Daniel and Kelly’s Extraordinary Universe - What’s the largest asteroid impact in Earth’s history?

Episode Date: May 9, 2024

Daniel and Kelly review the most cataclysmic impacts in our planet's history.See omnystudio.com/listener for privacy information.

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On the IHeart Radio app, Apple Podcasts Or wherever you get your podcast Daniel, it's great to be talking to you today. So now I would love for you to go ahead and reassure me that today we're not going to be talking about how scary and dangerous the universe is. Oh, no, no, not at all. Well, I mean, maybe a little bit.

Daniel, that is clearly hedging. I'm going to need more clarity. I mean, we're only going to talk about scary and dangerous family destroying things that already happened in the past. Because we have some way to prevent these scary and dangerous things from happening in the future, like to my children right no comment dude not okay totally totally not okay you got to embrace the danger Kelly that's where the thrill is i i guess i'm pushing through one way or another so let's do this just another show my kids won't listen to

Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I'm looking forward to the destruction of the Earth. I'm Kelly Weiner-Smith, adjunct faculty at Rice University, and I'm looking forward to yet another episode filled with existential dread. You know, in those moments, as the Earth is being obliterated by some huge, impactor. We're going to learn a lot about how the earth is put together and what's inside of it and as all those insides come to the outsides. You know, I'm going to hope that in that moment,

we all stop worrying about the details and we just hug our kids and our dogs and stuff. But I'm sure the physicist will still be collecting data and the economists will be quantifying something and anyway. Well, we are all still live and wondering about the universe. And so welcome to the podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio, in which we do our best to understand the nature of the universe before it comes crashing down on us. We try to cast our minds out into the deepest, darkest reaches of space, and understand what's out there, how does it all work?

We look back into the history of the universe to understand where it all came from, how it all works, and how we got to be where we are. Jorge can't be with us today, but I'm very glad to have with us, Kelly. Kelly, thanks for joining us on another. adventure of dangerous history of the universe. Thanks for having me, despite what it might sound like, I really do enjoy these episodes. And there is a lot of danger out there in the universe. If you cast your telescopes up to the moon, for example, you see that the surface is riddled

with craters. It looks like it's survived a drive-by asteroiding. And if you look even further out into the solar system, you can see crazy things like comets smashing into jupiter creating fireballs the size of earth all this kind of stuff seems to be happening all over the solar system it's a dangerous place epic and that might make you wonder of course how safe is our home here is the plan b strategy for planet earth super important do we need to scramble to get off of earth before something comes and obliterates us one way to answer that question is to think about our cosmic history of course we'd like to know

know what might be hitting us in the future, but the best way to learn about that might be to think about things that have already hit us in the past. Are you going to be making me a question the conclusions from my book? That maybe we do need that plan B and we need to start today because our demise is imminent? Maybe, or you could also look at this history and say, hey, we survived all this stuff. So maybe it's not such a big deal, right? Well, let's see where this goes. And so today on the podcast, we're going to be diving deep into the history of Earth.

To answer the question, What is the largest asteroid impact in Earth's history? You know who has a big impact? You're listeners. Let's hear what they have to say. Thanks very much to everybody who volunteers for this audience participation segment of the podcast. really love hearing your voices. It helps us calibrate the level of the podcast. Plus, we love you guys. We want to hear your voices and we hope you enjoy hearing your own voice

on the podcast. If you'd like to play for a future episode, don't be shy. Write to me to questions at danielanhorpe.com. Here's what listeners had to say. Wasn't this the asteroid that made the dinosaurs extinct or was this a meteor? Was it the planetoid that theoretically smashed into the earth and kind of blew them both apart and became the moon. I saw a model recently that looked so beautiful of kind of this orange fluid, two spheres banging into each other and then the moon forming. So maybe it was that one? I think that there is remnants of an ancient impact crater in Europe somewhere or maybe South America. I can't really remember.

From memory, there was a very large asteroid impact in South America, where that caused one of the dinosaur extinctions, but I can't remember what its name is. Or alternatively, could the moon, the collision that created the moon, be the largest impact that the Earth has ever experienced? I don't know whether that counts as an asteroid, but maybe. The first one that comes to mind is the asteroid that killed the dinosaurs, though I guess that was only like 65 million years ago. Since the Earth has been around for, I think, billions of years, there are probably many more, much larger than that earlier on. I guess another idea might be whatever it was that hit the early Proto Earth and split off into the moon.

Well, the extinction event of the dinosaurs comes to mind up top, but probably there was a larger collision when the planet was still pretty squishy. Probably there was a larger one there. My best guess. So one thing that I thought was interesting about the responses is that I think there was a bit of reticence to answer because folks weren't certain that they had the difference between asteroids, meteors, comets, meteorites, clear. Should we quickly go over, like, which ones and clarify that we're specifically talking about asteroids today? Or do you think we don't need to go over that?

