Planetary Radio: Space Exploration, Astronomy and Science - Worlds of snow and ice

Episode Date: January 26, 2022

From Venus to Pluto, our solar system contains a myriad of planets, moons and other bodies whose surfaces are covered in snow and ice made of water and other exotic stuff. Saturn’s moon Enceladus is among the most intriguing. Colin Meyer, Jacob Buffo and their associates have modeled its ice and the plumes that emanate from the moon’s south pole. These geysers may not originate in the ocean deep below. Planetary Society editor Rae Paoletta is also fascinated by the worlds with ice-like deposits and activity. Bruce Betts keeps us out there with a Titanic random space fact and a new space trivia contest. Discover more at https://www.planetary.org/planetary-radio/2022-meyer-buffo-enceladus-plumesSee omnystudio.com/listener for privacy information.

Weird Worlds of Ice and Snow, this week on Planetary Radio. Welcome, I'm Matt Kaplan of the Planetary Society, with more of the human adventure across our solar system and beyond. You find them throughout our solar neighborhood, planets, moons, comets, asteroids and more, our solar neighborhood, planets, moons, comets, asteroids, and more, all with stuff that looks and acts like ice and snow, even if it's made of far more exotic stuff than water. We'll talk about some of them today with a focus on Saturn's moon Enceladus. That's where Colin Meyer, Jacob Buffo, and their colleagues have modeled the thick ice and the plumes that shoot far into space from those so-called tiger stripes at the South Pole. It's entirely possible that these geysers come from much closer to the icy surface than the vast ocean that hides below.

Their work also makes it to Mars, Pluto, and our own planet. My colleague Ray Poletta is equally fascinated by these worlds, both hot and cold. We'll talk with her about her new Worlds of Snow article at planetary.org. And Bruce Betts will share a terrific random space fact that ties Enceladus to yet another realm of ice, Titan. Did you catch Comet Leonard during its brief visit? Blake Estes did,

and his gorgeous image tops the January 21 edition of The Downlink. Scroll down to read about that good-sized asteroid that also passed by last week. It got within about 2 million kilometers, or 1.2 million miles, of Earth. It won't be that close again for another couple of centuries. We also learned about an exoplanet discovered by a team of citizen scientists using data from TESS, the Transiting Exoplanet Survey Satellite. It's about three times as massive as Jupiter, but has about the same diameter, which is interesting. And you've probably heard

that the JWST is now in orbit around that point in space called L2. It got there so efficiently that its fuel is now expected to last about 20 years, twice as long as planned. We've always got space headlines, great images, and other good stuff at planetary.org slash downlink. Ray Paletta is the editor for the Planetary Society. and other good stuff at planetary.org slash downlink. Ray Paletta is the editor for the Planetary Society.

She recently joined me from her home in New York. Ray, welcome back to the show. Got any snow outside your window there? It's melted now, but the few times I've taken my dog out in the last 24 hours, we've been getting some sprinkles, some dusting for sure. You know, I'm a Southern California boy, born and raised. And so I have to travel to be in the snow, usually not too far, certainly not as far as Mars or Io or any of these other places that you wrote about in this great January 24th article.

It's up at planetary.org. And it is fascinating to read about that fluffy stuff coming down around the solar system. Though I guess some of it you probably wouldn't want to take a bite out of. Yeah, I'm thinking that maybe the heavy metal snow on Venus might not be the best place to go skiing. I was reading about that. And with apologies to Frank Zappa, watch out where those canoes blow and don't you eat that multicolored snow. From the snow cano, if we want to keep the rhyme up too. Yeah, I'm thinking also of Io. I didn't really expect to read about snow there.

Isn't that wild? I mean, what doesn't Io have? I mean, I know I say that in the piece, but I think about this all the time. It's like it's got hundreds of volcanoes. And then you have this wild snow. I mean, that's been detected now many, many times. And it's coming from potentially these volcanoes, which just blows my mind. Because volcanoes are super hot and snow is not. So it really does blow my mind. So you cover Mars as well,

but I want to go back to what you mentioned a moment ago. And that was Venus because of the speculation still about volcanoes there, that maybe there's this interesting material or element spewing out that's changing the look of the planet. It's cool because it is kind of a mystery that goes back all the way to 1989 with Magellan. It picked up that there were some strange, unexplained brightness coming off of Venus. And since then, all these different elements have been thrown out. What could be causing this?

As well as some unexplained dark regions. Some scientists might have thought it was something called tellurium, as well as some unexplained dark regions. Some scientists might have thought it was something called tellurium, but now others think that it could be lead sulfide, which is pretty incredible. I mean, it is literally heavy metal, and Venus does everything pretty heavy metal, so that would be fitting in a metaphorical sense as well.

