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Does Mars Have a Liquid Center? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Jorgey, I have a food engineering question for you.
• 0:12
  Speaker 1: Food engineering. We're trying to melt ice cream with a
• 0:15
  Speaker 1: particle collider, not yet, but now I'm gonna go try that.
• 0:18
  Speaker 1: Now I'm wondering how they engineer foods with a liquid
• 0:22
  Speaker 1: center inside. Okay, now you're trying to make our candy
• 0:25
  Speaker 1: with liquid inside? Yeah? Or like, how do they make
• 0:28
  Speaker 1: peanut butter vealed pretzels? That's a billion dollars secret. I
• 0:31
  Speaker 1: can't just reveal it. We might get sued. Alright, I
• 0:35
  Speaker 1: guess we should stick to revealing big science secrets. Yeah.
• 0:38
  Speaker 1: I don't think we'll get sued for those. They're usually
• 0:40
  Speaker 1: free and maybe also useless. You said it not mean. Hi.
• 1:00
  Speaker 1: I am more Hammon cartoonists and the creator of PhD comics. Hi.
• 1:04
  Speaker 1: I'm Daniel. I'm a particle physicist, and I do enjoy
• 1:07
  Speaker 1: me a peanut butter field pretzel. Really, why can't you
• 1:10
  Speaker 1: just put the peanut butter on the outside. It's a
• 1:14
  Speaker 1: totally different taste experience, man, I mean this can't be compared. Plus,
• 1:18
  Speaker 1: I admire the engineering. Somehow they baked this pretzel around
• 1:22
  Speaker 1: the peanut butter. It's incredible. You think that's how they
• 1:25
  Speaker 1: do it. They formed the bread around the peanut butter.
• 1:28
  Speaker 1: Actually did some research about this. It was the basis
• 1:30
  Speaker 1: of a big lawsuit. And there's a fancy co extrusion
• 1:33
  Speaker 1: process where they have the pretzel dough around the peanut
• 1:36
  Speaker 1: butter and then they bake it. Co extrusion. Wow, that
• 1:40
  Speaker 1: sounds like a heavy duty physics term. You should google it.
• 1:44
  Speaker 1: They used to find some really fun YouTube videos about
• 1:46
  Speaker 1: the interior of these factories. Pretty fascinating food engineering. And
• 1:50
  Speaker 1: by experiments, you mean you tried it at home a
• 1:52
  Speaker 1: bunch of times, or you ate a bunch of pretzels
• 1:54
  Speaker 1: with peanut butter. I ate a bunch of pretzels. I
• 1:56
  Speaker 1: tried the chocolate covered versions, the non chocolate cover versions.
• 1:59
  Speaker 1: I'm in the name of science. Have you tried coach
• 2:02
  Speaker 1: twinging butter and pretzels? That's the next level heart attack recipe.
• 2:06
  Speaker 1: You should sell that idea to Ben and Jerry's. But anyways,
• 2:09
  Speaker 1: welcome to our podcast, Daniel and Jorge Explain the Universe,
• 2:11
  Speaker 1: a production of I Heart Radio in which we extrude
• 2:14
  Speaker 1: ideas about the universe into your head without breaking your skull. Somehow,
• 2:20
  Speaker 1: we wrap your mind around the peanut butter field delicious
• 2:23
  Speaker 1: secrets of the universe. We talk about all of the
• 2:26
  Speaker 1: crazy stuff happening deep out in crazy space, and all
• 2:29
  Speaker 1: the tiny stuff happening in between your toes and the
• 2:32
  Speaker 1: smallest particles. We break down quantum mechanics, We talk about
• 2:35
  Speaker 1: astrophysics and everything in between. Wait, I thought that the
• 2:39
  Speaker 1: science secrets that we reveal our the pretzel part that
• 2:42
  Speaker 1: surrounds the yummy peanut butter inside of our punts. It
• 2:47
  Speaker 1: could be I was thinking of my brain is the
• 2:49
  Speaker 1: peanut butter and my skull is the pretzel. You just
• 2:53
  Speaker 1: ruined that vision of deliciousness for me. Every time you
• 2:56
  Speaker 1: bite into one of those from now on, just think
• 2:58
  Speaker 1: I'm eating Daniel's head, not mom goodness, let's please hitit
• 3:03
  Speaker 1: that out. But anyways, we do like to talk about
• 3:05
  Speaker 1: the universe and all of it's amazing goodness inside and
• 3:09
  Speaker 1: everything that you can quote through it, inside of it,
• 3:11
  Speaker 1: and all the things that you can discover because it's
• 3:14
  Speaker 1: the big cosmos and there are wonderful things out there
• 3:17
  Speaker 1: hiding in plain sight, that's right. And the more we
• 3:20
  Speaker 1: look out into the universe, the more we discover these
• 3:22
  Speaker 1: surprises and the more questions we have about exactly how
• 3:25
  Speaker 1: things work, what layers they're in, and how they're organized
• 3:28
  Speaker 1: and how they got that way, right, because we can
• 3:31
  Speaker 1: see the universe and touch it and probe, but who
• 3:33
  Speaker 1: knows what's line underneath the surface, what is at the
• 3:36
  Speaker 1: core of the universe and how it works. And everything
• 3:40
  Speaker 1: that's out there has a history. The Moon, the Earth, Mars,
• 3:43
  Speaker 1: every planet, every star has a sometimes billion years long history,
• 3:48
  Speaker 1: a crazy story that tells us how it got to
• 3:50
  Speaker 1: be the way it is today. And unraveling that story
• 3:53
  Speaker 1: is like the biggest, most delicious detective mystery in the universe.
• 3:57
  Speaker 1: Figuring out what exactly happened to the object. Can we
• 4:01
  Speaker 1: tell just by looking on the outside or just by
• 4:03
  Speaker 1: looking through a telescope, exactly what the story is of
• 4:06
  Speaker 1: this heavenly body? Yeah, because we want to know, right,
• 4:09
  Speaker 1: the species as human beings, were curious about where things
• 4:13
  Speaker 1: came from and how they got to be the way
• 4:15
  Speaker 1: they got to be, and that's all part of their history,
• 4:18
  Speaker 1: and it's all they're inside of the things for looking at. Yeah,
• 4:22
  Speaker 1: we showed up in this universe basically the last minute,
• 4:25
  Speaker 1: and a lot of stuff happened before we got here.
• 4:27
  Speaker 1: So it's fun to unravel those stories and figure out
• 4:30
  Speaker 1: have things looked this way for a long time? The
• 4:32
  Speaker 1: things used to be really different. Does that mean things
• 4:34
  Speaker 1: are going to change? It's all just part of like
• 4:37
  Speaker 1: becoming conscious beings and exploring the world that we find
• 4:40
  Speaker 1: around us. So today we'll be talking about one of
• 4:42
  Speaker 1: these mysteries. Line underneath the surface of our own neighborhood.
• 4:46
  Speaker 1: It's something that we can see almost every night, but
• 4:49
  Speaker 1: that is kind of hidden from us, right, that's right.
• 4:51
  Speaker 1: We have questions about what's beneath our feet, and we
• 4:53
  Speaker 1: have questions about what's beneath the feet of potential neighbors.
• 4:57
  Speaker 1: You mean the actual neighbors. Like is your neighbor sitting
• 5:00
  Speaker 1: on top of a giant oil well or something? Yeah,
• 5:02
  Speaker 1: maybe there's like a huge peanut butter deposit under my
• 5:05
  Speaker 1: neighbor's house and I could sell that to that factory. Yeah,
• 5:08
  Speaker 1: instead of liquid gold, that's liquid saturated fats. Well, it's
• 5:13
  Speaker 1: peanut butter technically a liquid or is it a solid?
• 5:15
  Speaker 1: I guess it depends if it's smooth or what's the
• 5:18
  Speaker 1: other one crunching? What is the phase diagram of peanut butter?
• 5:22
  Speaker 1: Can it sublimate into a gas? I wonder. I don't
• 5:24
  Speaker 1: know if anybody's ever done that experiment. You mean, like
• 5:27
  Speaker 1: go straight into a gas form of peanut butter, like
• 5:29
  Speaker 1: you can invade peanut butter. Not recommended, folks, not recommended.
