The Burning Mountains of Io, Part 2

of what we talked about last time. We started off talking about how I got interested in revisiting Io because we did do a series of episodes on Jupiter's moons at large several years back, but I wanted to come back and do a closer pass on Io, in particular because I got visually obsessed with some images produced by the NASA Juno mission in the past year or so. Guess it's actually little bit over a year because some of the data that we were looking at was collected

in late twenty twenty three. But we talked about several of these images in detail, about the strangely polychrome surface of the Moon and its truly fascinating surface features, including gigantic blade like mountains, vast sulfurous plains, hundreds of erupting volcanoes, enormous hellish lava lakes rippling with lava waves, and lava flows stretching hundreds of kilometers, all situated within a land

that is at once burning hot and freezing cold. So it is, as Bart Simpson might say, a land of contrasts, but also just a place of enormous physical and sort of geological drama. We also talked a little bit about the history of the exploration of Io, at least going back to Carl Sagan's account of the discoveries made by

the Voyager Probe in nineteen seventy nine. Around then talked about the extremely thin sulfur dioxide atmosphere of Io, which is generated initially by venting from the Moon's volcanoes and subsequently by the cyclical freezing and sublimation of sulfur dioxide frost on the surface, freezing when the Moon passes into Jupiter's shadow, then transitioning into gas again once back in

the sunlight. We also talked a good bit about the Greek myth of the Moon's namesake, sort of the themes of the Io story, especially in Ovid's telling and other versions of the story, and the way the tale was said in ancient times to interlock with Egyptian religious figures such as the goddess Isis, Shepherd of the dead, and the Sacred Mother of Pharaoh's And we are back today to talk once again about Io.

which it featured in stories I knew. I think it showed up at some point briefly in the Expanse, and I can't really think of many other examples.

think maybe it only partially factored in there. And I think one of the possibilities here is that i Owe is a moon that we know to be rather extreme and hostile, for even our sci fi visions and fantasies tend to give it a little safe distance.

horrible place to work. It's the horrible working conditions and there's a lot of like labor dispute in this particular sci fi vision, you know, eighty one, that's not too long after Ridley Scott's a and it's a film that you could almost assume to be in the same universe, you know. It's that sort of very gritty, essentially near future vision of science fiction that is very much focused on like the working man in space.

I've seen people talk about this online almost in terms of like a lost classic, Like it's apparently hard to get your hands on, but it's got some very impressive line work and just some really beautiful imagery. I mean, like I say that the film itself has a very gritty air to it, and that flavor is still present in the comic book apparently, but it also has this like extra like wilder vibe going on.

it's the perfect setting for that. Now I had to hunt around a little bit more defined examples of Io being used as a setting in other sci fi visions. There's a nineteen ninety four mini series titled Escape from Jupiter that concerns an escape from Io. Apparently it's an Australian kids adventure and it's also has Steve Bisley in it, who's in a number of I think it was in at least one of the Mad Max films.

it's one. It was released on Netflix. I have to say, in the one still I found from or a production image promotionary image, doesn't look very pizza in the background.

human colony. I haven't read that one, but I did read a story he wrote titled The Planet of Doubt, which I did a Monster Fact episode back in twenty twenty three, So I'm going to make sure that I re air that one either this week or the following week so you don't have to go look it up again.

But it's a pretty fun one. This guy had a real, real creative mind for dreaming up alien creatures that you know, often reflected some of the stranger biological examples we have on our own planet, but with you know, a nineteen thirties or slightly later sci fi spin.

concerns a possibly sentient IO. It was adapted into an episode of Love, Death and Robots on Netflix again, Netflix loves Io with the main character voice by McKinsey Davis, who's been in things like Halden Catch Fire and I believe the more recent Blade Runner of film.

