The following is a conversation with Catherine Duclir, 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.

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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 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 lexfreedman.com slash hiring.

That's where I will always post opportunities for working with me.

This is the Lex Friedman Podcast, and here is my conversation with Catherine DeClear.

Why is Pluto not a planet anymore?

Does this upset you or has justice finally been served?

So I get asked this all the time.

I think all planetary scientists get asked about Pluto, especially by kids who, we just

love for Pluto to still be a planet.

But the reality is, when we first discovered Pluto, it was a unique object in the outer

solar system.

And we thought 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.

And as we started discovering more and more of them, we realized that the concept of Pluto

being a planet didn't make sense unless maybe we added all the rest of them as planets.

So you could have imagined actually a different direction that this could have gone where

all the other objects that were discovered in that belt, or at least all the ones, let's

say, above a certain size, became planets instead of Pluto being declassified.

But we're now aware of many objects out there in the outer solar system and what's called

the Kuiper Belt that are of the same size or in some cases even larger than Pluto.

So 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 definition in such a way that took into account that

there's this belt of debris out there in the outer solar system of things with a range

of sizes.

Is there a hope for clear categorization of what is a planet and not, or is it all just

gray area?

When you study planets, when you study moons, satellites of those planets, is there lines

that could be cleanly drawn or is it just a giant mess?

Is it all like a fluid, let's say not mess, but it's like fluid of what is a planet, what

is a moon of a planet, what is debris, what is asteroids, all that kind of...

So there are technically clear definitions that were set down by the IAU, the International

Astronomy Union.

Is it size related?

Like what are the parameters based on?

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 extrasolar planets according to that definition are not planets.

So it has to orbit the sun.

It has to be large enough that its gravity has caused it to become spherical in shape,

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 have cleared out its orbital path.

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

Why didn't you clear out the path?

It's not big enough to knock everybody out of the way.

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, 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 it is important just for having

a general framework for understanding and talking about things to have a precise definition.

So you don't have a special romantic appreciation of a moon versus a planet versus an asteroid.

It's just an object that flies out there and it doesn't really matter what the categorization

is.

Because there's movies about asteroids and stuff, and then there's movies about the moon,

whatever, it's a really good movie.

There's something about moons that's almost like an outlier.

You think of a moon as a thing that's the secret part, and the planet is the more vanilla

regular part.

None of that?

You don't have any of that?

No, I actually do.

I really, satellites are, the moons are my favorite things in the solar system.

I think part of what you're saying, I agree from maybe a slightly different perspective,

which is from the perspective of exploration, 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.

The belt of debris, just real quick, that's out there.

Is there something incredible to be discovered there?

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 what, it just feels

like it's a cool, 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 weird things.

Or I guess in our conversation today, when we think about tools and what science is 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?

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.

We don't think it comes from outside the solar system, at least not most of it.

But there are so many fascinating objects out there and I think what you fit on is exactly

right that we just don't have the tools to study them in detail.

But we can look out there and we can see there are different species of ice on their surface

that tells us about, you know, the chemical composition 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.

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.

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 design devices or sensors

that go out there and take pictures and land?

Do you have to land to truly understand a little piece of rock or can you understand

it from remotely, like fly up close and remotely observe?

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.

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 fly by.

And so they did fly by another object out there in the Kuiper Belt and they take pictures

and they do what they can do.

And if you've seen the images from that mission of Pluto, you can see just how much detail

we have compared to just the sort of reddish dot that we knew of before.

So you do get an amazing amount of information actually from just essentially a high speed

flyby.

It always makes me sad to think about flybys that we might be able to, we might fly by

a piece of rock, take a picture and think, oh, that looks pretty and cool and whatever.

And that you could study 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 you know, like when you're on a deserted island and 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 miss it.

I don't know, some reason it makes me, it's the FOMO, it's fear of missing out.

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.

A sad pause, a Russian philosophical pause.

Okay.

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

Oh my goodness.

That is such a big question.

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 part of it falls under the heading of

astronomy.

And among the things that you can study with telescopes, like solar system moons 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, trying to detect tectonic tremors on its surface.

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.

So you like telescopes, not rockets, or at least 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.

But telescopes, it's amazing how much detail and how much information you can get from

telescopes today.

You can resolve 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 lava flows expand.

So and then, you know, spectroscopy, you get compositional information on all these things

and it's, 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.

So with the telescope, you can, I mean, how much information can you get about volcanoes,

about storms, about sort of weather, just so we kind of get a sense, like what a resolution

we're talking about?

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 and actually watch 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.

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.

Can we just zoom in on certain things like, let's talk about Io, which is the moon of

Jupiter.

Right.

Okay.

It's so big.

There's like volcanoes all over the place.

It's from a distance.

It's awesome.

So can you tell me about this moon and you're sort of a scholar of many planets and moons,

but that one kind of stood out to me.

So why is that an interesting one?

For so many reasons, but Io is the most volcanically active object in the solar system.

It has hundreds of active volcanoes on it.

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.

But I think to me, the reason that it's most interesting is as a laboratory for understanding

planetary processes.

So one of the broad goals of planetary science is to put together a sort of more general

and coherent framework 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.

But then when you try to transport that to somewhere like Io that doesn't have an atmosphere,

which has a very tenuous atmosphere, which makes a big difference for how the magma degasses,

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, the kind of intuition we have from

Earth doesn't apply.

And so broadly, planetary science is trying to broaden that framework so that you have

a kind of narrative that you can understand how each planet became different from every

other planet.

And I'm already making a mistake.

When I say planet, I mean planets and moons.

Like I said, I see the moons as planets.

As planets.

Yeah.

I actually already noticed that you didn't introduce Io as the moon of Jupiter.

You completely, you kind of ignored the fact that Jupiter exists.

It's like, let's focus on this.

Yeah.

Okay.

So, and you also didn't mention Europa, which I think is the, is that the most famous moon

of Jupiter?

Is that the one gets attention because it might have life?

Exactly.

Yeah.

But to you, Io is also beautiful.

