Speaker 1: Daniel. It's great to be talking to you today. So
Speaker 1: now I would love for you to go ahead and
Speaker 1: reassure me that today we're not going to be talking
Speaker 1: about how scary and dangerous the universe is.
Speaker 2: Oh no, no, not at all. Well, I mean maybe
Speaker 2: a little bit.
Speaker 1: Uh, Daniel, that is clearly hedging. I'm gonna need more clarity.
Speaker 2: I mean, we're only going to talk about scary and
Speaker 2: dangerous family destroying things that already happened in.
Speaker 1: The past because we have some way to prevent these
Speaker 1: scary and dangerous things from happening in the future, like
Speaker 1: to my children. Right, no comment, dude, not okay, totally, totally,
Speaker 1: not okay.
Speaker 2: You got to embrace the danger, Kelly. That's where the
Speaker 2: thrill is.
Speaker 1: I I guess I'm pushing through one way or another.
Speaker 1: So let's do this just another show my kids won't
Speaker 1: listen to.
Speaker 3: Hi.
Speaker 2: I'm Daniel, I'm a particle physicist and a professor at
Speaker 2: UC Irvine, and I'm looking forward to the destruction of
Speaker 2: the Earth.
Speaker 1: I'm Kelly Waitersmith, adjunct faculty at Rice University, and I'm
Speaker 1: looking forward to yet another episode filled with existential dread.
Speaker 2: You know in those moments as the Earth is being
Speaker 2: obliterated by some huge impactor, We're going to learn a
Speaker 2: lot about how the Earth is put together and what's
Speaker 2: inside of it. And as all those insides come to
Speaker 2: the outsides.
Speaker 1: You know, I'm going to hope that in that moment
Speaker 1: we all stop worrying about the details and we just
Speaker 1: hug our kids and our dogs and stuff. But I'm
Speaker 1: sure the physicists we'll still be collecting data, and the
Speaker 1: economists will be quantifying something, and anyway, well.
Speaker 2: We are all still live and wondering about the universe.
Speaker 2: And so welcome to the podcast Daniel and Jorge Explain
Speaker 2: the Universe, a production of iHeartRadio in which we do
Speaker 2: our best to understand the nature of the universe before
Speaker 2: it comes crashing down on us. We try to cast
Speaker 2: our minds out into the deepest, darkest reaches of space
Speaker 2: and understand what's out there, how does it all work.
Speaker 2: We look back into the history of the universe to
Speaker 2: understand where it all came from, how it all works,
Speaker 2: and how we got to be where we are. Jorge
Speaker 2: can't be with us today, but I'm very glad to
Speaker 2: have with us. Kelly. Kelly, thanks for joining us on
Speaker 2: another adventure of dangerous history of the universe.
Speaker 1: Thanks for having me. Despite what it might sound like,
Speaker 1: I really do enjoy these episodes.
Speaker 2: And there is a lot of danger out there in
Speaker 2: the universe. If you cast your telescopes up to the Moon,
Speaker 2: for example, you see that the surface is riddled with craters.
Speaker 2: It looks like it's survived a drive by asteroiding. And
Speaker 2: if you look even further out into the Solar System,
Speaker 2: you can see crazy things like comets smashing into Jupiter,
Speaker 2: creating fireballs the size of Earth. All this kind of
Speaker 2: stuff seems to be happening all over the Solar System.
Speaker 2: It's a dangerous place, epic and that might make you wonder,
Speaker 2: of course, how safe is our home here? Is the
Speaker 2: plan be strategy for a planet Earth super important? Do
Speaker 2: we need to scramble to get off of Earth before
Speaker 2: something comes and obliterates us. One way to answer that
Speaker 2: question is to think about our cosmic history. Of course,
Speaker 2: we'd like to know what might be hitting us in
Speaker 2: the future, but the best way to learn about that
Speaker 2: might be to think about things that have already hit
Speaker 2: us in the past.
Speaker 1: Are you going to be making me a question? The
Speaker 1: conclusions from my book that maybe we do need that
Speaker 1: Plan B and we need to start today because our
Speaker 1: demise is imminence.
Speaker 2: Maybe, or you could also look at this history and say, hey,
Speaker 2: we survived all this stuff, so maybe it's not such
Speaker 2: a big deal.
Speaker 1: Right, all right, Well, let's see where this goes.
Speaker 2: And so today on the podcast, we're going to be
Speaker 2: diving deep into the history of Earth to answer the
Speaker 2: question what is the largest asteroid impact in Earth's history?
Speaker 1: You know who has a big impact. Your listeners, Let's
Speaker 1: hear what they have to say.
Speaker 2: Thanks very much to everybody who volunteers for this audience
Speaker 2: participation segment of the podcast. We really love hearing your voices.
Speaker 2: It helps us calibrate the level of the podcast. Plus,
Speaker 2: we love you guys. We want to hear your voices
Speaker 2: and we hope you enjoy hearing your own voice on
Speaker 2: the podcast. If you'd like to play for a future episode,
Speaker 2: don't be shy. Write to me two questions at Danielandjorge
Speaker 2: dot com. Here's what listeners had to say. Wasn't just
Speaker 2: the asteroid that made the dinosaurs extinct? Almost meaning?
Speaker 4: Was it thea the planetoid that theoretically smashed into the
Speaker 4: Earth and kind of blew them both apart and became
Speaker 4: the Moon. I saw a model recently that looked so
Speaker 4: beautiful of kind of this orange fluid, two spheres banging
Speaker 4: into each other, and then the Moon forming, So maybe
Speaker 4: it was that one.
Speaker 3: I think that there's remnants of an ancient impact crater
Speaker 3: in Europe somewhere, or maybe South America.
Speaker 2: I can't really remember.
Speaker 3: From memory. There was a very large asteroid impact in
Speaker 3: South America somewhere that closed one of the dinosaur extinctions,
Speaker 3: but I can't remember what its name is. Well, alternatively,
Speaker 3: could the moon the collision that created the Moon be
Speaker 3: the largest impact that the Earth has they've experienced. I
Speaker 3: don't know whether that counts as an asteroid, but maybe
Speaker 3: the first one.
Speaker 5: That comes to mind disaster that killed the dinosaurs, though
Speaker 5: I guess that was only like sixty five million years ago.
Speaker 5: Since the Earth has been around for I think billions
Speaker 5: of years are probably many more, much larger than that
Speaker 5: earlier on. I guess another idea might be whatever it
Speaker 5: was that hit the early proto Earth and split off
Speaker 5: into the Moon.
Speaker 6: Well, the extinction event of the dinosaurs comes to mind
Speaker 6: up top, but probably there was a larger collision when
Speaker 6: the planet was still pretty squishy. Probably there was a
Speaker 6: larger one there, my best guess.
Speaker 1: So one thing that I thought was interesting about the
Speaker 1: responses is that I think there was a bit of
Speaker 1: reticence to answer because folks weren't certain that they had
Speaker 1: the difference between asteroids, meteors, comets meteorites clear. Should we
Speaker 1: quickly go over like which ones and clarify that we're
Speaker 1: specifically talking about asteroids today or do you think we
Speaker 1: don't need to go over that.
Speaker 2: No, I'm always down for exploring the ridiculous naming systems
Speaker 2: in physics.
Speaker 1: Or is today's episode just like giant hunks of stuff
Speaker 1: and we're being general?