No, I'm always down for exploring the ridiculous naming systems in physics. Or is today's episode just like giant hunks of stuff and we're being general? I mean, from a physics point of view, it doesn't really matter. It's giant hunks of stuff hurtling themselves towards the Earth that created huge explosions and left marks on the Earth surface. But it does kind of matter where those things came from if you want to think about our future prospects and whether, for example, your children will survive. And I do care about that because I'm not a physicist. And so what's the difference between an asteroid, a comet, and a meteor? Yeah, great question.

So an asteroid is basically a small rock that orbits the sun. These things are smaller than a planet, they're like bigger than the pebble-sized objects that are called meteorids. So asteroids are bigger than meteorids, but smaller than planets. And there's also the distinction that planets have to, like, clear the path they're in. So you can have like a bunch of asteroids in like a ring around the sun, and that's not an issue. But nothing in there can basically be a planet, even if it's as big as a planet. So there's a complicated distinction there between like planets, dwarf planets, asteroids. and meteoroids. And then, of course, there's comets.

Okay, but it's mostly all just a matter of size. It's mostly a matter of size. Comets actually come from a different place that come from deeper in their solar system. There's either the Kiper Belt or the Orch Cloud for really distant stuff. And we'll talk about that in a little bit. So that's asteroids and meteoroids and comets. Those are all things out in the solar system. A meteor is something that's burning up in our night sky, something that hits us.

And so that can be an asteroid or a comet. Comet or a little bit of alien space junk or whatever. So a meteor is basically when it hits the Earth. Asteroid and Comet is when it's still out there in space. Got it. Okay. And so the listeners were very interested or very aware of the extinction events where an asteroid wiped out the dinosaurs. And then there was another person who wanted to know if when the early Earth got hit and the moon split off, does maybe that count?

Yeah. The listeners are pretty darn well informed, I'd say. It's almost like they're listening to an awesome podcast regularly that teaches them all about the solar system and the universe. Congrats. And they pass the exam. But you're right that it is important to understand like what's out there in the solar system. Where is this stuff coming from? What are the sizes we expect for things that are raining down on the earth, this death from above?

Okay. So we've done like an overview of definitions. Let's jump into where asteroids come from. and give a little bit more background about where you would find asteroids in particular. And go. So something that you don't often realize when you look up at the night sky is you mostly see stars and planets and you think about the solar system in terms of, you know, like the sun and the planets and maybe a couple of moons here or there.

But the solar system is much, much dirtier than that. You know, there's a whole spectrum of chunks of stuff from the sun down to planets, down to moons, down to much smaller rocks. And as the stuff gets smaller, it becomes much more numerous. So you have like obviously one sun, a few planets, dozens of moons, but when you get to smaller chunks of stuff, asteroids and meteoroids and all that stuff, there's zillions and billions and even trillions of these things. But of course, they're not luminous, right?

They don't glow and they don't reflect as much light because they're small. So you don't mostly see them in the night sky. They're mostly invisible. So the picture I want to paint in your mind is space being filled basically with dark rocks. So I have an important question. Yeah. So in Star Wars, this is how all important questions start. In Star Wars, when they're like trying to navigate around rocks in space, there's just like, they're everywhere and you can't get around them.

If you were out in space and you were to stand on like one chunk of something, would you be able to see other chunks of stuff nearby? Or even though there's lots of them, are they? still like pretty darn spread out or is it like star wars no it's a great question um it's not like star wars it turns out star wars not a documentary and not a reliable way to play in your space mission it's good to know that would have been embarrassing to say that in public but no these rocks are pretty big but they're also very far apart because space is vast especially as you get out into the further reaches of the solar system, the amount of space between these planets gets enormous, right? The volume of the sphere goes as the radius cubed. And so if you're like

another million miles away from the sun, then you create a volume of space, which is much, much bigger than everything inside of it. And so even though there are lots and lots of asteroids out there, remnants from the formation of the solar system that didn't pull together into planets or were disturbed by the gravity of Jupiter, for example, to prevent them from coalescing. There are far enough apart that you can't really have that sort of like exciting space dodgum game. Well, you've dashed a lot of Star Wars related dreams today, but it's important to know. So, all right.

So where do you find most of these? So most of these things are in the asteroid belt, this region between Mars and Jupiter. And that's no accident. You know, as the solar system is forming, it clumps together mostly into the sun and then into the planets. And planets form when you have like a seed of a heavy object, something that can pull stuff together and generate its own gravitational well rather than just getting sucked into the sun. But because Jupiter became so big, its gravity was strong enough that it disrupted the formation of other stuff. And so that's why, for example, these asteroids

near Mars and Jupiter, even though they've been around for billions of years, they haven't like gradually coalesced into one big object. There's lots and lots of them over there. Oh, it's kind of fun to imagine what it would have been like to have another planet out there. There's a lot, Jupiter. Another way you can see the effect of Jupiter on these asteroids is that there's a bunch of asteroids in orbit with Jupiter. If you draw an ellipse for where Jupiter goes around the sun, it's not actually totally empty. There's a whole cluster of asteroids that are leading Jupiter and another cluster that are following Jupiter. They're called the Greeks and the Trojans, these two like different camps of asteroids.