• 5:34
  Speaker 1: Our lawyers have not vetted that statement. Please do not
• 5:37
  Speaker 1: vape peanut butter. You could clog through your lungs directly
• 5:40
  Speaker 1: with peanut butter. But if you do vape peanut butter,
• 5:42
  Speaker 1: tell us about it, because we're curious that may will
• 5:45
  Speaker 1: be another billion dollar industry who knows, or a billion
• 5:48
  Speaker 1: dollar lawsuit. We're about to get hit with people who
• 5:50
  Speaker 1: use it to cure their pretzel addiction, and then they'll
• 5:55
  Speaker 1: need some patches, some peanut butter patches. Anyways, Yeah, we'll
• 5:58
  Speaker 1: be tackling one such mystry in our own solar system,
• 6:02
  Speaker 1: so to be on the podcast, we'll be asking the question,
• 6:09
  Speaker 1: does Mars have a solid or liquid core? I guess
• 6:13
  Speaker 1: the question is Mars hardcore or softcore? Is it a
• 6:17
  Speaker 1: hard boiled egg or a soft boiled egg? Exactly? I
• 6:20
  Speaker 1: think it's a super fascinating question, and it's fun for
• 6:23
  Speaker 1: me because I think about like when people were asking
• 6:26
  Speaker 1: this question about the Earth, you know, for a long time,
• 6:28
  Speaker 1: we didn't really know, like, hey, what's the Earth made
• 6:31
  Speaker 1: out of? It's just one big rock? Or is there
• 6:33
  Speaker 1: something crazy going on under our own feet? And now
• 6:36
  Speaker 1: that we have a little bit of a sense of
• 6:38
  Speaker 1: what's going on inside the Earth, we can ask similar
• 6:40
  Speaker 1: questions about other planets, and so it's fascinating to wonder, like,
• 6:43
  Speaker 1: are they different, are they the same? What's going on?
• 6:46
  Speaker 1: I guess just to verify, the Earth has a softcore. Right,
• 6:49
  Speaker 1: The inside of our planet is molten, right, It's like
• 6:52
  Speaker 1: melted rock. Yeah, there's some melted rock and a lot
• 6:54
  Speaker 1: of melted metal, melted iron, liquid nickel, all this kind
• 6:58
  Speaker 1: of stuff flowing underneath our feet. It's part of why
• 7:00
  Speaker 1: we have, for example, a magnetic field. I see now,
• 7:03
  Speaker 1: I guess, is it possible for a planet of our
• 7:05
  Speaker 1: size to have a solid core? Like, wouldn't all that pressure,
• 7:09
  Speaker 1: gravity pressure eventually kind of I don't know, melt the
• 7:12
  Speaker 1: stuff inside. Yeah. The reason that we do have a
• 7:14
  Speaker 1: liquid core is because of all that temperature and pressure,
• 7:17
  Speaker 1: and that comes from both the gravitational pressure and also
• 7:20
  Speaker 1: the decay of the isotopes inside the Earth that helped
• 7:22
  Speaker 1: keep it hot. But it's not going to be that
• 7:24
  Speaker 1: way forever. You know, we got a certain spoonful of Earth,
• 7:28
  Speaker 1: and eventually it's gonna cool off. I think we estimated
• 7:31
  Speaker 1: once on this podcast that it's going to take more
• 7:32
  Speaker 1: than a hundred billion years before the Earth cools, So
• 7:36
  Speaker 1: we got some time, and you know, the Sun is
• 7:38
  Speaker 1: going to go red super giant before that, so it's
• 7:40
  Speaker 1: not going to be our number one problem. But other
• 7:43
  Speaker 1: planets are different sizes and so they will have different
• 7:46
  Speaker 1: cooling off times. It's gonna be a while before we're cool.
• 7:50
  Speaker 1: I can relate to that. Hey, we're gonna be young
• 7:52
  Speaker 1: and hot for a long time. Think about it that way.
• 7:54
  Speaker 1: That sounds very hard corn, all right, But they were
• 7:57
  Speaker 1: asking questions about Mars. Does Mars have a solid or
• 8:00
  Speaker 1: liquid core? And it's kind of a big deal, right
• 8:02
  Speaker 1: because it might tell us whether or not Mars is
• 8:06
  Speaker 1: still you know, sort of young and active, and it
• 8:09
  Speaker 1: might tell us also what our future might be for
• 8:11
  Speaker 1: that's right. And I think it's just a question that
• 8:13
  Speaker 1: people have when they look up into the sky and
• 8:15
  Speaker 1: they wonder, you know, is that planet over there a
• 8:18
  Speaker 1: lot like our planet or is it totally different? And
• 8:21
  Speaker 1: what does that mean about the nature of planets and
• 8:23
  Speaker 1: planets in other solar systems, and it's to me just
• 8:26
  Speaker 1: really connects with this basic, simple initial curiosity we have
• 8:30
  Speaker 1: when we look up at the sky, we wonder what
• 8:33
  Speaker 1: those things are like. Hey, but before we answer this question,
• 8:36
  Speaker 1: we wanted to answer a question from one of our listeners,
• 8:39
  Speaker 1: perhaps our youngest listener. That's right. You may remember last
• 8:43
  Speaker 1: week we talked about Hannah, who was home sick from school.
• 8:46
  Speaker 1: She's two and a half years old. She lives in
• 8:47
  Speaker 1: Australia and she wanted to hear Daniel and Jorge. So
• 8:51
  Speaker 1: I reached out to her dad and asked him, Hey,
• 8:53
  Speaker 1: does Hannah have any questions she wants us to answer
• 8:55
  Speaker 1: while she's homesick? And he asked her what questions she
• 8:59
  Speaker 1: had for day own Jorge, and she said, monkey, wait? Monkey?
• 9:03
  Speaker 1: Is her question? Was her first question or answer to
• 9:06
  Speaker 1: the universe and everything in it? I don't know. It's
• 9:09
  Speaker 1: hard to get in the mind of a two and
• 9:10
  Speaker 1: a half year old sometimes. But then he asked her again,
• 9:13
  Speaker 1: and so here's Hannah's real question. How and how my
• 9:18
  Speaker 1: land home? Why is the Larne shine? Oh that's adorable.
• 9:26
  Speaker 1: It's like a little tiny little nerd. Yeah, and she
• 9:29
  Speaker 1: has the same curiosity. Today we're talking about Mars and
• 9:31
  Speaker 1: what's in it, But you know, she's looking up in
• 9:33
  Speaker 1: the sky and she's wondering, why is that thing up
• 9:36
  Speaker 1: there glowing at me? It has the same root of curiosity.
• 9:39
  Speaker 1: I see you're saying that it taps into that same
• 9:42
  Speaker 1: like looking up at the sky and wondering what's going
• 9:44
  Speaker 1: on out there? Yeah, exactly why is that thing up
• 9:47
  Speaker 1: there doing that thing that it's doing? Well? Really quickly?
• 9:50
  Speaker 1: Then what is the answer for Hannah? Why does the
• 9:52
  Speaker 1: moon shine? Yeah, Hannah, the reason the moon shines, especially
• 9:56
  Speaker 1: at night, is that it's actually reflecting light from the Sun.
• 9:59
  Speaker 1: Even though you can't see the sun at night, the
• 10:02
  Speaker 1: sun can see the moon, and so the Sun's light
• 10:05
  Speaker 1: bounces off the moon and down to your eyeball. So
• 10:08
  Speaker 1: at night you're kind of seeing the sun by seeing
• 10:11
  Speaker 1: it reflect off the moon. So moonlight is all just
• 10:14
  Speaker 1: reflected sunlight. Right. Do you think she's asking about moonshine
• 10:17
  Speaker 1: as well? Why does my dad drink so much moonshine?
• 10:21
  Speaker 1: I don't know. I think that's a question for her
• 10:22
  Speaker 1: dad and his father. There nothing wrong with moonshine, nothing
• 10:27
  Speaker 1: wrong with the little moonshine. All right, well, Hannah, that's
• 10:29
  Speaker 1: to your answer. The moon shines because it bounces light
• 10:32
  Speaker 1: from the sun, so it looks like it glows, but
• 10:34
  Speaker 1: really it's just kind of like a mirror, just reflecting
• 10:36
  Speaker 1: and getting lit up by the sun. That's right, all right,
• 10:39
  Speaker 1: Well back to our question, those marks have a solid
• 10:42
  Speaker 1: or liquid core? This is a pretty interesting question, and
• 10:45
  Speaker 1: we were wondering, as usual, if people out there and
• 10:48
  Speaker 1: new the answer to this billion year question. So thanks
• 10:51
  Speaker 1: to everybody who volunteered to answer this question as usual.
