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

1. 0:00 – 1:27

   Introduction

   1. LFLex Fridman0:00

      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.

2. 1:27 – 6:35

   Pluto

   1. LFLex Fridman1:27

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

   2. KKKatherine de Kleer1:35

      (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...

   3. LFLex Fridman3:05

      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?

   4. KKKatherine de Kleer3:21

      (laughs)

   5. LFLex Fridman3:21

      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...

   6. KKKatherine de Kleer3:32

      So there are technically clear definitions that were set down by the IAU, the International Astronomy Union. Um...

   7. LFLex Fridman3:41

      Is it size related? Like what are the parameters based on what?

   8. KKKatherine de Kleer3:44

      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.

   9. LFLex Fridman4:14

      Mm-hmm.

   10. KKKatherine de Kleer4:15

       Um, and because Pluto orbits in a belt of material, it doesn't satisfy that stipulation. Uh...

   11. LFLex Fridman4:21

       Why didn't it clear out the path? It's not big enough-

   12. KKKatherine de Kleer4:23

       Right.

   13. LFLex Fridman4:23

       ...to knock everybody out of the way?

   14. KKKatherine de Kleer4:26

       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.

   15. LFLex Fridman5:28

       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?

   16. KKKatherine de Kleer6:06

       No, I actually do. I really, satellites or the moons are my favorite things-

   17. LFLex Fridman6:10

       Yeah.

   18. KKKatherine de Kleer6:10

       ... 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.

   19. LFLex Fridman6:19

       Right.

   20. KKKatherine de Kleer6:19

       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.

3. 6:35 – 10:32

   Kuiper belt

   1. KKKatherine de Kleer6:35

   2. LFLex Fridman6:35

      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?

   3. KKKatherine de Kleer7:26

      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.

   4. LFLex Fridman7:48

      Right.

   5. KKKatherine de Kleer7:48

      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.

   6. LFLex Fridman8:24

      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?

   7. KKKatherine de Kleer8:52

      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.

   8. LFLex Fridman9:35

      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

4. 10:32 – 14:15

   How to study planets and moons

   1. LFLex Fridman10:32

      pause. Okay. What are the tools available to us to study planets and their moons?

   2. KKKatherine de Kleer10:37

      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.

   3. LFLex Fridman12:03

      All right. So you like telescopes-

   4. KKKatherine de Kleer12:04

      Um-

   5. LFLex Fridman12:04

      ... not rockets? Or at least you were-

   6. KKKatherine de Kleer12:06

      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.

   7. LFLex Fridman12:59

      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.

   8. KKKatherine de Kleer13:15

      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.

5. 14:15 – 26:46

   Volcanoes on Io - moon of Jupiter

   1. KKKatherine de Kleer14:15

   2. LFLex Fridman14:15

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

   3. KKKatherine de Kleer14:21

      Right.

   4. LFLex Fridman14:22

      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?

   5. KKKatherine de Kleer14:42

      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-

   6. LFLex Fridman16:06

      Okay.

   7. KKKatherine de Kleer16:06

      ... the moons as planets.

   8. LFLex Fridman16:08

      As, as planets?

   9. KKKatherine de Kleer16:09

      Um...

   10. LFLex Fridman16:09

       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)

   11. KKKatherine de Kleer16:19

       (laughs) .

   12. LFLex Fridman16:19

       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?

   13. KKKatherine de Kleer16:33

       It's, exactly. Yeah.

   14. LFLex Fridman16:34

       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-

   15. KKKatherine de Kleer16:45

       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.

   16. LFLex Fridman16:58

       Well yeah, please. What's tidal? (laughs) Yes. Yes, please.

   17. KKKatherine de Kleer17:01

       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.

   18. LFLex Fridman17:54

       Mm-hmm.

   19. KKKatherine de Kleer17:54

       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-

   20. LFLex Fridman18:06

       What's an eccentric orbit?

   21. KKKatherine de Kleer18:08

       So eccentric orbit or elliptical orbit, it just means non-circular.

   22. LFLex Fridman18:12

       Right.

   23. KKKatherine de Kleer18:12

       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-

   24. LFLex Fridman18:35

       Mm-hmm.

   25. KKKatherine de Kleer18:35

       ... and so you actually have the shape of the object deforming over the course of the orbit and these-

   26. LFLex Fridman18:40

       Wow.