one of those, the mystery dunes of Io. So Rob to start off with, I'm gonna have you look at two images side by side in our outline here, and folks at home, we will describe them for you so you understand what we're looking at. On the right, we have a satellite image. This is taken from above the Namib Desert, which is on the west facing Atlantic coast of Southern Africa, and that desert covers parts of the

coastal region of Angola, South Africa, and primarily Namibia. Now, looking down at this desert from an orbital perspective, we can see a beautiful, almost hypnotic pattern repeating across the sandy expanse. Those are dunes, and sand dunes are characteristic of many, but certainly not all, desert environments on Earth. Some desert environments are very rocky, others are very cold, places you might find ice fields, and then other desert environments are the places you would find vast expanses of

sand dunes. Sand Dunes on Earth are formed primarily by what are called Eolian forces, meaning they're created by the action of wind, and actually the influence of wind comes in at multiple stages because if you go way back to the point of of the sand, wind along with water, plays a role in the weathering and the transportation of rocks.

So you start off with rocks. You might have rocks in the mountains or something, and they are broken up by weathering, they get rained on, or they get the wind blows on them, and various forces break those rocks up into smaller pieces which can then be transported by water and by wind downhill into places where they collect, and over time those pieces of rock are continually broken down into smaller and smaller pieces by further weathering and

erosion and transport, and the smallest sizes of mineral grains. You might remember this if you listen to our series on dust, are known as from larger to smaller are

known as sand, silt, and then clay. Sand Dunes are created in areas where sand collects, So after the rocks are weathered and eroded and then the sand is broken down in transport, it'll sort of end up in some kind of catching place, a depression, usually a lower lying area, And when the wind blows it can move sand particles along with it, And this is something yet again we talked about in our series on dust. The term for the process by which sand is moved around by the

wind is known as saltation. So you can get different ways that the wind interacts with sediments and rock pieces of different sizes. So you know, a larger rock, the wind blows against it, it's not going anywhere. Maybe a pebble the wind blows against it, it might kind of move it a little bit, or a pebble might get blown off another a pile of other pebbles and kind of tumble a little bit, but it doesn't really go

much of anywhere unless you get really high winds. And then meanwhile, if you go all the way down to the sort of the dust size of grains of sediment, the wind can pick it up and carry it up into the atmosphere and then the dust just you know, it is borne a lot for a long long time. It can travel anywhere. It can travel across the land, across the ocean, end up in different places. But sand is in this middle zone where it's subject primarily to

the forces known as saltation. When wind blows on sand, the sand will be blown along the surface of the ground, or will follow the surface of whatever sort of the base layer of the earth is, and it will will be kicked up, and it'll kind of jump and bounce and then come back down and hit the sand, and that will cause other pieces of sand to kind of get knocked out of place when the initial piece of sand lands, So it creates this kind of bouncing, jumping,

hopping motion as sand is blown along by the wind, As sand gets blown along by the wind, as saltation is going on. At some point the flow of wind

driven sand can become obstructed. Maybe it gets caught on an obstacle like there's a bush, or maybe it falls behind an obstacle like a bush or piece of vegetation, and then the wind cannot exert as much of a force on it anymore, so it just kind of like sits there and grains can pile up, or maybe it gets blown against the side of a slightly elevated pile of other grains of sand and it gets stuck there instead of moving on and from here, these places where

sand starts to collect can be a self reinforcing process, where a mound of sand just gets bigger and bigger as the wind forces blowing sand particles against it cause the particles to collect around this mound in one way

or another. So a common format of sand dune that you will get in places, especially where the dominant winds are blowing primarily in one direction, is that the side of the sand dune facing the wind will be a smoother, slower, more gradual slope, and then the side of the sand dune facing away from the dominant winds will be a

much steeper, sharper slope. And what's usually happening is the wind is blowing sand along and it's eroding sand from the middle of the rising slope on the windward side, and then trying to deposit it right at the crest, right at the peak of the dune. And in this way, over years and years, more and more sand accumulates. But sand dunes don't just grow higher and higher forever. Eventually a sand dune will collapse, not totally disappearing, but losing height.

