Speaker 1: Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2: Hello, and welcome to Stuff to Blow Your Mind. My
Speaker 2: name is Joe McCormick. My regular co host, Robert Lamb
Speaker 2: is out on vacation the day I'm recording this, but
Speaker 2: he will be back again soon. Today we've got an
Speaker 2: interview for you. This is a chat that I had
Speaker 2: with planetary scientist doctor Sabine Stanley about her twenty twenty
Speaker 2: three book called What's Hidden Inside Planets. This is a
Speaker 2: wonderfully interesting book about the science of planet formation and
Speaker 2: about what we know about the insides of planets near
Speaker 2: and far. A quick bit of author bio before we
Speaker 2: get started here. Doctor Sabine Stanley is a distinguished planetary
Speaker 2: scientist and a key contributor to NASA's Mars Insight mission.
Speaker 2: Holding a PhD in Earth and Planetary Sciences from Harvard
Speaker 2: u University, she focuses on the complexities of planetary interiors.
Speaker 2: Currently a faculty member at a top research university, she
Speaker 2: leads innovative studies in her specialized field. Beyond academia, Doctor
Speaker 2: Stanley is a regular speaker at international scientific conferences and
Speaker 2: serves as a consultant for various space missions. Her research
Speaker 2: has been published in leading scientific journals, earning her multiple
Speaker 2: awards for her contributions to planetary science. With a career
Speaker 2: that blends rigorous research and public engagement, Doctor Stanley remains
Speaker 2: a pivotal voice in the scientific community committed to enhancing
Speaker 2: our cosmic understanding. So I guess now let's jump right
Speaker 2: into our conversation, Doctor Sabine Stanley, Welcome to the podcast.
Speaker 3: Thanks so much for having me.
Speaker 2: So I wanted to start off with the idea something
Speaker 2: you bring up in the preface of your book, which
Speaker 2: is that when non scientists look out at space and
Speaker 2: find things to get excited about, one of the things
Speaker 2: I think that really gets people stirring is the idea
Speaker 2: of an exoplanet with liquid water at the surface, or
Speaker 2: a planet with breathable atmosphere breathable to us. And yet
Speaker 2: you say in your preface that quote, arguably a planet's
Speaker 2: interior is more important than the surface in determining a
Speaker 2: world's fitness for life or ability to withstand the pressures
Speaker 2: put on it by its home star. I think this
Speaker 2: might be really surprising to people. Could you explain this?
Speaker 3: Sure, there are actually two parts to this I would
Speaker 3: say the first is deep inside our planet, in the
Speaker 3: iron core, we actually generate the Earth's magnetic field, and
Speaker 3: magnetic fields when they are generating the core, they come
Speaker 3: all the way out to the surface of the planet
Speaker 3: and they basically surround the planet, and our magnetic field
Speaker 3: acts as this amazing shield stopping these high energy solar
Speaker 3: wind particles from hitting us. Now, when you have these
Speaker 3: high energy particles coming from the Sun, if they actually
Speaker 3: blast it into the planet without the magnetic field there,
Speaker 3: they would work to strip off our atmosphere. They would
Speaker 3: bring high radiation levels to the surface. It would essentially
Speaker 3: not be a really great place to live if we
Speaker 3: didn't have our magnetic field. So one really important thing
Speaker 3: when thinking about is that planet going to be really
Speaker 3: good for say, life to form, is does it have
Speaker 3: a magnetic field and that's really created in deep inside
Speaker 3: the planet. The other aspect of this is that most
Speaker 3: of the reasons that we think the surface of Earth
Speaker 3: is so nice and habitable, right the liquid water, that
Speaker 3: breathable air, all of that is related to a kind
Speaker 3: of recycling process that happens inside Earth. Earth's water a
Speaker 3: lot of it came from outgassing a volcano. So there's
Speaker 3: water deep inside the Earth. When you have volcanic flows
Speaker 3: bringing up magma to the surface, there's lots of gas,
Speaker 3: particles and water in that that eventually makes it out
Speaker 3: into the atmosphere. Carbon dioxide is recycled this way. Water
Speaker 3: is recycled this way. So you can't really just focus
Speaker 3: on the surface. You have to ask how does that
Speaker 3: surface interact with what's going on deep inside planet.
Speaker 2: So when people imagine what's going on deep inside the
Speaker 2: planet and the way it affects the surface, probably what
Speaker 2: first comes to the average non scientist's mind would be
Speaker 2: like earthquakes and volcanic eruptions, But actually it's much more
Speaker 2: entangled than that.
Speaker 3: Yeah. Absolutely, But those are also great examples of ways
Speaker 3: that the interior of our planet is really connected to
Speaker 3: how we experience the surface of a planet. Earthquakes, that's
Speaker 3: because the plates on the surface of the Earth are
Speaker 3: moving around and they descend back into the Earth at
Speaker 3: subduction zones and create these frictional spots between plates that
Speaker 3: create these earthquakes. Right.
Speaker 2: Another great example, there's a false fact that I once
Speaker 2: knew that your book corrected me on if you had
Speaker 2: asked me what was the source of Earth's magnetic field
Speaker 2: that you were just talking about. I would have said
Speaker 2: that it was generated by the spinning of the molten
Speaker 2: liquid core around the Earth's solid iron core because of
Speaker 2: the image of spinning, and I guess there's general knowledge
Speaker 2: that sort of dynamo effect, But in the book you
Speaker 2: explained that that isn't exactly correct. That's not exactly what's
Speaker 2: going on. So what does generate the Earth's magnetic field?
