What's up with Iapetus?

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Speaker 1: Orne, Hey, do you ever feel like being a parent is a little bit like being a detective? Yikes? What kind of crimes are your kids doing these days? Well, sometimes I walk into my kitchen and it looks like a disaster scene and I had to try to figure out, like what happened here? Oh, man, they had some big spaghetti parties or something. Yes, spaghetti sauce on the ceiling. Well, it sounds like you have to use your noodle to solve that saucy mystery. Hi, am or hand. My cartoonists and the co author frequently asked questions about the universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and my kitchen is often used as a chemistry laugh. Oh yeah, it makes dangerous chemicals or delicious chemicals, dangerous and experimental recipes, mostly by my daughter. Last week, I went to the kitchen and she was making boba from scratch. Oh, we've done that. It's pretty fun. Yeah, it's pretty fun. Not that dangerous, though. You make it sounds like you're making a you know, a breaking bad situation in your kitchen. Well, I didn't eat any of this boba because, you know, who knows what really went into it, but I did get to clean up after it, so that was fun. Yeah, it's the privilege of being a part I guess we're just the clean up crew and the finance ears at the same time. Somehow that doesn't make sense. Welcome to our podcast Daniel and Jorge Explained the Universe, a production of I Heart Radio, in which we act like the clean up crew for the universe. It's out there creating incredible mysteries and cosmic connections, slashing around and buzzing particles and throwing things in the black holes, but it's not always doing a great job of explaining itself. So we step in. We asked the big questions, We try to give as many answers as we in, and we embrace the eternal mysteries that is, the remaining vast unknown about the universe. Yes, because it is a pretty messy universe, full of amazing and sometimes can explicable phenomenon that no one is going to clean up apparently, if not for physicists and scientists. Yeah, that's exactly our job. We can't always organize the universe, but at least we can try to figure out why it ended up in this messy state that it's in. And when we see something we don't understand, you might think we get frustrated and confused, But actually those are the most glorious moments when you find a clue that tells you that the story you've been telling about the universe is not complete and you have an in road to figure out the true story. Well, I've seen your desktop, Daniel. I'm not sure I would trust you to clean anything up. It's pretty messy. It's part of the process. Man. The spaghetti stains and you're ceiling too. There's no boba making allowed in my office, at least for kids, because then they would know how messy you are now. Actually, all the chalkboards that I have in my office are cover in my kids scribbles, which is wonderful, but I hate erasing them, which means most of my chalkboards are no longer useful to me. Are there any good physics ideas in there? Have they done your job for you yet? I'm not done training them up yet to be grad students. Oh boy, I'm sure that they're looking forward to being their dad's grad students. That should be fun. No, neither of them look like they're heading into the science direction, but I wish them the best. Well, there are incredible mysteries out there are some of them pretty messy, some of them pretty neat. I think the universe it's a broad range of cleanliness and its phenomena, and we're here to explain all of them too. And you might think that most of the mysteries are deep out in space, at the heart of black holes, or only visible to particle physicists able to smash open the tiniest bits of matter. But there are a lot of mysteries that are sort of at our size, things the size of the Moon or the Earth. Things in our backyard that we still do not understand, things that are covered in clues left by a really interesting sequence of events that we get to unravel. It's right, there are big mysteries right here in our solar system. So to be on the podcast, we'll be asking the question what happened to yepid is? First of all, what is yepid is? And is that the correct way to pronounce it? According to my Internet googling, that is the correct pronunciation of this solar system body, which originally comes from the Greek I see and if it's on the Internet, it must be true exactly. I also found people from New Jersey who pronounced the epidis, but I think we should go with the Greek version. Are you sure they're talking about a celestial body and not not you? I was googling on campus and I thought this is probably danger zone, so I just stopped right there. And the whole Internet is a danger zone. But yeah, this is an interesting body in our olar system, one that we don't quite understand how it got to be the way it is exactly. And everything that's out there in our solar system tells a story. It tells us a story because of what it's made out of. It tells us a story because of what it looks like, and it tells us a story because of how it moves. You know, physics is a set of laws that governs how things evolve, and so if something is doing something weird or looking weird, there's a reason. There's a clue. It's like if you meet some person and they have a scar on their arm, you know that there's probably an interesting story there, and if you know them well enough to you might ask them about it. And so everything in the solar system is also covered in scars and comes with an interesting story. Yeah, maybe they were making boba in their kitchen and had a boba accident and their dad got really mad. And something that we've learned over the last few decades is how many interesting stories there are in our solar system. You probably have a picture in your mind of the Sun with the planets moving around it in a very orderly fashion and not changing, right, that this is the way the Solar system is and probably always has been. But as we look deeper into the Solar system and study with more detail, we discover that there's a lot of really interesting and chaotic history there. It's more like the mountains on Earth that changed slowly on our time scale, but very rapidly on geological time scales. Yeah, the story of how the Solar system form is not just a big story. It's also an important story, right, because it tells us kind of where we came from and how we came to be here, and also maybe what are the chances that life could develop in other places in the universe? Exactly is our solar system weird? What kind of strange early cataclysms do solar systems have to survive in order to produce life bearing planets. We know from our own solar system that Jupiter probably was formed on the outer Solar System, then moved inwards, and then moved back outwards