I have seen some snugly rats. But anyway, okay, heart outer cuticles. Sometimes when they lose that cuticle, that is when they release the contents of their bowels that they've
been holding onto for a while. That's also sometimes they'll release their eggs into that cuticle when they mold, and then the eggs sort of have this like protective little case that they're in for a while, and then when they hatch, they have to find like the holes in the cuticle to get back out.
All right, So these things are really small. You're saying a millimeter is the biggest one. Can I see something with my naked eye that's just a millimeter? So like tartar greates, you could actually, like if you squint see one of these things.
So it's about the size of like a period on a printed out sheet of paper, and so like you know, maybe you could see some like flailing limbs, but like if you had a dissecting scope you could see them better. But again, a millimeter is about the size of like some of the bigger ones, and so a lot of them are even smaller, and so you'd be better off with like a compound microscope.
And does everything that has this hard out or shell have to molt when it grows? Or are there some critters out there that can like gradually expand, Because like our skeleton gradually expands as we grow, why can't you gradually expand your exoskeleton as you grow? Or is that a totally naive biology question.
Our skeletons are inside of us, and so they can like expand as our squishy outer parts sort of like accommodying that. But I think that if you have a particular kind of cuticle that's like super hard that doesn't tend to grow and expand, I think you do usually need to lose those all right?
And so do all of these things look roughly the same even though some of them are a little bigger and some of them are smaller. Do they all roughly look like the same critter? Like an individual non trained biologist tell them apart by eye?
They do have some definite characteristics that help you tell them apart. So my question for you is, I think when most people think of tartar grades, there is an animated video that they saw. Is something coming to mind for you? Or have you not seen this video?
No? I definitely have a mental image of a tartar grade. I think the phrase water bear has also influenced me. So I'm imagining something that looks a little like a fat caterpillar, but with sort of claws and then a weird face with like a tube sticking out the front of it. So it's a little like a possum or something. I'm not sure exactly animal. It looks like maybe like a microscopic water possum.
Oh, I love possums. Okay, So there's this like famous video where they're pink and they've got that like almost a toilet paper roll on top of their face, and it kind of like goes into the face and out of the face over and over again as the tartar grades eight little legs furiously have it swimmed through this water. So I was listening to ologies and Allie Ward was interviewing doctor Paul Bartel's and he was lamenting that that is like not what they look like at all, what.
Popular science has led us astray.
Kelly, really, hold on, I know, I know, it's amazing. Okay, So first of all, that toilet paper roll, nos thing does not go out and in and out and in and out and in That was a mistake because someone took a special kind of microscopic picture. They used a scanning electron microscope, and the way the sample was prepared, one of the tartar grades had that thing sticking out like it usually does, and one of them, because of how it was prepared, it just kind of got like
sucked into the face. But I don't think that usually happens, and so the nose thing isn't going in and out and in and out and in and out. I think someone just saw both of those photos and were like, oh, it must alternate between these two states as opposed to like the preparation process just kind of messes up specimens sometimes.
Wow, it's like they saw two frames and just animated the interstitial. That's crazy.
And then the other thing is they don't swim. They are what's called benthic, so they walk around on like the floor of things, or like they crawl up vegetation, but they're not swimming. They're crawling along. And that video that most of us are, you know perhaps right now. It has eight legs that are all like in front
of it. It's like a bear, but all of its legs have been multiplied by two but what really happens is it has six legs and like the usual configuration, and then another two that go like straight out from.
Its butt butt legs.
Butt legs, Yeah, how can we get So those butt legs hold on to stuff so that they like don't get washed away with the current or something. And some have claws and some don't have claws, and they're not usually pink. A lot of them are clear or white, or if they've got color, a lot of times it's because they are clear, but you can see like the algae they ate, so they look green, or you can see their poop so they look brown. And so some of them do have some colors, but they're not even
though they're moss piglets, they're not pink. Hmm.
I see so clear, like they're invisible, like you can see through them. They're like transparent.
If they are starved, some of them probably are transparent. But if they've eaten anything, you can see their digestive tract because they've got like green in it.
Wow, that's crazy. So like little tartar gray children when they've been sneaking cookies from the cookie jar, it's not a question the parents are like I see.
That cookie exactly. Yes.
Wow, what's the evolutionary advantage to being transparent? Is it like a form of camouflage or is it just totally incidental?
Everyone don't know. My first guess would be that it does help with camouflage if like a predator just kind of sees through you. But then the other thing is that, like creating pigmentation, is often a process that requires some energy, and so maybe being clear is just easier than creating pigmentation. But if you're in an aquatic environment, probably being clear is a good way to hide and blend into stuff.
