Katherine de Kleer: Planets, Moons, Asteroids & Life in Our Solar System | Lex Fridman Podcast #184

Lex Fridman 0:00 The following is a conversation with Katherine DeKleer, a professor of planetary science and astronomy at Caltech. Her research is on the surface environments, atmospheres, and thermochemical histories of the planets and moons in our solar system. Quick mention of our sponsors: Fundrise, Blinkist, ExpressVPN, and Magic Spoon. Check them out in the description to support this podcast. As a side note, let me say that this conversation and a few others, quite big ones actually, that are coming up, were filmed in a studio where I was trying to outsource some of the work. Like all experiments, it was a learning experience for me. It had some positives and negatives. Ultimately, I decided to return back to doing it the way I was doing before, but hopefully with a team who can help me out and, uh, work with me long term. The point is, I will always keep challenging myself, trying stuff out, learning, growing, and hopefully improving over time. My goal is to surround myself with people who love what they do, are amazing at it, and are obsessed with doing the best work of their lives. To me, there's nothing more energizing and fun than that. In fact, I'm currently hiring a few folks to work with me on various small projects. If this is something of interest to you, go to lexfriedman.com/hiring. That's where I will always post opportunities for working with me. This is the Lex Fridman Podcast, and here is my conversation with Katherine DeKleer.

Lex Fridman 1:27 Why is Pluto not a planet anymore? Does this upset you or, um, has justice finally been served?

Katherine de Kleer 1:35 (laughs) So I get asked this all the time. I think all- all planetary scientists get asked about Pluto, especially by kids who- we just love for Pluto to still be a planet. Um, but the- the reality is, um, when we first discovered Pluto, it was a- it was a unique object in the outer solar system and we thought, you know, we were adding a planet to the inventory of planets that we had. And then over time, it became clear that Pluto was not a unique large object in the outer solar system, that there were actually many of these. Um, and as we started discovering more and more of them, we realized that the concept of- of Pluto being a planet, um, didn't make sense, unless maybe we added all the rest of them as planets. So you know, you could have imagined actually a different direction that this could've gone where all the other objects that were discovered in that belt, or at least all the ones, let's say, above- above a certain size became planets instead of Pluto being dis- declassified. Um, but we- we're now aware of many objects out there in the outer solar system in what's called the Kuiper Belt that are of the same size, or in some cases, even larger than Pluto. Um, so the- the declassification was really just a realization that it was not in the same category as the other planets in the solar system, and we basically needed to refine our- our definition in such a way that took into account that there's this- this belt of debris out there in the outer solar system of things with a range of sizes. Um...

Lex Fridman 3:05 Is there a hope for clear categorization of what is a planet and not? Do you have a s- Or is it all just gray area? When you study planets, when you study moons, satellites of those planets, is there lines that are cl- clea- that could be cleanly drawn or is it just a giant mess?

Katherine de Kleer 3:21 (laughs)

Lex Fridman 3:21 Is this all like a fluid... let's say not mess, but it's like fluid, uh, of what is a planet, what is a moon of a planet, what is debris, what is asteroids, all that kinda...

Katherine de Kleer 3:32 So there are technically clear definitions that were set down by the IAU, the International Astronomy Union. Um...

Lex Fridman 3:41 Is it size related? Like what are the parameters based on what?

Katherine de Kleer 3:44 So the parameters are that it has to orbit the sun, which was essentially to rule out satellites. Of course this was a not very forward-thinking definition because it technically means that all extra-solar planets, according to that definition, are not planets. Um, so it has to order th- uh, orbit the sun. It has to be large enough that its gravity has caused it to become spherical in shape, um, which also applies to satellites and also applies to Pluto. The third part of the definition is the thing that really rules out everything else which is that it has to has- have cleared out its orbital path.

Lex Fridman 4:14 Mm-hmm.

Katherine de Kleer 4:15 Um, and because Pluto orbits in a belt of material, it doesn't satisfy that stipulation. Uh...

Lex Fridman 4:21 Why didn't it clear out the path? It's not big enough-

Katherine de Kleer 4:23 Right.

Lex Fridman 4:23 ...to knock everybody out of the way?

Katherine de Kleer 4:26 Um, and this actually is not the first time it has happened. So Ceres, when it was discovered, Ceres is the largest asteroid in the asteroid belt, and it was originally considered a planet when it was first discovered, and it went through exactly the same story, history, where people actually realized that it was just one of many asteroids in the asteroid belt region, and then it got declassified to an asteroid, and now it's back to a dwarf planet. So there is a lot of reclassification. So to me, as somebody who studies solar system objects, um, I just personally don't care. My level of interest in something has nothing to do with what it's classified as. So my favorite objects in the solar system are all moons, and frequently when I talk about them, I refer to them as planets because to me, they are planets. They have volcanoes, they have geology, they have atmospheres, they're planet-like worlds. And so the distinction is not super meaningful to me, but I- it is important just for having a- a general framework for- for understanding and talking about things to have a precise definition.

Lex Fridman 5:28 So you don't have a- a special romantic, like, appreciation of a moon versus a planet versus an asteroid? It's just an object that flies out there and doesn't really matter what the categorization is. Like 'cause there's movies about asteroids and stuff, and then there's like- and then there's movies about, you know, the- the moon, whatever, is a really good movie. You know, there's something about moons that, um, that's almost like an outlier. Like you think of- of a moon as a thing that's the secret part...... and the planet is like the more like vanilla regular part? None of that? You don't have any of that?

Katherine de Kleer 6:06 No, I actually do. I really, satellites or the moons are my favorite things-

Lex Fridman 6:10 Yeah.

Katherine de Kleer 6:10 ... in the solar system. And I think part of what you're saying, I agree from maybe a slightly different perspective, which is from the perspective of exploration.

Lex Fridman 6:19 Right.

Katherine de Kleer 6:19 We've spent a lot of time sending spacecraft missions to planets. We had a mission to Jupiter, we had a mission to Saturn, we have plenty of missions to Mars and missions to Venus. I think the exploration of the moons in the outer solar system is the next frontier of solar system exploration.

Lex Fridman 6:35 The, the belt of debris, just real quick, that's out there, is there something incredible to be discovered there? A- again, we tend to focus on the planets and the moons, but it feels like there's probably a lot of stuff out there. And it probably, what is it? It's like a garbage collector from outside of the solar system, isn't it? Like, doesn't it protect from other objects that kind of fly in and... Like what... It, it just feels like it's a cool... You know, you know when you like walk along the beach and look for stuff and like look for... It feels like that's that kind of place where you can find cool, cool weird things. Or it, it... I guess in our conversation today when we think about tools and what science is, uh, studying, is there something to be studied out there? Or we just don't have maybe the tools yet, or there's nothing to be found?

Katherine de Kleer 7:26 There's, there's absolutely a lot to be found. So the material that's out there is remnant material from the formation of our solar system. It's, we don't think it comes from outside the solar system, at least not most of it. Um, but there, there are so many fascinating objects out there and I, I think what you've hit on is exactly right, that we just don't have the tools to study them in detail.

Lex Fridman 7:48 Right.

Katherine de Kleer 7:48 Um, but we, we can look out there and we can see there are different species of, of ice on their surface that tells us about, uh, you know, the chemical composition, the, of the disk that formed our solar system. Some of these objects are way brighter than they should be, meaning they have some kind of geological activity. People have hypothesized that some of these objects have subsurface oceans. You could even stretch your imagination and say some of those oceans could be habitable. Um, but we can't get very detailed information about them because they're so far away. And so I think if any of those objects were in the inner solar system, it would be studied intently and would be very interesting.

Lex Fridman 8:24 So would you be able to design a probe in that like very dense debris field, be able to like hop from one place to another? Is that just outside of the realm of... Like how would you even dev- design devices or sensors that go out there and take pictures and, and land? Do you have to land to truly understand a, a little piece of rock or can you understand it from remotely, like fly up close and remotely observe?

Katherine de Kleer 8:52 You can learn quite a lot from just a flyby and that's all we're currently capable of doing in the outer solar system. Um, the New Horizons mission is a recent example which flew by Pluto and then they had searched for another object that was out there in the Kuiper Belt, any object that was basically somewhere that they could deflect their trajectory to actually flyby. And so they did flyby another object out there in the Kuiper Belt and they take pictures and they do what they can do. And if you've seen images from that mission of Pluto, you can see just how much detail we have compared to just this sort of reddish dot that we knew of before. Um, so you do get an amazing am- amount of information actually from just essentially a high speed flyby.

Lex Fridman 9:35 It always makes me s- sad to think about flybys, that we might be able to f- we might flyby a piece of rock, take a picture and think, "Oh, that looks pretty and cool," and whatever, and that you could study s- certain like composition of the surface and so on, but it's actually teeming with life and we won't be able to see it at first. And it's sad 'cause y- you know like when you're on a deserted island, you wave your hands and the thing flies by and you're trying to get their attention and they probably do the same. Well, in their own way. Bacteria probably, right? But... And we, we miss it. I don't know. For some reason it makes me... It's the, it's the FOMO, it's fear of missing out. (laughs) It makes me sad that there might be life out there and we don't... We're not in touch with it. We're not talking. Yeah. Well, okay. (laughs) Uh, a sad, uh, pause, a Russian philosophical

Lex Fridman 10:32 pause. Okay. What are the tools available to us to study planets and their moons?

Katherine de Kleer 10:37 Oh my goodness. That is such a big question. Um, so among the field of astronomy, so planetary science broadly speaking, well, it falls kind of at the border of astronomy, geology, climate science, chemistry and even biology. So it's kind of on the border of many things, but, um, part of it falls under the heading of astronomy. And among the things that you can study with telescopes, like solar system moons, um, and planets, the solar system is really unique in that we can actually send spacecraft missions to the objects and study them in detail. And so I think that's, that's the kind of type of tool that is, that people are most aware of, that's most popularized, these amazing NASA missions that either you fly by the object, you orbit the object, you land on the object. Potentially you can talk about digging into it, drilling, um, trying to detect tectonic tremors on its surface. Um, the types of tools that I use are primarily telescopes. And so I, my background is in astrophysics and so I actually got into solar system science from astronomy, not from, you know, a childhood fascination with spacecraft missions, which is actually what... A lot of planetary scientists became planetary scientists because of childhood fascination with spacecraft missions, which is kind of interesting for me to talk to people and see that trajectory. I kind of came at it from the fascination with telescopes angle.