again, maybe even ejecting an entire planet from the Solar System along the way. Is this a typical kind of thing in our solar system? Fortunately, everything that happens in the Solar system leaves a mark. There's always some evidence of something that happened, and so we can unravel that story by working backwards, and then we can give it fun name like yep it is. Yep, we can. It's a good thing. They didn't call it nupidus. Yeah, that would be more negative name. But as usually, we were wondering how many people had heard of something in our solar system called the yep it is and what is the story with that body? So thanks to everybody who's willing to participate. As usual, if you would like to answer these questions for future versions in the podcast, please don't be shy right to me two questions at Daniel and Jorge dot com. So think about it for a second. If someone went up to you and ask you what is the story with yep it is? What would you say? I think I Petis or a Petis is a moon around Saturn. If I recall correctly, UM, it has a very light and a very dark side, UM, so the surface is different. I have no idea where this is. Maybe um, somebody who's half the moon as an ashtray UM. I don't know. I don't know what a Petus is. So I'm going to take a random guests and assume it's one of Jupiter's moons, and based on that assumption, I'm also going to guess that something unusual is happening, like maybe there is some sort of cloud formation around it that may indicate a volcanic eruption. I don't know it's it's a moon, it's it's on Saturn. I think it's one of the ones that has a really rough time because the tides ripping it around. If it's one of Saturn's moons, that it's got more problems with being smacked upside the head by the bits of the rings. So I'm going to go out on a limb and guess volcanic action. I have no idea. I Appenenus is a moon of Jupiter, I think, but I have not seen any recent news on it, And I don't remember what in particular is significant about that moon Iapetus. I think that's one of Saturn's moons. What's going on there? Um? Some icy stuff, some cracking and plumes and hopefully lots of organisms. Um. Judging by the name, I guess Yeapetus is a moon, but I don't really know of which planet and it does anything special about it? What is going on on Lapidus or Yapetus? Well, I'm not even sure what it is. Maybe a star fall way and that does funny things, but I totally sure what it does, and I didn't get invitation to whatever it does. All right, Well, a lot of people seem to guess that it was some kind of moon, yeah, though they're not sure exactly what's the moon of Yeah, a lot of people said it's a moon of Jupiter. But first of all, how do people know it was a moon? I don't know. I guess it sort of sounds like a moon. It sounds moony, yeah, but it is. But yeah, a lot of people seem to know it's a moon or guess it was a moon, but some people have thought it was maybe a star mm hmmm. Yeah, there's a lot of good guesses out there. I didn't give people really a lot of clues. I was really curious if people had heard about this strange object, already knew about the mysteries that it was hiding, or whether it was something that nobody had heard of. You make it sounds super mysterious, So let's get into it, Daniel, what is yeap it is? Assuming that's the correct pronunciation. Assuming that's a correct pronunciation, Yeapidus is a moon, and it's a moon of Saturn. It's a good guess moon of Jupiter because Jupiter is big and it's got lots of moons, so if you're not sure, Jupiter is always a good guess. But in this case it's one of the moons of Saturn. Saturn has a ton of moons too, Right does have more moons and Jupiter Saturn does have a lot of moons. Right, And Saturn is really interesting because it has obviously the big ring system and also the moons. Right with with complex interplace sometimes interesting. It has a lot of blings it does. It's a very bad rings and rocks. It says Yeapidus to ordering new stuff online anything, it's up for anything. Um. Yes, So Saturn has a bunch of moons. This moon is really interesting though, because it's much further out from the other moons, like the other seven major moons of Saturn. The furthest one out is Hyperion, and yeapa Is is twice as far out as Hyperion. So it's this huge ball of mostly ice a little bit rock that's orbiting Saturn. It's interesting how you know a planet can be kind of its own solar system, right, It's like a solar system within a solar system. Yeah, it really is. It's fascinating and it shows you just sort of like the general gravitational structure of the Solar system, everything is really determined by its gravitational attraction. You know, we talk a lot about how gravity is the weakest force in the universe. It's so much weaker than even the weak force, and yet you see here very physically, very viscerally, how it determines the structure of the universe. Right. The reason that these things orbit Saturn and Saturn orbits the Sun and the Sun orbits the center of the key way is all just gravity. It's pretty interesting. I guess it has to do with the fact that gravity is kind of a very local force, right, Like it's very powerful when you're up closed, but a little bit less powerful when you're far away. Yeah, gravity definitely falls like one over distance squared. I think it mostly has to do with the fact that gravity is different from the other forces because it's almost always just attractive, so it can't really be canceled out. Like the electromagnetic force is much more powerful than gravity, but it has two charges, positive and negative, and so you can neutralize it. Like the Earth and Sun don't have a very large overall electromagnetic charge because that would lead to a large force and a lot of transfer of mass between the two. They're mostly neutral. It can be neutralized, but gravity you can't neutralize. It's only has positive masses as we've discovered in the universe, and no negative masses as far as we're aware, which means that everything always attracts and you can't balance that out. Yeah, it's pretty interesting, I guess. Like to a moon, gravitationally mostly just sees the plan that it's orbiting, right, Like it's probably getting a little bit tugged by the Sun and the other planets, but mostly it just kind of sees what's in front of it, right, just like we're going around the Sun, but we're also kind of a little bit being pulled by other stars and other things in our galaxy. Yeah, I see what you're saying. Absolutely, it's true that gravity dominates the structure of the universe. But I think you're saying that we get this sort of hierarchical system where you have things orbiting things orbiting other things because you can mostly ignore things that are further away, like the Moon mostly just orbits the Earth and doesn't have to worry about the Sun and Jupiter and that kind of