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Speaker 1: Hey, Jorgey, I have a food engineering question for you.

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Speaker 1: Food engineering. We're trying to melt ice cream with a

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Speaker 1: particle collider, not yet, but now I'm gonna go try that.

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Speaker 1: Now I'm wondering how they engineer foods with a liquid

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Speaker 1: center inside. Okay, now you're trying to make our candy

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Speaker 1: with liquid inside? Yeah? Or like, how do they make

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Speaker 1: peanut butter vealed pretzels? That's a billion dollars secret. I

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Speaker 1: can't just reveal it. We might get sued. Alright, I

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Speaker 1: guess we should stick to revealing big science secrets. Yeah.

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Speaker 1: I don't think we'll get sued for those. They're usually

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Speaker 1: free and maybe also useless. You said it not mean. Hi.

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Speaker 1: I am more Hammon cartoonists and the creator of PhD comics. Hi.

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Speaker 1: I'm Daniel. I'm a particle physicist, and I do enjoy

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Speaker 1: me a peanut butter field pretzel. Really, why can't you

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Speaker 1: just put the peanut butter on the outside. It's a

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Speaker 1: totally different taste experience, man, I mean this can't be compared. Plus,

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Speaker 1: I admire the engineering. Somehow they baked this pretzel around

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Speaker 1: the peanut butter. It's incredible. You think that's how they

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Speaker 1: do it. They formed the bread around the peanut butter.

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Speaker 1: Actually did some research about this. It was the basis

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Speaker 1: of a big lawsuit. And there's a fancy co extrusion

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Speaker 1: process where they have the pretzel dough around the peanut

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Speaker 1: butter and then they bake it. Co extrusion. Wow, that

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Speaker 1: sounds like a heavy duty physics term. You should google it.

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Speaker 1: They used to find some really fun YouTube videos about

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Speaker 1: the interior of these factories. Pretty fascinating food engineering. And

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Speaker 1: by experiments, you mean you tried it at home a

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Speaker 1: bunch of times, or you ate a bunch of pretzels

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Speaker 1: with peanut butter. I ate a bunch of pretzels. I

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Speaker 1: tried the chocolate covered versions, the non chocolate cover versions.

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Speaker 1: I'm in the name of science. Have you tried coach

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Speaker 1: twinging butter and pretzels? That's the next level heart attack recipe.

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Speaker 1: You should sell that idea to Ben and Jerry's. But anyways,

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Speaker 1: welcome to our podcast, Daniel and Jorge Explain the Universe,

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Speaker 1: a production of I Heart Radio in which we extrude

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Speaker 1: ideas about the universe into your head without breaking your skull. Somehow,

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Speaker 1: we wrap your mind around the peanut butter field delicious

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Speaker 1: secrets of the universe. We talk about all of the

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Speaker 1: crazy stuff happening deep out in crazy space, and all

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Speaker 1: the tiny stuff happening in between your toes and the

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Speaker 1: smallest particles. We break down quantum mechanics, We talk about

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Speaker 1: astrophysics and everything in between. Wait, I thought that the

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Speaker 1: science secrets that we reveal our the pretzel part that

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Speaker 1: surrounds the yummy peanut butter inside of our punts. It

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Speaker 1: could be I was thinking of my brain is the

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Speaker 1: peanut butter and my skull is the pretzel. You just

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Speaker 1: ruined that vision of deliciousness for me. Every time you

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Speaker 1: bite into one of those from now on, just think

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Speaker 1: I'm eating Daniel's head, not mom goodness, let's please hitit

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Speaker 1: that out. But anyways, we do like to talk about

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Speaker 1: the universe and all of it's amazing goodness inside and

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Speaker 1: everything that you can quote through it, inside of it,

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Speaker 1: and all the things that you can discover because it's

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Speaker 1: the big cosmos and there are wonderful things out there

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Speaker 1: hiding in plain sight, that's right. And the more we

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Speaker 1: look out into the universe, the more we discover these

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Speaker 1: surprises and the more questions we have about exactly how

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Speaker 1: things work, what layers they're in, and how they're organized

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Speaker 1: and how they got that way, right, because we can

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Speaker 1: see the universe and touch it and probe, but who

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Speaker 1: knows what's line underneath the surface, what is at the

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Speaker 1: core of the universe and how it works. And everything

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Speaker 1: that's out there has a history. The Moon, the Earth, Mars,

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Speaker 1: every planet, every star has a sometimes billion years long history,

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Speaker 1: a crazy story that tells us how it got to

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Speaker 1: be the way it is today. And unraveling that story

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Speaker 1: is like the biggest, most delicious detective mystery in the universe.

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Speaker 1: Figuring out what exactly happened to the object. Can we

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Speaker 1: tell just by looking on the outside or just by

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Speaker 1: looking through a telescope, exactly what the story is of

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Speaker 1: this heavenly body? Yeah, because we want to know, right,

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Speaker 1: the species as human beings, were curious about where things

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Speaker 1: came from and how they got to be the way

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Speaker 1: they got to be, and that's all part of their history,

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Speaker 1: and it's all they're inside of the things for looking at. Yeah,

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Speaker 1: we showed up in this universe basically the last minute,

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Speaker 1: and a lot of stuff happened before we got here.

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Speaker 1: So it's fun to unravel those stories and figure out

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Speaker 1: have things looked this way for a long time? The

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Speaker 1: things used to be really different. Does that mean things

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Speaker 1: are going to change? It's all just part of like

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Speaker 1: becoming conscious beings and exploring the world that we find

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Speaker 1: around us. So today we'll be talking about one of

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Speaker 1: these mysteries. Line underneath the surface of our own neighborhood.

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Speaker 1: It's something that we can see almost every night, but

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Speaker 1: that is kind of hidden from us, right, that's right.

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Speaker 1: We have questions about what's beneath our feet, and we

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Speaker 1: have questions about what's beneath the feet of potential neighbors.

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Speaker 1: You mean the actual neighbors. Like is your neighbor sitting

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Speaker 1: on top of a giant oil well or something? Yeah,

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Speaker 1: maybe there's like a huge peanut butter deposit under my

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Speaker 1: neighbor's house and I could sell that to that factory. Yeah,

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Speaker 1: instead of liquid gold, that's liquid saturated fats. Well, it's

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Speaker 1: peanut butter technically a liquid or is it a solid?

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Speaker 1: I guess it depends if it's smooth or what's the

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Speaker 1: other one crunching? What is the phase diagram of peanut butter?

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Speaker 1: Can it sublimate into a gas? I wonder. I don't

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Speaker 1: know if anybody's ever done that experiment. You mean, like

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Speaker 1: go straight into a gas form of peanut butter, like

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Speaker 1: you can invade peanut butter. Not recommended, folks, not recommended.

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Speaker 1: Our lawyers have not vetted that statement. Please do not

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Speaker 1: vape peanut butter. You could clog through your lungs directly

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Speaker 1: with peanut butter. But if you do vape peanut butter,

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Speaker 1: tell us about it, because we're curious that may will

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Speaker 1: be another billion dollar industry who knows, or a billion

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Speaker 1: dollar lawsuit. We're about to get hit with people who

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Speaker 1: use it to cure their pretzel addiction, and then they'll

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Speaker 1: need some patches, some peanut butter patches. Anyways, Yeah, we'll

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Speaker 1: be tackling one such mystry in our own solar system,

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Speaker 1: so to be on the podcast, we'll be asking the question,

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Speaker 1: does Mars have a solid or liquid core? I guess

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Speaker 1: the question is Mars hardcore or softcore? Is it a

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Speaker 1: hard boiled egg or a soft boiled egg? Exactly? I

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Speaker 1: think it's a super fascinating question, and it's fun for

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Speaker 1: me because I think about like when people were asking

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Speaker 1: this question about the Earth, you know, for a long time,

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Speaker 1: we didn't really know, like, hey, what's the Earth made

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Speaker 1: out of? It's just one big rock? Or is there

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Speaker 1: something crazy going on under our own feet? And now

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Speaker 1: that we have a little bit of a sense of

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Speaker 1: what's going on inside the Earth, we can ask similar

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Speaker 1: questions about other planets, and so it's fascinating to wonder, like,

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Speaker 1: are they different, are they the same? What's going on?

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Speaker 1: I guess just to verify, the Earth has a softcore. Right,

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Speaker 1: The inside of our planet is molten, right, It's like

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Speaker 1: melted rock. Yeah, there's some melted rock and a lot

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Speaker 1: of melted metal, melted iron, liquid nickel, all this kind

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Speaker 1: of stuff flowing underneath our feet. It's part of why

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Speaker 1: we have, for example, a magnetic field. I see now,

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Speaker 1: I guess, is it possible for a planet of our

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Speaker 1: size to have a solid core? Like, wouldn't all that pressure,

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Speaker 1: gravity pressure eventually kind of I don't know, melt the

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Speaker 1: stuff inside. Yeah. The reason that we do have a

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Speaker 1: liquid core is because of all that temperature and pressure,

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Speaker 1: and that comes from both the gravitational pressure and also

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Speaker 1: the decay of the isotopes inside the Earth that helped

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Speaker 1: keep it hot. But it's not going to be that

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Speaker 1: way forever. You know, we got a certain spoonful of Earth,

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Speaker 1: and eventually it's gonna cool off. I think we estimated

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Speaker 1: once on this podcast that it's going to take more

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Speaker 1: than a hundred billion years before the Earth cools, So

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Speaker 1: we got some time, and you know, the Sun is

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Speaker 1: going to go red super giant before that, so it's

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Speaker 1: not going to be our number one problem. But other

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Speaker 1: planets are different sizes and so they will have different

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Speaker 1: cooling off times. It's gonna be a while before we're cool.

