Science Friday - Undiscovered Presents: The Holdout. Sept 18, 2018.

Episode Date: September 18, 2018

Since the 1980s, Gerta Keller, professor of paleontology and geology at Princeton, has been speaking out against an idea most of us take as scientific gospel: That a giant rock from space killed the dinosaurs. Nice story, she says—but it’s just not true. Gerta's been shouted down and ostracized at conferences, but in three decades, she hasn’t backed down. And now, things might finally be coming around for Gerta’s theory. But is she right? Did something else kill the dinosaurs? Or is she just too proud to admit she’s been wrong for 30 years? Subscribe to Undiscovered HERE, or wherever you get your podcasts. GUESTS Gerta Keller, professor of paleontology and geology at Princeton James Powell, geologist and author of Night Comes to the Cretaceous: Dinosaur Extinction and the Transformation of Modern Geology (St. Martin's Press) FOOTNOTES Michael Benton reviews the many, sometimes hilarious explanations for the (non-avian) dinosaurs’ extinction. Note: Ideas marked with asterisks were jokes! More in Benton’s book. Walter Alvarez tells his own story of the impact hypothesis in T. Rex and the Crater of Doom. The New York Times interviews Luis Alvarez before he dies, and he takes some parting shots at his scientific opponents. The impact and the Cretaceous-Tertiary boundary were simultaneous according to this paper. Learn more about how volcanoes are major suspects in mass extinctions. Read more about Gerta Keller, the holdout. CREDITS This episode of Undiscovered was reported and produced by Elah Feder and Annie Minoff. Our senior editor is Christopher Intagliata. Original music by Daniel Peterschmidt. Fact-checking help from Robin Palmer. Lucy Huang polled visitors to AMNH about what killed the dinosaurs. Our theme music is by I Am Robot And Proud. Excerpts from All Things Considered used with permission from NPR. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hi, Science Friday listeners. Our science documentary podcast Undiscovered is back for its second season. So over the next few weeks, we'll be sharing a few of this season's episodes. This week, I bet you have a good idea what killed the dinosaurs, right? Well, not so fast. In this episode of Undiscovered, Annie and Ella bring you the tale of a holdout, a scientist who just doesn't buy the common theory and her investigation of an alternate idea. This is Undiscovered.

What killed the dinosaurs? It is one of the great mysteries, the great enduring questions of science. They lived on this planet for 170 million years. Then abruptly, the rain ends. Dinosaurus is doing great. Where'd they go? And one of the first people to field an actual scientific explanation for this was a Transylvanian Baron, Franz Nopsha. It was 1917.

Franz was obsessed with dinosaurs, got into it after his sister found some giant bones near their castle because they lived in one. Right, Barron. And even though France was self-taught, he actually came up with some really great ideas about dinosaurs. But when it came to this very pivotal question, like what the heck happened to them? Not his best work. Franz thought. Dinosaurs. Mm-hmm.

Got too big. Okay. Maybe it was like a pituitary disorder. very close runner-up idea, they stopped doing it. Doing sex? Doing the sex. They suffered a, quote, reduction in sexual function. And to be honest, this is not the worst idea people have come up with. Over the last hundred years, it's just been like open season on the dino question. There was an ophthalmologist who thought that dinosaurs got cataracts and fell off cliffs. Sure. Good PSA to get your eyes checked. Yeah. Could mean the death of your species.

There was an actual legit paleontologist whose theory was that dinosaurs' brains were just too tiny and that therefore they were too stupid to live. The natural endpoint of evolution, right? Fatal stupidity. And I mean, why not, right? If no one has a better theory, like, if no one knows what killed the dinosaurs, go for it. But today we think we finally nailed it. Like if you ask a random person on the street, what killed the dinosaurs?

They'll tell you... A meteorite. A meteorite? A meteorite. A meteorite? A meteorite. A rock. A big rock. From the sky. A meteorite, roughly the size of Manhattan, slams into the Earth 66 million years ago, kills the dinoes.

And most of us? Feeling pretty good about this idea. But not Gerta Keller. There is no way. There is no way that they were killed by an asteroid. or meteorite or whatever. No big rock from space caused their extinction by itself. I'm Ella.

And I'm Annie. Today we've got the story of a holdout. Gerta Keller, a geologist and paleontologist at Princeton. Since the 80s, Gerta's been loudly telling her fellow scientists that they are wrong about something they are pretty sure they're right about. Gerta says she's been ostracized, shouted down at conferences, and still, she has held out. But is she right? Did something else kill the dinosaurs?