So I thought that planets were specifically. to clear their orbit. Does that? Okay. I know. But Jupiter is huge. So, all right. All right. Go on. So if you were like a lawyer for Pluto, you might raise this objection and say, hey, folks, you've been inconsistent here because planets are supposed to clear their orbit. But, you know, when planets get big enough, then they can actually collect asteroids in these Lagrange points, these points where the sun and Jupiter's gravity balances out in a way that there's like a little gravitational well there for asteroids to collect in. But it's super cool.

We're actually sending a mission to go visit these Trojans pretty soon. Be a lot of fun. Wait, your what? We have a mission that's going to go visit the asteroid belt and one of these Trojans. Ooh, that's exciting. Yeah, we had a whole podcast episode about it, me and you. So check that one out if you're curious about it. But even though you imagine this space to be filled with rocks and some of these are pretty

big, like Series is a whole dwarf planet in this region, it's like 900 kilometers. kilometers in diameter. So that's pretty big. I mean, it's like a 10th or a 13th of the radius of Earth. That's the biggest thing out there in the asteroid belt. But after that, it pretty much falls off. Like half of the mass of the asteroid belt is in just four big mama asteroids. After that, it's a bunch of smaller stuff. And those big mama asteroids are stay input, I hope. Mostly there's stay input. Nasted has a really good job of tracking these folks and thinking about their trajectory. they can predict them out to about a hundred years from now. After that, it's too chaotic with all the influence from Jupiter and Saturn

and the other little bits of the asteroid belt for them to reliably predict where they're going to be. But mostly they know where all the big ones are and they know they're not going to hit us in the next 100 years. All right. All right. That's certainty that I can handle. I'll sleep tonight. All right. So half of the mass is in those four objects and how is the rest of the mass distributed?

So after that, it's lots of times. tiny little ones. And you know, it used to be much more. It used to be that the asteroid belt had like 100 or a thousand times as much mass as it does. But when it's so dense over there, they will eventually bump into each other or even just pull on each other gravitationally and fall out of orbit and then plummet into the sun. So something like 99.9% of the mass of the asteroid belt is gone. It was lost in the first 100 million years of the solar system.

And what's left is a bunch of smaller asteroids. But even if you add it all up together, it's not even that much stuff. It's like four or five percent the mass of the moon. If you like gathered it all together into one big ball. So do we need to worry about like so you said most of it has already fallen into the sun or presumably fallen into Jupiter or something? Is the rest of it something like if Voyager, you know, was going out past Jupiter? Did we have to worry about it running into that stuff or there's just not that much of it

out there? There's not that much of it out there. Yeah. If you pointed a spaceship through the asteroid belt, you'd have a very small. small chance of hitting anything. Nice. That's good to hear. Yeah, so you can put your kids on that spaceship and send them out into space without

worrying about it, Kelly, or without worrying about that one thing. No, no. My kids are staying here. I wrote a whole book on why this is a bad idea. Four years of my life, my kids are staying here. All right. Unless they want to go and then I probably won't stop them. Okay.

Let's take a break. So we've talked about the asteroid belt between Mars and Jupiter. There are other clumps of death from above. And we'll get to that after the break. Imagine that you're on an airplane and all of a sudden you hear this. Attention passengers. The pilot is having an emergency and we need someone, anyone, to land this plane. Think you could do it?

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to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right. So, Daniel, where else are these clumps of death? Where else could they be coming from if they're going to be heading towards Earth? So the asteroids are not really something to worry about. We know where most of the big ones all. as we said and we know where they're going to be the more dangerous things are further out in the solar system out in the Kuiper belt like past Neptune like between 30 and 50 AU is a bunch of frozen ice cubes essentially out past the snow line where the sun is not powerful enough to vaporize ice can still be a big factor in the formation of clumps of stuff and also planets right that's why we call Neptune and Uranus the ice giants so out there in the Kuiper belt they're basically basically a bunch of big frozen snowballs and sometimes some of them fall towards the center of the solar system and those are comets because as they burn their way towards the sun the sun is then boiling stuff off of them making that tail and you maybe already said this and i guess i just didn't understand what why are we more at risk from stuff in the kiper belt than the asteroid belt which is closer are is their movement just more chaotic well for two reasons one is they come from further out so that by the time they make it into our inner neighborhood of the solar system they they're moving faster like they've fallen further into a gravity well and velocity is important because the faster you're moving when you hit the earth the more energy you're depositing

the more the seismic waves the more stuff you toss up into the atmosphere velocity does matter the other reason is that these things are harder to study they're further away so they're harder to spot and they're more erratic they're more susceptible to like passing stars that give them a little gentle tug and nudge them in towards the center of the solar system and they're so many of them out there that we can't possibly track all of them. So they're harder to spot and higher speeds. I don't like it. All right. Well, then you're definitely not going to like the ord cloud. Even further away from the sun is a theoretical cloud of basically icy mini planets. We think there might be trillions of objects in there that are more than a kilometer wide and

maybe even billions that are 20 kilometers wide. You said theoretical? Yes, theoretical. I had assumed we knew this about the Ork Cloud already. This is just like stuff we think. I mean, I guess it makes sense. It's really far away. But we just think it's out there. We're not sure. We think the Ork Cloud is out there.