What's the difference between volcanoes on Io versus Earth?

You said atmosphere makes a difference.

What the heat source plays a big role.

So many of the moons in the outer solar system are heated from gravitationally by tidal heating.

And I'm happy to describe what that is or, yeah, please, what's tidal?

Yes.

So tidal heating is, it's, if you want to understand and contextualize planets and moons,

you have to understand their heat sources.

So for Earth, we have radioactive decay in our interior as well as residual heat of formation.

But for satellites, tidal heating plays a really significant role and in particular

in driving geological activity on satellites and potentially making those subsurface oceans

in places like Europa and Enceladus habitable.

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.

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.

But because they're always meeting each other at the same point in the orbit, those gravitational

interactions add up coherently.

And so that tweaks them into eccentric orbits.

What's an eccentric orbit?

So eccentric orbit or elliptical orbit, it just means noncircular, so a deviation from

a circular orbit.

And that means that 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 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.

And so you actually have the shape of the object deforming over the course of the orbit.

And these 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.

That's the source of the magma.

Yeah.

Okay.

So why is, so Europa is, I thought there was like ice and oceans underneath kind of thing.

So why is Europa not getting the friction?

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 three object orbital resonance in the Jupiter system.

But we have these sorts of orbital resonances all over the solar system and also in exoplanets.

So for Europa, basically because it's farther from Jupiter, the effect is not as extreme,

but you do still have heat 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 for life.

Cool.

So it's like heating up the ocean a little bit.

Heating up the ocean a little bit.

And specifically in these like hydrothermal vents where we see really interesting life

evolve in the bottom of Earth's oceans.

That's cool.

Okay.

So what's Io, 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 you and I were to visit Io, like what would

that look like?

What would it feel like?

Is this the entire thing covered in basically volcanoes?

So 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 a thousand degrees or the magma when

it comes out is over a thousand degrees.

And so.

But it does come to the surface, the magma?

It does.

Yeah.

In particular places.

Whoa, that probably looks beautiful.

So like, so it's frozen, not ice.

Like what is, is rock, it's really cold rock.

And then you just have this like, what is, what does that look, what would that look

like with no atmosphere?

Would that, uh, would it be smoke?

What does it look like?

It's just magma, like just red, yellow, like liquidy things?

It's black, it's black and red, I guess.

Like think of 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 will flow out in sheets because

it has really low viscosity.

And I think the lava flows that we've been having in Hawaii over the past couple of years

are probably a decent analogy, although Io's magma's lavas are even more fluid and faster

moving.

How faster?

Like what, uh, how fat, like if you, uh, by the way, sorry, through the telescope, are

you tracking at what timescale?

Like every frame is how far apart?

If you're looking through a telescope, are we talking about seconds or we're talking

about days, months, when you kind of track, try to get a picture of what the surface might

look like, what's the frequency?

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 timescale, you to

actually see something change that fast, you have to have super high resolution.

The spatial resolution we have is a couple of hundred kilometers.

And so things are not changing on those scales over one second, unless you have something

really crazy happening.

So if you get, 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?

Would you be able to understand something deeper about these volcanic eruptions and

how magma flows and just the, like the rate of the magma is, or is it basically enough

to have the kilometer resolution?

Do you get it?

No way.

We want to go there.

Absolutely.

You want to go, you want to go to Io?

I mean, I don't want to go there personally, but I want to send a spacecraft mission there.

Absolutely.

Why?

Why are you scared?

Why am I scared?

Oh, you mean you don't like, I don't want to go there as a human as a human.

I want to send a robot there to look at it though.

This is again, everybody's discriminating against robots.

This is not, but it's fine.

But it's not hospitable to humans in any way, right?

Just very cold and very hot.

It's very cold.

The atmosphere is composed of sulfur dioxide, so you can 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 is still a thousand times less

dense than Mars is.

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.

So Jupiter's magnetic field strips all this material out of Io's atmosphere and that populates

its entire magnetosphere and then that material comes back around and hits Io and spreads

throughout the system actually.

It's just, it's like Io is the massive polluter of the Jupiter system.

Okay, cool.

So what does studying Io teach you about volcanoes on earth or vice versa?

Is in the difference of the two, what insights can you mine out?

That might be interesting in some way.

Yeah.

Well, 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 because the situations are so different and the compositions

are really different.

When you talk about outgassing, you know, earth volcanoes outgassed primarily water

and carbon dioxide, and then sulfur dioxide is the third most abundant gas.

And on Io, the water and carbon dioxide are not there, either it didn't form with them

or it lost them, we don't know.

And so the chemistry of how the magma outgassed this is completely different.

But the kind of one to me most interesting analogy to earth is that, so Io, as I've said,

it has these really low viscosity magmas, 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 had this, what we call very effusive

volcanism early in their history.

Okay, so this is almost like a little glimpse into the early history of earth.

Yeah.

Okay, cool.

So what are the chances that a volcano on earth destroys all of human civilization?

Maybe I wanted to sneak in that question.

Yeah, a volcano on earth.

Do you think about that kind of stuff when you just study volcanoes elsewhere?

Because 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?

Right.

Yeah, Yellowstone is a classic example.

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

wiped out by some other means, that maybe it'll happen eventually, that there'll be

one of these massive volcanoes on earth, but we'll probably be gone by then by some other

means.

Not to sound bleak.

That's very comforting.

Okay, so can we talk about Europa?

Is there, so maybe can you talk about the intuition, the hope that people have about

life being in 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?

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'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.

The radiation environment is too harsh and there's just not liquids on the surface of

most of these things and it's canonically accepted that liquids are required for life.

And so the subsurface oceans, in addition to maybe Titan's atmosphere, the subsurface

oceans of the icy satellites are one of the most plausible places in the solar system

for life to evolve.

Europa and Cellitus 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 they have these ice shells and then there's an ocean underneath the ice shell.

But on those moons around 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.

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 water interface is considered really important for the potential habitability.

As a small aside, you kind of said that it's canonically assumed that water is required

for life.

Is it possible to have life like in a volcano?

I remember people were like in that 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?