Speaker 2: I mean, from a physics point of view, it doesn't
Speaker 2: really matter. It's giant hunks of stuff hurtling themselves towards
Speaker 2: the Earth that created huge explosions and left marks on
Speaker 2: the Earth's surface. But it does kind of matter where
Speaker 2: those things came from if you want to think about
Speaker 2: our future prospects and whether, for example, your children will survive.
Speaker 1: And I do care about that because I'm not a physicist,
Speaker 1: And so what's the difference between an asteroid, a comet.
Speaker 2: And a meteor yeah, great question. So an asteroid is
Speaker 2: basically a small rock that orbits the Sun. These things
Speaker 2: are smaller than a planet if they're like bigger than
Speaker 2: the pebble sized objects that are called medioroids. So asteroids
Speaker 2: are bigger than meteoroids, but smaller than planets. And it's
Speaker 2: also the distinction that planets have to like clear the
Speaker 2: path they're in. So you can have like a bunch
Speaker 2: of asteroids in like a ring around the Sun and
Speaker 2: that's not an issue. But nothing in there can basically
Speaker 2: be a planet, even if it's as big as a planet.
Speaker 2: So there's a complicated distinction there between like planets, dwarf planets,
Speaker 2: asteroids and meteoroids. And then of course there's comets.
Speaker 1: Okay, but it's mostly all just a matter of size.
Speaker 2: It's mostly a matter of size. Comets actually come from
Speaker 2: a different place that come from deeper in their Solar system.
Speaker 2: There's either the Kuiper Belt or the Ort Cloud for
Speaker 2: really distant stuff, and we'll talk about that a little bit.
Speaker 2: So that's asteroids and meteoroids and comets. Those are all
Speaker 2: things out in the Solar System. A meteor is something
Speaker 2: that's burning up in our night sky, something that hits us,
Speaker 2: and so that can be an asteroid or a comet
Speaker 2: or a little bit of alien space junk or whatever.
Speaker 2: So meteor is basically when it hits the Earth, asteroid,
Speaker 2: meteoroid in comet is when it's still out there in space.
Speaker 1: Got it, Okay? And so the listeners were very interested
Speaker 1: or very aware of the extinction events where an asteroid
Speaker 1: wiped out the dinosaurs. And then there was another person
Speaker 1: who wanted to know if when the early Earth got
Speaker 1: hit and the Moon split off, does maybe that count? Yeah,
Speaker 1: the listeners are pretty darn well informed.
Speaker 2: I'd say it's almost like they're listening to an awesome
Speaker 2: podcast regularly that teaches them all about the Solar System
Speaker 2: and the universe. Congrats and they pass the exam. But
Speaker 2: you're right that it is important to understand, like what's
Speaker 2: out there in the Solar System, where is this stuff
Speaker 2: coming from? What are the sizes we expect for things
Speaker 2: that are raining down on the Earth this death from above?
Speaker 1: Okay, So we've done like an overview of definitions. Let's
Speaker 1: jump into where asteroids come from and give a little
Speaker 1: bit more background about where you would find asteroids in particular, and.
Speaker 2: Go so something that you don't often realize when you
Speaker 2: look up at the night sky is you mostly see
Speaker 2: stars and planets, and you think about the Solar System
Speaker 2: in terms of, you know, like the Sun and the
Speaker 2: planets and maybe a couple of moons here or there.
Speaker 2: But the Solar System is much much dirtier than that.
Speaker 2: You know, there's a whole spectrum of chunks of stuff,
Speaker 2: from the Sun down to planets, down to moons, down
Speaker 2: to much smaller rocks. And as the stuff gets smaller,
Speaker 2: becomes much more numerous. So you've like obviously one Sun,
Speaker 2: a few planets, dozens of moons, But when you get
Speaker 2: to smaller chunks of stuff, asteroids and meteoroids and all
Speaker 2: that stuff, there's zillions and billions and even trillions of
Speaker 2: these things. But of course they're not luminous, right, They
Speaker 2: don't glow, and they don't reflect as much light because
Speaker 2: they're small, so you don't mostly see them in the
Speaker 2: night sky. They're mostly invisible. So the picture I want
Speaker 2: to paint in your mind is space being filled basically
Speaker 2: with dark rocks.
Speaker 1: Wait, so I have an important question. Yeah, So in
Speaker 1: Star Wars, this is how all important questions start in
Speaker 1: Star Wars, when they're like trying to navigate around rocks
Speaker 1: and space. There's just like they're everywhere and you can't
Speaker 1: get around them. If you were out in space and
Speaker 1: you were to stand on like one chunk of something,
Speaker 1: would you be able to see other chunks of stuff nearby?
Speaker 1: Or even though there's lots of them, are they still
Speaker 1: like pretty darn spread out or is it like Star Wars.
Speaker 2: No, it's a great question. It's not like Star Wars.
Speaker 2: It turns out Star Wars not a documentary, not a
Speaker 2: reliable way to plan your space mission.
Speaker 1: Who you got to know? That would have been embarrassing
Speaker 1: to say that public.
Speaker 2: But no, these rocks are pretty big. But they're also
Speaker 2: very far apart. Because space is vast, especially as you
Speaker 2: get out into the further reaches of the Solar System,
Speaker 2: the amount of space between these planets gets enormous, right,
Speaker 2: The volume of the sphere goes as the radius cube,
Speaker 2: and so if you're like another million miles away from
Speaker 2: the Sun, then you create a volume of space which
Speaker 2: is much much bigger than everything inside of it. And
Speaker 2: so even though there are lots and lots of asteroids
Speaker 2: out there, remnants from the formation of the Solar System
Speaker 2: that didn't pull together into planets or were disturbed by
Speaker 2: the gravity of Jupiter, for example, to prevent them from coalescing.
Speaker 2: They're far enough apart that you can't really have that's
Speaker 2: sort of like exciting space dodgem game.
Speaker 1: Well, you've dashed a lot of Star Wars related dreams today,
Speaker 1: but it's important to know, so, all right, So where
Speaker 1: do you find most.
Speaker 2: Of these So most of these things are in the
Speaker 2: asteroid belt, this region between Mars and Jupiter. And that's
Speaker 2: no accident. You know, as the Solar System is forming,
Speaker 2: it clumps together, mostly into the Sun and then into
Speaker 2: the planets, and planets form when you have like a
Speaker 2: seed of a heavy object, something that can pull stuff
Speaker 2: together and generate its own gravitational well, rather than just
Speaker 2: getting sucked into the Sun. But because Jupiter became so big,
Speaker 2: it's gravity was strong enough that it disrupted the formation
Speaker 2: of other stuff. And so that's why, for example, these
Speaker 2: asteroids near Mars Jupiter, even though they've been around for
Speaker 2: billions of years, they haven't like gradually coalesced into one
Speaker 2: big object. There's lots and lots of them over there.
Speaker 1: Oh, it's kind of fun to imagine what it would
Speaker 1: have been like to have another planet out there. It's
Speaker 1: like Jupiter.
Speaker 2: Another way you can see the effect of Jupiter on
Speaker 2: these asteroids is that there's a bunch of astrailids in
Speaker 2: orbit with Jupiter. If you draw an ellipse for where
Speaker 2: Jupiter goes around the Sun, it's not actually totally empty.
Speaker 2: There's a whole cluster of asteroids that are leading Jupiter
Speaker 2: and another cluster that are following Jupiter. They're called the
Speaker 2: Greeks and the Trojans. These two like different camps of asteroids.