Or is she just too stubborn to admit she's been wrong for 30 years? That's coming up on Undiscovered. So for three decades, Gerta's been telling other scientists that they are wrong about what killed the dinosaurs. And I think to understand what kind of person does that, it might help to understand how Gerta handled being nearly driven to extinction herself. What happened is I was shot. I'm with Gerta in her lab at Princeton. She's dressed all in black the way she was the last two times I'd seen her. And she says pretty much everything in this very matter-of-fact voice,

except when she says something really morbid or cynical. Then she laughs. I always thought I would die when I was 23. Because I thought anything after 23 was too old and I didn't want to live. I mean, yeah. Gerda almost did die. Happened over 50 years ago. She hadn't quite made it to 23, but she's getting up there.

She's 22, so close. Left her home country, Switzerland a few years before, and at this point, she was living in Sydney, Australia. And one day, she's driving her Volkswagen bug. She has a friend in the passenger seat. They've just had lunch by the water. And as they're heading back into town, they get on a highway. And it was empty, and I thought it was very strange.

She keeps driving on this weirdly empty highway And suddenly she hears shots And then she sees a man in a blue trench coat And behind him a guy in a suit And they're shooting at each other And her first thought is maybe they're making a movie Except her friend points out, no cameras How can this be a movie?

So how do I know? In Switzerland you don't see people shooting at each other On the street unless it's a movie. Anyway, what she found finds out later is that the man in the blue trench coat had just robbed a bank. And the man chasing him was the bank teller. The police had closed off the highway, trying to contain the shootout, but they'd forgotten this ramp, the one that Gerta got on. So anyway, she's on this highway, and the man in the blue trench coat actually runs up to her car, shoots her, and steals the car.

He shot me from maybe two feet away, and he shot me right in here. She's pointing to her, arm. The bullet goes through her arm, rips through her lungs, but luckily it misses her heart and her spine. After that, she's in and out of consciousness, but she clearly remembers waking up in the hospital and that things are looking bad. I got the last rights and the priest told me I had to confess. And all I could tell him no. You told him no? This was funny. After this Gerta passes out. She comes to and there is that priest again. Last chance, you're going to die. Time to And I say no. And I pass out again, and they evidently they removed him after that.

So GERDA doesn't confess. She doesn't die, which is very GERDA. If she doesn't agree with something, there is no way in hell she's going to go along with it. Anyway, this shooting, it ends up being a turning point for GERDA, Mainly in that she decides she does want to live past 23, but also, growing up, Gerdas family was poor. She'd always been ambitious, but higher education hadn't been an option. And it's not too long after she recovers from getting shot that she really goes for it. She goes to university, gets a degree, actually keeps going until she has a PhD in Earth Sciences from Stanford.

But she's not studying dinosaurs yet. She's studying almost the anti-dinosaur. what I would describe as one of the least exciting organisms, one can study. I'm sorry, Gerta. They're called foraminifera. At her lab at Princeton, Gerta showed me a picture of one of these that she thought was particularly fine looking. It's really cute looking one. I mean, cute, I don't know.

It's beautiful. I'm seeing a pretty nondescript blob with some points. Okay, pointy blob. It's a very good pointy blob. Very useful one. Don't worry, this does become relevant to dinosaurs. I'm trusting you. As you should. Because Girda's blobs, they are very useful.

She specifically studies ancient planktonic forminifera. These are just single-celled organisms with tiny shells, float in oceans. Come in different blobby shapes that you can see under the microscope. So like not your charismatic megafauna? No, but very useful because they tell us what was happening to the planet in different points in its history. So if we scan down layers of ancient searrock, look at the blobs that are embedded in those. different layers. The number and kinds of blobs you see the chemical makeup of their shells in a particular layer, it can tell you if it was warmer or colder, if it was a stressful time

or a good time. And it really helps us to piece together what the Earth was up to in a particular moment in time. And it's what Gurdosal looking at these ancient blobs. That's what got our doubting the big Dino breakthrough of the century. Right. So it's 1980 when the news hits that someone might have actually cracked the case, figured out what killed the dinosaurs. The dinosaurs were among the most successful creatures on Earth. Baby Iroflato on NPR's All Things Considered, January 8, 1980. But suddenly and unexplainedly, they vanished about 65 million years ago.