It makes sense. It's part of all of our simulations. It's been predicted. But we've never actually seen something in the Ork Cloud because it is super duper far away. These things are like one to three light ears from the sun. But it's on a bunch of the illustrations I've seen. Artists, Conceptions. Oh, my God.

I know. No, this is basically an interstellar space. It's not really part of the heliosphere or the solar system, but we do think it's part of the gravitational system of the sun. And there's a lot of stuff out there theoretically. It's much further out than like even where Voyager 1 has gone. And it's so far away and these things are pretty small. So it's hard to spot them directly. Well, Voyager 1 gets there before it runs out of power. It's going to take like 300 years for Voyager 1 to get there. And it basically ran out of power. recently I heard that they stopped hearing from it. So we already know the end of that story. Oh, oh, that's really sad. I can't believe I missed that. Yes. Rest in peace, Voyager one. Exactly. Or float in peace or whatever you say out there in space. The Ork Cloud is theoretical. We're fairly confident it's there. We see indirect hints. And also we think it's a source of the longer period comets because these things are so far away, they take a long time to make it into the inner solar system and maybe impact on a juicy inner solar system planet or not.

And so the shorter period comets probably come from the Kuiper Belt and the longer period comets with even more mass and even more velocity come from the Oort cloud. Have we seen something come closer to us that we think came from the Oort cloud? Well, we've definitely seen a lot of long period comets, these comets that take centuries sometimes to orbit the solar system. And so we think that they originated from the Oort Cloud. So, yeah, we think those things are visitors from the org cloud. And that's one reason why people are excited to, like, go sample comets while they're sending probes out there to grab bits of comets to see, like, what is it like out there in the org cloud?

It'd be awesome to get a sample of the orc cloud that visited the inner solar system. Okay, so we've talked about where these things reside. Let's talk a little bit more about size. So, like, if something that's a meter in diameter comes at us, that's not a problem, right? That's going to burn up. That's not a problem. That's actually kind of awesome. Yeah, it makes a really nice streak in the sky.

It doesn't really do any damage. And also, it happens all the time. You know, space, as we said, is filled with dark rocks. It's not just the asteroids that we've cataloged in the asteroid belt. There's rocks out there all over the place, just floating free, tugged by Jupiter here and there. And that's why we see meteor shower. Right. Every meteor shower are a bunch of rocks hitting the earth. Fortunately, our atmosphere is dense enough to act like a big pillow. And so when they hit the atmosphere, there's friction, they heat up and then they burn up before they hit the ground. And so stuff that's less than a meter in size happens all the time. Yeah, a big flammable pillow. You know, I was when I was researching the spacebook and we were looking at companies that had sort of like out there ways of planning to. make money on space stuff. There was a company that was pitching that they could make you

essentially like asteroid meteor shower sorts of things by like sending mass to space and then having it come down at a certain time and that they could like determine the colors that it would be. Wow. So like, you know, the most epic birthday present, like a pink meteor shower for your kinseniera. But anyway. That sounds like there's no way that could go wrong. Yeah. Absolutely. That doesn't sound dangerous at all. No, no, it's great. It's great. Okay, all right. So we've got a meter and it's beautiful. When does it start becoming less beautiful and more scary?

Yeah, so there's this tradeoff. As they get larger, they get more dangerous. And fortunately, they also get less common. So, for example, stuff that's like a meter wide hits the earth around once per day. And that's not that big a deal. I mean, you can make a big explosion in the sky, and it's the kind of stuff that you hear about. You know, like the turbulence explosion in Russia recently, that's an order of magnitude of a meter size thing. Often this just happens, you know, over the ocean, nobody notices. But occasionally you get a bigger one.

And if you had something like 10 or 20 meters wide, this happens like every 10 or 50 years, then you're starting to get energies comparable to an atomic bomb explosion. Whoa. I feel like we should hear about. that more often. But I guess you said that it happens over the ocean a lot. And so we wouldn't hear about it. Yeah, I had exactly the same reaction. I was like, hold on a second. Nuclear bomb explosions, not that common. You'd think you'd hear about it. This is beyond the news. You'd feel it or something. But these things tend to happen in the upper atmosphere and often over the ocean. So they're just not observed or reported. But with how much like surveillance equipment we

have in space, I would expect you'd see it. But I guess that surveillance equipment, you know, has only been up there since like the 60s or something like that. So we don't have that many years of data. Wow. Okay. That's the numbers you're giving are much more regular than I would have guessed. Let's move on. Yeah. And it's also energy deposited in the upper atmosphere. So it's not like the equivalent of somebody sitting off a nuclear weapon on land or even dropping one in the ocean. And so while the military is definitely tracking these things and we talked about like the network of satellites that the military has when we were talking recently about interstellar asteroids and whether they've hit the earth and whether ovi lobe has actually gathered any sphericals from them so we know the

folks are tracking them it's just not that big a deal it's like getting your shields zapped with lasers but you know your shields are pretty strong okay all right so these explosions are happening in the atmosphere so have we talked about a size yet that could reach the earth and is there a relationship between size and whether yeah there's got to be a relationship between size and whether or not makes it to the earth to impact, right? Yeah, so anything above like 25 or 50 meters will probably make it to the surface. Anything smaller than that is probably going to burn up in the atmosphere. And once you get up to that size, we're talking about a significant amount of energy.