One more stop. Enceladus, you talked to another friend of the show. I mean, you talked to Tanya Harrison, too, who's been heard on the show. But Sarah Horst talked to you about what's going on with those geysers that we've seen up there. And I guess Enceladus likes to spread the snow around. Oh, my gosh. I think this is one of my favorite parts of the whole piece was learning about this so-called snow cannon from Enceladus. Basically, Enceladus gets this quote-unquote snow, right?

But it's not just enough that Enceladus can get the sprinkling. It's also so powerful that it gets to some of Saturn's other moons as well. So I just love that Enceladus is spreading the wintry vibes all around. There's more that makes this special. It's the whole look of the piece, which is like nothing we've ever, that I've seen anyway, that we've done on our website. And it includes, well, you, you talk about these great little animated gifts. Yeah, no, I love the pixelated art that we did. It almost looks like a video game. And Sam Marcus, the artist who designed this is so talented. Definitely check out

some of his other work. I think we'll be linking to the Giphy so that you can share the gifts all over the internet. I just can't get enough of it. I especially love Enceladus and IO. They are really, really fun. And we'll put the link up to our Giphy site as well. Ray, great piece. And thanks for coming back on the show to talk about making snow all over the solar system.

Let it snow. Always a pleasure. Thanks, Matt. That's my colleague Ray Paoletta, editor for the Planetary Society. I won't lie, hearing that the plumes shooting spaceward from Enceladus might not originate all the way down in that moon's ocean was slightly disappointing. After all, we all dream of flying through them with a spacecraft capable of detecting very complex organics and maybe carrying a microscope, tools that could reveal evidence of life.

Life that was mining its own business in a warm, salty ocean before it got sucked into a crack and spewed into the cold of space. But the modeling work done by the Meyer Ice Mechanics Group at New Hampshire's Dartmouth College doesn't eliminate that possibility. It just adds what may be a more realistic view of at least some of what's happening as much as a billion miles or 1.7 billion kilometers from Earth. Professor Colin Meyer and postdoctoral researcher Jacob Buffo joined me a few days ago for a conversation about the modeling they and other colleagues are doing, not just of Enceladus, but for Mars, Pluto, and even our own

world. Colin and Jacob, thank you very much for joining me on Planetary Radio. I'm very happy to be able to talk to you about this recent work that may have a lot to say about looking for life on or under the ice on Enceladus, that moon of Saturn. But I think we may get to some other topics as well. Thanks for joining us here on Planetary Radio. Thank you so much. Really glad to be here. Yeah, thank you for having us. Our pleasure. As you guys know, the Cassini mission first showed us those plumes coming out of those so-called tiger stripes at the South Pole of Enceladus. This is back in 2005. So, man, going on 17 years ago now.

What's wrong with the widely expressed speculation ever since then? I'll call it speculation and not hope that those plumes are coming directly through cracks from that ocean way down beneath kilometers of ice. Colin? Yeah. So after that observation, two ideas were sort of proposed. And one of the ideas was this Hereford idea that the cracks went all the way through to the ocean. That was exciting because at the time, it wasn't clear whether there was an ocean on Enceladus. It was hoped and thought that there was, and they didn't know how big it was, if it covered the entire moon or just some sort of reservoir. That's even still debated now, though the gravity data does suggest that it goes under the entire moon. But if you look back in the early teens, people were still drawing maps of having sort of a regional ocean

underneath the South Pole. But so this idea, this Hereford idea that the cracks went all the way through the shell and that it was accessing sort of sub-ice shell material, and that was what was causing the plumes, that was one of the ideas that was proposed. But that actually wasn't the dominant idea when the first ideas came out, but the other idea was proposed by Francis Nimmo and collaborators. And this was a sheer heating idea. And the other idea was proposed by Francis Nimmo and collaborators. And this was a sheer heating idea. And this was building off some of Francis's work, which said that on these tiger stripes,

there was actually heat that was generated as sort of quakes moved along them, driven by tidal motions. As those quakes propagated along the fractures, they generated heat just in the way that putting your hands together and slipping them past one another might generate ponds. That was a very exciting idea about what would be the source of this sort of heat anomaly. There's a lot of heat coming out of these tiger stripes. This idea that the sheer heating was causing it caught a lot of attention in around 2007. Your work with the modeling that you've done has followed up on this. I guess it

was first presented in December at the American Geophysical Union fall meeting. It has shaken things up about the plumes, I think it's safe to say. I mean, it's kind of a big deal, right, if they're not coming from the ocean. I mean, you don't know that, but would you say that it's more likely based on your modeling that the source is perhaps quite a bit closer to the surface? Well, I think one important thing to say about this is that in the original shear heating model that Francis proposed, he was looking at a pure ice shell. So there was no salt entrained in the shell and therefore couldn't produce any sort of the signal that Cassini observed. And so when we accessed the problem, we said, okay, but we know that the shell is salty. And so shear heating, we should still analyze this problem, even in the case of shear heating, because we know that there's salt entrained in the shell and that would affect the shear

