What will the Lucy mission teach us?

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Speaker 1: Hey, Kelly, are your kids into mystery novels? My oldest is really into reading, but right now she's mostly into comic books with like cats and dogs that have big sweetler lies and you know, things with with really cute little animals. Well, have you tried to hook them on like the Grandest Mystery of all time? Now? I am onto you. This is probably about planet killing asteroids or the death of the sun. You are definitely going to be finding some way to frighten my kids, right, Oh my gosh, Kelly, I would never Oh man, oh yeah, why don't I believe? You know? The Grandest Mystery is not at all about death and destruction. It's about the birth and the creation of planets. Well, that sounds more like a romance than a mystery. It's a bit of the astronomical birds and bees. Hi. I'm Daniel. I'm a particle physicist and a professor if you see Irvine, and I love seeing new planets get born. And um, Kelly Waynersmith, I'm a parasitologist with Rice University, and I love hearing about new planets being born. Do you love getting those announcements like come check out our new cute little planet it's got little googly eyes. Yeah, that's the best. No, I guess baby planets actually aren't that attractive. They're like, you know, covered in lava and pretty nasty looking. Actually, well, you know, I'm gonna go ahead and blow your mind here and say that, you know, human babies are kind of kind of gross. Oh, I'm so glad you admitted that. I totally agree with you. Like, there's the rare cute baby, but most of them look like, you know, Richard Nixon or like Winston Churchill or something. On a bad day, that's the one that looks like Dandy DeVito. And I was like, man, and you know, it's a good thing that parents live their babies. It is a good thing. And I'm sure for you, dear listener, your baby is the one cute baby out there. Really gorgeous. Great job with that kid, amazing, amazing, a plus. But the joy of life and the joy of seeing your friends have kids is not because their baby is necessarily cute. It's because it's an incredible process. Because what you're witnessing is the creation of new life and the continuation of this incredible journey. And in the astronomical context, the same is true. We're excited to see the birth of new planets, not just because that planet is cute and lava colored, but because it tells us something about our context, where we came from, how our planet was born. But I bet it's a lot more complicated than just watching human babies. I don't know. Do you have to feed planets? You have to change their diaper? I mean they never wake up screaming, do they? Those are all excellent points. Yes, if all you have to do is look through a telescope, you should consider yourself lucky. And looking through telescopes is mostly what we do because we're interested in solving this detective mystery, in unraveling the story of the creation of our own Solar system, in understanding how Earth got to be where it is, and is that unusual? Are there other Earths out there in other solar systems? All of these questions can be answered, but first we have to dig up clues, clues that lie in wait for us all over the Solar system, and we need to get money to do that. Now. Some of those clues, of course, are right here on Earth. You know. We can dig into the crust of the Earth and understand things about the formation of the Earth, things that have shocked previous generations of scientists. Imagine living in a time when we thought the Earth might be like thousands of years old. We had no idea of the geological time scale. Like reading those stories about people who study glaciers or geology and come up with these calculations, are like, hold on a second, this suggests the Earth is billions of years old. That's crazy. It must be wild to come up with a finding like that and think, my goodness, how am I going to convince everybody that we've been off by by so many orders of magnitude. It's one of those like open your third eye sort of moments, like you've been smoking banana peals around the campfire and you suddenly have this new vision right of the way the universe works. Jokes aside that for me is like my scientific fantasy to make a discovery that just like pulls the rug out of our entire understanding of how everything works, Like what this is super crazy old, that's amazing. But so I assume that those kinds of discoveries happen less frequently the longer science goes on. What do you think your chances are of having one of those moments. Oh, I think that there are lots of opportunities left. I think actually, as time goes on in the last hundred years, our estimate of the fraction of knowledge we have about the universe just keeps dropping and dropping and dropping, like we keep making discoveries like, oh, turns out of the matter out there in the university is something else nobody's ever studied before. Oh, it turns out two thirds of the energy in the universe is something weird and new and bonkers, like dark energy. So as time goes on, we certainly learn more, but we realized that we have a smaller and smaller fraction of the total knowledge than we thought. So I think there's lots of discoveries ahead. What do you think. I think you need to pass the banana peal because you just blew my mind. Well. One of the ways that we find these things is by looking for sort of like time capsules. We try to figure out what has been undisturbed since the early times of the Solar system, to find like a scoop of the early Solar system and study it before everything has gotten like messed up in the intermediate ages. And one way we can do that, of course is look into the Earth. But the Earth is sort of dynamic, you know, like the Earth is four and a half billion years old, but also a lot of stuff has happened on Earth, and so one thing we can do is like look on Earth for really really old rocks that might tell us like what was Earth put together from? What were the basic building blocks of the Earth. What was going on in the Solar system four and a half billion years ago that led to the formation of the Earth. But you know, there's something puzzling there. I don't know if you have the same sense, Kelly, when we talk about like the age of rocks. I remember hearing about this when I was a kid and being like, what do you mean the age of rocks? Like that rock is made out of like iron and silicon and carbon. That stuff is super duper old. What are you talking about the age of rocks? Did that confuse you when you were a kid? Yeah, no, absolutely, And even sometimes I still find it a little confusing now to think about rocks having different ages. Yeah, And I think the way to think about it is not in terms of like the building blocks of the rocks, Like pick up a rock in front of you, it's got in it elements, and those elements were formed the hearts of stars or in supernovas or neutron star collisions that may be much much older than our solar system, right, because our