• 10:54
  Speaker 1: If you'd like to participate for future episodes, please write
• 10:57
  Speaker 1: to me two questions at Daniel and Jorge dot com.
• 11:00
  Speaker 1: Think about it first. Second, do you think Mars is
• 11:03
  Speaker 1: solid or liquid on the inside. Here's what people had
• 11:07
  Speaker 1: to say. Yes, they might be a big diamond inside it.
• 11:13
  Speaker 1: Now I think Mars has hot liquid. Yes, it does
• 11:18
  Speaker 1: completely solid, because Mars doesn't have any radioactive isotopes inside
• 11:23
  Speaker 1: the core. Keep it hot and keep it liquid. I'm
• 11:25
  Speaker 1: going to say, yes, Mars has a solid core of
• 11:29
  Speaker 1: iron or nickel or some other heavy element, just like Earth. Yes,
• 11:33
  Speaker 1: Mars has a solid core. It has no obvious plate
• 11:39
  Speaker 1: tectonics going on it obviously had some sort of tectonic
• 11:43
  Speaker 1: activity going on at some time, and the magnetic field
• 11:49
  Speaker 1: is almost non existent. So I think if we were
• 11:53
  Speaker 1: to dig deeper, I think we'd find it does have
• 11:56
  Speaker 1: a solid core. I don't think Mars has a significant
• 11:59
  Speaker 1: magnetic field because solar radiation is a concern for explorers.
• 12:04
  Speaker 1: I would say it cooled down at least a billion
• 12:07
  Speaker 1: years ago to a solid all the way through to
• 12:09
  Speaker 1: its core. Yes, I think it has and used to
• 12:15
  Speaker 1: be more powerful and active. But judging by the strength
• 12:22
  Speaker 1: of the magnetic field and the atmosphere, it weakened in time.
• 12:29
  Speaker 1: Probably that will happen to Earth to I don't know
• 12:34
  Speaker 1: for sure, but kind of this is the way I
• 12:38
  Speaker 1: think it would go. Mars does have a solid core.
• 12:42
  Speaker 1: End of story. I see you remember you saying in
• 12:45
  Speaker 1: an earlier podcast that Mars does not have um an
• 12:49
  Speaker 1: electromagnetic field protecting it because it doesn't have a solid core.
• 12:56
  Speaker 1: So I'm going to say no, all right, some pretty
• 13:01
  Speaker 1: definitive answers here. I feel like people were pretty confident
• 13:04
  Speaker 1: about their answers here. They're like, yes, definitely, this, definitely,
• 13:07
  Speaker 1: that definitely peanut butter, A big hot diamond. I like
• 13:11
  Speaker 1: that one. Why do you think people are so confident
• 13:13
  Speaker 1: this time? I think that a lot of people have
• 13:14
  Speaker 1: heard that Mars is smaller and cooled faster, doesn't have
• 13:18
  Speaker 1: volcanoes on the surface or a magnetic field, and so
• 13:22
  Speaker 1: I think that leads people to suspect that it might
• 13:24
  Speaker 1: just be a big lump of hard rock, unlike the
• 13:27
  Speaker 1: Earth and the story. All right, thanks for joining us, um,
• 13:31
  Speaker 1: But there's more, I see, there's more to the story.
• 13:35
  Speaker 1: There is more to the story, Yes, exactly. I think
• 13:37
  Speaker 1: there's some really interesting nuances here that these listeners will learn.
• 13:41
  Speaker 1: All right, well, let's dig into it. First of all, Daniel,
• 13:43
  Speaker 1: why is this question interesting to you, I guess and
• 13:47
  Speaker 1: to physicists and generally to the public. Why should we
• 13:50
  Speaker 1: care whether Mars is hardcore or soft and squishy on
• 13:53
  Speaker 1: the inside. Yeah, Well, for me, there's sort of two
• 13:56
  Speaker 1: levels there. One is just inherent curiosity, like I have questions,
• 14:00
  Speaker 1: is about what's inside stuff. You know, you ever get
• 14:02
  Speaker 1: a rock and you crack it open, you find a
• 14:04
  Speaker 1: crystal inside. There's like a joy there discovering something you
• 14:08
  Speaker 1: didn't expect, and so you always want to like look
• 14:10
  Speaker 1: inside stuff to see what's there. Maybe there's something hidden,
• 14:13
  Speaker 1: maybe there's a mystery. You know, that's why we explore
• 14:15
  Speaker 1: the universe. We don't just sit back and think about
• 14:17
  Speaker 1: it in our minds the way the Greeks do. So
• 14:19
  Speaker 1: we sort of want to know what's out there because
• 14:22
  Speaker 1: we could be shocked, we could be surprised. Mars couldn't
• 14:24
  Speaker 1: be like hollow on the inside and filled with aliens
• 14:27
  Speaker 1: or something. So we definitely want to go look and
• 14:29
  Speaker 1: see what's inside this stuff. But also I think there's
• 14:32
  Speaker 1: a question about just sort of the nature of planets,
• 14:35
  Speaker 1: Like we have an interest in how many planets are
• 14:38
  Speaker 1: out there, how do they form, what do they look like?
• 14:40
  Speaker 1: Are their potential homes for humanity out there? And to
• 14:43
  Speaker 1: get an answers to that, we really need to know
• 14:45
  Speaker 1: like how planets warm and what they're made out of
• 14:47
  Speaker 1: it that will give us an answer to like what
• 14:49
  Speaker 1: they're like on the surface. So we got to know
• 14:51
  Speaker 1: how the insides work if we want to figure out
• 14:53
  Speaker 1: how the outsides look. Yeah, because you know, it's still
• 14:55
  Speaker 1: kind of a big mystery in astrophysics and in science
• 14:59
  Speaker 1: is how do the Solar System form and out of
• 15:01
  Speaker 1: these planets specifically form in in an early version of
• 15:05
  Speaker 1: the solar system, right, and it's still kind of a
• 15:07
  Speaker 1: big question. We're still running simulations and trying to figure
• 15:10
  Speaker 1: that out. Yeah, we talked about on this podcast we
• 15:12
  Speaker 1: don't even really understand how our solar system came to be,
• 15:16
  Speaker 1: Like we run models about our solar system doesn't really
• 15:19
  Speaker 1: quite make sense, Like why is Mars so small? And
• 15:21
  Speaker 1: why do we have very few planets close to our
• 15:24
  Speaker 1: Sun whereas many other solar systems have lots and lots
• 15:27
  Speaker 1: of planets in between the distance between our Sun and Mercury.
• 15:30
  Speaker 1: So we want to know the answer to that question,
• 15:32
  Speaker 1: like what is the story of our solar system? For me,
• 15:35
  Speaker 1: it drives me crazy to think that there's an exciting,
• 15:37
  Speaker 1: traumatic story something that happened here and we just don't
• 15:40
  Speaker 1: know it. Maybe were coextruded by the great planet factoring
• 15:45
  Speaker 1: the sky, a new creation myth folks born here today
• 15:48
  Speaker 1: on the podcast, co extrusion sounds like a good novel name. Yeah,
• 15:53
  Speaker 1: And you know, there are folks who do that kind
• 15:55
  Speaker 1: of study, like look for other planets and other solar systems.