So like a 100 meter size asteroid, if it hits, which is something that happens every few thousand years, we think, has as much energy is 3,000 atomic bombs. Oh my gosh. Okay, so 5,000 years, how long have we had recorded? recorded history. Do we have, and I know, it could have happened in the ocean and we missed it or something, but do we have any recorded histories of this sort of thing happening? We do, we think, and we're going to dig into that in just a minute. Ooh, suspenseful. And then as the things get larger, like a kilometer wide, we're talking about something every half million years.

We think probably five kilometer wide asteroids happen every 20 to 40 million years. And basically anything above five or 10 kilometers is extinction level event. We're talking about creating craters that are like 100 kilometers wide, tossing up enormous amounts of stuff into the atmosphere, obliterating a continent instantly with fireballs. So like an enormous amount of energy. But fortunately, very, very rare. I don't know what to say other than maybe I'm not going to be sleeping tonight.

Maybe I take it back. And so, of course, we're really curious about if this is going to happen in the future and when, But we can also look around the earth for signs that this has happened because it's hit the moon. It's hit basically every surface in the solar system. The earth is not special. The earth also gets hit with this stuff. But only the larger ones make it down to the surface and cause impact craters. So now I'm realizing that I would love to know how we figured out these frequency data that you said.

You know, how do we know that you get a five meter size one almost every five years? And how can we search the Earth for evidence of how often it got hit? Or are you saying that we don't bother searching the Earth because it's easier to just look at the moon? These are extrapolations from our simulations of like what's out there in the solar system. How often do we expect stuff to hit the Earth? We can also verify those and a lot of those simulations are built on studies of impact craters on the moon and other objects. The moon is just being super close by and like riddled with impact craters. And they do all sorts of cool studies to see like the age of craters on the moon by seeing how they're layered.

Like if you have a fresh crater, then it's going to have no other craters inside of it, whereas an old crater is going to have lots of other small craters within it. And so you can tell the age of these craters on the moon by like how many other craters have been layered on top of them. It's super cool. That is super cool. And we couldn't do that on Earth because that stuff gets covered up too fast. Is that right? No, we do actually have evidence of craters here on Earth. Though it is more complicated because we have weather and we have an atmosphere, and so only the bigger stuff leaves evidence.

But there's lots of cool ways that people have figured out that formations on Earth are due to impact. Like there's certain kinds of rock that are only formed when you get a super high energy impact. Like shocked quartz. This is a structure of quartz that's only formed under extremely high pressure. Like you squeeze quartz hard enough and it changes its crystal structure. And it stays that way even after you remove the pressure. I like that name, Shocked Quartz. It was like, oh, that was a surprising explosion.

I'm shocked. We only actually discovered it recently in nuclear testing craters. Like when we started creating these conditions, these nuclear bombs, we discovered this shock quartz. Then we found it in other places on Earth. And we're like, oh, wow. This must have been a big explosion, too, thousands of years ago. So it's kind of cool how modern technology.

has enabled us to discover the secrets of the past. So many positives to nuclear bomb testing. But earlier you were asking whether we have evidence for like these sort of smaller collisions in the recent past. And maybe my favorite one is in Estonia. This evidence in Estonia of an impact that left a crater that's like 100 meters wide. And they think it happened in 1500 BC. So this is just a few thousand years ago.

years ago. You know, as we were saying, like, we expect 100 meter wide impactors every few thousand years. So do we have any written history of this? And this is a great candidate. Go on. So is it, is it the ancient Egyptians? They did a lot of writing. The ancient Egyptians did a lot of writing. But these are lakes in Estonia that they're pretty certain were caused by an impact. They're like these big circular lakes. And they suspect that they may actually appear in Estonian and Finnish mythology. So now this is. is very tenuous, of course. But you know, you're wondering like ancient peoples when they saw this thing, what did they think? How did they describe it? How would it appear in their records? Because

they're not all doing astronomy. I mean, the ancient Chinese have like astronomical records way, way back then. But we don't have astronomical records from everybody. You, of course, are familiar with a famous work of literature of Beowulf. I am indeed, yes. Because your husband, as the best adaptation ever has been written by my husband for children, because who didn't want the Beowulf for children version yes well exactly and so spoiler alert beowulf dies in the end and he dies the hands of a fiery dragon and in the text they call it the sky plague a long creature that flew at night over the coast of gray stone cliffs and in the poem it uses its fiery poison its breath to scorch and depopulate the countryside and some people think i read a sociology paper that says that the

description of the dragon and the devastation it causes has a lot in common with this impact site in Kali. And there are indeed gray stone cliffs nearby. And so it could be that like some fiery impact left its traces in the local mythology and ended up in the text of Beowulf. Whoa, that's pretty cool. And you know, this is not scientific, of course. It's always very easy to come up with a connection where there isn't one.

