Speaker 1: Hey, please take a second and leave us a review
Speaker 1: on Apple Podcasts, Spotify, or wherever you listen to the podcast.
Speaker 1: Thanks a lot. Hey, Welcome to Science Stuff, the production
Speaker 1: of iHeartRadio. I'm poor, Hey Champ, and today we are
Speaker 1: going to the Moon. You might think you know the moon,
Speaker 1: but actually it is full of scientific mysteries. We're going
Speaker 1: to be talking about where the moon came from, what
Speaker 1: it's made out of, and what it can tell us
Speaker 1: about how life started on Earth. So get ready to
Speaker 1: go over the moon as we tackle the unanswered questions
Speaker 1: about our mysterious moon enjoying. Hey everyone, Today we're talking
Speaker 1: to doctor Matt Siegler. Doctor Ziegler is a planetary scientist
Speaker 1: at the University of Hawaii who works on several missions
Speaker 1: for NASA and the European Space Agency, including did You
Speaker 1: Are the miss mission to put astronauts back on the Moon.
Speaker 1: He's going to answer three questions for us. Number one,
Speaker 1: where did the moon come from? As it turns out,
Speaker 1: it's really unusual for us to have such a big moon.
Speaker 1: Number two, why does the moon always faces the same way?
Speaker 1: Wasn't always the case? And number three, why are we
Speaker 1: going back to the moon? It turns out scientists have
Speaker 1: identified a deep mystery about the Moon that might have
Speaker 1: huge implications for space travel and our search for extraterrest
Speaker 1: deal life. So here's my conversation with doctor Matt Siegler. Well,
Speaker 1: thank you doctor Siegler for joining us again.
Speaker 2: Okay, welcome.
Speaker 1: The last time we talked it was New Year's and
Speaker 1: we talked about how the Earth goes around the Sun.
Speaker 1: And now we're getting close to the lunar New Year,
Speaker 1: so I thought it would be interesting to talk about
Speaker 1: the moon.
Speaker 2: Okay, that's actually my specialties. That's great to talk about
Speaker 2: something that I know.
Speaker 1: Are you saying you're a lunatic?
Speaker 2: Yes, yeah, we're proud to call ourselves lunatics.
Speaker 1: Well, in what ways is our moon unusual in the
Speaker 1: Solar System?
Speaker 2: Okay? Well, the weirdest thing about our moon is how
Speaker 2: big it is compared to Earth. There are a couple
Speaker 2: of moons out there, some of Saturn's moons and a
Speaker 2: couple of Jupiter's moons that are about the size of
Speaker 2: our moon or even a little bigger. But those planets
Speaker 2: are huge, right, you could fit I think it's thirteen
Speaker 2: hundred earths inside of Jupiter, right, Wow, huh. And so
Speaker 2: their biggest moon is a very small moon compared to
Speaker 2: the size of its body, meaning.
Speaker 1: Like if Jupiter had a moon that's proportionately the same
Speaker 1: size as our moon, it would be like the size
Speaker 1: of Saturn or something.
Speaker 2: Yeah, it would be like the size of Neptune at least.
Speaker 2: So yeah, And the only other planet that, if you
Speaker 2: want to call it a planet that has a similar
Speaker 2: is Pluto.
Speaker 3: Right.
Speaker 1: Oh, no, no, we don't talk about Pluto in this podcast.
Speaker 2: You don't talk about about plu.
Speaker 1: We don't know.
Speaker 2: Pluto has a moon that's about a tenth of its
Speaker 2: size or something like that.
Speaker 1: But plut itself is very small, smaller than us, right,
Speaker 1: smaller than our moon kind of.
Speaker 2: Yeah, Pluto is around it could fit inside the continental US.
Speaker 2: So it's a pretty small body.
Speaker 1: Okay, Oh, that's a very polite way to say it.
Speaker 1: It's a small body. Yes, yes, small body.
Speaker 2: So that's the weirdest thing about our moon is how
Speaker 2: big it is compared to us.
Speaker 1: So that's the first mystery about the moon. Why is
Speaker 1: it so big? None of the other planets have a
Speaker 1: moon this big.
Speaker 3: Why is that?
Speaker 1: Well, as it turns out, Charles Darwin's Sun George Darwin
Speaker 1: had a theory about that.
Speaker 2: So that's actually a funny part of the history is
Speaker 2: our moon is relatively large. It's about the size of
Speaker 2: the Pacific Ocean basin, and so Charles Darwin's son, I
Speaker 2: believe George Darwin first theorized that the Moon might have
Speaker 2: been created from the Earth by being spit out of
Speaker 2: the Pacific Ocean basin, and the Pacific Ocean was the
Speaker 2: hole left behind. So that's a good way to remember
Speaker 2: the size of the Moon is roughly the size of
Speaker 2: the Pacific Ocean, because that was one of the first thoughts, Well, well,
Speaker 2: we have a hole here on Earth that's about the
Speaker 2: size of the moon.