Speaker 3: Yeah, you're absolutely right. This is a common misunderstanding out there,
Speaker 3: even some scientists have it. So it turns out in
Speaker 3: order to generate magnetic fields, you do need to have
Speaker 3: a good electrical conductor, and so having a metal like
Speaker 3: iron in this center of the Earth that helps. You
Speaker 3: do need to have it be liquid or fluid ability
Speaker 3: to move around. But the key thing is the motions
Speaker 3: that can create magnetic fields through, like this dynamo action
Speaker 3: that you talked about. Those motions have to be much
Speaker 3: more complex than just spinning around. So it's not just
Speaker 3: that the Earth is spinning and that's causing it. It's
Speaker 3: actually these like helical type flows that occur because of
Speaker 3: the fact that the Earth is trying to cool down,
Speaker 3: so space is cold. The inside of Earth is hot.
Speaker 3: And so just like if you put a pot of
Speaker 3: soup on the stove, the bottom of the pot is hot,
Speaker 3: the top of the pot is cold. You get that
Speaker 3: boiling action that rolling around. Same thing in the core
Speaker 3: of the Earth, you get these churning motions as the
Speaker 3: hot material at the center of the Earth tries to
Speaker 3: make it up and out to cool down the core
Speaker 3: and then the planet. So it's convection, that's what we
Speaker 3: call it. It's convection. That's the motion that's actually creating
Speaker 3: the magnetic field that Earth has.
Speaker 2: So it's this magnetic dynamo that creates the field that
Speaker 2: can in some ways permit and sustain life on Earth.
Speaker 2: To what extent is Earth unique in this regard? What
Speaker 2: do we know about the presence of a possible dynamo
Speaker 2: in other planets or objects in our Solar system?
Speaker 3: Yeah, great question. So lots of the other planets actually
Speaker 3: do have magnetic field. So all the giant planets, Jupiter, Saturn, Uranus,
Speaker 3: and Neptune, they all have these global magnetic fields generated
Speaker 3: by a dynamo deep inside just like Earth. The smallest
Speaker 3: of the planet's mercury also has a dynamo, and this
Speaker 3: was actually quite a surprise when it was discovered. Now,
Speaker 3: for Mars, it doesn't have a dynamo today, so it
Speaker 3: doesn't have this global MAGNETELD, but it did have one
Speaker 3: in the past. So about four billion years ago, the
Speaker 3: rocks on the surface of Mars were magnetized from a
Speaker 3: dynamo that was active at that time. And then there's Venus.
Speaker 3: For Venus, we have no way to tell if it
Speaker 3: ever had a dynamo in the past. It does not
Speaker 3: have one today.
Speaker 2: You bring up Venus, and there's a funny thing you
Speaker 2: mentioned toward the end of the book, which is the
Speaker 2: frustrations that Venus presents planetary scientists, especially the ones who
Speaker 2: want to study the interior of the planet. Why is
Speaker 2: Venus so frustrating? Why is it so hard to study?
Speaker 3: Yeah, Venus is the worst planet in the Solar System.
Speaker 3: I'm just going to put that out there right now.
Speaker 3: Here's the issue, right, it's really hard to study the
Speaker 3: insides of planets. You don't have access to it. You
Speaker 3: can't drill down and study the core of a planet
Speaker 3: that way, so you have to develop all these really
Speaker 3: clever methods to try and figure out what's going on
Speaker 3: deep inside the Earth. A lot of methods that are
Speaker 3: kind of like what doctors use to figure out what's
Speaker 3: going on inside the human body. Right, We do scans
Speaker 3: of things, we use gravity, we use magnetic fields, we
Speaker 3: use seismology. So then you try and use any of
Speaker 3: these techniques on Venus, and they don't work for a
Speaker 3: variety of different reasons. So first of all, let's say
Speaker 3: we wanted to use seismology, right, So the waves that
Speaker 3: pass through a planet when you have an earthquake, for example,
Speaker 3: on Earth, the speed of those waves is completely determined
Speaker 3: by the material properties they are passing through. So we
Speaker 3: actually learn a lot about what the materials are inside
Speaker 3: the Earth by looking at how fast these seismic waves
Speaker 3: travel through it. You want to do this on Venus, Sorry,
Speaker 3: the surface is a horrible temperature, and the atmosphere is
Speaker 3: made of sulphuric acid, and the pressure is ninety two
Speaker 3: atmospheric pressures, so it's just the materials are just going
Speaker 3: to melt and dissolve basically, so no chance to do that.
Speaker 3: Then you try and use a magnetic field, right, Having
Speaker 3: a magnetic field is a great way to learn about
Speaker 3: the interior of a planet. As soon as you know
Speaker 3: a planet has a global magnetic field, you know, it's
Speaker 3: got a liquid molten electrical conductor in its interior, and
Speaker 3: it's got those churning motions. Well, Venus doesn't have that,
Speaker 3: so we can't use that. And you try and say, okay, well,
Speaker 3: why don't we just observe the surface and look at
Speaker 3: the rotation of the surface, for example, while Venus has
Speaker 3: this horribly opaque atmosphere that you can't actually look through
Speaker 3: and try to do that. And then one of my
Speaker 3: favorite things about Venus is that when you look at
Speaker 3: all the planets, all the planets, you know we talk
Speaker 3: about planets being spheres, they're not spheres. They're actually kind
Speaker 3: of bulgy oblate spheroids, we call them. So they're fatter
Speaker 3: across the equator than they are at the poles, and
Speaker 3: that bulging of the equator is because of the fact
Speaker 3: that the planet's spin. Now we can use that information
Speaker 3: how bulgey a planet is to actually tell what material
Speaker 3: is inside it, how dense it is inside it. And
Speaker 3: you go and try and do this at Venus, and
Speaker 3: Venus is rotating so slowly that it basically has no bulge.