stuff. Yeah, that's true, although as we'll hear today, Jupiter does play a role in the orbits of all the other planets. Also, it does really have a little bit of an effect that tugs on all of these things and creates chaos that can mess up the whole system and also protect us. You know, Jupiter's enormous gravity breaks up things that come into the Solar System, like it's shredded comet Shoemaker Levy when it came into the Solar System a few decades ago, and that helps protect the Earth sometimes. Yeah, it AC's kind of like magnet, right, like pulls dangerous things away from us and also sucks the mint. Yeah, exactly. So the whole system is sort of very delicately balanced, and understanding exactly how things orbit and where they're going requires understanding everything in great detail. Like when we send a probe out into the far reaches of the Solar System, we have to account for the gravity of all of those planets, which give it little tugs, because even a little tug early on is going to change the direction of that probe, which you can really add up when you're going zillions and zillions of miles. So I think, like to first order, you know, to a simple approximation, you can mostly just think about the Earth orberating the Sun. But you want to get all the details right, then you need to factor in Jubiter's orbit and Jubiter's gravity. But back to yeah, it is, so it's a moon of Saturn, And is this something we can see with the naked eye? Because I know, like if you look at it through a telescope at Saturn and you can see the reins, can you also maybe see this moon? You can't see the moon of Saturn with the naked eye. In fact, it was Galle who saw moons are on Jupiter for the first time because of his telescope. You really need a telescope to see these things. This moon was discovered by Cassini, not by Galileo, and he also used a telescope, and it was in sixteen seventy one that he discovered it. So we've known about this moon for a long long time, basically since the advent of the telescope. So if you have a telescope at home, you can maybe see this moon. Right. Yeah, you don't need a very powerful telescope to see Yapous, but as we'll learn later, you can only really see one side of Yapodus with a telescope. Right. Well, we've been yapping a lot about Yeapidus. Uh, let's stay into why it's so interesting and what is there is some kind of strange story about it. So there's like three really weird things about Yeapoitis, how it moves, its shape, and its color. To me, the motion is really interesting because not only is Yapatis much further out than all the other moons, like the other moons are much closer in they all sort of clustered together, and then you got Yeapais like way way out there. Not only that, but also it's not in the plane as the other moons. So you have like Saturn is rotating and around it are the rings, and then also the moons which rotate around Saturn, and those all move around the same axis. Like if you drew a line through the north and south pole of Saturn, Saturn itself rotates around that axis, and then all the moons and the rings rotate around that same axis, but not yeapitus, yapatus orbits on like a tilted axis. Interesting, it's not in the same plane. And that is um weird, right, because usually, like in our solar system, almost everything is going around the same plane, right, the same kind of um level. So when you have a lot of stuff going around you, it's usually in the same level, right. Yeah, And there's a good physics reason for that. It comes from conservation of angular momentum. Like the whole solar system is mostly spinning in the same direction because the big cloud of gas and dust that created the solar system was originally spinning, and that spin can't just go away. In our universe, angulamentum sticks around. If you have a top spinning without friction, it will continue spinning forever. The only way to slow it down is to come in with some sort of outside force, to bump it from something external, right, And so as solar systems started to coalesce, that very gentle spin became faster and faster. So the Sun is spinning in one direction, the planets are mostly moving around the Sun in the same direction as it's spinning in that same plane. And then all the planets are spinning in that same direction, and their moons are mostly moving around them in that same direction. So everything is super well aligned. Right. So if you see something that is spinning around another object in kind of a skewed or inclined level, that means there's maybe an interesting story going on there, right exactly. It means that you have some sort of external force that has tweaked it. And so the cool thing there is that it tells you something about the history, right. It tells you something happened here that's interesting. It wasn't just the normal formation of a moon that you would expect. You know, there's a few different ways that you can make a moon for a planet, Yeah, including in your kitchen. I guess we're along with Bobo. But let's get into the different ways you can make a moon. I guess a lot of people might want to know that if they want to make their own moon. And let's get into why it's so weird that yep it Is has a skewed orbit. But first let's take a quick break. All right, we're talking about yep it is, which, Um, it's a great name. I think I'm going to name my next child yep yep it is a great name. Well, it's a moon of Saturn, and it's a weird moon. And it's a little interesting and a bit of a mystery because, first of all, because it has kind of a skewed orbit, it's not orbiting along with the rings of Saturn. It's not orbiting at the same level as the other moons of Saturn. It's ordering kind of a in a tilted orbit. Yeah, and when you look at the moon of a planet, you gotta wonder, like, where did this moon come from? And as far as we know, there's a few different ways that a plane and it can get a moon. There's the idea that it's made from the same stuff, Like you have a big cloud of stuff and some of it comes together into a planet. But if you have a big enough blob of it that's like far enough away, then it's going to coalesce into its own little blob rather than falling into the planet and becoming part of the planet. And so it can coalesce into its own little blob of stuff, right because initially, like every planet in the Solar System was like a cloud of stuff. Right, Yeah, all you had is a big cloud and the sunsuted form and it's swallowed up most of the gas. But then you also have other heavy seeds of like places where you had a little bit more stuff than everywhere else. And you know, gravity is this runaway effect. When you have something with a little bit more density, it has more gravity, so it's able to pull other stuff in, which gives it more density, which gives it more gravity. So any place that is like a little bit more dense by chance than