Speaker 1: Yeah, maybe that's came It was like a giant pimple
Speaker 1: that just popped off the Earth. That was the theory, yes, yes,
Speaker 1: or the Darwin giant pimple theory. Yeah, George Darwin didn't
Speaker 1: quite get thinks is right as this famous dad Charles Darwin,
Speaker 1: or did he?
Speaker 2: Now we kind of think it's crazy, but really how
Speaker 2: we think the moon formed now was not all that different.
Speaker 2: It's just that that spitting out happened in a big
Speaker 2: event when something the size of Mars or so collided
Speaker 2: into the early Earth and caused that event where material
Speaker 2: got spit out and formed the moon.
Speaker 1: That's a wild theory, Like we have a moon that's
Speaker 1: like gray white, but we think it happened because some
Speaker 1: giant mini planet crashed into the original Earth.
Speaker 2: Yeah, so that's the idea is the original early Solar
Speaker 2: system was full of things that were flying all around,
Speaker 2: and some of them collided into each other, and the
Speaker 2: debris of that collision formed something kind of like a
Speaker 2: ring of Saturn around the Earth. Right, it was a ring,
Speaker 2: and then that coalesced together and became the Moon.
Speaker 1: So like our Earth is a mix of those two
Speaker 1: original planets, and the Moon is a mix of those
Speaker 1: two original planets.
Speaker 2: Exactly.
Speaker 1: Yes, scientists think the way the moon form was that
Speaker 1: a planet the size of Mars crashed into a pre
Speaker 1: Earth planet about four and a half billion years ago,
Speaker 1: and then the debris from that crash clumped together and
Speaker 1: formed the Moon. But here's a big question, how do
Speaker 1: we know that? What makes us think that's how the
Speaker 1: Moon formed. Well, it turns out this idea started when
Speaker 1: we first walked on the Moon.
Speaker 2: And this explains basically what we found when the Apollo
Speaker 2: samples were returned in the nineteen sixties and seventies. Huh,
Speaker 2: was that a lot of the isotopes of atoms were
Speaker 2: incredibly similar between the Earth and the Moon.
Speaker 1: What do you mean isotopes?
Speaker 2: So normally an atom will have the same number of
Speaker 2: protons and neutrons, and so an isotope is one that
Speaker 2: has different numbers of neutrons.
Speaker 1: Okay than the normal one I see. And so it's
Speaker 1: where for the isotopes on Earth to match the ones
Speaker 1: on the Moon.
Speaker 2: Yeah, So that turns out to be one of the
Speaker 2: key identifiers of where something formed in the early Solar
Speaker 2: System is it's the isotopes of its different atoms, and
Speaker 2: particularly good one is oxygen.
Speaker 1: It turns out you can tell exactly where in the
Speaker 1: Solar System a piece of rock comes from by its isotopes.
Speaker 1: Like a piece of rock has more of one kind
Speaker 1: of oxygen or carbon, you can tell it came from
Speaker 1: close to the Sun, or near Jupiter, or way out
Speaker 1: at the edges of the Solar system.
Speaker 2: So we think the whole Solar System essentially was a
Speaker 2: big cloud of gas and dust that was leftover from
Speaker 2: some other star that exploded, right, huh, And that cloud
Speaker 2: kind of collust around the early Sun, and then when
Speaker 2: that Sun turned on, you know, very early in the
Speaker 2: Solar system four point six billion years ago, it heated
Speaker 2: that cloud and basically boiled off different isotope ratios as
Speaker 2: you went different distance from the Sun. And then when
Speaker 2: the planets formed, out of those different isotopic ratios as
Speaker 2: a function of distance away from the Sun, they seem
Speaker 2: to have checked those isotopes permanently after that.
Speaker 1: Interesting, it's like the rocks have a tag that says
Speaker 1: where in the Solar System formed.
Speaker 2: Yeah, so when we see a meteorite that we have
Speaker 2: identified has come from Mars or a meteorite from the
Speaker 2: Asteroid belt, these will have different oxygen isotope ratios than
Speaker 2: the Earth. But the Moon has almost the same as
Speaker 2: the Earth, like too incredible precision, such that the only
Speaker 2: way that we can explain it was that they essentially
Speaker 2: formed together as a single body. Okay, and so the
Speaker 2: Earth and the Moon are incredibly similar, and it could
Speaker 2: be that it's just kind of telling us they formed
Speaker 2: at the exact same distance from the Sun. But the
Speaker 2: precision in which they match seems to only be explained
Speaker 2: if they really formed together in this idea of the
Speaker 2: giant impact or simple.
Speaker 1: I see the match is too good. It's just too
Speaker 1: identical to the Earth.
Speaker 2: Yeah, Like these are identical twins, you know, they had
Speaker 2: to be born from the same mother.
Speaker 1: I see the DNA says their siblings, same mother, same father.