But it's fun to imagine how these people might have thought about these huge, devastating impact. And it's something you can go and visit today. called Kali. I'm sure I'm not pronouncing it incorrectly, K-A-A-A-L-I. And it's a site in Estonia with obvious impact craters. And it's a wonderful work of fiction, particularly if you're reading the version written by my husband, called Beowulf. Exactly. And it may have inspired some of the great literature of our civilization. But you don't actually have to travel to Estonia to see impact craters. We have an awesome one right here in the U.S. And after a break, we'll tell you where you can find it.

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It's called Meteor Crater. And it's the site of an impact from 47,000 BC. So this is like almost 50,000 years ago. But it's not a small site. This crater is more than a kilometer across. And it's just like out there in the desert. It's just like huge, vast plains. And then all of a sudden, enormous impact crater.

You can see this thing while I'm flying over Arizona. It's like very obvious. This one, I happen to know, is nickel iron. If it had been ice, but it was the same size and going the same speed, would it matter? Or is it about size and speed and mass? Yeah, great question. It wouldn't matter so much like you could have a similar impact crater. But this one actually left a meteor right because it's made of nickel and iron.

A lot of it survived. Like half of it was vaporized when it came through the atmosphere and smashed into the earth. But huge chunks of it are still lying around. They have found chunks of this asteroid before it came a meteor, and now the chunks of it are called meteorite. So we can actually study it. Whoa. Do it like, is this something you can buy online? Is there that much of it?

There's not that much of it. It's very scientifically valuable. But it also played an important role in understanding how to date geological events. Like one way we figure out how old things are, how old a rock is when it went from lava to some sort of like crystal, is by looking at the uranium. inside of it. We can use uranium dating to figure out when a rock was made. And did this have uranium in it or does stuff in space have different amounts of uranium? This stuff has uranium in it so we can use this technique to figure out like when the original chunk of stuff was made before it hit the earth. But it actually also has a really cool story

connected to gasoline because when they were trying to figure this stuff out, they need to understand where all the lead was in the atmosphere. The way this dating system works is is that when these little crystals form inside the rock, these Xircon crystals, they allow uranium in, but they strongly reject lead. Like the chemistry of it says, lead is not allowed inside these crystals. But uranium decays into lead. And so after millions or billions of years, the uranium has transformed itself into lead. So the more lead you find inside these crystals, the older the rock is. It's like a little clock turning uranium into lead.

And you know there's no lead to start with because the crystals repell it. So if you can measure the amount of lead and the amount of uranium, that you can tell how old stuff is. So the chemist who was figuring this stuff out, he was trying to calibrate this and he was discovering, oh my gosh, there's lead everywhere. Like every time he tried to get a lead-free environment just to like calibrate his measurements and do some tests, he was totally unable to. He had to actually go to Arizona and study a piece of this meteorite to try to get like an unspoiled piece of rock that didn't have like lead everywhere in it. And that, of course, was because we had lead in our gasoline. And we were pumping a huge amount of lead into our atmosphere and into our children's mouths. There was lead everywhere in the 70s.

And he actually led the charge to get lead out of gasoline, not just because it was making everybody dumber, but also because he didn't like having a lead-polluted atmosphere. It made it harder for him to make these measurements. And he's one of the first people to measure the age of the earth accurately. Better living through science. Yeah. And this meteorite helps us all have a safer environment for our children. and understand uranium dating.

Wow. Well, okay, so that's a positive thing for once. Maybe my children can listen to that chunk, but I'll just take out the lead is everywhere part. Well, lead is no longer everywhere, thankfully. All right, so let's go even further back in time. Presumably, we'll talk about an even bigger asteroid. Where are we going to find this one?

So for the next biggest one, we've got to go to Kazakhstan. There's a site in Zammachin, Kazakhstan, done, where an impact left a crater 14 kilometers wide about a million years ago. Oh, okay. So how many Hiroshima's would that produce? That's got to be a lot. That was a really big impact, absolutely. They think that this is essentially the most recent impact that would have produced a huge nuclear winter, not large enough to cause a mass extinction, but large enough to really have a serious impact on the Earth's climate for many years. So this was a really large event. I mean, 14 kilometer wide crater is like nothing to

joke about. I'm a little surprised you can have a nuclear winter without a mass extinction, but I guess nature's kind of resilient. By then, the mammals were already in charge, and we'd already survived one big nuclear winter. So, you know, grow out that fur coat and hunker down for a few years. We've got this figured out. Now, can I buy any of this online? Actually, you can. This one is so big that it left fragments everywhere, and people just go look and pick up the stuff and sell it online.