   27. KKKatherine de Kleer18:40

       ... 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.

   28. LFLex Fridman18:52

       That's, that's the source of the-

   29. KKKatherine de Kleer18:54

       Yeah.

   30. LFLex Fridman18:55

       ... 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?
6. 26:46 – 36:07

   Is there life in the oceans of Europa?

   1. LFLex Fridman26:46

      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?

   2. KKKatherine de Kleer27:08

      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-

   3. LFLex Fridman28:54

      It's so cool.

   4. KKKatherine de Kleer28:54

      ... water interface is, is considered really important for the potential habitability.

   5. LFLex Fridman29:02

      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?

   6. KKKatherine de Kleer29:34

      I think anything's possible (laughs) .

   7. LFLex Fridman29:37

      (laughs) Okay. It's one of those things.

   8. KKKatherine de Kleer29:38

      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-"

   9. LFLex Fridman29:47

      Yeah.

   10. KKKatherine de Kleer29:47

       "... 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)

   11. LFLex Fridman30:28

       (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?

   12. KKKatherine de Kleer30:51

       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-

   13. LFLex Fridman31:18

       Mm-hmm.

   14. KKKatherine de Kleer31:19

       ... but your instrument could detect some spectroscopic signature of that dead bacterium. But that's-

   15. LFLex Fridman31:24

       Hm.

   16. KKKatherine de Kleer31:24

       ... you know, that's many ifs and assumptions that I-

   17. LFLex Fridman31:26

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

   18. KKKatherine de Kleer31:31

       Right, or even-

   19. LFLex Fridman31:32

       Skeletons of bacteria.

   20. KKKatherine de Kleer31:32

       ... I'm thinking even remotely, um, you know.

   21. LFLex Fridman31:34

       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.

   22. KKKatherine de Kleer31:47

       So Enceladus gives you a slightly better chance of that because Enceladus is a, is a moon of Saturn.

   23. LFLex Fridman31:55

       Mm-hmm.

   24. KKKatherine de Kleer31:55

       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-

   25. LFLex Fridman32:09

       Nice.

   26. KKKatherine de Kleer32:09

       ... 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.

   27. LFLex Fridman32:39

       Uh, can, can you tell me a little more, uh, on, uh, how do you pronounce it? Uh, Celad-

   28. KKKatherine de Kleer32:45

       Enceladus.

   29. LFLex Fridman32:45

       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.

   30. KKKatherine de Kleer32:55

       Not enough really.
7. 36:07 – 46:36

   How unlikely is life on Earth?

   1. LFLex Fridman36:07

      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?

   2. KKKatherine de Kleer36:40

      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.

   3. LFLex Fridman37:16

      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?

   4. KKKatherine de Kleer38:23

      (laughs) So-

   5. LFLex Fridman38:24

      Zero or one plus?

   6. KKKatherine de Kleer38:25

      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-

   7. LFLex Fridman38:45

      Right.

   8. KKKatherine de Kleer38:45

      ... 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-"

   9. LFLex Fridman39:02

      (laughs)

   10. KKKatherine de Kleer39:02

       "... A, common sense that didn't need to give a b- give a name."

   11. LFLex Fridman39:05

       Yeah.

   12. KKKatherine de Kleer39:05

       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.

   13. LFLex Fridman39:23

       Mm-hmm.

   14. KKKatherine de Kleer39:23

       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.

   15. LFLex Fridman39:50

       Well, definitive is a funny, is a funny word.

   16. KKKatherine de Kleer39:53

       (laughs)

   17. LFLex Fridman39:53

       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.

   18. KKKatherine de Kleer41:49

       Hmm.

   19. LFLex Fridman41:49

       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.

   20. KKKatherine de Kleer42:15

       I hope that's true.

   21. LFLex Fridman42:16

       You hope that-

   22. KKKatherine de Kleer42:16

       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.

   23. LFLex Fridman42:29

       (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.

   24. KKKatherine de Kleer43:28

       Right. Or what happened-

   25. LFLex Fridman43:29

       What the hell is-

   26. KKKatherine de Kleer43:29

       ... before the big bang.

   27. LFLex Fridman43:30

       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.

   28. KKKatherine de Kleer43:51

       (laughs)

   29. LFLex Fridman43:51

       (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?

   30. KKKatherine de Kleer44:06

       Oh, gosh, I have to come up with another favorite that's not Io?
8. 46:36 – 48:50

   Life on Venus

   1. LFLex Fridman46:36

      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?