Speaker 2: Okay, And so there were lots of theory going around,
Speaker 2: and as far as I understand it, there was some
Speaker 2: international meeting about this in the early nineteen eighties and
Speaker 2: there was a lot of debate, and then out came
Speaker 2: the giant impact as the winner, and it's kind of
Speaker 2: been the standard since then.
Speaker 1: Interesting. So it's not like we have some smoking gun
Speaker 1: that says that this is what happened, or that there
Speaker 1: was a camera or somebody saw this happened. It's like, well,
Speaker 1: we can't think of anything else, and this is the
Speaker 1: only thing that we have left.
Speaker 2: Yeah, and everything that we find out knew about the
Speaker 2: Moon seems to fit with the theory of the giant impact.
Speaker 2: Like what like one of the things we found out
Speaker 2: was from seismometers on the Moon. We've been able to
Speaker 2: figure out that the Moon has a fairly small iron core, right,
Speaker 2: and the Earth actually has a really big iron core
Speaker 2: for its size. And so where did this extra iron
Speaker 2: on the Earth come from and the lack of iron
Speaker 2: on the Moon come from. Well, it may have been
Speaker 2: that you had this big impact and then more the
Speaker 2: iron went into the big object than into the small
Speaker 2: on it.
Speaker 3: Oh.
Speaker 1: I see, what do you think the junior Darwin would
Speaker 1: feel now that you've disproven his theory and not lived
Speaker 1: up to the greatness of the Darwin name.
Speaker 2: I don't know. I think scientists by nature like to
Speaker 2: know the truth or the facts about the matter, and
Speaker 2: if an idea that we clung to turns out to
Speaker 2: be wrong, we should kind of give it up.
Speaker 3: Yeah.
Speaker 2: So I think that was a strong philosophy of science
Speaker 2: then and it still is today.
Speaker 1: Nice all right, when we come back, we're going to
Speaker 1: tackle the second big mystery about the moon, which is
Speaker 1: why is the Moon always facing us the same way?
Speaker 1: In case you haven't noticed, every time you look at
Speaker 1: the Moon, no matter where you are on the planet
Speaker 1: or what time of the month or year, it is,
Speaker 1: the features on the Moon always look the same, even
Speaker 1: though it's spinning around the Earth. How can it be
Speaker 1: that it's training at just the right rate for it
Speaker 1: to always look the same to us?
Speaker 3: We'll answer that.
Speaker 1: Question and more after the break.
Speaker 3: We'll be right back. Hey, we'll come back.
Speaker 1: We're answering questions about the moon, and so far we've
Speaker 1: talked about where the moon came from four and a
Speaker 1: half billion years ago and how scientists figured out what happened.
Speaker 1: Now we're going to answer another big question about the moon,
Speaker 1: which is why is the Moon always facing us the
Speaker 1: same way? If you think about it, the Earth is
Speaker 1: going around the Sun, but the Earth doesn't always face
Speaker 1: the same way to the Sun. If you were standing
Speaker 1: on the surface of the Sun, the Earth would look
Speaker 1: like it's spinning and it would look different every time
Speaker 1: you see it. But you can't say that about the Moon.
Speaker 1: The features of the Moon always look the same to us.
Speaker 1: The only people in history that have gotten in a
Speaker 1: different view of the Moon are the Apollo astronauts that
Speaker 1: went there back in the nineteen sixties. Well, the reason
Speaker 1: that the Moon always looks the same to us, according
Speaker 1: to Professor Matt Ziegler, has to do with the fact
Speaker 1: that the Moon isn't round. Okay, next question, Matt, why
Speaker 1: is the Moon always facing the same way to us?
Speaker 2: Okay, So the moon is what we call tidally locked
Speaker 2: which essentially means one side is always facing us.
Speaker 1: Right. Is that another characteristic of science.
Speaker 2: If you don't know, we give it a fancy name
Speaker 2: and basically says this is all we know about it. Yeah.
Speaker 2: So a lot of moons in the Solar System are
Speaker 2: also tidally.
Speaker 1: Locked, not just our moon.
Speaker 2: Like Jupiter's moons gets large. Four moons are all tidally locked.
Speaker 2: So one face of Io is always facing Jupiter, one
Speaker 2: face of Europa is always facing Jupiter.
Speaker 1: Whow, we're not alone. Our moon is not the only one.
Speaker 1: The moon is what scientists call tidally locked, which basically
Speaker 1: means it's always facing us the same way. But there
Speaker 1: is a reason why this happens, and it has to
Speaker 1: do with how gooey the Earth and the Moon are.
Speaker 2: This happens essentially because of how gooey an object is.
Speaker 3: Uh huh.
Speaker 2: So if something's spinning and it's gooey inside, it can
Speaker 2: dissipate energy.
Speaker 1: Okay, meaning like if you were spinning a water balloon.