• 15:58
  Speaker 1: They look for exoplanets, and then there's a whole community
• 16:00
  Speaker 1: people who just study like the planets in our solar
• 16:03
  Speaker 1: system and what's in them. People who dedicate their entire
• 16:06
  Speaker 1: research careers to like this question what's inside Mars, And
• 16:10
  Speaker 1: you're saying that there might be parallels but the Earth
• 16:12
  Speaker 1: as well, Like knowing what happened to Mars might help
• 16:16
  Speaker 1: us understand what's happening here in Earth and let us
• 16:19
  Speaker 1: study things like earthquakes and what we can expect in
• 16:22
  Speaker 1: the future. Absolutely, you never want to just have any
• 16:25
  Speaker 1: equals one, right. You don't want to base all of
• 16:27
  Speaker 1: your conclusions about how planets work from one example. You
• 16:30
  Speaker 1: want to look at a bunch of them. You want
• 16:31
  Speaker 1: to population so you can get a sense for what's typical,
• 16:34
  Speaker 1: and you can also see the future, Like if Mars
• 16:37
  Speaker 1: is smaller and colder than Earth, then in some sense
• 16:40
  Speaker 1: it might be what the future of Earth looks like,
• 16:42
  Speaker 1: you know, in millions and billions of years. But it'd
• 16:45
  Speaker 1: be good to get an understanding of how these processes
• 16:47
  Speaker 1: work because we rely on the Earth to have these
• 16:49
  Speaker 1: layers in order to have our civilization and our society function.
• 16:53
  Speaker 1: So it would be good to know, like the factors
• 16:55
  Speaker 1: that control that, What are the forces at play? Are
• 16:57
  Speaker 1: things rising or sinking or cooling or eating or what's
• 17:00
  Speaker 1: going on inside. So absolutely we want to get a
• 17:03
  Speaker 1: better handle on the interior mechanisms of our planet. And
• 17:06
  Speaker 1: it's all right there, hidden under the surface, bubbling up
• 17:09
  Speaker 1: or maybe just chilling out. Let's get into whether or
• 17:11
  Speaker 1: not Mars has a solid or liquid core and whether
• 17:15
  Speaker 1: we'll ever know. But first let's take a quick we're
• 17:31
  Speaker 1: talking about whether Mars the planet, right, not the Mars bars,
• 17:34
  Speaker 1: because we know those have a newgat center, right, But
• 17:37
  Speaker 1: isnt a liquid or a solid? Oh no, another you
• 17:41
  Speaker 1: have a whole episode on strange matter from in candies.
• 17:45
  Speaker 1: Daniel vapes various candies. That's in my new podcast series,
• 17:49
  Speaker 1: one episode long. You just blew my mind vaping. What
• 17:53
  Speaker 1: does that even mean? Oh my goodness, how could it
• 17:55
  Speaker 1: be possible that nobody's ever tried that before, you know,
• 17:58
  Speaker 1: after raping other stuff, since somebody must have had that idea.
• 18:02
  Speaker 1: Oh man, I think you're in the run business, Daniel. Alright,
• 18:05
  Speaker 1: So we're trying to figure out whether Mars has a
• 18:07
  Speaker 1: solid or liquid core, not just for curiosity about what's
• 18:10
  Speaker 1: going on there, but I might tell about the history
• 18:13
  Speaker 1: of our planet and the whole Solar System. And so Daniel,
• 18:16
  Speaker 1: you actually went out there and talked to an expert
• 18:18
  Speaker 1: on this topic. Right, that's right. I called up a
• 18:21
  Speaker 1: colleague of mine, Katherine Johnson. She's at the University of
• 18:24
  Speaker 1: British Columbia, and I asked her why she was so
• 18:27
  Speaker 1: excited about this particular question. Here's what she had to say.
• 18:30
  Speaker 1: So then it's my pleasure to introduce to the program
• 18:32
  Speaker 1: professor Katherine Johnson. Catherine said hello to our listeners and
• 18:36
  Speaker 1: tell them a little bit about yourself. Hi. So it's
• 18:40
  Speaker 1: pressure to be here. And I'm a faculty member at
• 18:43
  Speaker 1: the University of British Columbia in Vancouver and also a
• 18:46
  Speaker 1: scientist at the Planetary Science Institute a Tucson and I
• 18:50
  Speaker 1: work in geophysics in uh sort of planetary science. So
• 18:54
  Speaker 1: I'm interested in understanding the interior state and evolution of
• 19:00
  Speaker 1: of the planets, moons, and asteroids in our Solar system.
• 19:04
  Speaker 1: And tell me why that's exciting for you. What is
• 19:06
  Speaker 1: it about the interior of Mars, for example, that makes
• 19:09
  Speaker 1: you curious, that makes you wonder what's going on inside there?
• 19:12
  Speaker 1: So you know, one of the reasons that I like
• 19:15
  Speaker 1: to think about other planets is really to try to
• 19:17
  Speaker 1: understand our own planet better. I think you know, for me,
• 19:20
  Speaker 1: that's one of the major motivations to try to understand
• 19:24
  Speaker 1: planets in our own solar system, especially in the inner
• 19:27
  Speaker 1: Solar system right where we have Mercury, Venus, the Earth, Mars,
• 19:31
  Speaker 1: our own Moon, and they're all completely different from each other,
• 19:35
  Speaker 1: even though they started in somewhat similar at least with
• 19:38
  Speaker 1: the exception of the Moon, started in somewhat similar ways.
• 19:41
  Speaker 1: And so a lot of this really has to do
• 19:44
  Speaker 1: with their interiors and how they are interiors of like
• 19:48
  Speaker 1: shaped their histories. All right, Thank you, Katherine. And so
• 19:53
  Speaker 1: you went and chatted with her about this topic, Yeah,
• 19:55
  Speaker 1: I did. We had a really fun conversation after all
• 19:57
  Speaker 1: about it. Learned a lot of gory details of how
• 20:00
  Speaker 1: the project works and the politics of getting her instrument
• 20:04
  Speaker 1: up and on Mars and how that all works. It
• 20:06
  Speaker 1: was a lot of fun. Thanks Catherine very much for
• 20:08
  Speaker 1: educating me about your research. She has an instrument on Mars.
• 20:11
  Speaker 1: She does exactly. She helped design and build this seizedmometer
• 20:16
  Speaker 1: that they have on Mars, which is one of the
• 20:17
  Speaker 1: ways they figure out what's inside. Interesting because that is
• 20:21
  Speaker 1: sort of a way they do it here on Earth. Right,
• 20:23
  Speaker 1: we haven't actually like dug a hole or a little
• 20:25
  Speaker 1: people to the center of the earth. We have just
• 20:28
  Speaker 1: models and kind of sound and sound wave detections on
• 20:31
  Speaker 1: the surface, right, that's right. We have dug in only
• 20:33
  Speaker 1: very shallow holes relatively speaking, into the earth, and so
• 20:37
  Speaker 1: we have not actually probed physically the center of the Earth.
• 20:41
  Speaker 1: But we do have a pretty good picture of what's
• 20:43
  Speaker 1: going on inside the earth because of earthquakes. Every time
• 20:46
  Speaker 1: there's an earthquake, it's like the earth rings sort of
• 20:49
  Speaker 1: like a bell, and the waves they don't just like
• 20:52
  Speaker 1: shake the outer crust, they propagate all the way through
• 20:55
  Speaker 1: the interior. And when waves cross a threshold, like when
• 20:58
  Speaker 1: you go from solid to liquid, or the quit to solid,
• 21:00
  Speaker 1: or one kind of metal or to another, you get reflections.
• 21:03
  Speaker 1: Just like when light hits a piece of glass, most
• 21:05
  Speaker 1: of it goes through, but some of it reflects. So
• 21:07
  Speaker 1: these reflections and the interior of the earth make for
• 21:10
  Speaker 1: really complicated patterns. But if you have a bunch of
• 21:13
  Speaker 1: seized momometers all over the earth that measure the shaking,
• 21:16
  Speaker 1: you can get a really nice picture of exactly how
• 21:19
  Speaker 1: this wave propagated through the earth. And then from that
• 21:21
  Speaker 1: you can back out like, oh, there must have been
• 21:23
  Speaker 1: a layer here, and it must have been a layer there,
• 21:25
  Speaker 1: and you can make really detailed measurements about the composition
• 21:28
  Speaker 1: and the density and the flow of those layers. And
• 21:31
  Speaker 1: so she has some instruments on Mars, and are the
• 21:33
  Speaker 1: earthquakes on Mars as she is, she can measure there
• 21:35
  Speaker 1: are no earthquakes on Mars. There are Mars quakes, Martian quakes. Yeah,
• 21:42
  Speaker 1: they actually only have one sized momometer on Mars, so
• 21:44
  Speaker 1: it's a little trickier, but we'll dig into it in
• 21:46
  Speaker 1: detail in a few minutes, all right. And I like
• 21:48
  Speaker 1: how she talked about how every planet is different and
• 21:51
  Speaker 1: how like the insights tell you a lot about your history.