heating dynamics. And then in relevant parameter regimes, we can still get material near to the surface that could be then geyser material. That sort of is the core of the result is that even in the shear heating regimes, we could still produce geyser material. Do I remember correctly, Jacob, that those salts, they were also discovered by Cassini because it was flying through the plumes, right? It couldn't detect really complex organic molecules, but it could pick up stuff like salts. Yeah, yeah. They flew through the plumes essentially and basically registered that there were salts as well as some silicates in the plume particles that they flew through and detected. So they did see those. So we know that they're

coming from somewhere salty. And I think the big question was, where is that coming from? The go-to answer was the ocean. And I think the big step that Colin has taken in doing this modeling is showing that there are processes that can also produce these type of salty reservoirs within the shell. So you don't necessarily have to get all the way down through to the ocean to access some salty reservoir of fluid. The modeling that you've done is based on these, I'll call them pockets, you may have a better term for it, of liquid water kept liquid because of those tidal forces, the same stuff that makes Io over at Jupiter such a

nasty place to visit. Does that also help to explain the salts in the plumes? Yes. I think the important thing about the tidal forcing is really to generate energy to create this melt. The salts getting into the ice shell is a bit of a different process, but it's kind of something that we took as an idea from things that happen on Earth. So when our own ocean freezes out and produces sea ice, whether that's up in the Arctic or down around Antarctica, the ocean freezes out and some amount of salts from our ocean gets entrained in that ice. It's not completely fresh ice like you would get on a lake or something like that. fresh ice like you would get on a lake or something like that. So the idea is that when these oceans on these other worlds freeze out to form these icy shells, there's going to be some amount of residual salt in those shells as well. Once you start kind of flexing and squeezing this ice shell that's full of salts, if you have any regions or something like that, that is a higher,

has a higher content of the salt that can actually reduce the melting point and kind of provide a localization for the kind of first spot to melt within these shells. And once you concentrate those maybe through different processes, you can keep melting easier and easier just because you've localized all of these salts in one spot. One of the things that Jacob is bringing up, which is really important, is that the process by which salt gets into the shell may be different than how, you know, requiring an ocean. The fact that the plume particles have salt in them, we draw a direct link from the plume to the ocean, sort of skipping the shell. shell. And I think that part of the reason and what Jacob and I have been working on for the past couple of years is saying that actually these shells are very salty. And people know this. I mean, if you just look at the many of the icy satellites around the solar system, they are salty, they have salt, you can see that they're not pure ice shells. And that salt entrained in

the shell actually causes the dynamics that Jacob was talking about, which is exciting. And so I think the work that we're doing with this shear heating model is really drawing this connection between processes that are happening in the shell, possibly explaining these other phenomena. So it's another sort of participating idea. Jacob, it wasn't maybe the major point you were making, but I do want to go back to what you said about the salt affecting the melting point of that water. I mean, it's really, it's the same mechanism as salting roads, right? Yeah, exactly. The same reason that you're in a cold place on earth, we put salt on the road so that it melts at a lower freezing point. That happens in any salty

system. So like, again, our ocean freezes at about negative two degrees Celsius, as opposed to zero degrees Celsius, just because there's some amount of salt in it. And so that should be the same thing on ocean worlds and in these icy shells. Some of the things that we're also looking at is can you have geological processes within these ices that could kind of localize these salts. Folks have coined this term called cryovolcanism or cryomagmatism. That's the idea that on these icy bodies, you would basically have volcanism, but instead of having liquid rock like we do here for volcanoes on Earth, it would just be salty water. This salt water will behave in kind of similar ways where it can

fractionate out and split up and this salt can move around and potentially create different features in these ice shells. So that's another thing we're thinking about is, you know, how does this salt get distributed and what does that mean for the geological properties of these ice shells, just like we have all these different kinds of volcanisms and different geophysical processes occurring on Earth? volcanisms and different geophysical processes occurring on Earth. What you're describing seems to me, I'm going to guess, only scratches the surface, no pun intended, of the complexity that has to go into the kind of modeling that you have done. I mean, nobody's been to Enceladus, at least not yet, but you and others have been able

to build these models of what may be going on, models that have use in other settings, and we might be getting to that a little bit later. I think it's utterly fascinating that you're able to do this, but what does it take to create these sorts of complex mathematical models, Colin? Yeah, that's a great question. So one of the things that we've been doing is leaning a lot on models that have been developed for Earth, for sea ice, as Jacob was talking about. So one of the things that we've been doing is leaning a lot on models that have been developed for earth for sea ice, as Jacob was talking about. There's a key idea in models when we think about solidification of sea ice is this idea of partial melting. Not only does the salt

lower the melting point of the system that's working on salting the roads and things like that, but it also gives this sort of third system where you can get partial melting. And so that means that when you go above a certain temperature, you cross this threshold, and then there allows to be little pockets of melt within a matrix of ice. And so one way you can think about this is taking a bowl of ice cream. Put the bowl of ice cream in the microwave, it will all melt, and then it will be all liquid. But if you leave the bowl of ice cream out for just a minute or two, it is starting to melt, right? There's still ice chunks and other melt in there, but it's not fully melt, and it's not fully solid. There's this mushy zone as they go.