I think anything's possible.

I think so.

It doesn't have to be water.

You can tell, as you identified, I phrased that really carefully.

It's canonically accepted that because 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 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 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.

That'd be fascinating.

I mean, it'd be fascinating if it's possible to detect it easily.

How would we detect if there is life on Europa?

Is it possible to do in a noncontact way from a distance through telescopes and so on?

Or do we need to send robots and do some drilling?

I think realistically you need to do the drilling.

So Europa also has these long tectonic features on its surface where it's thought that 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.

But your instrument could detect some spectroscopic signature of that dead bacterium.

But that's many ifs and assumptions.

That's a hope because then you don't have to do that much drilling.

You can collect from the surface.

Skeletons of bacteria.

Right.

I'm thinking even remotely.

Oh, remotely.

Yeah.

That's sad that there's a single cell civilization living underneath all that ice trying to get

up.

Trying to get out.

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

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 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.

But let's say that you have some ingenuity and can come up with a way to do that.

It potentially gives you a more direct opportunity at least to try to measure those bacteria

directly.

Can you tell me a little more on, how do you pronounce it, Salas?

Enceladus.

Enceladus.

Can you tell me a little bit more about Enceladus?

Like we've been talking about way too much about Jupiter, Saturn doesn't get enough love.

Saturn doesn't get as much love.

So what's Enceladus?

Is that the most exciting moon of Saturn?

Depends on your perspective.

It's very exciting from a astrobiology perspective.

I think Enceladus and Titan are the two most unique and interesting moons of Saturn that

definitely both get the most attention also from the life perspective.

So what's the more likely Titan or Enceladus for life?

If you were to bet all your money in terms of like investing, which to investigate, what

are the differences between the two that are interesting to you?

Yeah.

So the potential for life in each of those two places is very different.

So Titan is the one place in the solar system where you might imagine, again, all of this

is so speculative, but you might imagine life evolving in the atmosphere.

So from 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 an atmosphere denser than Earth's 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's effectively doing prebiotic chemistry

in the atmosphere.

While still being freezing cold?

Yes.

Okay.

What would that be like?

Would that be pleasant for humans to hang out there?

It's just really cold?

There's nowhere in the solar system that would be pleasant for humans.

It would be cold.

You couldn't breathe the air.

But colonization wise, if there's an atmosphere, isn't that a big plus?

Or still a ton of radiation?

Sure.

Okay.

So Titan, that's a really nice feature that life could be in the atmosphere because then

it might be remotely observable or certainly is more accessible if you visit.

Okay.

So what about Enceladus?

So that would be still in the ocean.

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 globally liquid over the age of the solar system.

And so there are some models that say that it's going through this cyclical evolution

where the ocean freezes completely and thaws completely and the orbit sort of oscillates

in and out of these eccentricities.

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?

It also means there might be mass extinction events if it does occur and then it just freezes.

Again, very sad, man.

This is very depressing, all the slaughter of life elsewhere.

How unlikely do you think life is on Earth?

So when you study other planets and you study the contents of other planets, does that give

you a perspective on 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, like from nothing to life,

from the basic ingredients to life?

I guess another way of asking it is how unique are we?

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.

We don't know whether it's happened anywhere else in the universe, although 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.

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 in terms of the odds of origins of life on Earth, I mean, this

all has to do with how special and unique is Earth.

What you land in terms of the number of civilizations has to do with how unique their 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 completely unscientific question, well, no,

it's actually a 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 that are Earth like planets, it's getting better and better understood.

What's your sense from that perspective, how many alien civilizations out there, zero or

one plus?

You're right that the equation is being better understood, but you're really only talking

about the first three parameters in the equation or something.

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 given habitable

conditions, how likely is it to survive, all these things.

There are all these huge unknowns.

Actually I remember when I first saw that equation, I think it was my first year of

college and I thought this is ridiculous.

This is A, common sense that didn't need to give a name, you know, and B, just a bunch

of unknowns, it's like putting our ignorance together in one equation.

But now I understand this equation, you know, it's not something we'll ever necessarily

have the answer to, it just gives us a framework for having the exact conversation we're having

right now.

And I think that's how it was intended in the first place when it was put into writing

was to give people a language to communicate about the factors that go into the potential

for aliens to be out there and for us to find them.

I would put money on there being aliens, I would not put money on us having definitive

evidence of them in my lifetime.

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

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 obsessed that we literally would not

be able to detect them.

Even when they're like in front of us, like trees could be aliens, but just their intelligence

could be realized on a scale, on a time scale or physical scale that we're not appreciating.

Like trees could be way more intelligent than us.

I don't know.

It's just a dumb example.

It could be rocks or it could be things like, this, I love this, this is a Dawkins memes.

It could be that ideas are the, 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 physics, right?

This is like, we think of thoughts as something that springs up from neurons firing or where

the hell they come from.

And now what about consciousness?

Maybe consciousness is the communication.

It sounds like ridiculous, but like we're so self centered on this space, time, communication

and physical space using like written language, like spoken with audio on a time scale that's

very specific on a physical scale, it's very specific.

So I tend to think that, but bacteria will probably recognize like moving organisms will

probably recognize, but when that forms itself into intelligence, most likely it'll be robots

of some kind because we won't be meeting the origins.

We'll be meeting the creations of those intelligences.

We just would not be able to appreciate it.

And that's the saddest thing to me that we, yeah, we're too dumb to see aliens.

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 0.0001% of understanding

anything is humbling.

I hope that's true because I feel like we're very ignorant as a species.

And I hope that our current level of knowledge only represents the 0.001% of what we will

someday achieve.

That actually feels optimistic to me.

Well, 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 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 so there's much more, like physicists are much more confident.

Biologists are like, uh, this is a squishy mess, we're doing our best, physicists, but

I would be, it'd be fascinating to see if physicists themselves would also be humbled

by their being like, what the hell is dark matter and dark energy?

What the hell is the, not just the origin of the, not just the big bang, but 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.

Right.

What happened before the big bang?

Yeah.

Yeah.