Wow. All right, so we have totally the wrong mental image of a tartar grade, but it is still kind of cute. Yeah, and it does have those fat little legs and a toilet paper snout. But we're setting the record straight here today.
Well, they don't all have the toilet paper snout. Again. There's over thirteen hundred species. Some of them look like you little salamanders, but instead of a tail, they've got like, you know, the two butt legs. There's some variability in how they look, but they do have that. Like general, there's also tons of variability and where you find them. Some are in lakes, some are in oceans, and some are living in like when there's a little bit of water on lichens or moss, they live in that like
little water film. And there's some that you find in like roof gutters. They're essentially anywhere where there is enough water to keep them from like desiccating, or are there in environments that dry out sometimes and then water comes back, and this is what they're so well known for. They have a bunch of different strategies for surviving that dry out period.
If you find them in large bodies of water. How come you never find like mega tartar grades, you know, like there are sharks and then there used to be like huge sharks. Was there ever a tartar grade that was like a meter long or like a one hundred meter long or is that the next Michael Bay movie we're looking forward to.
There have been I believe a couple fossil tartar grades that have been found, and I don't think we've ever found a mega big one. So yeah, pass that idea onto Michael Bay. I think it's a winner because there are some that are carnivores and include there are some that will eat other TURTI grades, So I think that would make a great movie.
Exactly. You thought they were cute and fuzzy until you saw the big one come for you. Okay, but what limits them from growing? Like why aren't there bigger ones? Is there something about their geometry which doesn't scale up? Or is an ecological thing like they can't eat enough food to get that big? Or is there something which will eat them if they get too big? Or do we not know?
I don't think we know. Amazing, amazing that we don't know.
Amazing how many things biologists don't understand.
I feel like that's a theme of the physics talks. But all right, fair, fair, all right, okay man, it's a battle between California and Virginia and physics and biology today. I appreciate when you and I are both anti chemistry and we're on the same team, but because today we're doing battle, all right, So let's start with their abilities to survive desiccation, which means like drying out.
So this is something you hear about a lot in popular science. Are you going to ruin this for us also? Or is this something they really can do?
They really can, well, not all of them, So again, many many species the ones that tend to live in like mosses and lichens and roof gutters, like places that are wet sometimes but dry other times. They're able to form this stage known as a ton state, where they essentially it's like almost go dormant. Some of them describe it as like it's near death. So they're able to
like go into this like super resistant form. And when they're in this super resistant form, this is when scientists have done all manner of horrible things to them, like dip them in liquid nitrogen, shoot them out of guns just to see like how much can they handle when they're in this state.
So this is what they're famous for. When it's not like a nice and cozy and damp time to be a Tarta grade, you like convert into this like weird long lasting state where you're basically immortal, and then you can just like unfurl and be a Tarta grade again later it's like time traveling to the future.
So immortal, no, when they go into this state, they can survive for like years, maybe decades. But so one thing you might have heard is they can stay in this stage for hun ndreds of years. Actually that seems to be possibly a misreading of a study. So there was like a museum specimen where we knew when it was collected, and one hundred years later it got taken out of like some drawer and they found some tartar grades and they added some water, and it looked like
part of an arm kind of moved a little. This was written in Italians, either Italian or French in some Romance language, and so it was like an arm moved a little, but then nothing else.
Well, you know, in Italian hand gestures are super duper important, So maybe that was interpreted as communication, you know, that's right.
It could be. As a biologist, I've had to look at a lot of specimens where like, oops, the ethanol dried out, and now this animal's totally dried, and I'm going to try to like get it back in its normal shape by adding like water or more ethanol. And when that happens, they often like move in response to the rehydrating And it's not that they're alive, that's just the molecules responding to the presence of water. And if it did do a like hello, guys, hand gesture, it
died right afterwards. Maybe it's impressive, but probably it's just an artifact of it, like rehydrating.
That could you poured water on a dried up belief, it would change its shape also, and you might interpret that its motion, but it's definitely not alive.
Yes, exactly, and so that's a possible scenario. But there has been a specimen collected from Antarctica where it was two Tarta grades that had entered this dormant state and an egg that hadn't hatched yet, and the specimen was put in cold storage at life think negative twenty for thirty years and then removed and they came out of
their ton state, became adults. One of them croaked, but the egg hatched, and then the two individuals who were still alive went on to like reproduce I think more than once even, and so they were like definitely alive, like not maybe waved at you and then croaked, like they're definitely alive, so decades.
Now the adult. That's really impressive, right to freeze an adult and have it then reanimate and survive. That's amazing. Eggs are a different story, right, because like human eggs, you can freeze. That's not such a big deal. But why is that I've never really understood. Like I thought, if you freeze any cell, the water inside of it expands and bursts the cell membranes. And that's why it's like hard to freeze a cow and then like reanimate it. Why is it possible to do for eggs or sperm
or stuff like that. Why doesn't that same physics supply?