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Speaker 1: I can relate to that. Hey, we're gonna be young

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Speaker 1: and hot for a long time. Think about it that way.

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Speaker 1: That sounds very hard corn, all right, But they were

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Speaker 1: asking questions about Mars. Does Mars have a solid or

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Speaker 1: liquid core? And it's kind of a big deal, right

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Speaker 1: because it might tell us whether or not Mars is

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Speaker 1: still you know, sort of young and active, and it

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Speaker 1: might tell us also what our future might be for

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Speaker 1: that's right. And I think it's just a question that

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Speaker 1: people have when they look up into the sky and

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Speaker 1: they wonder, you know, is that planet over there a

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Speaker 1: lot like our planet or is it totally different? And

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Speaker 1: what does that mean about the nature of planets and

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Speaker 1: planets in other solar systems, and it's to me just

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Speaker 1: really connects with this basic, simple initial curiosity we have

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Speaker 1: when we look up at the sky, we wonder what

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Speaker 1: those things are like. Hey, but before we answer this question,

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Speaker 1: we wanted to answer a question from one of our listeners,

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Speaker 1: perhaps our youngest listener. That's right. You may remember last

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Speaker 1: week we talked about Hannah, who was home sick from school.

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Speaker 1: She's two and a half years old. She lives in

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Speaker 1: Australia and she wanted to hear Daniel and Jorge. So

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Speaker 1: I reached out to her dad and asked him, Hey,

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Speaker 1: does Hannah have any questions she wants us to answer

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Speaker 1: while she's homesick? And he asked her what questions she

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Speaker 1: had for day own Jorge, and she said, monkey, wait? Monkey?

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Speaker 1: Is her question? Was her first question or answer to

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Speaker 1: the universe and everything in it? I don't know. It's

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Speaker 1: hard to get in the mind of a two and

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Speaker 1: a half year old sometimes. But then he asked her again,

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Speaker 1: and so here's Hannah's real question. How and how my

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Speaker 1: land home? Why is the Larne shine? Oh that's adorable.

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Speaker 1: It's like a little tiny little nerd. Yeah, and she

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Speaker 1: has the same curiosity. Today we're talking about Mars and

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Speaker 1: what's in it, But you know, she's looking up in

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Speaker 1: the sky and she's wondering, why is that thing up

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Speaker 1: there glowing at me? It has the same root of curiosity.

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Speaker 1: I see you're saying that it taps into that same

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Speaker 1: like looking up at the sky and wondering what's going

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Speaker 1: on out there? Yeah, exactly why is that thing up

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Speaker 1: there doing that thing that it's doing? Well? Really quickly?

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Speaker 1: Then what is the answer for Hannah? Why does the

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Speaker 1: moon shine? Yeah, Hannah, the reason the moon shines, especially

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Speaker 1: at night, is that it's actually reflecting light from the Sun.

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Speaker 1: Even though you can't see the sun at night, the

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Speaker 1: sun can see the moon, and so the Sun's light

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Speaker 1: bounces off the moon and down to your eyeball. So

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Speaker 1: at night you're kind of seeing the sun by seeing

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Speaker 1: it reflect off the moon. So moonlight is all just

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Speaker 1: reflected sunlight. Right. Do you think she's asking about moonshine

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Speaker 1: as well? Why does my dad drink so much moonshine?

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Speaker 1: I don't know. I think that's a question for her

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Speaker 1: dad and his father. There nothing wrong with moonshine, nothing

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Speaker 1: wrong with the little moonshine. All right, well, Hannah, that's

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Speaker 1: to your answer. The moon shines because it bounces light

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Speaker 1: from the sun, so it looks like it glows, but

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Speaker 1: really it's just kind of like a mirror, just reflecting

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Speaker 1: and getting lit up by the sun. That's right, all right,

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Speaker 1: Well back to our question, those marks have a solid

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Speaker 1: or liquid core? This is a pretty interesting question, and

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Speaker 1: we were wondering, as usual, if people out there and

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Speaker 1: new the answer to this billion year question. So thanks

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Speaker 1: to everybody who volunteered to answer this question as usual.

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Speaker 1: If you'd like to participate for future episodes, please write

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Speaker 1: to me two questions at Daniel and Jorge dot com.

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Speaker 1: Think about it first. Second, do you think Mars is

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Speaker 1: solid or liquid on the inside. Here's what people had

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Speaker 1: to say. Yes, they might be a big diamond inside it.

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Speaker 1: Now I think Mars has hot liquid. Yes, it does

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Speaker 1: completely solid, because Mars doesn't have any radioactive isotopes inside

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Speaker 1: the core. Keep it hot and keep it liquid. I'm

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Speaker 1: going to say, yes, Mars has a solid core of

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Speaker 1: iron or nickel or some other heavy element, just like Earth. Yes,

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Speaker 1: Mars has a solid core. It has no obvious plate

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Speaker 1: tectonics going on it obviously had some sort of tectonic

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Speaker 1: activity going on at some time, and the magnetic field

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Speaker 1: is almost non existent. So I think if we were

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Speaker 1: to dig deeper, I think we'd find it does have

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Speaker 1: a solid core. I don't think Mars has a significant

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Speaker 1: magnetic field because solar radiation is a concern for explorers.

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Speaker 1: I would say it cooled down at least a billion

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Speaker 1: years ago to a solid all the way through to

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Speaker 1: its core. Yes, I think it has and used to

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Speaker 1: be more powerful and active. But judging by the strength

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Speaker 1: of the magnetic field and the atmosphere, it weakened in time.

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Speaker 1: Probably that will happen to Earth to I don't know

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Speaker 1: for sure, but kind of this is the way I

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Speaker 1: think it would go. Mars does have a solid core.

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Speaker 1: End of story. I see you remember you saying in

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Speaker 1: an earlier podcast that Mars does not have um an

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Speaker 1: electromagnetic field protecting it because it doesn't have a solid core.

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Speaker 1: So I'm going to say no, all right, some pretty

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Speaker 1: definitive answers here. I feel like people were pretty confident

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Speaker 1: about their answers here. They're like, yes, definitely, this, definitely,

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Speaker 1: that definitely peanut butter, A big hot diamond. I like

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Speaker 1: that one. Why do you think people are so confident

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Speaker 1: this time? I think that a lot of people have

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Speaker 1: heard that Mars is smaller and cooled faster, doesn't have

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Speaker 1: volcanoes on the surface or a magnetic field, and so

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Speaker 1: I think that leads people to suspect that it might

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Speaker 1: just be a big lump of hard rock, unlike the

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Speaker 1: Earth and the story. All right, thanks for joining us, um,

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Speaker 1: But there's more, I see, there's more to the story.

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Speaker 1: There is more to the story, Yes, exactly. I think

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Speaker 1: there's some really interesting nuances here that these listeners will learn.

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Speaker 1: All right, well, let's dig into it. First of all, Daniel,

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Speaker 1: why is this question interesting to you, I guess and

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Speaker 1: to physicists and generally to the public. Why should we

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Speaker 1: care whether Mars is hardcore or soft and squishy on

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Speaker 1: the inside. Yeah, Well, for me, there's sort of two

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Speaker 1: levels there. One is just inherent curiosity, like I have questions,

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Speaker 1: is about what's inside stuff. You know, you ever get

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Speaker 1: a rock and you crack it open, you find a

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Speaker 1: crystal inside. There's like a joy there discovering something you

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Speaker 1: didn't expect, and so you always want to like look

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Speaker 1: inside stuff to see what's there. Maybe there's something hidden,

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Speaker 1: maybe there's a mystery. You know, that's why we explore

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Speaker 1: the universe. We don't just sit back and think about

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Speaker 1: it in our minds the way the Greeks do. So

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Speaker 1: we sort of want to know what's out there because

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Speaker 1: we could be shocked, we could be surprised. Mars couldn't

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Speaker 1: be like hollow on the inside and filled with aliens

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Speaker 1: or something. So we definitely want to go look and

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Speaker 1: see what's inside this stuff. But also I think there's

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Speaker 1: a question about just sort of the nature of planets,

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Speaker 1: Like we have an interest in how many planets are

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Speaker 1: out there, how do they form, what do they look like?

