Short Wave - Iridium's Pivotal Role In Our Past And ... Maybe Our Future?

Episode Date: December 23, 2019

The story of how a father and son team - one a physicist, one a geologist - helped solve a big scientific mystery. What brought the reign of dinosaurs to an end? NPR Science Correspondent Richard Harris tells us how they turned to an element, iridium, for answers. Plus, how iridium could help prevent another potential future global catastrophe. It's our celebration of 150 years of the periodic table of elements. Follow Maddie on Twitter @maddie_sofia. Email the team at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Maddie Safaya here. It's the 150th anniversary of the periodic table of elements, and we have been celebrating by highlighting some of our favorite elements. We did helium, we did aluminum, and now Richard Harris, long-time NPR science correspondent, is going to tell us about his favorite. Yep, eridium. Aridium. I know. I are on the periodic table. Atomic number 77. It's a metal. And that's everything you need to know.

Well, I guess that's it. Oh, wait, wait, wait, wait, I have a few other ideas. I just should tell you, first of all, that iridium is not only one of the rarest elements on the earth's crust. It gives us an important clue about solving a longstanding mystery, one of my favorites about dinosaurs. Love dinosaurs. Oh, what's not to love? I mean, Jurassic Park, good movie, one of my favorites. Mine, too, and I'm still waiting for the sequel, Cretaceous Park. Because that's when the big old dinosaurs went extinct at the end of the Cretaceous, right?

And iridium has provided a surprising clue about how that went down. A little extinction clue. Yes, and iridium doesn't just tell us about mass extinction. It might just possibly play a role in preventing another potential global catastrophe, one that we are spurring on today. Okay, that's a little darker than I expected to go today, but okay, here we go, let's go. Well, darker than extinction of dinosaurs, I don't know. So today on the show, a look at eridium, dinosaurs, extinction, humanities, survival, and more. What else could you want from an episode, Richard?

Not a thing. All right, Richard, we're talking about iridium on today's show. What does this element tell us about dinosaurs and how they went extinct? We're going to go back tens of millions of years ago to start. Yeah, well, can we start in say like 1980? That's what I said, Richard. I said 1980. 1980.

Okay, well, that's actually when an academic paper gets published by a group led by a father and son team from the University of California at Berkeley, Louis Alvarez, the father, a physicist, and, by the way, a Nobel Prize winner, and his son Walter Alvarez, who's a geologist. And they were interested in a specific period of time in Earth's history. It was a transition between two geologic periods, the Cretaceous period and the Paleogene. Good ones. Two good periods. Oh, yeah. So dinosaurs still roamed the Earth during the Cretaceous period, but after that, you don't find any of these dino bones, except in our current dinosaurs' birds. You know what I mean?

I do know what you mean. Yeah, I love thinking of dinosaurs as birds. Me too. Birds as dinosaurs. Same thing. Yeah, it's true. So at any rate, but the Alvarezes weren't actually trying to answer that big, why did the dinosaurs go extinct mystery at that point? Walter and Louis Alvarez were trying to answer just one part of that riddle, which is how quickly that transition between the two periods took place. So Walter tromped off to Italy where there are rock outcrops that were laid down as sediment back at the time of that transition.

Okay, seems like a good idea. Yeah. Why look at those rocks? Well, to get the backstory, I talked to another Berkeley scientist. My name is Paul Rennie, and I'm the director of the Berkeley Geochronology Center. And he said, the secret to figuring out how fast that transition happened involves measuring dust from outer space that's constantly raining down on the earth in tiny amounts. Louis Alvarez, Walter's father, being a physicist, thought, well, you know, we can determine that.

We can make some reasonable assumptions about how much dust is coming in from, extraterrestrial sources. Okay, extraterrestrial, we're talking stuff from outside Earth or the atmosphere. And Richard, can I just say, the fact that somebody thought about measuring cosmic dust to figure out the passage of time 60-some million years ago is objectively awesome. It is. And when you think about the dust coming from asteroids colliding with each other, it's even cooler. And they were looking for particular stuff. And in particular, if we look at an element that's rare on Earth,

but common in meteors. An element that's rare on Earth, but common in asteroids, hmm, guess what we're talking about, Maddie? I'm going to take a wild stab, and I'm going to say iridium. Yeah. Good guess. Excellent guess. Thank you.

Are we done? But what's the role of the dust here? Right. Well, Louis was operating on a reasonable assumption, which is that this dust from meteors rains down on the earth at a more or less constant rate. It's dust, of course, enriched with eridium. So they figured if they could measure how. much eridium had built up in this transitional layer, they would be able to tell how long

it had taken to accumulate. So I'm thinking, sort of figuring out how much snow fell over a period of time, if you know the rate it falls, and how much is on the ground, except this is tens of millions of years ago. Roger, tens of millions of years ago, and the iridium doesn't melt in the sunlight, so it sticks around. You can still see it at 65 or 66 million years later. So at any rate, when they ran those calculations, what the Alvarez's found was stunning.

The results were so extreme that just the passage of a long time would not really explain this. It was many times greater than the amount of aridium in this layer than they expected just from this gradual accumulation. So the conclusion they drew was that there had been some huge pulse of extraterrestrial astrotrial matter. And the obvious conclusion that they quickly came to was that it was a large impact. A large impact. We're talking to asteroid times. Yes, indeed we are, an asteroid. They think the asteroid smashes into the earth, destroying so much of life on Earth.