Yeah, so I am not an expert on cryopreservation, but I think that it has something to do when you're freezing human eggs, If you freeze them really fast, the cells don't lice the same way. This is part of why, like if you get meat, you don't want to like slowly freeze it and then defrost and do that over and over again because the cells lice and the meat taste less good. I think something about freezing them really quick, but I don't know why it is that they can come back after that.
Yeah, because even human embryos can do that, right, even fertilized eggs. It's sort of amazing.
It is. We should have a whole episode on cryopreservation.
Yes, let's do it right, but it's definitely not something you can do to like a human adult, right, Yeah, at least not yet. If people are working on that, right, preserving the brains of old baseball players for the future. All Right, so you're telling us that this is real, that tartar grades really can't go into this crazy state and then survive insanely long exposure to really difficult conditions and then be alive again and reproduce and be happy.
What's going on during that state? Like are they alive or are things paused? Like is there some metabolism happening? Like, what's going on?
I'm going to tell you the answer to that, Daniel after the break. Okay, So you wanted to know what happens when the tartar grades go into this like semi dormant state. So first of all, they like kind of squish up into a ball, and so they like pull their heads in that they pull their legs in, and they like expel and they lose almost all their water. By the end, they have something like two to three percent of the water they started with. Just to be clear,
that would kill humans. Like we're like, what seventy percent water or something. If we went down to three percent, we'd be gonners. We'd be gunners way before then. So as they lose that water, they start producing something called trehlos, which is a sugar, and it ends up forming kind of like a glass like structure that holds everything together
and gives it like structural integrity. And this has long been the explanation for why tartar grades are able to survive such incredible conditions, including the explanation you gave five years ago on Daniel and Jorge Explained the Universe. When I listened to that episode.
Oh all right, doing some research.
Yeah, yeah, well, you know, I needed something to listen to while I was walking around the other day. But so, here's the thing though about trehelos. Lots of tartar grade species. Some of them make trehelos when they go into this ton state. Some of them make quantities so small that we're not actually sure that it can do the function
of making this glass structure that protects organism. And some of them don't appear to even have the equipment at all to make trehillos, which suggests maybe it's part of the picture for some species. But that's not like an across the board answer for how tartar grades are able to do this, So it's complicated, and they make a bunch of other proteins So cryptobiosis is a term. It means hidden life, and so it's another way for describing
this ton state. And I found a line in a twenty seventeen paper that said, mechanisms that protect tartar grade cells during cryptobiosis are still poorly understood or completely unknown.
Ooh, that sounds like a fair description of all biology and physics.
And physics and you guys only have like six questions you need to answer. Get to work on that, guys.
And that's my favorite thing about the universe, that it's poorly understood or completely unknown, because otherwise it would be boring, right, I.
Feel the same way about biology, dude.
All right, So some of these guys have the these weird glass like proteins called trehillosies, which maybe provide some internal scaffolding that like support the cell when it's all dried out. But some of them don't even have it, but they can still do this ton state weird survive for everything.
Yeah, right, and so we don't really know what's happening there. We felt like we had a handle on it, and then we were like, oh, wait, some of these don't make that at all. So I don't know. Back to the drawing board.
Do you think that means that other target grades have different strategies or that this glass like structure has no connection to their ability to survive.
I bet it's both. So it could depend a lot on the ecology of the animal. So some animals that are in these environments with no water for longer might need sort of more extreme solutions to this problem. And so it could be something about like what kind of environment you tend to be in, Whereas if, like I don't know, maybe you're at the edge of a lake and you know, every once in a while you find yourself dry for five minutes, you can just kind of
like get through that. And so it might depend on your ecology how frequently you encounter these weird situation, or it could be different solutions entirely. I don't think we know yet, all right, And then I.
Have a basic biology question, which is, like, in biology, how do you answer the question this is how they're doing it, or that's how they're doing it. Do you have to develop an alternative where you're like knocked out that capability and show that like, if they don't have this protein, then they can no longer do this thing. And that's how we know. Because biology is such a huge, complicated roup Goldberg machine. How can you point to any one bit and say this is the essential bit.
Yeah, so it's super complicated. So sometimes you can say, like, you know, if trehelos is produced by a gene or something, you could go in and turn that gene off and then put the tartar grade through a drying cycle and see how it does and measure like, Okay, definitely it didn't make trehelos anymore and it died.