Speaker 3: So we can't use that either. Basically, Venus is just
Speaker 3: very frustrating doesn't want us to know anything about its interior.
Speaker 2: So there's a great section in the chapter Gazing Outward
Speaker 2: where in this chapter you're talking about the formation of
Speaker 2: our Solar System from the orig original molecular cloud that
Speaker 2: came together to make the Sun and the planets the
Speaker 2: protoplanetary disc. And you talk about how the interesting ways
Speaker 2: the connections between the features of that initial cloud and
Speaker 2: features of the current Solar System and even everyday life
Speaker 2: on Earth. So, for example, the elemental composition of that
Speaker 2: vast cloud determines the elements that make our Solar System,
Speaker 2: but also more interesting and subtle things like how the
Speaker 2: slight initial rotation of that cloud governs so much about
Speaker 2: our world. Could you talk about some of these connections
Speaker 2: between the properties of the cloud and the way the
Speaker 2: Solar System is now?
Speaker 3: Yeah? Absolutely, So. I remember once sitting there and just thinking,
Speaker 3: you know, okay, yeah, we know that the planet's orbit
Speaker 3: around the Sun, we know that the planets are spinning.
Speaker 3: Why is everything spinning all right? Why don't doesn't anything
Speaker 3: just stay still? And the answer has to do with
Speaker 3: this great concept in physics called angular momentum conservation. So basically,
Speaker 3: you can't just change the spin of something without putting
Speaker 3: a lot of torque on it, like forcing it. Right.
Speaker 3: And so then you put something out in the middle
Speaker 3: of nowhere, a molecular cloud, right, and you don't have
Speaker 3: anything really torquing it or anything, and you ask, well,
Speaker 3: how much spin is it going to have? And it's
Speaker 3: going to have some random amount, right, like nothing's perfectly
Speaker 3: isolated and still, so you take all those particles in
Speaker 3: the molecular cloud and you add up all their spins,
Speaker 3: and a lot of them will cancel out. Someone will
Speaker 3: be spinning in one direction, other particles will be spinning
Speaker 3: in the other direction. And you add it all up
Speaker 3: and it almost all cancels out except for a little bit.
Speaker 3: And that little bit in a molecular cloud. Here's the
Speaker 3: amazing thing. Once gravity gets hold of that molecular cloud,
Speaker 3: it starts gravitationally collapsing to eventually form our solar system.
Speaker 3: That amount of spinning just increases and increases and increases
Speaker 3: as the cloud gets smaller and smaller and smaller. And
Speaker 3: you have a total understanding. People have a total understanding
Speaker 3: of this effect. If you've ever watched, for example, figure
Speaker 3: skaters who are about to do a jump with a
Speaker 3: spin it and they pull their arms in. As soon
Speaker 3: as you make something more compact, it spins faster, even
Speaker 3: though you don't do anything to it. And the same
Speaker 3: thing happened to the molecular cloud. As it became smaller
Speaker 3: and smaller and smaller, it spin faster and faster and faster.
Speaker 3: And that's what led to all the spinning we have
Speaker 3: in the Solar System now. And this is true not
Speaker 3: just of our Solar System. We can look out and
Speaker 3: see other Solar systems forming. We can see other planets
Speaker 3: around other stars. They're all spinning too. It's all the
Speaker 3: kind of we share that among all the planets.
Speaker 2: We call the roughly spherical objects that orbit stars planets,
Speaker 2: and we call the objects that orbit planets moons. But
Speaker 2: are there any other material differences between a planet and
Speaker 2: the moon? Are there even any trends?
Speaker 3: Yeah, it's a great question. So moons can be complicated.
Speaker 3: So in reality, if you're someone like me who's interested
Speaker 3: in the interior of planets, you're just as happy to
Speaker 3: consider moon's planets. Right, Moons for their they're made of
Speaker 3: similar stuff. They have the same laws of physics that
Speaker 3: govern their interior. We have moons that have magnetic fields. Ganymede,
Speaker 3: which is a moon of Jupiter, actually has a magnetic
Speaker 3: field generated in its core. So we study the same
Speaker 3: processes on these bodies. Where moons can be a little
Speaker 3: bit different than planets, there's a lot bigger possibility of
Speaker 3: where they came from compared to where they ended up.
Speaker 3: So for example, the rocky planets in the Inner Solar System, Mercury, Venus, Earth, Mars,
Speaker 3: they all pretty much formed close to where they are now.
Speaker 3: Some moons actually come from very far away and then
Speaker 3: get trapped in the gravitational field of a planet and
Speaker 3: then become a moon there. And that happens a lot,
Speaker 3: for example in the Outer Solar System. So if you
Speaker 3: look at Jupiter or Neptune or any of these planets,
Speaker 3: some of their moons are on these really weird orbits.
Speaker 3: They're like orbiting in the opposite direction as the planet
Speaker 3: is spinning. They're not around the equator at all. And
Speaker 3: those moons we think are actually captured basically comets. They're
Speaker 3: captured comets or asteroids that were doing their own thing
Speaker 3: got gravitationally kicked into the Solar System a little bit
Speaker 3: close in and then got trapped around a planet. So
Speaker 3: you can actually find some bodies orbiting these planets that
Speaker 3: were probably formed much further away, and so in that sense,
Speaker 3: that's a little bit different than what you see with planets.