   2. KKKatherine de Kleer46:56

      So, the detection that was reported-

   3. LFLex Fridman46:58

      Yeah.

   4. KKKatherine de Kleer46:58

      ... was the detection of the molecule phosphine.

   5. LFLex Fridman47:00

      Mm-hmm.

   6. KKKatherine de Kleer47:01

      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-

   7. LFLex Fridman47:18

      Gotcha.

   8. KKKatherine de Kleer47:18

      ... the train of logic, and, um, I don't personally believe that phosphine was detected in the first place.

   9. LFLex Fridman47:26

      Okay, so then, I mean, this is just one study, but I, as a layman-

   10. KKKatherine de Kleer47:31

       Mm-hmm.

   11. LFLex Fridman47:31

       ... 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.

   12. KKKatherine de Kleer47:47

       Oh, yeah. Well, that connection that you just made, the contents of the atmosphere to the life-

   13. LFLex Fridman47:51

       Yeah.

   14. KKKatherine de Kleer47:52

       ... 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-

   15. LFLex Fridman48:12

       Got it.

   16. KKKatherine de Kleer48:12

       ... 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.

   17. LFLex Fridman48:27

       Yeah.

   18. KKKatherine de Kleer48:28

       Um...

   19. LFLex Fridman48:29

       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.

   20. KKKatherine de Kleer48:47

       Clearly, yes.

   21. LFLex Fridman48:48

       (laughs)

   22. KKKatherine de Kleer48:48

       Everyone is so excited about that possibility.

9. 48:50 – 55:37

   Mars

   1. KKKatherine de Kleer48:51

   2. LFLex Fridman48:51

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

   3. KKKatherine de Kleer49:02

      (laughs)

   4. LFLex Fridman49:02

      And, uh, he seems to want to take something called Dogecoin there, first to the moon.

   5. KKKatherine de Kleer49:08

      (laughs) Fuck. (laughs)

   6. LFLex Fridman49:09

      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.

   7. KKKatherine de Kleer49:28

      Mm-hmm.

   8. LFLex Fridman49:28

      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.

   9. KKKatherine de Kleer49:49

      (laughs)

   10. LFLex Fridman49:49

       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?

   11. KKKatherine de Kleer50:19

       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-

   12. LFLex Fridman50:28

       Yes.

   13. KKKatherine de Kleer50:28

       ... 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-

   14. LFLex Fridman50:47

       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?

   15. KKKatherine de Kleer51:00

       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-

   16. LFLex Fridman52:13

       It's difficult.

   17. KKKatherine de Kleer52:13

       ... 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.

   18. LFLex Fridman52:22

       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.

   19. KKKatherine de Kleer53:09

       Right. I wonder if, have people been working on the genetic engineering of, of insects to make them...

   20. LFLex Fridman53:17

       More radiation friendly? Uh, resistant.

   21. KKKatherine de Kleer53:18

       Right, or pressure resistant or whatever, make them more-

   22. LFLex Fridman53:21

       But this is not, this is... What could possibly go wrong with-

   23. KKKatherine de Kleer53:24

       (laughs)

   24. LFLex Fridman53:24

       ... 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.

   25. KKKatherine de Kleer53:37

       (laughs)

   26. LFLex Fridman53:37

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

   27. KKKatherine de Kleer53:44

       Hmm.

   28. LFLex Fridman53:44

       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-

   29. KKKatherine de Kleer53:58

       I was gonna ask, if you had the opportunity, would you go?

   30. LFLex Fridman54:01

       Yeah, I'm joking about the cockroach thing and-
10. 55:37 – 1:06:15

    What is interesting about Earth as a planet?

    1. LFLex Fridman55:37

       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.

    2. KKKatherine de Kleer56:14

       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-

    3. LFLex Fridman57:24

       Mm-hmm.

    4. KKKatherine de Kleer57:24

       ... 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-

    5. LFLex Fridman57:55

       Oh, really? So the other planets don't have plate tectonics?

    6. KKKatherine de Kleer57:56

       It's the only one that has plate tectonics, yeah.

    7. LFLex Fridman57:59

       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-

    8. KKKatherine de Kleer58:11

       Right.

    9. LFLex Fridman58:11

       ... and there's cracks?

    10. KKKatherine de Kleer58:12

        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.