But even then, maybe trehelos is just a precursor to something else which is actually doing the crucial function. Right. I mean, there's just such a complicated series of events. It seems to me hard to ever point to one and say this is the explanation. Do you think it's just that we always want to simple explanation and there really aren't any, or that sometimes there really are simple explanations and we can find them.
There are probably rarely simple explanations, but I think that's pretty rare. Like when we did the human genome project, I think we expected we would like immediately understand the cause of cancer and a bunch of other diseases because now we have the whole genome and it's going to
be super easy. But no, it depends on like how the genome is expressed, lots of complicated extra bits, and you know, like for the Trehelos example, if you knocked out trechlos and the tartar grades died, maybe it's because Trehlos does something else earlier, like even when it's not in desiccation mode and you've killed it in some way
that has nothing to do with desiccation. So ideally you try to address the question from a bunch of different angles and see what the picture you put together tells you. But usually the answer is like it involves five thousand different genes that are all upregulated and different in and you know some of them are cell signaling genes. It's almost never like the answer is X. But you know, you guys have complicated answers to Sometimes.
Yeah, we do, absolutely, And sometimes you look at a big complicated system and there is no simple story that you can tell or model that you can use to understand it. But sometimes you can, right like ten to the twenty nine little molecules can all fly through the air together following F equals M. It's a very simple story about a lot of complicated things that are all
happening in concert, and somehow simplicity emerges. So I was sort of wondering how often that happens in biology, that you can pull one strand of a story and say this is the role this is playing, or if it's always just a huge courus.
Yeah, no, it never happens that it's one string, Like I like to joke that an ecology, like, you know, the only quote unquote theory that we have is it depends.
See that's my problem with biology exactly.
But you know, if you don't try to figure out all the things it depends on, then you never cure cancer or you know, you never save the endangered animals or whatever. So you know, you got to dig in anyway, know.
Exactly biology has no clear answers, but the questions are super duper important and interesting and so they're worth going after.
Anyway, I appreciate the effort you're making to understand my perspective. You're doing a great job. You're doing a great job, all right, So I forgot to answer a question that you had earlier, which was like, what is happening to metabolism and stuff when they're in this tot and the answer is it depends. Right, This might be pretty straightforward, all right, tell me. They reduce their metabolism, they reduce their oxygen use, and it's almost like they're frozen in time.
So they're not doing a lot of biological stuff when they're in this desiccated state.
But to me, there's a difference between actually frozen like there's no motion and very slow like are they alive? Is there some consumption of energy? Are they going to run out of energy at some point or is it really just paused.
I think it's got to be the case that there's still some consumption of energy, so one otherwise you'd expect that they could like live forever, and so I think at some point they kind of run out their stores. But of course during that time they're also like accumulating radiation damage and other sorts of problems of just being alive. They're amp in it down, but I don't think it's completely zero.
Yeah, amazing, Yeah.
And so because they're resistant to things like desiccation. Actually, I wish I knew the history of the first time somebody was like, let's throw these guys in liquid nitrogen. Doesn't seem super nice, but they've got this sort of
reputation for being super environmentally resistant. We've exposed them to pressures of seven and a half gigapasscals, which is equivalent to being one hundred and eighty kilometers below the surface of the Earth, and this is an environment that I just can't imagine you would expect that selection would be preparing these organisms for it, because it just doesn't come up. But they mostly did. Okay, at six hours, they were alive.
And so here's the thing. You'll hear like a list of like they can survive seven point five giga pass scales of pressure, blah blah blah. They can survive seven point five gigapascals of pressure for six hours.
That's pretty good, though six hours is a long time, Like we're talking the same like a hydraulic press. You know, yes, this is serious stuff.
No, that's a good point. Like so every once in a while, though, you'll see like a YouTube headline that's like they're immortal. This is incredible. You're right, it's incredible. They can survive this, but they can't survive it for long. If they're exposed to it for twenty four hours, they've kicked the bucket, all right.
And I can understand why evolution wouldn't need them to be able to survive one hundred kilometers underground for a thousand years. But it's not that hard to imagine why it would be useful to survive high pressure briefly, right, you can imagine some high pressure situation comet impact, dinosaur steps on you. I don't know, right, these things do happen. I suppose evolution can select for them. No, you're looking skeptical over there.
So if you are a tartar grade living in the Marianna's Trench, and I don't know if we have tartar grades in the Marianna's Trench, then you would have experienced selection for being able to handle extreme pressures. But I don't know if like a once in many millions of years, commet would still be exerting selection pressure now for seven point five gigapas skials of pressure.
Well, if we had like lots of pianos dropping out of buildings on people's heads the way I always thought we were going to have when I was a kid, I thought that was like a feature of adult life, you know, quicksand pianos and anvils, dropping on people. Wow, that was happening more often than you would expect evolution to somehow select humans to be able to survive you know, anvils and pianos and stuff like that, so you know there must be some biological equivalent to an bills and pianos.