solar systems like four and a half billion years old, but the universe is almost fourteen billion years old, and there's been many cycles of this process where stars pulled together with helium and fuse heavier and heavier elements and then blow that out into the universe to make the raw materials for new solar systems. So, like the iron that's in your body, maybe much much older than our solar system. But when we talk about the age of rocks, we're not talking about the age of the stuff inside of it. We're talking about the age of this arrangement. So it's sort of like if you have a pile of lego pieces, you know, and somebody puts something together and then it sits on your shelf for a few years. How old is that, like lego dinosaur that your kid built, Well, it's five years old, right, because that's when you put it together, not twenty five years old. The age of lego pieces. So it's more like the age of the arrangements of the things that make it this current rock that sort of defines the age of the rock. Does that make sense? That does make sense, But it sounds like a lot of looking down for an astronomer to be doing, don't you guys usually look up? Well, we like to look up, right, We like to see how things are going outside in the universe. But that's a lot harder to look at, right, And so typically people do dig around and try to find asteroids that have hit the Earth recently, because asteroids are these incredible time capsules while the Earth has gone through all sorts of cycle of like melting and reforming, and the rocks here can be fairly young, right. We have like rocks that were formed yesterday. You go to Hawaii and you'd like pick up a piece of lava that's, you know, still a little warm. That rock is like, you know, a week old rock. Cute little baby rock. Right. But there are some rocks in the Solar System that were formed four and a half billion years ago in those early moments when people were putting those lego pieces together and haven't really been doing much since. Right, They didn't get pulled into a planet. There's just sort of like the leftover bits, like when you're making bread and your countertop and there's all that flour leftover that didn't like make it into the bread, right, that's sort of the leftover ingredients and stuff that didn't make it into the solar system. You know, it still blows my mind that we can pick up a rock and be like, you're not from around here, and and figure out what rocks came from the solar or you know, from outside Earth, and which ones, uh, we're born here. It is really incredible and it's a testament to all of this careful work by geologist understanding how rocks can form, what are the conditions to make this kind of rock. Amazing thing to me is that these rocks are sort of stable. Like some kind of rocks you can only form under crazy conditions super high pressure. But then you can take them and put them on the surface of the Earth and they stay that way, right. They don't like automatically revert and melt back to their basic ingredients. It's not like ice where you can make it in the freezer, but then when you take it out it turns back into water. These rocks, you make them in crazy conditions and then they just sort of like freeze that way forever, even if you bring them to new conditions. That's sort of amazing, Like that's the only reason why a lot of geology is possible. It's very helpful of them. It's very helpful of them, exactly. And just like when we talked about in the episode about where is most of the water on Earth? You know, there's some of these rocks that are formed like in the presence of water and trop water inside of them and then come up to the surface and you can like get a little core sample of what's going on deep unto the Earth. It's really amazing. That is really amazing. So we've done a lot of work here on Earth to try to understand like how Earth was formed, and we've picked up rocks we think came from space. But scientists are invasion to learn more and want to understand how the Solar System was formed, and so of course we want to look at asteroids like in sit you, we want to go to the asteroids and visit them ourselves and study them and see like what are these basic building blocks of the universe. Why are there these legos left over that nobody put together into planets. And that sounds really hard. It does, i'd really hard. But fortunately we have really clever people with really fun beards who are working on this project. Did you say with really fun beards, with really fun beards exactly? That's really important. It's not important that people have beards while working on these projects. Beards are not necessary. But the project we're talking about today is led by somebody with a really awesome Santa Claus style beard. Nice. That always makes me feel very comforted to see somebody with the Santa Claus style beard. I feel like they're going to give me something nice and I want to sit next to them. And so on today's episode, we'll be asking the question what will the Lucy Mission teach us? And in fact, the Lucy Mission is headed by Harold Levison, which if you google him, he's got an awesome smile and a huge beard and he looks like he's about to give us all science presents. Oh do you know him? Is he Santa esque in personality as well? I don't know him, but I did actually watch a video with him, and he's like bubbling over with excitement and enthusiasm. He's like a kid on Christmas morning. About to unwrap secrets of the universe. Oh, I just looked up a picture and I like him already. He does look like he's a happy looking guy. I know. It's a lot of fun. And So the reason that Harold is so excited about these asteroids, and the reason I'm and so excited about these asteroids is that they might contain secrets about the formation of our Solar System. They might even have hints about the formation of life on Earth. You know, during the early Solar System. We think that some of the carbon based molecules and the other volatile materials that serve as the building blocks of life, some of those may have actually been brought to Earth via asteroid and calm the terry impacts. So if we can go out and understand, like what's in these asteroids, are there organic molecules out there, we might get a better clue to understand how life on Earth form, not just the planet, but like the critters on top of it. Well, so there's nobody who's proposing that life started on asteroids and got deposited here, But the idea is that the building blocks of life were on the asteroids and got deposited here and then life could come about? Is that right? I don't think it's fair to say nobody is proposing that. Somebody out there is definitely thinking that. I'm not sure if it's just the person who currently has the banana pe Like, you've probably heard the idea that life may have started elsewhere and then landed on Earth. You know, we are all martians. Sort of an idea, you know that's not necessarily well found, that it's just speculation, But it is a question, like what