    11. LFLex Fridman58:36

        Through the freezing cold crust?

    12. KKKatherine de Kleer58:37

        Yes. Very cold, very rigid crust, yeah.

    13. LFLex Fridman58:42

        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?

    14. KKKatherine de Kleer58:51

        The gas?

    15. LFLex Fridman58:52

        Like, the whole thing, like the- the magma punching through the-

    16. KKKatherine de Kleer58:56

        Oh my gosh.

    17. LFLex Fridman58:56

        ... the icy...

    18. KKKatherine de Kleer58:57

        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-

    19. LFLex Fridman59:15

        Wow.

    20. KKKatherine de Kleer59:15

        ... 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.

    21. LFLex Fridman59:29

        Yeah.

    22. KKKatherine de Kleer59:29

        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-

    23. LFLex Fridman59:44

        Oh.

    24. KKKatherine de Kleer59:44

        ... 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.

    25. LFLex Fridman1:00:18

        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?

    26. KKKatherine de Kleer1:00:28

        Sure. There's light. It depends.

    27. LFLex Fridman1:00:31

        Oh, okay. So you could s- you could still... okay.

    28. KKKatherine de Kleer1:00:32

        Depends what angle you're looking at it-

    29. LFLex Fridman1:00:34

        Got you.

    30. KKKatherine de Kleer1:00:34

        ... where the sun is, all the things like that.
11. 1:06:15 – 1:11:25

    Weather patterns

    1. LFLex Fridman1:06:16

       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?

    2. KKKatherine de Kleer1:06:38

       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-

    3. LFLex Fridman1:08:14

       Mm-hmm.

    4. KKKatherine de Kleer1:08:14

       ... um, physically deep properties of, um, Jupiter's interior and, and circulation. Um...

    5. LFLex Fridman1:08:22

       What are the, these vortices? What, what's the basic material of the storms?

    6. KKKatherine de Kleer1:08:27

       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.

    7. LFLex Fridman1:08:48

       Oh.

    8. KKKatherine de Kleer1:08:49

       And sometimes measure it directly and, you know, different species make different colors as well.

    9. LFLex Fridman1:08:54

       Oh, cool.

    10. KKKatherine de Kleer1:08:55

        Um...

    11. LFLex Fridman1:08:55

        Ice storms, okay.

    12. KKKatherine de Kleer1:08:57

        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.

    13. LFLex Fridman1:09:13

        Yeah.

    14. KKKatherine de Kleer1:09:13

        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.

    15. LFLex Fridman1:09:45

        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.

    16. KKKatherine de Kleer1:10:01

        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-

    17. LFLex Fridman1:10:09

        Re-distribute, right.

    18. KKKatherine de Kleer1:10:09

        ... effectively. Uh...

    19. LFLex Fridman1:10:10

        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.

    20. KKKatherine de Kleer1:10:28

        Oh my goodness, yeah, so...

    21. LFLex Fridman1:10:29

        Even with the little variation we have on Earth.

    22. KKKatherine de Kleer1:10:31

        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.

    23. LFLex Fridman1:10:55

        Re-distribute.

    24. KKKatherine de Kleer1:10:55

        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.

    25. LFLex Fridman1:11:05

        Mm-hmm.

    26. KKKatherine de Kleer1:11:05

        And then you get to go back and learn something by how you have to modify the theory to make it fit.

    27. LFLex Fridman1:11:11

        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.

    28. KKKatherine de Kleer1:11:24

        (laughs)

12. 1:11:25 – 1:20:27

    Asteroids

    1. KKKatherine de Kleer1:11:25

       .

    2. LFLex Fridman1:11:25

       Uh, we talked quite a bit about planets and moons. Can we talk a little bit about asteroids?

    3. KKKatherine de Kleer1:11:31

       For sure.

    4. LFLex Fridman1:11:32

       What is, uh, what's an asteroid? And what kind of asteroids are there?

    5. KKKatherine de Kleer1:11:36

       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-

    6. LFLex Fridman1:11:46

       Mm-hmm.

    7. KKKatherine de Kleer1:11:46

       ... 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-

    8. LFLex Fridman1:14:08

       Oh wow, cool.

    9. KKKatherine de Kleer1:14:08

       ... basically. Um...

    10. LFLex Fridman1:14:10

        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-

    11. KKKatherine de Kleer1:14:29

        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.