Lex Fridman 12:03 All right. So you like telescopes-

Katherine de Kleer 12:04 Um-

Lex Fridman 12:04 ... not rockets? Or at least you were-

Katherine de Kleer 12:06 When I was a kid, it was looking at the stars and playing with telescopes that really fascinated me and that's how I got into this. Um, but telescopes, it's...... amazing how much detail and how much information you can get from telescopes today. You can resolve, um, individual cloud features and watch them kind of sheer out in the atmosphere of Titan. You can literally watch volcanoes on Io change from day to day as the, the lava flows expand. Um, so, and then, you know, with spectroscopy you get compositional information on all these things and it's, um... When I started doing solar system astronomy, I was surprised by how much detail and how much information you can get even from Earth, and then as well as from orbit, like the Hubble Space Telescope or the James Webb.

Lex Fridman 12:59 So with a telescope, you can, um... I mean, how much information can you get about volcanoes, about storms, about sort of weather? Just so we kind of get a, a sense like what, uh, resolution we're talking about.

Katherine de Kleer 13:15 Well, in terms of resolution, so at a, you know, on a given night, if I go and take a picture of Io and its volcanoes, you can sometimes see at least a dozen different volcanoes. You can see the infrared emission coming off of them and resolve them, separate them from one another on the surface, uh, and, and actually watch how, how the heat coming off of them changes with time. And I think this time variability aspect is one of the big advantages we get from telescopes. So you send a spacecraft mission there, and you get an incredible amount of information over a very short time period. But for some science questions, you need to observe something for 30 years, 40 years. Like, let's say you want to look at the moon Titan, which has one of the most interesting atmospheres in the solar system. Um, its orbital period is 29, 30 years. And so if you want to look at how its atmospheric seasons work, you have to observe it over that long of a time period, and you're not going to do that with a spacecraft. But you can do it with telescopes.

Lex Fridman 14:15 Can we, uh, just zoom in on certain things? Like, let's talk about Io, which is the moon of, uh, Jupiter.

Katherine de Kleer 14:21 Right.

Lex Fridman 14:22 Okay. It's like epic. There's like volcanoes all over the place. It's, um... From a distance, it's awesome. So can you tell me about this moon? And you're sort of, um, a scholar of many planets and moons, but that one kind of stood out to me. So why is that an interesting one?

Katherine de Kleer 14:42 For so many reasons. But, uh, Io is, it is the most volcanically active object in the solar system. It has hundreds of active volcanoes on it. Um, it has volcanic plumes that go hundreds of kilometers up above its surface. It puts out more volume of magma per volcano than volcanoes on Earth today. Um, but I think, to me, the reason that it's most interesting is be- is as a laboratory for understanding planetary processes. Um, so one of the broad goals of planetary science is to put together a sort of more general and coherent framework, um, for how planets work in general. Our current framework, you know, it started out very Earth-centric. We start to understand how Earth volcanoes work. Um, but then when you try to transport that to somewhere like Io that doesn't have an atmosphere, which makes a, or does- has a very tenuous atmosphere, which makes a big difference for how the, the magma degasses. Um, for something that's really small, for something that has a different heat source, for something that's embedded in another object's magnetic field, uh, the kind of intuition we have from Earth doesn't apply. And so broadly, planetary sciences is trying to broaden that framework so that you have a kind of narrative that all, you can understand how each planet became different from eith- every other planet. And I'm already making a mistake. When I say planet, I mean planets and moons. Like I said, I see-

Lex Fridman 16:06 Okay.

Katherine de Kleer 16:06 ... the moons as planets.

Lex Fridman 16:08 As, as planets?

Katherine de Kleer 16:09 Um...

Lex Fridman 16:09 Yeah. I actually already noticed that you didn't introduce Io as the moon of Jupiter. You, you completely, you, uh, you kind of ignored the fact that Jupiter exists. (laughs)

Katherine de Kleer 16:19 (laughs) .

Lex Fridman 16:19 It's like, "Let's focus on the..." (laughs) Yeah. Okay so, uh... And you also didn't mention Europa, which I think is the f- is, is that the most famous moon of Jupiter? Is that the one that gets attention because it might have life?

Katherine de Kleer 16:33 It's, exactly. Yeah.

Lex Fridman 16:34 Okay. But you're, uh, but to you, Io's also beautiful. I, what's the difference between (laughs) volcanoes on, uh, Io versus Earth? You said atmosphere makes a difference. What, uh, what-

Katherine de Kleer 16:45 Yeah. Um, the, the heat source plays a big role. So, um, many of the moons in the outer solar system are heated from gravitationally by tidal heating. Um, and I'm happy to describe what that is or not.

Lex Fridman 16:58 Well yeah, please. What's tidal? (laughs) Yes. Yes, please.

Katherine de Kleer 17:01 Okay. Um, so tidal heating is, it's... If you want to understand and contextualize planets and moons, you have to understand their heat sources. Um, so for Earth, we have radioactive decay in our interior, as well as residual heat of formation. But for satellites, um, tidal heating plays a really significant role, and in particular, in driving geological activity on satellites. Um, and potentially making those subsurface oceans in places like Europa and Enceladus habitable. Um, and so the way that that works is if you have multiple moons and their orbital periods are integer multiples of one another, that means that they're always encountering each other at the same point in the orbit. Um, so if they were on just random orbits, they'd be encountering each other at random places and the gravitational effect between the two moons would be canceling out over time.

Lex Fridman 17:54 Mm-hmm.

Katherine de Kleer 17:54 But because they're always meeting each other at the same point in the orbit, uh, those gravitational interactions add up coherently. Um, and so that tweaks them into eccentric orbits. Uh-

Lex Fridman 18:06 What's an eccentric orbit?

Katherine de Kleer 18:08 So eccentric orbit or elliptical orbit, it just means non-circular.

Lex Fridman 18:12 Right.

Katherine de Kleer 18:12 So a deviation from a circular orbit. And that means that, you know, for Io or Europa, at some points in their orbit, they're closer to Jupiter and at some points in their orbit, they're farther away. And so when they're closer, they're stretched out.-in a sense but, but literally just not very stretched out, like a couple hundred meters, something like that. And then when they're farthest away, they're less stretched out-

Lex Fridman 18:35 Mm-hmm.

Katherine de Kleer 18:35 ... and so you actually have the shape of the object deforming over the course of the orbit and these-

Lex Fridman 18:40 Wow.

Katherine de Kleer 18:40 ... orbits are, like, just a couple of days and so that, in the case of Io, that is literally sufficient friction in its mantle to melt the rock of its mantle, and that's what generates the magma.

Lex Fridman 18:52 That's, that's the source of the-

Katherine de Kleer 18:54 Yeah.

Lex Fridman 18:55 ... the magma. Okay, so why is Euro- so Europa is, I thought there was, like, ice and oceans underneath kind of thing, so why is Europa not getting the friction?

Katherine de Kleer 19:05 It is. It's just a little bit farther away from Jupiter and then Ganymede is also in the orbital resonance so it's a, a three object orbital resonance in the Jupiter system. Um-

Lex Fridman 19:14 Okay.

Katherine de Kleer 19:14 But we have these sorts of orbital resonances all over the solar system and also in exoplanets. Um, so for Europa, basically because it's farther from Jupiter, the effect is not as extreme but you do still have heat-

Lex Fridman 19:27 Okay.

Katherine de Kleer 19:27 ... generated in its interior in this way and that may be driving, could be driving hydrothermal activity at the base of its ocean which obviously would be a really valuable thing-

Lex Fridman 19:37 Ooh.

Katherine de Kleer 19:37 ... for life.

Lex Fridman 19:38 Cool.

Katherine de Kleer 19:38 Um ...

Lex Fridman 19:39 So it's like heating up the ocean a little bit?

Katherine de Kleer 19:41 Heating up the ocean a little bit and specifically in these, like, hydrothermal vents where we see really interesting, uh-

Lex Fridman 19:48 Yeah.

Katherine de Kleer 19:48 ... life evolve in the bottom of-

Lex Fridman 19:50 Yeah.

Katherine de Kleer 19:50 ... Earth's oceans.

Lex Fridman 19:51 That's cool. Okay, so what's, uh, what's Io, um, what else? So we know the source is this friction, but there's no atmosphere. I'm trying to get a sense of what it's like if, if, if you and I were to visit Io, uh, like, wha- what would that look like, what would it feel like?

Katherine de Kleer 20:07 (laughs)

Lex Fridman 20:08 Is it, is the entire thing covered in basically, uh, volcanoes?

Katherine de Kleer 20:15 Um, so it's, it's interesting because there's very little atmosphere, the surface is actually really cold, very far below freezing on the surface when you're away from a volcano, but the volcanoes themselves are over 1,000 degrees, or the, the magma when it comes out is over 1,000 degrees and so ...

Lex Fridman 20:31 But it does come to the surface, the magma?

Katherine de Kleer 20:33 It does, yep.

Lex Fridman 20:35 In particular places? Whoa, that probably looks beautiful. So like, so it's fr- it's frozen, not ice. Like what is, uh, it's rock, it's really cold rock, and then you just have this, like, s- uh, what is, what does that loo- what would that look like with no atmosphere? Would that, uh, would there be smoke? What, what does it look like? What, is it just magma, like just red, uh, yellow, like, liquidy things?

Katherine de Kleer 21:03 Uh, it's-

Lex Fridman 21:03 Or-

Katherine de Kleer 21:04 ... it's black. It's black and, and red I guess. Like, think of, um, the type of magma that you see in Hawaii. So different types of magma flow in different ways, for example. So in somewhere like Io, the magma is really hot and so it, it will flow out in sheets because it has really low viscosity.

Lex Fridman 21:21 Mm-hmm.

Katherine de Kleer 21:22 Um, and I think the, the lava flows that we've been having in, in Hawaii over the past couple of years are probably a decent analogy, although um, Io's magmas, lavas are even more fluid and, and faster moving.

Lex Fridman 21:35 How fast are-

Katherine de Kleer 21:36 Um-

Lex Fridman 21:36 Like what, uh, how fa- like if you, uh, by the way, sorry. Through the telescope, are you tracking at what time scale? Like, what, the fr- every frame is how, how far apart if you're looking through a telescope? Are we talking about seconds, are we talking about, um, days, months? When you kind of track, try to get a picture of what the surface might look like, what's the frequency?