And throwing up an enormous amount of dust into the atmosphere. The dust itself caused mass extinctions, but it also had iridium in it and it spread around the Earth. So they realized this collision is a big one. And the conditions that resulted, you know, reasonably enough they thought they theorized, killed off these lumbering dinosaurs. You know, Richard, nobody ever thinks about that other life. I feel like it's always dinosaurs, dinosaurs, dinosaurs. I know. You don't get little plastic models of marine four aminifera and you're stalking to you.

Anyway, as I mentioned, this paper was published back in 1980. And back then, a catastrophic end seemed to many scientists pretty far-fetched because, you know, evolution takes place over millions of years. So a lot of scientists were expecting to see gradual changes. And Paul Rennie says when the Alvarez has proposed this meteor, theory, it created quite a stir in the community. It did, yeah. I mean, it was originally not widely accepted, but acceptance sort of came in waves. And the biggest confirmation came when in early 90s there was the discovery of the crater on the northern coast of the Yucatan Peninsula.

A study published in today's issue of Science magazine appears to add weight to a theory that a giant meteor struck the earth 65 million years ago in what is now Mexico. This is the intro to my story that aired in NPR back in 1992. Some scientists see this as evidence that helps prove their theory that the dinosaurs were wiped out by a giant asteroid or comet. But as NPR science correspondent Richard Harris reports, the theories... Oh, little baby Richard Harris science reporter. You've been covering the story for a bit. I have indeed. Actually, back since the early 1980s, but no dinosaur drugs, please. And a really big asteroid could scatter iridium dust globally.

The question was, where's the crater that a huge asteroid like that would make? You just listen to all that joy in your voice, you know? I know. Well, what can be more fun than dead dinosaurs, really? Okay. So this study found the point of impact for the giant asteroid. Yes, it was a crater 110 miles across called Chick-Chilube. And it was created by this asteroid that had a tremendous amount of explosive power, as you can well imagine. Sure. So when these geologists tested the age of the materials from the crater, it turned out to

date very closely to the mass extinction. By the way, dating methods have been recalibrated since that paper, so scientists now say that catastrophe happened 66 million years ago, not 65 million. What's a million years among friends, you know? Yeah, yeah, absolutely. So, I'm not going to. It's a good joke. It's a good joke. Yeah, but the point is, of course, the impact and the dinosaur demise line up perfectly. And for that 1992 story, I talked to Carl Swisher at the Institute of Human Origins, which at the time was in Berkeley. Oh my gosh. Berkeley, Berkeley, Berkeley. I know. The excitement was even much larger when we went across the street. Team Alvarez for the win. Absolutely, yes. For the most part, there's a lot of evidence, but there will always be some skeptics in the scientific community.

And, you know, it's also important maybe to mention that at the same time, about the same time, there was a whole lot of volcanic activity also on the earth. So there's always people thinking one-two punch maybe or something. The asteroid definitely came, but was it the absolute coup de grace for all these dinosaurs. That's still debated. Yeah. Asteroid, touch of volcanoes, a little bit of mix, maybe. So, okay, Richard, Arridium helped us figure out our dinosaur extinction mystery. You mentioned earlier that it could also help us potentially prevent the next global catastrophe. We're not talking another asteroid here. No, we have Bruce Willis for asteroids, if you remember the action movie, Armageddon. No, no, actually, we're talking about climate change.

Ugh, still bad. Okay, climate change. How does Aridium help? Well, what we really need to do to combat climate change is to have a clean fuel that's cheaper than fossil fuels. If we could get such a thing, you know, the world would quickly switch to the cheaper fuel, and we'd stop dumping all that carbon dioxide in the atmosphere. I don't know about quickly, but sure, that's the dream, Richard. Yeah, fair enough. So what's the link between clean fuels and iridium? Well, we really like to capture energy from sunlight and turn that into liquid fuels. Now, plants figured this out long before the dinosaurs were even around.

Photosynthesis! That's right. And, you know, the first step in this process is to split a water molecule. And the problem is this is not so easy to do in the lab. What chemists need is a catalyst. So the chemicals that speed up chemical reactions out there getting stuff done. You got it. And I'm guessing you can see where I'm going with this.

Arridium is a good catalyst. It is a great catalyst for this purpose. And imagine turning sunlight into hydrogen fuel or liquid fuel you could put into an airplane. Of course, there's one itty-bitty problem with this scenario. Eridium, you will recall, is one of the rarest elements on Earth's crust. Because of his scarcity, it's one of the most expensive metals as well. So it does complicate our research. So it's a curveball mother nature throws at us.

That's Duongui Wang. He's a chemistry professor at Boston College, and he's trying to develop an eridium catalyst to make fuel out of sunlight. And he's trying to get around this issue of how little of it we have. Our idea is that we wanted to utilize this catalyst to its maximum. That is, we wanted to make every atom counts. And since iridium is so rare, he wants to make sure every single atom in a catalyst is actually at work speeding up reactions. Even so, it's probably a stretch to think about building an industry around iridium, right?

So his colleagues are also hoping that once they understand how iridium does this magic, they can find something else that will work as a catalyst as well or nearly as well, and ideally something that's abundant on the earth. So, aridium or something like it could potentially help save the day. That's the hope. Richard, you could cover it for another 25 years. Well, I will probably be sitting on my couch, but I hope I will be listening to you, episode 6,212 on shortwave. If I know you, the math is right on that.

Math is pretty close. I took 12 days off per year. Pick it out. I knew it. I knew it wasn't a random number. This episode was produced by Rebecca Ramirez and edited by Viet Le. Shout out to Daniel Shookin and Stacey Abbott for their engineering help. The facts of this episode were checked by Emily Kwong. This has been shortwave from NPR. See you tomorrow.

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