Speaker 2: Yeah. Or a good analogy is if you're spinning a
Speaker 2: hard boiled egg versus a normal egg. Right, the hard
Speaker 2: boiled egg will spin and spin and spin, right, but
Speaker 2: the non heart boiled egg will slow itself down pretty
Speaker 2: quickly because that ah, yeah, that goo inside is kind
Speaker 2: of churning around and dissipating energy of that spin.
Speaker 1: I see, if I spin a raw egg in space,
Speaker 1: it'll eventually slow down because the liquid inside is losing energy.
Speaker 2: Yeah, And so something akin to this happens inside of
Speaker 2: a body like the Moon that initially early on at
Speaker 2: least had a large liquid inside of it, right.
Speaker 1: Oh. It initially the Moon was gooey, oh yeah, because
Speaker 1: it was formed from the giant impact right, which was
Speaker 1: really hot and made a lot of things melt. What
Speaker 1: doctor Ziegler is saying is that when the Moon formed,
Speaker 1: it was probably spinning really fast, but the inside of
Speaker 1: it was gooey. It was melted rock or lava. It
Speaker 1: was still hot from one the huge collision that formed
Speaker 1: the Moon happened, and that melted inside made the Moon
Speaker 1: stop spinning.
Speaker 3: It's sort of like.
Speaker 1: If you take a regular plastic water bottle and you
Speaker 1: try to toss it up into the air so that
Speaker 1: it spins, it'll eventually stop spinning in mid air, and
Speaker 1: that's because the water inside.
Speaker 3: Of it slashes around.
Speaker 1: Well, the same thing happened to the Moon, and actually
Speaker 1: it's also happening to the Earth.
Speaker 2: And the Moon is doing this today to the Earth. Actually,
Speaker 2: and so the Earth is actually slowing down. Right, Our
Speaker 2: day is twenty four hours now. It used to be
Speaker 2: twenty two hours, and earlier on in the Earth's history
Speaker 2: it was as short as four hours. So we think
Speaker 2: when the Earth and Moon formed that the Earth day
Speaker 2: was about four hours long.
Speaker 1: Really, yeah, we were spinning that fast.
Speaker 2: Yeah, and then the Moon has caused us to slow
Speaker 2: down that we're now at twenty four hours a day.
Speaker 2: What maybe in a billion years will be at twenty
Speaker 2: five hours a day or something like that. Right.
Speaker 1: Oh, so the reason the day feels this long is because.
Speaker 3: Of the moon.
Speaker 2: Yeah, it's the moon's fault.
Speaker 1: You had a long day, Blame the moon. Howl of
Speaker 1: the moon.
Speaker 2: Yeah, but if your day was too short, if it
Speaker 2: went by too fast, then think the moon.
Speaker 1: Right, Oh yeah, that's right, that's right.
Speaker 2: So the same way that the Earth day is slowly
Speaker 2: getting longer because the Earth is slowing its spin, the
Speaker 2: Moon went through something similar. It's just because the Moon
Speaker 2: is a lot smaller, it happened a lot faster. Basically.
Speaker 1: Okay, maybe take me back, So we had this big crash,
Speaker 1: A lot of stuff went out there into space eventually
Speaker 1: formed the moon. The moon had a squishy inside, meaning
Speaker 1: like it was lava inside.
Speaker 2: Right basically, right, Yeah, basically it's magma if it's not erupted.
Speaker 1: Not the whole other episode. It was magma or lava
Speaker 1: melted rock. It was melted rock, and it was spinning
Speaker 1: super fast.
Speaker 3: Yeah.
Speaker 2: So we had a fast spinning Earth and a fast
Speaker 2: spinning Moon, and basically them tugging on each other slowed
Speaker 2: each other down. Okay, So if I was a live
Speaker 2: bike there and on Earth, I would die because I
Speaker 2: couldn't breathe and standing on lava. But if I could
Speaker 2: somehow be there, my day would be four hours long,
Speaker 2: and I would see the moon like basically spinning in place.
Speaker 2: The Moon would look different every time I looked at it. Yeah,
Speaker 2: you would see the far side of the moon back then.
Speaker 1: Oh okay, And over time we slowed down and the
Speaker 1: moon slowed down to the point where now it's always
Speaker 1: looking at us the same way. Yes, So is it
Speaker 1: just luck that we just happened to be alive at
Speaker 1: a time when it's spinning. It just the right time
Speaker 1: for it to be always looking at it, or is
Speaker 1: it stuck there?
Speaker 2: I wouldn't say it's that lucky, because we think it's
Speaker 2: stuck very quickly, like in potentially a few thousand years
Speaker 2: to less than a million years, Like the moon slowed
Speaker 2: itself down very quickly. So the moon'spent tidally locked for
Speaker 2: most of Earth's history, really, and then it got stuck there. Yeah,
Speaker 2: and then it's been stuck there. And it's a little
Speaker 2: arbitrary which side ended up stuck facing the Earth. And
Speaker 2: that's still a debate of why the near side of
Speaker 2: the Moon is the near side.