First of all, I think Looney Tunes gave you a distorted view of adulthood.
But fair, fair, I feel like.
The strategy could just be like you have eye spots that detect a shadow overhead, and when that happens, your brain is just like piano move and you get out of the way. That seems like an easier path for selection to take than being able to withstand a piano dropping on your head.
Also, it probably takes a while to get into this ton state, so it's not like target grade is swimming along sees a comet coming down and then like switches into ton state like a superhero. This is like already happens to be in this state and then survives the impact, right.
Yep, yes, exactly, Okay, they can get into it, like I think a couple hours pretty quick, but not like immediately, not like snap in your fingers. It takes some work.
A couple hours. Isn't great for our superhero movie plot.
Yeah, that's true. But you know, if Michael Bay contacts us, we can like change some biology stuff. Like, as we've talked about in the past, what's important is your consistent so you know, we will consistently change their biology. Another incredible stressor they've been able to survive is a bunch of different kinds of radiation at levels that certainly would have killed people. Amazing, and we think that we know partly how they do this one. So tartar grades produce
a class of proteins called intrinsically disordered proteins. And you're like, why are you making me hear that multi syllabic phrase that is, in.
Fact exactly what was going through my mind.
Yes, I know, I've gotten to know you pretty well. But so the fact that they're disordered and like kind of all over the place is important. And so if you think of this like blobby thing, this blobby protein is attracted to DNA, so your genetic material that codes for everything else, and it binds to the DNA like electrostatically. And because it's sort of like this blobby all over thing, and you know, I wish the listeners could see the beautiful things I'm doing with my arms right now.
You're basically Italian right now.
I was just gonna say that, Yeah, you beat me to it. And so this blobby thing is able to just kind of like fall over the DNA like a coat, and then it appears to provide like a physical barrier to the radiation and protect the DNA from breaking. And in fact, they were able to get bacteria by like moving some genes around to produce these proteins, and then they mix them in to human cells, and these proteins
bound to human DNA. And when you blasted the human DNA with radiation, they were protected by these disordered, blobby kinds of proteins that were like coats for the DNA, radiation shielding for the DNA.
Oh my god, this is our superhero origin story. Bitten by a radioactive chartic D, Kelly gained that critter's ability to withstand radiation.
It's gonna be amazing coming it's fall.
Tart to Kelly. So let's reminder of listeners exactly what radiation is and how it damages to sell because we're talking about X rays and ultraviolet light and gamma radiation. Those all sound like very different things, but they're all just photons. Talking about very high energy photons, photons like the ones emitted by your lamp or your screen or by the sun, just higher energy, so they like penetrate deeper.
And the problem, of course, is that when these things penetrate into your cells, they can like blast open delicate stuff like your DNA, and that's how you get cancer, right, Or also sometimes that's how your kids end up being like amazing cross country runners even though you have no athletic skills yourself. Hypothetically speaking, right, mutations are sometimes good and sometimes bad. You never know, But it's like going into computer code and just like randomly changing a few
things and hoping that it gets better. Yeah, sometimes it gets worse, And so that's what we're protecting against, right, that's right.
And the study that I was reading it was looking at breaks in the DNA. So DNA is like a double stranded helix. It's almost like you took a ladder and that sort of twisted it so that it's like a spiral staircase, and they're looking at do you get one break in the ladder or two breaks in the ladder. So does one of the like long poles break or both of them, And so they were able to find that you get fewer breaks overall when you have this like radiation coat protecting it.
So why don't we all have this radiation coat. Is it like good to be susceptible to radiation because then you get these mutations? Or is this radiation coat like expensive in some other way that's usually not worth it.
I think it'll probably surprise some people to learn that usually when you get blasted with radiation, you get like cancer, but not superpowers. You probably generally want to avoid it. But to be clear, we don't actually know the answer to this because we don't understand the system very well.
But one hypothesis that I read about was that, you know, probably we don't all have these because if you've got something that's like a coat for your DNA, you know, like the way your DNA replicates is like stuff comes in and opens up the double strand, and like there's machinery that starts replicating stuff, and if you've got like a big coat covering it, you can't do that stuff and like gets in the way, And so it might be nice to protect you during a period where you're
not doing a lot of replicating your DNA because you're just kind of hanging out waiting for the awful situation you find yourself into. Pass.
So it's sort of like you're locking down your DNA, but then you can't really use it. It's like when you freeze your credit and then you can't like open a new bank account because you've protecting yourself against yourself.