another place is a seed for something to form. These seeds form, and then sometimes they pull themselves together and form something larger, right, But sometimes they don't. Sometimes they're spinning fast enough to get into orbit around each other, which is why the Earth is orbiting the Sun instead of just falling into its massive gravity, because it had enough motions going fast enough to avoid falling in And so when you have a planet forming, the same thing happens. Right. Not all of the stuff in the neighborhood of the planet necessarily forms the planet. Some of it can form a moon, and that moon can get into orbit around the planet. But when that happens, you expect it to be aligned with the motion of the planet, expected to be orbiting around the same axis that the planet is spinning. That's not happening here. Yeap it Is is is orbiting a different axis, this tilted orbit. Right. I think you're saying that if yeap it Is was formed along with Saturn, it should be spinning in the same level, at the same level as its rings and all the other moons if it had been made that way. So something must have happened to it, or maybe it wasn't made the same along with Saturn. Yeah, one really fun idea is capture. You know, maybe some rock came from somewhere else, maybe it was lost from another planet, or even like interstellar object came and was captured by Saturn. Because Saturn is a big, heavy dude, right, It's got a lot of gravity on its own. It's can't compare to Jupiter. Jupiter is much more massive than Saturn, but Saturn is no lightweight, and so it's possible for it to capture our Capture is sort of like exotic and seems really cool, And it's also likely to lead to weird orbits because the orbit of that object would just depend on the angle that came in on, and it's not likely necessarily for it to be aligned with a Solar system. It could come like from the top or from the bottom, or any random angle and then get captured, and then it would have a weird orbit and it's kind of a big coincidence if if that happens, right, it's rare, Right, It's like it's rare for something to come in with just the right velocity, angle and position to actually fall into a stable orbit. Right. Yeah. Orbits are not easy. If you shoot rocks and Saturn, most of them will just fall into Saturn or be deflected away from Saturn. To get into a stable orbit, you have to like really hit the window. And there's something about yeapetus Is orbit that makes it unlikely that it came from capture, which is that it's though it's tilted, is really really circular, like it's not some weird eccentric elliptical orbit or something crazy, and a captured orbit is very very unlikely to be like perfectly circular. For that to happen, you not only have to hit just the right window, you have to hit like a perfect dot in inside that window to get into a perfectly circular orbit. So scientists think that Yeapodus, though it's tilted, probably didn't come from capture, right, not just because it's rare to have a circular orbit in a capture, but also because of what this moon is made out of. Right, that's right. And as far as we can tell, this moon seems to be made out of basically the same stuff as the other moons. It's like ice and rock. We haven't visited this moon, but we can tell by how the light reflects off of it something about what it's made out of. And so it looks like it's made out of basically the same stuff that Saturn and its moons were made out of. So it doesn't look like it's captured, doesn't look like capture can explain. It looks too much like it's a parent exactly, which is I guess ice? Is it really ice? But is it's not water? Ice? Is it. It is ice. But astronomers have a different meaning for the word ice than you and I do, of course, right, because they've taken this word that we are familiar with and adopted it for something else. Remember, astronomers also think that everything heavier than helium is a metal, right, I think oxygen is a metal. We are a metal breathing species, according to astronomers. But ice in this case can also refer to like methane ice, or ammonia ice, or all sorts of other hydrocarbons. But there is also a lot of like water ice there. There's no shortage of water in the outer Solar system, right, So I guess that's one of the mysteries is that, yeah, it is. It looks a lot like Saturn. Looks like it was made from the same stuff Saturn was, but it's in an orbit that's tilted, unlike the other stuff that's orbiting Saturn. Mm hmm exactly. So that's very weird. It tells you something happened here, m all right. What are some of the other mysteries of Yevidis. The other mystery is that its is kind of like a walnut. Most of the things out there in the Solar system that are this big are pretty round, Like the Earth is round and the Moon is round, and Jupiter is round. And that's just because of gravity. Right. If you have a big, heavy object, it's gonna pull on stuff and eventually it's gonna pull stuff down, and any bit that's sticking up is going to get yanked down by gravity. It's like the simplest shape. It's the lowest energy shape for a huge blob of stuff. That's not true for a really small blob. Like if you have rock in your hand, it's strong enough to resist the pull of gravity. Gravity is not going to form every rock into a sphere, but a big enough piece of stuff has it powerful enough gravity to overcome that. But YEAPS is not a sphere, right, But the things in the source system aren't perfectly spherical, right, Like the Earth is not a perfect sphere. It's kind of you know, a little little wide around the waist. Earth has been having too much boba at home. I think, Yeah, things are not perfect spheres because they're spinning, right, So things would be a perfect sphere if they weren't spinning, or when you're spinning, you can think of it like creating this fictitious force that works against gravity. So, like the force of gravity on you is a little weaker at the equator than it is at the north pole, so you're like way less at the equator than at the north pole. Right, It's it's kind of like hanging on at the edge of a merry go round, right, You're being kind of pulled outwards exactly, and that force counteracts the force of gravity, so it makes a lesser effective force. It's not really a force, it's just a product of you being in an accelerated frame of reference because you're spinning. You're moving in a circle. But that's what happens. And so if you spin the Earth, it makes it fatter, and exactly how fat it gets depends on how strong it is. If you had like a planet made of graphene or diamond or something and you spun it, it wouldn't get much fatter, whereas if you had a planet made of like maple syrup and you spun it, it would mostly make it into a disk. Which is why I like the galaxy is a disk rather than a spear, whereas the Earth is a sphere rather than a disc or more like a