Speaker 1: Okay, you might be wondering, if the Moon went from
Speaker 1: spinning really fast to slowing down, why did it stop.
Speaker 1: It's still going around to Earth, so why didn't the
Speaker 1: Moon suddenly start spinning in place the other way? Well,
Speaker 1: according to doctor Siegler, it all has to do with
Speaker 1: the shape of the moon.
Speaker 2: The Moon isn't a perfect sphere. It's kind of egg
Speaker 2: shaped itself or what rugby ball shaped or whatever you
Speaker 2: want to call it. Yeah, just slightly.
Speaker 1: Yes, the Moon is not perfectly round. You might have
Speaker 1: heard that the Earth is not perfectly round either. It's
Speaker 1: a little wider around the middle or the equator. That's
Speaker 1: because the Earth is spinning, and so it bulges out, but.
Speaker 2: The Moon isn't round.
Speaker 1: In a different way and for a different reason, the
Speaker 1: Moon doesn't bulge out, it's actually stretched out. It looks
Speaker 1: slightly closer to a rugby ball or an American football
Speaker 1: ball with one of the pointy ends pointing at the Earth.
Speaker 1: And the reason it's that shape isn't because it's spinning,
Speaker 1: but because the Earth is pulling on it. As the
Speaker 1: Moon goes in orbit around the Earth, the Earth's gravity
Speaker 1: pulls on the Moon to keep it in that orbit,
Speaker 1: and that causes the Moon to get stretched. And I
Speaker 1: think I came up with a good analogy for tidal logging,
Speaker 1: which is that sort of like if you're in a
Speaker 1: merry go round and someone's at the edge and they're
Speaker 1: about to fall off, like you grabbed their hand to
Speaker 1: keep them in the merry go round, and so the
Speaker 1: centropgal force is pulling them out, but I'm holding their
Speaker 1: hand pulling them in, and so that causes them to stretch, right.
Speaker 2: Okay, Yeah, that would be a good description of it.
Speaker 1: Yeah, okay, And so that's what causes the Moon to
Speaker 1: look sort of like a football shape pointing at us.
Speaker 2: Yeah, and at some point in the Moon's history it
Speaker 2: became solid enough, it cooled off enough that it froze
Speaker 2: in a football shape at that time.
Speaker 1: Okay, so here's what scientists think happened. There was a
Speaker 1: pre Earth planet somewhere close to our current orbit. He
Speaker 1: got smashed by another planet about the size of Mars.
Speaker 1: Some of the debris stayed in place and became the Earth,
Speaker 1: and some of the debris floated out in space and
Speaker 1: became the Moon. This new Moon was an orbit around
Speaker 1: the new Earth, but it was gooey and melted on
Speaker 1: the inside. That made it stop spinning in place. And
Speaker 1: because it was being pulled around in an orbit around
Speaker 1: the Earth, it stretched out a little to be closer
Speaker 1: to the shape of a football pointed back at the Earth.
Speaker 1: Then it cooled off and it got stuck in that shape.
Speaker 1: And once it got stuck in that shape, it became
Speaker 1: tidally locked, with one end of the football always pointing.
Speaker 3: At the Earth.
Speaker 1: Wait, wait, wait, wait, I think what you're saying is
Speaker 1: that just because of the particular history of when the
Speaker 1: Moon cooled is the reason we're always seeing the same side.
Speaker 1: Because if it had stay squisher longer. Maybe the moon
Speaker 1: would be rounder now, less football.
Speaker 2: Shape, maybe, but I think it would still become tidally
Speaker 2: locked eventually.
Speaker 3: Yeah. Okay, that's good.
Speaker 2: That's a good thought. I have to think about that
Speaker 2: one more than live on the air.
Speaker 1: Am I gonna get my name in a paper?
Speaker 2: Now? The cham.
Speaker 1: The cham procrastinating hot football theory of moon tidal walking. Yes,
Speaker 1: rolls off the tongue exactly.
Speaker 3: Okay.
Speaker 1: There are a couple of interesting things about this scenario.
Speaker 1: The first is that the arrangement of having something football
Speaker 1: shape pointing at you in orbit is stable, meaning that
Speaker 1: if the football, for some reason tilton starts to point
Speaker 1: in a different direction, the physics of the orbit will
Speaker 1: make it snap back. Remember the analogy of keeping someone
Speaker 1: from falling off a merry go round if they start
Speaker 1: to twist or turn, the fact that you're grabbing their
Speaker 1: hand and pulling on them towards the center of the
Speaker 1: merry go round means to'll go back to the same position.
Speaker 1: And that is why the moon is always facing us
Speaker 1: the same way. We're basically looking at one of the
Speaker 1: pointy ends of the football shaped moon. It's part of
Speaker 1: the moon that we never see that's the other pointy
Speaker 1: end of the football. Oh I see. So, like if
Speaker 1: I took the moon right now and I flipped it
Speaker 1: one to eighty degrees, we would be looking at the
Speaker 1: different side of the moon, but it would stay locked
Speaker 1: to that side of the moon. Yes, Oh, fascinating. Somebody
Speaker 1: should do that, man.
