Planetary Radio • Jan 26, 2022

Worlds of snow and ice

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On This Episode

Colin meyer

Colin Meyer

Assistant Professor of Engineering and Director of the Meyer Ice Mechanics Group at Dartmouth College

Jacob buffo

Jacob Buffo

Post-doctoral Researcher in the Meyer Ice Mechanics Group, Dartmouth College

Rae headshot

Rae Paoletta

Editorial Director for The Planetary Society

Betts bruce headshot 9980 print

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Kaplan mat headshot 0114a print

Mat Kaplan

Planetary Radio Host and Producer for The Planetary Society

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.

Color view of the plumes of Enceladus
Color view of the plumes of Enceladus A true-color view of Enceladus' southern plumes.Image: NASA / JPL-Caltech / SSI / Kevin M. Gill
Infrared views of Saturn's Moon Enceladus
Infrared views of Saturn's Moon Enceladus These views of Saturn's moon Enceladus were created using infrared data collected by NASA's Cassini spacecraft during its 13-year mission at Saturn. The red regions correspond to warmer surface temperatures. The bottom-right image shows Enceladus' south pole, where subsurface ocean water vents into space. These warmer regions could indicate hotspots on the ocean floor, along with conditions favorable for life as we know it.Image: NASA/JPL-Caltech/University of Arizona/LPG/CNRS/University of Nantes/Space Science Institute
Closeup on Enceladan vents
Closeup on Enceladan vents Cassini captured the images for this 4-frame mosaic on Enceladus' south polar tiger stripes during its 21 November 2009 close flyby.Image: NASA / JPL-Caltech / SSI / mosaic by Glen Nagle

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What moon in our solar system is named after a character in Shakespeare’s King Lear?

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What planets in our solar system have higher “surface” gravity than Earth? For the giant planets that don’t have an actual surface, use the gravity at the one bar pressure level.

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Question from the Jan. 12, 2022 space trivia contest:

What is the sum of the number of hexagons of one Keck 10-meter telescope primary mirror divided by the number of JWST hexagons plus the Palomar Hale telescope primary mirror diameter divided by the Mount Wilson Hooker telescope diameter? Use standard mathematical order of operations.

Answer:

Four. That’s the sum of the number of hexagons of one Keck 10-meter telescope primary mirror divided by the number of JWST hexagons plus the Palomar Hale telescope primary mirror diameter divided by the Mount Wilson Hooker telescope diameter, derived using standard mathematical order of operations. Phew.

Transcript

Mat Kaplan: Weird worlds of ice and snow, this week on Planetary Radio. Welcome. I'm Mat Kaplan, 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, 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 the thick ice and the plumes that shoot far into space from those so-called tiger stripes out the South Pole. It's entirely possible that these guys 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.

Mat Kaplan: My colleague Rae Paoletta 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 down link. 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.

Mat Kaplan: We also learned about an exoplanet discovered by a team of citizen scientists using data from tests, 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/downlink. Rae Paoletta is the editor for The Planetary Society. She recently joined me from her home in New York. Rae, welcome back to the show. Got any snow outside your window there?

Rae Paoletta: It's melted now. But the few times I've taken my dog out in the last 24 hours we've been getting some sprinkle, some dusting for sure.

Mat Kaplan: 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. 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.

Rae Paoletta: Yeah. I'm thinking that maybe the heavy metal snow on Venus might not be the best place to go skiing.

Mat Kaplan: 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.

Rae Paoletta: From the snow canoe if we want to keep the rhyme up too.

Mat Kaplan: Yeah. I'm thinking also of IO. I didn't really expect to read about snow there.

Rae Paoletta: 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.

Mat Kaplan: 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.

Rae Paoletta: It's cool because it is 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 at what could be causing this 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 led 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.

Mat Kaplan: One more stop, Enceladus. You talk to another friend of the show. I mean, you talked to Tony 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.

Rae Paoletta: 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 "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 wintery vibes all around.

Mat Kaplan: There's more that makes this special, it's the whole look of the piece, which is like nothing that I've seen anyway, that we've done on our website. And it includes, well, you talk about these great little animated gifts.