All kinds of theories have been advanced why. Some say the Earth got too warm, others say too cold. And now Dr. Louis Alvarez, a physicist at the University of California at Berkeley, has come up with a novel theory of his own. Lewis Alvarez, the man with the theory. Imagine your classic 50s scientists, you know, horn room glasses, white dress shirt, that is Lewis, he's a physicist. But he's not just any old physicist. Lewis Alvarez is a Nobel laureate who'd worked on the atomic bomb.

He was actually in the fleet of planes that dropped the bomb on Hiroshima. So he's a big deal. Of course, none of this has anything to do with dinosaurs. But Lewis's son, Walter, is a geologist. And one day, Alvarez Jr. shows his dad this hunk of rock that he picked up in Italy. And running through this rock is this thin red layer of clay. And it dates to the end of the Cretaceous. This is the geologic period when all of the dinosaurs kick the bucket.

And together with some chemists, Alvarez Jr. and senior discover something really interesting about that red line. Arridium. A giant spike of iridium. We found an increase of 30 times in aridium in Italy. And then we looked in Denmark, and there it goes up 160 times. It's an extraordinary thing. And it's extraordinary because eridium, this metal, you don't usually find it in Earth's crust. Like it's super rare here.

But where it's not rare is in space rocks. And so Alvarez Sr. comes up with this idea. And that is an asteroid, about six miles in diameter. bumped into the earth. The asteroid pulverizes on impact, sends up a massive dust cloud. Cut out the light. Cut out the light, then you stop the photosynthesis. Darkness. Plants die. The animals that eat the plants die.

The animals that eat the animals that eat the plants die. At the end of the Cretaceous, the Earth is unrecognizable. About two-thirds of all species just gone. And that includes the dinosaurs. the dinosaurs, except for the ones that live and become birds. And pretty soon scientists all over the world, they're turning up signs of a giant rock impact, signs that they'd missed before. Like in Montana, they find shocked courts, this type of courts that only forms under extreme pressure.

Like when a giant rock hits the earth. Or in Texas, signs of an ancient tsunami. Like when a giant rock hits the earth and sends up massive tidal waves, and so on. And by the late 80s, a lot of scientists are coming around to the impact hypothesis. But a lot of scientists aren't convinced. And that includes Gerta. Gerta at this point is already at Princeton. And she's looking at her forminaforeblobs.

And she's thinking what they're saying, what the Alvarez's are saying, it just can't be true. And here's why. According to the Alvarez's, when the sunlight cuts out, there's a mass extinction all over the world. All kinds of species die, not just the dinosaurs, but big species, small species, microscopes. things like the forminifera, Gerta's blobs. And if the Alvarez's are right, the extinction of all these species is sudden. It's an apocalypse all over the world, happening, geologically speaking, pretty much all at once. But when Gertes scans her layers of rock, she doesn't see a sudden apocalypse.

Her blobs are dying out gradually over an extended period. A gradual extinction, that in itself is a contradiction of what the Alvarez's were saying. But that's not Girda's only objection. Gerta says her blobs, she sees him starting to decline well before the Alvarez's magic, big rock from space hits. And so from where Gert is standing, it seems like, yes, there was something that was killing off a lot of species at the end of the Cretaceous. But could you really say that this killer was a rock from space? If by the time it hits, they are already dying. By 1988, Gerta's ready to unveil her findings, and she finds the opportunity.

a bunch of planetary scientists have organized a conference in Snowbird, Utah. It's a lot of space people who, you know, really dig this threat from space idea. And Gertr decides she's going to head over and, like, you know, show them that they're wrong. I thought they would look at the data and see maybe we have to rethink. Gert admits in retrospect maybe she was a little naive going into this. Just a tad. She remembers throwing up her first slide. It was something like gradual mass extinction, emphasis on gradual.

There was a gasp. These were all impact folks. And people immediately started lining up, even before my introduction was given. And the line keeps growing. Gertr remembers that by the time her talk is over, there were about 30 people lined up. And they are all there to tell her that she's wrong. She doesn't know what she's talking about. She remembers shouting. So somewhere along the line, you probably had a very good science teacher tell you that disagreement is all part of the scientific process. Right? She might not have mentioned the shouting, but in theory, dissent, even impolite dissent, can be part of that push and pull that moves science forward. The philosopher Carl Popper, according to him, the mark of a true scientific theory is not that you can prove it. It's that you could disprove it with the right evidence. And so your job, if you are a scientist with a nifty theory, is to try to knock that theory down, try to test it and test it again, try to disprove it.