Katherine de Kleer 21:59 So it depends a little bit on what you want to do. I, ideally every night, um, but you could take a frame every second and see how things are changing. The, the problem with that is that for things to change on a one-second time scale, you, to actually see something change that fast, you have to have super high resolution.

Lex Fridman 22:19 Okay.

Katherine de Kleer 22:19 The spatial resolution we have is a couple hundred kilometers and so-

Lex Fridman 22:23 Okay, got it.

Katherine de Kleer 22:23 ... things are not changing on those scales over one second unless you have something really crazy happening.

Lex Fridman 22:30 So if you get, you, if you get a telescope closer to Io, if you get a, or a camera closer to Io, would you be able to understand something, is that something of interest to you? It, uh, would you be able to understand something deeper about these volcanic eruptions and how magma flows and just the, like, the rate of the magmas or is it basically enough to have the kilometer resolution? To get a sense-

Katherine de Kleer 22:55 No way. We want to go there.

Lex Fridman 22:57 You want to go-

Katherine de Kleer 22:58 Absolutely.

Lex Fridman 22:58 You, you want to go to Io?

Katherine de Kleer 22:59 I mean, I don't want to go there personally but I want to send a spacecraft mission there, absolutely, yeah.

Lex Fridman 23:03 Why, why are you scared?

Katherine de Kleer 23:04 Why am I scared? (laughs)

Lex Fridman 23:05 Oh, you mean you don't (laughs) , uh, like hu- uh...

Katherine de Kleer 23:09 I don't want to go there as a human.

Lex Fridman 23:10 As a human, so human-

Katherine de Kleer 23:11 I want to send a robot there-

Lex Fridman 23:12 I see.

Katherine de Kleer 23:13 ... to look at it though.

Lex Fridman 23:13 This is again, everybody's discriminating against robots, this is, uh, not-

Katherine de Kleer 23:17 (laughs)

Lex Fridman 23:17 But it's fine. Uh, but it's not hospitable to, uh, humans in any way, right? Just very cold and very hot?

Katherine de Kleer 23:24 It's very cold, um, the atmosphere is composed of sulfur dioxide so-

Lex Fridman 23:30 Okay, got it.

Katherine de Kleer 23:30 ... you could breathe it, there's no pressure. I mean, it's kind of all the same things you talk about, one talks about about Mars only worse. The atmosphere's still a thousand times less dense than Mars is. Um, and the radiation environment is terrible because you're embedded deep within Jupiter's magnetic field and Jupiter's magnetic field is full of charged particles that have all come out of Io's volcanoes actually. Um, so, uh, Jupiter's magnetic field strips all this material out of Io's atmosphere-

Lex Fridman 24:01 Mm-hmm.

Katherine de Kleer 24:02 ... and that populates its entire magnetosphere and then that material comes back around and hits Io and, and spreads throughout the system actually. It's just, it's like, uh, Io is the massive polluter of the Jupiter system.

Lex Fridman 24:14 (laughs)

Katherine de Kleer 24:14 (laughs)

Lex Fridman 24:14 Okay, cool. Uh, so what, uh, what does studying Io, uh, teach you about volcanoes on Earth or vice versa? Is, is, in the difference of the two, what, uh, insights can you mine out?... that might be interesting in some way.

Katherine de Kleer 24:34 Yeah. It's, we try to port the tools that we use to study Earth volcanism to Io and it works to some extent, but it is challenging, um, because the situations are so different. And the compositions are really different. When you talk about outgassing, you know, Earth volcanoes outgas primarily, uh, water and carbon dioxide, and then sulfur dioxide is the, the third most abundant gas.

Lex Fridman 25:00 Mm-hmm.

Katherine de Kleer 25:00 And on Io, the water and carbon dioxide are not there.

Lex Fridman 25:05 Right.

Katherine de Kleer 25:05 Um, either it didn't form with them or it lost them, we don't know. And so, so the chemistry of how the magma outgasses is completely different. Um, but the, the kind of one, to me, most interesting analogy to Earth is that, um ... So Io, as I've said, it has these really low viscosity magmas. They, the, the lava spreads really quickly across its surface. It can put out massive volumes of magma in relatively short periods of time. And that sort of volcanism is not happening anywhere else in the solar system today, but literally every terrestrial planet and the moon, um, had this, what we call very effusive volcanism early in their history.

Lex Fridman 25:48 Okay, so this is almost like a little glimpse into the early history of Earth.

Katherine de Kleer 25:52 Yeah.

Lex Fridman 25:52 Okay, cool. So, uh, what are the chances that, uh, a volcano on Earth destroys all of human civilization? Maybe I wanted to sneak in that question.

Katherine de Kleer 26:01 Yeah, a volcano on Earth, um-

Lex Fridman 26:06 Do you think about that kind of stuff when you just study volcanoes elsewhere? 'Cause isn't it kind of humbling to see something so powerful and so hot, like, so unpleasant for humans, and then you realize we're sitting on many of them here?

Katherine de Kleer 26:18 Right. Yeah. Yellowstone is a classic example. I, I don't know what the chances are of that happening. My intuition would be that the chances of that are lower than the chances of us getting (laughs) wiped out by some other means.

Lex Fridman 26:33 Okay.

Katherine de Kleer 26:33 But, but in the time, you know-

Lex Fridman 26:35 That's comforting.

Katherine de Kleer 26:35 ... that, that maybe it'll happen eventually that there will be one of these massive volcanoes on Earth, but we'll probably be gone by then by some other means.

Lex Fridman 26:42 (laughs)

Katherine de Kleer 26:42 Not to sound bleak, but ... (laughs)

Lex Fridman 26:43 (laughs) That's very comforting. Okay,

Lex Fridman 26:46 so can we talk about, um, Europa? Is there, um ... So maybe can you talk about the intuition, the hope that people have about life being on Europa? Maybe also what are the things we know about it? What are the things to you that are interesting about that particular moon of Jupiter?

Katherine de Kleer 27:08 Sure. Yeah, Europa is, from many perspectives, one of the really interesting places in the solar system among the solar system moons. So there are a few... There, there has, there's a lot of interest in looking for or understanding the potential for life to evolve in the subsurface oceans. I think it's fairly widely accepted that the chances of life evolving on the surfaces of really anything in the solar system is very low. Um, the radiation environment is too harsh, um, and there's, there's just not liquids on the surface of most of these things, and it's canonically accepted that liquids are required for life. Um, and so the subsurface oceans, in addition to maybe Titan's atmosphere, the subsurface oceans of the icy satellites, uh, are one of the most plausible places in the solar system for life to evolve. Um, Europa and Enceladus are interesting because for many of the big satellites, so Ganymede and Callisto, also satellites of Jupiter, also are thought to have subsurface oceans. But, um they are... So they have these ice shells and then there's an ocean underneath the ice shell. But on those moons, or on Ganymede, we think that there's another ice shell underneath, and then there's rock. And the reason that that is a problem for life is that your ocean is probably just pure water because it's trapped between two big shells of ice. Uh, so Europa doesn't have this ice shell at the bottom of the ocean we think, and so the water and rock are in direct interaction. And so that means that you can basically dissolve a lot of material out of the rock. You potentially have this hydrothermal activity that's injecting energy and nutrients for life to survive. And so this rock-

Lex Fridman 28:54 It's so cool.

Katherine de Kleer 28:54 ... water interface is, is considered really important for the potential habitability.

Lex Fridman 29:02 As a small aside, you kind of said that it's canonically assumed that, uh, li- water is required for life. Is it possible to have life o- like, in a volcano? I remember people were s- a- d- like a na- uh, National Geographic program or something kind of hypothesizing that you can really have life anywhere. So as long as there's a source of heat, a source of energy, do you think it's possible to have life in a volcano? Like, no water?

Katherine de Kleer 29:34 I think anything's possible (laughs) .

Lex Fridman 29:37 (laughs) Okay. It's one of those things.

Katherine de Kleer 29:38 I think so, water... It doesn't have to be water. I, that's sort of, I, you can tell as you identified, I phrased that really carefully. "It's canonically accepted-"

Lex Fridman 29:47 Yeah.

Katherine de Kleer 29:47 "... that..." Um, because we recognize that, you know, scientists recognize that we have no idea what broad range of life could be out there and all we really have is our biases of life as we know it. But for life as we know it, it's very helpful to have or even necessary to have some kind of liquid and preferably a, a polar solvent that can actually dissolve molecules, something like water. So the case of liquid methane on Titan is less ideal from that perspective. But, you know, liquid magma, if it stays liquid long enough for life to evolve, you have a heat source, you have a liquid, you have nutrients. In theory, that checks your three classic astrobiology boxes. Um... (laughs)

Lex Fridman 30:28 (laughs) That'd be fascinating. I mean, it'd be fascinating if it's possible to detect it easily. How, uh, would we detect if there is life on Europa?... is, um, is it possible to do in a non-contact way from a distance through telescopes and so on? Or, uh, do we need to send robots and do some drilling?

Katherine de Kleer 30:51 I think realistically you need to do the drilling. Um, there's... So Europa also has these long tectonic features on its surface where it's thought that, um, there's potential for water from the ocean to be somehow making its way up onto the surface, and you could imagine some out there scenario where there's bacteria in the ocean, it's somehow working its way up through the ice shell, it's spilling out on the surface, it's being killed by the radiation-

Lex Fridman 31:18 Mm-hmm.

Katherine de Kleer 31:19 ... but your instrument could detect some spectroscopic signature of that dead bacterium. But that's-

Lex Fridman 31:24 Hm.

Katherine de Kleer 31:24 ... you know, that's many ifs and assumptions that I-

Lex Fridman 31:26 That's a hope because then you don't have to do that much drilling, you can collect from the surface.

Katherine de Kleer 31:31 Right, or even-

Lex Fridman 31:32 Skeletons of bacteria.

Katherine de Kleer 31:32 ... I'm thinking even remotely, um, you know.

Lex Fridman 31:34 Oh, remotely. Yeah. That's sad that there's a s- single cell civilization living underneath all that ice trying, trying, trying to get up, trying to get out.

Katherine de Kleer 31:47 So Enceladus gives you a slightly better chance of that because Enceladus is a, is a moon of Saturn.

Lex Fridman 31:55 Mm-hmm.