Speaker 1: So I thought that planets were supposed to clear their orbits.
Speaker 1: Does that okay?
Speaker 2: All right?
Speaker 1: But Jupiter is huge, so all right, go on.
Speaker 2: So if you were like a lawyer for Pluto, you
Speaker 2: might raise this objection and say, hey, folks, you've been
Speaker 2: inconsistent here because planets are supposed to clear their orbit.
Speaker 2: But you know, when planets get big enough, then they
Speaker 2: can actually collect asteroids in these lagrange points, these points
Speaker 2: where the Sun and Jupiter's gravity balances out in a
Speaker 2: way that there's like a little gravitational well there for
Speaker 2: asteroids to collect in. But it's super cool. We're actually
Speaker 2: sending a mission to go visit these Trojans pretty soon
Speaker 2: be a lot of fun.
Speaker 1: Wait your what.
Speaker 2: We have a mission that's going to go visit the
Speaker 2: asteroid belt and one of these trojans.
Speaker 1: Ooh, that's exciting.
Speaker 2: Yeah, we had a whole podcast episode about it, Me
Speaker 2: and you, so check that one out if you're curious
Speaker 2: about it. But even though you imagine this space to
Speaker 2: be filled with rocks, and some of these are pretty big,
Speaker 2: like Series is a whole dwarf planet in this region.
Speaker 2: It's like nine hundred kilometers in diameter, So that's pretty big.
Speaker 2: I mean, it's like a tenth or thirteenth of the
Speaker 2: radius of Earth. That's the biggest thing out there in
Speaker 2: the asteroid belt. But after that it pretty much falls off.
Speaker 2: Like half of the mass of the asteroid Belt is
Speaker 2: in just four big Mama asteroids. After that, it's a
Speaker 2: bunch of smaller stuff.
Speaker 1: And those big Mama asteroids are stay input.
Speaker 2: I hope mostly they stay input. NaSTA does a really
Speaker 2: good job of tracking these folks and thinking about their trajectory.
Speaker 2: They can predict them out to about one hundred years
Speaker 2: from now. After that, it's too chaotic with all the
Speaker 2: influence from Jupiter and Saturn and the other little bits
Speaker 2: of the asteroid belt for them to reliably predict where
Speaker 2: they're going to be. But mostly they know where all
Speaker 2: the big ones are and they know they're not going
Speaker 2: to hit us in the next one hundred years.
Speaker 1: All right, all right, that's that certainty that I can handle.
Speaker 1: I'll sleep tonight, all right. So, so half of the
Speaker 1: mass is in those four objects, and how is the
Speaker 1: rest of the mass distributed?
Speaker 2: So after that it's lots of tiny little ones. And
Speaker 2: you know, it used to be much more. It used
Speaker 2: to be that the asteroid belt had like one hundred
Speaker 2: or a thousand times as much mass as it does.
Speaker 2: But when it's so dense over there, they will eventually
Speaker 2: bump into each other or even just pull on each
Speaker 2: other gravitationally and fall out of orbit and then plummet
Speaker 2: into the Sun. So something like ninety nine point ninety
Speaker 2: percent of the mass of the asteroid belt is gone.
Speaker 2: It was lost in the first one hundred million years
Speaker 2: of the Solar System. And what's left is a bunch
Speaker 2: of smaller asteroids. But even if you add it all
Speaker 2: up together, it's not even that much stuff. It's like
Speaker 2: four or five percent the mass of the Moon. If
Speaker 2: you like gathered it all together into one big ball.
Speaker 1: So do we need to worry about like so you
Speaker 1: said most of it has already fallen into the Sun
Speaker 1: or presumably fallen into Jupiter or something. Is the rest
Speaker 1: of it? Something like if voyager, you know, was going
Speaker 1: out past Jupiter, did we have to worry about it
Speaker 1: running into that stuff? Or there's just not that much
Speaker 1: of it out there?
Speaker 2: There's not that much of it out there. Yeah, if
Speaker 2: you pointed a spaceship through the asteroid belt, you'd have
Speaker 2: a very small chance of hitting anything.
Speaker 1: Nice. That's good to hear.
Speaker 2: Yeah, so you can put your kids on that spaceship
Speaker 2: and send amount of space without worrying about it.
Speaker 1: Kelly, No, No, my kids are staying here. I wrote
Speaker 1: a whole book on why this is a bad idea,
Speaker 1: four years of my life. My kids are staying here
Speaker 1: unless they want to go, and then I probably won't stop. Okay,
Speaker 1: let's take a break. So we've talked about the asteroid
Speaker 1: belt between Mars and Jupiter. There are other clumps of
Speaker 1: death from above, and we'll get to that after the break,
Speaker 1: all right, So, Daniel, where else are these clumps of death?
Speaker 1: Where else could they be coming from if they're going
Speaker 1: to be heading towards Earth.
Speaker 2: So the asteroids are not really something to worry about.
Speaker 2: We know where most of the big ones are, as
Speaker 2: we said, and we know where they're going to be.
Speaker 2: The more dangerous things are further out in the Solar system,
Speaker 2: out in the Kuiper Belt, like past Neptune, like between
Speaker 2: thirty and fifty AU, is a bunch of frozen ice cubes,
Speaker 2: essentially out past the snow line where the Sun is
Speaker 2: not powerful enough to vaporize. Ice can still be a
Speaker 2: big factor in the formation of clumps of stuff and
Speaker 2: also planets. Right, That's why we call Neptune and Urinus
Speaker 2: the ice giants. So out there in the Kuiper Belt,
Speaker 2: they're basically a bunch of big frozen snowballs, and sometimes
Speaker 2: some of them fall towards the center of the Solar system,
Speaker 2: and those are comets because as they burn their way
Speaker 2: towards the Sun, the Sun is then boiling stuff off
Speaker 2: of them, making that tail.
Speaker 1: And you maybe already said this, and I guess I
Speaker 1: just didn't understand. What, why are we more at risk
Speaker 1: from stuff in the Kuiper Belt than the asteroid belt,
Speaker 1: which is closer is there movement just more chaotic.
Speaker 2: Well, for two reasons. One is they come from further out,
Speaker 2: so that by the time they make it into our
Speaker 2: inner neighborhood of the Solar System, they're moving faster, like
Speaker 2: they've fallen further into a gravity well. And velocity is
Speaker 2: important because the faster you're moving when you hit the Earth,
Speaker 2: the more energy you're depositing, the more the seismic waves,
Speaker 2: the more stuff you toss up into the atmosphere. Velocity
Speaker 2: does matter. The other reason is that these things are
Speaker 2: harder to study. They're further away, so they're harder to spot,
Speaker 2: and they're more erratic. They're more susceptible to like passing
Speaker 2: stars that give them a little gentle tug and nudge
Speaker 2: them in towards the center of the Solar System. And
Speaker 2: there's so many of them out there that we can't
Speaker 2: possibly track all of them, so they're harder to spot
Speaker 2: and higher speeds.
Speaker 1: I don't like it all.
Speaker 2: Right, Well, then you're definitely not going to like. The
Speaker 2: Org cloud, even further away from the Sun is a
Speaker 2: theoretical cloud of basically icy many planets. We think there
Speaker 2: might be trillions of objects in there that are more
Speaker 2: than a kilometer wide, and maybe even billions that are
Speaker 2: twenty kilometers wide. You said theoretical, Yes, theoretical.