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Speaker 1: Are their potential homes for humanity out there? And to

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Speaker 1: get an answers to that, we really need to know

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Speaker 1: like how planets warm and what they're made out of

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Speaker 1: it that will give us an answer to like what

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Speaker 1: they're like on the surface. So we got to know

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Speaker 1: how the insides work if we want to figure out

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Speaker 1: how the outsides look. Yeah, because you know, it's still

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Speaker 1: kind of a big mystery in astrophysics and in science

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Speaker 1: is how do the Solar System form and out of

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Speaker 1: these planets specifically form in in an early version of

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Speaker 1: the solar system, right, and it's still kind of a

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Speaker 1: big question. We're still running simulations and trying to figure

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Speaker 1: that out. Yeah, we talked about on this podcast we

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Speaker 1: don't even really understand how our solar system came to be,

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Speaker 1: Like we run models about our solar system doesn't really

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Speaker 1: quite make sense, Like why is Mars so small? And

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Speaker 1: why do we have very few planets close to our

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Speaker 1: Sun whereas many other solar systems have lots and lots

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Speaker 1: of planets in between the distance between our Sun and Mercury.

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Speaker 1: So we want to know the answer to that question,

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Speaker 1: like what is the story of our solar system? For me,

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Speaker 1: it drives me crazy to think that there's an exciting,

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Speaker 1: traumatic story something that happened here and we just don't

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Speaker 1: know it. Maybe were coextruded by the great planet factoring

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Speaker 1: the sky, a new creation myth folks born here today

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Speaker 1: on the podcast, co extrusion sounds like a good novel name. Yeah,

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Speaker 1: And you know, there are folks who do that kind

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Speaker 1: of study, like look for other planets and other solar systems.

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Speaker 1: They look for exoplanets, and then there's a whole community

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Speaker 1: people who just study like the planets in our solar

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Speaker 1: system and what's in them. People who dedicate their entire

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Speaker 1: research careers to like this question what's inside Mars, And

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Speaker 1: you're saying that there might be parallels but the Earth

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Speaker 1: as well, Like knowing what happened to Mars might help

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Speaker 1: us understand what's happening here in Earth and let us

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Speaker 1: study things like earthquakes and what we can expect in

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Speaker 1: the future. Absolutely, you never want to just have any

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Speaker 1: equals one, right. You don't want to base all of

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Speaker 1: your conclusions about how planets work from one example. You

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Speaker 1: want to look at a bunch of them. You want

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Speaker 1: to population so you can get a sense for what's typical,

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Speaker 1: and you can also see the future, Like if Mars

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Speaker 1: is smaller and colder than Earth, then in some sense

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Speaker 1: it might be what the future of Earth looks like,

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Speaker 1: you know, in millions and billions of years. But it'd

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Speaker 1: be good to get an understanding of how these processes

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Speaker 1: work because we rely on the Earth to have these

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Speaker 1: layers in order to have our civilization and our society function.

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Speaker 1: So it would be good to know, like the factors

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Speaker 1: that control that, What are the forces at play? Are

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Speaker 1: things rising or sinking or cooling or eating or what's

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Speaker 1: going on inside. So absolutely we want to get a

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Speaker 1: better handle on the interior mechanisms of our planet. And

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Speaker 1: it's all right there, hidden under the surface, bubbling up

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Speaker 1: or maybe just chilling out. Let's get into whether or

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Speaker 1: not Mars has a solid or liquid core and whether

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Speaker 1: we'll ever know. But first let's take a quick we're

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Speaker 1: talking about whether Mars the planet, right, not the Mars bars,

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Speaker 1: because we know those have a newgat center, right, But

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Speaker 1: isnt a liquid or a solid? Oh no, another you

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Speaker 1: have a whole episode on strange matter from in candies.

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Speaker 1: Daniel vapes various candies. That's in my new podcast series,

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Speaker 1: one episode long. You just blew my mind vaping. What

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Speaker 1: does that even mean? Oh my goodness, how could it

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Speaker 1: be possible that nobody's ever tried that before, you know,

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Speaker 1: after raping other stuff, since somebody must have had that idea.

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Speaker 1: Oh man, I think you're in the run business, Daniel. Alright,

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Speaker 1: So we're trying to figure out whether Mars has a

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Speaker 1: solid or liquid core, not just for curiosity about what's

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Speaker 1: going on there, but I might tell about the history

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Speaker 1: of our planet and the whole Solar System. And so Daniel,

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Speaker 1: you actually went out there and talked to an expert

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Speaker 1: on this topic. Right, that's right. I called up a

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Speaker 1: colleague of mine, Katherine Johnson. She's at the University of

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Speaker 1: British Columbia, and I asked her why she was so

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Speaker 1: excited about this particular question. Here's what she had to say.

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Speaker 1: So then it's my pleasure to introduce to the program

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Speaker 1: professor Katherine Johnson. Catherine said hello to our listeners and

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Speaker 1: tell them a little bit about yourself. Hi. So it's

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Speaker 1: pressure to be here. And I'm a faculty member at

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Speaker 1: the University of British Columbia in Vancouver and also a

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Speaker 1: scientist at the Planetary Science Institute a Tucson and I

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Speaker 1: work in geophysics in uh sort of planetary science. So

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Speaker 1: I'm interested in understanding the interior state and evolution of

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Speaker 1: of the planets, moons, and asteroids in our Solar system.

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Speaker 1: And tell me why that's exciting for you. What is

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Speaker 1: it about the interior of Mars, for example, that makes

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Speaker 1: you curious, that makes you wonder what's going on inside there?

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Speaker 1: So you know, one of the reasons that I like

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Speaker 1: to think about other planets is really to try to

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Speaker 1: understand our own planet better. I think you know, for me,

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Speaker 1: that's one of the major motivations to try to understand

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Speaker 1: planets in our own solar system, especially in the inner

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Speaker 1: Solar system right where we have Mercury, Venus, the Earth, Mars,

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Speaker 1: our own Moon, and they're all completely different from each other,

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Speaker 1: even though they started in somewhat similar at least with

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Speaker 1: the exception of the Moon, started in somewhat similar ways.

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Speaker 1: And so a lot of this really has to do

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Speaker 1: with their interiors and how they are interiors of like

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Speaker 1: shaped their histories. All right, Thank you, Katherine. And so

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Speaker 1: you went and chatted with her about this topic, Yeah,

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Speaker 1: I did. We had a really fun conversation after all

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Speaker 1: about it. Learned a lot of gory details of how

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Speaker 1: the project works and the politics of getting her instrument

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Speaker 1: up and on Mars and how that all works. It

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Speaker 1: was a lot of fun. Thanks Catherine very much for

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Speaker 1: educating me about your research. She has an instrument on Mars.

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Speaker 1: She does exactly. She helped design and build this seizedmometer

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Speaker 1: that they have on Mars, which is one of the

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Speaker 1: ways they figure out what's inside. Interesting because that is

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Speaker 1: sort of a way they do it here on Earth. Right,

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Speaker 1: we haven't actually like dug a hole or a little

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Speaker 1: people to the center of the earth. We have just

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Speaker 1: models and kind of sound and sound wave detections on

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Speaker 1: the surface, right, that's right. We have dug in only

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Speaker 1: very shallow holes relatively speaking, into the earth, and so

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Speaker 1: we have not actually probed physically the center of the Earth.

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Speaker 1: But we do have a pretty good picture of what's

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Speaker 1: going on inside the earth because of earthquakes. Every time

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Speaker 1: there's an earthquake, it's like the earth rings sort of

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Speaker 1: like a bell, and the waves they don't just like

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Speaker 1: shake the outer crust, they propagate all the way through

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Speaker 1: the interior. And when waves cross a threshold, like when

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Speaker 1: you go from solid to liquid, or the quit to solid,

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Speaker 1: or one kind of metal or to another, you get reflections.

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Speaker 1: Just like when light hits a piece of glass, most

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Speaker 1: of it goes through, but some of it reflects. So

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Speaker 1: these reflections and the interior of the earth make for

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Speaker 1: really complicated patterns. But if you have a bunch of

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Speaker 1: seized momometers all over the earth that measure the shaking,

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Speaker 1: you can get a really nice picture of exactly how

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Speaker 1: this wave propagated through the earth. And then from that

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Speaker 1: you can back out like, oh, there must have been

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Speaker 1: a layer here, and it must have been a layer there,

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Speaker 1: and you can make really detailed measurements about the composition

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Speaker 1: and the density and the flow of those layers. And

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Speaker 1: so she has some instruments on Mars, and are the

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Speaker 1: earthquakes on Mars as she is, she can measure there

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Speaker 1: are no earthquakes on Mars. There are Mars quakes, Martian quakes. Yeah,

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Speaker 1: they actually only have one sized momometer on Mars, so

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Speaker 1: it's a little trickier, but we'll dig into it in

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Speaker 1: detail in a few minutes, all right. And I like

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Speaker 1: how she talked about how every planet is different and

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Speaker 1: how like the insights tell you a lot about your history.

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Speaker 1: I guess that's true for people to write like you

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Speaker 1: can look at my veins and be like, this guy

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Speaker 1: hit a lot of peanut butter. Unfortunately, sometimes our interiors

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Speaker 1: do reveal our history exactly, and every planet has a

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Speaker 1: very different story. And the thing that always surprises me

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Speaker 1: is to realize that these stories change with time. You know,

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Speaker 1: It's not like Venus has always looking the way it

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Speaker 1: does today and that Mars has always looked the way

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Speaker 1: it does today. You know, right now, the surface of

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Speaker 1: Mars is very cool and inactive. But scientists think that

428
00:22:22,880 --> 00:22:26,200
Speaker 1: Mars had volcanoes active on its surface up to maybe

429
00:22:26,240 --> 00:22:29,520
Speaker 1: like a million years ago, which is basically no time

430
00:22:29,560 --> 00:22:32,760
Speaker 1: at all in the billions of years history of Mars.