sphere. Interesting, what about the Sun. Is the Sun also a little wide around its waist, and the Sun is a little wide around its waist. And even though it's sort of like more like maple syrup than a diamond, because it's just a big ball of plasma, it's gravity is so powerful. So it's this interplay between the mass and the spinning rate and the sort of interior tension of the object that determines the final shape, right, okay, And so then yeah, it is this moon of Saturn is also not privently spherical. It has kind of a weird feature around its waist. Yeah, it's got two weird features. Actually. First of all, it's bulging. It's bulging as if it was spinning a lot, right, Like we said, things that spin faster should bulge more, right, But Yeapais doesn't spin very fast, and yet it has a really big bulge. It's like sort of fatter around the middle than it should be for its spin. So that's kind of weird. It's like inconsistent, right. I feel like you're attacking yeap It is this body positivity here, Daniel, I mean, there's no normal right in the Solar system regards to our bulges. I'm not criticizing. I'm saying it's fascinating, right, It's individual, it's different, and I love that, right. I don't want it to just like fall into the same rules as everybody else, you know yourself, yaps. Yeah, but it's but you're saying it a little bit too wide around its ways than it should be. We can't explain how wide it is around its waist just from its spinning. Could it be that maybe the inside of it is more liquid than we think it is or something like that. That's a really cool idea. Typically the insides are liquid due to tidal forces, but Yeapaus is really far from Saturn, too far for Saturn to like be heating it from the interior. There are other like big moons of Saturn and Jupiter that we think might have like underground oceans because of tidal forces, but yeap it is is too small and too far for those kind of effects. Could it be spinning faster than we think it is. No, we can measure it's been pretty well. That's not something we're confused about. But it also has a weird thing on top of this bulg Right, not only is it bulging, but a long it's waist. It has this huge ridge that makes it look like a walnut. And this is not something like a little bump we're exaggerating here. This thing is like fifteen kilometers high and twenty kilometers wide. Is one of the biggest features in the Solar system. Like when we did our Tallest Mountains in the Solar System episode, this featured on it. It's this crazy ring around its waist. It's like a one long mountain ridge kind of right that goes along the equator. The first approximation is like a big ridge around the equator, kind of like a walnut. If you zoom in, it's actually like a complicated system that has a few isolated peaks and then like a two kilometer section with like three parallel ridges. It's really strange, but mostly it seems like a sort of a ring around the middle. And there's nothing else in the Solar system that looks anything like this. Typically, when you see something in the Solar system, you can see other examples of it because it's a common process. But this, whatever caused this must have been rare because it's the only exam ample we've ever seen of like a walnut object in the Solar system. Yeah, that's pretty nuts. We're hoping to crack the mystery one, all right. Yeah, and then you said there's a third mystery about the third and the most amazing mystery in my view, is that it has two colors. So when Cassini first saw Yeapois in sixteen seventy one, it looked pretty bright. He saw on one side of Saturn, and then he thought, well, if this thing is orbiting Saturn, I should be able to see it on the other side also, So he trained his telescope to the other side of Saturn and didn't see anything, and it was very confused. And then he saw it again on the original side, and then he didn't see it on the other side. So you can only see it on one side of the planet, like as it goes around you can see it and when it's on the right side, but you can't see it when it comes around on the left side exactly. And he actually guessed the reason. He guessed that it's because it's a two toned planet. One side of it is white, the other side of it is black. It's like one of those black and white cookie or like a scoop of vanilla ice cream that's been half dipped into chocolate. Wait what and so is the idea that it's when it's one one side of the planet, it's always facing us on the chocolate side, But when it's on the other side of the planet, it's always facing us on the vanilla side, exactly because it's tidally locked. So the same part of it is always facing Saturn. So when it goes around, we always see the trailing edge on one side and the leading edge on the other side, so we see black and then white, and then black and then white. I see it. So it is spinning in place, but it's spinning in place at the same rate as it's going around Saturn, sort of like our moon. How we when you look at the moon here on Earth, you always see the same side of it, even though it's spinning around us, exactly because Saturn has pulled it to be a little bit oblong, and so it's sort of relaxed into this gravitational minimum where the closer bits get pulled on a little bit more strongly by Saturn. It's called tidal locking, and so the same side of it is always facing Saturn. So we always see the trailing side of Yappitus when it's on one side of Saturn and the lead inside of Yopotus when it's on the other and those are different colors. One is very dark and one is very bright. It's super weird because you said it looks like a walnut, right, it has a ridge in the middle, But it's not like one side of the walnut is one color, the other one is another color. It's like it has the two sides of the walnut. But then it was somebody dipped it sideways. Yeah, somebody dipped it sideways. Yeah, it's super weird. So now it has like four quadrants kind of right, like four there are four different Yepidus is Yepti. Yeah, and somebody probably made a big mess in the universe kitchen when they were cooking up this project. Maybe they're trying to make a moon size boba ball, and that would also explain why it's a little bit bulging. Maybe all the moons are just boba. There you go, you need to get into tap yoga physics. My daughter asked me once if it was true that horse hoofs were made of gummy bears. Technically, um, it depends on what the horse has been eating. I guess, Yeah, I mean, I think it's true that gummy bears are made of horses hooves, which is a little discomforting for a girl who loves horses so much and gummy bears. She had to pick one, horses or gummy bears. Yeah, well, I don't know how a horse could run with gummy bear hooves, but you know, some cartoonis could probably figure that out. Yeah, well, they have vegan gummies. Did you tell her about those? They're not as