Speaker 1: I had assumed we knew this about the Ork Cloud already.
Speaker 1: This is just like stuff we think. I mean, I
Speaker 1: guess it makes sense. It's really far away, but we're
Speaker 1: we just think it's out there. We're not sure.
Speaker 2: We think the Orc Cloud is out there. It makes sense,
Speaker 2: it's part of all of our simulations. It's been predicted,
Speaker 2: but we've never actually seen something in the Ork Cloud
Speaker 2: because it is super duper far away. These things are
Speaker 2: like one to three light ears from the Sun.
Speaker 1: But it's on a bunch of the illustrations I've seen.
Speaker 2: Artists' conceptions. Oh my gosh, I know. No, this is
Speaker 2: basically an interstellar space. It's not really part of the
Speaker 2: heliosphere or the Solar system. But we do think it's
Speaker 2: part of the gravitational system of the Sun, and there's
Speaker 2: a lot of stuff out there. Theoretically, it's much further
Speaker 2: out than like even where Voyager one has gone, and
Speaker 2: it's so far away, and these things are pretty small,
Speaker 2: so it's hard to spot them directly.
Speaker 1: Well, Voyager one gets there before it runs out of power.
Speaker 2: It's going to take like three hundred years for Voyager
Speaker 2: one to get there, and it basically ran out of power. Recently,
Speaker 2: I heard that they stopped hearing from it, so we
Speaker 2: already know the end of that story.
Speaker 1: Oh oh, that's really sad. I can't believe I missed that. Yes,
Speaker 1: Christ in Peace one.
Speaker 2: Exactly, or floating piece or whatever you say out there
Speaker 2: in space. The Ork Cloud is theoretical. We're fairly confident
Speaker 2: it's there. We see indirections, and also we think it's
Speaker 2: the source of the longer period comets. Because these things
Speaker 2: are so far away, they take a long time to
Speaker 2: make it into the Inner Solar System and maybe impact
Speaker 2: on a juicy Inner Solar System planet or not. And
Speaker 2: so the shorter period comets probably come from the Kuiper Belt,
Speaker 2: and the longer period comets with even more mass and
Speaker 2: even more velocity come from the Org Cloud.
Speaker 1: Have we seen something come closer to us that we
Speaker 1: think came from ort cloud.
Speaker 2: Well, we've definitely seen a lot of long period comets,
Speaker 2: these comments that take centuries sometimes to orbit the Solar System,
Speaker 2: and so we think that they originated from the Ork Cloud.
Speaker 2: So yeah, we think those things are visitors from the
Speaker 2: Ork Cloud. And that's one reason why people are excited
Speaker 2: to like go sample comets while they're sending probes out
Speaker 2: there to grab bits of comments to see, like what
Speaker 2: is it like out there in the Orc cloud. Be
Speaker 2: awesome to get a sample of the Ork cloud that
Speaker 2: visited the Inner Solar System.
Speaker 1: Okay, so we've talked about where these things reside. Let's
Speaker 1: talk a little bit more about size. So like, if
Speaker 1: something that's a meter in diameter comes at us, that's
Speaker 1: not a problem, right, that's going to burn up.
Speaker 2: That's not a problem. That's actually kind of awesome. Yeah,
Speaker 2: it makes really nice streak in the sky. It doesn't
Speaker 2: really do any damage. And also it happens all the time.
Speaker 2: You know, space, as we said, is filled with dark rocks.
Speaker 2: Is not just the asteroids that we've cataloged in the
Speaker 2: asteroid belt. There's rocks out there all over the place,
Speaker 2: just floating free, tugged by Jupiter here and there. And
Speaker 2: that's why we see meteor showers. Right, Every meteor shower
Speaker 2: are a bunch of rocks hitting the Earth. Fortunately, our
Speaker 2: atmosphere is dense enough to act like a big pillow,
Speaker 2: and so when they hit the atmosphere, there's friction, they
Speaker 2: heat up and then they burn up before they hit
Speaker 2: the ground. And so stuff that's less than a meter
Speaker 2: in size, it happens all the time.
Speaker 1: Yeah, a big slammable pillow.
Speaker 2: You know.
Speaker 1: I was when I was researching the spacebook, and we
Speaker 1: were looking at companies that had sort of like out
Speaker 1: there ways of planning to make money on space stuff.
Speaker 1: There was a company that was pitching that they could
Speaker 1: make you essentially like asteroid meteor shower sorts of things
Speaker 1: by like sending masks to space and then having it
Speaker 1: come down at a certain time, and that they could
Speaker 1: like determine the colors that it would be. Wow, so like,
Speaker 1: you know, the most epic birthday present, like a pink
Speaker 1: meteor shower for your Kinsania.
Speaker 2: But anyway, that sounds like there's no way that could
Speaker 2: go wrong. Yeah, absolutely, that doesn't sound dangerous at all.
Speaker 1: No, No, it's great, it's great. Okay, all right, so
Speaker 1: we've got a meter and it's beautiful. When does it
Speaker 1: start becoming less beautiful and more scary?
Speaker 2: Yeah, So there's this trade off. As they get larger,
Speaker 2: they get more dangerous, and fortunately they also get less common. So,
Speaker 2: for example, stuff that's like a meter wide hits the
Speaker 2: Earth around once per day, and that's not that big
Speaker 2: a deal. I mean, you can make a big explosion
Speaker 2: in the sky and it's the kind of stuff that
Speaker 2: you hear about, you know, like the churbulence explosion in
Speaker 2: Russia recently. It's an order magnitude of a meter size thing.
Speaker 2: Often this just happens, you know, over the ocean. Nobody notices,
Speaker 2: but occasionally you get a bigger one. And if you
Speaker 2: had something like ten or twenty meters wide, this happens
Speaker 2: like every ten or fifty years, then you're starting to
Speaker 2: get energies comparable to an atomic bomb explosion.
Speaker 1: WHOA, I feel like we should hear about that more often.
Speaker 1: But I guess I guess you said that it happens
Speaker 1: over the ocean a lot, and so we wouldn't hear
Speaker 1: about it.
Speaker 2: Yeah. I had exactly the same reaction. I was like,
Speaker 2: hold on, a second, nuclear bomb explosions not that common.
Speaker 2: You think you'd hear about it. This is beyond the news.
Speaker 2: You'd feel it or something. But these things tend to
Speaker 2: happen in the upper atmosphere and often over the ocean,
Speaker 2: so they're just not observed or reported.
Speaker 1: But with how much like surveillance equipment we have in space,
Speaker 1: I would expect you'd see it. But I guess that
Speaker 1: surveillance equipment, you know, has only been up there since
Speaker 1: like the sixties or something like that, so we don't
Speaker 1: have that many years of data. Wow, Okay, that's the
Speaker 1: numbers you're giving are much more regular than I would
Speaker 1: have guessed. Let's move on.
Speaker 2: Yeah, and it's also energy deposited in the upper atmosphere,
Speaker 2: so it's not like the equivalent of somebody sitting off
Speaker 2: a nuclear weapon on land or even dropping one in
Speaker 2: the ocean. And so while the military is definitely tracking
Speaker 2: these things, and we talked about like the network of
Speaker 2: satellites that the military has when we're talking recently about
Speaker 2: interstellar asteroids and whether they've hit the Earth and whether
Speaker 2: Avilobe has actually gathered any spherials from them. So we
Speaker 2: know the folks are tracking them, it's just not that
Speaker 2: big a deal. It's like getting your shields zapped with lasers,
Speaker 2: but you know your shields are pretty strong.