do we find out there in the asteroids? Is it just the basic building blocks of life? Are there complex organic molecules out there formed in the collisions of objects in the early Solar System? We just don't know. It's a big question mark because we haven't gone to look. And what we do know is that the universe holds lots of surprises for us. Every time we dig into something, we find things that are shocking that up end our understanding of the universe. So it's always worth looking, and there's always good job security you'll always find the next question exactly way to make a cynical I mean, I'm just waxing poetic here about knowledge for knowledge's sake, And you're like, Daniel, you're just worried about your four oh one k that's the role I play in this diet. I'm okay with that. I'm the dream killer in my relationship with Zach too. All right, Well, unless this turns into a marriage therapy podcast, let's move on and talk about what we can learn about the early Solar system. And so, as usual, I was curious if this was a mission that people had heard about, if people knew what the Lucy Mission might teach us, what makes it unusual, what its special abilities are, and specifically, what questions it might answer for us about the nature of our own solar system. So I went out there as usual and ask folks to comment on these questions. If you'd like to participate in this fun game for a future episode, please don't be I write to us two questions at Daniel and Jorge dot com. So think about it for a minute before you hear these answers. What do you think the Lucy Mission might teach us? Usually people had to say, I have not heard of this mission, but I do know that physicists and uh astronomers like to name things with acronyms. So whatever the mission will teach us I am sure it is within the name somewhere an acronym form so UM. From what I understand, I mean, I guess it's it's going to teach us more about the makeup of those asteroids and UM and in turn the makeup of our Solar System. Okay, I think I just saw news about the Lucy mission, something about the Solar panels. Maybe not deploying correctly, but hopefully if all goes well. UM. I'm pretty sure the Lucy mission is looking at asteroids and how they helped form primordial planets when the Sol System was forming, or at least I think that's the goal of the mission. I think it's going for the Trojan asteroids that they go in front and back of Jupiter. Everybody thinks that these asteroids they are from the beginning of the formation of the Solar System, and it will teach us a lot about how and when and a lot of things about Solar system. I actually have no idea what the Lucy mission is, but I hope it results in less click bait about asteroids coming very close to Earth. If I remember correctly, the Lucy Mission UM is going to bring information about the composition of asteroids like what is inside an asteroid? So I really liked the first answer because it was the first thing that I thought of. And so NASA does love some acronyms. Is Lucy an acronym? Unfortunately, no, Lucy is actually not an acronym. But there is a funny story there. The Lucy Mission is named after the Lucy fossil, which is this famous ancient fossil dug up in Africa that's sort of a missing link that shows like an important step in human evolution. And that fossil, of course, is famously named after the Beatles song Lucy and the Sky with Diamonds, which of course was written after the Beatles themselves had been smoking bananappeals. So there is a connection there. Oh good good, Yeah, we're all connected, to say. But the concept is, the reason they named it after a fossil is that they think of asteroids as fossils. They're like, these are captured bits from earlier times. This is like a snapshot of what was going on four and a half billion years ago. If we dig into this, we can understand something about the Solar system at a time when we don't otherwise have access to it. Right and same way like biologists would love to go walking around Africa two million years ago and see, like who's climbing in the trees? Right, but we can't. Instead of we have to just look at the fossils as a way to get a sense for what was going on back then. And have we thought of asteroids as the fossils of the solar system for a long time or is that sort of a new idea. That's a really good question. I think in the last few decades it's definitely been understood that asteroids played this vital role in understanding our solar system. As we've developed this idea for how the solar system formed, you know, I think for a long time we imagine that maybe everything just sort of like came together harmoniously, that you start with this big cloud of gas and dust and just sort of collapsed gravitationally. Now we know that the solar system probably had a lot more drama in it than we previously imagined. There's this model of how the solar system formed called the Nice model, named after the city in France where it was developed, and actually Harold Levinson played a big role in the development of this model, and it suggests that some of the big planets, Urinous, Neptune, Saturn were formed closer to the Sun than they are now. Right, that these big planets are more likely to form closer to the Sun, and that later they got sort of kicked out, that the gravitational interactions between these things were unstable, and some of them got kicked out further into the Solar System. And actually we may have even lost a giant planet in the process. And you and I did an episode about like where is Jupiter now and where the Jupiter been? And we think that Jupiter may have started on the outside and then migrated in and then then pulled back out by Saturn, and in the process we think that these leftover ingredients, these asteroids probably got scattered all over the Solar System. And so I think like this recent understanding of this process to form Solar System has given asteroids special importance. Interesting. So, so I know that you can find asteroids in the main asteroid belt, which is out past Mars, but before you get to Jupiter, and then there's also near Earth asteroids which are a little closer. Are they all fossils of the Solar System or did some of those come about at different times or did they just sort of like end up in different places but all sort of started at the same time. We don't really know. So, as you say, there's this like main belt of asteroids extends between Mars and Jupiter from like two point one to three point three a U. One of the interesting things about the main belt is that there seemed to be several populations of asteroids. There are these carbonaceous asteroids with the lots of carbon in them, called C types. There are these stony S type asteroids. Then there's some really rare M type asteroids that have a lot of heavy metals in them. And they're also seemed to be some that are like rubble piles and other ones that are really compact. And one of the questions we have is like, do these in fact all come from the same original