And this happens when one side of the dune becomes too steep, exceeding what is called the angle of repose. Now, this is a kind of cool physics principle. I think we may have talked about this on the show before, but the angle of repose is the steepest angle that a pile of sediment or whatever other granular substance can

attain before it collapses under its own weight. In fact, I wonder if we talked about the angle of repose in when we were talking about the ant lion, because I believe that is a factor in the construction of their conical traps. That you know, they make them so just so that they're sort of right on the edge, and it's easy for the sides to start collapsing and pull an ant down if they fall in.

National Park in Colorado. The angle of repose for sand is usually between thirty and thirty four degrees, so once it gets steeper than that, the dune will collapse. And this, in part explains why when you're looking at pictures of sand dunes in the desert, you will, as I said, often see them with this one smooth side, kind of a gentler slope on one side ascending at a shallower angle, and then the other side will fall off at a steeper angle with an almost kind of sheared off texture.

the shelter from the wind on the leeward side. And sand dunes are really interesting, you know, you can if you watch them over long periods of time, they can start to seem less like the geological formations we're used to. I mean, we know that mountains move over time, but you know, it's really hard to imagine how mountains move. You really have to just sort of think outside of the human timescale. Dunes are kind of somewhere in between

mountains and the waves in the ocean. Over periods of you know, months or years, dunes will will creep across the surface of the Earth. So that's dunes on Earth. However, Rob I want to come back and have you look at the photos we started with, So the one we were looking at first is sand dunes on Earth. But then the photo I've got for you here on the

left is a photo of Io. So what we see on the lower left hand side of the image is a kind of dark spreading expanse that has a sort of creepy organic outline, kind of like if you zoom way out, like a flood pouring through topography. And researchers think that this area in the photo of Io is probably one of those relatively fresh lava flows that we

talked about last time. You know, a lot of the surface of Io is affected by lava flows, and that they can be huge, enormous, hundreds of kilometers of just lava flows. And this helps contribute, of course to what Carl Sagan said about the moon right. He said that Io is a place of relatively rapid change by planetary standards. Major changes to the surface of Io can occur on

a timescale of months. But if you look at the other side of this image from Galileo, not the dark side, but the lighter colored side, we see not lava flows, but these pale reflective ripples thousands of them arrayed in a repeating pattern, kind of like what you would see in like when you can see a standing wave of emerging in a fluid, or you know, if you like a rattle, you like rattle a speaker, and then on top of it there's some sand. You get these emerging things.

One thing I wanted to compare it to was like a silver reptile skin. It has almost kind of a pebbly lizard texture.

few other trace constituents. And for a comparison of how thin Io's atmosphere is, I was looking for, you know, what's the difference between Earth's atmosphere and iOS And I actually found a twenty twenty press release from the National Science Foundation that addressed this. They crunch the numbers and they say that i Io's atmosphere is roughly a billion times thinner than Earth's It is barely an atmosphere at all, thicker than the even more tenuous exosphere of Earth's moon,

which I was looking that up. Also, apparently Earth's moon has such a thin layer of gas that there are only about one hundred molecules of gas per cubic centimeter near its surface. So iOS is thicker than that, but still not thick enough to cause irrosive wind patterns like we have on Earth. So if there's not enough of an atmosphere to sustain significant winds on Io, and if dunes are generally created by Eolien forces by wind, what's making the dunes or are they actually dunes at all?

So just a couple of years ago, there was a paper that actually addressed this question. It was published in Nature Communications by MacDonald at All and the title is this will answer some of the questions Eolian sediment transport on IO from lava frost interactions and for context. I was also reading about this in a Rutgers University press release by Kiddy Macpheerson from April twenty twenty two that

had some quotes from the authors. So, first of all, to answer the question, are these dunes previous researchers had noted that the features which are generally turned termed ridges in the astronomy context or the planetary science context. These features that they had been noticed for their similarity to eli and sand dunes on planets like Earth and Mars. Mars has dunes as well, But these previous investigations usually argued, no, these are probably not dunes formed by wind. For the