Speaker 1: Okay, all right, So these explosions are happening in the atmosphere.
Speaker 1: So have we talked about a size yet that could
Speaker 1: reach the Earth, and is there a relationship between size
Speaker 1: and whether Yeah, there's got to be a relationship between
Speaker 1: size and whether or not it makes it to the
Speaker 1: Earth to impact, right.
Speaker 2: Yeah, So anything above like twenty five or fifty meters
Speaker 2: will probably make it to the surface. Anything smaller than
Speaker 2: that is probably going to burn up in the atmosphere.
Speaker 2: And once you get up to that size, we're talking
Speaker 2: about a significant amount of energy. So like one hundred
Speaker 2: meters size asteroid if it hits, which is something that
Speaker 2: happens every few thousand years, we think has as much
Speaker 2: energy as three thousand atomic bombs.
Speaker 1: Oh my gosh, Okay, so five thousand years. How long
Speaker 1: have we had recorded history? Do we have? And I
Speaker 1: know it could have happened in the ocean and we
Speaker 1: missed it or something, But do we have any recorded
Speaker 1: histories of this sort of thing happening?
Speaker 2: We do, we think, and we're going to dig into
Speaker 2: that in just a minute.
Speaker 1: Who suspenseful?
Speaker 2: And then as the things get larger, like a kilometer wide,
Speaker 2: we're talking about something every half million years. We think
Speaker 2: probably five kilometer wide asteroids happen every twenty to forty
Speaker 2: million years, and basically anything above five or ten kilometers
Speaker 2: is extinction level event. We're talking about creating creators that
Speaker 2: are like one hundred kilometers wide, tossing up enormous amounts
Speaker 2: of stuff into the atmosphere, obliterating a consonant instantly with fireballs,
Speaker 2: so like an enormous amount of energy, but fortunately very
Speaker 2: very rare.
Speaker 1: I don't know what to say other than maybe I'm
Speaker 1: not going to be sleeping tonight. Maybe I take it back.
Speaker 2: And so, of course we're really curious about if this
Speaker 2: is going to happen in the future, and when we
Speaker 2: can also look around the Earth for signs at this
Speaker 2: this happened because it's hit the Moon, it's hit basically
Speaker 2: every surface in the Solar System. The Earth is not special.
Speaker 2: The Earth also gets hit with this stuff, but only
Speaker 2: the larger ones make it down to the surface and
Speaker 2: cause impact craters.
Speaker 1: So now I'm realizing that I would love to know
Speaker 1: how we figured out these frequency data that you said.
Speaker 1: You know, how do we know that you get a
Speaker 1: five meter size one almost every five years? And how
Speaker 1: can we search the Earth for evidence of how often
Speaker 1: it got hit? Are you saying that we don't bother
Speaker 1: searching the Earth because it's easier to just look at
Speaker 1: the Moon.
Speaker 2: These are extrapolations from our stimulations of like what's out
Speaker 2: there in the Solar system, how often do we expect
Speaker 2: stuff to hit the Earth. We can also verify those
Speaker 2: and a lot of those stimulations are built on studies
Speaker 2: of impact craters on the Moon and other objects, the
Speaker 2: Moon just being super close by and like riddled with
Speaker 2: impact craters, and they do all sorts of cool studies
Speaker 2: to see like the age of craters on the Moon,
Speaker 2: by seeing how they're layered, Like if you have a
Speaker 2: fresh then it's gonna have no other craters inside of it,
Speaker 2: whereas an old crater is gonna have lots of other
Speaker 2: small craters within it. And so you can tell the
Speaker 2: age of these craters on the Moon by like how
Speaker 2: many other craters have been layered on top of them.
Speaker 2: It's super cool.
Speaker 1: That is super cool. And if we couldn't do that
Speaker 1: on Earth because that stuff gets covered up too fast,
Speaker 1: is that right?
Speaker 2: No, we do actually have evidence of craters here on Earth,
Speaker 2: though it is more complicated because we have weather and
Speaker 2: we have an atmosphere, and so only the bigger stuff
Speaker 2: leaves evidence. But there's lots of cool ways that people
Speaker 2: have figured out that formations on Earth are due to impact,
Speaker 2: Like there's certain kinds of rock that are only formed
Speaker 2: when you get a super high energy impact, Like shocked quartz.
Speaker 2: This is a structure of quartz that's only formed under
Speaker 2: extremely high pressure. Like you squeeze quartz hard enough and
Speaker 2: it changes its crystal structure and it stays that way
Speaker 2: even after you remove the pressure.
Speaker 1: I like that name shocked quartz. It was like, Oh,
Speaker 1: that's a surprising explosion.
Speaker 2: It sucks. We only actually discovered it recently in nuclear
Speaker 2: testing craters, Like when we started creating these conditions, these
Speaker 2: nuclear bombs, we discovered this shock courts. Then we found
Speaker 2: it in other places on Earth. We're like, oh, wow,
Speaker 2: this must have been a big explosion too, thousands of
Speaker 2: years ago. So it's kind of cool how modern technology
Speaker 2: has enabled us to discover the secrets of the past.
Speaker 1: So many positives to nuclear bomb testing.
Speaker 2: But earlier you were asking whether we have evidence for
Speaker 2: like these sort of smaller collisions in the recent past,
Speaker 2: And maybe my favorite one is in Estonia. This evidence
Speaker 2: in Estonia of an impact that left a crater that's
Speaker 2: like one hundred meters wide, and they think it happened
Speaker 2: in fifteen hundred BC, So this is just a few
Speaker 2: thousand years ago, you know, as we were saying, like,
Speaker 2: we expect one hundred meter wide impactors every few thousand years.
Speaker 2: So do we have any written history of this? And
Speaker 2: this is a great candidate.
Speaker 1: Go on, So is it the ancient Egyptians? They did
Speaker 1: a lot of writing.
Speaker 2: The ancient Egyptians did a lot of writing. But these
Speaker 2: are lakes in Estonia that they're pretty certain were caused
Speaker 2: by an impact. They're like these big circular lakes, and
Speaker 2: they suspect that they may actually appear in Estonian and
Speaker 2: Finnish mythology. So now this is very tenuous, of course,
Speaker 2: but you know, you're wondering, like ancient peoples when they
Speaker 2: saw this thing, what did they think? How they describe it?
Speaker 2: How would it appear in their records? Because they're not
Speaker 2: all doing astronomy. I mean, the ancient Chinese have like
Speaker 2: astronomical records way way back then, but we don't have
Speaker 2: astronomical records from everybody. You, of course, are familiar with
Speaker 2: the famous work of literature of Beowulf.
Speaker 1: I am indeed yeh, because you're the best adaptation ever
Speaker 1: has been written by my husband for children, because who
Speaker 1: didn't want the Beowolf for children version?
Speaker 2: Yes, well exactly, And so spoiler alert, Beowulf dies in
Speaker 2: the end, and he dies the hands of a fiery dragon.