Speaker 2: One of the most shocking facts that you discussed in
Speaker 2: the book concerns the formation of the Earth's moon. Now,
Speaker 2: I know the leading theory on the formation of the
Speaker 2: Earth's moon is the giant impact idea, but specifically, the
Speaker 2: thing that you introduced to me was how rapidly the
Speaker 2: Earth's moon was probably formed according to the leading theory
Speaker 2: of its origin. Could you explain this.
Speaker 3: Yeah, this blows my mind. By the way, so we're
Speaker 3: somewhat I think people have heard of this theory that
Speaker 3: something about the size of Mars, usually called they crashed
Speaker 3: into Earth, had this kind of glancing impact into pro
Speaker 3: to Earth Earth. This was like four point five billion
Speaker 3: years ago, and that crash caused some of that body
Speaker 3: and some of the Earth to get kind of blasted
Speaker 3: off the surface of the planet and small chunks were
Speaker 3: put into orbit. And then you ask the question, Okay,
Speaker 3: so now you have this disk of material surrounding the Earth.
Speaker 3: How long did it take for that disk of material
Speaker 3: to become the Moon a single object? Now, that disk
Speaker 3: of material followed the same laws of physics as the
Speaker 3: planet's forming out of the disc. Initially on gravity caused collisions.
Speaker 3: Some of those collisions caused things to clump together. Eventually,
Speaker 3: the Moon grew and grew and grew, and estimates suggest
Speaker 3: it took forty years for this to happen. Now, when
Speaker 3: you're talking about things in astronomy and in Earth science,
Speaker 3: you're working on millions of years, billions of years. Those
Speaker 3: are the types of lengths of time we're used to.
Speaker 3: So talking about a process that takes forty years is
Speaker 3: just shocking. And so I always have this image in
Speaker 3: my head, and this is obviously impossible because it was
Speaker 3: four point five billion years ago, But I have this
Speaker 3: image in my head of like some parents sitting down
Speaker 3: with their kids and the parents going, you know, when
Speaker 3: I was your age, there was no moon in the
Speaker 3: sky kind of thing, right like that. It's on a
Speaker 3: human generational timescale that this changed.
Speaker 2: That's truly unbelievable. And you actually mentioned several other things
Speaker 2: about the Moon that I didn't quite know about and
Speaker 2: were so interesting one is that it's a parent magnitude
Speaker 2: from the Earth was larger initially, I guess because it
Speaker 2: was closer. But you also mentioned something called a fossil
Speaker 2: bulge in the moon. Could you explain these?
Speaker 3: So when the Moon formed, it was much closer to
Speaker 3: the Earth, and since then it's been slowly receding away
Speaker 3: from the Earth. And we can even measure this change
Speaker 3: in distance of the Moon to the Earth. And that's
Speaker 3: happening because of really interesting gravitational interaction between the Moon
Speaker 3: and the Earth. And it's the same reason, for example,
Speaker 3: that the Moon only shows us one face, so tidal interactions,
Speaker 3: the fact that you know, the Earth's not a perfect sphere,
Speaker 3: the Moon's not a perfect sphere, and they tug on
Speaker 3: each other when are not kind of facing the right way.
Speaker 3: That has caused the Moon to start moving further away.
Speaker 3: It's also caused the Earth to start slowing down its
Speaker 3: rotation a little bit, and so over time, the Moon's
Speaker 3: moving further away and it's going to make it smaller
Speaker 3: and smaller and smaller. And one reason we know all
Speaker 3: of this is that the moon, if you look at
Speaker 3: how bulgy it is, Like I talked about how spinning
Speaker 3: objects have this bulge on them. The Moon is too
Speaker 3: bulgy for how fast it's spinning right now, and the
Speaker 3: only way to explain that is it must have been
Speaker 3: spinning faster in the past. And the only way for
Speaker 3: it to have been spinning faster in the past is
Speaker 3: if it was much closer to the Earth, because we
Speaker 3: know it's locked. It's day is locked to the Earth's
Speaker 3: you know, it's always facing the Earth the same side,
Speaker 3: so it had to have a much faster spin in
Speaker 3: order to get that bulge that it had.
Speaker 2: With exoplanets, we often hear about the habitable zone of
Speaker 2: a star, the area of the distance out from a
Speaker 2: star that we believe there could be the conditions possible
Speaker 2: for life to arise. But an interesting fact you mentioned
Speaker 2: is that if a faraway exoplanet astronomer we're looking at
Speaker 2: our Solar system, they would see not one but three
Speaker 2: planets within our habitable zone, Earth, Venus, and Mars. But
Speaker 2: neither of the other two planets, Mars or Venus are
Speaker 2: especially hospitable now, and Venus is really inhospitable. So what
Speaker 2: does that tell us about looking for exoplanets that could
Speaker 2: sustain life elsewhere?