And some of it is really spectacular. Like, you can buy this stuff called glass foam, which shows you that the original impactor was kind of fluffy. It had these, like, big chunks of silicon with huge air bubbles in it. We still don't really understand exactly how it was. formed and in some of these chunks of glass foam you can see them melt like there's unspoiled chunks of glass foam then the other side of the rock is like melted glass foam as it passed through the atmosphere and the plasma from the friction actually melted the edge of this thing

it's really pretty spectacular so yeah you can just go online and buy zamancheid quite the conversation piece and you know there's a lot of pseudoscience surrounding this stuff people think it's mystical i look for some of this stuff for sale and it was advertised is having the capacity to, quote, blast away bad forces and negative people who block your life's path. So I'm not sure. I mean, that sounds great. Big if true, right? That's right. Yeah, so we'll see. I'm not going to endorse those claims, but it is pretty cool to own a chunk of stuff that came from space that, like, floated around the solar system for a while and then decided to end its days here on Earth.

That is pretty cool. All right. And so now we're going to another stand. We're heading to Tajikistan. Tell us about this one. Yeah. So Karakul Tajikistan is a site of a disputed impact. It's basically a huge lake.

And when people first went to space and saw pictures of them from space, they were like, hold on a second. Look at the shape of that thing. That looks like an impact crater. And that's because it's very circular? It's mostly circular. It's actually got like a big peninsula in the middle that some people think is also part of the evidence because when a rock hits the earth, they can have all sorts of weird seismic bouncebacks. So some people think it's consistent with a crater. Some people are like, nah, you're just imagining it. It's like staring at clouds. But if it is an impact crater, it's an enormous one. This thing is 50 kilometers wide. And they think it probably happens somewhere between five and 20 million. years ago. So this would have been big news a long time ago. So why do we have to dispute this? Why can't we know for sure? Why can't we look for like shocked quartz or tectite or something?

Yeah, people have done that. But you know, these things aren't easy to find when it's so old. Even the big crater, like the one we'll talk about next that killed the dinosaur. It took a long time before people were able to like find the evidence for it. So this one was discovered fairly recently. People are still studying and still trying to find those pieces of evidence. It might be out there. All right. All right. So then let's move on to the dinosaur killer. So probably the most famous impact site on Earth is, do you know how to pronounce this one, Kelly? No. Do you want to try on air?

Chick-chlube. All right. We're going to go with that. I think I had a Russian in there. I'm not sure that belongs. Sorry. This is the one in the Yucatan. You know how Mexico basically has that little swoop in it?

And they think that that's the edge of an impact crater, the one that probably took out the dinosaurs, 65 million years ago. And this one's enormous, right? It's 150 kilometers wide. And they think that an impact or like 10 kilometers wide hit the earth and left that impact crater. When we can see now from space, it's pretty amazing. But we do have shocked quartz and tectites from this one? From this one, we actually do have very specific evidence. You can see in the ring around the edge, shocked quartz everywhere.

And they have tectites, which are these little bits of glass that are created during the impact. They're thrown everywhere that are different from the edge. volcanic glass and also like don't have the geology of the local environment so they seem very obviously like created from some impactor. So here we have very strong evidence that there really was an impact 65 million years ago. People still argue about whether it's the reason the dinosaurs went extinct, et cetera, et cetera, et cetera, but we're pretty confident that it happened and it would lead to crazy things like tsunamis a kilometer high, clouds of dust and ash and steam, including like 25 trillion tons of material,

some of which escaped the earth and is still floating around in the solar system. Like explosive dust from this impact is still out there. It's crazy, right? That's intense. Yeah. So this is the most famous impact creator on Earth when people know about the most,

but it's actually probably not the biggest, the most dramatic impact in Earth's history. No. This is the biggest one that I know about and I feel pretty good because I think for the listener, this was the one that most of them talked about as well

so what's which one is bigger so there's an impact crater in South Africa it's called Redafort I'm sure I'm mispronouncing it and this one is

300 kilometers wide so it's twice as wide as the one that killed the dinosaurs oh my gosh but this one is also much much older they date this one

to like two billion years ago so when life was very very primitive and because it's so old. It's been eroded significantly. Like, mostly it looks like a partial ring of hills and there's a dome in the middle of it. You have to sort of like squint your eyes a little bit to even see it. Why is there a dome? Why are rolling hills the sign of an impact crater? I would think that like Ohio being flat would be the sign of an impact crater, but not, I don't associate

hills with impact craters. Yeah, so the dome is really fascinating. When a really big impactor hits the earth, you don't just get a crater. For a huge one, you actually get a bounce back in the center. The earth is like a big waterbed, right? You hit it, it's going to bounce back a little bit. And so if it's big enough, you get this bounce back, this dome in the center. And then you also don't just get like one circle. You can have multiple rings. It's like the seismic waves travel through the earth and they get frozen in several places. It's not actually something that's understood very well. You can see it in a few other places around the solar system, impact craters with multiple rings around them, but geologists are still trying to understand exactly how that

happens. But if you look at these sets of hills in South Africa, you can see that there are multiple rings surrounding this dome. So that looks a lot like a huge impact. The bounce back that you're talking about, that's the, like you said, the lake in Tajikistan has like an island in the middle. That's the bounce back that you were talking about. Okay, got it. Yeah, exactly. But because it's so old, it's not really complete anymore. Like if you'd seen this thing when it was fresh, you probably would see like a big dome in the middle and then complete rings around it, multiple complete rings.