Katherine de Kleer 31:55 And it's broadly similar to Europa in some ways, it's an icy satellite, it has a subsurface ocean that's probably in touch with the rocky interior, but it has these massive geysers at its south pole where it's spewing out material-

Lex Fridman 32:09 Nice.

Katherine de Kleer 32:09 ... that appears to be originating all the way from the ocean. And so in that case, you could potentially fly through that plume and scoop up that material and hope that at the velocities you'd be scooping it up, you're not destroying any signature of the life you're looking for. Um, but let's say that you have some ingenuity and can come up with a way to do that, you know, it potentially gives you a more direct opportunity at least to try to measure those bacteria directly.

Lex Fridman 32:39 Uh, can, can you tell me a little more, uh, on, uh, how do you pronounce it? Uh, Celad-

Katherine de Kleer 32:45 Enceladus.

Lex Fridman 32:45 Enceladus? (laughs) Can you tell me a little bit more about Enceladus? Like, uh, we've been talking about way too much about Jupiter. Saturn doesn't get enough love.

Katherine de Kleer 32:55 Not enough really.

Lex Fridman 32:57 Not enough. (laughs) Uh, Saturn doesn't get as much love, so what's, what's Enceladus? Um, is that the most exciting moon of, uh, Saturn?

Katherine de Kleer 33:05 Depends on your perspective. Um, it's, it's very exciting from a astrobiology perspective. I think Enceladus and Titan are the two most unique and interesting moons of Saturn, they definitely both get the most attention also from the life perspective. Um...

Lex Fridman 33:22 So what's more likely, uh, Titan or Enceladus for life? If you were to, uh, bet all your money in terms of like investing, which to investigate, what, what are the difference between the two that are interesting to you?

Katherine de Kleer 33:37 Yeah. So the potential for life in each of those two places is very different. So Titan is the, the one place in the solar system where you might imagine, again all of this is so speculative, but you might imagine life-

Lex Fridman 33:51 Right.

Katherine de Kleer 33:51 ... evolving in the atmosphere. So the, from a-

Lex Fridman 33:54 Whoa.

Katherine de Kleer 33:54 ... a biology perspective, Titan is interesting because it forms complex organic molecules in its atmosphere. It has a dense atmosphere, it's actually denser than Earth's, it's the only moon that has-

Lex Fridman 34:05 What?

Katherine de Kleer 34:06 ... an atmosphere denser than Earth's.

Lex Fridman 34:07 That's cool.

Katherine de Kleer 34:08 And it's got tons of methane in it. What happens is that methane gets irradiated, it breaks up and it reforms with other things in the atmosphere. It makes these complex organic molecules and it, it's effectively doing prebiotic chemistry in the atmosphere.

Lex Fridman 34:23 While still being freezing cold?

Katherine de Kleer 34:25 Uh, yes.

Lex Fridman 34:27 Okay. What, what would that be like? Would that be pleasant for humans to, to hang out there? Is it just really cold?

Katherine de Kleer 34:34 There's nowhere in the solar system that would be pleasant-

Lex Fridman 34:36 Okay.

Katherine de Kleer 34:36 ... for humans. Um, it would be cold, you couldn't breathe the air, um...

Lex Fridman 34:40 But colonization wise? If there's an atmosphere, isn't that a big plus?

Katherine de Kleer 34:44 Sure.

Lex Fridman 34:44 Or still a ton of radiation? Okay, so (laughs) okay, so Titan... That, that's a really nice feature that the life could be in the atmosphere 'cause then it's, it's that might be remotely observable or certainly is more accessible if you visit. Okay. So, uh, well what about Enceladus? So that would be still in the ocean?

Katherine de Kleer 35:08 Right. And Enceladus has the advantage, like I said, of spewing material out of its south pole so you could collect it. But it has the disadvantage of the fact that we don't actually really understand how its ocean could stay froz- or sorry could stay globally liquid over the age of the solar system. And so there are some models that say that it's going through this, um, cyclical evolution where the ocean-

Lex Fridman 35:35 Oh.

Katherine de Kleer 35:35 ... freezes completely and thaws completely and the orbit sort of, um, oscillates in and out of, of these eccentricities. Um, and in that case, the potential for life ever occurring there in the first place is a lot lower because if you only have an ocean for 100 million years, is that enough time? Um...

Lex Fridman 35:54 And it also means there might be mass extinction events if it does occur.

Katherine de Kleer 35:58 Right.

Lex Fridman 35:59 And then it just freezes.

Katherine de Kleer 36:00 Yes.

Lex Fridman 36:00 Again, very sad. Man, I'm... This is very depressing, all the (laughs) like slaughter of life elsewhere.

Lex Fridman 36:07 How unlikely do you think life is on Earth? So when you look, when you study other planets and you study the contents of other planets, does that give you a perspective on, um, the origin of life on Earth? Which again, is full of mystery in itself. Not the evolution but the origin. The first springing to life, s- like from, from nothing to life. From the basic ingredients to life. I, I guess another way of asking it is how unique are we?

Katherine de Kleer 36:40 Yeah. It's a great question, and it's one that just scientifically, we don't have an answer to. We don't even know how many times life evolved on Earth, if it was only once or if it happened independently a thousand times in different places. Uh, we don't know whether it's happened anywhere else in the universe, although it, it feels absurd to believe that we are the only life that evolved in the entire universe, but it's conceivable. We just have just no real information. We don't understand really how life came about in the first place on Earth.

Lex Fridman 37:16 I mean, so if you look at the Drake equation that tries to estimate how many alien civilizations are out there, planets have a big part to play in that equation. If you were to bet money, uh, in terms of the odds of, uh, origins of life on Earth, I mean this all has to do with how special and unique is Earth. H- what you land in terms of the number of civilizations has to do with how unique the rare Earth hypothesis is, how rare and special is Earth, how rare and special is the solar system. Like if you had to bet all your money on a, on a completely unscientific question... Well, no, actually, it's actually rigorously scientific, we just don't know a lot of things in that equation. There's a lot of mysteries about that. And it's slowly becoming better and better understood in terms of exoplanets, in terms of how many solar systems are out there, where there's planets, they're Earth-like planets, that's getting better and better understood. What's your sense from that perspective, um, how many alien civilizations are out there?

Katherine de Kleer 38:23 (laughs) So-

Lex Fridman 38:24 Zero or one plus?

Katherine de Kleer 38:25 You're right that the equation is, is being better understood, but you're really only talking about the first three parameters in the equation or something, you know, how many stars are there? How many planets per star? And then we're just barely scratching the surface of what fraction of those planets might be habitable. The rest of the terms in the equation are like, how likely is life to evolve-

Lex Fridman 38:45 Right.

Katherine de Kleer 38:45 ... given habitable conditions, how likely is it to survive? All these things. Um, there are all these huge unknowns. Actually, I, I remember when I first saw that equation. I think I was... I think it was my first year of college, and I thought, "This is ridiculous. This is-"

Lex Fridman 39:02 (laughs)

Katherine de Kleer 39:02 "... A, common sense that didn't need to give a b- give a name."

Lex Fridman 39:05 Yeah.

Katherine de Kleer 39:05 You know? Um, and B, just a bunch of unknowns. It's like putting our ignorance together in one equation. But I- I've actually... Now I understand this equation, you know, it's not something we'll ever necessarily have the answer to, it's- it just gives us a framework for having the exact conversation we're having right now.

Lex Fridman 39:23 Mm-hmm.

Katherine de Kleer 39:23 And I think that's how it was intended in the first place when it was, was put into writing, was to, to give people language to communicate about the factors that go into the potential for aliens to be out there and for us to find them. Um, I, I would put money on there being aliens. I would not put money on us having definitive evidence of them in my lifetime.

Lex Fridman 39:50 Well, definitive is a funny, is a funny word.

Katherine de Kleer 39:53 (laughs)

Lex Fridman 39:53 Because, uh, my sense is... This is the saddest part for me, is my sense in terms of intelligent alien civilizations, I feel like we're so... We're so self-obssessed that we literally would not be able to detect them, even when they're, like, in front of us. Like, like, trees could be aliens, but just their intelligence could be, um, realized on a scale, on a time scale or a physical scale that we're not appreciating. Like, trees could be way more intelligent than us. I don't know. This is just a dumb example. Could be rocks. Rock... Or it could be things like the, uh... Oh, this, I love this, this is Dawkins memes, it could be that ideas are the s- the, i- like, ideas we have, like, where do ideas come from? Where do thoughts come from? Maybe thoughts are the aliens, or maybe thoughts is the actual mechanisms of communication in, uh, physics, right? So it's just like we think of thoughts as something that springs up from neurons firing, but where the hell did they come from? And now, what about consciousness? Maybe consciousness is the communication here. I think... It sounds like ridiculous, but like we're so self-centered on this, uh, spacetime communication in physical space using like written language, like spoken with audio. (laughs) would you... On a time scale that's very specific, on a physical scale that's very specific. Uh, so yeah, so I, I, I tend to think that, uh... B- bacteria will probably recognize, like, like moving organisms will probably recognize, but when that forms itself into intelligence, most likely it'll be robots of some kind, 'cause we won't be meeting the origins, we'll be meeting the creations of those intelligences.

Katherine de Kleer 41:49 Hmm.

Lex Fridman 41:49 We just would not be able to, uh, to appreciate it, and that's the saddest thing to me. That, uh, we... W- yeah. We... We're not... We're too dumb (laughs) to see aliens. Uh, like, we're too... We kind of think like look at the progress of science, we've accomplished so much. The sad thing, it could be that we're just like in the first .0001% of understanding anything. It's humbling. Okay.

Katherine de Kleer 42:15 I hope that's true.

Lex Fridman 42:16 You hope that-

Katherine de Kleer 42:16 Because I feel like we're very ignorant as a species, and I hope that our current level of knowledge only represents the .001% of what we will someday achieve. That actually feels optimistic to me.

Lex Fridman 42:29 (laughs) Well, that... I feel like that's easier for us to comprehend in the space of biology and not as easy to comprehend in the space of physics, for example. Because we have a sense that, like, we have... It like... Uh, if you, if you talk to theoretical physicists-... they have a sense that we understand the basic laws that form the nature of reality, of our universe. But it... So there's much more conf- like, physicists are much more confident. (laughs) Biologists are like, "Uh..." (laughs) "This is a squishy mess. We're doing our best." Uh, physicists, th- yeah, but I would be... It'd be fascinating to see if physicists themselves would also be humbled by there being... Like, what the hell is dark matter and dark energy? What- what the hell is the, uh, n- not- not just the origin of the... not just the big bang, but, uh, everything that happened since the big bang? A lot of things that happened since the big bang we have no ideas about except basic models of physics.