Speaker 3: I think it tells us that we have to be
Speaker 3: a little more subtle in how we figure out whether
Speaker 3: a planet is a good candidate for some of that
Speaker 3: might have life or not. Right, totally, get why we
Speaker 3: are using these criteria right now. Right, what's the distance
Speaker 3: from a planet star at which the temperatures are just
Speaker 3: right so that water could be liquid on the surface
Speaker 3: if there was water there. That's kind of the condition
Speaker 3: we're using now. But as mentioned, planets are complicated, and
Speaker 3: you could have a planet that comple letly changes its
Speaker 3: surface temperature through a greenhouse, a runaway greenhouse effect. That's
Speaker 3: what happened on Venus. Right, Venus is getting not that
Speaker 3: much more heat from the Sun as we are, but
Speaker 3: it happened to go through this climate process, this runaway
Speaker 3: greenhouse that made the temperture on the surface incredibly hot
Speaker 3: and not able to sustain any water. The water all
Speaker 3: evaporated off of Venus. So we have to be a
Speaker 3: little bit more careful. We need to understand the dynamics
Speaker 3: of what's going on inside the bodies and outside, because
Speaker 3: that's what creates the atmospheres. Another great example of this,
Speaker 3: I think we also need to kind of broaden the
Speaker 3: search for habitable worlds, let's say, because if you look
Speaker 3: in our Solar system, aside from Earth, the next best
Speaker 3: place to possibly look for where life might form are
Speaker 3: actually in the water oceans of some of the moons
Speaker 3: in the outer Solar System. Now, these oceans are buried
Speaker 3: like miles beneath the surface, but they're liquid water, they
Speaker 3: have energy sources, they have complex carbon molecules, all the
Speaker 3: kind of ingredients that we think might be important for life.
Speaker 3: So I think we need to think more carefully about
Speaker 3: what the conditions are for life on exoplanets out there,
Speaker 3: and we might end up finding life in places we
Speaker 3: didn't expect.
Speaker 2: So when trying to understand what's inside planets, we've talked
Speaker 2: about using detection methods for like magnetic fields and seismic
Speaker 2: research and things like that. But what can isolated pieces
Speaker 2: of physical evidence like meteorites and diamonds tell us about
Speaker 2: how planets are formed and what's inside them.
Speaker 3: Yeah, this is one of my favorite things in the world.
Speaker 3: So I'm going to start with the diamonds thing. We
Speaker 3: really would like to actually have samples from deep inside
Speaker 3: the Earth, because that would be the best way to
Speaker 3: study it. It's impossible to do this, we can't drill
Speaker 3: deeper than about eight miles or something like that, right,
Speaker 3: and the earth goes down about almost three thousand miles, right,
Speaker 3: So this is just not possible, luckily for us. Sometimes
Speaker 3: the Earth brings samples from the deep up to the surface,
Speaker 3: and one thing it does is it brings up diamonds.
Speaker 3: Lots of people know about diamonds because they're important in
Speaker 3: say the jewelry industry, things like that, And when you're
Speaker 3: someone who's a jeweler, what you really care about are
Speaker 3: these pure diamonds, the things that are just pure carbon
Speaker 3: and diamond form. When you're a geologist or someone who's
Speaker 3: studying the in tier of the earth, you want the
Speaker 3: impure diamonds. You want the diamonds where some little bit
Speaker 3: of the interior of the Earth got stuck in the
Speaker 3: middle of the diamond as it was forming. And because
Speaker 3: diamonds are so hard, they actually maintain their pressure, and
Speaker 3: so when they come up to the surface, that little
Speaker 3: bit of material from deep inside the Earth actually stays
Speaker 3: preserved in the inside of that diamond. And so we
Speaker 3: can actually study materials how they are in the deep
Speaker 3: interior of the Earth by looking at these inclusions in
Speaker 3: the diamonds when they come to the surface. So that's
Speaker 3: one thing. Now, meteorites are like the best Christmas gift
Speaker 3: anyone could ever get from other planets. Right. Basically, you
Speaker 3: have some sort of collision or something that happened far
Speaker 3: away that caused a piece of a planet or an
Speaker 3: asteroid to get knocked off. Eventually that piece of the
Speaker 3: asteroid came near Earth and some of it landed on
Speaker 3: Earth and we can go and collect it. That's rarely
Speaker 3: where you have samples of the insides of other planets,
Speaker 3: and we even have meteorites that are very iron rich
Speaker 3: that come from the cores of previous planetary asteroid like
Speaker 3: bodies that got broken up. So one of the best
Speaker 3: pieces of evidence we have for what's in our core
Speaker 3: is actually looking at the cores of other bodies. They're
Speaker 3: all very similar. They all have this iron rich cores
Speaker 3: that eventually come to Earth and we get to study them.
Speaker 2: This reminds me there's an object that you mentioned several
Speaker 2: times in the book that I feel like I can
Speaker 2: tell you are especially excited about, and it is the
Speaker 2: asteroid sixteen Psyche. What makes Psyche so exciting?
Speaker 3: So, first of all, there is a mission on its
Speaker 3: way to Psyche right now, So we are going to
Speaker 3: study this asteroid up close and personal, and I'm very
Speaker 3: excited about that. I think in our Solar System, we're
Speaker 3: used to different kinds of worlds. Right You've got the
Speaker 3: rocky worlds of the inner planets in the Solar System,
Speaker 3: You've got the gas giants like that Are and Saturn.
Speaker 3: You've got the water worlds like you're in a a Neptune,
Speaker 3: and even some of the moons we can consider water
Speaker 3: World's Europa Enceladus moons like that. Sixteen. Psyche is a
Speaker 3: metal world. So this is a body that is mostly
Speaker 3: made of iron. It's mostly metal, and we just haven't
Speaker 3: seen that before. And I'm really excited about what it's
Speaker 3: going to be like to go look at this thing
Speaker 3: and you know, answer questions like, hmm, what does a
Speaker 3: crater look like on a body that's mostly made of metal? Is?
Speaker 3: What does a volcano look like on this thing? Does
Speaker 3: it have a magnetic field? What's really going on on
Speaker 3: the surface. So it's very exciting. It's a new type
Speaker 3: of planetary body that we've never gotten to see up
Speaker 3: close and personal.
Speaker 2: I think you mentioned the idea of a metal volcano.