Speaker 2: And in the text they call it the sky Plague,
Speaker 2: a long creature that flew at night over the coast
Speaker 2: of Greystone Cliffs, and in the poem it uses its fiery,
Speaker 2: poisonous breath to scorch and depopulate the countryside. And some
Speaker 2: people think I read a sociology paper that says that
Speaker 2: the description of the dragon and the devastation it causes
Speaker 2: has a lot in common with this impact site in Collie,
Speaker 2: And there are indeed Greystone Cliffs dearby, and so it
Speaker 2: could be that, like some fiery impact left its traces
Speaker 2: in the local mythology and ended up in the text
Speaker 2: of Beowulf.
Speaker 1: WHOA, that's pretty cool.
Speaker 2: And you know this is not scientific, of course, it's
Speaker 2: always very easy to come up with a connection where
Speaker 2: there isn't one. But it's fun to imagine how these
Speaker 2: people might have thought about these huge, devastating impact And
Speaker 2: it's something you can go and visit today. It's called Kali.
Speaker 2: I'm sure, I'm pronouncing it incorrectly kaa l I. And
Speaker 2: it's a site in Estonia with obvious impact craters.
Speaker 1: It's a wonderful work of fiction, particularly if you're reading
Speaker 1: the version written by my husband called be Wolf.
Speaker 2: Exactly, and it may have inspired some of the great
Speaker 2: literature of our civilization. But you don't actually have to
Speaker 2: travel to Estonia to see impact creators. We have an
Speaker 2: awesome one right here in.
Speaker 1: The US, and after a break, we'll tell you where
Speaker 1: you can find it. All right, So, for your listeners
Speaker 1: who reside in the United States, if we want to
Speaker 1: visit our nation's crater, where would we go?
Speaker 2: So in Arizona, there's a place well named. It's called
Speaker 2: Meteor Crater, and it's the side of an impact from
Speaker 2: forty seven thousand BC, so this is like almost fifty
Speaker 2: thousand years ago. But it's not a small site. This
Speaker 2: crater is more than a kilometer across, and it's just
Speaker 2: it's like out there in the desert. It's just like
Speaker 2: huge vast plains and then all of a sudden, enormous
Speaker 2: impact crater. You can see this thing one flying over Arizona.
Speaker 2: It's like very obvious.
Speaker 1: This one. I happened to know is nickel iron if
Speaker 1: it had been ice but it was the same size
Speaker 1: and going the same speed, would it matter or is
Speaker 1: it about size and speed and mass?
Speaker 2: Yeah, great question, It wouldn't matter so much. Like you
Speaker 2: get a similar impact crater, but this one actually left
Speaker 2: a meteor right because it's made of nickel an iron.
Speaker 2: A lot of it survived, like half of it was
Speaker 2: vaporized when it came through the atmosphere and smashed into
Speaker 2: the earth, but huge chunks of it are still lying around.
Speaker 2: They have found chunks of this asteroid before it came
Speaker 2: a meteor and now the chunks of it are called meteorite,
Speaker 2: so we can actually study it.
Speaker 1: Whoa dude like, is this something you can buy online?
Speaker 1: Is there that much of it?
Speaker 2: There's not that much of it. It's very scientifically valuable.
Speaker 2: But it also played an important role in understanding how
Speaker 2: to date geological events. Like one way we figure out
Speaker 2: how old things are, how old a rock is when
Speaker 2: it went from lava to some sort of like crystal,
Speaker 2: is by looking at the uranium inside of it. We
Speaker 2: can use uranium dating to figure out when a rock
Speaker 2: was made.
Speaker 1: And did this have uranium in it or does stuff
Speaker 1: in space have different amounts of uranium.
Speaker 2: This stuff has uranium and it so we can use
Speaker 2: this technique to figure out like when the original chunk
Speaker 2: of stuff was made before it hit the earth. But
Speaker 2: it actually also has a really cool story connected to
Speaker 2: gasoline because when they were trying to figure this stuff out,
Speaker 2: they need to understand where all the lead was in
Speaker 2: the atmosphere. The way this dating system works is that
Speaker 2: when these little crystals form inside the rock, these Zerokon crystals,
Speaker 2: they allow uranium in, but they strongly reject lead. Like
Speaker 2: the chemistry of it says lead is not allowed inside
Speaker 2: these crystals, but uranium decays into lead, and so after
Speaker 2: millions or billions of years, the uranium has transformed itself
Speaker 2: into lead. So the more the lead you find inside
Speaker 2: these crystals, the older the rock is. It's like a
Speaker 2: little clock turning uranium into lead. And you know there's
Speaker 2: no lead to start with because the crystal's repel it.
Speaker 2: So if you can measure the amounts of lead and
Speaker 2: then mounted uranium, then you can tell how old stuff is.
Speaker 2: So the chemist who was figuring this stuff out, he
Speaker 2: was trying to calibrate this and he was discovering, Oh
Speaker 2: my gosh, this lead everywhere. Like every time he tried
Speaker 2: to get a lead free environment just to like calibrate
Speaker 2: his measurements and do some tests, he was totally unable to.
Speaker 2: He had to actually go to Arizona and study a
Speaker 2: piece of this meteorite to try to get like an
Speaker 2: unspoiled piece of rock that didn't have like lead everywhere
Speaker 2: in it. And that, of course was because we had
Speaker 2: lead in our gasoline and we were pumping a huge
Speaker 2: amount of lead into our atmosphere and into our children's mouths.
Speaker 2: There's lead everywhere in the seventies, and he actually led
Speaker 2: the charge to get lead out of gasoline, not just
Speaker 2: because it was making everybody dumber, but also because he
Speaker 2: didn't like having a lead polluted atmosphere. It made it
Speaker 2: harder for him to make these measurements. And he's one
Speaker 2: of the first people to measure the age of the.
Speaker 1: Earth accurately better living through science.
Speaker 2: Yeah, and this meteorite helps us all have a safer
Speaker 2: environment for our children and understand uranium dating.
Speaker 1: Wow. Well, okay, so that's that's a positive thing for once.
Speaker 1: Maybe my children can listen to that chunk. But I'll
Speaker 1: just take out the lead is everywhere a part.
Speaker 2: Well, lead is no longer everywhere, thankfully.
Speaker 1: All right, So let's go even further back in time.
Speaker 1: Presumably we'll talk about an even big asteroid. Where are
Speaker 1: we going to find this one?
Speaker 2: So for the next biggest one, we got to go
Speaker 2: to Kazakhstan. There's a site in zamashin Kazakhstan where an
Speaker 2: impact left a crater fourteen kilometers wide about a million
Speaker 2: years ago.
Speaker 1: Oh okay, so how many hiroshimas would that produce? That's
Speaker 1: gotta be a lot.
Speaker 2: That was a really big impact. Absolutely. They think that
Speaker 2: this is essentially the most recent impact that would have
Speaker 2: produced a huge nuclear winter. Not large enough to cause
Speaker 2: a mass extinction, but large enough to really have a
Speaker 2: serious impact on the Earth's climate for many years. So
Speaker 2: this was a really large event. I mean, fourteen kilometer
Speaker 2: wide crater is like nothing to joke about.
Speaker 1: I'm a little surprised you can have a nuclear winter
Speaker 1: without a mass extinction, but uh, I guess nature's kind
Speaker 1: of resilience.
Speaker 2: By then, the mammals were already in charge, and we'd
Speaker 2: already survived from one big nuclear winter. So you know,
Speaker 2: grow out that fur coat and hunker down for a
Speaker 2: few years we.