Katherine de Kleer 43:28 Right. Or what happened-

Lex Fridman 43:29 What the hell is-

Katherine de Kleer 43:29 ... before the big bang.

Lex Fridman 43:30 What ha- yeah, yeah, what happened before, or- or what's happening inside a black hole. Why is there a black hole at the center of our galaxy? Can somebody answer this? A super massive black hole, nobody knows how it started, and they seem to be, like, in the middle of all galaxies. Um, so that could be a portal for aliens to communicate through consci- okay. Um, all right, back to planets.

Katherine de Kleer 43:51 (laughs)

Lex Fridman 43:51 (laughs) How, um... What's your favorite... Outside of Earth, what's your favorite planet or moon? Maybe outside of the ones... Well, first, have we talked about it already? Or... And then if we did mention it, what's the one outside of that?

Katherine de Kleer 44:06 Oh, gosh, I have to come up with another favorite that's not Io?

Lex Fridman 44:09 Oh, Io's the favorite.

Katherine de Kleer 44:10 Oh, absolutely.

Lex Fridman 44:10 Why is Io the favorite?

Katherine de Kleer 44:12 I mean, basically everything I've- I've already said. It's just such a- an amazing and unique object. Um, but on, I guess, a personal note, it's probably the object that made me become a planetary scientist. It's the first thing in the solar system that really deeply captured my interest. Um, and when I started my PhD, I wanted to be an astrophysicist working on things like galaxy evolution. Um, and sort of slowly... I had done some projects in the solar system, but Io is the thing that, like, really caught me into doing solar system science.

Lex Fridman 44:53 Okay, let's- let's leave, uh, moons aside. What's your favorite planet? It sounds like you like moons better than planets. So let's, uh...

Katherine de Kleer 45:02 That's accurate. Uh, but the planets are- are fascinating. I think... You know, I find the planets in the solar system really fascinating. What I like about the moons is that they... there's so much less that is known. There's still a lot more discovery space, and the questions that we can ask are- are still the- the bigger questions.

Lex Fridman 45:22 Gotcha.

Katherine de Kleer 45:23 Um, which, you know, I... And maybe I'm being unfair to the planets because we are still trying to understand things like, was there ever life on Mars? And that is a huge question, and one that we've sent numerous robots to Mars to try to answer. So, maybe I'm being unfair to the planets, but-

Lex Fridman 45:39 (laughs)

Katherine de Kleer 45:39 ... but there is certainly quite a bit more information, uh, that we have about the planets than the moons. But, I mean, Venus is- is a fascinating object. So, I like the objects that lie at the extremes. I think that if we can make a- a sort of theory or- or, like I've been saying, framework for understanding planets and moons that can incorporate even the most extreme ones, then, you know, those are the things that really test your theory and test your understanding. And so they- they've always really fascinated me. Not so much the nice habitable places like Earth, but these extreme places like Venus that have, um, sulfuric acid clouds and just incredibly hot and dense surfaces. And Venus, of course, I- I love volcanism for some reason, and- and Venus has... probably has volcanic activity. Definitely has in the recent past. Maybe has ongoing today.

Lex Fridman 46:36 Uh, what do you make of the news, and maybe you can update it, in terms of life being discovered in the atmosphere of- of Venus? Is that... Sorry. Okay, you have opinion- I can already tell you have opinions. Was that fake news? I got excited when I saw that. What's the... what's the final, uh... Is there life on Venus?

Katherine de Kleer 46:56 So, the detection that was reported-

Lex Fridman 46:58 Yeah.

Katherine de Kleer 46:58 ... was the detection of the molecule phosphine.

Lex Fridman 47:00 Mm-hmm.

Katherine de Kleer 47:01 Um, and they said that they tried every other mechanism they could think of to produce phosphine, and they... none of... no mechanism worked, and then they said, "Well, we know that life produces phosphine." And so that was sort of the-

Lex Fridman 47:18 Gotcha.

Katherine de Kleer 47:18 ... the train of logic, and, um, I don't personally believe that phosphine was detected in the first place.

Lex Fridman 47:26 Okay, so then, I mean, this is just one study, but I, as a layman-

Katherine de Kleer 47:31 Mm-hmm.

Lex Fridman 47:31 ... I'm skeptical, a little bit, about tools that sense the contents of an atmospher- like, uh, contents of a- an atmosphere from... remotely, and making conclusive statements about life.

Katherine de Kleer 47:47 Oh, yeah. Well, that connection that you just made, the contents of the atmosphere to the life-

Lex Fridman 47:51 Yeah.

Katherine de Kleer 47:52 ... is- is a tricky one. And yeah, I know that that claim received a lot of criticism for the lines of logic that went from detection to, uh, to claim of life. Even the detection itself, though, di- doesn't- doesn't meet the sort of historical scientific standards of-

Lex Fridman 48:12 Got it.

Katherine de Kleer 48:12 ... of a detection. Um, the... it was a very tenuous detection, and only one line of the species was detected, and a lot of really complicated data analysis methods had to be applied to even make that weak detection.

Lex Fridman 48:27 Yeah.

Katherine de Kleer 48:28 Um...

Lex Fridman 48:29 So it could be... it could be noise, it could be polluted data, it could be all the- all those things. And so it doesn't have... it doesn't meet the- the level of, uh, rigor that you would hope, but of course, I mean, we're doing our best. And it's clear that, uh, the human species are hopeful to find life.

Katherine de Kleer 48:47 Clearly, yes.

Lex Fridman 48:48 (laughs)

Katherine de Kleer 48:48 Everyone is so excited about that possibility.

Lex Fridman 48:51 All right, let's, uh, let me ask you about Mars. So, um, there's a guy named Elon Musk.

Katherine de Kleer 49:02 (laughs)

Lex Fridman 49:02 And, uh, he seems to want to take something called Dogecoin there, first to the moon.

Katherine de Kleer 49:08 (laughs) Fuck. (laughs)

Lex Fridman 49:09 I'm just, I'm just kidding about the Dogecoin. I, I don't even know what the, what the heck is, uh, um, up with that whole, uh... I think, uh, I think humor has power in the 21st century, in a way to spread ideas in the most positive way.

Katherine de Kleer 49:28 Mm-hmm.

Lex Fridman 49:28 So, I love that kind of humor 'cause it makes people smile, but it also kind of sneak, it's like a Trojan horse for cool ideas. (laughs) You w- you open with humor and you, uh, like the humor is the appetizer, and then the main meal is the science and the engineering.

Katherine de Kleer 49:49 (laughs)

Lex Fridman 49:49 Anyway, uh, do you think it's possible to colonize Mars or other planets in the solar system? But we're especially, uh, looking to Mars. Is there something about planets that make them very harsh to humans? Is there something in particular you think about and maybe, you know, high, like big picture perspective, do you have a hope we, we do in fact become a multi-planetary species?

Katherine de Kleer 50:19 I do think that if our species survives long enough and we don't wipe ourselves out or get wiped out by some other means-

Lex Fridman 50:28 Yes.

Katherine de Kleer 50:28 ... that we will eventually be able to colonize other planets. I do not expect that to happen in my lifetime. I mean, tourists may go to Mars, tourists, people who commit years of their life to going to Mars as a tourist may go to Mars. Um, I don't think that we will colonize it. Um-

Lex Fridman 50:47 Is there a sense why? You think it's just too harsh of an environment to, uh, to, to... Like it's too costly to build something habitable there for a large population?

Katherine de Kleer 51:00 I think that we need to do a lot of work in learning how to use the resources that are on the planet already to do the things we need. So, if you're talking about someone going there for a few months, um, so back up a little bit. There are many things that make Mars not hospitable. Temperature, you can't breathe the air, you need a pressure suit. Even if you're on the surface, the radiation environment is, you know, even in all of those things, the radiation environment is too harsh for the human body. Um, all of those things seem like they could eventually have technological solutions. Um, the challenge, the, the real significant challenge to me seems to be the, the creation of a self-sustaining civilization there. You know, you can bring pressure suits, you can bring oxygen to breathe, but those are all in limited supply. And if we're gonna colonize it, we need to find ways to make use of the resources that are there to do things like produce food, produce the air the humans need to keep breathing. Just in order to make it self-sustaining, there's a tremendous amount of work that has to be done. And people are working on these problems, but I think-

Lex Fridman 52:13 It's difficult.

Katherine de Kleer 52:13 ... that's gonna be a major obstacle in going from visiting where we can bring everything we need to survive in the short term to actually colonizing.

Lex Fridman 52:22 Yeah. I find that whole project of the human species quite inspiring, these like huge moonshot projects. Somebody... I, I was reading s- something, um, in terms of the source of food that's th- that may be the most effective on Mars, is you could farm insects. That's the easiest thing to farm. So we'd be eating like cockroaches if we're living on Mars, 'cause that's the easiest thing to actually, um, as a source of protein. So growing a source of protein is the easiest thing is, uh, is insects. I just imagine this giant f- For people who are afraid of insects, this is not a pleasant... (laughs) Maybe you're not supposed to even think of it that way. It would be like a cockroach milkshake or something like that.

Katherine de Kleer 53:09 Right. I wonder if, have people been working on the genetic engineering of, of insects to make them...

Lex Fridman 53:17 More radiation friendly? Uh, resistant.

Katherine de Kleer 53:18 Right, or pressure resistant or whatever, make them more-

Lex Fridman 53:21 But this is not, this is... What could possibly go wrong with-

Katherine de Kleer 53:24 (laughs)

Lex Fridman 53:24 ... a cockroach to make him radiation resistant? They're already like survived all, ev- everything. Plus I, um, I took an allergy test, um, in Austin. So there's, e- everybody's aller- it was like the allergy levels are super high there.

Katherine de Kleer 53:37 (laughs)

Lex Fridman 53:37 Uh, and, uh, one of the things apparently, I'm not allergic to any insects except cockroaches, which is hilarious.

Katherine de Kleer 53:44 Hmm.