And so that's what happens in sea ice on Earth. People have written down mathematical models for how you generate these mushy zones for Earth systems. And this group at Oxford developed very powerful code to model these sea ice systems and the mushy zones that they develop. And so we're leveraging that code developed for this idea of having a mushy zone, a region of partial melting. And we're using it not in a CI system, though sometimes we do analyze those systems as well, but we're using it in the context of Enceladus. I think one of the key ideas, getting back to your question, Matt, is we're starting with an idea. This idea is let's revisit the shear heating

model of Francis Nemo. Let's, let's add salts to it. We put that into this model, this CI developed model softball. And then we want to sort of like probe one physical question. And so the physical question we're after is if you add shear heating to this, do you produce a zone of partial melt around the fracture? Like that little bit of ice cream that's melting around the side, that then allows the melt to then migrate along the fracture and then potentially out into a geyser. I think the key components to our thinking in these systems is identifying a question or a topic and finding the tools to

analyze it and then where those tools come from and then looking at the sort of implications of that. You mentioned that you've adapted this model that was developed at Oxford. By the way, is this the one called Softball? Yeah, this is Softball. Exactly. Yeah. Love that name. It seems very appropriate somehow. I note that you had co-authors on the presentation at AGU at Oxford, also UC Santa Cruz and NYU. So this is an ocean hopping finding. Indeed, indeed. When you run this model, how do you find the data that you need to base it on when you're talking about a world that we have not been to? I assume that you've already actually said that that Cassini data is pretty valuable.

Definitely. Yeah. So this is an important thing. Right. We don't know the salt compositions for the shell. We don't know the salt compositions for the ocean. And so we develop sort of sensitivities in our model to those different things. So how does the model change if we change these parameters? That's a way of dealing with the fact that we don't know what they are generally, though we do know from the Cassini data, some levels, if we just sort of like extract the plume particles that we get and say, ah, this is the ocean chemistry, then we could say what the ocean chemistry is. Though our results are actually sort of a cautionary tale for that and saying that, hey, maybe it's not a great idea to just go one-to-one particles coming out of the geysers to the ocean. I mean, even if you ignore our results completely, I would still agree that it might not be a great idea to go one-to-one particles to ocean because there's so many

processes going on in that process of extracting liquid water at depth all the way up into particles. But leaving that aside, we can take sensitivity to our model to these different parameters. Another way to ask the same question is, is sort of what are the predictions of the model? And how do they compare to other observations that we can see from Cassini, the heat flow that's coming out of the South Pole, or the volume of ice particles that are emanating, you know, if the if the volume of ice that can come out of the geysers is 100 times what my model would produce partial melting, then that means that it's probably not a good model for the system. And so those are the types of data. In the heat flow example, there's really

nice work describing the decay rate of heat away from a tiger stripe. And so the shear heating model, it produces a lot of heat at that location, and then that heat decays away. And so if we are able to match the decay rate, or at least spectra of the decay rate from the tiger stripe, that could be a good description of what's happening thermodynamically. So far, so good. I mean, is the data kind of matching up with what you thought, what the model told you you might see? Well, I mean, so all of this is preliminary, right? So we haven't published this paper yet. We're still working on it. But yes, those are sort of our basically two targets is trying to figure out under what parameter regimes do we observe the things that are observed in Cassini? And, you know, our preliminary work suggests, yes, that we can find parameter regimes that can produce these sort of, that can match those observations from Cassini. Jacob, you called this a cautionary tale.

Do you remember what you meant by that? Colin touched on it a bit as far as things like extrapolating the chemistry from the Cassini measurements. is kind of this tricky bit where if you're directly accessing the ocean, there's a chance that that is a more representative chemistry in the plume particles, but that if there's kind of this intermediate step, there could be an issue, I think. And for astrobiology, it's kind of the same thing. You know, when we're thinking about, are these oceans habitable? You know, we want to know, can things live in these oceans? And I think some of the big questions related to that are, are there the nutrients and energy sources in these oceans that would make these oceans habitable? But it's kind of like, you know, me trying to guess what's in your kitchen right now, food flies or something like that, right?