Speaker 1: Got this figured out. Now can I buy any of
Speaker 1: this online?
Speaker 2: Actually you can. This one is so big that it
Speaker 2: left fragments everywhere, and people just go like and pick
Speaker 2: up the stuff and sell it online. And some of
Speaker 2: it is really spectacular, Like you can buy this stuff
Speaker 2: called glass foam, which shows you that the original impactor
Speaker 2: was kind of fluffy. It had these like big chunks
Speaker 2: of silicon with huge air bubbles in it. We still
Speaker 2: don't really understand exactly how it was full. And in
Speaker 2: some of these chunks of glass foam you can see
Speaker 2: the melt, like there's unspoiled chunks of glass foam. Then
Speaker 2: the other side of the rock is like melted glass
Speaker 2: foam as it passed through the atmosphere and the plasma
Speaker 2: from the friction actually melted the edge of this thing.
Speaker 2: It's really pretty spectacular. So yeah, you can just go
Speaker 2: online and buy Zamanschite.
Speaker 1: Quite the conversation piece, And you know, there's a lot
Speaker 1: of studio science surrounding this stuff.
Speaker 2: People think it's mystical. I look for some of this
Speaker 2: stuff for sale, and it was advertised as having the
Speaker 2: capacity to quote blast away bad forces and negative people
Speaker 2: who block your life's path. So I'm not sure that
Speaker 2: sounds great big if true, right right, Yeah, so we'll see.
Speaker 2: I'm not going to endorse those claims, but it is
Speaker 2: pretty cool to own a chunk of stuff that came
Speaker 2: from space that like floated around the Solar System for
Speaker 2: a while and then decided to end its days here
Speaker 2: on Earth.
Speaker 1: That is pretty cool, all right. And so now we're
Speaker 1: going to another stan. We're heading to Jikastan. Tell us
Speaker 1: about this one.
Speaker 2: Yeah, So Karakul to Jikastan is the site of a
Speaker 2: disputed impact. It's basically a huge leak. And when people
Speaker 2: first went to space and saw pictures of him from space,
Speaker 2: they were like, hold on a second, look at the
Speaker 2: shape of that thing. That looks like an impact crater.
Speaker 1: And that's because it's very circular.
Speaker 2: It's mostly circular. It's actually got like a big peninsula
Speaker 2: in the middle. Some people think is also part of
Speaker 2: the evidence, because when a rock hits the Earth, it
Speaker 2: can have all sorts of weird seismic bounce backs, So
Speaker 2: some people think it's consistent with a crater. Some people
Speaker 2: are like, nah, you're just imagining it. It's like staring
Speaker 2: at clouds. But If it is an impact crater, it's
Speaker 2: an enormous one. This thing is fifty kilometers wide, and
Speaker 2: they think it probably happened somewhere between five and twenty
Speaker 2: million years ago. So this would have been big news
Speaker 2: a long time ago.
Speaker 1: So why do we have to dispute this? Why can't
Speaker 1: we know for sure? Why can't we look for like
Speaker 1: shocked quartz or tech tight or something.
Speaker 2: Yeah, people have done that, but you know, these things
Speaker 2: aren't easy to find when it's so old. Even the
Speaker 2: big crater like the one we'll talk about next that
Speaker 2: killed the dinosaur, it took a long time before people
Speaker 2: were able to like find the evidence for it. So
Speaker 2: this one was discovered fairly recently, and people are still
Speaker 2: studying and still trying to find those pieces of evidence
Speaker 2: that might be out there.
Speaker 1: All right, all right, so then let's move on to
Speaker 1: the dinosaur killer.
Speaker 2: So probably the most famous impact site on Earth is
Speaker 2: Do you know how to pronounce this one? Kelly? No,
Speaker 2: do you want to try on air?
Speaker 4: Uh?
Speaker 1: Chick kloop?
Speaker 2: All right, We're gonna go with that.
Speaker 1: I think I had a Russian in there. I'm not
Speaker 1: sure that belongs.
Speaker 2: Sorry, this is the one in the Yucatan. You know
Speaker 2: how Mexico basically has that little swoop in it, and
Speaker 2: they think that that's the edge of an impact crater,
Speaker 2: the one that probably took out the dinosaurs sixty five
Speaker 2: million years ago. And this one's enormous, right, it's one
Speaker 2: hundred and fifty kilometers wide, and they think that an
Speaker 2: impactor like ten kilometers wide hit the Earth and left
Speaker 2: that impact crater. One we can see now from space.
Speaker 2: It's pretty amazing.
Speaker 1: But we do have shocked quarts and tech tights from
Speaker 1: this one.
Speaker 2: From this one, we actually do have very specific evidence.
Speaker 2: You can see in the ring around the edge, shock
Speaker 2: quarts everywhere, and they have tech tights, which are these
Speaker 2: little bits of glass that are created during the impact
Speaker 2: and then thrown everywhere that are different from volcanic glass
Speaker 2: and also like don't have the geology of the local environment,
Speaker 2: so they seem very obviously like created from some impactor.
Speaker 2: So here we have very strong evidence that there really
Speaker 2: was an impact sixty five million years ago. People still
Speaker 2: argue about whether it's the reason the dinosaurs went extinct,
Speaker 2: et cetera, et cetera, et cetera, but we're pretty confident
Speaker 2: that it happened, and it would lead to crazy things
Speaker 2: like tsunamis a kilometer high clouds of dust and ash
Speaker 2: and steam, including like twenty five trillion tons of material,
Speaker 2: some of which escaped the Earth and is still floating
Speaker 2: around in the Solar system, like explosive dust from this
Speaker 2: impact is still out there.
Speaker 1: It's crazy, right, that's intense.
Speaker 2: Yeah, So this is the most famous impact crater on
Speaker 2: Earth when people know about the most, but it's actually
Speaker 2: probably not the biggest, the most dramatic impact in Earth's history.
Speaker 1: No, this is the biggest one that I know about,
Speaker 1: and I feel pretty good because I think for the listeners,
Speaker 1: this was the one that most of them talked about
Speaker 1: as well. So which one is bigger?
Speaker 2: So there's an impact crater in South Africa. It's called Redifort.
Speaker 2: I'm sure I'm mispronouncing it. And this one is three
Speaker 2: hundred kilometers wide, so it's twice as wide as the
Speaker 2: one that killed the dinosaurs, Oh my gosh. But this
Speaker 2: one is also much much older. They date this one
Speaker 2: to like two billion years ago, so when life was
Speaker 2: very very primitive, and because it's so old, it's been
Speaker 2: eroded significantly, like mostly it looks like like a partial
Speaker 2: ring of hills and there's a dome in the middle
Speaker 2: of it. You have to sort of like squinch your
Speaker 2: eyes a little bit to even see it.
Speaker 1: Why is there a dome? Why are rolling hills the
Speaker 1: sign of an impact crater. I would think that like
Speaker 1: Ohio being flat would be the sign of an impact crater,
Speaker 1: But I don't associate hills with impact craters.
Speaker 2: Yeah, so the dome is really fascinating. When a really
Speaker 2: big impact or hits the Earth, you don't just get
Speaker 2: a crater for a huge one, you actually get to
Speaker 2: bounce back in the center. The Earth is like a
Speaker 2: big waterbed. Right you hit it, it's gonna bounce back
Speaker 2: a little bit. And so if it's big enough, you
Speaker 2: get this bounce back, this dome in the center. And
Speaker 2: then you also don't just get like one circle. You
Speaker 2: can have multiple rings. It's like the seismic waves travel
Speaker 2: through the Earth and they get frozen in several places.