Lex Fridman 53:44 So maybe, uh, um, well, the, I'm gonna use that as a, you know how people use, uh, uh, an excuse that, "I'm allergic to cats," to not have cats. I'm gonna use that as an excuse to, uh, not go to Mars as one of the first batch of people. Other than what-

Katherine de Kleer 53:58 I was gonna ask, if you had the opportunity, would you go?

Lex Fridman 54:01 Yeah, I'm joking about the cockroach thing and-

Katherine de Kleer 54:03 (laughs)

Lex Fridman 54:03 ... I would definitely go. I love challenges. I love, I love things... I love doing things where the possibility of death is s- is, uh, not insignificant.

Katherine de Kleer 54:16 Hmm.

Lex Fridman 54:17 'Cause it makes me appreciate it more. D- Uh, meditating on death makes me appreciate life. And, uh, when the meditation on death is forced on you 'cause of how difficult the task is, I enjoy those kinds of things.

Katherine de Kleer 54:37 Hmm.

Lex Fridman 54:37 Most people don't, it seems like. (laughs) But I love the idea of difficult journeys, um, for no purpose whatsoever except exploration, going into the unknown, seeing what the limits of the human mind and the human body are.... is like, what the hell else is this whole journey that we're on for? I- I- I- uh, but it could be because I grew up in the Soviet Union. There's a kind of love for space, like, the- the space race, the Cold War created. I don't know if still it permeates American culture as much, but especially with a dad as a scientist, I think I've- I've loved the idea of humans striving out towards the stars, always. Like, from the engineering perspective.

Katherine de Kleer 55:23 Mm-hmm.

Lex Fridman 55:23 It's been really exciting. I don't know if people love that as much in America anymore. I think, uh, Elon is bringing that back a little bit, that excitement about rockets and, uh-

Katherine de Kleer 55:32 Yeah, I agree.

Lex Fridman 55:32 ... going out there. But, uh... So that- that's hopeful. But for me, I always loved

Lex Fridman 55:37 that idea. From a alien scientist perspective, if you were to look back on Earth, uh, is there something interesting you could say about Earth? Like how would you summarize Earth? Like in a rep- you know, like, uh, Hitchhiker's Guide to the Galaxy? Like, if you had to report, like write a paper on Earth, or- or like a letter, like a- like a one-pager, um, summarizing the contents of the surface and the atmosphere, is there- is there something interesting? Like, do you ever take that kind of perspective on it? I know you like volcanism, so volcanoes that will probably be in the report.

Katherine de Kleer 56:14 I- I was gonna say, that's where I was gonna go first. Uh, there are a few things to say about the atmosphere, but in terms of the volcanoes... So one of the really interesting puzzles to me in planetary science is, so we can- we can look out there and we've been talking about surfaces and volcanoes and atmospheres and things like that. But that is just, you know, this tiny little veneer on the outside of the planet, and most of the planet is completely sort of inaccessible to telescopes or to spacecraft missions. You can drill a meter into the surface but, you know, that's still really the veneer. Um, and one of the cool puzzles is looking at what's going on on the surface and trying to figure out what's happening underneath, or just any kind of indirect means that you have to study the interior because you can't dig into it directly. Even on Earth you can't dig in- deep into Earth. Uh, so from that perspective, looking at Earth, um, one thing that you would be able to tell from orbit, given enough time, is that Earth has tectonic plates. So you would see that volcanoes follow the edges, if you trace where all the volcanoes are on Earth-

Lex Fridman 57:24 Mm-hmm.

Katherine de Kleer 57:24 ... they follow these lines that trace the edges of the plates. And similarly you would see things like the, uh, Hawaiian string of volcanoes that you could infer just like, you know, we did as people actually living on Earth that the plates are moving over some plume that's coming up through the mantle. And so you could use that to say... if the aliens could look at where the volcanoes are- are happening on Earth and say something about the fact that Earth has plate tectonics, which makes it really unique in the solar system. Um-

Lex Fridman 57:55 Oh, really? So the other planets don't have plate tectonics?

Katherine de Kleer 57:56 It's the only one that has plate tectonics, yeah.

Lex Fridman 57:59 Well, what about Io and the fr- the friction and all that that's not plate tect... What's the difference between... So, oh, is plate tectonics like another layer of like solid rock that moves around-

Katherine de Kleer 58:11 Right.

Lex Fridman 58:11 ... and there's cracks?

Katherine de Kleer 58:12 Exactly. Yeah, so- so Earth has plates of solid rock sitting on top of a partially molten layer, and those plates are kind of shifting around. Um, on Io, it doesn't have that and the volcanism is what we call heat pipe volcanism. It's the magma just punches a hole through the crust and comes out on the surface. I mean, that's a simplification, but that's effectively what's happening.

Lex Fridman 58:36 Through the freezing cold crust?

Katherine de Kleer 58:37 Yes. Very cold, very rigid crust, yeah.

Lex Fridman 58:42 How do you- how does that look like by the way? Uh, I- I don't think we've mentioned, so the gas that's expelled, like if we were to look at it, does it look beautiful or does it look boring?

Katherine de Kleer 58:51 The gas?

Lex Fridman 58:52 Like, the whole thing, like the- the magma punching through the-

Katherine de Kleer 58:56 Oh my gosh.

Lex Fridman 58:56 ... the icy...

Katherine de Kleer 58:57 Yes, I'm sure it would be beautiful, and the pictures we've seen of it are beautiful. You have... So the- the magma will come out of, the lava will come out of these fissures and you have these curtains of lava that are maybe even a kilometer high. So if you looked at videos-

Lex Fridman 59:15 Wow.

Katherine de Kleer 59:15 ... I don't know how many volcano videos you've looked at on Earth, but you sometimes see a tiny, tiny version of this in Iceland. You see just these sheets of magma coming out of a fissure when you have this really low, um, viscosity magma sort of water-like coming out as sheets.

Lex Fridman 59:29 Yeah.

Katherine de Kleer 59:29 Um, and the plumes that come out, because there's no atmosphere, um, all the plume molecules are just, or plume particles, where they end up is- is just a function of the direction that they left the vent. So they're all following-

Lex Fridman 59:44 Oh.

Katherine de Kleer 59:44 ... ballistic trajectories. Um, and you end up with these umbrella plumes. You don't get these sort of complicated plumes that you have on Earth that are occurring because of how that material is interacting with the atmosphere that's there. You just have these huge umbrellas. And it's been hypothesized actually that... So the atmosphere is made of sulfur dioxide, and that you could have these kind of ash particles from the volcano and the sulfur dioxide would, um, condense onto these particles and you'd have sulfur dioxide snow coming out of these volcanic plumes.

Lex Fridman 1:00:18 And, uh, there's not much light though, right? So you wouldn't be able to s- like it would make a good- it would not make a good Instagram photo because you have to... Would you see the snow?

Katherine de Kleer 1:00:28 Sure. There's light. It depends.

Lex Fridman 1:00:31 Oh, okay. So you could s- you could still... okay.

Katherine de Kleer 1:00:32 Depends what angle you're looking at it-

Lex Fridman 1:00:34 Got you.

Katherine de Kleer 1:00:34 ... where the sun is, all the things like that.

Lex Fridman 1:00:36 All right.

Katherine de Kleer 1:00:36 You know, the sunlight is much weaker but it's still there.

Lex Fridman 1:00:38 It's still there. And, uh, how- how big is Io in terms of gravity? Is- is it smaller? Is it a pretty small moon?

Katherine de Kleer 1:00:47 It's quite a bit smaller than Earth anyway.

Lex Fridman 1:00:49 A lot smaller-

Katherine de Kleer 1:00:50 Yeah.

Lex Fridman 1:00:50 ... than Earth, okay. Okay cool. So they float- float out for a little bit.

Katherine de Kleer 1:00:54 Mm-hmm.

Lex Fridman 1:00:54 So it floats... Uh, they... Yeah, no, you're right, that would be- that would be- that would be gorgeous. Um, now what else about Earth?... is interesting besides volcan- So, plate tectonics, I d- I didn't realize that that was a unique element of a planet in the solar system, um, 'cause that, I wonder what... I mean, we experience it as human beings as quite painful because of the earthquakes and all those kinds of things. But I wonder if there's nice features to it?

Katherine de Kleer 1:01:22 Yeah. So, coming back to habitability again, um, things like tectonics and plate tectonics are, are thought to play an important role in the surface being habitable and that's because you have a way of recycling material. So, if you have a stagnant surface, everything, you know, you use up all the free oxygen, everything reacts until you no longer have reactants that life can extract energy from. And so, if nothing's changing on your surface, you kind of reach this stagnation point. Um, but something like plate tectonics recycles material. You bring up new, fresh material from the interior, you bring down material that's up on the surface and, and that can kind of refresh your, your nutrient supply in a sense, or the, the sort of raw-

Lex Fridman 1:02:08 Mm-hmm.

Katherine de Kleer 1:02:08 ... materials that, that the surface has to work with. So, um, from a kind of astrobiologist perspective looking at Earth, you would see that recycling of material because of the plate tectonics. You would also see how much oxygen is in Earth's atmosphere and between those two things, you would identify Earth as a reasonable candidate for a habitable environment. Um, in addition to, of course, the, you know, pleasant temperature and liquid water. Um, but the abundance of oxygen and the, the plate tectonics both play a role as well.

Lex Fridman 1:02:42 And also see, like, tiny dot satellites flying around and-

Katherine de Kleer 1:02:45 Well, sure. Yes.

Lex Fridman 1:02:46 ... shooting rockets. I wonder if they would be able to... I really think about that, like, if they, if aliens were to visit, I mean, would they really see humans as the thing they should be focusing on? I think it would take a while, right? Because it's so obvious that that should... 'Cause there's, like, so much incredible li- uh, in terms of biomass, humans are a tiny, tiny, tiny fraction. There's, like, ants. W- they would probably detect ants, right?

Katherine de Kleer 1:03:15 (sighs)

Lex Fridman 1:03:15 Or they probably would focus on the water and the fish 'cause there's, like, a lot of wa-... I don't, I was surprised to learn that there's more species on land than there is in the sea. Like, there's 90, I think 90 to 95% of the species are on land than is-

Katherine de Kleer 1:03:29 Are on land?

Lex Fridman 1:03:30 On land.

Katherine de Kleer 1:03:30 Not in the sea? Oh.

Lex Fridman 1:03:31 Not in the sea. Oh, I thought, like, there's so much going on in the sea. But no-

Katherine de Kleer 1:03:35 Right.