place in the Solar System where they gathered together in some of these crazy events, you know, where Jupiter's throwing stuff in and out of the Solar System? Is this just like the remnants of the mess? Like you come home after you're leaving your kids for an hour and the floor is covered in cheerios and also in toys, and you're like, huh, where the eating toys materials together where those different crazy moments in the hour I left them, right, It's it's a fun detective mystery quote unquote fun Exactly who made a mess of my solar system? That's really the question we're asking today. So like I'm picturing now that room that you talked about, and I'm also picturing you know, sci fi movies that I've watched where they've had to move through the asteroid belt and the asteroids are really packed in their super close together. Is that like would you be like dipping and dodging as you go through or they actually more spaced out and like just for you know, dramatic effect in the sci fi movies, they're really close together. They're really spaced out, And so those pictures you have of like the Millennium Falcon like dodging and dipping whatever. You can't go evading stormtroopers in the asteroid belt because they're really spaced out. I mean, there are a lot of asteroids and the mass adds up to a non trivial amount. But also space is really really big, especially as you get further and further from the Sun, Like the amount of volume grows as the radius cube, right, so like the space between Mars and Jupiter, there's plenty of room there for lots of asteroids, and you can probably stand on one and not see any others from the surface of it. Oh, I kind of feel like a dream of mine has died. You are ruining sci fi movies for making you too, are a dream killer, Daniel. But I'm making asteroid mining more realistic, right, because it's easier to get in and through the asteroid belt if indeed you can stop, right. Isn't this something people imagine that we could like stop on asteroids and dig up a huge chunk of plutonium or platinum or something, these incredible minerals that exist on the asteroids. Yeah, but it's complicated by things like how do you land on a rubble pile or how do you wrangle a giant, you know, C type asteroid. These things are complicated, But yes, you're right. It will facilitate things that you don't have to worry about one asteroid slamming into another while you're trying to get your work done. And you know, I've heard people criticize asteroid mining is ridiculous, like how would you bring a huge chunk of platinum back to Earth and that would be super expensive and crash the market, etcetera. But have you done any research into like asteroid pit stops, Like say you're on a ship and you need extra fuel. You're going through the asteroid belt and you stop on a frozen blob and extract some ice from it and get some hydrogen. Is that more realistic because you don't need to bring it back to Earth and sell it. You can actually like use it for your own local purpose. Well but so, I mean, so in your example, you are at the asteroid belt on your way somewhere else, and where where else would you be on your way to in the next couple of hundred years? You know, like I don't imagine us having you know, homes on Enceladus for quite a long time. Well, I was gonna say, I can imagine if you live on Mars, maybe you'd want to go out to the asteroid belt for some building materials, like you go to lows or home depot. But you know, I think for a while the Martians will be trying to use stuff on Mars. So I maybe at some point the asteroid belt will be helpful as a waypoint or a supply point. But I think it's a little bit far off, all right, But I'm hearing it's not impossible, folks, not impossible. We could be making pit stops in the asteroid belt. I think it might happen one day. Well. One of the most interesting things about the asteroid belt to me is that the asteroids are not just confined to the asteroid belt, like we're all familiar with that. But it turns out that there are more asteroids in the Solar System than just the ones in the main belt. There are two clumps that are super fascinating that are called the Trojans. These are two blobs of asteroids that are not in the main belt. They're actually in Jupiter's orbit, like one orbits the Sun ahead of Jupiter and one orbits the Sun behind Jupiter. Are they trying to sneak into Jupiter. Well, one of them is called the Greek Camp and the other one it's called the Trojan camp. So I'm sure they've got billion year long nefarious plots that they are hatching. They're very patient, they're very patient. But now these guys are hanging out in sort of lagrange points. Lagrange points became famous sort of when James Webb Space Telescope launched, and people learned about how it's living at L to this stable orbit. If you have two massive bodies in the Solar System, there are only a few places you can hang out where you can be stable, where like the gravitational tug is not going to change where you're orbiting. One of those is L ones, for example, and the Earth and the Sun. L one is a point between the Earth and the Sun. You can hang out right there and you're gravitationally stable. Nobody's tugging you out of that spot. L two is the same, but on the other side of the Earth, like in the shadow of the Earth, and that's where James Webb is. L three is like on the other side of the Sun than the Earth. But there's also these other two points L four and L five which are stable where you're like sixty degrees behind the Earth or Jupiter sixty degrees ahead of the Earth or Jupiter, and you can orbit stable there. So they think that back when the crazy days, when Jupiter was scattering cheerios and asteroids all over the Solar System because the parents weren't around, that some of them landed in L four and L five and have been hanging out there ever since the interesting I thought some of those were only like mostly stable, but you still still kind of drifted. But like, are all of those stable stable? Like those asteroids are not going anywhere for as long as we uh, you know, were to be able to go one check, well, none of these points are like totally stable, even L two, right, it's not a hundred percent stable. You can get boosted out of it. And L four and L five are less stable than L one, two and three. But they've been there for a long time, right, those guys have been floating there, we think, for billions of years, and so they found a little sweet spot. Also, the other thing that makes these unstable is that there's more than one thing, so there's complicated dynamics. All this goes out the window if you get bumped by your neighbor and now you have like a new velocity vector that takes you in another direction. But you know, it's been billions of years and lots of the bumps have happened, and so these things are mostly flying around pretty happy, and we expect that they will stay there, most of them, for billions of years. Of course, occasionally you get collisions and things fall into the