That's right. You shouldn't have sent your Social Security number to that person over email. Kelly from the past anyway. So they're surprisingly radiation resistant. Let's talk about what happens when you dip them in liquid nitrogen or expose them to the vacuum of space next. All right, we're back. We've talked about how tartar grades are amazingly resistant to high pressures, amazingly resistant to radiation, although not completely resistant.
You can kill them eventually, but they're impressively resistant. Also, weirdly, we've been very interested in exposing them to temperature extremes, and so, Daniel, I have a question for you. There's this commonly made claim that you can expose tartar grades to very close to absolute zero and they survive cool This was from a paper in the nineteen fifties in a language I don't speak, and I couldn't find the original. How long have we been able to create temperatures close
to absolute zero? Has it been since the nineteen fifties?
So the history is that colder, earlier than you might expect. Like Faraday, Michael Faraday, who did so much amazing work on electromagnetism, he got stuffed down like negative one hundred and thirty s, so that's one hundred and forty degrees above app flue zero. That was in eighteen forty five. And then a guy named Doer after which the Doers are named liquified hydrogen down to twenty one kelvin in
eighteen ninety eight. Right, So this is already just twenty degrees above absolute zero in the eighteen hundreds, and then it was just ten years later we got down to four degrees kelvin when the Nobel Prize in nineteen thirteen for that one.
Oh wow.
And the current record, the closest we've ever gotten is one hundred pico kelvins. That's zero point zer zero zero zers or zero zerzero zero one kelvin. And there's an instrument on the International Space Station that's going to try to get to one pico kelvin is called the cold Atom Lab.
All right, okay, so definitely by the nineteen fifties you could be testing how tartar grades survived too close to absolute zero? And Daniel, what is absolute zero? I believe that's the temperature at which molecular stuff just stops and everything's frozen in place. Is that right?
Absolute zero is a theoretical limit we've never achieved and don't know if it's act actually possible. And essentially the argument is when things get colder, velocities internally slow down. It's a model of temperature that says things are hot because the stuff inside it is moving fast or wiggling a lot. And so what happens when things get colder, They move slower, They wiggle less. Okay, make them colder, all right, they wiggle less. Is there a point at
which all wiggling stops? And so sort of the way like when you learn calculus in high school, you could never actually approach infinity. You like approach it and see what the tendencies are. In that same way, we estimate that absolute zero might be the place where everything stops.
But that's extrapolating, and it's all kind of classical physics and quantum mechanics says you could never actually get there because there's a minimum energy to all the fields in the universe, so everything has to be buzzing because if anything was ever completely motionless, they would have no uncertainty, and there's a minimum uncertainty to the fabric of the universe. So we don't know if anything can ever get to absolute zero, if it's a real thing or not. But we've gotten pretty close.
Okay, and grades were able to handle it for at least a little while, even though I couldn't find the original paper.
Wow, So how cold did they get these heartigrades?
So the paper that I was able to find both because it was online and in my native language. They dipped them in liquid nitrogen, So that's negative one hundred and ninety six degrees celsius. Pretty cold, super cold, and ninety percent of them survived.
Wow.
Yeah, it was for fifteen minutes.
I don't think many Californians would survive at that temperature for that.
Long, you know, even though Virginians are a hardier bunch than you all Californians, I don't think we could have survived that either.
That's because you have to wrap your heart in so many layers of protection that it's not available during normal use. See, that's why Californians are friendlier.
That doesn't make sense. No, no, no, no, no, that's not how this works, all right. But one point that I want to make here is that some of the Tartar grades that were not in the Ton state also survived, and that was also true during the radiation experiments too.
Oh wow, and.
That makes us like those disordered proteins that we were talking about, maybe they help, but maybe that's not the whole picture, because you wouldn't expect the active, untunned individuals to be surviving if those proteins were the whole picture, because they're not making a bunch of those when they're not in the Ton state. So everything's complicated. Okay, But now let's get to the juicy stuff. Space. Some scientists have wanted to figure out if Tarte grades can survive
the super extreme environment of space. So first we sent them up into spacecraft and expose them to microgravity and some space radiation. But they were still like in this temperature controlled container thing. They did pretty well. In response to microgravity. Like, whereas humans are bones and our muscles fall apart in the ton state, they're just kind of chillin And.
Let's remind ourselves what is the extreme environment of space? What's difficult about space? So this high radiation because we don't have the magnetic field of Earth to bend those particles away, and we don't have the atmosphere to shield us. Then there's microgravity that's not so extreme. But then there could also be low temperatures if you're out in space, low pressure, and then of course no oxygen.