Speaker 2: That's a real thing. What does that mean?
Speaker 3: We're going to find out, But imagine this is you know,
Speaker 3: this is an asteroid that's big enough that it could
Speaker 3: have stuff going on in the interior. You could have
Speaker 3: some of them iron from the interior being liquid and
Speaker 3: getting kind of taken up out of the interior onto
Speaker 3: the surface at these volcanic vents. So, yeah, we might
Speaker 3: get to see a metal volcano up close.
Speaker 2: Coming back to looking inside planets, if you go beyond
Speaker 2: Earth and even beyond the rocky planets, one of the
Speaker 2: most fascinating questions to ponder is what's inside the gas
Speaker 2: planets and the ice giants. I suspect you've seen the
Speaker 2: many variations on the article or video. What is it
Speaker 2: like to fall into Jupiter or something like that. It's
Speaker 2: clearly a captivating question because we see these outer cloud
Speaker 2: layers and there's just this you question, like, obviously, you
Speaker 2: imagine you're denser than some outer part of that cloud
Speaker 2: layer and you could sync down into it, and you've
Speaker 2: got to wonder what's inside. So what do we know
Speaker 2: about what is inside the gas giants and the ice giants?
Speaker 3: Yeah, this is one of my favorite things to talk about.
Speaker 3: So we are so accustomed to how materials behave in
Speaker 3: the types of conditions we have here on the surface
Speaker 3: of the Earth. If I just say the word water,
Speaker 3: you have a natural instinctive reaction to what water is.
Speaker 3: It's either that liquid in my glass, or maybe it's
Speaker 3: frozen on some ice somewhere, or it's water vapor that's
Speaker 3: causing fog. Right, you put water under the high pressures
Speaker 3: and high temperatures that are deep inside planets, it's a
Speaker 3: completely different beast. Same thing is true for hydrogen. So
Speaker 3: let's start there. Hydrogen the most kind of the simplest
Speaker 3: element we have, thing that we're used to being in
Speaker 3: gaseous form. Now in Jupiter and in Saturn. As you
Speaker 3: keep descending into the planet, temperatures are rising, you get
Speaker 3: to millions of degrees, you can get to millions of
Speaker 3: atmospheres of pressure. Hydrogen is a very different material under
Speaker 3: that pressure, and in fact, is you squeeze a hydrogen molecule,
Speaker 3: you basically allow So imagine hydrogen molecule. You got a
Speaker 3: proton at the center and the nucleus, and you got
Speaker 3: this electron floating around. You squeeze enough of those close
Speaker 3: together the electrons essentially get freed from the protons and
Speaker 3: you create what's called what we call a metal. So
Speaker 3: you can actually have metallic hydrogen going on inside Jupiter
Speaker 3: and Saturn, and it's a great electrical Conductor's actually where
Speaker 3: Jupiter creates its magnetic field, same with Saturn. So that's
Speaker 3: kind of a material we're not expected. Interestingly, helium take
Speaker 3: another one, the second most simple element we have, helium.
Speaker 3: You do the same thing. The helium. Turns out that
Speaker 3: in the outer layers of Jupiter and Saturn in the atmosphere,
Speaker 3: helium and hydrogen are nicely mixed. Right. It's kind of
Speaker 3: like if you put salt in water or sugar in
Speaker 3: water warm water and you stir it. They're nicely mixed.
Speaker 3: You can't kind of separate them, but you put them
Speaker 3: under high enough pressure. When this hydrogen becomes a nice metal,
Speaker 3: the helium no longer wants to stay mixed in it,
Speaker 3: and so helium will actually kind of exolt out of
Speaker 3: the hydrogen and become these droplets, and then helium's heavier
Speaker 3: than hydrogen, so they drop out. It rains helium inside
Speaker 3: Jupiter and Saturn. So I think that's really cool. Then
Speaker 3: you get to the ice giants, where you have a
Speaker 3: lot more complicated molecules methane, ammonia, and you say, okay,
Speaker 3: what happens to those things under high pressure, and you
Speaker 3: can get things, for example, like super ionic water that's
Speaker 3: actually formed in where all the oxygen atoms form a
Speaker 3: nice lattice and all the hydrogen the protons that would
Speaker 3: make up water in the H two O flow freely
Speaker 3: between it, something we've never seen on the surface of
Speaker 3: the Earth. And you can even make a diamond ocean
Speaker 3: deep inside Neptune and Uranus. It's been hypothesized that the
Speaker 3: carbon in things like carbon dioxide and methane ends up
Speaker 3: in the diamond phase deep inside, but then it melts,
Speaker 3: so you actually get a liquid diamond ocean. Diamond actually
Speaker 3: has this really cool property that water on the surface
Speaker 3: of the Earth also has, and that's right near that
Speaker 3: freezing point. The solid phase is slightly less dense than
Speaker 3: the liquid phase, which is why we have, for example,
Speaker 3: icebergs that can float on water. Here. The same is
Speaker 3: true deep inside Uranus and Neptune. Diamond bergs would actually
Speaker 3: float on a diamond seed deep inside Uranus and Neptune.
Speaker 3: So these are just material behavior that we just have
Speaker 3: no experience with here on the surface of the Earth,
Speaker 3: and I love thinking about it.