Speaker 2: It's not actually something that's understood very well. You can
Speaker 2: see it in a few other places around the Solar System,
Speaker 2: impact craters with multiple rings around them, but geologists are
Speaker 2: still trying to understandactly how that happens. But if you
Speaker 2: look at these sets of hills in South Africa, you
Speaker 2: can see that there are multiple rings surrounding this dome.
Speaker 2: So that looks a lot like a huge impact.
Speaker 1: The bounce back that you're talking about. That that's the
Speaker 1: like you said, the lake in Tajikastan has like an
Speaker 1: island in the middle. That's the that's the bounce back
Speaker 1: that you were talking about. Okay, got it, Yeah exactly.
Speaker 2: But because it's so old, it's not really complete anymore.
Speaker 2: Like if you've seen this thing when it was fresh,
Speaker 2: you probably would see like a big dome in the
Speaker 2: middle and then complete rings around it, multiple complete rings.
Speaker 2: But because it's been two billion years since the incident,
Speaker 2: a lot of those have just eroded away. So now
Speaker 2: you have incomplete rings of hills, so partial rings of
Speaker 2: hills around the dome.
Speaker 1: But the good news is that all of this has
Speaker 1: happened in the past half the day. Listeners, it's been
Speaker 1: nice having you here.
Speaker 2: Sleep well, and then you know, as the listeners mentioned,
Speaker 2: maybe the most dramatic incident in Earth history was the
Speaker 2: formation of the moon. Right, we think that the Earth
Speaker 2: was hit by a proto planet billions and billions of
Speaker 2: years ago, which essentially obliterated the entire planet, turned the
Speaker 2: entire surface into lava, which spun out and turned into
Speaker 2: the Earth and the Moon. So this is probably the
Speaker 2: most dramatic event in Earth's history, so dramatic that it
Speaker 2: doesn't even leave an impact crater, right, It just like
Speaker 2: vaporizes the whole planet. But they actually think that they
Speaker 2: found in the Earth's core some evidence of this impact.
Speaker 1: And what is the evidence.
Speaker 2: They look inside the Earth, you know, to like the
Speaker 2: lower most mantle, and they find that some chunks of
Speaker 2: the mantle look a little bit different. It's like a
Speaker 2: different composition, different density, and they think that what they're
Speaker 2: seeing there is mantle from the impact or from FEA
Speaker 2: that made its way down to proto Earth's lower mantle.
Speaker 2: So basically, like the inner core of our planet is
Speaker 2: partially from the inner core of this huge impactor.
Speaker 1: That's incredible.
Speaker 2: Yeah, So the blobs, the density patterns inside the Earth
Speaker 2: show this tell tail sign of this crazy cataclysmic impact,
Speaker 2: even more dramatic than the one that killed the dinosaurs,
Speaker 2: even more dramatic than this one that left these eroded
Speaker 2: rings in South Africa.
Speaker 1: Glad I wasn't there, and I sure do like the mood.
Speaker 2: And as much as these all seem scary, Kelly, these
Speaker 2: all were crucial in life turning out the way that
Speaker 2: it did. Right. If things had happened differently, we wouldn't
Speaker 2: be here. And so we can say thank you to
Speaker 2: the solar system for raining death down on other people's
Speaker 2: ancestors for so many years.
Speaker 1: Yes, thank you for this past, but never again in
Speaker 1: the future. Right, there's no risk of this happening, say,
Speaker 1: I don't know in the next decade or so.
Speaker 2: There's actually an asteroid that's a few hundred meters across
Speaker 2: that's likely to make a close pass in April of
Speaker 2: twenty twenty nine. It's called Apofis, and they predict that
Speaker 2: it's going to come by Friday the thirteenth in April
Speaker 2: twenty twenty nine. But it's just supposed to make a
Speaker 2: clut us.
Speaker 4: But it's not.
Speaker 1: It's not coming on Friday the thirteenth, Are you kidding?
Speaker 2: I am not making that part of that part is real.
Speaker 2: You gotta wonder what it's like to be that scientist,
Speaker 2: like predicting the day it's going to be the closest
Speaker 2: approach and having to be like Friday the thirteenth.
Speaker 1: Or I wonder if you have like a Cassandra syndrome
Speaker 1: sort of thing, like, no one's gonna believe me if
Speaker 1: I say it's coming on Friday the thirteen.
Speaker 2: That's right.
Speaker 1: How close is close when you say it's going to
Speaker 1: make a close pass?
Speaker 2: You know, astronomically speaking, anything that comes like with between
Speaker 2: the Earth and the Moon is pretty close. But that
Speaker 2: doesn't mean it's very dangerous. The Earth is still a
Speaker 2: very small target compared to the vastness of space, and
Speaker 2: it's hard to predict these things years out. So as
Speaker 2: time gets closer, they'll predict it more accurately, and very
Speaker 2: likely we'll all be fine.
Speaker 1: But it's like within the range of error right now
Speaker 1: that Earth could get hit.
Speaker 2: Depends how generous you want to be with range of error.
Speaker 2: There's always systematic uncertainties that haven't accounted for that increase
Speaker 2: the envelope to include the Earth. So yeah, it's possible
Speaker 2: it could hit the Earth. Maybe we should be thinking
Speaker 2: about Plan B Kelly, what do you think?
Speaker 1: I don't know, mostly because I think there's zero chance
Speaker 1: that we could have a self sustaining settlement on Mars
Speaker 1: by twenty twenty nine. So if Earth is going to
Speaker 1: be destroyed in twenty twenty nine. You know, a Mars
Speaker 1: settlement would just be like a couple years behind. Maybe
Speaker 1: you'd buy us a couple more years or something, but
Speaker 1: I doubt it. For more information, check out A City
Speaker 1: on Mars by Kelly and Zach Widersmith.
Speaker 2: I mean, if Earth's civilization is going to be destroyed
Speaker 2: in five years anyway, might as well spend all your
Speaker 2: money on books right now.
Speaker 1: That's exactly well, it's a good deal, even if there's
Speaker 1: not a world ending cataclysm coming.
Speaker 2: Well, it's fun to think about the crazy history of
Speaker 2: the Earth. You know. It hasn't just been bubbling oceans
Speaker 2: and hot tubs and all sorts of cozy times. It's
Speaker 2: been dramatic and cataclysmic. And we can find the evidence
Speaker 2: of those impacts on the surface of other objects in
Speaker 2: the Solar System, but also year on Earth. And I
Speaker 2: love when geologists unearth the evidence here on Earth for
Speaker 2: crazy events in our deep history.
Speaker 1: Way to go, geologists, don't let it happen again.
Speaker 2: It's on you, exactly. We're counting on you, well, all right,
Speaker 2: even if we do nothing about it's knowing how this
Speaker 2: works and knowing the history of the impacts. Maybe you
Speaker 2: will help us figure out how to prevent them in
Speaker 2: the future. Thanks very much everybody for listening, and thanks
Speaker 2: Kelly for joining us today.
Speaker 1: Thanks for having me on the show. It was quote
Speaker 1: unquote fun as always.
Speaker 2: All Right, everyone, tune in next time for more science
Speaker 2: and curiosity. Come find us on social media where we
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