431
00:22:32,800 --> 00:22:35,680
Speaker 1: So like, this is an active story that's still developing.

432
00:22:35,920 --> 00:22:38,760
Speaker 1: We're in the middle of history. We are history is

433
00:22:38,800 --> 00:22:41,479
Speaker 1: being made exactly all right, Well, maybe it step us

434
00:22:41,480 --> 00:22:44,240
Speaker 1: through here. Why do we think Mars might have a

435
00:22:44,400 --> 00:22:47,919
Speaker 1: solid core? Like where did this idea first come from?

436
00:22:47,960 --> 00:22:49,760
Speaker 1: And why do we need to assume that? Well, you know,

437
00:22:49,800 --> 00:22:51,640
Speaker 1: we just didn't know for a long time. I think

438
00:22:51,720 --> 00:22:54,440
Speaker 1: the popular conception is that Mars has a solid core

439
00:22:54,640 --> 00:22:58,280
Speaker 1: just because it's smaller and colder. Right, Mars is really

440
00:22:58,320 --> 00:23:00,720
Speaker 1: weird and small. People might not realized. But it has

441
00:23:00,760 --> 00:23:03,280
Speaker 1: like a tenth of the mass of the Earth, so

442
00:23:03,320 --> 00:23:06,560
Speaker 1: it's really a much smaller chunk of stuff than the

443
00:23:06,560 --> 00:23:08,720
Speaker 1: Earth is. Well, I really a ten I knew it

444
00:23:08,760 --> 00:23:11,840
Speaker 1: was smaller, but I didn't know it's ten times smaller, lighter. Yeah,

445
00:23:11,840 --> 00:23:15,240
Speaker 1: it's you know, maybe ten but it's just like not

446
00:23:15,320 --> 00:23:17,840
Speaker 1: really that much stuff. And people think that it might

447
00:23:17,880 --> 00:23:20,160
Speaker 1: be Jupiter's fault, you know, Jupiter might have come into

448
00:23:20,200 --> 00:23:23,680
Speaker 1: the inner solar system earlier on, like millions and billions

449
00:23:23,680 --> 00:23:25,760
Speaker 1: of years ago, and sort of pushed away a lot

450
00:23:25,760 --> 00:23:28,199
Speaker 1: of the stuff that might have helped make Mars bigger.

451
00:23:28,480 --> 00:23:31,080
Speaker 1: That might be one reason why Mars is small. But that's,

452
00:23:31,160 --> 00:23:33,359
Speaker 1: you know, just a mystery. But in the end, Mars

453
00:23:33,400 --> 00:23:35,440
Speaker 1: is a smaller chunk of stuff, and a smaller chunk

454
00:23:35,480 --> 00:23:38,120
Speaker 1: of stuff doesn't have as much gravity, so it doesn't

455
00:23:38,119 --> 00:23:40,920
Speaker 1: have as much pressure and high temperature stuff and its interior,

456
00:23:41,240 --> 00:23:44,199
Speaker 1: and it cools faster. So there's this sense that Mars is,

457
00:23:44,240 --> 00:23:46,879
Speaker 1: like being a smaller rock, has a less chance to

458
00:23:46,920 --> 00:23:49,399
Speaker 1: have a molten core than Earth does. Like you know,

459
00:23:49,560 --> 00:23:52,200
Speaker 1: asteroids out there don't have molten corks. They're not big

460
00:23:52,320 --> 00:23:55,680
Speaker 1: enough to generate that pressure and temperate in their interiors. Oh,

461
00:23:55,720 --> 00:23:57,960
Speaker 1: I see, So that's where I guess you might first

462
00:23:57,960 --> 00:24:01,240
Speaker 1: assume that Mars has a solid core, and we also

463
00:24:01,280 --> 00:24:04,159
Speaker 1: know just have a magnetic field, right, I mean, I

464
00:24:04,160 --> 00:24:06,800
Speaker 1: guess if I said this, like they took a compass

465
00:24:06,840 --> 00:24:08,680
Speaker 1: to Mars and it didn't work. Yeah, there's lots of

466
00:24:08,720 --> 00:24:11,680
Speaker 1: satellites orbiting Mars looking for magnetic fields and they don't

467
00:24:11,720 --> 00:24:13,280
Speaker 1: have one. But if you look at some of the

468
00:24:13,359 --> 00:24:16,439
Speaker 1: rocks on Mars, you can see fossil evidence for a

469
00:24:16,480 --> 00:24:19,359
Speaker 1: magnetic field. That means that we know that Mars used

470
00:24:19,400 --> 00:24:22,080
Speaker 1: to have a magnetic field. So that sort of adds

471
00:24:22,119 --> 00:24:24,600
Speaker 1: to the narrative, like maybe Mars when it was young

472
00:24:24,760 --> 00:24:29,360
Speaker 1: and hot, literally had a flowing interior core that generated

473
00:24:29,359 --> 00:24:32,399
Speaker 1: this magnetic field. But it's gone now, and so maybe

474
00:24:32,400 --> 00:24:35,119
Speaker 1: that like locked up and there's no longer any motion

475
00:24:35,200 --> 00:24:36,720
Speaker 1: in the core. Yeah. I used to be a lot

476
00:24:36,720 --> 00:24:40,000
Speaker 1: more magnetic when I was younger, and otter too, but no,

477
00:24:40,119 --> 00:24:42,000
Speaker 1: I'm just cool. Yeah, back when you had a better

478
00:24:42,040 --> 00:24:46,840
Speaker 1: interior flow. Yeah, back when were his clogged with candy killings?

479
00:24:47,160 --> 00:24:48,879
Speaker 1: All right, So then where did this idea that it

480
00:24:48,920 --> 00:24:51,160
Speaker 1: could be liquid? And I mean, it seems pretty reasonable

481
00:24:51,200 --> 00:24:54,240
Speaker 1: for it to be solid and likely, but what makes

482
00:24:54,280 --> 00:24:56,639
Speaker 1: this thing it could have a liquid core? Well, you know,

483
00:24:56,720 --> 00:24:58,959
Speaker 1: we just don't know, And so one question is like,

484
00:24:59,119 --> 00:25:01,480
Speaker 1: maybe we think it has a solid core, but let's

485
00:25:01,560 --> 00:25:04,800
Speaker 1: go check. Remember a lot of the amazing discoveries we've

486
00:25:04,880 --> 00:25:07,480
Speaker 1: made in history come from just sort of checking off

487
00:25:07,560 --> 00:25:10,080
Speaker 1: things where we didn't expect to find anything interesting. Like

488
00:25:10,440 --> 00:25:13,800
Speaker 1: let's check to see how quickly galaxies rotate. Oh my, gosh,

489
00:25:13,880 --> 00:25:16,920
Speaker 1: they're rotating way too fast. That's how we discovered dark matter.

490
00:25:17,240 --> 00:25:19,680
Speaker 1: Let's check to see what happens when we shoot photons

491
00:25:19,680 --> 00:25:22,159
Speaker 1: at this metal that seems boring. Oh my gosh, we

492
00:25:22,200 --> 00:25:25,399
Speaker 1: discover quantum mechanics. So there's lots of wonderful opportunities to

493
00:25:25,400 --> 00:25:28,120
Speaker 1: discover things when you just sort of do basic checks.

494
00:25:28,119 --> 00:25:30,159
Speaker 1: So that's number one. I guess you don't want to

495
00:25:30,200 --> 00:25:32,440
Speaker 1: go around the university just assuming things right. You want

496
00:25:32,440 --> 00:25:35,640
Speaker 1: to actually make sure. Yeah, that's why we do experiments right,

497
00:25:35,680 --> 00:25:38,679
Speaker 1: because often the results are a surprise, and those are

498
00:25:38,680 --> 00:25:41,240
Speaker 1: the most delicious times in science, right when you get

499
00:25:41,280 --> 00:25:44,399
Speaker 1: a result that surprises you, that doesn't make sense, it

500
00:25:44,440 --> 00:25:47,280
Speaker 1: conflicts with your idea of the universe, and that's how

501
00:25:47,320 --> 00:25:49,680
Speaker 1: you learn, right, that's what science is. But then people

502
00:25:49,720 --> 00:25:53,200
Speaker 1: also realize that we didn't actually have conclusive evidence that

503
00:25:53,560 --> 00:25:55,719
Speaker 1: Mars had a solid core, that you could build a

504
00:25:55,800 --> 00:25:58,360
Speaker 1: model of Mars with a liquid core that was still

505
00:25:58,440 --> 00:26:01,200
Speaker 1: consistent with everything we saw and we knew about Mars.

506
00:26:01,400 --> 00:26:03,640
Speaker 1: But I guess maybe the question is could it be liquid?

507
00:26:03,680 --> 00:26:06,400
Speaker 1: I mean, if it doesn't have a magnetic field, wouldn't that,

508
00:26:06,600 --> 00:26:08,400
Speaker 1: you know, tell us that it has a solid core,

509
00:26:08,760 --> 00:26:13,119
Speaker 1: not necessarily, because the magnetic field actually requires two different things.