But because it's been two billion years since the incident, a lot of those have just eroded away. So now you have incomplete rings of hills. So partial rings of hills around the dome. But the good news is that all of this has happened in the past. Have a good day, listeners. It's been nice having you. you hear sleep well and then you know as the listeners mentioned maybe the most dramatic incident

in earth's history was the formation of the moon right we think that the earth was hit by a proto planet billions and billions of years ago which essentially obliterated the entire planet turning the entire surface into lava which spun out and turned into the earth and the moon so this is probably the most dramatic event in earth's history so dramatic that it doesn't even leave an impact crater right it just like vaporizes the whole planet. But they actually think that they found in the earth's core some evidence of this impact. And what is the evidence? They look inside the earth, you know, to like the lower most mantle. And they find that some chunks of the mantle look a little bit different. It's like a different

composition, different density. And they think that what they're seeing there is mantle from the impact or from phia that made its way down to proto-earth's lower mantle. So basically like the inner core of our planet is partially from the inner core of this huge impactor. That's incredible. Yeah. So the blobs, the density patterns inside the earth show this telltale sign of this crazy cataclysmic impact, even more dramatic than the one that killed the dinosaurs, even more dramatic than this one that left these eroded rings in South Africa.

Glad I wasn't there. And I sure do like the moon. And as much as these all seem scary, Kelly, these all were crucial. in life turning out the way that it did, right? If things had happened differently, we wouldn't be here. And so we can say thank you to the solar system for raining death down on other people's ancestors for so many years. Yes. Thank you for this past, but never again in the future, right? There's no, there's no risk of this happening, say, I don't know, in the next decade or so. There's actually an asteroid that's a few hundred meters across that's likely to make a close

pass in April of 2029. It's called Apophis. And they predict that it's going to come by Friday the 13th in April 2029. But it's just supposed to make a close pass. Well, it's not it's not coming on Friday the 13th. Are you kidding? I am not making that part up. That part is real. You got to wonder what it's like to be that scientist like predicting the day it's going to be closest approach and having to be like Friday the 13th. Or I wonder if you have like a Cassandra syndrome sort of thing. Like no one's going to believe me if I say it's coming on Friday the 13th. That's right.

How close is close when you say it's going to make a close pass? You know, astronomically speaking, anything that comes like with between the Earth and the moon is pretty close. But that doesn't mean it's very dangerous. The Earth is still a very small target compared to the vastness of space. And it's hard to predict these things years out. So as time gets closer, they'll predict it more accurately and very likely we'll all be fine. But it's like within the range of error right now that Earth could get hit. Depends how generous you want to be with range of error.

There's always systematic uncertainties they haven't accounted for that increase the envelope to include the Earth. So yeah, it's possible it could hit the Earth. Maybe we should be thinking about Plan B, Kelly. What do you think? I don't know. Mostly because I think there's zero chance that we could have a self-sustaining settlement on Mars by 20. So if Earth is going to be destroyed in 2029, you know, a Mars settlement would just be like a couple years behind. Maybe you'd buy us a couple more years or something.

But I doubt it. For more information, check out a city on Mars by Kelly and Zach Wienersmith. I mean, if Earth civilization is going to be destroyed in five years anyway, might as well spend all your money on books right now. That's exactly. Well, it's a good deal. Even if there's not a world ending cataclysm coming. Well, it's fun to think about the crazy history of the Earth. You know, it hasn't just been bubbling oceans and hot tubs and all sorts of cozy times.

It's been dramatic and cataclysmic. And we can find the evidence of those impacts on the surface of other objects in the solar system, but also here on Earth. And I love when geologists unearth the evidence here on Earth for crazy events in our deep history. Way to go, geologists. Don't let it happen again. it's on you exactly we're counting on you well all right even if we do nothing about it's knowing how this works and knowing the history of the impacts maybe will help us figure out

how to prevent them in the future thanks very much everybody for listening and thanks kelly for joining us today thanks for having me on the show it was quote unquote fun as always all right everyone tune in next time For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime.

On the new podcast, America's Crime Lab, every case has a story to tell, and the DNA holds the truth. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hi, it's Honey German, and I'm back with season two of my podcast. Grasias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition?

No, I didn't audition. I haven't auditioned in, like, over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending, with a little bit of cheesement and a whole lot of laughs. And, of course, the great vivras you've come to expect. Listen to the new season of Dacus Come Again on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast.

I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. denials easier complex problem solving takes effort listen to the psychology podcast on the iHeart radio app apple podcasts or wherever you get your podcasts this is an iHeart podcast