Speaker 2: Yeah, simultaneously wonderful and frustrating that it violates our intuition,
Speaker 2: so you can't really picture it. You want to be
Speaker 2: able to, but you can't with the idea of superheated
Speaker 2: ices and things like that. But it reminds me of
Speaker 2: actually things closer to home. You talk about other ways
Speaker 2: that even the interior of the Earth also violates our
Speaker 2: intuitions about how materials work. For example, I think there's
Speaker 2: a part in the book where you talk about how
Speaker 2: it's hard for people to understand sometimes that parts of
Speaker 2: the mantle migrate up and down even though the mantle
Speaker 2: is solid not liquid. Is that right?
Speaker 3: That's absolutely right. So I think there's also a big
Speaker 3: misunderstanding out there that you think because you see at volcanos,
Speaker 3: you see this magma coming up being all liquid, you
Speaker 3: think that means that the interior of the earth, the mantle,
Speaker 3: is all liquid, And that's absolutely not true. The rock
Speaker 3: inside the mantle of the Earth is solid, it's very solid.
Speaker 3: That doesn't mean it can't flow. So we do see
Speaker 3: that rock move around, it moves on really slow timescales,
Speaker 3: so it can take hundreds of millions of years for
Speaker 3: a rock to make it from say the core mantle boundary,
Speaker 3: up to the surface of the Earth. But it does flow,
Speaker 3: it does move around, and the only reason we see
Speaker 3: it in its liquid state at the surface is because
Speaker 3: it was under a lot of pressure deep inside the Earth.
Speaker 3: Pressures increase incredibly as you go down, and so that
Speaker 3: it was basically pressure frozen. It was basically made a
Speaker 3: solid because of the high pressure, and then you bring
Speaker 3: that up to the surface and you release the pressure
Speaker 3: and everything kind of expands out and becomes the magma
Speaker 3: the liquid that you see.
Speaker 2: There is a strange feature Towards the end of your book.
Speaker 2: There's a great section where you just sort of like
Speaker 2: explore all of the different strange aspects of planets, especially
Speaker 2: like the ice giants and the gas giants. So you
Speaker 2: talk about the helium ray and the diamond rain. You
Speaker 2: also talk about why Uranus and Neptune have strange multi
Speaker 2: polar magnetic fields. Does does that mean? Where does that
Speaker 2: come from?
Speaker 3: Imagine back to when we only really knew about the
Speaker 3: Earth's magnetic field, right, and Earth's magnetic field the most
Speaker 3: common feature about it is it looks like a die pole.
Speaker 3: So there's a north pole and there's a south pole,
Speaker 3: and the magnetic field lines connect them. When we started
Speaker 3: exploring other planetary bodies, we started to see this happen
Speaker 3: a lot. So Jupiter and Saturn also very dipolar. Mercury dipolar.
Speaker 3: When the Voyager two mission, which was the only mission
Speaker 3: that we have that has gone out to Uranus and
Speaker 3: Neptune and basically just flew by for a little while,
Speaker 3: when it got to first Urinus, which is closer, it
Speaker 3: didn't see a dipolar field. It saw this multipolar fields.
Speaker 3: There were a bunch of North poles and a bunch
Speaker 3: of South poles all over the planet. I remember reading
Speaker 3: about some of this history of when this happened in
Speaker 3: the eighties, and people, you know, weren't expecting that. So
Speaker 3: the first question you have is, all, well, maybe maybe
Speaker 3: something broke, maybe the magnetometer is not working properly or
Speaker 3: something like that, and they did lots of tests and
Speaker 3: they make sure that wasn't the case. Then you get
Speaker 3: out to Neptune and it's also this multipolar field, and
Speaker 3: so you got to say, hmm, well, were we just
Speaker 3: wrong about the fact that magnetic fields are supposed to
Speaker 3: be dipolar, and the fact that Uranus and Neptune happen
Speaker 3: to be the only water rich planets in the Solar System,
Speaker 3: these ice giants, and they happen to be the only
Speaker 3: ones with multipolar fields, then you got to start saying,
Speaker 3: maybe there's a causal relationship with there, right, So I've
Speaker 3: spent a lot of time thinking about that and trying
Speaker 3: to think about how you create multipolar fields in an
Speaker 3: ice giant, And it turns out that there are some
Speaker 3: features in an ice giant that might make multipolar fields
Speaker 3: more likely to occur. Turns out that the dynamo region
Speaker 3: can be really thin in these bodies, so you just
Speaker 3: have this really thin shell where the conditions are just
Speaker 3: right for convection to occur in a good electrical conductor
Speaker 3: and create a magnetic field. When you have this really
Speaker 3: thin shell, you can't make big global dipolar fields. Nothing's
Speaker 3: communicating the right way. All the length skills are too small.
Speaker 3: So maybe you get more multipolar fields that way. People
Speaker 3: are still studying this that we're really looking forward to
Speaker 3: new mission, hopefully to Uranus sometime in the next decade,
Speaker 3: so that we can study the magnetic field up close
Speaker 3: and the interior of the planet, so that we can
Speaker 3: understand the connection.
Speaker 2: We have a basic idea of the types of planets
Speaker 2: that can exist from our own Solar system. We have,
Speaker 2: you know, the inner rocky planets. We have the gas giants,
Speaker 2: we have the ice giants, and then we have these
Speaker 2: other planets that we're familiar with from looking at other stars,
Speaker 2: like the hot Jupiters and the super earths and so forth.
Speaker 2: But there is a new planet type that you introduced
Speaker 2: me to in this book. I don't think i'd ever
Speaker 2: heard of it before, the hypothetical carbon planet. That sounds
Speaker 2: so strange. What is the deal with this?