And if it's still standing, it might even be true. But now time for some real talk. Just generally speaking, that's not what scientists in a lab or in the field or something. We're not thinking, I'm here, I'm going to, I'm here to falsify some theory. You're trying to explore your own area of research. Jim Powell is a retired geologist who wrote a book about the Dino debates. And he says, look, scientists, they're human beings. They're going to get attached to some ideas.

They're not really going to want to knock down their own. theories. And that's normal. But there is an antidote, which is working in communities. Collectively, scientists will compete with each other, tell each other they're wrong, knock down a weak idea, to the, quote, great disappointment of its proponents and to the advancement of science overall. That sounds pretty good. Did I say that? You did. You know, what I started saying later is, more succinctly, is science is better than scientists. Do you want to elaborate? No. That's it. He does, though.

Science overcomes the weaknesses, the foibles, the mistakes, the biases of individual scientists. Scientific disagreement really did some good work, actually, in the Dino debates. You know, after the Alvarez's came in with their flashy theory, people were trying to either, you know, knock it down if they didn't like it or prop it up if they did like it. Hundreds of papers come out. And that flood of evidence is great for science. But at that conference, in 1988, there was way more hostility than Gerta was expecting. And it wasn't just this conference. By all accounts, these impact debates were among the ugliest chapters in science history.

The tactics were not exactly scientific. They were bullying, a name-calling, destroying careers, threats to destroy careers. And we kind of have to acknowledge this. Part of the problem was Louis Alvarez. This big shot physicist didn't exactly have a time. ton of respect for paleontologists, who up until this point had been the dinosaur experts. And Lewis didn't exactly try to hide how he felt about them. Like he told the New York Times, quote, I don't like to say bad things about paleontologists.

Always a good start to a sentence. Yeah, real promising. But they're really not very good scientists. They're more like stamp collectors. And one geologist who disagreed with Lewis, Lewis called him a, quote, weeks. sister, who no one invited to conferences anymore. This is like third grade stuff. Louis Alvarez was a very strong personality,

and he said and did some things, personal things, that he shouldn't have done. It went beyond Lewis, though. Opponents of the impact hypothesis said that some journals were biased against them, that it got really hard to publish anti-impact papers in some of these journals. And Gertes says that some people were even afraid to speak out against it. And so this wasn't just healthy, Scientific disagreement.

Gerta says this was intimidation. Certainly Gerta Keller was not intimidated. True. For Gerta being told that she's wrong, that is just fuel. It made her... In many ways, invigorated. I wasn't intimidated. It's not my nature. I was sure my dad was right. Gerta was ready to keep fighting.

Like, sure, Team Impact did have this arridium spike. They had that in their corner. But it wasn't a clincher. The anti-impact team, they were still in the game. What Gerta didn't know is the smoking gun that all those pro-impact scientists had been waiting for. It had already been found. That's coming up after the break. Hey, Annie and Ella here.

We're doing a friend raiser. That is what we call a fundraiser where you don't have to give us any money. Which is my favorite kind of razor. So here's how it works. If you like Undiscovered, please tell a friend, fill out a very short form. We'll email your friend a link to Undiscovered. Don't worry, we're not going to spam them. And we'll send you an Undiscovered sticker.

They are blue. They have our logo on them. Looks amazing on your laptop, water bottle, forehead, wherever. So go to Undiscoveredpodcast.org slash stickers. That's undiscoveredpodcast.org slash stickers. For a long time, if you were a scientist who didn't believe that a big impact killed the dinosaurs, you had one thing that you could hold. on to. Kind of a gotcha question, which is if a rock that big hit the earth, where is the

hole? And then in 1990, even that changes, a group of scientists announced they've found a pretty big hole. It's a crater hugging the coast of the Yucatan Peninsula in Mexico. It's over a hundred miles across, enormous, partly on land, partly underwater, buried under deep layers of sediment. The geologists name it Chicksilub, after a small village at the center. And it turns out this Chixilub crater had been in front of us all along. Funny story. I actually vacationed inside the crater a few months ago. Yeah, while working on this story and failed to notice. It kind of clicked in the day before I left. But there were actually geologists who noticed long before 1990. Message somehow got lost on its way to the impact folks.