Speaker 2: Yeah, if they were like a giant impact or someone
Speaker 2: crashed a really really big rocket into the Moon, that
Speaker 2: they were enough to unlock it, you could have imagined
Speaker 2: that it would lock again in that other way.
Speaker 1: Like I'm tired of seeing this side of the moon, Like,
Speaker 1: I'm done with it, Let's see the other side. Somebody's
Speaker 1: give it a little push and it'll lock back to
Speaker 1: the other side exactly. Yeah.
Speaker 3: Okay.
Speaker 1: You might be wondering, why would I want to look
Speaker 1: at the other side of the moon? Is it really
Speaker 1: that different? Well, it turns out that it is different,
Speaker 1: and scientists don't really know why.
Speaker 2: But there are all these weird things we've learned about
Speaker 2: the moon. Now, is that the crust on the far
Speaker 2: side of the moon is a lot thicker than the
Speaker 2: crust on the near side of the moon. Whoa, and
Speaker 2: like the near side of the moon has all the
Speaker 2: lava flows right far side has none of that? What?
Speaker 2: And so why did the near side of the moon
Speaker 2: and the far side of the moon end up so different?
Speaker 2: And is that because of the tidal locking or is
Speaker 2: it a cause of why we tidally locked with this face?
Speaker 1: Did it tidally lock because one side is different than
Speaker 1: the other? Or is one side different than the other
Speaker 1: because it's going around the Earth always facing the same way.
Speaker 2: Yeah, And there are different ideas about what caused that difference.
Speaker 2: That the Moon might have had a giant impact of
Speaker 2: its own that created the difference originally, or that just
Speaker 2: imagine you tidally locked when you're still really close to
Speaker 2: the Earth and the Earth is still a molten ball
Speaker 2: of lava, but it really heats one side more than
Speaker 2: the other. Yeah, and that could cause a difference. So
Speaker 2: there are a number of theories out there of how
Speaker 2: that would cause the near side on the far side
Speaker 2: to be different in the way they are.
Speaker 1: In other words, we sort of know why the moon
Speaker 1: is always facing us the same way, but we don't
Speaker 1: know why it's this side of the Moon that's facing us.
Speaker 1: It could have been random, or there could be more things,
Speaker 1: but the moon and its history that we don't know about. Okay,
Speaker 1: when we come back, we're going to tackle the last
Speaker 1: mystery of the Moon, and it's a big one. It's
Speaker 1: a secret that could determine the future of space travel
Speaker 1: and it could help us understand the reason why there's
Speaker 1: life on Earth. So stay with us.
Speaker 3: We'll be right back.
Speaker 1: Hey, welcome back. We're not going to tackle the big
Speaker 1: open questions about the Moon. It turns out there's a
Speaker 1: lot we don't know about the Moon, including a question
Speaker 1: that might have huge implications for the future of space
Speaker 1: travel and what we know about how life started on Earth.
Speaker 1: Here's doctor Matt Ziegler, a planetary scientist involved in the
Speaker 1: New Artemis mission stake astronauts back to the Moon. Okay, Matt,
Speaker 1: what don't we know about the Moon? What are some
Speaker 1: of the biggest mysteries we're trying to figure out right now?
Speaker 2: Oh? Yeah, that depends on which subdiscipline of lunar science
Speaker 2: you're in.
Speaker 1: I think, really, what flavor of lunatic are you? So?
Speaker 2: One thing we don't know about is what's on the
Speaker 2: interior of the Moon.
Speaker 1: We don't know.
Speaker 2: Yeah, we have lots of pictures of the surface of
Speaker 2: the Moon. We know that sometimes stuff came up from
Speaker 2: the surface of the moon, But we want to figure
Speaker 2: out what's going on inside of the moon and how.
Speaker 1: Wait wait before in the episode, you told me that
Speaker 1: we know how much iron is inside the moon.
Speaker 2: Yeah, we know kind of basic things that like, the
Speaker 2: moon has these different layers and they're about this big.
Speaker 2: And we know that because in the nineteen seventies we
Speaker 2: had seismometers around the moon that we're recording moonquakes.
Speaker 3: Uh huh.
Speaker 2: And so from listening to a moonquake, you can tell
Speaker 2: kind of how thick the different layers are, what the
Speaker 2: density of the interior is, but you don't really know
Speaker 2: the composition entirely. You're kind of guessing based on density.
Speaker 2: And so one of the ways you can figure out
Speaker 2: the composition is by measuring how much heat is coming out.
Speaker 1: Yes, it turns out we don't know exactly what the
Speaker 1: inside of the Moon is made out of. So one
Speaker 1: project doctor Siger is working on is to take the
Speaker 1: moon's temperature. There are radioactive elements inside the Moon that
Speaker 1: are giving off heat, and so by burying thermometers all
Speaker 1: over the moon, you could reconstruct what all those radioactive
Speaker 1: elements are.