Solar System and wipe out dinosaurs, etcetera. Yeah, the little thing like that. So is there any reason to be interested in these relative to what's happening in the main asteroid belt? Would they be easier for us to send something to to go study for example? No, these are not easier to get to. But we think that they might have a different collection of stuff than the other asteroid belts. Everything the Solar System seems to like a different composition of the stony type and the metal type and the carbon type, and so people haven't studied these nearly as much, and so it's sort of like an untapped pocket. It's places people haven't explored yet. Well, so it seems like there's lots of places that would be fun for Lucy to visit. Where is Lucy going? Right? So, Lucy is a really fun and very exciting mission that's going to explore a lot of these things. I want to get into more about it and exactly what Lucy is going to tell us about the nature of the Solar System. But first let's take a quick break. All right, welcome back. So, Dan, you were just about to tell us where Lucy is going, So Lucy is actually going to visit eight different asteroids on this one trip. It's kind of crazy. They're gonna stop by one main Belt asteroid and it's gonna go visit seven Trojans. It's going to go both to the Trojan camp and to the Greek camp. The whole thing is this crazy zigzag around the Solar System. So how did they pick their one main asteroid Belt one to visit? That must have been a hard choice. Actually, it's funny. They're visiting one called Donald Johansson, which is named after the discoverer of the Lucy fossil itself. Right, So the Lucy mission is going to go visit the Donald Johansson asteroid. So there's a part of me that thinks it would be sort of beautiful to have that connection and that that's a fine reason to pick it. But there's another part of me that feels like there must be a better criteria for picking which out of all the Main Belt asteroids you're going to visit, and so why did this one get picked? Well, part of it is just what is possible. You know, in the Solar System, things move slowly, and so if you want to visit stuff you have to visit stuff that happens to be fairly close to each other at the time that you are there. For example, that one of the reasons that like Voyager and Pioneer could visit so many planets back in the seventies is that there was this window when you could fly out from the inner Solar System and visit those planets as they came around the Sun. Some of these things have a super duper long orbits and so this is dictated mostly just by what's going on in the Solar System. And actually there's a hilarious story about how they designed this mission. The original plan was like, Okay, here's two asteroids we're gonna plan to visit, and they planned the whole trajectory. And then in two thousand and fourteen, before NASA selected this as a mission, Brian Sutter, a long time mission trajectory designer, was walking Harold Levinson through a computer simulation of the proposed route and Levison was like, hold on a second, We're gonna come kind of close to this other one, Patroclus, which is this pair of Trojan asteroids that orbit each other, and this is like one of his favorite Trojan it's this weird binary pair where Patroclus and Monoecius are like rotating around each other. It's super fascinating. And as he saw like the projected trajectory of Lucy, He's like, wait a second, can we stop there at the time? And so Sutter is like, you know what, I think we could. And so then they went and they like dug through the orbit. SE's like, what else are we going by? And he fed like seven and fifty thou known asteroid orbits into this crazy Excel spreadsheet. What Yeah, I spent months running calculations on it. And so they used Excel to design the trajectory of this thing and found all these other opportunities, and they ended up adding, you know, six different stops. So this thing went from visiting two asteroids to visiting eight asteroids because basically, you know, science Santa Claus enthusiasm and Excel spreadsheets. That's awesome. On the one hand, I can imagine the guy who thinks his job is done and then someone's like, well what about this, and being like, oh, like, I've had so many moments in science where I've been like, oh I thought I was done. But that's awesome. So we have to find out. I know, it's like when you're driving between two errands and you're like, oh, there's a donut shop. I don't really want to stop, but I do want a donut, right, That's right? And because exactly, and so this mission is going to visit more different destinations and independent orbits than any other space mission in history. And I totally encourage you to google the Lucy trajectory because it's kind of bonkers. So it launched already, They launched it in October one, and it's starting out. It's going to take like two different gravity assists around the Earth over the next few years to try to get up a little bit of speed before launching out into the outer Solar System. That's incredible to me. The fact that we ever figured out gravity assists is also incredible. So, Okay, we're gonna spend a little time hanging out with our buddy the Earth for a while and then what's next. Yeah, And remember, the idea of a gravity assist is just to limit how much fuel you need. You need fuel later on in the mission to help you like change course and go from one asteroid to the other. Do you want to minimize how much fuel you spend on like getting out there to the asteroid belt, and you know, the more fuel you carry, the more fuel you need. It's a very thin budget, and so we use gravity assists because it takes longer, but it means you don't need a much fuel. And the way a gravity asists works is that you like swing close by a planet, you come out going another direction. You can actually also pick up a little bit of speed, which is kind of crazy, not just like a totally symmetric operation. You're actually stealing a little bit of energy from the planet that your gravity assisting around, like an you know, imperceptibly small amount of energy. This thing is gonna make two swoops around the Earth and then it's gonna go visit this asteroid Donald Johansson, which is in the main belt. That's like four years from starts to initial visits. So like out of the eight places, four years later, it's just reached the first one. When a grant gets funded, what happens to those people for the four years in between, Like I do they have a lot of work to do or is the like trajectory sort of programmed in? They have to monitor it right and they have to keep on track of it in case it goes off of course, etcetera. But there isn't a lot of work in between these stops to planning these projects. It's a little tricky, right You have to have people who have different expertise at different times. And this project is going to last for fifteen years, like some of the data they're going to get in the mid twenty thirties, and you know, science Santa Claus is not that