What happened before?

Or what's happening inside the black hole?

Why is there a black hole at the center of our galaxy?

Can somebody answer this?

A supermassive 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 consciousness.

Okay.

Um, all right, back to planets.

How, um, what's your favorite outside of earth?

What's your favorite planet or moon?

Maybe outside of the ones we, well, first, have we talked about it already or, and then

if we did mention it, what's the one outside of that?

Oh gosh.

I have to come up with another favorite that's not IO.

Oh, IO is the favorite.

Oh, absolutely.

Why is IO the favorite?

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 was the thing that like really caught me in to doing solar system science.

Okay.

Let's, let's leave, uh, moons aside.

What's your favorite planet?

It sounds like you like moons better than planets.

So it's, uh, that's accurate.

Um, but the planets are, are fascinating.

I think, you know, I find that 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 still the,

the bigger questions.

Gotcha.

Um, which, you know, I, and maybe I'm being unfair to the planets because we're 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, 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 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'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 love volcanism for some reason, and, and Venus has, probably

has volcanic activity, definitely has in their recent past, maybe has ongoing today.

What do you make of the news and maybe you can update it in terms of life being discovered

in the atmosphere 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 a life on Venus?

So the detection that was reported was the detection of the molecule phosphine.

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 train of logic.

And, um, I don't personally believe that phosphine was detected in the first place.

Okay.

So then, I mean, this is just one study, but I, as a layman, I'm skeptical a little bit

about tools that sense the contents of an atmosphere, like contents of an atmosphere

from remotely and making conclusive statements about life.

Oh yeah.

Well that connection that you just made, the contents of the atmosphere to the life 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, did, doesn't, doesn't meet the sort of historical scientific

standards of, 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.

Yeah.

Um.

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 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.

Clearly.

Yes.

Everyone is so excited about that possibility.

All right.

Let's, uh, let me ask you about Mars.

So, um, there's a guy named Elon Musk and, uh, he seems to want to take something called

Dogecoin there.

First of the month.

I'm just, I'm just kidding about the Dogecoin.

I don't even know what the heck is up with that whole, um, I think, uh, I think humor

has power in the 21st century in a way to spread ideas in the most positive way.

So I love that kind of humor because it makes people smile, but it also kind of sneaks.

It's like a Trojan horse for cool ideas.

You you open with humor and you, uh, like the humor is the appetizer.

And then the main meal is the science and the engineering anyway, uh, do you think it's

possible to colonize Mars or other planets in the solar system, but we're especially

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 in a high like big picture

perspective, do you have a hope we, we do in fact become a multi planetary species?

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 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 go

into Mars as a tourist may go to Mars.

Um, I don't think that we will colonize it.

Um, is there a sense why it's just too harsh on the environment to, uh, to, to, like it's

too costly to build something habitable there for a large population.

I think that we need to do a lot of work and learning how to use the resources that are

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 we'll 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 going to 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 that's going to be a major obstacle

in going from visiting where we can bring everything we need to survive in the short

term to actually colonizing.

Yeah.

I find that whole project of the human species quite inspiring these like huge moonshot projects.

Somebody I was reading something, um, in terms of the source of food that's 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 before living on Mars because that's the easiest

thing to actually, um, as a source of protein.

So growing a source of protein is the easiest thing as insects.

I just imagine this giant for people who are afraid of insects.

This is not a pleasant, maybe you're not supposed to even think of it that way.

It'd be like a cockroach milkshake or something like that.

Right.

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

them radiation friendly, right.

Or pressure resistant or whatever.

What can possibly go wrong with making radiation resistant, they're already like survived everything.

Plus I, um, I took an allergy test, um, in Austin.

So there's everybody's alert is like the allergy levels are super high there.

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

It's hilarious.

So maybe, uh, um, well, I'm going to use that as a, you know, people use, uh, an excuse

that I'm allergic to cats to not have cats.

I'm going to use that as an excuse to, uh, not go to Mars as one of the first batch of

people.

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

Yeah, I'm joking about the cockroach thing.

I would definitely go.

I love challenges.

I love, I love things.

I love doing things where the possibility of death is, is, uh, not insignificant because

it makes me appreciate it more.

Meditating on death makes me appreciate life.

And uh, when the meditation on death is forced on you because of how difficult the task is,

I enjoy those kinds of things.

Most people don't, it seems like, 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, 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 the 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 has 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 going out there.

But, uh, so that's, that's hopeful, but for me, I always loved that idea.

From a alien scientist perspective, if you were to look back on earth, is there something

interesting you could say about earth?

Like, how would you summarize earth?

Like in a report, you know, like, uh, Hitchhiker's Guide to the Galaxy, like if you had to report,

like write a paper on earth 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.

I was going to say that's where I was going to 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 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, 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...

Oh, really?

So the other planets don't have plate tectonics?

It's the only one that has plate tectonics.

Yeah.

What about Io and the friction and all that, that's not plate tectonics?

What's the difference between...

Oh, it's plate tectonics, like another layer of like solid rock that moves around and there's

cracks.

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.

Through the freezing cold crust?

Yes.

Very cold, very rigid crust.

Yeah.

How do you, how does that look like, by the way?

I don't think we've mentioned, so the gas that's expelled, like if we were to look at

it, is it beautiful or is it like boring?

The gas?

I mean, the whole thing, like the magma punching through, the icy...

Oh my gosh.

Yes, I'm sure it would be beautiful, and the pictures we've seen of it are beautiful.

You have, so 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, 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 viscosity magma, sort of water like, coming out of these sheets.

And the plumes that come out, because there's no atmosphere, all the plume molecules are

just plume particles, where they end up is just a function of the direction that they

left the vent, so they're all following ballistic trajectories, 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 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 condense onto these particles, and you'd have sulfur

dioxide snow coming out of these volcanic plumes.

And there's not much light, though, right?

So you wouldn't be able to, like, it would not make a good Instagram photo, because you

have to, would you see the snow?

Sure.

There's light.

It depends.

Oh, okay.

So you could, okay.