• 21:55
  Speaker 1: I guess that's true for people to write like you
• 21:57
  Speaker 1: can look at my veins and be like, this guy
• 21:59
  Speaker 1: hit a lot of peanut butter. Unfortunately, sometimes our interiors
• 22:03
  Speaker 1: do reveal our history exactly, and every planet has a
• 22:06
  Speaker 1: very different story. And the thing that always surprises me
• 22:09
  Speaker 1: is to realize that these stories change with time. You know,
• 22:12
  Speaker 1: It's not like Venus has always looking the way it
• 22:14
  Speaker 1: does today and that Mars has always looked the way
• 22:16
  Speaker 1: it does today. You know, right now, the surface of
• 22:19
  Speaker 1: Mars is very cool and inactive. But scientists think that
• 22:22
  Speaker 1: Mars had volcanoes active on its surface up to maybe
• 22:26
  Speaker 1: like a million years ago, which is basically no time
• 22:29
  Speaker 1: at all in the billions of years history of Mars.
• 22:32
  Speaker 1: So like, this is an active story that's still developing.
• 22:35
  Speaker 1: We're in the middle of history. We are history is
• 22:38
  Speaker 1: being made exactly all right, Well, maybe it step us
• 22:41
  Speaker 1: through here. Why do we think Mars might have a
• 22:44
  Speaker 1: solid core? Like where did this idea first come from?
• 22:47
  Speaker 1: And why do we need to assume that? Well, you know,
• 22:49
  Speaker 1: we just didn't know for a long time. I think
• 22:51
  Speaker 1: the popular conception is that Mars has a solid core
• 22:54
  Speaker 1: just because it's smaller and colder. Right, Mars is really
• 22:58
  Speaker 1: weird and small. People might not realized. But it has
• 23:00
  Speaker 1: like a tenth of the mass of the Earth, so
• 23:03
  Speaker 1: it's really a much smaller chunk of stuff than the
• 23:06
  Speaker 1: Earth is. Well, I really a ten I knew it
• 23:08
  Speaker 1: was smaller, but I didn't know it's ten times smaller, lighter. Yeah,
• 23:11
  Speaker 1: it's you know, maybe ten but it's just like not
• 23:15
  Speaker 1: really that much stuff. And people think that it might
• 23:17
  Speaker 1: be Jupiter's fault, you know, Jupiter might have come into
• 23:20
  Speaker 1: the inner solar system earlier on, like millions and billions
• 23:23
  Speaker 1: of years ago, and sort of pushed away a lot
• 23:25
  Speaker 1: of the stuff that might have helped make Mars bigger.
• 23:28
  Speaker 1: That might be one reason why Mars is small. But that's,
• 23:31
  Speaker 1: you know, just a mystery. But in the end, Mars
• 23:33
  Speaker 1: is a smaller chunk of stuff, and a smaller chunk
• 23:35
  Speaker 1: of stuff doesn't have as much gravity, so it doesn't
• 23:38
  Speaker 1: have as much pressure and high temperature stuff and its interior,
• 23:41
  Speaker 1: and it cools faster. So there's this sense that Mars is,
• 23:44
  Speaker 1: like being a smaller rock, has a less chance to
• 23:46
  Speaker 1: have a molten core than Earth does. Like you know,
• 23:49
  Speaker 1: asteroids out there don't have molten corks. They're not big
• 23:52
  Speaker 1: enough to generate that pressure and temperate in their interiors. Oh,
• 23:55
  Speaker 1: I see, So that's where I guess you might first
• 23:57
  Speaker 1: assume that Mars has a solid core, and we also
• 24:01
  Speaker 1: know just have a magnetic field, right, I mean, I
• 24:04
  Speaker 1: guess if I said this, like they took a compass
• 24:06
  Speaker 1: to Mars and it didn't work. Yeah, there's lots of
• 24:08
  Speaker 1: satellites orbiting Mars looking for magnetic fields and they don't
• 24:11
  Speaker 1: have one. But if you look at some of the
• 24:13
  Speaker 1: rocks on Mars, you can see fossil evidence for a
• 24:16
  Speaker 1: magnetic field. That means that we know that Mars used
• 24:19
  Speaker 1: to have a magnetic field. So that sort of adds
• 24:22
  Speaker 1: to the narrative, like maybe Mars when it was young
• 24:24
  Speaker 1: and hot, literally had a flowing interior core that generated
• 24:29
  Speaker 1: this magnetic field. But it's gone now, and so maybe
• 24:32
  Speaker 1: that like locked up and there's no longer any motion
• 24:35
  Speaker 1: in the core. Yeah. I used to be a lot
• 24:36
  Speaker 1: more magnetic when I was younger, and otter too, but no,
• 24:40
  Speaker 1: I'm just cool. Yeah, back when you had a better
• 24:42
  Speaker 1: interior flow. Yeah, back when were his clogged with candy killings?
• 24:47
  Speaker 1: All right, So then where did this idea that it
• 24:48
  Speaker 1: could be liquid? And I mean, it seems pretty reasonable
• 24:51
  Speaker 1: for it to be solid and likely, but what makes
• 24:54
  Speaker 1: this thing it could have a liquid core? Well, you know,
• 24:56
  Speaker 1: we just don't know, And so one question is like,
• 24:59
  Speaker 1: maybe we think it has a solid core, but let's
• 25:01
  Speaker 1: go check. Remember a lot of the amazing discoveries we've
• 25:04
  Speaker 1: made in history come from just sort of checking off
• 25:07
  Speaker 1: things where we didn't expect to find anything interesting. Like
• 25:10
  Speaker 1: let's check to see how quickly galaxies rotate. Oh my, gosh,
• 25:13
  Speaker 1: they're rotating way too fast. That's how we discovered dark matter.
• 25:17
  Speaker 1: Let's check to see what happens when we shoot photons
• 25:19
  Speaker 1: at this metal that seems boring. Oh my gosh, we
• 25:22
  Speaker 1: discover quantum mechanics. So there's lots of wonderful opportunities to
• 25:25
  Speaker 1: discover things when you just sort of do basic checks.
• 25:28
  Speaker 1: So that's number one. I guess you don't want to
• 25:30
  Speaker 1: go around the university just assuming things right. You want
• 25:32
  Speaker 1: to actually make sure. Yeah, that's why we do experiments right,
• 25:35
  Speaker 1: because often the results are a surprise, and those are
• 25:38
  Speaker 1: the most delicious times in science, right when you get
• 25:41
  Speaker 1: a result that surprises you, that doesn't make sense, it
• 25:44
  Speaker 1: conflicts with your idea of the universe, and that's how
• 25:47
  Speaker 1: you learn, right, that's what science is. But then people
• 25:49
  Speaker 1: also realize that we didn't actually have conclusive evidence that
• 25:53
  Speaker 1: Mars had a solid core, that you could build a
• 25:55
  Speaker 1: model of Mars with a liquid core that was still
• 25:58
  Speaker 1: consistent with everything we saw and we knew about Mars.
• 26:01
  Speaker 1: But I guess maybe the question is could it be liquid?
• 26:03
  Speaker 1: I mean, if it doesn't have a magnetic field, wouldn't that,
• 26:06
  Speaker 1: you know, tell us that it has a solid core,
• 26:08
  Speaker 1: not necessarily, because the magnetic field actually requires two different things.