young. So actually, what they've done for the major parts of the mission where the lead is kind of old, is that they've designated a successor, like a younger person in their career who can take over in case they need a replacement. You know, this is like a game of Throne style planning. You know, that's a little morbid, but but probably smart. And so I guess no grad students, I mean maybe you if you're a grand student working on this project. It's because your advisors on the project and you get some of the data. You have to be careful with students and post docs who have sort of short time horizons working on this stuff. You can do a pH d thesis on a project like this where it's like development of it, or you know, stabilization of it, or guidance systems or navigation, and then somebody else can come along into a pH D thesis. It's like analysis of the data. Those are all, you know, totally valid contributions. I think these days we recognize that some of these projects I have such long time cycles that we need people to work on the initial bits, for example and particle accelerators. People have been writing pH DDCs on the Atlas detector before it was even built, you know, stimulated studies for how we should build this kind of thing. It's an important contribution to the field, you know, Yeah, yeah, okay, fair enough. Alright, So it takes us four years to get to Donald Johannsson and tell me a little bit more about what Donald Johansson is. Like, we don't really know that much about it, but it's really fascinating. It's actually quite small, it's like only four kilometers wide. But they suspect that it's a fragment of a collision from like a hundred and thirty million years ago. They think there was a meta asteroid they got smashed into and created like all of this shrapnel, and that Donald Johansen is like a piece of that and so by studying that they hope to understand like what happened and what was that big one made out of and sort of like get a sense by the inside of that mega asteroid, because you know, some of these things are rubble piles, but some of them have layers. You know, some of these things were like pro to planets has sort of started to form and then got arrested because no more material came by. Like there are actually dwarf planets living inside the asteroid belt or like Vesta and Series. These are layered with like dense material at their cores. They were on their way to becoming planets. They had just gotten bigger helpings of the raw materials. Okay, And so so we started Donald Johansson and then where are we going next? We visit the L four cloud, which is the Greek Camp. This is the one orbiting like sixty degrees ahead of Jupiter. And there it's going to visit a bunch of asteroids and hang out for a little bit. It's gonna sort of like swoop through and stop by and check out a couple of them, and then it's going to swing back around and it's going to visit Earth again. In twenty thirty one, this time to change directions so and can go out to the other Trojan camp. This is why physics makes no sense. How does it make sense to go back to Earth to go back out to Jupiter. You guys are tricking us. I think we'll remember that these things are on opposite sides of the solo sits them, right, The Greek camp and the Trojan camp are each sixty degrees separated from Jupiter, which means they're a hundred twenty degrees separated from each other, and a hundred eighty is the opposite side of the Solar system. So these Greeks and Trojans are really distant from each other. So if you're at one and you want to head to the other, stopping by Earth on the way, it's not really like out of the way. We really are the donut shop between two errands. Alright, Alright, that checks out. So then they go to the Trojan camp, and then there's somewhere to go after that. So then they go to the Trojan camp. There they get to visit a couple of those really interesting asteroids we talked about, Patroclus and Venetius. These are really fascinating because they're orbiting each other, they're like in a very tight binary orbit, sort of like weights like a dumbbell, spinning around each other, but without any connection in between them. And people don't know, is this like part of the process of forming larger objects that you get this like binary inspiral which gradually comes together to form a larger object, or is this stable? Could they last like this forever? And one of the fascinating things about this pair is that they don't actually orbit in the ecliptic right Most of the stuff in the Solar System or based in sort of like a flat plane, like Venus and Earth and Jupiter and all the way after like Neptune and Uranus, are mostly in the same disc because they have the same angler momentum as most of the stuff in the Solar System. But a few things are a little crazy in the orbit like above or below the ecliptic. Means that they're not often in the ecliptic right there, like at an angle, And these guys are orbiting above typically the ecliptic and then dip down below, and so they're actually gonna pass right through just when Lucy gets there, so will be a really rare opportunity to see these guys up close. Man, it seems like this team looked out in a lot of ways. Yeah, it's a really happy coincidence that they're going to get to visit all of this stuff, and then after they visit this trojan camp, they're going to go into a stable six year orbit back and forth between these L four and L five clouds just to get like as much data as possible. There's no point in like bringing this thing back to Earth, so they figured, like, let's just let it hang out out there and gather as much data as we can until it runs out of fuel. Oh so the six years is when it runs out of fuel. I think six years is how long it's going to take to go between L four and L five after its last visit. So every six years after that it's going to pass between L four and L five and it will continue sending data back. I guess. So is this powered by like, uh, you know, radioactive material the decay slowly, is it going to keep sending information or is it gonna you know, peter out pretty quick. We think it might last for a long time. It actually has solar panels. The way this thing looks as kind of cool as like a central blob with two like circular solar panels. It looks a little bit like a tie fighter if you took those wings and flatten them out instead of having them be like parallel to the main ship. And so this thing is capable of gathering energy and sort of living for a long time. It's not going to take a whole lot of energy at that time, you know, just to send messages back to Earth. And so a lot of these missions, you know, they have an official life cycle which is pretty short ten years, fifteen years, but sometimes they can go for a very very long time if the electronics is hardy enough and for things. So this doesn't have like a radioactive heat or unit keeping like it's core at a normal temperature. It's all solar power. Yeah, this one is just solar power. It doesn't have