510
00:26:13,160 --> 00:26:16,760
Speaker 1: It requires some liquid, but it also requires flow, Like

511
00:26:16,800 --> 00:26:19,000
Speaker 1: that liquid has to be in motion. There needs to

512
00:26:19,000 --> 00:26:22,040
Speaker 1: be some sort of like circulation of that liquid. Because

513
00:26:22,040 --> 00:26:24,600
Speaker 1: remember the dynamo effect that gives you a magnetic field

514
00:26:24,880 --> 00:26:27,760
Speaker 1: doesn't just come from having liquid sitting around. It comes

515
00:26:27,760 --> 00:26:31,920
Speaker 1: from currents right ionized particles in motion. So it's possible

516
00:26:32,000 --> 00:26:34,560
Speaker 1: that Mars has a liquid, but that liquid isn't flowing

517
00:26:34,600 --> 00:26:37,480
Speaker 1: in the right way to give you a magnetic field. Oh,

518
00:26:37,560 --> 00:26:40,159
Speaker 1: I see. It could just be like liquid center just

519
00:26:40,200 --> 00:26:42,320
Speaker 1: sitting there. Yeah. Or you could have a liquid layer

520
00:26:42,359 --> 00:26:45,000
Speaker 1: between two other solid layers and it could just be

521
00:26:45,040 --> 00:26:47,360
Speaker 1: sort of like too thin to have the right kind

522
00:26:47,400 --> 00:26:50,119
Speaker 1: of rotating currents. Or it might just be the like

523
00:26:50,359 --> 00:26:53,520
Speaker 1: the heat difference between that liquid layer and the next

524
00:26:53,560 --> 00:26:55,919
Speaker 1: layer isn't great enough to get like the convection. You

525
00:26:56,000 --> 00:26:58,280
Speaker 1: need to have flow, don't. You also need like to

526
00:26:58,359 --> 00:27:01,199
Speaker 1: have special metals in that you know, liquid layer for

527
00:27:01,240 --> 00:27:03,640
Speaker 1: you to get the magnetic field, Like is an iron

528
00:27:04,359 --> 00:27:06,639
Speaker 1: in our molten core a big part of why we

529
00:27:06,680 --> 00:27:08,879
Speaker 1: have a magnetic field, yeah, exactly, And so you need

530
00:27:08,920 --> 00:27:11,480
Speaker 1: to be open to those possibilities. We do think, based

531
00:27:11,520 --> 00:27:14,520
Speaker 1: on density estimates, that there is a big iron nickel

532
00:27:14,560 --> 00:27:17,000
Speaker 1: core to Mars. So the question is really is some

533
00:27:17,040 --> 00:27:19,239
Speaker 1: of it liquid or is it all solid? But you're right,

534
00:27:19,240 --> 00:27:21,640
Speaker 1: you need some metal. If you had just like a

535
00:27:21,640 --> 00:27:24,399
Speaker 1: core of you know, ceramic or whatever, something that was

536
00:27:24,400 --> 00:27:27,280
Speaker 1: totally insulating, then you couldn't get a magnetic feel from

537
00:27:27,320 --> 00:27:29,520
Speaker 1: that has to conduct electricity. So it could have a

538
00:27:29,600 --> 00:27:32,760
Speaker 1: liquid core. Mars could look sort of small and cold,

539
00:27:32,880 --> 00:27:35,920
Speaker 1: but it could be inside you know, frosthing or seating

540
00:27:36,040 --> 00:27:40,360
Speaker 1: or you know, have a soft, squishy center or layer. Absolutely,

541
00:27:40,560 --> 00:27:43,000
Speaker 1: and that's a really exciting moment in science when you realize,

542
00:27:43,119 --> 00:27:45,560
Speaker 1: hold on a second, you know, everything we thought was

543
00:27:45,600 --> 00:27:50,320
Speaker 1: true could be different. This other theories actually totally consistent

544
00:27:50,359 --> 00:27:53,160
Speaker 1: with everything we know. And that's exciting because it gives

545
00:27:53,160 --> 00:27:55,639
Speaker 1: you like two possibilities to explore. It gives you an

546
00:27:55,640 --> 00:27:58,240
Speaker 1: opportunity to be surprised. Then, I guess the big question

547
00:27:58,280 --> 00:28:00,760
Speaker 1: then is if it could be liquid inside, how could

548
00:28:00,840 --> 00:28:03,040
Speaker 1: we ever know? I mean, we're sitting here, thousands and

549
00:28:03,040 --> 00:28:06,600
Speaker 1: thousands of miles away, sending small robots one at a time.

550
00:28:06,960 --> 00:28:09,800
Speaker 1: How are we going to find out what's inside? Daniel. Yeah, Well,

551
00:28:09,840 --> 00:28:11,840
Speaker 1: it turns out we have lots of different ways to

552
00:28:11,840 --> 00:28:14,280
Speaker 1: prove this question, some of which we can do without

553
00:28:14,320 --> 00:28:16,880
Speaker 1: actually going to the surface of Mars. One of them

554
00:28:16,920 --> 00:28:19,679
Speaker 1: is really cool is that they measure basically how squishy

555
00:28:19,800 --> 00:28:23,320
Speaker 1: Mars is. They have a satellite which rotates around Mars

556
00:28:23,520 --> 00:28:26,080
Speaker 1: and basically it's imaging its surface and making a picture

557
00:28:26,080 --> 00:28:28,800
Speaker 1: of like the shape of Mars, how spherical is it?

558
00:28:29,040 --> 00:28:32,520
Speaker 1: Because Mars, like everything else, is getting squeezed by the Sun.

559
00:28:32,880 --> 00:28:36,080
Speaker 1: Remember we talked about tidal forces, how the gravitational force

560
00:28:36,119 --> 00:28:38,840
Speaker 1: on an object is stronger on the side that's closer

561
00:28:38,880 --> 00:28:41,320
Speaker 1: to the Sun than further from the Sun. Or for example,

562
00:28:41,360 --> 00:28:44,760
Speaker 1: this is why Jupiter's moon Io has hot interior, because

563
00:28:44,760 --> 00:28:48,040
Speaker 1: it's getting squeezed by these tidal forces. Well, Mars is

564
00:28:48,040 --> 00:28:51,000
Speaker 1: getting squeezed by the Sun, and it would get squeezed

565
00:28:51,000 --> 00:28:54,200
Speaker 1: differently if it had a liquid center or some liquid

566
00:28:54,280 --> 00:28:57,040
Speaker 1: layers than if it was totally solid. Basically would get

567
00:28:57,040 --> 00:29:00,200
Speaker 1: squished more So by measuring really precisely the shape of

568
00:29:00,240 --> 00:29:02,720
Speaker 1: Mars as it spins and goes around the Sun, you

569
00:29:02,760 --> 00:29:04,480
Speaker 1: can get a sense for whether or not it has

570
00:29:04,480 --> 00:29:06,960
Speaker 1: a liquid layer. You mean, like as it goes around

571
00:29:06,960 --> 00:29:09,640
Speaker 1: the Sun or as it spins around its axis. Yeah,

572
00:29:09,720 --> 00:29:11,840
Speaker 1: basically the important thing is which side of it is

573
00:29:11,880 --> 00:29:14,040
Speaker 1: facing the Sun, because that's the part that's getting sort

574
00:29:14,040 --> 00:29:17,160
Speaker 1: of pulled towards the Sun really, and as it spins

575
00:29:17,160 --> 00:29:19,360
Speaker 1: and as it moves around the Sun, a different part

576
00:29:19,400 --> 00:29:22,040
Speaker 1: of it is facing the Sun, and so it's getting squeezed.

577
00:29:22,160 --> 00:29:25,160
Speaker 1: So if it was a solid rock, then it wouldn't

578
00:29:25,200 --> 00:29:27,920
Speaker 1: get really deformed by the gravity of the Sun much

579
00:29:27,960 --> 00:29:30,280
Speaker 1: as it goes around. But if it was liquid inside,

580
00:29:30,320 --> 00:29:32,040
Speaker 1: it might you know, kind of wish, kind of like

581
00:29:32,040 --> 00:29:35,479
Speaker 1: a drop of water in space. Yeah, exactly, That's exactly

582
00:29:35,480 --> 00:29:38,080
Speaker 1: what happens, and so we can measure that, and that

583
00:29:38,160 --> 00:29:40,520
Speaker 1: gives us some clue about whether or not there's a

584
00:29:40,560 --> 00:29:43,520
Speaker 1: liquid or solid layer inside Mars. All right, well, let's

585
00:29:43,520 --> 00:29:45,120
Speaker 1: get into some of the other ways we can tell

586
00:29:45,200 --> 00:29:48,600
Speaker 1: if Mars is soft and squishy on the inside or

587
00:29:48,640 --> 00:29:50,720
Speaker 1: if it's hardcore. So let's get into that. But first

588
00:29:50,800 --> 00:30:07,280
Speaker 1: let's take another quick break. Alright, is Mars hardcore or

589
00:30:07,520 --> 00:30:10,880
Speaker 1: is it just a big squishy or person inside. Now,

590
00:30:10,920 --> 00:30:12,880
Speaker 1: we talked about how we can tell, and we can

591
00:30:12,880 --> 00:30:16,280
Speaker 1: tell sometimes by the tidal effects of the Sun on

592
00:30:16,320 --> 00:30:19,640
Speaker 1: its shape. So that's one way, and that's happening to

593
00:30:19,840 --> 00:30:22,680
Speaker 1: us here on Earth. To Daniel, our Earth is getting squished. Yeah,

594
00:30:22,720 --> 00:30:25,680
Speaker 1: our Earth gets squished by the Sun and by the moon. Right,

595
00:30:25,880 --> 00:30:27,920
Speaker 1: the reason that we have tides in our ocean is

596
00:30:27,960 --> 00:30:30,680
Speaker 1: that the Moon is having exactly that same effect on

597
00:30:30,720 --> 00:30:34,000
Speaker 1: our liquid exterior, and then the Sun has that effect

598
00:30:34,080 --> 00:30:37,400
Speaker 1: on our liquid interior because it squeezes the whole planet.