It depends what angle you're looking at it, where the sun is, all the things like that.

You know, the sunlight is much weaker, but it's still there.

It's still there.

And how big is Io in terms of gravity?

Is it smaller?

Is it a pretty small moon?

It's quite a bit smaller than Earth anyway.

It's smaller than Earth.

Okay.

Okay.

Cool.

So they float up for a little bit.

So it floats.

Wow.

Yeah.

No, you're right.

That would be gorgeous.

What else about Earth is interesting besides volcanoes?

So plate tectonics.

I didn't realize that that was a unique element of a planet in the solar system, because that,

I wonder what, I mean, we experienced as human beings, it's quite painful because of earthquakes

and all those kinds of things, but I wonder if there's nice features to it.

Yeah.

So coming back to habitability again, things like tectonics and plate tectonics are thought

to play an important role in the surface being habitable.

And that's because you have a way of recycling materials.

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.

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 that can kind

of refresh your nutrient supply, in a sense, or the sort of raw materials that the surface

has to work with.

So from a kind of astrobiologist perspective, looking at Earth, you would see that recycling

of material because 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 in addition to, of course, the, you know, pleasant temperature and liquid

water.

But the abundance of oxygen and the plate tectonics both play a role as well.

And also see like tiny dot satellites flying around and rockets.

Well, sure, yes.

I wonder if they would be able to, I really think about that, like, if aliens were to

visit, and 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, because there's like so much incredible,

in terms of biomass, humans are a tiny, tiny, tiny fraction.

There's like ants, they would probably detect ants, right?

Or they probably would focus on the water and the fish because there's like a lot of

water.

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.

Or on land?

On land.

Not in the sea?

No.

Not in the sea.

Not in the sea, but no, the variety that like the branches created by evolution, apparently

it's probably a good answer from 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, it's not diversity friendly.

What can I say?

It needs to improve its diversity.

Do you think the aliens would come, I mean, the first thing they would see is I suppose

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?

Yeah.

I mean, there's, 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 geometric

shapes.

Like if it's, cause to me like hard corners, like what do we think is engineered?

Things that are like, have kind of straight lines and corners and so on, they would probably

detect those in terms of buildings would stand out to them because that's, that goes against

the basic natural physics of the world.

But I don't know if the electricity and lights and so on, it could be, I honestly, it could

be the plate tectonics.

It could be like, that they're 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.

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, we're very human.

We think we're one organism, but that may not be the case.

They might see, in fact, they may also see like a human city as one organism.

Like what is this thing that like, clearly this organism gets aroused at night because

the lights go on and then, and then it like, it sleeps during the day.

I don't know how, like the, what perspective you take on the city.

Is there something interesting about earth or other planets in terms of weather patterns?

So we talked a lot about volcanic patterns.

Is there something else about weather that's interesting, like storms or variations in

temperature, all those kinds of things?

Yeah.

So there's sort of every planet and moon has a kind of interesting 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 global circulation patterns of many of

these atmospheres, why the storm systems occur.

So the composition and occurrence of storms and clouds and these objects is another one

of these kind of windows into the interior that I was talking about with surfaces.

One of these ways that we can get perspective and what the composition is at 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.

But looking at where those occur 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 just insane.

There's so much going on.

You look at these pictures and there's all these vortices and antivortices and you have

these different bands that are moving in opposite directions that may be giving you information

about the deep, like deep in the atmosphere, physically deep properties of Jupiter's interior

and circulation.

What are these vortices?

What's the basic material of the storms?

It's condensed molecules from the atmosphere.

So ammonia ice particles 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 and sometimes measure it directly and different species

make different colors as well.

Oh, cool.

Ice storms.

Okay.

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.

So sometimes the sunlight's a little bit above the equator and sometimes it's a little bit

below the equator.

But on Uranus, it's like 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's actually kind of amazing that the atmosphere doesn't look crazier than it does.

But understanding how, 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 understanding

of how atmosphere is.

So like heats up one side of the planet for 10 years and then freezes it the next, like,

and that you're saying should probably lead to some chaos.

And it doesn't.

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 effectively.

Right.

So they have a stabilizing, like self regulating aspect to them that they're able to deal with

extreme conditions.

But predicting how that complex system unrolls is very difficult, as we know, about predicting

the weather on Earth even.

Oh, my goodness.

Yeah.

Even with the little variation we have on Earth.

You know, people have tried to put together global circulation models.

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.

So Titan, for example, like I said, 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 happen moving into sort of the next season of Titan.

And those predictions have ended up being wrong.

And so then, you know, 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.

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

it fit.

I'm excited by the possibility of one day there will be for various moons and planets,

there will be like news programs reporting the weather with the fake confidence of like

as if you can predict the weather.

We talked quite a bit about planets and moons.

Can we talk a little bit about asteroids?

For sure.

What is, what's an asteroid?

And what kind of asteroids are there?

So the asteroids, let's talk about just the restricted to the main asteroid belt, which

is the region, it's a region of debris basically between Mars and Jupiter.

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, are

remnant objects from the origin of the solar system.

And so one of the reasons that we are so interested in them, aside from potentially the fact that

they could come hit Earth, but scientifically it's, it gives us a window into understanding

the composition of the material from which Earth and the other planets formed and how

that material was kind of redistributed over 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 sort of disc of material that the whole solar system formed

out of and have kind of remained ever since more or less the same.

They've probably collided with each other and we see the, all these collisional fragments

and you can actually look and based on their orbits say, you know, like these 50 objects

originated as the same object.

You can see them kind of dynamically moving apart after some big collision.

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 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 crests.

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 basically.

So it's like puzzle pieces that you might be able to stitch together or I guess 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, I mean, there's too many objects in there to.

I think that there are cases where people 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.

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 our surface and then we can see it, but, you know, sort

of in bulk.

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 getting irradiated and all

that.

But it's a cool potential window or like analogy into the interior of our own planet.

Well, how do you begin studying some of these asteroids?

What if you were to put together a study, like what are the interesting questions to

ask that are a little bit more specific?