And, you know, if I can actually be there, and if we have missions that can actually get to the ocean, then you can take these measurements and look around and see what's there and determine whether there's enough there that these potential organisms could use. But if we're just detecting these plume particles, you kind of maybe have like a shopping list of things that somebody has, if you've had these particles erupted through a plume. you've had these particles erupted through a plume. But if these chemicals have been entrained in the ice shell and then processed and concentrated and melted and refrozen, it's kind of like finding that shopping list after it's gone through the washing machine or something, right? You just have these like little pieces and you're trying to figure out now what's in this kitchen and what's usable and like, is this a good representation of what's actually down underneath the surface? So we need to be cautious, I guess, in understanding that there might have been a lot of processes and revamping and, you know, maybe only a small amount of this information

from down deep actually got trapped in these particles that we're measuring. So that was kind of my thinking for the cautionary tale quote. So has this model and the results you have so far, has it at all affected your enthusiasm for some future mission to that moon of Saturn? Not at all. No, I mean, I think that in many ways, the goal of this is not to dampen any excitement for Enceladus in any way. is not to dampen any excitement for Enceladus in any way. This was purely my enthusiasm for Enceladus, finding a way to say, oh, this is a cool problem. I would like to work on this. So marrying my excitement for Enceladus and science.

I'm excited about trying to understand how things work and going to Enceladus and figuring this out. And if we go to Enceladus or other lines of evidence prove that this theory is completely wrong, I mean, that's flattery of the greatest degree, right? I mean, I'm excited to learn how it works. And, you know, I'm just thrilled to participate in it. Mars, Pluto, and Mar are just ahead when we rejoin Colin Meyer and Jacob Buffo in moments here on Planetary Radio. Hi again, it's Casey Dreyer, the Chief Advocate here at the Planetary Society. Our 2022 Day of Action is set for March 8th.

This is your chance to advocate on behalf of space science and exploration. of space science and exploration. If you've heard us talk about how effective and just personally rewarding our past Days of Action have been, this event is for you. Learn how to participate in this virtual online experience by visiting planetary.org slash dayofaction. If you live in the United States,

we'll book your congressional meetings for you and also provide you expert training so you can be the best advocate possible. If you live outside the U.S., you can still make your voice heard on March 8th. It all starts at planetary.org slash dayofaction. Join us as we speak out for space. Before we bring it in a little closer into the sun here, I want to give you a chance to say anything else that you might like to about

your partners in this work. I talked about the other institutions involved, but I also saw that your colleague there at Dartmouth, Tara, is it Tara or Tara Tomlinson also contributed to the work? Yeah, Tara Tomlinson. Yeah, she's a new grad student in our group. She's doing awesome work on two things. One, she's looking at solidification using softball and trying to understand how permeability of the ice as it's solidifying, we have to put that into our model. It's a constitutive relationship, meaning that we need to directly say how the permeability, the rate at which things can flow, depends on the density. And there are many different models for this. But in this case, we don't actually know which ones are good models

and which ones are not good models. And so when we do our solidification experiments, or in this result, you know, the stuff we're talking about today, I have just decided which constitutive model I'm going to put in based on some experiments in the past. But to be fair, I don't know if that's the best one to model in this system. And so Tara is doing great work trying to understand, you know, what are the differences? How do they produce different solidification rates? And she also is doing another project, which is really exciting. Too bad she's not here to talk about her work, because it's very cool'm trying to understand the glaciers on Pluto, how you might have subglacial systems of sort of hydrology moving along the glacier systems and who on Pluto,

but it's no longer water ice. We'd actually be considering the nitrogen ice. They might have analogs to, you know, glaciers here on earth and having systems, similar systems. Very cool. Again,

no pun intended, but I bet that's something that people like Alan Stern are following pretty closely. There's one other question that occurred to me. With the speculation about the possibility of biology, or at least the capability to support life in the ocean, have you or have others thought about if indeed these geysers are emanating from liquid water sources, these pockets much closer to the surface, do you still see any potential for biological activity there? Could you see critters existing happily in these pockets? That is a million dollar question, I think, at least, right? And hopefully, you know, as these missions

go out and collect more data, we'll get close to that. But I think our kind of overarching follow the water goal that leads a lot of this astrobiology work is a big component of that. And so anywhere that you can potentially have liquid water, whether it's a nice giant ocean or even just these small pockets and regions where there might be some amount of liquid water, is going to be good places to look for life. And I think, again, making the analogy between what we see on Earth is super important because we see organisms living in these pockets and channels in sea ice. So the same way that we took this computer model from the physics that govern sea ice dynamics and things like that, I think the analogy from the biology side is just as important in understanding how these super special extreme

organisms can optimize and make use of these small pockets and channels, but still thrive and reproduce and live in just whatever environment you can throw at them. So I think any anywhere with water is still a good place to, to look. Definitely, definitely. And I think an important point about that's underlying what Jacob's saying is that the model that we wrote down, isn't very Enceladus specific, you know, there that we put in the Enceladus parameters. You know, we put in the Enceladus parameters, you know, the gravity and things like that. The model equally applies to other icy satellites in the solar system. Like there's a lot of excitement about Europa.