Yes, And so this first experiment was replicating the microgravity problem, but they weren't exposed to the vacuum of space, they weren't experiencing full radiation, and they were in low Earth orbit, so they were still protected by the magnetosphere, and they weren't experiencing the kind of temperatures extremes you usually experience in space. Okay, So another experiment or a set of
experiments amped things up. They put them in a container that had holes in it, and then they had a variety of UV filters on top of the different containers. So some of the tartar grades were exposed to the vacuum of space well, having their temperature controlled but not being exposed to UV radiation. And then others experienced various kinds of UV radiation well being exposed to the vacuum of space while still having their temperatures controlled in a
nice way. Does that all make sense? Vacuum of space they rocked at which, to be clear, it would kill people, right. The three Soviet cosmonauts who were exposed to the vacuum of space did not survive the experience, and that's pretty much what you should expect for the rest of us too.
The thing that first kills you there is what is it the low pressure that like, your eyeballs are boiling and your blood is boiling because you're used to being squeezed in by all the air.
I think what killed them in particular is that the nitrogen boiled out of their blood and it happened in their brains and they had a bunch of brain hemorrhaging.
That does not sound good, no, And.
So TARTA grades don't have the same circulatory system, the internal goo that keeps these little guys going. It's not the same system as ours. So you might not have to worry about nitrogen bubbles, but also they've gotten like a bunch of the water out already, and so you're probably not going to have like stuff that could bubble out. So they did great in the vacuum of space, but as soon as you opened those filters so that you reradiation could get them too, they started dying in droves.
Like I think, oh, really, maybe four of the like sixty survived that exposure, and that wasn't fair, like a whole lifetime. I think it was. Like one of the things that frustrates me about papers that are published in really high impact journals is that they give you a short page limit and so important details get left out. And I couldn't figure out how long they were exposed, but it couldn't have been more than ten days, because that's how long the entire mission lasted.
Said, we heard earlier that they can survive UV radiation on its own, and we heard just now that they can survive the vacuum of space. But you're saying that you combine them, then that snuffs them out, so they can't survive the combination.
So here's the problem. All these studies that we've been talking about, yeah, all looking at different species of tartar grades. So because a tartar grade could survive some high radiation doesn't mean that the next species that you expose it
to could survive. And also, not all of these studies have the exact same experimental design, so it could be that a bunch of the tartar grades that were exposed to radiation were exposed to it for like five minutes, but when you're exposed to it for ten days, then
you start dying. And so you know, when you hear someone like rattling off a list of all the extreme stuff that tartar grades can do, so some species can do some of those things for some lengths of time, but it's not like all of them can do all of those amazing things indefinitely.
So that's like saying, oh, polar bears can swim in cold water and grizzly bears can run really fast, and doesn't mean that they can do.
Both, yes, exactly, or that they could do both like forever. Like eventually, the polar bear is going to need to find land and stop swimming. So the space people don't invite me to their parties. The tartar grade people aren't going to invite me to their parties anyway, It's all right, I'm a downer.
Physicists will always invite you to their parties, killing because we don't have any.
Oh, oh, that's probably not true. Maybe, So here is the question everybody's been dying to know the answer to. In twenty nineteen, the Bearasheet Lunar Lander crashed on the Moon. It contained tartar grades, although the government officials who approved that launch did not know that because the company that had bought space on the lander did not disclose that they were sending biological specimens, which they are supposed to do.
And why were they sending biological specimens? Was this some can tartar grades survive experiment? Or were they hoping to populate the Moon?
I hope that it was a can tartar grade survive experiment, and also like that probably would have been a pretty cool pr move for their mission to be able to be like, oh, tartar grades in space, they really can survive everything. But for whatever reason, they decided to not disclose that it was happening, and I was not able to figure out what species they sent. I spent a long time asking. I asked Blue Sky. Nobody knew and
if you know, let me know. But so part of figuring out whether or not they can survive involves knowing the tolerances for that species in particular, right, But I don't know what species it is.
So the answer is it depends.
Well, we were talking about biology, so of course the answer is it depends. Biology. Doesn't disappoint but I think probably not. And here's why. All right, So, first somebody decided to stick tartar grades in bullets and then shoot them at sandbags to try to figure out if they could survive the impact and the subsequent shock wave that would have been experienced when the lander crashed into the moon.
This was an experiment done in response to the crash, like just to answer this question, not an independently motivated experiment.
That's exactly right. Wow, it doesn't say that in the paper, but I found an interview with the authors it sounds like that's true. And so there's a sentence in the paper that says, accordingly, we have fired tartar grades at high speed in a gun onto sand targets, subjecting them to impact shocks and evaluating their survival. Actually, this paper was all about if something hit the Earth and dislodged
Earth that had tartar grades. Could the tartar grade survive base and survive so that they could land on the Moon or Mars or populated. So it was a study about pants spermia on the possibility of the tartar grades becoming you know, interplanetary before the rest of us. I found an interview where the author said, probably they wouldn't have survived because of the shockwave. So it seems unlikely
that they survived. But let's go ahead and assume that maybe they got lucky and they survived the initial shockwave, because.