a blob of plutonium or something else like thermoelectrically heating it. It show it's relying on photons from the Sun, and you know out there by Jupiter's orbit, this is of course a lot less Sun than there is out here, but it doesn't take that much energy to operate this thing. Once he's out there in this orbit. Unfortunately, when they launched this thing, one of the solar arrays open perfectly and the other one didn't. It opened only like somewhere between eighty and they're not sure, and it didn't like latch open. This thing is supposed to like unfold and then like click into place, so they're not exactly sure how much it didn't open and why it didn't open. They're also like not sure what to do about it. You know, on one hand, it's in okay shape, it's getting a lot of energy. The other hand, you know, maybe they could crack it open a little bit, and they're sort of limited in what they could do. They could like press the button again and try it again, but you know, something else might ki. You never know. Oh, that must have been such a devastating moment at the moment. Do they have any projections for how many years that might cut off the experiment or they're just not thinking about it because maybe they can fix it and they're just going to move on for now. They're just gonna move on for now because things are working and there's always a bit of a buffer. Right when they engineer these things, they always provide more power than they need just in case something like this happens, and so they think it's not going to cut into the operating of the mission. Of course, it is better to have more power and to not have this like weird mechanical failure that always makes you worried. Right, It's like if you get a new car and something breaks the first week, you're like, hold on a second, what's next exactly? Maybe the whole things that disaster, But usually it's fine, Okay, Well, so now we've talked about where it's going to go and what's powering this thing. So let's take a break and then we'll find out what kind of data that's going to collect. All right, and we're back. Okay, So we know that we've got these solar arrays, and those solar arrays are going to get used to power equipment. What kind of equipment is Lucy carrying with her? So Lucy has a few different scientific instruments on board. There's a high resolution camera produced like sort of looking at these things and trying to understand the shape of them, and just like the surface, one big question scientists have is like exactly what is the shape of these things that will help them in their models for how these things are formed. Another is a spectrometer. That's something that very carefully measures the energy of all the photons that you're getting. It tells you like are you getting green photons or red photons. That's very important for understanding like what's inside these things, how much light are they reflecting? What kinds of light? And then they have a disc of lab grown diamonds or a special infrared spectrometer that's able to measure the energy of photons sort of on the longer wavelength. And why would you want to know about that because it doesn't just give you more information about what the asteroid is made out of. Yeah, because as asteroids are cold, right, they're not hot. They don't glow from their own light. The only time you get light from an asteroid is when the sun shines on it, and so it's always reflected light. Another way you can study these objects is from their own very small amount of heat. Remember that everything in the universe does actually give off light, just maybe at temperatures that you can't see with the naked eye. So like the Sun glows at a certain wavelength in the visible because it's super duper hot. The Earth also glows. If you look to the Earth in the infrared, you would see it emitting photons just like you glow, which is why when the predator comes to Earth to hunt humans, it can use its infrared vision to see you, right because of your body heat, and so asteroids also glow, but they tend to glow in the infrared. This is why, like the James Web Telescope is gonna be really cool at discovering exoplanets and planetary disks that are forming in the same way. Using infrared helps you look at these asteroids in their own native light that they are giving off. Okay, and so then you mentioned earlier that asteroids there's what C type, D type and P type asteroids. So the way that they glow can tell you how to can help you differentiate between them, Is that right? That's right. And most of the asteroids that we've had a chance to study in depth are the C type, the ones that are rich in carbon, and most of the meteorites that have landed on Earth are these C type. But there are other types of asteroids, and these other ones tend to have different colors. Some of these the D type and the P type, these are much redder, which means that maybe they have like organic and volatile elements in them. And nobody's ever visited a D type or P type asteroid or gone up close. So by looking at the sort of light that's reflected from it, we can tell, oh, look, it has more carbon, or has less carbon, or it has more of this crazy element in it. Because remember the things absorbed light and reflect light based on their internal chemical composition. The reason the plant is green is because it has chemicals inside of it which tend to reflect green light, and that tells you about something that's going on inside. It tells you about the energy levels of the electrons in those chemicals. So by looking at the different energy of the light that comes off of these things, you can get a sense for what's inside without even digging into it, right, without like taking a sample and analyzing it in the lab. And so like when we say that an asteroid is C type or D type or P type, is it actually like, you know, C type but also twenty five percent D type is in there? Or are they really like pretty homogeneous? They're definitely homogeneous. And in typical astronomy fashion, we have these categories which are blurry right, And really these are about what we see. So we call it C type because it looks a certain way, and we call it D type because it looks a different way, and we suspect that probably means something else is going on underneath, and there are something are the fuzzy like, hm, it's kind of red, what's this one? And so this is just like our categorization just from studying these things through telescopes. And what we need to do is go up there and visit them and get a much more detailed understanding and probably try to overthrow this whole hierarchy of C type and D n P type and get a better understanding for where these guys came from and what's been going on with them. And it is Lucy going to be visiting at least one of each type. Because Lucy is going to be visiting so many asteroids, she will get to observe some D types and some T types and some M types. Yeah. One of the really fun things I think is that Lucy is going to be taking these really close up