reasons that we've already raised. The atmosphere of Io is not thick enough to really have wind. It's not thick enough to lift sediment and move it around. And again, this moving around of sediment by s particles by wind would be saltation. So remember that when it comes up in these quotes. The authors of the paperwright quote choosing

zero point one nanobars as a representative atmospheric pressure. One study estimated a twenty kilometer per second threshold friction speed to move grains on Io, two orders of magnitude greater than Io's roughly three hundred meters per second wins, concluding that an Eolian origin for these features was impossible. Formation by tidal forces was favored. Now, tidal forces means the interaction of different gravitational forces on matter exerting a pulling

or a stretching force. So this alternate explanation previously favored because Io can't sustain wins, is that there's something about the gravity that is causing these ridge features to emerge. However, despite agreeing that saltation is not possible under the ambient atmospheric conditions of Io, the authors note that there really are a number of similarities between the features seen in

these images and Eolian dunes. They mentioned quote the ridges, regular spacing, slightly meandering forms, and possession of crestline defects. So these are all features that are very similar, so similar to wind formed dunes on Earth and Mars that it would be kind of strange if that's not what they were. So is there any way that these features could have been formed by something like wind, even though

you know, even given the limitations we know of Io's atmosphere. Well, the authors of the paper note that the thickness of Io's atmosphere is not consistent across its surface, so the density of surface gas could actually be much higher at certain times and in certain areas, specifically in the vicinity of volcanic vents, which are rapidly viewing so two gas

as they erupt. The authors ask, what if there is a sort of you could say, quote unquote wind that is present locally, not globally, on the surface of Io, consisting of some kind of rush of gases from subsurface interactions from volcanism or from downstream effects of volcanic eruptions, And what if this is responsible for crafting the dunes?

And this is in fact what they find support for in their paper and the author's write quote here we demonstrate that interactions between lava from volcanic eruptions and the sulfur dioxide frost blanketing Io's surface can produce localized sublimation vapor flows with sufficient gas densities to enable saltation. So I thought that was really interesting. So what would these interactions be. To be clear, they're not talking about their quote unquote wind being the gases that burst directly from

volcanic eruptions. You know, it's not like the gas comes out of the volcano and that is the wind. They're talking instead about a secondary mechanism that they find probable, which is that you have hot lava flowing just underneath the surface of the frost layer here, and it's creating this interaction with the sulfur dioxide frost on the surface, causing the sulfur dioxide to sublimate. Essentially, it heats it

up and it causes an outgasing process. So suddenly a bunch of this SO two turns into gas and then they find that that would be capable of driving saltation. So lead author George MacDonald, quoted in the press release, says, our studies point to the possibility of Io as a new dune world. We have proposed and quantitatively tested a mechanism by which sand grains can move and in turn

dunes could be forming there. And I really they actually come through in the in the press release there the authors are like referencing the book Dune and talking about how it could be like a racket. So I like the dedication to like we have we have determined how it can be a dune world.

but instead you see dunes facing different directions. But another thing is that if this really is the mechanism, you might expect to see more dunes forming, like around the edges offs like we see in this image we started with, where you've got this black glassy area on one part of the image. You know, that's where the lava is flowing, and then at the edge of that it's probably interacting with these these planes of so two frost, and that could be creating the winds that blow that blow over

the surface and help form the dunes. Interesting, So I feel like sci fi writers, we're just feeding you, We're just you know, like you can you can do a dune type thing on io that'll work here.

the rest of them. It's kind of like looking at the I don't know Batman's rogue gallery and saying, well, which one is the like the least awful, And you might be like, well, mister Freeze has some you know, some virtues to him, yes, but he's still a murderous madman. Killer.

just got to move on to the next thing. I don't I don't think that's a good basket to put your chickens in.

in your you know, sci fi visions. You know, it's like you have to really look at far future scenarios where it would even become possibly feasible for there to be truly independent colonies, independent systems that are not depending on this place where we evolve to thrive. Yeah.