• 26:13
  Speaker 1: It requires some liquid, but it also requires flow, Like
• 26:16
  Speaker 1: that liquid has to be in motion. There needs to
• 26:19
  Speaker 1: be some sort of like circulation of that liquid. Because
• 26:22
  Speaker 1: remember the dynamo effect that gives you a magnetic field
• 26:24
  Speaker 1: doesn't just come from having liquid sitting around. It comes
• 26:27
  Speaker 1: from currents right ionized particles in motion. So it's possible
• 26:32
  Speaker 1: that Mars has a liquid, but that liquid isn't flowing
• 26:34
  Speaker 1: in the right way to give you a magnetic field. Oh,
• 26:37
  Speaker 1: I see. It could just be like liquid center just
• 26:40
  Speaker 1: sitting there. Yeah. Or you could have a liquid layer
• 26:42
  Speaker 1: between two other solid layers and it could just be
• 26:45
  Speaker 1: sort of like too thin to have the right kind
• 26:47
  Speaker 1: of rotating currents. Or it might just be the like
• 26:50
  Speaker 1: the heat difference between that liquid layer and the next
• 26:53
  Speaker 1: layer isn't great enough to get like the convection. You
• 26:56
  Speaker 1: need to have flow, don't. You also need like to
• 26:58
  Speaker 1: have special metals in that you know, liquid layer for
• 27:01
  Speaker 1: you to get the magnetic field, Like is an iron
• 27:04
  Speaker 1: in our molten core a big part of why we
• 27:06
  Speaker 1: have a magnetic field, yeah, exactly, And so you need
• 27:08
  Speaker 1: to be open to those possibilities. We do think, based
• 27:11
  Speaker 1: on density estimates, that there is a big iron nickel
• 27:14
  Speaker 1: core to Mars. So the question is really is some
• 27:17
  Speaker 1: of it liquid or is it all solid? But you're right,
• 27:19
  Speaker 1: you need some metal. If you had just like a
• 27:21
  Speaker 1: core of you know, ceramic or whatever, something that was
• 27:24
  Speaker 1: totally insulating, then you couldn't get a magnetic feel from
• 27:27
  Speaker 1: that has to conduct electricity. So it could have a
• 27:29
  Speaker 1: liquid core. Mars could look sort of small and cold,
• 27:32
  Speaker 1: but it could be inside you know, frosthing or seating
• 27:36
  Speaker 1: or you know, have a soft, squishy center or layer. Absolutely,
• 27:40
  Speaker 1: and that's a really exciting moment in science when you realize,
• 27:43
  Speaker 1: hold on a second, you know, everything we thought was
• 27:45
  Speaker 1: true could be different. This other theories actually totally consistent
• 27:50
  Speaker 1: with everything we know. And that's exciting because it gives
• 27:53
  Speaker 1: you like two possibilities to explore. It gives you an
• 27:55
  Speaker 1: opportunity to be surprised. Then, I guess the big question
• 27:58
  Speaker 1: then is if it could be liquid inside, how could
• 28:00
  Speaker 1: we ever know? I mean, we're sitting here, thousands and
• 28:03
  Speaker 1: thousands of miles away, sending small robots one at a time.
• 28:06
  Speaker 1: How are we going to find out what's inside? Daniel. Yeah, Well,
• 28:09
  Speaker 1: it turns out we have lots of different ways to
• 28:11
  Speaker 1: prove this question, some of which we can do without
• 28:14
  Speaker 1: actually going to the surface of Mars. One of them
• 28:16
  Speaker 1: is really cool is that they measure basically how squishy
• 28:19
  Speaker 1: Mars is. They have a satellite which rotates around Mars
• 28:23
  Speaker 1: and basically it's imaging its surface and making a picture
• 28:26
  Speaker 1: of like the shape of Mars, how spherical is it?
• 28:29
  Speaker 1: Because Mars, like everything else, is getting squeezed by the Sun.
• 28:32
  Speaker 1: Remember we talked about tidal forces, how the gravitational force
• 28:36
  Speaker 1: on an object is stronger on the side that's closer
• 28:38
  Speaker 1: to the Sun than further from the Sun. Or for example,
• 28:41
  Speaker 1: this is why Jupiter's moon Io has hot interior, because
• 28:44
  Speaker 1: it's getting squeezed by these tidal forces. Well, Mars is
• 28:48
  Speaker 1: getting squeezed by the Sun, and it would get squeezed
• 28:51
  Speaker 1: differently if it had a liquid center or some liquid
• 28:54
  Speaker 1: layers than if it was totally solid. Basically would get
• 28:57
  Speaker 1: squished more So by measuring really precisely the shape of
• 29:00
  Speaker 1: Mars as it spins and goes around the Sun, you
• 29:02
  Speaker 1: can get a sense for whether or not it has
• 29:04
  Speaker 1: a liquid layer. You mean, like as it goes around
• 29:06
  Speaker 1: the Sun or as it spins around its axis. Yeah,
• 29:09
  Speaker 1: basically the important thing is which side of it is
• 29:11
  Speaker 1: facing the Sun, because that's the part that's getting sort
• 29:14
  Speaker 1: of pulled towards the Sun really, and as it spins
• 29:17
  Speaker 1: and as it moves around the Sun, a different part
• 29:19
  Speaker 1: of it is facing the Sun, and so it's getting squeezed.
• 29:22
  Speaker 1: So if it was a solid rock, then it wouldn't
• 29:25
  Speaker 1: get really deformed by the gravity of the Sun much
• 29:27
  Speaker 1: as it goes around. But if it was liquid inside,
• 29:30
  Speaker 1: it might you know, kind of wish, kind of like
• 29:32
  Speaker 1: a drop of water in space. Yeah, exactly, That's exactly
• 29:35
  Speaker 1: what happens, and so we can measure that, and that
• 29:38
  Speaker 1: gives us some clue about whether or not there's a
• 29:40
  Speaker 1: liquid or solid layer inside Mars. All right, well, let's
• 29:43
  Speaker 1: get into some of the other ways we can tell
• 29:45
  Speaker 1: if Mars is soft and squishy on the inside or
• 29:48
  Speaker 1: if it's hardcore. So let's get into that. But first
• 29:50
  Speaker 1: let's take another quick break. Alright, is Mars hardcore or
• 30:07
  Speaker 1: is it just a big squishy or person inside. Now,
• 30:10
  Speaker 1: we talked about how we can tell, and we can
• 30:12
  Speaker 1: tell sometimes by the tidal effects of the Sun on
• 30:16
  Speaker 1: its shape. So that's one way, and that's happening to
• 30:19
  Speaker 1: us here on Earth. To Daniel, our Earth is getting squished. Yeah,
• 30:22
  Speaker 1: our Earth gets squished by the Sun and by the moon. Right,
• 30:25
  Speaker 1: the reason that we have tides in our ocean is
• 30:27
  Speaker 1: that the Moon is having exactly that same effect on
• 30:30
  Speaker 1: our liquid exterior, and then the Sun has that effect
• 30:34
  Speaker 1: on our liquid interior because it squeezes the whole planet.
• 30:37
  Speaker 1: All right, Well, what are some of the other ways
• 30:39
  Speaker 1: we could tell if Mars is soft or our inside.
• 30:43
  Speaker 1: Another way they do it is by measuring it's wobble.
• 30:46
  Speaker 1: So Mars is spinning and it's going around the Sun,
• 30:48
  Speaker 1: and they measure its orbit very very precisely. And something
• 30:51
  Speaker 1: with a liquid center will spin a little bit differently
• 30:54
  Speaker 1: than something with a solid center, because the liquid center,
• 30:57
  Speaker 1: for example, might not be keeping up with the rest
• 31:00
  Speaker 1: of the object, right, it might be flowing at a
• 31:01
  Speaker 1: different rate, and that's will affect how Mars sort of
• 31:04
  Speaker 1: wobbles as it goes around the Sun and changes its orbit.
• 31:08
  Speaker 1: Really because of like conservation of angular momentum, or is
• 31:13
  Speaker 1: it just like you know, like moving around a water
• 31:16
  Speaker 1: bottle with water in it. It just creates a lot
• 31:18
  Speaker 1: of kind of inner forces that kind of throw you off. Yeah. Well,
• 31:22
  Speaker 1: there is definitely a different moment of inertia for an
• 31:24
  Speaker 1: object that has liquid inside of it because the distributed differently,
• 31:28
  Speaker 1: like the density is different, right, So you can get
• 31:30
  Speaker 1: a sense for the interior density. But then also, as
• 31:33
  Speaker 1: you say, you're gonna get like flows and it's not
• 31:35
  Speaker 1: necessarily going to catch up to the rest of Mars.