Do you find a favorite asteroid that could be tracked and try to track it through telescopes?

Or do you, is it has to be, do you have to land on those things to study it?

So when it comes to the asteroids, there are so many of them and the big pictures or the

big questions are answered, so some questions can be answered by zooming in in detail on

individual object, but mostly you're trying to do a statistical study.

So you want to look at thousands of objects, even hundreds of thousands of objects 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 kinds of statistical properties of the asteroid belt.

And those properties can be directly compared with the results of simulations for the formation

of the solar system.

What do we know about the surfaces of asteroids or the contents of the insides of asteroids

and what are still open questions?

So I would say that we don't know a whole lot about their compositions.

Most of them are small and so you can't study them in such detail with telescopes 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, but you can't really like get a statistical survey

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 how bright they are, you look at whether they're red or blue, simply, you

know, whether their spectrum is sloped towards long wavelengths or short wavelengths.

There are certain, if you point a spectrograph at their surfaces, there are certain features

you can see.

So you can tell that some of them have silicates on them.

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'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 classify them into these categories.

There's still a huge amount of room for understanding them better and for understanding how their

surfaces are changing in the space environment.

Is it hard to land on an asteroid?

Is this a dumb question?

It feels like it would be quite difficult to actually operate a spacecraft in such a

dense field of debris.

Oh, the asteroid belt, there's a ton of material there, but it's actually not that dense.

It is mostly open space.

So mentally do picture like mostly open space with some rocks.

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.

And so there's not necessarily.

Might look like a rock, but 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?

Like what are we supposed to be visualizing here?

This is like very few have water, right?

There's some water in the outer part of the asteroid belt, but they're not quite like

comets in the sense of having clouds around them.

There are some crazy asteroids that do become active like comets.

That's the whole other category of thing that we don't understand.

But their surfaces, I mean, we have visited some, you can find pictures that spacecraft

have taken of them.

We've actually scooped up material off of the surface of some of these objects.

We're bringing it back to analyze it in the lab.

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.

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.

Is there this, do you worry about this?

Is there any chance that one of these fellas destroys all of human civilization by an asteroid

kind of colliding with something, changing its trajectory and then heading its way towards

earth?

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 a lot of them.

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.

Have you, are you aware of this Apophis object?

So there's an asteroid, a near earth object called Apophis that people thought had 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 going to be visible in the sky in a relatively dark, I mean, not even that dark, probably

not visible from Los Angeles, but, and it's going to come a 10th of the way between the

earth and the moon.

It's going to come closer apparently than some geosynchronous communication satellites.

Oh wow.

So that is a close call, but people have studied it and apparently are very confident it's

not actually going to hit us, but it was.

I'm going to have to look into this because I'm very sure, I'm very sure what's going

to 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.

And then last minute they'll be like, there was a miscalculation.

They're not lying.

It's just like the space of possibilities, because it's very difficult to track these

kinds of things and there's a lot of kind of, um, there's complexities involved in this.

There's a lot of uncertainties that I just, something tells me that human civilization

will end with, we'll see it coming.

And then last minute there'll be a, oops, we'll like, we'll see it coming and we'll,

it'll be like, no, it's just, it's just threatening, but no problem.

No problem.

And last minute it'll be like, oops, that was a miscalculation.

And it's all over in a matter of like a week, or just very positive and optimistic today.

Is there any chance that Bruce Willis can save us in the sense that from what you know

about asteroids, is there something that, um, you can catch them early enough to, uh,

change volcanic, uh, eruptions, right, um, sort of drill, put a nuclear weapon inside

and break up the asteroid or change its trajectory?

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, um, depending on the objects and how close, 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 it's, it's like a terminator too.

When it's like the thing that just like you shoot it in splashes and then comes back together

will be very useless.

That's fascinating.

It was 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.

And but then we have an understanding about surfaces here on earth, we can map up a lot

of things.

I wonder if we can do that.

Some kind of detail of being able to have that same level of precision in landing on

surfaces with as wide of a variety as asteroids have 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, unlike the movies, humans would likely get in the way.

Like it should all be done by robots and like land drill, place the, the explosive that

should all be done through control, the 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, somebody I know well, Russ Tedrick at MIT led the DARPA robotics challenge team 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, 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 of trouble with uneven surfaces.

That's basically what you have to do with, uh, the challenge involves you're mostly autonomous

with some partial human communication, but that human communication is broken up.

Like you don't get a, you get a noisy channel, so you can, humans can, which is very similar

to what it would be like in humans remotely operating a thing on an asteroid.

And so with that, robots really struggled.

There's some hilarious painful videos of like a robot, not able to like open the door.

And then it tries to open the door without like, it misses the handle and in doing so

like falls, I mean, it's, um, it's painful to watch.

So like that, there's that, and then there's SpaceX.

So I have hope from SpaceX and then I have less hope from bipedal robotics, um, but it's

fun.

It's fun to kind of imagine.

And I think the planetary side of it comes into play in understanding the surfaces of

these asteroids more and more that, you know, forget sort of destruction of human civilization.

It'd be cool to have like spacecraft just landing on all these asteroids to study them

at scale and being able to figure out dynamically what, you know, whether it's a rubble pile

or whether it's, um, a solid objects, like, do you see that kind of future of science?

Maybe a hundred, 200, 300 years from now, where there's just robots expanding out through

the solar system, like sensors, essentially.

Some of it taking pictures from a distance, some of them landing, just exploring and giving

us data.

Cause it feels like we're working with very little data right now.

Sure I, I do see exploration going that way.

I think, um, the way that NASA is currently or historically has been doing missions is

putting together these, these really large missions that do a lot of things and are extremely

well tested and have a very low rate of failure.

But now that, um, these sort of CubeSat technologies are, are becoming easier to build, easier

to launch, they're, they're very cheap.

And you know, NASA is getting involved in this as well.

There's, there's a lot of interest in these missions that are relatively small, relatively

cheap and just do one thing.

So you can really optimize it to just do this one thing.

And maybe you could build a hundred of them and send them to different asteroids.