pictures of the surface of these asteroids to try to count the number of craters. They have this high resolution but black and white camera that's gonna like try to count the number of craters on the surface of these things to get a sense for like how much impacts have there been, what's going on out here? You know, are these things mostly just frozen from the early Solar system or has it a bit a lot of activity? Interesting that should be I can't wait to see the photos. Sometimes I wonder, like our photos mostly just for like the general public, so that you can convince them the money was spent well, because we really like pictures. But it seems like no, these will be helpful photos. They certainly will. And we think also that what's going on in the surface of these things and like how much they've been cracked, how much you can see inside of them from collisions, and how much is going on on them will help answer some of these questions about what happened in the early Solar system, Like was there some big event five million years after the Solar system was formed when Jupiter got its new location and scattered everything and thinks has been mostly frozen since then? Or have there been lots of period of activity things we might not even be aware of that scrambled all of these things and bang them into each other. Fairly recently. So it's sort of like if you dig up fossils and you discover something fairly modern that tells you like the layers have been mixed or something. So just digging in up there, we'll tell us something about the history of the Solar System. It's amazing to me that you can get so much information just from photos and photons. Yeah, like this Patrick Clus pair, they're super excited to understand, like are these surfaces very smooth? Are they totally beat up? You know. Answers to these questions will give scientists insight into like the relative age of the Trojan asteroids and the conditions of the early Solar System. It's going to be really fascinating. And right now it's just a lot of questions. People of all these different theories about how the Solar System might have formed, and they make very different predictions or like what the asteroids should look like. But because we just don't know, we can't tell your theory is crazy, it doesn't match the data because we don't have the data. And we're always in this cycle in physics when the theorists are going crazy with their ideas because we just haven't made the measurements to tell them yes or know about something. And then we finally go out there and we see something. We get to roll out of their ideas and they're like, oh wait, but you didn't measure this, did you. Okay, so now we can go crazy being creative about things you haven't measured. It's like always this game with the gaps. You go through these bottlenecks. Then the idea is proliferate again exactly, and we hope that there will be surprises out there. Lucy's gonna look for like rings and satellites of these asteroids, Like the asteroids themselves might have their own like a little many moons or many rings around them that would be so cute. Today, there's one that might be pronounced Euributes that they think has a satellite around it. This just one kilometer in size, and so when they go visit it, they might get to see its own little baby. Oh, that would be wonderful. It would be a lot of fun. And you know, though, we're gonna learn a lot about these asteroids. We're gonna map the surfaces, we're gonna take these color pictures. We're going to determine the masses and the densities. We're going to study all the craters. Another thing we might do is teach future humans something about us. You mentioned Voyager and they went out into interstellar space. How are we going to teach anyone stuff about us if it's staying here. Well, it's just gonna hang out in the Solar System, right, It's not going to like leave the Solar System or get like crashed into some planetary body. It's just gonna keep orbiting L four and L five basically forever. And so they put on it a golden plaque. The golden plaque contains its launch day, at the positions of the planets at the launch time, what the continents on Earth look like when we launched, and then a bunch of like crazy cultural snippets from you know, what's going on on Earth right now. There's like Beach by Martin Luther King Jr. Some We're from Carl Sagan, songs from the Beatles, of course. And the idea is, you know, maybe in a thousand years some humans will find this and they'll be like, oh, look at this crazy relic from the early days, and it might be our own time capsule of what's going on right now. To inform future archaeologists about our civilization. Okay, so Voyager, we put stuff on there so that non humans could learn about us, But this is so that humans of the future can learn about us. What an awesome responsibility to be one of the people deciding what goes on that golden plaque. I know, and it might be humans. It might be trans humans because humans have transformed by so much. It might be our own ai that have you wiped us out and then find this monument to ourselves. Oh hey, it might be aliens coming to the solar system long after we have eradicated ourselves and finding this monument we built it to ourselves. You had to end it on like humans dying, didn't you? Of course, to get back to that another episode my kids can't listen to. But you know, let's end on a positive note. There's so much to learn about the history of our solar system. As you were asking earlier, you know what discoveries have left to be made. Well, this just highlights how little we have explored even our own solar system. We've done our best by using telescopes and looking through them to try to understand what's going on. But there's a real limit to what you can do without actually going there. So I'm really excited about this Lucy mission going out there and taking these pictures and really examining these solar system fossils to give us a clue about the history and the story of our own solar system. And how exciting to have something to look forward to you for the next decade plus as the data come in. That's right, but it's going to be about as slow as like a James Cameron project. You know, the data is just going to drip in like every five years or so. But you know whom I discovered something new, something revolutionary. Maybe we'll find a relic from some other alien civilization that left us an easter egg in Trojan Camp. We can hope, we can hope. All right. Well, thank you everybody for joining us on this mission to understand the early Solar system and what the Lucy Mission will teach us about it. And thank you very much Kelly for doing us on today's episode. Thanks for having me. I had a lot of fun as always, all right, and enjoy your time with your real live children. I will you do the same, all right. Thanks everybody for listening. Tune in next time, Thanks for listening, and remember that Daniel and Jorge Explain 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.