good. You love that hoof aftertaste, that's what makes so so good. All right, Well, let's get into what these mysteries really mean about the history of our solar system and one are some possible explanations for these strange phenomenon. But first, let's take another quick break light. We're talking about gummy bears and horse foods. Apparently, somehow that's related to the moon of Saturn called yep Is. You take a bunch of gummy bears, you launch amount into space, and you get them spinning, and eventually you get a Boba moon. I mean, isn't boba basically just gummy bears in your drink? But it's pretty spacey and celestial. Alright, we we're talking about the moon of Saturn called yeap it Is, and it's many mysteries. It's mysterious because it has a weird orbit, it has a weird ridge around its equator, and it's also got two sides of it, literally a dark side and a light side. Yeah, and forever will it dominate its destiny? Yeah, it's like an actual ying yang ball out there in space. Yeah, it really is that. It It looks like a huge art project. All right, Well, let's tackle each of these mysteries one at a time, Daniel. What could be causing its or what could have caused it's weird orbit. So we're pretty sure that Yeapitus was formed around Saturn. As we said, it was made at the same stuff as Saturn. So that precludes the idea that it's like some weird rock from somewhere else that came in at a strange angle. But if it formed around Saturn, then we think probably should be in the same plane as all the other moons. So another possibility is that it was struck by something. Right, another way to get external angular momentum is to be hit by something that comes from somewhere else, maybe like an asteroid that lost its way or something from another Solar system that banged into it could give it a tilted orbit. I see, like, if there's something scwed it, it came in and crashed into it and scwed it. But wouldn't that also kind of make the orbit more elliptical or some weird shape, isn't it? It's still weird that it's so perfectly circular and tilted. Yeah, I think it's likely that a collision would also perturb the shape of the orbit. So a better explanation is a series of gentle tugs from Jupiter. Remember Jupiter, we said it's sort of like the bad boy of the Solar System. It's not staying and it's laying. It's tugging on everybody because it's so massive. Remember, Jupiter is like ten times as massive as Saturn, and Yeapodus is a really far out moon. It's like really distant from Saturn. So if all of Saturn's moons, this is the one that's most susceptible to Jupiter's gravity. So it might be that sometime in the earlier history of the Solar System, when things were funky and Jupiter and Saturn were migrating their places in the Solar System, some gravitational interaction between Jupiter and Saturn could have tugged on Yapotus in such a way as to give it this weird tilt. But isn't that kind of weird because Jupiter is in the same claim and the same level as all the rings of Saturn, right and all its spoons, So if it pulled in, it wouldn't just kind of pulled it outwards on the orbit. You do have to conserve angular momentum, right, and so to create something that's off tilt, you would have to shoot something else off in the other direction. So maybe like there were two moons of Saturn and one of them got this tilt and another one got ejected out of the Solar system to sort of balance things out. We think probably it was a pretty chaotic event, But it's still sort of like a big question mark. People are running simulations, and in those simulations you can sometimes generate these kinds of tilts. So it's still a big mystery. Then it's still a big mystery we do not understand, but we know that something happened here. It's not just the ordinary formation of rings and moons around a planet. The tidal forces of Saturn are not enough to explain this weird moon. So it's like a huge clue that something big happened in the Solar System. It's so it's so far away from all the other moons of Saturn. I wonder is that if it's possibly it could have just formed that way, right, Like, maybe it's some of the some of the outer stuff that we're that was far away from Saturn just had this kind of extra angular momentum in another direction, and because it's so far away from all the other stuff, it just you know, form its own orbit plane. It's a good point that the whole Solar system has an overall average angular momentum, but like a random pocket of the Solar system can have its own angular momentum, and then you expect all those pockets to add up to the overall angular momentum of the Solar System. So it is possible to get a fluctuation there. We have like one blob that has a different direction, but it's pretty rare. Otherwise we would see this more often around other planets, and so it's a possibility, but we don't see that happening very often in simulations, all right, So maybe it could be Jupiter or maybe it had a collision, but it like, none of it is a slam dunk case. None of it is a slam dunk case. It's still an open question, and it might not be something that's very easy to figure out unless we go and explore Yapodus itself and like look at this geology and try to understand if there's something they're consistent with a big collision or not. It's so weird. Well, I guess you know, you're we were just saying that it's not likely that it was a collision because it would be hard to sort of get that orbit right. But it could still could happen, right, it still could happened possible, I mean, if it's if it's there today, and maybe that's what did happen. And actually collisions are part of the hypothesis for some of the other mysteries of the Yapodus, so it might come together interesting. All right, Well, let's getting too the other mysteries. Um, what might explain it's bulge around its middle. So the weird thing about the bulge is that Yapodus is not spinning fast enough to have that bulge. But it might be that the bulge got sort of like frozen in back when Yappotus was softer and was spinning fast. Like imagine as Yeapitus forms, it's not as cold and as frozen and as firm as it is today. It was more like a huge ball of boba. And maybe it was spinning faster before it got like tidally locked by Saturn. So originally as it formed, maybe it was spinning faster and then that shape got frozen in as it cooled, And so now it's sort of like has the bulge left over from its original spin, and then it got tidally locked by Saturn, but it still has that same shape, but it has enough time pass for um the spin to slow down that much. Yes, Saturn's gravity is pretty strong, so it's had plenty of time to tidally lock an object. Right. Yeah, that's an interesting phenomenon, right, because it requires the planet to kind of change shape to right, Yeah, a little bit like like the part of the planet that's closer to the