It's unlikely, well, I don't know. I don't want to make statements like that. But it doesn't seem like there are surface to ocean fractures going through Europa's really thick shell, but there may still be plumes and they may arise from the sheer heating mechanism. And so, you know, having a little bit of a mechanism to have shallower water in Europa that doesn't rely on fractures going all the way to the ocean or could be very exciting. I think our audience is probably tired of hearing me say it, to say nothing of Jeff

Goldblum. But, you know, life finds a way, at least down here on Terra Firma. Let's move to that other world that we talk a lot about on this show, Mars. There was this quote in something that I read, if life ever originated on Mars, it may have followed liquid water to progressively greater depths. Now, we've talked a lot on the show about, hey, the place to look for life is under the surface, but most people, I think we're just talking about a handful of meters. You guys are talking about a lot deeper down, at least in the current day, right?

How does this work? I think this is probably in relation to some work that I've done with Lu Zhu Oja, who's a professor down at Rutgers. The big problem with Mars, right, is that at least currently it's hard to have water on the surface. And that's what we're looking for is that water. And so he had kind of come up with this idea that if you have these thick ice sheets on Mars, if they can get thick enough that you could maybe insulate the ground

enough that you could basically melt the bottom of these ice sheets just from the geothermal heat at the base. And again, this is something that we see on Earth. So we're just ripping off glaciology again. But so we basically created a model to simulate that to see if or how much ice you would need to to, how thick these ice sheets would need to be to get this melting at the base. Because, you know, again, if you can produce this liquid environment at the base of these glaciers, then you could potentially house organisms. And that's something that we see in subglacial lakes on Earth as well. You know, these pockets of water beneath ice sheets in Antarctica that have been maybe separated for millions of years from the open ocean or the atmosphere or things like that.

But they're still full of life, bacterial and stuff like that. That was kind of the goal of that study. how much ice and water could have at one point been on Mars to basically predict how thick these ice sheets could get, and kind of figured out that given the predicted climate models, that these ice sheets could get thick enough to actually produce some significant melting at the base and potentially create environments that could house organisms through different glaciological cycles. So you speculate that that life, once it formed, perhaps 4 billion years ago, Mars was drying out already, and it's a pretty dry place now, that it may have found its way a lot farther down?

Yeah, yeah. There's some great groups now that are looking at kind of like the present ground ice on Mars. So even though right now we just kind of see ice in the polar caps above the surface, there is probably and there's good measurements that show that there's probably a ton of ice like in the ground. So think about more like permafrost on Earth, this is actually down deep beneath the actual surface. And if you keep going down below that, the idea is that you could probably get to aquifers beneath this ground ice. So you're just going to kind of follow that water down and down and down as it would be the survival strategy, I guess. If there were these communities and then all of a sudden, you know, Mars loses its atmosphere and then starts losing all of this surface water and ice that potentially they're just going to keep traveling down and following wherever that liquid water is still stable. It's what I would do. How far down are we talking about? Are we talking meters, kilometers?

I don't have a good estimate right off the top of my head. But I mean, this ground ice is probably tens of meters, if not deeper. But it could be kind of a heterogeneous thickness throughout. if not deeper, but it could be kind of a heterogeneous thickness throughout. So they are using radar as kind of, I think, the primary method to measure the location and kind of the masses of these ground ices. So I don't think there's a definitive regional or global map yet about the complete thickness, but it's something that they're trying to kind of chip away at. And permafrost on Earth, you can find kilometer-thick permafrost on Earth does, you can find kilometer thick permafrost

on Earth. Wow. Colin, what this tells me is that there's a lot of interesting stuff going on in your research group there at Dartmouth. Before we close out, I just wonder if you want to say anything about how this work and these models are telling us more about our own planet. Well, yeah. So one of the things that we're excited about here is connecting terrestrial processes to planetary processes and vice versa, trying to understand sort of these systems, whether they arise on Enceladus or on Earth or another planet, and see what's sort of like translatable and what are some new directions that we can push.

There is work that we're excited about in permeability, you know, that has applications to sea ice on Earth, but also has applications to the sort of like shell growth of icy satellites and things like that. So I do a lot of work on glacier hydrology on Earth, writing mathematical models for how water trickles through snow, seasonal snow or glacier snow, how snow compacts, and then also how meltwater flows under glaciers. We have a collaborator in our group, Aaliyah Summers, who has a model she wrote to describe the motion of water as it flows under the glacier, whether it's channelized or in a thin sheet. And this is the model that we're going to be applying to Pluto,

but we're also applying it to places in Greenland. So I think it's an exciting nexus to be at, thinking both about planetary processes, but also about glaciers on Earth. And I think that one of the driving, a couple of the driving questions on Earth are climate change. Glaciers are disappearing and as they disappear, sea levels are rising and that's inundating communities

and these sorts of things. And so understanding the processes that are controlling that is really important. On the planetary scale, there's a little bit sort of, I would say, lower urgency. And it's driven by this question of curiosity around finding, you know, habitable places. But that's really exciting and fun and great to think about. And so I think it's cool to sort of

like leverage both sides to think about things that are urgent here on Earth, as well as things that are sort of like cosmic in many ways and sort of driven by curiosity. What are your thoughts, Jacob? Yeah, I mean, I think one of the special things about this work and our work has really been that we kind of came from different backgrounds. You have more of like an Earth glaciology background and I come from more of the astronomy and astrobiology and planetary science background. more of the astronomy and astrobiology and planetary science background. But having those different perspectives and to try and come at these problems at totally different ways, I think is really helpful and really important. And that's kind of across the board.