Rae Paoletta: 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 gifty 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.

Mat Kaplan: They are really, really fun. We'll put the link up to our gifty site as well. Rae, great piece and thanks for coming back on the show to talk about making snow all over the solar system.

Rae Paoletta: Let it snow. Always a pleasure. Thanks Mat.

Mat Kaplan: That's my colleague, Rae Paoletta, editor for The Planetary Society. I won't lie hearing that the plumes shooting space word 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 maybe 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.

Mat Kaplan: Professor Colin Meyer and post-doctoral 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. 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.

Colin Meyer: Thank you so much. Really glad to be here.

Jacob Buffo: Yeah. Thank you for having us.

Mat Kaplan: 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.

Colin Meyer: Yeah. So after that observation, two ideas were proposed. One of the ideas was this Herford idea that the cracks went all the way through route to the ocean. That was exciting because at the time it wasn't clear whether there was an ocean on Enceladus. So 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 reservoir. So 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 18s, people were still drawing maps of having a regional ocean underneath the South Pole. But so this Herford idea that the cracks went all the way through the shell and that it was accessing 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.

Colin Meyer: The other idea was proposed by Francis Nimmo and collaborators. And this was a sheer heating idea. This was building off some of Francis's work which said that on these tiger stripes, there was actually heat that was generated as 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 heat through palms. That was a very exciting idea about what would be the source of this heat anomaly. There's a lot of heat coming out of these tiger stripes. This idea that the shear heating was causing caught a lot of attention in around 2007.

Mat Kaplan: 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 say. I mean, it's a big deal, right, if they're not coming from the ocean. 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?

Colin Meyer: 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 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 year heating because we know that they're 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 is the core of the result, is that even in the shear heating regimes, we could still produce geyser material.

Mat Kaplan: 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.

Jacob Buffo: 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.

Mat Kaplan: 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 title forces, the same stuff that makes IO over a Jupiter, such a nasty place to visit. Does that also help to explain the salts in the plumes?

Jacob Buffo: Yeah. So I think the important thing about the title force 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 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 round in 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.

Jacob Buffo: 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 flexing and squeezing this ice shell that's full of salts, if you have any regions or something like that, that has a higher content of the salt, that can actually reduce the melting point and provide a localization for the 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.

Colin Meyer: 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 requiring an ocean. The fact that the plume particles have salt in them, we draw a direct link from the plume to the ocean, skipping the shell. And I think that part of the reason and what Jacob and I have been working on for the past couple 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 participating idea.

Mat Kaplan: 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 the same mechanism as salting roads, right?

Jacob Buffo: Yeah, exactly. It's the same reason that you're in a cold place on earth, where you put salt on the roads so that it melt at a lower freezing point that happens in any salty system. Again, our ocean freezes at about negative two degrees celsius as opposed to zero degree 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 localize this salt.

Jacob Buffo: Folks have coined this term called cryovolcanism or cryomagnetism. 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. The salt water will behave in similar ways where it can fraction 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 of about, is 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 volcanism and different geophysical processes occurring on earth.

Mat Kaplan: 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?

Colin Meyer: 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. 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 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.

Colin Meyer: 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 [crosstalk 00:17:42]. And so that's what happens in sea ice.

Colin Meyer: 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 CI systems and the mushy zones that they develop. And so we are leveraging that code developed for this idea of having a mushy zone, a region of partial melting, and we're using it, not an CI system, though sometimes we do analyze those systems as well, but we're using it in a context of Enceladus.

Colin Meyer: I think one of the key ideas, getting back to your question, Mat, is we're starting with an idea. This idea is let's revisit the shear heating model of Francis Nimmo. Let's add salts to it. We put that into this model, this CI developed model soft bowl. And then we want to 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 implications of that.

Mat Kaplan: You mentioned that you've adapted this model that was developed at Oxford. By the way, is this the one called softball?

Colin Meyer: Yeah, this is softball. Exactly. Yeah.

Mat Kaplan: 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.

Colin Meyer: Indeed.

Mat Kaplan: 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.