Lex Fridman 1:03:35 ... the, the variety that, like, the branches created by evolution apparently... It's probably a good answer from an evolutionary biology perspective why land created so much diversity, but it did. So, like, the sea, there's so much not known about the sea, about the oceans, but it's not, um, it's not diversity friendly. What, what can I say?

Katherine de Kleer 1:03:58 Mm-hmm.

Lex Fridman 1:03:58 It needs, uh, it needs to, it needs to improve its diversity. What can you do to see?

Katherine de Kleer 1:04:01 So do you think the aliens would come? I mean, the first thing they would see is, I suppose, our, our cities. Assuming that they had some idea of what a natural world looked like, they would see cities and say, "These don't belong. Which of these many species created these?"

Lex Fridman 1:04:16 Yeah. I mean, there's, I, if I were to guess, it would... It's a good question. I don't know if you do this when you look at the telescope, whether you look at, uh, geometric shapes. Like, if it's, uh, g- g- 'cause to me, like, hard corners, like, what do we think is engineered? Things that are, like, have kinda straight lines and corners and so on. They will probably detect those and in terms of buildings would stand out to them because that's, that goes against the basic natural ph- physics of the world. Um, but I don't know if the, uh, electricity and lights and so on. It could be, I, honestly, it could be the pl- plate tectonics (laughs) .

Katherine de Kleer 1:05:01 (laughs)

Lex Fridman 1:05:01 It could be like, hmm, that, uh, the, like, the volcanoes. That'd be, okay, that's a source of heat and then they would focus. They might literally, I mean, depending on how alien life forms are, they might notice the microorganisms before they notice the big, like, notice the ant before the elephant. 'Cause, like, there's a lot more of them depending what they're measuring devi-... We think like size matters, but maybe with their tools of measurement, they would look for quantity versus size. Like, why focus on the big thing? Focus on the thing that there's a lot of. And when they see humans, depending on their measurement devices, they might see we're made up of billions of organisms. Like, the fact that we have, w- we're very human-centered. We think that we're one organism, but that, that may not be the case. They might see, in fact, they might also see, like, a human city as one organism. Like, what is this thing that, like... Clearly, this organism gets, um, aroused at night 'cause the lights go on and then, uh, and then it, it, like, it sleeps during the day (laughs) . I don't know i-... How, like, the, what perspective you take on the city.

Lex Fridman 1:06:16 Is there something interesting about Earth or other planets in terms of weather patterns? So, we talked ab- a lot about, uh, volcanic patterns. Is there something else about weather that's interesting, like storms or variations in temperature, all those kinds of things?

Katherine de Kleer 1:06:38 Yeah. So, there's sort of... Every planet and moon has a kind of interesting and, and unique weather pattern and those weather patterns are really, we don't have a good understanding of them. We don't even have a good understanding of the, the global circulation patterns, um, of, of many of these atmospheres. Why the storm systems occur? So, the, the-... composition and occurrence of storms and clouds in these objects is, is another one of these kind of windows into the interior that I was talking about with surfaces. One of these, um, ways that we can get perspective and what the composition is of the interior and how the circulation is working. So circulation will bring some species up from deeper in the atmosphere of the planet to some altitude that's a little bit colder and that species will condense out and form a cloud at that altitude. And we can detect, in some cases, what those clouds are composed of. Um, and looking at where those occur, um, can tell you how the circulation cells are. Whether the atmospheric circulation is say coming up at the equator and going down at the poles, or whether you have multiple cells in the atmosphere. And I mean Jupiter's atmosphere is, is just insane. There's so much going on. You look at these pictures, and there's all these vortices and anti-vortices, and you have these different bands that are moving in, in opposite directions that may be giving you information about the, the deep prop- like deep in the atmosphere-

Lex Fridman 1:08:14 Mm-hmm.

Katherine de Kleer 1:08:14 ... um, physically deep properties of, um, Jupiter's interior and, and circulation. Um...

Lex Fridman 1:08:22 What are the, these vortices? What, what's the basic material of the storms?

Katherine de Kleer 1:08:27 It's condensed molecules from the atmosphere, so ammonia ice particles, um, in the case of Jupiter. It's methane ice in the case of let's say Uranus and Neptune, and other species. You can kind of construct a chemical model for which species can condense where. And so you see a cloud at a certain altitude within the atmosphere, and you can make a guess at what that cloud is made of.

Lex Fridman 1:08:48 Oh.

Katherine de Kleer 1:08:49 And sometimes measure it directly and, you know, different species make different colors as well.

Lex Fridman 1:08:54 Oh, cool.

Katherine de Kleer 1:08:55 Um...

Lex Fridman 1:08:55 Ice storms, okay.

Katherine de Kleer 1:08:57 I mean the climate of Uranus has always been fascinating to me because it orbits on its side, and it has a 42-year orbital period. And so, you know, with Earth, our seasons are because our equator is tipped just a little bit to the plane that we orbit in.

Lex Fridman 1:09:13 Yeah.

Katherine de Kleer 1:09:13 So sometimes the sun lights a little bit above the equator and sometimes it's a little bit below the equator. But on Uranus, it's like for, for 10 years, the sunlight is directly on the North Pole, and then it's directly on the equator, and then it's directly on the South Pole. And it, it's actually kind of amazing that the atmosphere doesn't look crazier than it does. Uh, but understanding how the... Taking again like one of these extreme examples, if we can understand why that atmosphere behaves in the way it does, it's kind of a test of our, our understanding of how, how atmospheres work.

Lex Fridman 1:09:45 So it like heats up one side of the planet for 10 years, and then freezes it the next like... And that you're saying w- should probably lead to some chaos, a- and it, it doesn't.

Katherine de Kleer 1:10:01 The fact that it doesn't tells you something about the atmosphere. So atmospheres have a property that surfaces don't have, which is that they can redistribute heat a lot more-

Lex Fridman 1:10:09 Re-distribute, right.

Katherine de Kleer 1:10:09 ... effectively. Uh...

Lex Fridman 1:10:10 So they have a stabilizing, like self-regulating aspect to them, that they're able to deal with extreme conditions. (sighs) But predicting how that complex system unrolls is, is, is very difficult, as we know about predicting the weather on Earth even.

Katherine de Kleer 1:10:28 Oh my goodness, yeah, so...

Lex Fridman 1:10:29 Even with the little variation we have on Earth.

Katherine de Kleer 1:10:31 You know, people have tried to put together global circulation models. So you know we've done this for Earth. People have tried to do these for other planets as well, and it is a really hard problem. Um, so Titan, for example, like I said, it's, it's one of the best studied atmospheres in the solar system, and people have tried to make these global circulation models and actually predict what's going to, to happen moving into sort of the next season of Titan.

Lex Fridman 1:10:55 Re-distribute.

Katherine de Kleer 1:10:55 And those predictions have ended up being wrong. And so then, you know, it's, I, I don't know. It's always exciting when a prediction is wrong because it means that there's something more to learn, like your theory wasn't sufficient.

Lex Fridman 1:11:05 Mm-hmm.

Katherine de Kleer 1:11:05 And then you get to go back and learn something by how you have to modify the theory to make it fit.

Lex Fridman 1:11:11 I'm excited by the possibility one day there'll be for various moons and planets, there'll be, uh, like news programs reporting the weather, uh, with a fake confidence of, like as if you can predict the weather.

Katherine de Kleer 1:11:24 (laughs)

Katherine de Kleer 1:11:25 .

Lex Fridman 1:11:25 Uh, we talked quite a bit about planets and moons. Can we talk a little bit about asteroids?

Katherine de Kleer 1:11:31 For sure.

Lex Fridman 1:11:32 What is, uh, what's an asteroid? And what kind of asteroids are there?

Katherine de Kleer 1:11:36 So the asteroids, l- let's talk about just the r- restricted to the main asteroid belt, which is the region, it's a region of debris basically-

Lex Fridman 1:11:46 Mm-hmm.

Katherine de Kleer 1:11:46 ... between Mars and Jupiter. Um, and the, these sort of belts of debris throughout the solar system, the outer solar system, you know, the Kuiper Belt that we talked about, the asteroid belt, as well as certain other populations where they accumulate because they're gravitationally more favored, um, are, are remnant objects from the origin of the solar system. And so one of the reasons that we are so interested in them, um, aside from potentially the fact that they could come hit Earth, but, uh, scientifically, it's, um, it gives us a, a window into understanding the composition, uh, of the material from which Earth and the other planets formed and how that material was kind of redistributed over the, the history of the solar system. So the asteroids, one could classify them in two different ways. Some of them are ancient objects, so they accreted out of the, the sort of disc of material that the whole solar system formed out of, um, and have kind of remained ever since more or less the same. Um, they've probably collided with each other and we see the, all these collisional fragments. And you can actually look and...... um, based on their orbits, say, you know, like, "These 50 objects originated as the same object." Uh, you can see them kind of dynamically moving apart after some big collision. Um, and so some of them are these ancient objects, maybe, that have undergone collisions, and then there's this other category of object that is the one that I personally find really interesting, which is, um, remnants of objects that could have been planets. So early on, a bunch of potential planets accreted that we call planetesimals, and they formed, and they formed with a lot of energy, and they had enough time to actually differentiate. So some of these objects differentiated into cores and mantles and crusts. Uh, and then they were subsequently disrupted in these massive collisions, and they... Now we have these fragments, we think, fragments floating around the asteroid belt that are, like, bits of mantle, bits of core, bits of crest-

Lex Fridman 1:14:08 Oh wow, cool.

Katherine de Kleer 1:14:08 ... basically. Um...

Lex Fridman 1:14:10 So it's like puzzle pieces that you might be able to stitch together, or I guess it's, it's all, uh, it's all mixed up so you can't stitch together the original planet candidates, or is that possible to try to see if they kind of s- I mean there's too many o- uh, there's too many objects in there to-

Katherine de Kleer 1:14:29 I think that there are cases where people have, have kind of looked at objects and, by looking at their orbits, they say, "These objects should have originated together," but they have very different compositions.

Lex Fridman 1:14:39 Mm-hmm.