But anyway, in 1990, it all clicks together. And so Walter Alvarez and some others go down to Mexico and find a nice, rocky outcrop that tells the very story that they've been telling all along. Big impact, big tsunami, spike in iridium. It is all there. That was actually the time I thought, okay, so they are probably right. I figured, okay, if they have the crater and they have the iridium, fine. That was when I thought I would get out of it. Get out of?

out of the mass extinction business and go on to something else. Gerta give up. That did not last long. So I called Walter. Alvarez, the son. And I said, congratulations. It's a very nice paper, and it looks like you nailed it. Basically, you did great, congratulations, but maybe she should take a look for herself.

They describe a particular cross-section of rock. Could he give her the coordinates? And he said, no. Walter declined to talk to us for this story, but Gerta already had a reputation at this point, depending on who you talk to, a reputation as stubbornly wrong. So if Walter did refuse to give her the coordinates, maybe that's why. Still, even without the coordinates, Gerta just goes. She actually heads out to Mexico.

She takes a couple of collaborators with her, and they just go to the general area, where they know this rock is supposed to be. But this is a big area, so they're just wandering around. all day. It's getting late. They're not finding this piece of rock. But they do keep seeing these men on horseback with guns. And they're kind of freaked out. But eventually, they realize, like, they are not going to find this thing without help. So Gerta approaches one of the men, and she shows him this picture and says, you know, have you seen this rock? And he says yes. It's just down there. It was just a few hundred yards away. Later, she finds out that the men with guns

regarding a marijuana plantation just behind the hill. So Gerta has her rock samples. Later, she analyzes them in her lab back home. And she doesn't see what the other side is saying. Her interpretation is entirely different. It actually changes a lot over the years. But today she says, okay, there was an impact. But the timing is wrong.

She says this area in Mexico, it shows the impact happened almost 200,000 years before the end of the Cretaceous. So it can't be their smoking gun. But in the 90s, it seems like the tide has turned against Gerta. They are done with her naysing. They have their crater. And in 1994, there's another big conference organized by space folks in Houston. And most people there seem to be fully on the impact side.

Every time someone went up, they would say, I believe in the impact. They just go up and say, hello, I believe in the impact. Yes. And then people would wildly clap and stamp. It was just loud and hitting the table in front of them. Grida had a few allies at this conference, but for the most part, she felt like a pariah. It was depressing. But she still does not give up. She does not get out of the extinction business. And I asked her like, why? How do you keep going? I don't know. honestly I've thought about it myself many times why and my husband has often told me forget it go moves on to something else why are you going through this you can't change anybody's

mind which is all true and I've thought about it many times and then I still couldn't do it I'm just driven to find out for myself what really happened. Which is admirable and what scientists are supposed to do. But other people like Jim Powell, who wrote the book on the Dino Debates, they say we know what really happened. A meteor killed the dinosaurs. The evidence just kept coming in after they found the Chicksilube Crater, and it's still coming in today.

In 2013, a team of Berkeley scientists used improved methods. to compare the age of the impact and the age of the mass extinction. The age of the Chixilob impact, they found to be 66.038 million years. The age of the mass extinction was 66.043 million years. And these are the same coincidence to the realm, out to the limit, out to impossibility. Maybe Louis Alvarez was a bully. But Jim says it's ultimately the scientific evidence that did win this debate. It was an intimidation.

It was facts. So now we know what killed the dinosaurs? A big rock from space. Or is it? So you might not know it from reading a headline like this one from 2010, quote, a theory set in stone. An asteroid killed the dinosaurs after all. But over the decades, even as scientists were accumulating all this evidence in favor of the rock from space theory,

another hypothesis has also been steadily gaining ground. Volcanoes. So in India, there's this volcanic region called the Deccan traps. And near the end of the Cretaceous, it starts erupting. And these aren't your typical volcanic eruptions. It's not a mountain blowing its top. It's more like the earth cracked open across thousands of miles and began spewing lava and gases.