Speaker 2: And just this last year about a year ago now,
Speaker 2: we had the first geothermal heat flow probe since then
Speaker 2: land on the Moon with one of these missions that's
Speaker 2: kind of leading up to Artemis.
Speaker 1: Basically, we put a thermometer on the Moon.
Speaker 2: Yeah, we drilled the thermometer about a meter down below
Speaker 2: the nerve. And if we do this in enough locations
Speaker 2: around the Moon, we can start to put together this
Speaker 2: picture of how the heat producing elements are different around
Speaker 2: the whole Moon.
Speaker 1: Okay, And so the mystery is what exactly's in there?
Speaker 1: What could be inside the moon?
Speaker 2: Yeah? Is the material in the Moon the same or
Speaker 2: different than the material deep inside of Earth? Right? And
Speaker 2: that gets back to this idea did the Moon form
Speaker 2: from the Earth?
Speaker 1: Right?
Speaker 2: We know that these oxygen isotopes and sauch are telling
Speaker 2: us that the Moon and the Earth seemed to form together,
Speaker 2: but the composition of the deep interior is going to
Speaker 2: be another data point telling us did they form from
Speaker 2: the same spot?
Speaker 1: I see, what if you find that the inside of
Speaker 1: the Moon is made out of cheese.
Speaker 2: Well then then we better go there and mind the cheese.
Speaker 2: It's hard milking cows. And I don't know, I think
Speaker 2: it still might be cheaper to get cheese from cows
Speaker 2: on the Earth.
Speaker 1: But I don't know, but it's moon cheese. You can
Speaker 1: charge your premium, Yes, exactly.
Speaker 3: Okay. The last mystery.
Speaker 1: Doctor Seeger brought up about the Moon is a pretty
Speaker 1: interesting one. It's tied to the new Artemis missions that
Speaker 1: you might have seen in the news, where we're bringing
Speaker 1: astronauts back to the Moon and what they find could
Speaker 1: revolutionize the future of space travel.
Speaker 2: I would say. Another big mystery and one of the
Speaker 2: big motivators of the Artemis program coming up to the
Speaker 2: Moon and the whole international exploration of the Moon is
Speaker 2: is their ice at the poles of the Moon.
Speaker 1: Oh, we don't know.
Speaker 2: No, So we have craters, and because the Moon has
Speaker 2: a very low tilt, a crater near the pole will
Speaker 2: literally be a place where the sun don't shine.
Speaker 1: Right, I see, it's the moon hole. The moon hill
Speaker 1: is where the sun don't shine. Yes, yes, it turns
Speaker 1: out there might be places on the Moon with water
Speaker 1: on it. At the north and south poles of the Moon,
Speaker 1: there are craters so deep that they never get hit
Speaker 1: by light from the sun, and because they never feel
Speaker 1: the heat of the sun, they are super cold, which
Speaker 1: means they could be full of ice.
Speaker 2: And so these places on the surface of the Moon,
Speaker 2: because get no direct sunlight, actually can be colder than
Speaker 2: like the surface of Pluto. Whoa, And so any water
Speaker 2: molecules that land there, you know, maybe a comet hit
Speaker 2: the Moon, or maybe an asteroid that had like water
Speaker 2: in its rock materials hit the Moon. Ah, that water
Speaker 2: should stick at the poles.
Speaker 1: That's right, there could be huge lakes of ice inside
Speaker 1: of craters in the North and South poles of the Moon.
Speaker 1: You might have heard on a previous episode of this
Speaker 1: podcast or somewhere else that scientists think most of the
Speaker 1: water that we have here on Earth actually came from
Speaker 1: asteroids or comets that flew here from the far edges
Speaker 1: of the Solar System. In other words, most of the
Speaker 1: water that you drink that makes up your body could
Speaker 1: be important. Well, the same thing probably happened on the Moon.
Speaker 1: Must have also been hit with comets and asteroids full
Speaker 1: of water, except that on the Moon, because there's no atmosphere,
Speaker 1: most of that water probably evaporated into space when it
Speaker 1: got hit by sunlight, except potentially in the craters on
Speaker 1: the north and South poles of the Moon.
Speaker 3: And if there's water.
Speaker 1: There, it could have a big impact onto things. The
Speaker 1: first is space traveling, and we're hoping that that ice
Speaker 1: is there, both because we want, you know, astronauts to
Speaker 1: drink martinis on the Moon and could generally stay alive
Speaker 1: and hydrated.
Speaker 2: Yes, and hydrated, and also that if you saw the
Speaker 2: Space Shuttle ever launch, it had a big cloud coming out.
Speaker 2: What that was was mostly steam. Right, So water is
Speaker 2: rocket fuel.
Speaker 1: You could make rocket fuel out of water. Yeah, that's right.