Colin Meyer: 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 sensitivities in our model to those different things. So how does the model change if we change these parameters? And 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 extract the plume particles that we do it and say, This is the ocean chemistry, then we could say what the ocean chemistry is. Though our results are actually a cautionary tale for that in 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.

Colin Meyer: 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 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. If the volume of ice that can come out of the geysers is 100 times that 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.

Colin Meyer: 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.

Mat Kaplan: So far so good. I mean, is the data matching up with what you thought, what the model told you, you might see?

Colin Meyer: Well, I mean, all of this is preliminary, right? So we haven't published this paper yet. We're still working on it. But yes, those are our basically two targets, is trying to figure out under what parameter regimes do we observe the things that are observed in Cassini. Our preliminary work suggest yes, that we can find perimeter regimes that can match those observations from Cassini.

Mat Kaplan: Jacob, you called this a cautionary tale. Do you remember what you meant by that?

Jacob Buffo: Colin touched on it a bit, as far as things extrapolating the chemistry from the Cassini measurements. We talked about it where that's a small sample of what the plume particles are and what the composition is. But it's that backtracking and linking it one to one is this tricky bit where if you're directly accessing the ocean, there's a chance that that is a more representative chemistry and the plume particles. But if there's this intermediate step, there could be an issue, I think. And for astrobiology, it's the same thing. When we're thinking about, are these oceans habitable, 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 resources in these oceans that would make these oceans habitable? But it's like me trying to guess what's in your kitchen right now, food, [inaudible 00:23:20] or something like that, right?

Jacob Buffo: And 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 maybe have a shopping list of things that somebody has, if you've had these particles erupted through a plume. But if these chemicals have been entrained in ice shell and then processed, and concentrated, and melted, and refrozen, it's like finding that shopping list after it's gone through the washing machine or something. You just have these little pieces and you're trying to figure out now what's in this kitchen and what's usable. Is this a good representation of what's actually down under the surface? So we need to be cautious, I guess, in understanding that there might have been a lot of processes and revamping and maybe only a small amount of this information from down deep actually got trapped in these particles that we're measuring. So that was my thinking for the cautionary tail quote.

Mat Kaplan: 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?

Colin Meyer: 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. 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. If we go to Enceladus or other lines of prove that this theory is completely wrong, I mean, that's flattery of the greatest degree, right?

Mat Kaplan: Yeah.

Colin Meyer: I'm excited to learn how it works. I'm just thrilled to participate in it.

Mat Kaplan: Mars, Pluto and Mar are just ahead when we rejoin Colin Meyer and Jacob Buffo in moments here on Planetary Radio.

Casey Dreier: Hi, again, it's Casey Dreier, 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. If you've heard us talk about how effective and just personally rewarding our days of action have been, this event is for you. Learn how to participate in this virtual online experience by visiting planetary.org/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 US, you can and still make your voice heard on March 8th. It all starts at planetary.org/dayofaction. Join us as we speak out for space.

Mat Kaplan: 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 or institutions involved, but I also saw that your colleague there at Dartmouth, Tara, is it Tara or Tera Tomlinson, also contributed to the work.

Colin Meyer: Yeah. Tara, 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 solidified. 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 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.

Colin Meyer: And so Tara's doing great work trying to understand 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, trying to understand the glaciers on Pluto, how you might have subglacial systems of hydrology moving along the glacier systems on Pluto. But it's no longer water ice. We'd actually be considering the nitrogen ice. They might have analogs too, glaciers here on earth and having similar systems.

Mat Kaplan: Very cool. Again, no pun into ended. 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?

Jacob Buffo: That is a million dollar question, I think, at least, right. And hopefully, as these missions go out and collect more data, we'll get close to that. But I think our 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 all 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.

Jacob Buffo: So the same way that we took this computer model from the physics that govern CIS 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 anywhere with water is still a good place to look.

Colin Meyer: Definitely. And I think an important point that's underlying what Jacob's saying is that the model that we wrote down isn't very Enceladus specific, that we put in the Enceladus parameters, 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 this shear heating mechanism. And so 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 could be very exciting.