And they would just collect this one piece of information from each asteroid.

It's a kind of different, more distributed way of doing science, I guess.

And there's a ton of potential there, I agree.

Let me ask you about objects or one particular object from outside our solar system.

We don't get to study many of these, right?

They don't, we don't get stuff that just flies in out of nowhere from outside the solar system

and flies through.

Apparently there's been two recently in the past few years.

One of them is Amuamua.

What are your thoughts about Amuamua?

So fun to say.

Could it, could it be space junk from a distant alien civilization or is it just a weird shaped

comet?

I like the way that's phrased.

Um, so Amuamua is, is a fascinating object.

Just the fact that we have started discovering things that are coming in from outside our

solar system is amazing and can, can start to study them.

And now that we have seen some, we can design now kind of thinking in advance.

The next time we see one, we will be much more ready for it.

We will know which telescopes we want to point at it.

We will have explored whether we could even launch a fast turnaround mission to actually

like get to it before it leaves the solar system.

In terms of Amuamua, yeah, it's, for an object in our solar system, it's really unusual in

two particular ways.

One is the dimensions that we don't see natural things in our solar system that are kind of

long and skinny.

We see, the things we see in our solar system don't deviate from spherical by that much.

And then that it showed these strange properties of accelerating as it was leaving the solar

system, which was not understood at first.

So in terms of the alien space junk, you know, as a scientist, I cannot rule out that possibility.

I have no evidence to the contrary.

Um, however,

See, you're saying there's a chance.

I cannot, I cannot, as a scientist, honestly say that I can rule out that it's alien space

junk.

However, I see the kind of alien explanation as following this, the Sagan's extraordinary

claims require extraordinary evidence.

If you are going to actually claim that something is aliens, you need to carefully evaluate,

everyone needs to carefully evaluate the other options and see whether it could just be something

that we know exists that makes sense.

In the case of Oumuamua, there are explanations that fit well within our understanding of

how things work.

So there are a couple, there are two hypotheses for what it could be made of.

They're both basically just ice shards.

In one case, it's a nitrogen ice shard that came off of something like Pluto in another

solar system, that Pluto got hit with something and broke up into pieces, and one of those

pieces came through our solar system.

In the other scenario, it's a bit of a failed solar system.

So our solar system formed out of a collapsing molecular cloud.

Sometimes those molecular clouds are not massive enough, and they sort of collapse into bits,

but they don't actually form a solar system, but you end up with these kind of chunks of

hydrogen ice, apparently.

And so one of those chunks of hydrogen ice could have got ejected and passed through

our solar system.

So both cases explain these properties in about the same way.

So those ices will sublimate once they've passed the sun, and so as they're moving away

from the sun, you have the hydrogen or nitrogen ice sublimating off the sunward part of it,

and so that is responsible for the acceleration.

The shape also, because you have all this ice sublimating off the surface, if you take

something, the analogy that works pretty well here is for a bar of soap.

Your bar of soap starts out sort of close to spherical, at least from a physicist perspective,

and as you use it over time, you eventually end up with this long, thin shard because

it's been just by sort of weathering, as we would call it.

And so in the same way, if you just sublimate material off of one of these ice shards, it

ends up long and thin, and it ends up accelerating out of the solar system.

And so given that these properties can be reasonably well explained that way, we should

be extremely skeptical about attributing things to aliens.

See, the reason I like to think that it's aliens is because it puts a lot of priority

on us not being lazy and we need to catch this thing next time it comes around.

I like the idea that there's objects, it almost saddens me, they come out of the darkness

really fast and just fly by and go and leave.

It just seems like a wasted opportunity not to study them.

It's the easiest way to do space travel outside of the solar system is having the things come

to us.

Right?

I like that way of putting it.

And it would be nice to just land on it.

And first of all, really importantly, detect it early and then land on it with a really

nice spacecraft and study the hell out of it.

If there's a chance it's aliens, alien life, it just feels like such a cheap way, inexpensive

way to get information about alien life or something interesting that's out there.

And I'm not sure if an ice shard from another planetary system will be interesting, but

it very well could be.

It could be totally new sets of materials.

It could be, tell us about composition of planets we don't quite understand.

And it's just nice when, especially in the case of a Moa Moa, I guess it was pretty

close to earth.

It would have been nice to, don't go there, they come to us, I don't know.

That's what makes me quite sad.

It's a missed opportunity.

Well, yeah.

And whether you think it's aliens or not, it's a missed opportunity, but we weren't

prepared and we will be prepared for the next ones.

So there's been a movement in astronomy more towards what's called time domain astronomy.

So kind of monitoring the whole sky all the time at all wavelengths.

That's kind of the goal.

And so we expect to detect many more of these in the future, even though these were the

first two we saw, our potential to detect them is only increasing with time.

And so there will be more opportunities and based on these two, we now can actually sit

and think about what we'll do when the next one shows up.

I also, what it made me realize, I know I didn't really think through this, but it made

me realize if there is alien civilizations out there, the thing we're most likely to

see first would be space junk.

My stupid understanding of it.

And the second would be really dumb kind of, you could think of maybe like relay nodes

or something objects that you need to have a whole lot of for particular purposes of

like space travel and so on.

Like a speed limit signs or something, I don't know, whatever we have on earth, a lot of

that's dumb.

It's not alien aliens in themselves.

It's like artifacts that are useful to the engineering in the systems that are engineered

by alien civilizations.

So like it would, we would see a lot of stuff in terms of setting, in terms of looking for

alien life and trying to communicate with it.

Maybe we should be looking not for like smart creatures or systems to communicate with.

Maybe we should be looking for artifacts or even as dumb as like space junk.

It just kind of reframed my perspective of like, what are we looking for as signs?

Cause there could be a lot of stuff that doesn't have intelligence, but gives us really strong

signs that there's somewhere is life or intelligent life.

And yeah, that made me kind of, I know it might be dumb to say, but reframe the kind

of thing that we should be looking for.

Yeah.

So the benefit of looking for intelligent life is that we perhaps have a better chance

of recognizing it.