We've been super fortunate to work with a lot of different people who do a lot of different things. And I think that's really integral to expanding the way that we're thinking about these questions and has definitely helped open at least my eyes to the best ways to go about these things. Involving a bunch of different people who have a bunch of different ideas and a bunch of different approaches to these things is really the best way to get at these questions. And that's planetary science for you. Multidisciplinary, right? Listen, you guys are at Dartmouth up there in New Hampshire. You're no strangers to ice in your own environment.

What's the weather up there today? Well, there's about a foot of snow on the ground and it's cold. It's a little icy, but, but yeah, no, it's, it's a beautiful sunny day. Enjoy it. And I hope that you can continue to enjoy this great work, this modeling of phenomena all over our solar system. My congratulations to you guys and the rest of these researchers. And tell Tara that we're sorry we missed her,

but maybe another time when we talk about her work on Pluto. Thanks, guys. Thank you so much, Matt. Yeah, thanks so much for having us. This was great. Time for What's Up on Planetary Radio. We are back with the chief scientist of the Planetary Society, who is ready to tell you about that night sky and a whole bunch of other stuff, including, I will just bet, a random space fact.

Welcome. Before we get into it, I got this message for you from Kent Murley in Washington, who appreciated your pop culture reference last week. It was sort of an origami reference that appropriately sailed right over my head. He reminded me that it was from Airplane, the movie. Yes, I don't even remember what I was referring to. But yes, you can make a brooch or a pterodactyl. Yeah, that's... Anyway, yes. Moving on.

What's up? Low evening west, Jupiter. Going away in a few weeks. Still hanging out there. And in the pre-dawn east, the party has started. We've got super bright Venus. and over to its right, Mars. They will be joined on January 29th by a very thin crescent moon. So go check that out.

Also, hey, it's northern winter. That means Orion. Check out Orion over in the southeast in the early evening. Draw a line through Orion's belt. One direction, you get Sirius, the brightest star in the southeast in the early evening. Draw a line through Orion's belt. One direction, you get Sirius, the brightest star in the sky, night sky. And the other direction, you get at least really close to the Pleiades star cluster. So have fun. You know what else I noticed up there?

Castor and Pollux, not far from Orion. Orion is just, that's my favorite constellation. There was no question. Yeah. Castor and Pollux up there in Gemini. And then also the whole winter hexagon, which is, uh, six bright stars that form, you know, a hexagon because they're six and they're kind of sorta evenly spaced. Anyway, look it up or, uh, buy someone's brilliant book that talks about it.

Okay. And there'll be more hexagons coming up later in the segment. It's a hexagonal themed show. But on to this week in space history. It is a sad week or more positively Space Heroes Week. Every fatality in a spacecraft in the U.S. space program happened during this week. 1967, the Apollo 1 Fire 86 Challenger in 2003, Columbia. We remember all of them and what they gave for space exploration and humanity.

And to give a little bit of a much more positive note, 1958, Explorer 1 was launched, the first successful U.S. satellite. A big week in U.S. space history, no matter how you look at it. Yeah, we salute those heroes as we do every year. On to random space facts. Oh, I like that at the end. You probably heard of Enceladus. I'm guessing you heard a lot about it just a little bit ago.

Yeah, just in the last half hour, 45 minutes. But have you ever wondered how much bigger is Titan than Enceladus? Have you wondered that, Matt? Yes. The answer is a lot. All right. Well, that's my random space fact for the week. No, I've got more. Over 1,000 Enceladuses could fit inside Titan if you squished them up and got rid of the pore space. Wow. Titan's a lot bigger than all the other moons of Saturn. And no wonder people thought that Enceladus was too small

to have an ocean inside. Surprise. Yeah, exactly. We move on to the trivia question where I got mathematical-ish. And here was what I asked. I said all of the following are about telescope primary mirrors. You know, popular with the kids these days. What is the sum of the number of hexagons of one 10 meter telescope divided by the number of JWST hexagons plus Palomar Hale telescope diameter divided by the

Mount Wilson Hooker telescope diameter. What does that math give you in the end? How'd we do, Matt? I was surprised to see how many of you out there loved this and want more mathematically based questions from Bruce. Wow. Isn't that something? I will start with this response from our poet laureate, Dave Fairchild in Kansas. Start out with the hex of Keck. It's 36, you know. 18 is the hex for Webb. Lagrangian, we shall go.