Mat Kaplan: I think our audience is probably tired of hearing say nothing to Jeff Goldblum, but 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, A, the place to look for life is under the surface. But most people, I think were 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?

Jacob Buffo: I think this is probably in relation to some work that I had done with [inaudible 00:31:27] 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 come up this 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. 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 have, how thick these ice sheets would need to be to get this melting at the base.

Jacob Buffo: Because 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. 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 there's still full of life bacterial and stuff like that. That was the goal of that study. And we used some historical predictions of how much ice and water could have at one point been on Mars to basically predict how thick these ice sheets could get and 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 cycle.

Mat Kaplan: 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?

Jacob Buffo: Yeah. There's some great groups now that are looking at the present ground ice on Mars. So even though right now we just 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 in the ground. So think about more like permafrost on earth. This is actually down deep beneath the 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 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 Mars loses its atmosphere and then starts and 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.

Mat Kaplan: It's what I would do. How far down are we talking about? Are we talking meters, kilometers?

Jacob Buffo: 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 a heterogeneous thickness throughout. So they are using radar as, I think the primary method to measure the location and 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 triple way at.

Colin Meyer: And permafrost on earth, you can find kilometer thick permafrost on earth.

Mat Kaplan: 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 model are telling us more about our own planet.

Colin Meyer: 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 these systems, whether they arise on Enceladus or on earth or another planet. And see what's translatable and what are some new directions that we can push. Tara's work that we're excited about in permeability, that has applications to sea ice on earth, but also has applications to the 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 melt water flows under glaciers. We have collaborator in our group, Alia Summer, 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.

Colin Meyer: 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 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.

Colin Meyer: On the planetary scale, there's a little bit, I would say, lower urgency and it's driven by this question of curiosity around finding general habitable places. But that's really exciting and fun and great to think about. And so I think it's cool to leverage both sides to think about things that are urgent here on earth, as well as things that are cosmic in many ways and driven by curiosity. What are your thoughts, Jacob?

Jacob Buffo: Yeah. I mean, I think one of the special things about this work and our work has really been that we came from different backgrounds. You have more of like an earth glacier theology background, and I come from 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. 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 are 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 question.

Mat Kaplan: 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?

Colin Meyer: Well, there's about a foot of snow on the ground and it's cold. It's a little icy, but, it's a beautiful sunny day.

Mat Kaplan: 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. Tell Tara that we're sorry we missed her, but maybe another time when we talk about her work on Pluto. Thanks guys.

Colin Meyer: Thank you so much, man.

Jacob Buffo: Yeah. Thanks so much for having us. This is great.

Mat Kaplan: Time for What's Up on Planetary Radio. We are back with the chief scientist of The Planetary Society who is you 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 Marley in Washington who appreciated your pop culture reference last week. "It was an origami reference that appropriately sailed right over my head." He reminded me that it was from Airplane, the movie.

Bruce Betts: Yes. I don't even remember what I was referring to, but yes, you can make a broach or [inaudible 00:39:30]. Yeah. Anyway. Yes.

Mat Kaplan: Moving on. What up?

Bruce Betts: Low evening west, Jupiter, going away in a few weeks, still hanging out there. And in the pretty down 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 to 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 serious, the brightest star in the sky, night sky. And the other direction you get at least really close to the [inaudible 00:40:16]. So have fun.

Mat Kaplan: You know what else I noticed up there? [inaudible 00:40:21], not far from Orion. Orion is just, that's my favorite constellation. There is no question.

Bruce Betts: Yeah. [inaudible 00:40:28] up there in Gemini. And then also the whole winter hexagon, which is six bright stars that form a hexagon because they're six and they're evenly spaced. Anyway, look it up or buy someone's brilliant book that talks about it.

Mat Kaplan: Okay. And there'll be more hexagons coming up later in the segment.

Bruce Betts: It's a hexagonal theme show. But onto this weekend in space history, it is sad week or more positively space heroes week. Every fatality in a spacecraft in the US 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 us satellite.

Mat Kaplan: A big week in US space history, no matter how you look at it. Yeah. We salute those heroes as we do every year.

Bruce Betts: Onto random [inaudible 00:41:43].