We couldn't necessarily recognize what an alien stop sign look like.

And maybe the theorists are the people who sort of model and try to understand slow system

objects are pretty good at coming up with models for anything.

I mean, maybe a mua mua was a stop sign, but we're clever enough that we could come up

with some physical explanations for it.

And then we all want to go with the simplest possible, we all want to believe the sort

of most skeptical possible explanation.

And so we missed it because we're too good at coming up with alternate explanations for

things.

And it's such an outlier, such a rare phenomenon that we can't study a hundred or a thousand

of these objects.

We have to, we had just one.

And so the science almost destroys the possibility of something special being there.

It's like Johnny Ive, this designer of Apple, I don't know if you know who that is.

He's the lead designer.

He's the person who designed the iPhone and all the major things.

And he talked about, he's brilliant, one of my favorite humans on earth and one of the

best designers in the history of earth.

He talked about like when he had this origins of an idea, like in his baby stages, he would

not tell Steve Jobs because Steve would usually like trample all over it.

He would say, this is a dumb idea.

And so I sometimes think of the scientific community in that sense, because the weapon

of the scientific method is so strong at its best that it sometimes crushes the out of

the box outlier evidence.

We don't get a lot of that evidence because we don't have, we're not lucky enough to have

a lot of evidence.

So we have to deal with just special cases and special cases could present an inkling

of something much bigger, but the scientific method user tramples all over it.

And it's hard to know what to do with that because the scientific method works, but at

the same time, every once in a while, it's like a balance.

You have to do 99% of the time, you have to do like scientific rigor, but every once in

a while, this is not you saying, me saying, smoke some weed and sit back and think, I

wonder, you know, it's the Joe Rogan thing.

It's entirely possible that it's alien space junk.

Anyway.

Yeah.

I think so.

I completely agree.

And I think that most scientists do speculate about these things.

It's just at what point do you act on those things?

So you're right that the scientific method has inherent skepticism, and for the most

part, that's a good thing because it means that we're not just believing crazy things

all the time.

But it's an interesting point that requiring that high level of rigor occasionally means

that you will miss something that is truly interesting because you needed to verify it

three times and it wasn't verifiable.

I also think like when you communicate with the general public, I think there's power

in that 1% speculation of just demonstrating authenticity as a human being, as a curious

human being.

I think too often, I think this is changing, but I saw, I've been quite disappointed in

my colleagues throughout 2020 with the coronavirus.

There's too much speaking from authority as opposed to speaking from curiosity.

There's some of the most incredible science has been done in 2020, especially on the virology

biology side.

And the kind of being talked down to by scientists is always really disappointing to me as opposed

to inspiring.

Like the things we, there's a lot of uncertainty about the coronavirus, but we know a lot of

this stuff and we speak from scientists from various disciplines, speak from data in the

face of that uncertainty.

And we're curious, we don't know what the hell is going on.

We don't know if this virus is going to evolve, mutate.

We don't know if this virus or the next one might destroy all human civilization.

You can't speak with certainty.

In fact, I was on a survey paper about masks, something I don't talk much about because

I don't like politics, but we don't know if masks work, but there's a lot of evidence

to show that they work for this particular virus.

The transmission of the virus is fascinating actually.

The biomechanics of the way viruses spread is fascinating.

If it wasn't destructive, it would be beautiful.

And we don't know, but it's inspiring to apply the scientific method to the best of our ability,

but also to show that you don't always know everything and to, perhaps not about the virus

as much, but other things speculate.

What if, you know, what if it's the worst case and the best case?

Because that's ultimately what we are, descendants of apes that are just curious about the world

around us.

Yeah, I'll just add to that, not on the topic of masks, but on the topic of curiosity.

I mean, I think that's, astronomy and planetary sciences, a field are a little, are unique

because for better and for worse, they don't directly impact humanity.

So you know, we're not studying virology to prevent transmission of, you know, illness

amongst humans.

We're not characterizing volcanoes on earth that could destroy cities.

We, it really is a more curious and in my opinion, playful scientific field than many.

So for better and worse, we can kind of afford to pursue some of the speculation more because

human lives are not in danger if we speculate a little bit too freely and get something

wrong.

Yeah, definitely.

In the space of AI, I am worried that we're sometimes too eager, speaking for myself,

to like flip the switch to on just to see like what happens.

Maybe sometimes we want to be a little bit careful about that because bad things might

happen.

Is there books or movies in your life long ago or recently that were inspiring, had an

impact on you that you would recommend?

Yeah, absolutely.

So many that I just don't know where to start with it.

So I love reading.

I read obsessively.

I've been reading fiction and a little bit of nonfiction, but mostly fiction obsessively

since I was a child and just never stopped.

So I have some favorite books.

None of them are easy readings.

So I definitely, I mean, I recommend them for somebody who likes an intellectual challenge

in the books that they read.

So maybe I should go chronologically.

I have at least three.

I'm not going to go through 50 here.

Yeah, I'd love to also like maybe ideas that you took away from what you mentioned.

Yeah.

Yeah.

Why they were so compelling to me.

One of the first books that really captured my fascination was Nabokov's book Pale Fire.

Are you familiar with it?

So I read it actually for a class.

It's one of the few books I've ever read for a class that I actually really liked.

And the book is, it's in some sense a puzzle.

He's a brilliant writer, of course, but the book is like, it's formatted like a poem.

So there's an introduction, a very long poem and footnotes, and you get partway through

it before realizing that the whole thing is actually a novel, unless you sort of read

up on it going in.

But the whole thing is a novel and there's a story that slowly reveals itself over the

course of all of this and kind of reveals this just fascinating character basically

and how his mind works in this story.

The idea of a novel also being a kind of intellectual puzzle and something that slowly reveals itself

over the course of reading was really fascinating to me and I have since found a lot more writers

like that.

In a contemporary example that comes to mind is Kazuo Ishiguro, who's pretty much all of

his books are like slow reveals over the course of the book and like nothing much happens

in the books, but you keep reading them because you just want to know like what the reality

is that he's slowly revealing to you.