Then take 200 inches for the Pyrex Palomar. And finally, 100 for the hooker seeing stars. So now we've done the research and our numbers are assigned as standard mathematical. Our order is defined. Now both of the divisions give integers of two. So adding them will give us four. Is that the answer, Bruce? Yes, that is the answer and nicely defines all of the numbers in the equation.

Two plus two is four. We have proven it once again. That's such a relief. And here's a surprising answer as well. Why surprising? Because I checked back through six years of entries and Mel Powell, funny man, Mel Powell has never won, at least not thanks to random.org. He did win once because he had a funny response, but not because of random choice. Well, Mel, it finally happened. Congratulations. It's my revenge for the toy with emotions wisecrack that came from you last week, Bruce. Well, fine, Dr. Betts, the gloves are off. Here's the answer.

Man. The number of letters in the name, as he commonly uses it, of our distinguished planetary radio host, plus the numbers in the name, as I commonly use it, of this less distinguished but still earnest TPS member and trivia contest participant. That sum divided by the combined number of times the letter B appears and the letter T appears in the name of the planetary society's evil, yet distinguished chief scientist. Because sometimes two plus two does not simply equal four the easy way. Harumph. Well, Mel, you're right. except that if I follow your formula correctly, I came up with 4.5, which would round up to 5, of course. But at the bottom, you did say 4, so I think we have our winner, Bruce. Well, I guess no matter what happened with the equation, we have our winner, thanks to you and Random.org. So congratulations, Mel.

Well, I accept part about calling me evil, but it's kind of balanced by the best use of harumph I've heard in a long time. Yeah, boy, it wasn't just your everyday harumph, was it? Mel, you have won yourself that beautiful startorialist necktie. It's the gold ink on black, I think, that they're going to provide to you. And Bruce, I know that you have just been livid with envy because you're looking at my tie right now. I bought this from Startorialist. It's the silver on, I think it's royal blue JWST tie. And I am just there. I put it on a nice shirt just so I could wear a tie for you. Oh, dude, it is so cool looking.

Thank you, Startorialist, for making this prize available to Mel, who no doubt will be thrilled. I got a few more. Chris Bailey in Texas. I teach sport biomechanics and I always make sure my students include the units in their answers. I'm fairly certain that's the first time I've ever used or even considered hexagons per meter as a unit. I had a few other people took you more to task because you didn't specify imperial or metric. Well, I will take them to task. You go ahead and then I will take them to task. Here's what came from Narahari Rao, who's also in Texas. Palomar Hale Telescope Primary Mirror Diameter, Mount Wilson Hooker Telescope Diameters have been assumed in meters. I would think that Dr. Betts would want us to use the standard SI units.

When used in inches, the sum totals to exactly four. And Patrick Luski in California. I was hoping the answer would be 42. Me too, Patrick, but no, sorry. Pierre-Louis Fan in France, he was going to complain about the imperial units, but then realized the equation is dimensionally homogenous, so it works with any units. Is that the right term? Dimensionally homogenous? I like that. I usually have heard the single word, dimensionless. He adds, no wonder Bruce is chief scientist. Actually, a lot of people came up with 4.04 if you do it strictly metric, but come on. It's a round off error. Someone rounded off. Probably going from inches to meters, because indeed, it should be the same, and it is dimensionless.

If you use meters, you get meters over meters. If you use inches, you get inches over inches. And of course, we have hexagons over hexagons. And so everything ends up dimensionless, and you should end up with the same answer one way or the other. Makes perfect sense to me. I got one more thing to read. It's from Gene Lewin in Washington. Numbers and inches are here both combined, divided, then added. Operational order assigned, or is it meters that we are to use? Did Dr. Betts pose this query to see what we choose? So two answers are given within this quatrain.

A shout out to Mel Powell. I can feel your pain. So four is the answer if you use the first sum or 4.04 for the second one. A lot of rounding errors out there. Yep. And a lot of people apparently finding me to be evil, which kind of makes me want to be more evil. But I'm not this week. but I'll think about it.

Don't encourage him, folks. But I will encourage you to provide us with a new contest. This one's to show that I'm a classy, classy dude, because that's what classy people call themselves, is classy, classy dudes. Here's your question. What moon is named after a character from Shakespeare's King Lear? Go to planetary.org slash radio contest.

You have until February 2nd. That's Wednesday, February 2nd at 8 a.m. Pacific time. And here's a prize that doesn't come up much anymore. It's a Planetary Radio t-shirt from our friends at Chop Shop. ChopShopStore.com is where you will find the entire Planetary Society merchandise collection, including that really lovely t-shirt. And with that, I believe we're done. All right, everybody, go out there, look up at the night sky, and think about what soft, what light upon yonder planet breaks.

Thank you, and good night. It is the Chief Scientist, and Bruce is the son, who joins us every week here for What's Up. I am Big Pentameter, dude. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its Snow Angel members, you can become as cool as they are at planetary.org slash join. Mark Hilverda and Jason Davis are associate producers. Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser.

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