Mat Kaplan: Oh, I like that at the end.

Bruce Betts: You probably heard of Enceladus. I'm guessing you heard a lot about it, just a little bit ago.

Mat Kaplan: Yeah, just in the last half hour or 45 minutes.

Bruce Betts: But have you ever wondered how much bigger is Titan than Enceladus? Have you wondered that, Mat?

Mat Kaplan: Yes. The answer is a lot.

Bruce Betts: All right. Well that's my random space pack for the week. No, I've gotten more. Over 1000 Enceladuses could fit inside Titan if you squished them up and got rid of the fore space.

Mat Kaplan: Wow.

Bruce Betts: Titan's a lot bigger than all the other moons of Saturn.

Mat Kaplan: And no wonder people thought that Enceladus was too small to have an ocean in inside. Surprise.

Bruce Betts: 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, 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, Mat?

Mat Kaplan: I was surprised to see how many of you out there loved this and want more mathematically based questions from Bruce.

Bruce Betts: Wow.

Mat Kaplan: Isn't that something? I will start with this response from our poet laureate, Dave Fairchild in Kansas. "Start out with the hex of [inaudible 00:43:28]. It's 36. You know. 18 is the hex for web. Lagrangian, we shall go. Then take 200 inches for the Pyrex Palomar and finally 100 for the Hooker seen 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?"

Bruce Betts: 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.

Mat Kaplan: That's such a relief. And here's a surprising answer as well. Why surprising? Because I check 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 a random choice. Well, Mel, it finally happened.

Bruce Betts: Congratulations.

Mat Kaplan: It's my revenge for the toy with emotions wise crack that came from you last week, Bruce. We'll find Dr. Betts. The gloves are off. Here's the answer.

Bruce Betts: Man.

Mat Kaplan: "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 GPS 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, harrumph." Well, Mel you're right. Except that if I follow your formula correctly, I came up with 4.5, which would round up to five, of course. But at the bottom you did say four. So I think we have our winner, Bruce.

Bruce Betts: Well, I guess no matter what happened with the equation, we have our winner thanks to you and random.org. So congratulations, Mel. [inaudible 00:45:44] have heard about calling me evil, but it's balanced by the best use of harrumph I've heard in a long time.

Mat Kaplan: Yeah, boy, it wasn't just your everyday harrumph. Was it? Mel, you have won yourself that beautiful STARtorialist neck tie. 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 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... I put on a nice shirt just so I could wear a tie for you.

Bruce Betts: Dude, it is so cool looking.

Mat Kaplan: 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."

Bruce Betts: Well, I will take them to task. You go ahead, then I will take them to task.

Mat Kaplan: 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 Lusky in California, "I was hoping the answer 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.

Bruce Betts: Usually you have heard the single word dimensionless.

Mat Kaplan: 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.

Bruce Betts: It's a round off here. Someone rounded off probably going from inches to meters because indeed it should be the same and it is dimensionless. But 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.

Mat Kaplan: Makes perfect sense to me. I got one more thing to read. It's from Jen 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 use the first sum or 4.04 for the second one." A lot of rounding errors out there.

Bruce Betts: Yeah. And a lot of people are apparently finding me to be evil, which makes me want to be more evil. But I'm not this week. But I'll think about it.

Mat Kaplan: Don't encourage him folks. But I will encourage you to provide us with a new contest.

Bruce Betts: This one's the show that I'm a classy, classy dude because that's what classy people call themselves as classy, classy dudes. Here's your question. What moon is named after a character from Shakespeare's king Lear? Go to planetary.org/radiocontest.

Mat Kaplan: You have until February 2nd. That's Wednesday, February 2nd at 8:00 AM 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. At 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.

Bruce Betts: All right, everybody go out there, look up the night sky and think about [inaudible 00:50:04], what light upon the under planet breaks. Thank you and goodnight.

Mat Kaplan: It is the chief scientist and Bruce is the son who joins us every week here for What's Up.

Bruce Betts: [inaudible 00:50:15].

Mat Kaplan: 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/join. Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is ranged and performed by Pieter Schlosser. Ad astra.