We don't know the speed of the descent of the lander, right, it depends on when it failed. If it fails just before it hits the surface, it's going to be a pretty gentle crash. If it fails really far away, then it's going to plummet towards the surface. But the Moon's gravity is still not very strong, so it's not going to be going that fast, right, But still it depends.
This paper that I read had a bunch of different impact speeds and shockwaves that they looked at, and I looked on the internet to figure out what we think the impact speed was of the bearsheet lander and based on their table, I think it's possible it survived. But then in an interview with the authors they said, no, no, no, the shockwave, it wouldn't have survived. But then I found another paper that was like, no, it might have survived based on the info and the table. So you know, it depends.
Were any of these papers written by anonymous authors from the Moon?
Oh, I don't know. Yeah, the TARTI grades achieved sentience. I think we have to worry about them sending like moon rocks down at us as punishment for all the things that we've done to them in the lab.
All right, so you think it's unlikely they survey the impact on the Moon once they're on the Moon, say they happen to survivor if you do, then what did they have to put up with?
So now they've got to worry about radiation. So the Moon doesn't have a strong planet wide magnetosphere like Earth does or a thick atmosphere, so they'd be exposed to all of the space radiation. And as we saw in those earlier studies, base radiation, solar radiation is bad for them, so that would kill them if they were exposed to it.
But let's say, well, what if maybe when they crashed, the little container that was holding them ended up burying itself under the regolith, and so now the regolith is protecting them from radiation. Creative, let's imagine that. Okay, so now you've got to deal with temperature. We know they can handle really cold temperatures. The moon at night has about a two week period where it's negative one hundred and thirty three celsius, which is negative two hundred and
eight fahrenheit. That's at the equator. We know that they survived negative one hundred and ninety six celsius, which is more than that, but for fifteen minutes, So we don't know if they could survive the law long polar nights, which are the equivalent of two weeks on Earth. But I think the bigger problem is one temperature swings back and forth between extreme heat and extreme cold, but two the fact that the moon does get really hot, so
without that atmosphere, things just heat up a lot. So without an atmosphere, things get really hot and really cold. There's nothing to sort of dampen the temperature swings. And as we saw previously, tartar grades don't do great at really high temperatures. They do pretty well with cold temperatures, but with hot temperatures they can't survive for super long. But let's imagine, Hey, we said that they're underneath the regolith.
They're protected from radiation. Underneath the regolith, you're also to some extent protected from temperature extremes. So maybe they're still alive there. But now you've got a problem with water. So in order to come out of their ton state, they need to be hydrated, and the lunar regolith is as wet as cement, so not super wet. So say it got hit by a comet that was bringing water, Well, I think that impact and the like heating up that happens when the comet hits the surface could kill the
tartar grades. But also if you get water, you're only going to get it temporarily and then it's going to like be lost to the vacuum of space. So I don't see them getting out of their ton state. And then the final big problem is food. If they did get out of their Ton state, they don't have anything to eat, Like, I don't know what species this is.
If this is the carnivorous ones and there was enough of a size variability, maybe the big ones could eat the little ones, but eventually you're gonna run out of it. So I don't see the tartar grades permanently settling the Moon.
So it's unlikely that the tartar grades are like water, bearing around, being cute and bouncing around the surface of the Moon, living happily. But it's possible that some of them are in the ton state, survive the impact, are buried in the regolith and don't need water or food because they're just basically paused for a long time, but maybe not forever.
I feel like that is a very low probability scenario, but it depends. I don't know that I can rule it out entirely. Maybe they're still in their ton state. We'll find them. I mean, we know that they can't be in that state for forever, and it's already been like five years, so I'm not super hopeful.
Sorry, But if a huge impactor slams into the Earth and like completely demolishes it so there's no record of life left on Earth, there could still be on the Moon some basically like frozen proof that there was once life on Earth. So that aliens visiting in the deep future could be like, oh, look, there was something here once.
Maybe, or those incredible temperature swings have killed them and the bacteria that live in their guts have consumed them and they've become liquid munch because biologies grows.
Also, all right, well, I guess we're just gonna have to wait millions of years for a huge impact and alien arrival to find out the answer to that one.
Ah, and people say I'm the negative one.
All right, well, thank you Tim for your really fun question. I think Kelly had a lot of fun digging into the research on tartar grades.
I did. It distracted me while I was sick and couldn't get out of bed, So thank you for this wonderful question. I had a blast.
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