599
00:30:37,440 --> 00:30:39,520
Speaker 1: All right, Well, what are some of the other ways

600
00:30:39,520 --> 00:30:43,480
Speaker 1: we could tell if Mars is soft or our inside.

601
00:30:43,560 --> 00:30:45,960
Speaker 1: Another way they do it is by measuring it's wobble.

602
00:30:46,120 --> 00:30:48,480
Speaker 1: So Mars is spinning and it's going around the Sun,

603
00:30:48,800 --> 00:30:51,920
Speaker 1: and they measure its orbit very very precisely. And something

604
00:30:51,920 --> 00:30:54,520
Speaker 1: with a liquid center will spin a little bit differently

605
00:30:54,600 --> 00:30:57,120
Speaker 1: than something with a solid center, because the liquid center,

606
00:30:57,120 --> 00:30:59,920
Speaker 1: for example, might not be keeping up with the rest

607
00:31:00,000 --> 00:31:01,840
Speaker 1: of the object, right, it might be flowing at a

608
00:31:01,880 --> 00:31:04,400
Speaker 1: different rate, and that's will affect how Mars sort of

609
00:31:04,440 --> 00:31:08,280
Speaker 1: wobbles as it goes around the Sun and changes its orbit.

610
00:31:08,680 --> 00:31:13,120
Speaker 1: Really because of like conservation of angular momentum, or is

611
00:31:13,160 --> 00:31:16,560
Speaker 1: it just like you know, like moving around a water

612
00:31:16,600 --> 00:31:18,959
Speaker 1: bottle with water in it. It just creates a lot

613
00:31:18,960 --> 00:31:22,280
Speaker 1: of kind of inner forces that kind of throw you off. Yeah. Well,

614
00:31:22,320 --> 00:31:24,640
Speaker 1: there is definitely a different moment of inertia for an

615
00:31:24,720 --> 00:31:28,120
Speaker 1: object that has liquid inside of it because the distributed differently,

616
00:31:28,160 --> 00:31:30,320
Speaker 1: like the density is different, right, So you can get

617
00:31:30,360 --> 00:31:33,280
Speaker 1: a sense for the interior density. But then also, as

618
00:31:33,320 --> 00:31:35,560
Speaker 1: you say, you're gonna get like flows and it's not

619
00:31:35,600 --> 00:31:37,840
Speaker 1: necessarily going to catch up to the rest of Mars.

620
00:31:38,320 --> 00:31:40,040
Speaker 1: And so you can tell sort of like you know,

621
00:31:40,080 --> 00:31:42,560
Speaker 1: the difference between having a liquid and solid based on

622
00:31:42,640 --> 00:31:45,960
Speaker 1: how sort of the angle of Mars spin changes as

623
00:31:46,000 --> 00:31:47,760
Speaker 1: it goes around it. Think of it's sort of like

624
00:31:47,760 --> 00:31:49,920
Speaker 1: a top. You know, a top that has a liquid

625
00:31:49,920 --> 00:31:52,200
Speaker 1: center will spin differently than the top that doesn't have

626
00:31:52,240 --> 00:31:54,640
Speaker 1: a liquid center. Right, Well, a top of the liquid

627
00:31:54,680 --> 00:31:57,560
Speaker 1: tender would slow down faster, wouldn't it. It depends on

628
00:31:57,600 --> 00:31:59,880
Speaker 1: if the liquid is initially spinning. I guess. So that

629
00:32:00,000 --> 00:32:02,960
Speaker 1: another way we can tell we can very carefully kind

630
00:32:02,960 --> 00:32:05,720
Speaker 1: of study the orbit of Mars. Yeah, but then the

631
00:32:05,720 --> 00:32:07,720
Speaker 1: most precise way, of course is to get down to

632
00:32:07,760 --> 00:32:11,200
Speaker 1: the surface and actually measure Mars quakes and use those

633
00:32:11,240 --> 00:32:14,680
Speaker 1: to get an internal picture of what's going on inside Mars. Oh,

634
00:32:14,720 --> 00:32:18,040
Speaker 1: I see, like get onto Mars surface and measure how

635
00:32:18,800 --> 00:32:22,480
Speaker 1: you know, sound ways to travel through the planet precisely.

636
00:32:22,840 --> 00:32:25,720
Speaker 1: And they did this originally on the Viking Landers. They

637
00:32:25,760 --> 00:32:28,920
Speaker 1: actually had seized moometers on the first two Viking Landers,

638
00:32:29,360 --> 00:32:31,640
Speaker 1: but it didn't really work like one of them, it

639
00:32:31,640 --> 00:32:34,560
Speaker 1: didn't deploy, so it didn't get onto the surface, and

640
00:32:34,640 --> 00:32:38,240
Speaker 1: the other one only ever heard one Mars quake, but

641
00:32:38,280 --> 00:32:41,040
Speaker 1: it was before it was actually touching the surface, and

642
00:32:41,040 --> 00:32:43,680
Speaker 1: so it was this very sort of controversial event in

643
00:32:43,800 --> 00:32:47,600
Speaker 1: planetary science community. Had Viking heard of Mars quake or not,

644
00:32:48,200 --> 00:32:52,600
Speaker 1: and so before inside landed on Mars fairly recently, nobody

645
00:32:52,680 --> 00:32:55,400
Speaker 1: knew if there actually were Mars quakes or if it

646
00:32:55,480 --> 00:32:58,360
Speaker 1: was just totally quiet thing. I guess, well, maybe first

647
00:32:58,360 --> 00:33:00,520
Speaker 1: of all, let's take a step back and maybe mentioned

648
00:33:00,520 --> 00:33:02,760
Speaker 1: briefly how you can use sound waves to tell what

649
00:33:02,800 --> 00:33:05,760
Speaker 1: the core looks like like the sound waves traveled differently

650
00:33:05,800 --> 00:33:08,040
Speaker 1: if there was liquid or solid. Yeah, just like we

651
00:33:08,080 --> 00:33:10,120
Speaker 1: do for the Earth, as we talked about earlier. If

652
00:33:10,120 --> 00:33:13,040
Speaker 1: there are Mars quakes, then they generate these compression waves,

653
00:33:13,040 --> 00:33:16,440
Speaker 1: and those compression waves will bounce off of interior layers,

654
00:33:16,560 --> 00:33:19,120
Speaker 1: and so if there's a interface between the layers, like

655
00:33:19,360 --> 00:33:22,720
Speaker 1: a solid mantle and then a liquid layer. Then you'll

656
00:33:22,760 --> 00:33:25,200
Speaker 1: have the sound waves bounce off differently than it's just

657
00:33:25,360 --> 00:33:28,720
Speaker 1: all solid, just like light going through glass or hitting water.

658
00:33:28,880 --> 00:33:31,160
Speaker 1: When you transfer from one medium to another or from

659
00:33:31,160 --> 00:33:33,560
Speaker 1: one density to another, you're gonna get all sorts of

660
00:33:33,600 --> 00:33:36,440
Speaker 1: complicated reflections. And if you measure the sound waves on

661
00:33:36,480 --> 00:33:38,520
Speaker 1: the surface, then you can get a picture of that.