sorry, the part of the moon that's closer to the planet actually gets heavier, yeah, because remember tidal forces come from a difference in the gravitational force on the near side and the far side. As we're talking about before gravity gets weaker with distance, which means that the Earth is pulling on the near side of the Moon harder than it's pulling on the forest side of the Moon. And as you say, eventually that makes the near side of the Moon a little bit closer, like turns into an ellipsoid instead of a sphere. And then it's sort of hard to get it out of that configuration because now you have like a little bit of a heavier bit that's even closer. So it ends up in sort of a stable state where like the long axis of the Moon is not pointing towards the planet. So like maybe before you're saying it was more liquid this this moon. Yeah, So the idea is that as it was forming before it got tightly locked, maybe it was spinning faster and it was sort of softer. It wasn't like maybe fully liquid, but it wasn't as firm and as frozen as it is today, and so it's bulge got frozen in maybe early on, and then it got tidally locked by Saturn. That's sort of like one hypothesis to potentially explain the bulge you got like flash freeze or flash frozen exactly exactly. And then remember that the bulge has on top of it this weird ridge, right, these crazy tall mountains that go all the way around the bulge, And so people are trying to also explain that at the same time, right, that it's weird to have this mountain rich around your waist of any celestial body. So what are some theories about that? Well, this is really bizarre, as we said, because it doesn't appear anywhere else in the Solar system. So there's a bunch of very different stories here. One is a huge collision, Like maybe there was a really big collision and that's the explanation for why Yeppotus is tilted. And this collision might have like tossed up an enormous amount of stuff which formed a ring around the Moon, but wasn't stable and eventually like fell down and formed this ridge around the edges. Right, But if it was just made from stuff falling on the ground, Um, why would only fall in the equator? And also how can you explain, like the peaks of it, it would only fall in the equator if it had time to gather into a ring. Remember, rings conform because gravity can compress things a long the axis of spin without any resistance. It's harder for gravity to push things towards the axis of spin, but along the axis of spin isn't a big deal. That's why, like Saturn's rings are flat. So you have some big collision which creates a huge cloud of debris which orbits and forms a ring for a little while, but then the ring falls back down onto the Moon. So that would explain why it only goes around the equator. You're right that it doesn't really explain very well why it's like such a crazy tall mountain. You'd expect more of a blob or something there. Yeah, right, Yeah, especially it's just like raining rocks. So people have other ideas, like one idea that it comes from underneath, that there's some very strange geology that was happening as it was forming and freezing, that this weird icy material like upweld from the interior of Yapitus. This is very speculative. People don't really have like a great model to explain how that might have happened. Interesting, it came from the ground, sort of like maybe how mountains form here on Earth, right, like mountains here, A lot of our mountains and ridges form from the tectonic plates crashing into each other and then kind of like well like swelling up right, pushing up, And so this could be some like cracking in the exterior and friction between those pieces or things pushing up from underneath. But you have to explain why you basically only see it along the ridge. Is very strange and it's very dramatic, Like I can't accentuate enough, like how tall these mountains are there? Really are insanely high for a tiny little moon. Yeah, thirteen kilometers high. Um. I wonder if maybe the two things are kind of related to each other, like the bulge and the mountains, like maybe before yet but it was spinning a lot faster, which kind of maybe made everything on the equator kind of push out, and then which made all the technic plates also maybe push out towards the middle of the equator, and then that created the mountains. Could have been something like that, Yeah, it certainly it could be that, like the spinning makes the equator sort of like more fragile and more likely to be the place where things are going to well up from underneath. It's certainly possible, but it's definitely an area of active investigation, all right, and then the last mystery is it's weird colors that the one side of the planet, on one side of the moon, it's bright and the other side it's darker. Like how big is this contrast? Like is it really like black and white? Or is it like one shade of brown and another shade of brown? It's really like black and white. You should definitely google this. One side of it is like twenty times brighter than the other. I mean, Cassini, it took him thirty years to build a telescope powerful enough to even see the dark side of the Appitus. It's very dramatic. Well, it's interesting that it's also interesting that it's pointing towards us kind of right, Like, what are the chances that we would see both sides, the dark and light side, and not just one side? Or is it that some parts of the year we see both and sometimes we see on only the dark side. Well, it's going around Saturn counterclockwise like all the other moons, so we're always definitely going to see the trailing side and the leading side. That gives you a clue, Right, it seems to be interestingly colored, So the trailing side in the leading side are different colors. It's like flying through space in some direction, and the leading side is the dark side and the trailing side is the bright side. It's not just like randomly oriented. What do you mean like leading side? What does that mean? So, if you're like riding a motorcycle through a huge cloud of bugs, for example, the leading side is the front face plate that's going to hit all the bugs, and the trailing side is the back side of the helmet that's not hitting any of the bugs, right, And so, yeah, it is moving around saturn, it's moving through space. It's moving in the direction of one of its sides, that's the leading side. Oh you mean like ground right, Yes, like going around a merrygoround. If you're facing one way, you know you're faving in the front part of your body is going to hit all the bugs, but the backside of your body is not going to hit any bugs. Exactly. So when you get off your motorcycle and you look at the helmet and you see insects covering the front and not the back, you don't think, oh, it's weird that it only covered the front. There's like a reason. It's connected to