• 31:38
  Speaker 1: And so you can tell sort of like you know,
• 31:40
  Speaker 1: the difference between having a liquid and solid based on
• 31:42
  Speaker 1: how sort of the angle of Mars spin changes as
• 31:46
  Speaker 1: it goes around it. Think of it's sort of like
• 31:47
  Speaker 1: a top. You know, a top that has a liquid
• 31:49
  Speaker 1: center will spin differently than the top that doesn't have
• 31:52
  Speaker 1: a liquid center. Right, Well, a top of the liquid
• 31:54
  Speaker 1: tender would slow down faster, wouldn't it. It depends on
• 31:57
  Speaker 1: if the liquid is initially spinning. I guess. So that
• 32:00
  Speaker 1: another way we can tell we can very carefully kind
• 32:02
  Speaker 1: of study the orbit of Mars. Yeah, but then the
• 32:05
  Speaker 1: most precise way, of course is to get down to
• 32:07
  Speaker 1: the surface and actually measure Mars quakes and use those
• 32:11
  Speaker 1: to get an internal picture of what's going on inside Mars. Oh,
• 32:14
  Speaker 1: I see, like get onto Mars surface and measure how
• 32:18
  Speaker 1: you know, sound ways to travel through the planet precisely.
• 32:22
  Speaker 1: And they did this originally on the Viking Landers. They
• 32:25
  Speaker 1: actually had seized moometers on the first two Viking Landers,
• 32:29
  Speaker 1: but it didn't really work like one of them, it
• 32:31
  Speaker 1: didn't deploy, so it didn't get onto the surface, and
• 32:34
  Speaker 1: the other one only ever heard one Mars quake, but
• 32:38
  Speaker 1: it was before it was actually touching the surface, and
• 32:41
  Speaker 1: so it was this very sort of controversial event in
• 32:43
  Speaker 1: planetary science community. Had Viking heard of Mars quake or not,
• 32:48
  Speaker 1: and so before inside landed on Mars fairly recently, nobody
• 32:52
  Speaker 1: knew if there actually were Mars quakes or if it
• 32:55
  Speaker 1: was just totally quiet thing. I guess, well, maybe first
• 32:58
  Speaker 1: of all, let's take a step back and maybe mentioned
• 33:00
  Speaker 1: briefly how you can use sound waves to tell what
• 33:02
  Speaker 1: the core looks like like the sound waves traveled differently
• 33:05
  Speaker 1: if there was liquid or solid. Yeah, just like we
• 33:08
  Speaker 1: do for the Earth, as we talked about earlier. If
• 33:10
  Speaker 1: there are Mars quakes, then they generate these compression waves,
• 33:13
  Speaker 1: and those compression waves will bounce off of interior layers,
• 33:16
  Speaker 1: and so if there's a interface between the layers, like
• 33:19
  Speaker 1: a solid mantle and then a liquid layer. Then you'll
• 33:22
  Speaker 1: have the sound waves bounce off differently than it's just
• 33:25
  Speaker 1: all solid, just like light going through glass or hitting water.
• 33:28
  Speaker 1: When you transfer from one medium to another or from
• 33:31
  Speaker 1: one density to another, you're gonna get all sorts of
• 33:33
  Speaker 1: complicated reflections. And if you measure the sound waves on
• 33:36
  Speaker 1: the surface, then you can get a picture of that.
• 33:38
  Speaker 1: It can give you a map of the interior of
• 33:40
  Speaker 1: the planet I see, and then from the density map
• 33:43
  Speaker 1: you can maybe infer like, oh, this part is less dense,
• 33:46
  Speaker 1: it must be liquid. But also those transition points are
• 33:49
  Speaker 1: really important. You can tell where the transition points are
• 33:52
  Speaker 1: by telling when the reflection happened in exactly the direction
• 33:56
  Speaker 1: that the wave wind. And we actually have confirmation that
• 33:59
  Speaker 1: there are Mars quakes, like we've seen them or felt them,
• 34:02
  Speaker 1: or do we know for sure? Yeah, we actually do
• 34:05
  Speaker 1: have now. So the inside lander that's sitting on Mars,
• 34:08
  Speaker 1: it has the seized momometer on it. And so the
• 34:11
  Speaker 1: lander landed and then put out this cute little bubble
• 34:14
  Speaker 1: which sits on the surface of Mars, and it's shielded
• 34:16
  Speaker 1: from the sun and from the wind, and it just
• 34:18
  Speaker 1: listens to the surface of Mars. So before they landed,
• 34:21
  Speaker 1: they had all these theories about how you might get
• 34:24
  Speaker 1: Mars quakes even without any tectonic activity. Right, there's no
• 34:28
  Speaker 1: like plates on Mars. You don't have like earthquakes on
• 34:31
  Speaker 1: Mars the same way you have on Earth because you
• 34:33
  Speaker 1: don't have tectonic activity. But they thought that you would
• 34:36
  Speaker 1: still have little Mars quakes. So they landed this thing
• 34:39
  Speaker 1: on Mars and they saw like four hundred and fifty
• 34:42
  Speaker 1: Mars quakes in two thousand nineteen. Wait, what four hundred
• 34:47
  Speaker 1: Mars quakes a year? Yeah, so more than one every day.
• 34:51
  Speaker 1: And these are pretty small. Little quakes are like, you know,
• 34:53
  Speaker 1: things that the sizedmometer could pick up but you wouldn't
• 34:56
  Speaker 1: necessarily notice. Could it be the Mars inside their caves
• 34:59
  Speaker 1: kind partying or something jumping up and down. It's actually
• 35:03
  Speaker 1: really fascinating. In order to understand whether they could be
• 35:05
  Speaker 1: quakes on Mars without tectonic activity, right, without these tectonic
• 35:09
  Speaker 1: plates smashing into each other, they look to see if
• 35:11
  Speaker 1: there are earthquakes on Earth far away from the plate boundaries,
• 35:16
  Speaker 1: and it turns out that there are, So you can
• 35:18
  Speaker 1: get earthquakes even where you don't have plates that can
• 35:21
  Speaker 1: come from like the sun heating up big slabs of
• 35:23
  Speaker 1: rock which then expand, or things happening underneath that affect
• 35:27
  Speaker 1: you know, how the crust is moving. And so from
• 35:31
  Speaker 1: those models, they expected there to be a bunch of
• 35:33
  Speaker 1: Mars quakes, and then they put this thing on Mars
• 35:35
  Speaker 1: and they actually see these quakes. Interesting, like, even if
• 35:38
  Speaker 1: there are no liquid core, and there are in any
• 35:40
  Speaker 1: like big giant plates of rock floating and crashing into
• 35:44
  Speaker 1: each other, you can still get earthquakes just from a
• 35:46
  Speaker 1: rock just sitting there getting keated out by the sun. Yeah,
• 35:49
  Speaker 1: and that's not something that we understand very very well,
• 35:52
  Speaker 1: and so it's something they're curious about. They were really
• 35:54
  Speaker 1: curious when they landed this thing, like what we see
• 35:56
  Speaker 1: with the level of quakes we expected, or where they
• 35:58
  Speaker 1: be a lot more than we expected, will be a
• 36:00
  Speaker 1: lot quieter than we expected. They had some pretty good arguments,
• 36:03
  Speaker 1: but they just weren't sure. You know. That's why we
• 36:06
  Speaker 1: go explore the Solar system. And so we measured four
• 36:08
  Speaker 1: and fifty Mars quakes in and then twenty they stopped
• 36:12
  Speaker 1: because of the pandemic. Also, No, that's just the latest
• 36:16
  Speaker 1: data that they've released, so that's the latest result. But
• 36:18
  Speaker 1: you know, they're still analyzing data. This is an active
• 36:20
  Speaker 1: area research. They're still collecting data, and they're still waiting
• 36:24
  Speaker 1: for a really big quake. So far, they've seen sort
• 36:27
  Speaker 1: of a lot of small quakes, and I think they're
• 36:29
  Speaker 1: a little bit disappointed. They were hoping for like a
• 36:31
  Speaker 1: bunch of big ones, because the big ones are the
• 36:33
  Speaker 1: ones that carry a lot of energy and really help
• 36:36
  Speaker 1: them see the interior. With the smaller quakes, it doesn't
• 36:39
  Speaker 1: penetrate as deeply, so you can't really tell what's going on.
• 36:42
  Speaker 1: So they're sort of hanging out waiting to get lucky.