I keep coming back to that idea. Our earth is this incredible pearl, and because it is the place where there is life, it is the place where we are meant to be. And you know, we may expand out and explore these other places, we may expand out and make new homes on these other places, but this, this is the place from which we arose. This is our true home. This is the only place we can count on to sustain us as long as we cherish it.

the Earth is. But it is also essentially a mineral product at its material base, which most of the Earth is, but also a biofact. You know, a pearl is created by life, and the way the Earth is now it was also in a way created by life. Life is defined what the planet is down to its very physical substance.

most plausible here? And I know you'd been reading a bit about io and life, so once you turn up.

it can survive in very hostile conditions. So it's not completely out of the question that something could evolve, either evolve within those hostile conditions on another world, or survive in such conditions, you know, after the loss of a previous habitat. And so I was looking around in one individual in particular that has speculated a fair amount concerning IO is German astrobiologist Dirk Schultz Makouch speculated in twenty

twenty three on Big Think about the possibility. The title of the Big Think article that he crafted is there could be life on hot volcanic Io. Jupiter's quote pizza met.

is more is more general audience. But but he goes through, you know, all the major points that he hits in some of these other articles, and he drives home that the Juno mission revealed much more about Io than we previously knew, and that based on these more recent discoveries, you know, it's reasonable to hypothesize that while Io is now this volcanic world of extreme cold and extreme hot temperatures, it may have once had as much liquid water as

Europa and Ganny meat and during those early days, the combination combination of liquid water and geothermal heat again you know, highly volcanic world could have led to the development of life. However, of course, this wouldn't be the case today. Io would have gone on to lose most of the water due to Jupiter's radiation and tidal forces, and this is pretty

much left the surface of Io quite uninhabitable. But what about the underground, Well, Schulzmakouch stresses that it might still prove too violent beneath Io's surface for life, Like it's still it's still you know, not the best bat, but you know. He says that there's a chance it could survive there due to the possibibility of remaining abundant water carbon and reduce sulfur compounds. So a dynamic, though possibly

too dynamic environment for life. Maybe not on the surface of Io, but perhaps maybe underneath the surface of the planet, beneath the planet of the pizza if you will.

And he stresses that lava tubes here on Earth, you know, they provide a great example because they are often home to extremophile and microbial life, regardless of the region in which you find them. You know, this is true of lava tubes in the desert as well as in Iceland, in places like that. And on top of that, lava tubes on Mars, according to schulsmaccooch the most plausible place to find life on the Red planet. So lava tubes

in general great place to look for. It seems like lava tubes should be present beneath the surface of Io as well. Now, he also discusses that if there's not enough water for life on Io, it's also feasible that hydrogen sulfide might and in for water, though he stresses that quote suggesting an alternative alternative solvent for life is

always very very speculative. Yeah, So I do want to make sure I'm doing justice to what he has written and said about this, because he's not saying there's definitely life on ioh. He's saying, you know, we have to keep an open mind about these things and discuss how it could exist there based on what we know of life here on Earth.

would be down in these lava tubes. And one of the things that he points out is that, yeah, these we just have to speculate like this, This would be very hard to just to explore one hundred percent for a number of reasons. It's very difficult to figure out how you would like land a craft or a rover on IO and then dig down underneath the surface. It's

a very hostile world. However, there's still plenty of room to explore it from an orbital standpoint, and we can continue to learn more about the surface of Io and the composition of IO, and in doing so we might be able to make even better guesses about what might be beneath the surface. All right, Well, on that note, we're going to close out this episode, but we'll come back with one more episode on Io this Thursday. In

the meantime, definitely feel free to write into us. We'd love to hear from you your thoughts about anything we discussed here. Examples of IO from science fiction. All of that is fair Game will remind you the stuff to blow your mind. Is primarily a science and culture podcast, with core episodes on Tuesdays and Thursdays, short form episodes on Wednesdays and on Fridays. We set aside most serious concerns to just talk about a weird film on Weird

House Cinema. Maybe we'll get to Outland someday. It's been on kind of like the shortlist for a little bit, but maybe maybe someday soon If you would like us to cover Outland on Weird House Cinema, write in and encourage.