662
00:33:38,760 --> 00:33:40,400
Speaker 1: It can give you a map of the interior of

663
00:33:40,400 --> 00:33:43,640
Speaker 1: the planet I see, and then from the density map

664
00:33:43,720 --> 00:33:46,040
Speaker 1: you can maybe infer like, oh, this part is less dense,

665
00:33:46,080 --> 00:33:49,239
Speaker 1: it must be liquid. But also those transition points are

666
00:33:49,240 --> 00:33:52,560
Speaker 1: really important. You can tell where the transition points are

667
00:33:52,880 --> 00:33:56,520
Speaker 1: by telling when the reflection happened in exactly the direction

668
00:33:56,600 --> 00:33:59,360
Speaker 1: that the wave wind. And we actually have confirmation that

669
00:33:59,400 --> 00:34:02,800
Speaker 1: there are Mars quakes, like we've seen them or felt them,

670
00:34:02,920 --> 00:34:05,320
Speaker 1: or do we know for sure? Yeah, we actually do

671
00:34:05,400 --> 00:34:08,400
Speaker 1: have now. So the inside lander that's sitting on Mars,

672
00:34:08,480 --> 00:34:11,200
Speaker 1: it has the seized momometer on it. And so the

673
00:34:11,280 --> 00:34:13,960
Speaker 1: lander landed and then put out this cute little bubble

674
00:34:14,160 --> 00:34:16,600
Speaker 1: which sits on the surface of Mars, and it's shielded

675
00:34:16,640 --> 00:34:18,799
Speaker 1: from the sun and from the wind, and it just

676
00:34:18,960 --> 00:34:21,880
Speaker 1: listens to the surface of Mars. So before they landed,

677
00:34:21,880 --> 00:34:24,359
Speaker 1: they had all these theories about how you might get

678
00:34:24,480 --> 00:34:27,960
Speaker 1: Mars quakes even without any tectonic activity. Right, there's no

679
00:34:28,200 --> 00:34:31,360
Speaker 1: like plates on Mars. You don't have like earthquakes on

680
00:34:31,400 --> 00:34:33,640
Speaker 1: Mars the same way you have on Earth because you

681
00:34:33,680 --> 00:34:36,560
Speaker 1: don't have tectonic activity. But they thought that you would

682
00:34:36,560 --> 00:34:39,239
Speaker 1: still have little Mars quakes. So they landed this thing

683
00:34:39,280 --> 00:34:42,480
Speaker 1: on Mars and they saw like four hundred and fifty

684
00:34:42,560 --> 00:34:47,360
Speaker 1: Mars quakes in two thousand nineteen. Wait, what four hundred

685
00:34:47,560 --> 00:34:51,040
Speaker 1: Mars quakes a year? Yeah, so more than one every day.

686
00:34:51,120 --> 00:34:53,640
Speaker 1: And these are pretty small. Little quakes are like, you know,

687
00:34:53,800 --> 00:34:56,280
Speaker 1: things that the sizedmometer could pick up but you wouldn't

688
00:34:56,320 --> 00:34:59,720
Speaker 1: necessarily notice. Could it be the Mars inside their caves

689
00:34:59,800 --> 00:35:03,000
Speaker 1: kind partying or something jumping up and down. It's actually

690
00:35:03,000 --> 00:35:05,799
Speaker 1: really fascinating. In order to understand whether they could be

691
00:35:05,960 --> 00:35:09,600
Speaker 1: quakes on Mars without tectonic activity, right, without these tectonic

692
00:35:09,600 --> 00:35:11,920
Speaker 1: plates smashing into each other, they look to see if

693
00:35:11,920 --> 00:35:16,319
Speaker 1: there are earthquakes on Earth far away from the plate boundaries,

694
00:35:16,640 --> 00:35:18,319
Speaker 1: and it turns out that there are, So you can

695
00:35:18,360 --> 00:35:21,120
Speaker 1: get earthquakes even where you don't have plates that can

696
00:35:21,160 --> 00:35:23,640
Speaker 1: come from like the sun heating up big slabs of

697
00:35:23,719 --> 00:35:27,800
Speaker 1: rock which then expand, or things happening underneath that affect

698
00:35:27,880 --> 00:35:30,960
Speaker 1: you know, how the crust is moving. And so from

699
00:35:31,000 --> 00:35:33,319
Speaker 1: those models, they expected there to be a bunch of

700
00:35:33,320 --> 00:35:35,320
Speaker 1: Mars quakes, and then they put this thing on Mars

701
00:35:35,320 --> 00:35:38,440
Speaker 1: and they actually see these quakes. Interesting, like, even if

702
00:35:38,480 --> 00:35:40,879
Speaker 1: there are no liquid core, and there are in any

703
00:35:40,920 --> 00:35:44,480
Speaker 1: like big giant plates of rock floating and crashing into

704
00:35:44,520 --> 00:35:46,600
Speaker 1: each other, you can still get earthquakes just from a

705
00:35:46,680 --> 00:35:49,160
Speaker 1: rock just sitting there getting keated out by the sun. Yeah,

706
00:35:49,320 --> 00:35:52,080
Speaker 1: and that's not something that we understand very very well,

707
00:35:52,160 --> 00:35:54,480
Speaker 1: and so it's something they're curious about. They were really

708
00:35:54,480 --> 00:35:56,359
Speaker 1: curious when they landed this thing, like what we see

709
00:35:56,360 --> 00:35:58,440
Speaker 1: with the level of quakes we expected, or where they

710
00:35:58,480 --> 00:36:00,320
Speaker 1: be a lot more than we expected, will be a

711
00:36:00,360 --> 00:36:03,600
Speaker 1: lot quieter than we expected. They had some pretty good arguments,

712
00:36:03,600 --> 00:36:06,000
Speaker 1: but they just weren't sure. You know. That's why we

713
00:36:06,040 --> 00:36:08,160
Speaker 1: go explore the Solar system. And so we measured four

714
00:36:08,520 --> 00:36:12,560
Speaker 1: and fifty Mars quakes in and then twenty they stopped

715
00:36:12,560 --> 00:36:16,040
Speaker 1: because of the pandemic. Also, No, that's just the latest

716
00:36:16,080 --> 00:36:18,400
Speaker 1: data that they've released, so that's the latest result. But

717
00:36:18,440 --> 00:36:20,880
Speaker 1: you know, they're still analyzing data. This is an active

718
00:36:20,880 --> 00:36:23,840
Speaker 1: area research. They're still collecting data, and they're still waiting

719
00:36:24,160 --> 00:36:27,000
Speaker 1: for a really big quake. So far, they've seen sort

720
00:36:27,000 --> 00:36:29,160
Speaker 1: of a lot of small quakes, and I think they're

721
00:36:29,160 --> 00:36:31,640
Speaker 1: a little bit disappointed. They were hoping for like a

722
00:36:31,640 --> 00:36:33,840
Speaker 1: bunch of big ones, because the big ones are the

723
00:36:33,840 --> 00:36:36,160
Speaker 1: ones that carry a lot of energy and really help

724
00:36:36,200 --> 00:36:39,160
Speaker 1: them see the interior. With the smaller quakes, it doesn't

725
00:36:39,160 --> 00:36:42,000
Speaker 1: penetrate as deeply, so you can't really tell what's going on.

726
00:36:42,440 --> 00:36:44,440
Speaker 1: So they're sort of hanging out waiting to get lucky.

727
00:36:44,560 --> 00:36:47,480
Speaker 1: So they have detected Mars quakes, but there aren't big

728
00:36:47,600 --> 00:36:49,760
Speaker 1: enough for them to sort of be able to see

729
00:36:49,920 --> 00:36:52,560
Speaker 1: much about the inter core. They're not as big as

730
00:36:52,600 --> 00:36:55,360
Speaker 1: they hoped, but you know, they are clever scientists, and

731
00:36:55,400 --> 00:36:58,640
Speaker 1: so they've developed fancy new ideas for how to use

732
00:36:58,680 --> 00:37:01,560
Speaker 1: these to see the interior here anyway, and it's not

733
00:37:01,719 --> 00:37:04,279
Speaker 1: as powerful as they would have hoped until they get

734
00:37:04,320 --> 00:37:06,600
Speaker 1: like a really big one in all of Mars rings

735
00:37:06,640 --> 00:37:08,879
Speaker 1: like a bell. But they have been able to get

736
00:37:08,880 --> 00:37:11,640
Speaker 1: a pretty good picture for what's going on all right, well,

737
00:37:11,680 --> 00:37:15,080
Speaker 1: then that's out there on Mars, and Katherine Johnson is

738
00:37:15,120 --> 00:37:17,239
Speaker 1: one of the scientists on it. So what did she

739
00:37:17,280 --> 00:37:19,520
Speaker 1: say that we've found so far? So I asked her

740
00:37:19,560 --> 00:37:22,040
Speaker 1: to give me the insight on Mars and tell me

741
00:37:22,080 --> 00:37:24,200
Speaker 1: what's going on in the interior. And here's what she

742
00:37:24,280 --> 00:37:26,360
Speaker 1: had to say. So, we've had a good idea for

743
00:37:26,640 --> 00:37:30,399
Speaker 1: quite a while now a decade or so, that the

744
00:37:30,440 --> 00:37:33,840
Speaker 1: deepest interior of Mars is at least partly fluid, but

745
00:37:33,880 --> 00:37:37,000
Speaker 1: we haven't been able to confirm it with seismology, and

746
00:37:37,120 --> 00:37:39,600
Speaker 1: that's something that we're hoping to do with the Insight

747
00:37:39,800 --> 00:37:42,560
Speaker 1: mission that's currently on Mars. And the other thing that

748
00:37:42,600 --> 00:37:46,200
Speaker 1: we really haven't known is how big it's core is.