• 36:44
  Speaker 1: So they have detected Mars quakes, but there aren't big
• 36:47
  Speaker 1: enough for them to sort of be able to see
• 36:49
  Speaker 1: much about the inter core. They're not as big as
• 36:52
  Speaker 1: they hoped, but you know, they are clever scientists, and
• 36:55
  Speaker 1: so they've developed fancy new ideas for how to use
• 36:58
  Speaker 1: these to see the interior here anyway, and it's not
• 37:01
  Speaker 1: as powerful as they would have hoped until they get
• 37:04
  Speaker 1: like a really big one in all of Mars rings
• 37:06
  Speaker 1: like a bell. But they have been able to get
• 37:08
  Speaker 1: a pretty good picture for what's going on all right, well,
• 37:11
  Speaker 1: then that's out there on Mars, and Katherine Johnson is
• 37:15
  Speaker 1: one of the scientists on it. So what did she
• 37:17
  Speaker 1: say that we've found so far? So I asked her
• 37:19
  Speaker 1: to give me the insight on Mars and tell me
• 37:22
  Speaker 1: what's going on in the interior. And here's what she
• 37:24
  Speaker 1: had to say. So, we've had a good idea for
• 37:26
  Speaker 1: quite a while now a decade or so, that the
• 37:30
  Speaker 1: deepest interior of Mars is at least partly fluid, but
• 37:33
  Speaker 1: we haven't been able to confirm it with seismology, and
• 37:37
  Speaker 1: that's something that we're hoping to do with the Insight
• 37:39
  Speaker 1: mission that's currently on Mars. And the other thing that
• 37:42
  Speaker 1: we really haven't known is how big it's core is.
• 37:46
  Speaker 1: This is really important because we don't know exactly how
• 37:49
  Speaker 1: big it is. The trade off is it could be
• 37:51
  Speaker 1: smaller and pure metal or a bit bigger with some
• 37:54
  Speaker 1: light stuff mixed in with it. So it seems like
• 37:58
  Speaker 1: Mars does have liquid in its core. Really they can tell, Yeah,
• 38:02
  Speaker 1: it's at least partly fluid. That's what she said. And
• 38:05
  Speaker 1: all these different methods that we've been using, the Wibble method,
• 38:08
  Speaker 1: the Wobble method, and these seismic methods all sort of
• 38:12
  Speaker 1: tell the same story that there is some liquid in
• 38:15
  Speaker 1: the interior of Mars, interesting like at the core or
• 38:18
  Speaker 1: as a layer, probably as a layer on the outer core,
• 38:21
  Speaker 1: just like with the Earth. You know, in the Earth,
• 38:23
  Speaker 1: as you go into the Earth, you have the mantle
• 38:25
  Speaker 1: and then you have sort of an outer core and
• 38:27
  Speaker 1: inter core, and there you have like increasing temperature and pressure.
• 38:31
  Speaker 1: At first, temperature winds and things are like hot and melty,
• 38:34
  Speaker 1: and then as you get to the very center, pressure winds.
• 38:37
  Speaker 1: Even though things are still really hot, pressure takes over
• 38:39
  Speaker 1: and you have a solid core. So they think that's
• 38:41
  Speaker 1: probably what's happening on Mars. Also, you have this core
• 38:44
  Speaker 1: that's like eight kilometers and radius and the outer layers
• 38:48
  Speaker 1: of it probably liquid, so they feel pretty confident. Then
• 38:51
  Speaker 1: they know the answer. So all of our listeners were,
• 38:54
  Speaker 1: how wrong, or most of them were, as I would
• 38:57
  Speaker 1: have been, But that's pretty surprising. So they found that
• 39:00
  Speaker 1: Mars does have a liquid center, Yeah, exactly. Mars is
• 39:03
  Speaker 1: still hot and young, and I was surprised as well.
• 39:06
  Speaker 1: You know, I also expected Mars to be solid because
• 39:08
  Speaker 1: it seems cold and it's small, and I expected things
• 39:11
  Speaker 1: will have cooled off and for all the reasons we
• 39:13
  Speaker 1: gave before, it seemed like a reasonable guest, but you
• 39:15
  Speaker 1: never know until you actually go out there and measure it.
• 39:18
  Speaker 1: There are surprises out there waiting for us, and so
• 39:20
  Speaker 1: we are still learning a lot about how planets form
• 39:23
  Speaker 1: and how they develop into their middle age. Can you
• 39:26
  Speaker 1: still call it lava or magma or would it be
• 39:29
  Speaker 1: like marthma. I'm not sure what the name of it
• 39:31
  Speaker 1: would be, but this is stuff much much deeper than
• 39:34
  Speaker 1: the outer layers, right, Magma is actually part of the
• 39:36
  Speaker 1: crust that's become liquid because it's become really hot. We're
• 39:39
  Speaker 1: talking about stuff that's below the crust, below the mantle,
• 39:43
  Speaker 1: down into the core itself, like the real interior Mars.
• 39:46
  Speaker 1: This other question of like is there magma still on
• 39:49
  Speaker 1: Mars is another fascinating question because vulcanism on Mars seems
• 39:53
  Speaker 1: to have ended fairly recently, so it could be that
• 39:56
  Speaker 1: inside the crust of Mars there is still some sort
• 39:59
  Speaker 1: of hot mac interesting. That's cool. Maybe when we get
• 40:02
  Speaker 1: there we could use that for energy. Is that possible, Yeah, absolutely,
• 40:06
  Speaker 1: it's possible. You know, I guess it wouldn't be called
• 40:08
  Speaker 1: geo thermal energy and be called like mart show thermal energy, yeah,
• 40:15
  Speaker 1: mio thermal energy. But Mars has a thicker crust we
• 40:19
  Speaker 1: think than the Earth does. We think the crust is
• 40:21
  Speaker 1: like fifty to a hundred kilometers thick, so it's probably
• 40:24
  Speaker 1: colder and thicker. So it might be harder to find
• 40:26
  Speaker 1: a spot where there's still like you know, active magma.
• 40:29
  Speaker 1: We don't even know if there is still. But you know,
• 40:31
  Speaker 1: Mars had is like volcanic history for billions of years,
• 40:34
  Speaker 1: which seems to have ended kind of recently, so it
• 40:37
  Speaker 1: would be a surprise if there was totally cold and
• 40:40
  Speaker 1: quiet in the interior in terms of the crust. So
• 40:42
  Speaker 1: it's just another flavor of peanut butter, maybe crusty, smooth,
• 40:46
  Speaker 1: crunchy and crusty. Mars is very multifacet that it is
• 40:50
  Speaker 1: not just two layers, man, There are layers and layers
• 40:52
  Speaker 1: and layers. Mars was co co co co extruded. All right,
• 40:55
  Speaker 1: Well that's a pretty surprising answer, and thank you to
• 40:58
  Speaker 1: Katherine Johnson for helping us out. And it just goes
• 41:00
  Speaker 1: to show you how many surprises are out there waiting
• 41:03
  Speaker 1: in our own backyard or in our neighbor's backyard, and
• 41:06
  Speaker 1: you just have to go out there and check, or
• 41:08
  Speaker 1: at least, you know, spent a few billion dollars building
• 41:11
  Speaker 1: a little robot doesn't for you? Yeah, exactly, build a
• 41:14
  Speaker 1: big robot and use it to investigate your neighbor's backyard.
• 41:17
  Speaker 1: See how that goes, See how that works out. You
• 41:19
  Speaker 1: might call the solar system police on you use it
• 41:22
  Speaker 1: to steal their peanut Butterfield pretzels or their vapen so
• 41:25
  Speaker 1: you can do some experiments at home. All right, Well,
• 41:28
  Speaker 1: we hope you enjoyed then and came away thinking that
• 41:31
  Speaker 1: maybe the even our own backyard, It's not what it
• 41:34
  Speaker 1: seems sometimes, so keep its gloring, keep asking questions, and
• 41:37
  Speaker 1: thanks for tuning in. See you next time. Thanks for listening,
• 41:47
  Speaker 1: and remember that Daniel and Jorge Explain the Universe is
• 41:50
  Speaker 1: a production of I Heart Radio. For more podcast from
• 41:53
  Speaker 1: my Heart Radio, visit the i heart Radio app, Apple Podcasts,
• 41:57
  Speaker 1: or wherever you listen to your favorite show. This