And this goes on for hundreds of thousands of years. Volcanoes killed the dinosaurs. That's the idea, Gerdes. supports now. Volcanoes could actually do a ton of the same stuff that a big rock from space could do. Like, block out the sun? Check. Errupting volcanoes create sulfate aerosols that can block out the light and cause global cooling. And when those aerosols settle, you're left with a lot of CO2, which could cause global warming. So climate change, that's something a lot of people say a meteorite would also cause. Even the impact team's original clue, that big eridium spike, in 1983, the kill

until a way a volcano starts erupting. It's the same one that's active now. And what do scientists discover coming out of it? Arridium. But here's the thing that really got me. Of the five big mass extinctions that have happened in Earth's history, three of those coincide with very intense volcanic activity. And there's evidence to suspect volcanism was involved in all of them.

Okay, so we're a couple of minutes ahead of schedule, so just feel free to chat to your neighbor. Last fall, I went to see GERDA speak at a conference. It was the Geological Society of America, and she was there to talk about her latest data on the deck and traps. And I was really curious, after hearing Gerta described the kind of reception she got in the 80s and the 90s, I was curious what kind of reception she'd get today. So the next presentation is Go to Keller.

When it's Gertes turn to talk, she looks super confident. She strolled right up to the front of the room. Instead of taking the stairs, one might say the easy way for a 72-year-old to get onto a stage. Gerta jumps onto the stage, which I'd say was at two or three feet high. And she tells the audience about all the work they're doing with Mercury. Turns out that's a very good signature of volcanic activity, how they're really trying to map out the history of the deck and traps.

As far as I can tell, sitting in the crowd, it's all pretty smooth sailing. You know, no hostile lines, no booing. And it's over. Thank you. Thanks very much, Gerta. There are steps outside. But she jumps off the stage instead. I hope I can do that.

We don't have time for questions. Gerta isn't exactly popular these days. I was at this conference and when I told other people about the story I was working on mentioned Gerta's name. I got some pretty deep, exasperated sighs. Clearly she still has a reputation. At the same time, she's not exactly a pariah or an outsider either. Maybe people are just used to her now.

I think it has something to do with the fact that the idea that she's backing now, volcanoes as dinosaur killers, it's gaining momentum. Not that the impact hypothesis is in any way, shape, or form out of the picture. No. And of course, it doesn't have to be one or the other necessarily. It's not volcanoes versus big rock. Some people think it was a one-two punch. A lot of volcanism, weakened ecosystems. And then you have this meteorite delivering the knockout blow.

In 2015, a team published a paper saying maybe the meteorite even accelerated the volcanic activity. At the geology conference, I decided to poll people to see what they thought. You know, where are we at now? What do people believe? The meteor is the meteor. Maybe that is one of the causes. I don't think it was just the asteroid. Volcanoes, definitely volcanoes. I don't think that decking volcanism wasn't involved.

I think it is the collusion of multiple effects. Combined effects. Multiple factors. Agreed. Is that good? They seem to be in the mood for compromise. Most of them were like, yeah, meteor, obviously. But yeah, volcanoes, they probably mattered too.

So a little bit of this, a little bit of that. But for GERDA, no deal. This whole one-two punch business, she told me it's basically the last gasp of a dying theory, the impact hypothesis. Meteor just not a big player. And Jim Powell, even though he thinks Gerta is dead wrong on this. He spoke really highly of her and of all those pain. paleontologists who fought this theory tooth and nail.

He says even if they're wrong, they helped. Their efforts wound up making the theory stronger. They made the Alvarez and others go back and look again, look for more evidence, until finally the whole thing was stronger than it was at the time of the Alvarez theory, thanks in part to this resistance to the theory. And I think this may be something unusual about. science is that criticism makes it stronger. If it doesn't kill it, it makes it stronger.

Pretty sure Gerta would agree with that. Undiscovered is reported and produced by me Ella Fetter. And me, Annie Minoff. Our senior editor is Christopher and Taliatta, and our composer is Daniel Petersmith. Special thanks this week to Lucy Wong. And as always, I Am Robot and Proud wrote our theme. We had fact-checking help from Robin Palmer. To learn more about this story and what killed the dinosaurs, visit Undiscovered podcast.

And if you want to read Jim Powell's book, it's called Night Comes to the Cretaceous, Dinosaur Extinction, and the Transformation of Modern Geology. And if you want to hear more episodes, subscribe to Undiscovered wherever you get your podcasts. Finally, thank you to everyone at Science Friday and WNYC Studios, and to MicroGal and everyone who left us really nice iTunes reviews welcoming us back. Thank you. Thank you. It's really good to be back.

See you next week. One of important things actually that I came away with is I'm not afraid of dying. It was actually nice. All this floating around up there and before I... There were weird things going on.