749
00:37:46,760 --> 00:37:49,160
Speaker 1: This is really important because we don't know exactly how

750
00:37:49,200 --> 00:37:51,400
Speaker 1: big it is. The trade off is it could be

751
00:37:51,560 --> 00:37:54,560
Speaker 1: smaller and pure metal or a bit bigger with some

752
00:37:54,960 --> 00:37:58,080
Speaker 1: light stuff mixed in with it. So it seems like

753
00:37:58,200 --> 00:38:02,319
Speaker 1: Mars does have liquid in its core. Really they can tell, Yeah,

754
00:38:02,520 --> 00:38:05,200
Speaker 1: it's at least partly fluid. That's what she said. And

755
00:38:05,360 --> 00:38:08,279
Speaker 1: all these different methods that we've been using, the Wibble method,

756
00:38:08,360 --> 00:38:12,080
Speaker 1: the Wobble method, and these seismic methods all sort of

757
00:38:12,120 --> 00:38:14,960
Speaker 1: tell the same story that there is some liquid in

758
00:38:15,000 --> 00:38:18,160
Speaker 1: the interior of Mars, interesting like at the core or

759
00:38:18,200 --> 00:38:20,960
Speaker 1: as a layer, probably as a layer on the outer core,

760
00:38:21,239 --> 00:38:23,000
Speaker 1: just like with the Earth. You know, in the Earth,

761
00:38:23,040 --> 00:38:25,520
Speaker 1: as you go into the Earth, you have the mantle

762
00:38:25,840 --> 00:38:27,440
Speaker 1: and then you have sort of an outer core and

763
00:38:27,600 --> 00:38:31,160
Speaker 1: inter core, and there you have like increasing temperature and pressure.

764
00:38:31,400 --> 00:38:34,040
Speaker 1: At first, temperature winds and things are like hot and melty,

765
00:38:34,280 --> 00:38:36,960
Speaker 1: and then as you get to the very center, pressure winds.

766
00:38:37,040 --> 00:38:39,839
Speaker 1: Even though things are still really hot, pressure takes over

767
00:38:39,880 --> 00:38:41,960
Speaker 1: and you have a solid core. So they think that's

768
00:38:41,960 --> 00:38:44,520
Speaker 1: probably what's happening on Mars. Also, you have this core

769
00:38:44,600 --> 00:38:48,440
Speaker 1: that's like eight kilometers and radius and the outer layers

770
00:38:48,480 --> 00:38:51,400
Speaker 1: of it probably liquid, so they feel pretty confident. Then

771
00:38:51,440 --> 00:38:54,239
Speaker 1: they know the answer. So all of our listeners were,

772
00:38:54,280 --> 00:38:57,439
Speaker 1: how wrong, or most of them were, as I would

773
00:38:57,440 --> 00:39:00,759
Speaker 1: have been, But that's pretty surprising. So they found that

774
00:39:00,880 --> 00:39:03,680
Speaker 1: Mars does have a liquid center, Yeah, exactly. Mars is

775
00:39:03,719 --> 00:39:06,160
Speaker 1: still hot and young, and I was surprised as well.

776
00:39:06,200 --> 00:39:08,640
Speaker 1: You know, I also expected Mars to be solid because

777
00:39:08,680 --> 00:39:11,200
Speaker 1: it seems cold and it's small, and I expected things

778
00:39:11,239 --> 00:39:13,279
Speaker 1: will have cooled off and for all the reasons we

779
00:39:13,280 --> 00:39:15,640
Speaker 1: gave before, it seemed like a reasonable guest, but you

780
00:39:15,719 --> 00:39:18,040
Speaker 1: never know until you actually go out there and measure it.

781
00:39:18,280 --> 00:39:20,920
Speaker 1: There are surprises out there waiting for us, and so

782
00:39:20,960 --> 00:39:23,600
Speaker 1: we are still learning a lot about how planets form

783
00:39:23,800 --> 00:39:26,600
Speaker 1: and how they develop into their middle age. Can you

784
00:39:26,600 --> 00:39:29,319
Speaker 1: still call it lava or magma or would it be

785
00:39:29,360 --> 00:39:31,880
Speaker 1: like marthma. I'm not sure what the name of it

786
00:39:31,880 --> 00:39:34,239
Speaker 1: would be, but this is stuff much much deeper than

787
00:39:34,239 --> 00:39:36,880
Speaker 1: the outer layers, right, Magma is actually part of the

788
00:39:36,920 --> 00:39:39,839
Speaker 1: crust that's become liquid because it's become really hot. We're

789
00:39:39,840 --> 00:39:42,880
Speaker 1: talking about stuff that's below the crust, below the mantle,

790
00:39:43,120 --> 00:39:46,759
Speaker 1: down into the core itself, like the real interior Mars.

791
00:39:46,800 --> 00:39:49,200
Speaker 1: This other question of like is there magma still on

792
00:39:49,239 --> 00:39:53,400
Speaker 1: Mars is another fascinating question because vulcanism on Mars seems

793
00:39:53,440 --> 00:39:55,920
Speaker 1: to have ended fairly recently, so it could be that

794
00:39:56,080 --> 00:39:59,160
Speaker 1: inside the crust of Mars there is still some sort

795
00:39:59,160 --> 00:40:02,719
Speaker 1: of hot mac interesting. That's cool. Maybe when we get

796
00:40:02,760 --> 00:40:06,120
Speaker 1: there we could use that for energy. Is that possible, Yeah, absolutely,

797
00:40:06,120 --> 00:40:08,160
Speaker 1: it's possible. You know, I guess it wouldn't be called

798
00:40:08,280 --> 00:40:14,840
Speaker 1: geo thermal energy and be called like mart show thermal energy, yeah,

799
00:40:15,440 --> 00:40:19,440
Speaker 1: mio thermal energy. But Mars has a thicker crust we

800
00:40:19,520 --> 00:40:21,279
Speaker 1: think than the Earth does. We think the crust is

801
00:40:21,320 --> 00:40:24,400
Speaker 1: like fifty to a hundred kilometers thick, so it's probably

802
00:40:24,400 --> 00:40:26,640
Speaker 1: colder and thicker. So it might be harder to find

803
00:40:26,719 --> 00:40:29,600
Speaker 1: a spot where there's still like you know, active magma.

804
00:40:29,640 --> 00:40:31,480
Speaker 1: We don't even know if there is still. But you know,

805
00:40:31,560 --> 00:40:34,520
Speaker 1: Mars had is like volcanic history for billions of years,

806
00:40:34,600 --> 00:40:37,440
Speaker 1: which seems to have ended kind of recently, so it

807
00:40:37,480 --> 00:40:39,920
Speaker 1: would be a surprise if there was totally cold and

808
00:40:40,000 --> 00:40:42,239
Speaker 1: quiet in the interior in terms of the crust. So

809
00:40:42,239 --> 00:40:46,360
Speaker 1: it's just another flavor of peanut butter, maybe crusty, smooth,

810
00:40:46,440 --> 00:40:50,000
Speaker 1: crunchy and crusty. Mars is very multifacet that it is

811
00:40:50,040 --> 00:40:52,320
Speaker 1: not just two layers, man, There are layers and layers

812
00:40:52,320 --> 00:40:55,399
Speaker 1: and layers. Mars was co co co co extruded. All right,

813
00:40:55,520 --> 00:40:58,360
Speaker 1: Well that's a pretty surprising answer, and thank you to

814
00:40:58,480 --> 00:41:00,799
Speaker 1: Katherine Johnson for helping us out. And it just goes

815
00:41:00,840 --> 00:41:03,160
Speaker 1: to show you how many surprises are out there waiting

816
00:41:03,239 --> 00:41:06,640
Speaker 1: in our own backyard or in our neighbor's backyard, and

817
00:41:06,680 --> 00:41:08,799
Speaker 1: you just have to go out there and check, or

818
00:41:08,840 --> 00:41:11,240
Speaker 1: at least, you know, spent a few billion dollars building

819
00:41:11,239 --> 00:41:14,320
Speaker 1: a little robot doesn't for you? Yeah, exactly, build a

820
00:41:14,320 --> 00:41:17,040
Speaker 1: big robot and use it to investigate your neighbor's backyard.

821
00:41:17,120 --> 00:41:19,640
Speaker 1: See how that goes, See how that works out. You

822
00:41:19,719 --> 00:41:22,360
Speaker 1: might call the solar system police on you use it

823
00:41:22,400 --> 00:41:25,440
Speaker 1: to steal their peanut Butterfield pretzels or their vapen so

824
00:41:25,480 --> 00:41:28,440
Speaker 1: you can do some experiments at home. All right, Well,

825
00:41:28,480 --> 00:41:31,439
Speaker 1: we hope you enjoyed then and came away thinking that

826
00:41:31,680 --> 00:41:33,960
Speaker 1: maybe the even our own backyard, It's not what it

827
00:41:34,000 --> 00:41:37,120
Speaker 1: seems sometimes, so keep its gloring, keep asking questions, and

828
00:41:37,160 --> 00:41:47,640
Speaker 1: thanks for tuning in. See you next time. Thanks for listening,

829
00:41:47,640 --> 00:41:50,360
Speaker 1: and remember that Daniel and Jorge Explain the Universe is

830
00:41:50,400 --> 00:41:53,880
Speaker 1: a production of I Heart Radio. For more podcast from

831
00:41:53,920 --> 00:41:57,680
Speaker 1: my Heart Radio, visit the i heart Radio app, Apple Podcasts,

832
00:41:57,800 --> 00:42:00,080
Speaker 1: or wherever you listen to your favorite show. This