Speaker 1: You can turn water into rocket fuel. It's a process
Speaker 1: called electrolysis where you separate the H two O into
Speaker 1: H and oh, and once you have oxygen gas and
Speaker 1: hydrogen gas, it can burn those to push rockets further
Speaker 1: out into space.
Speaker 2: So basically, if we can find enough ice on the Moon,
Speaker 2: the Moon also becomes a fueling station for our exploration
Speaker 2: of the universe. Right, that's wow. That's another exciting thing
Speaker 2: about it.
Speaker 1: And the other exciting thing about finding water on the
Speaker 1: Moon is that if there is water there in deep craters,
Speaker 1: it would be sort of an untouched record how water
Speaker 1: came to our solar system neighborhood billions of years ago.
Speaker 2: It's kind of like flypaper and it essentially should record
Speaker 2: the delivery of this water to the Moon.
Speaker 1: It might tell us like, yes, we did get water
Speaker 1: from asteroids or comets.
Speaker 2: Yeah, and tell us you know where the sources of
Speaker 2: our water came from. Yeah, And this is really important
Speaker 2: for understanding the big pictures of like, well, could there
Speaker 2: be life somewhere else out there? Right, because now we're
Speaker 2: finding all these other solar systems. And did the same
Speaker 2: thing that caused water to somehow come from outside the
Speaker 2: outer Solar System to Earth? Is that a common process
Speaker 2: that happens in every solar system or is it a
Speaker 2: weird thing that only happened in our Solar system?
Speaker 3: Yeah?
Speaker 2: That you would have a planet that's warm enough to
Speaker 2: live on because we're close but also wet.
Speaker 1: We want to know more about why Earth has water
Speaker 1: because water is the key ingredient in life.
Speaker 2: Yes, and the Moon holds a record of water that
Speaker 2: the Earth does not.
Speaker 1: You're making the Moon seem like a really good tourist stop,
Speaker 1: Like it might have fuel for you to go to
Speaker 1: other parts of the universe. It might have some good
Speaker 1: history so you can read while you're there. Yeah, and
Speaker 1: it might have some cheese inside also for your snacks. Exactly.
Speaker 2: Yeah, So in a thousand years, the Moon might be
Speaker 2: the wall drugs. You'll see signs for a thousand miles
Speaker 2: before you get to the name.
Speaker 1: It might be the BUCkies of space.
Speaker 2: Yes, the moon is, but we've only got one.
Speaker 1: Well, the buggies are really hard to find too, aren't they.
Speaker 2: Yeah?
Speaker 1: Yeah, all right, last question, Matt. When you step out
Speaker 1: in a warm Hawaiian night you see the full moon,
Speaker 1: what are you thinking that?
Speaker 2: Well, just last night, I think we're out and I
Speaker 2: saw the moon with my kids, and I said, you know,
Speaker 2: in a couple of weeks, there's going to be people
Speaker 2: behind that thing, right, And that thought alone is pretty
Speaker 2: neat and exciting. Yeah, that there will be people there,
Speaker 2: and maybe you know, in a few years it will
Speaker 2: be all of us, right, a lot of us going
Speaker 2: going to this gas station in the sky. Yeah, And
Speaker 2: it's just neat to look at the Moon and knowing
Speaker 2: about some of this history, of all the processes that
Speaker 2: happened on the Moon, from the delivery of ice to
Speaker 2: volcanoes on the surface of the Moon. There's a lot
Speaker 2: of exciting stuff that you can imagine going on up there,
Speaker 2: and you can imagine it differently on the moon because
Speaker 2: you can see it. You know, I see Jupiter in
Speaker 2: the night sky, and I can imagine what's going on
Speaker 2: in that dot maybe. But the Moon is somehow this
Speaker 2: thing that we all can relate to because it's still something.
Speaker 2: We can see it from the Earth.
Speaker 1: And it is a part of the Earth, right.
Speaker 2: Yeah, it appears to be part of the Earth and
Speaker 2: part of our formation of the Earth. And we're part
Speaker 2: of the Earth, right We're made of the material from
Speaker 2: the Earth too, So the moon is.
Speaker 3: Our brother, all right.
Speaker 1: So to recap scientists think our moon came from the
Speaker 1: random collision of two small planets. The moon is always
Speaker 1: facing us the same way because it's shaped a little
Speaker 1: like an American football. We're not one hundred percent sure
Speaker 1: what's inside of it. It could still be cheese. And
Speaker 1: the moon might in the future serve as a gas
Speaker 1: station for our exploration of the cosmos. So if all of
Speaker 1: that doesn't turn you into a lunatic, I don't know
Speaker 1: what will. Thanks for joining us. See you next time
Speaker 1: you've been listening to science stuff. Production of Heart Radio
Speaker 1: written and produced by me or Hey Cham, edited by
Speaker 1: Rose Seguda, Executive producer Jerry Rowland, and audio engineer and
Speaker 1: mixer Kasey Pegram, and you can follow me on social media.
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