    12. LFLex Fridman1:14:39

        Mm-hmm.

    13. KKKatherine de Kleer1:14:39

        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.

    14. LFLex Fridman1:15:26

        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?

    15. KKKatherine de Kleer1:15:51

        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.

    16. LFLex Fridman1:16:11

        Yeah.

    17. KKKatherine de Kleer1:16:11

        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.

    18. LFLex Fridman1:16:41

        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?

    19. KKKatherine de Kleer1:16:52

        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-

    20. LFLex Fridman1:17:17

        Yeah.

    21. KKKatherine de Kleer1:17:17

        ... 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-

    22. LFLex Fridman1:17:25

        Mm-hmm.

    23. KKKatherine de Kleer1:17:25

        ... 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.

    24. LFLex Fridman1:17:44

        Mm-hmm.

    25. KKKatherine de Kleer1:17:45

        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.

    26. LFLex Fridman1:18:20

        Is it hard to land on an asteroid? Is this, uh, is this- is this- is this a dumb question?

    27. KKKatherine de Kleer1:18:26

        (laughs) .

    28. LFLex Fridman1:18:26

        It feels like, uh, it would be quite difficult to actually operate a spacecraft in such a, uh, dense field of debris.

    29. KKKatherine de Kleer1:18:39

        Oh, the asteroid belt. Um, there's a ton of material there, but it's actually not that dense. It is mostly open space.

    30. LFLex Fridman1:18:45

        Okay.
13. 1:20:27 – 1:29:10

    Will an asteroid hit Earth soon?

    1. KKKatherine de Kleer1:20:27

    2. LFLex Fridman1:20:27

       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?

    3. KKKatherine de Kleer1:20:47

       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-

    4. LFLex Fridman1:21:00

       A lot of them.

    5. KKKatherine de Kleer1:21:01

       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.

    6. LFLex Fridman1:21:56

       Oh, wow.

    7. KKKatherine de Kleer1:21:56

       So, that is a close call, but people have studied it and, and apparently-

    8. LFLex Fridman1:22:01

       Yeah.

    9. KKKatherine de Kleer1:22:02

       ... are very confident it's not actually going to hit us, but it was-

    10. LFLex Fridman1:22:04

        We're gonna have to look into this-

    11. KKKatherine de Kleer1:22:05

        Yeah. (laughs)

    12. LFLex Fridman1:22:06

        ... '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."

    13. KKKatherine de Kleer1:22:26

        (laughs)

    14. LFLex Fridman1:22:26

        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.

    15. KKKatherine de Kleer1:22:42

        Mm-hmm.

    16. LFLex Fridman1:22:42

        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.

    17. KKKatherine de Kleer1:23:10

        (laughs)

    18. LFLex Fridman1:23:10

        Is there, uh, any chance that Bruce Willis can save us-

    19. KKKatherine de Kleer1:23:13

        (laughs)

    20. LFLex Fridman1:23:13

        ... 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.

    21. KKKatherine de Kleer1:23:37

        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?

    22. LFLex Fridman1:23:49

        5:00 PM.

    23. KKKatherine de Kleer1:23:50

        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-

    24. LFLex Fridman1:24:36

        Right.

    25. KKKatherine de Kleer1:24:36

        ... it's, it, it n-

    26. LFLex Fridman1:24:37

        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.

    27. KKKatherine de Kleer1:24:44

        (laughs)

    28. LFLex Fridman1:24:44

        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.

    29. KKKatherine de Kleer1:25:08

        Hmm.

    30. LFLex Fridman1:25:09

        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 encode that into whatever rocket that lands sufficiently to, I presume, humans, unlike the m- unlike the movies, humans w- would likely get in the way. Like, it should all be done by robots. And they could land, drill, place the, uh, the explosive. That should all be done through control through robots, and then you should be able to dynamically adjust to, um, to the surface. The flip side of that, for a robotics person, I don't know if you've seen these. It's been very heartbreaking. Uh, s- somebody I know well, Russ Tedrake at MIT, led the DARPA Robotics Challenge Team, uh, for the Humanoid Robot Challenge for DARPA. I don't know if you've seen videos of robots on two feet falling, but you're talking about millions, you know, e- several years of work from, with some of the most brilliant roboticists in the world, millions of dollars, and the final thing is a highlight video on YouTube of robots falling. But they had a lot-

Episode duration: 1:56:53