Katherine de Kleer 1:14:39 And so then you can hypothesize maybe they were different fragments of a differentiated object. But one of the really cool things about this is, you know, we've been talking about getting clues into the interiors of planets. We've never seen a planetary core or deep mantle directly. Some mantle material comes up on Earth's surface and then we can see it, but, you know, in, in sort of in bulk. Um, we haven't seen these things directly and these asteroids potentially give us a chance to, like, look at what our own core and mantle is like, or at least would be like if it had been also floating through space for a few billion years and, and getting irradiated and all that. Uh, but it's, it's a cool potential window or, like, analogy into the interior of our own planet.

Lex Fridman 1:15:26 Well, how do you begin studying some of these asteroids? What, uh, if you were to put together a study, like, what are the interesting questions to ask that are a little bit more specific? Like, do you find a favorite asteroid that could be tracked and try to, try to track it through telescopes, or do you, um, is th- is it has to be you have to land on those things to study it?

Katherine de Kleer 1:15:51 So wh- when it comes to the asteroids, there's so many of them in the big pictures, or the, the big questions are answered, um... So some questions can be answered by f- zooming in in detail on individual object, but mostly you're trying to do a statistical study.

Lex Fridman 1:16:11 Yeah.

Katherine de Kleer 1:16:11 So you want to look at thousands of objects, even hundreds of thousands of objects, uh, and figure out what their composition is and look at, you know, how many big asteroids there are of this composition versus how many small asteroids of this other composition and put together these kind of statistical properties of the asteroid belt. And those properties can be directly compared with the results of simulations for the, the formation of the solar system.

Lex Fridman 1:16:41 Mm-hmm. What do we know about the surfaces of asteroids, or the con- the, the contents of the insides of asteroids, and what are still open questions?

Katherine de Kleer 1:16:52 So I would say that we don't know a whole lot about their compositions. Um, most of them are small, and so you can't study them in such detail with telescopes as, as you could, you know, a planet or moon. And at the same time, because there are so many of them, you could send a spacecraft to a few, uh, but you can't really, like, get a statistical survey-

Lex Fridman 1:17:17 Yeah.

Katherine de Kleer 1:17:17 ... with spacecraft. And so a lot of what we, a lot of what has been done comes down to sort of classification. You look at-

Lex Fridman 1:17:25 Mm-hmm.

Katherine de Kleer 1:17:25 ... how bright they are, you look at, uh, whether they're red or blue, um, simply, you know, whether their spectrum is sloped towards long wavelengths or short wavelengths. There are certain, uh, if you, if you, uh, point a, a spectrograph at their surfaces, there are certain features you can see. So you can tell that some of them have silicates on them.

Lex Fridman 1:17:44 Mm-hmm.

Katherine de Kleer 1:17:45 Um, and, uh, but these are the sort of... They're pretty basic questions. We're still trying to classify them based on fairly basic information in kind of combination with our general understanding of the material the solar system formed from, and so you're sort of, you com- you're coming in with prior knowledge, which is that you more or less know what the materials are the solar system formed from, and then you're trying to cl- classify them into these categories. There's still a huge amount of room for, for understanding them better, um, and for understanding how their surfaces are changing in the space environment.

Lex Fridman 1:18:20 Is it hard to land on an asteroid? Is this, uh, is this- is this- is this a dumb question?

Katherine de Kleer 1:18:26 (laughs) .

Lex Fridman 1:18:26 It feels like, uh, it would be quite difficult to actually operate a spacecraft in such a, uh, dense field of debris.

Katherine de Kleer 1:18:39 Oh, the asteroid belt. Um, there's a ton of material there, but it's actually not that dense. It is mostly open space.

Lex Fridman 1:18:45 Okay.

Katherine de Kleer 1:18:46 Uh, so, so mentally do picture, like, mostly open space with, with some rocks. Uh, the problem is some of them are not thought to be solid. So some of these asteroids, especially these, these core mantle fragments you can think of as sort of solid like a planet, but some of them are just kind of aggregates of material. We call them rubble piles.

Lex Fridman 1:19:06 Mm-hmm.

Katherine de Kleer 1:19:06 And so there's not necessarily-

Lex Fridman 1:19:09 Might look like a rock.

Katherine de Kleer 1:19:10 (laughs) .

Lex Fridman 1:19:10 But do, do a lot of them have kind of-... clouds around them, like a dust cloud thing? Or, like, do you know what you're stepping on when you try to land on it? (laughs) Like, what, what-

Katherine de Kleer 1:19:23 (laughs)

Lex Fridman 1:19:24 ... what are we supposed to be visualizing here? There's, like, very few have water, right?

Katherine de Kleer 1:19:29 There's some water in the outer part of the asteroid belt, but they're not-

Lex Fridman 1:19:32 Okay.

Katherine de Kleer 1:19:32 ... quite like comets-

Lex Fridman 1:19:33 Okay.

Katherine de Kleer 1:19:34 ... um, in the, in the sense of having clouds around them. There are some crazy asteroids that do become active like comets. That's li- a whole other category of thing that we don't-

Lex Fridman 1:19:43 Yeah.

Katherine de Kleer 1:19:43 ... understand. Um, but their surfaces, I mean, we have visited some, you can, you know, find pictures that spacecraft have taken of them and we've actually scooped up material off of the surface of some of these objects. We're bringing it back-

Lex Fridman 1:19:56 Hmm.

Katherine de Kleer 1:19:56 ... to, to analyze it in the lab um, and there's a mission that's launching next year to land on one of these supposedly core fragment objects to try to figure out what the heck it is and what's going on with it. Uh, but the surfaces, you know, they're, they're... You can picture a solid surface with some little grains of sand or pebbles on it and occasional boulders. Maybe some fine dusty regions, dust kind of collecting in certain places, but...

Lex Fridman 1:20:27 Is, is there, does... Do you worry about this? Is there any chance that one of these fellas destroys all of human civilization by, um, an asteroid kind of colliding with something, changing its trajectory, and then heading on its way towards Earth?

Katherine de Kleer 1:20:47 That is definitely possible, and it doesn't even have to necessarily collide with something and change its trajectory. We're not tracking all of them. We can't track all of them yet. You know, there's still-

Lex Fridman 1:21:00 A lot of them.

Katherine de Kleer 1:21:01 People are, people are tracking a lot of them and we are doing our best to track more of them, but there are a lot of them out there and it would be potentially catastrophic if one of them impacted Earth. Um, have you... Are, are you aware of this, um, Apophis object? So, there's an asteroid, a near-Earth object, called Apophis, that people thought had a, a decent probability of hitting Earth in 2029 and then potentially again in 2036, so they did a lot of studies. It's not actually going to hit Earth, but it is going to come very close. It's gonna be visible in the sky in a relatively dark... I mean, not even that dark. Um, probably not visible from Los Angeles, but, um... And it's gonna come, uh, a tenth of the way between the Earth and the, the moon. It's gonna come closer, apparently, than some geosynchronous communication satellites.

Lex Fridman 1:21:56 Oh, wow.

Katherine de Kleer 1:21:56 So, that is a close call, but people have studied it and, and apparently-

Lex Fridman 1:22:01 Yeah.

Katherine de Kleer 1:22:02 ... are very confident it's not actually going to hit us, but it was-

Lex Fridman 1:22:04 We're gonna have to look into this-

Katherine de Kleer 1:22:05 Yeah. (laughs)

Lex Fridman 1:22:06 ... 'cause I, I'm very sure, I'm very sure what's gonna happen if an asteroid actually hits Earth, that the scientific community and government will confidently say that, uh, "We have nothing to worry about. It's going to be a close call."

Katherine de Kleer 1:22:26 (laughs)

Lex Fridman 1:22:26 And then last minute they'll be like, "There was a miscalculation." (laughs) They're not lying, it's just like the space of possibilities, 'cause it's very difficult to track these kinds of things, and there's a lot of kind of... there's complexities involved, so there's a lot of uncertainties.

Katherine de Kleer 1:22:42 Mm-hmm.

Lex Fridman 1:22:42 But I just... There's something tells me that human civilization will end with, we'll see it coming, and then last minute there'll be a, "Oops." Well, like, we'll see it coming and we'll, we'll be like, "No, it's, this is, this is threatening, but no problem. No problem." And last minute it'll be like, "Oops, that was a miscalculation." And then it's all over in a matter of like a week. (laughs) But, uh, is there... (laughs) We're just very positive and optimistic today.

Katherine de Kleer 1:23:10 (laughs)

Lex Fridman 1:23:10 Is there, uh, any chance that Bruce Willis can save us-

Katherine de Kleer 1:23:13 (laughs)

Lex Fridman 1:23:13 ... uh, in the sense that from what you know about asteroids, is there something that, um, it can catch them early enough to, uh, change volcanic, uh, eruptions, right? Um, so they drill, put a nuclear weapon inside, and, uh, break up the asteroid or change its trajectory.

Katherine de Kleer 1:23:37 There is potential for that if you catch it early enough in advance. Um, I think in theory if you knew five years in advance?

Lex Fridman 1:23:49 5:00 PM.

Katherine de Kleer 1:23:50 Um... Depending on the object and how close or how, how much you would need to deflect it, um, you could deflect it a little bit. I don't know that it would be sufficient in all cases, um, and this is definitely not my specific area of expertise, but my understanding is that there is something you could do. Um, but it also... How you would carry that out depends a lot on the properties of the asteroid. If it's a solid object versus a rubble pile, so let's say you planted some bomb in the middle of it and it blew up, but it was just kind of a pile of material anyway, and then that material comes back together and then you kind of just have the same thing. Presumably its trajectory would be altered, but-

Lex Fridman 1:24:36 Right.

Katherine de Kleer 1:24:36 ... it's, it, it n-

Lex Fridman 1:24:37 It's like Terminator 2 when it's like the th- the thing that just like, you shoot it and it splashes and then it comes back together. It would be very useless.

Katherine de Kleer 1:24:44 (laughs)

Lex Fridman 1:24:44 That's fascinating, and, but what's fascinating... I've gotten a lot of hope from watching, uh, uh, SpaceX rockets that land. There's so much, it's like, oh wow, from an AI perspective, from a robotics perspective, wow, we can do a hell of an amazing job with control.

Katherine de Kleer 1:25:08 Hmm.

Lex Fridman 1:25:09 And, but then we have an understanding about surfaces here on Earth, we can tr- map out a lot of things. I wonder if we can do that some kind of detail...... of being able to do, have that same level of precision in landing on surfaces with as wide of a, of a variety as asteroids have. So to be able to understand the exact properties of the surface and be able to