the fact that you're moving through that cloud of bugs in a certain direction. That's why you have bugs all over the front side, the leading side of it. And so the fact that the leading side of Yapodus is the dark side is a big clue as to why it's I see, as it goes around Saturn, but then Saturn is also going around the Solar system, so if it is picking up bugs or the equivalent of bugs, it's like stuff that's near Saturn as well, exactly. And that's just what they figured out. They pointed the Spitzer space telescope at Saturn, and remember Spitzer is an infrared telescope, so it's really good at seeing stuff that doesn't reflect a lot of light but glows in the infrared. And what it discovered is that there's a huge ring of Saturn that nobody knew about. It's basically like an enormous ring of dust. It extends really really far out even well beyond the Yapodus. So this is huge cloud of dust and Yeapodus is basically flying through that cloud, sort of like it's flying through a cloud of bugs. It's just like it's flying through a cloud of bugs, and this cloud is actually rotating the other direction from Yapais. So it's like flying through a headwind of this dust. It's actually one of the rings of Saturn, this really really dusty, sort of diffuse ring of Saturn that it's flying through. It's interesting that it's happening on this moon of Saturn, Like why isn't it happening in our moon? Like why doesn't our moon look half white and half a dark Well, because Earth doesn't have this huge dusty ring that our moon is flying through, and so Saturn has this huge dusty ring. They think it comes from another one of the moons of Saturn, Phoebe. Phoebe is this very very dark moon, and it's basically getting shredded, it's getting hit and it's falling apart, and it's leaving this big dust trail, and the Yeapodus is flying through that dust trail. Yeah, so it's it's creating this kind of trail. But then that's in the same level as all the other moons, whereas in yeap Its is literally like dipping in and out of this right sort of like like you were saying, it's like a chocolate like an ice cream ball being dipped in chocolate exactly, and Yeapodus is the furthest out, which is why it sees most of this dust from this dusty e ring created by Phoebe. And it's not actually the only place this happens. Like Callisto, one of the satellites of Jupiter, also sees a little bit of a contrast on its leading edge and its trailing edge for similar reasons. Well, which side do you think is better to live on? The dark side, the filled with a bugs splatter or the cleaner side behind. Well, the dark side is hotter, and that's one of the reasons why it's dark because this dust falls onto it and then absorbs more of the Sun's radiation which warms it up, which also then like boils off any of the ice which like floats up and then lands on the other side. Wait what Once the dust lands, it warms up that half of Yeapitus, and that contributes to the darkening of the planet because it boils off any of the ices which land on the other side. Wait to the ice is what makes it look clear? Yeah, the ice makes it look brighter. And so when the ice evaporates, what are you left with rocks? Yeah, So when the ice evaporates, it reduces the reflectivity of that side, right you left with rocks and other stuff that doesn't reflect as much. So it's just sort of like when you make snow dirty, right, it melts much faster because it's able to absorb the sun, and then it gets darker and darker, and it's a runaway effect. The same thing is happening on Yeapotus. One side of it got covered in dust from Phoebe, and that like melted all the ice on that side, warming it up, and all that ice like reformed on the other side, and now one side is super bright and the other side is super not that it's weird, And wouldn't that also change its shape, Like wouldn't it look flatter on the the side that's getting pelted, like the stuff is evaporating away and landing on the other side. Wouldn't that make the overall moon have kind of an oblong shape a little bit? But I think we're talking about like centimeters worth of covering out like meters or kilometers, So I don't think it makes a different sort of geologically interesting. So I guess you would want to live on the warmer side right of an ice planet, Yes, I think so. You want to live on the warmer side, but you're also going to be sweeping dust off of your solar panels basically every day book splatters. You'd be pretty excited to discover bugs out in space. I guess that would be the bigger news. All right, Well, it's pretty cool. I guess you can look at pictures of this moon and and see the contrast right between the two sides. It's very easy to spot exactly. It's very dramatic. Somebody definitely dipped the appetus in hot couco or bugs, or maybe the opposite. Maybe it's actually chocolate and it's been dipped in vanilla. Yeah, maybe it's chocolate bugs too. But is it pretty conclusive that people feel pretty confident that that this is the reason it's has two colors. Yeah, they discovered this ring about ten years ago, and they've done a bunch of calculations and they think it all clicks together that there's enough dust that comes from Phoebe to cover this moon to change the temperature to create this runaway effect. So it's a pretty solid explanation. They're pretty sure it's not boba. They're pretty sure it's not boba, but you never know until you do of the experiment. So we've got to send a mission out there to take a taste of Yeapodus that's right, the bo emission bo bo bo one to find out conclusively if the answer is Yeapidus or Nupidus that's right, or Yapides speaking of dirty snow. Not my PTIs your putis right? Al right? Well, another sign that there are still big mysteries here in our own backyard, in our Solar system. There are things that are the way they are, but nobody quite knows how they got to be their way, And everything around us is a clue about the incredible story of the Solar System and the wider universe. Everything is the way it is for a reason and has a fascinating backstory, and if you watch enough episodes, eventually all those backstory details get revealed, right, Or maybe it was the Solar System was just making it up as win alone, as most TV shows happen, because you never know. You didn't know if it was going to get renewed for another season. So you can't redcon physics, not without a time machine. I thought that's what physicists were, professional red connors, Like this is what happened. No, wait, this is what happened. We argue about what happens, but we can't actually change it. Mm hmm, but he can make up different stories about it kind of. Yeah, that's true. All right. Well, we hope you enjoyed that. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production of I Heart Radio. For more podcast For my heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. Yeah,