Speaker 3: Yeah, you know, it's interesting when you look in our
Speaker 3: Solar system, and let's say you look at the rocks
Speaker 3: inside the Earth. They're mostly made of what we call silicates,
Speaker 3: so they have silicon and oxygen atoms combined together, magnesium silicates,
Speaker 3: aluminum silicates. This is kind of what defines the chemistry
Speaker 3: of the rocks on the Earth, and all of that
Speaker 3: was determined by the ratio of carbon to oxygen to
Speaker 3: magnesium in the protoplanetary disk that formed and eventually became
Speaker 3: all the materials we have. Now, if you go to
Speaker 3: some other solar systems out there, they might have slightly
Speaker 3: different ratios. And if nebula out there that eventually forms
Speaker 3: a star with planets around it happened to have a
Speaker 3: little bit more carbon, then the types of rocks that
Speaker 3: you form, the types of minerals that you form, can
Speaker 3: be very different, and you can actually create planets that
Speaker 3: are mostly made of carbon, that have a much higher
Speaker 3: carbon content than what we have here on Earth. It's
Speaker 3: a geologist kind of like dreamscape to think about, what
Speaker 3: if the chemistry was just slightly different because there's just
Speaker 3: a little bit more of some tiny sub element. Right, Remember,
Speaker 3: our solar system was mostly hydrogen and helium, and it
Speaker 3: was just little bits of these rocks that eventually became
Speaker 3: the Earth. And now you just slightly tweak the ratio
Speaker 3: of those elements in extrasolar planets and you could create
Speaker 3: completely different worlds.
Speaker 2: Last question. You already mentioned why the upcoming study of
Speaker 2: asteroid sixteen Psyche is going to be so exciting, but
Speaker 2: what are some of the other upcoming missions and experiments
Speaker 2: that you think are likely to teach us the most
Speaker 2: about planetary science. What are you most excited to learn
Speaker 2: in the near future.
Speaker 3: Okay, there are two missions that I'm most excited about,
Speaker 3: and I actually have nothing to do with these missions,
Speaker 3: so I'm just a super fan of these missions. The
Speaker 3: first one is the Europa Clipper mission, which is going
Speaker 3: to go to a moon of Jupiter named Europa, scheduled
Speaker 3: launch next year. And Europa is an exciting place because
Speaker 3: it's this icy moon of Jupiter and we know that
Speaker 3: it has a liquid water ocean buried beneath the surface,
Speaker 3: and we think it has all the ingredients you might
Speaker 3: think of as necessary for life. So the plan is
Speaker 3: to go there and see try to get a sense
Speaker 3: of what that ocean is made of. Are there complex
Speaker 3: molecules in there that are kind of what we would
Speaker 3: consider the building blocks of life, things like that. So
Speaker 3: that's one really exciting. The other one is actually another moon.
Speaker 3: There's a mission called Drag and Fly, which is scheduled. Yeah,
Speaker 3: you know it's going to be a good mission when
Speaker 3: it has a cool name, right, So Dragonfly is scheduled
Speaker 3: to go to Saturn's moon Titan. Now Titan, in my opinion,
Speaker 3: is probably one of the coolest places in the Solar
Speaker 3: System to think about. It's the only other planetary body
Speaker 3: out there to have nitrogen as its main based thick atmosphere.
Speaker 3: So the Earth is the other planet, right, so it
Speaker 3: has some similarities to it. It's the only other body
Speaker 3: out there that we have seen liquids running on the surface.
Speaker 3: So just like on Earth we have rivers and seas
Speaker 3: and oceans, Titan has rivers and seas and oceans on
Speaker 3: the surface. Now there's a catch, they're not water. Those
Speaker 3: rivers and season oceans are actually made of things like
Speaker 3: methane and ethane, so not you know, fun places. But
Speaker 3: Titan has this thick atmosphere and it's also incredibly small,
Speaker 3: so it has a really low gravity. So my favorite
Speaker 3: fact about Titan is that it's really easy to fly there.
Speaker 3: So you could strap some cardboard on your arms and
Speaker 3: flap them on the surface of Titan could fly right.
Speaker 3: So this is amazing. So the Dragonfly mission has decided
Speaker 3: to take advantage of it. So it's sending essentially an octacopper,
Speaker 3: so it's two quad copters, so think of a helicopter,
Speaker 3: but with eight different blade things. It's sending this thing
Speaker 3: out there. It's going to be able to land on
Speaker 3: the surface, do a bunch of science and then take
Speaker 3: off again, look around, figure out where it wants to
Speaker 3: go next, travel quite long distances, and then land again
Speaker 3: and do more science. So this is going to be
Speaker 3: the first time we're able to study this world very locally, right,
Speaker 3: like touch it, and also fly around to very different
Speaker 3: parts of it. And Titans exciting because it has all
Speaker 3: the building blocks of life. We know there's a liquid
Speaker 3: water ocean underneath. We know it has complex chemicals, those
Speaker 3: hydrocarbons like methane and ethane. We know it has energy sources.
Speaker 3: So we really want to understand a lot of the
Speaker 3: processes that we think are important in the creation of
Speaker 3: life are going to be happening on Titan, and we're
Speaker 3: excited to study them up close.
Speaker 2: Doctor Sabine Stanley, thank you so much for joining us today.
Speaker 2: It's been a real pleasure to talk.
Speaker 3: Thanks so much.
Speaker 2: This was fun, all right. If you would like to
Speaker 2: check out the book for yourself again, it is called
Speaker 2: What's Hidden Inside Planets from twenty twenty three, available in
Speaker 2: audiobook form as well if that's your medium of choice.
Speaker 2: Quick note about our show if you are new to it.
Speaker 2: Stuff to Blow your Mind is a science and culture
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