Short Wave - Fulgurite: What A Lightning-Formed Rock May Have Contributed To Life On Earth

Episode Date: March 31, 2021

When lightning strikes the ground, it can leave behind a root-like rock called a fulgurite. Host Maddie Sofia talks with NPR science correspondent Nell Greenfieldboyce about what lightning and its funky rock creation can reveal about the origins of life. To read more of the story, check out Nell's reporting here. You can email us 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 Safai here with NPR science correspondent, Nell Greenfield Boys. Hi now. Hey, Maddie. So listen, I have a question for you. If I asked you what comes to mind when you think of lightning and life, what would you say? Lightning and life. Maybe the Frankenstein?

You know, that lightning got them where they were going. It's alive. It's alive. It's alive. It's alive. It's alive. All right. Yeah, that's what everybody thinks of. But today I have a different story about lightning and life. And this one starts about five years ago in Illinois, not too far from Chicago, in a family's backyard where something strange happened.

There was just like some fire around outside that they saw. And they're like, we don't know what this was because there's just little bits of glass, basically, on the surface in their backyard. So that's Benjamin Hess, and at the time he was an undergraduate at Wheaton College. And the family, you know, whose backyard this was, called up the college's Department of Geology. So my professor readily figured out that that was probably a lightning strike. So they went and dug up that spot in the yard. And down there they found a kind of gray-looking glass that sort of extended down into the earth like a tree root with sort of like branches coming out of the sides. I mean, that's like objectively pretty cool, Mel. So the lightning made this glass root-looking thing. Yeah, absolutely. The lightning's intense heat immediately melted the clay and whatever else was in the soil into a glass,

a kind of foggy, gray-looking glass. And so when the scientists cut it open and looked inside, they found something really surprising, something that's actually linked to the start of life on Earth. So today on the show, what a weird rock can tell us. us about lightning and the origins of life. This is Shortwave, the Daily Science Podcast from NPR. So now, you were telling us about this rock or glass or whatever you called it, created by lightning?

It's a fulgerite. What? What now, now? A fulgerite. It means lightning rock. All right. That's pretty cool. So is this like a rare thing?

Well, Benjamin Hess told me, you know, folgarites haven't been studied that much. He's a graduate student now at Yale University, by the way. And he says, we know from satellites and whatnot that there are over 500 million flashes of lightning a year. So, you know, that's a lot of lightning, although only about a quarter of those flashes are thought to actually hit the ground. So there are 100 to 200 million a year that strike the ground, which is also theoretically 100 to 200 million phogorites being formed a year. Although if you, like, strike a building or strike plants or something, you're not going to make a fuller. Okay. I mean, I don't know. A hundred million folgarites sounds like a lot to me, you know. The thing is, most of them that have been found and collected are ones that were made when lightning

hit like a desert or like a beach. So basically, you know, a wide expanse of sand. Because it's really easy to see like a glass structure sticking out of the sand. But when it strikes soil, it's covered by leaves, detritus, vegetation, or rocks up on obscure mountain tops. It can be a lot harder to notice or find. So I just don't think people have really paid much attention to them before. Okay. So this makes sense. If they're mostly found in, you know, sand, I can see why the backyard strike was unusual. And then you said the scientists tore into that folgerite. Yeah, yeah, they cut it up. They wanted to analyze all the minerals inside just to see what was there. But no, you said they found something unexpected. What is that thing? A mineral called Shreiber site. It's one that's found in some

meteorites. In meteorites. We're going to meteorites now. Okay, all right. Yeah. And here's the thing. For a while now, a lot of scientists have thought that minerals like this one, delivered by meteorites, were really important for the start of life on Earth because they supplied an essential element, phosphorus. It really plays a key role in a lot of the basic cell structures and functions. Like phosphorus makes up the backbone of DNA, the double helix and DNA and RNA, for example. But now, like, why did the Earth need phosphorus for meteorites? Doesn't Earth have its own phosphorus already? Isn't this, like, kind of a basic element? So the early Earth had abundant phosphorus.

You're right. But it was all locked up in rocks, basically trapped in minerals that are really unreactive. They just don't easily dissolve in water. So that phosphorus would just not have been available for the earliest biological molecules. And that created this question of, like, where did the phosphorus that could react and form biomolecules come from? And Benjamin has told me that one answer was meteorites.

So meteorites were really abundant when Earth was forming and in the first billion years or so afterwards. So people thought, aha, it could actually be extraterrestrial phosphorus source that provided the reactive phosphorus needed for life to form. But he found that same stuff in a rock created by a lightning strike. So maybe we don't even need meteorites. Exactly. I mean, that is what he naturally wondered. Like, okay, billions of years ago when life was getting started, could there have been enough lightning striking the ground

to add a decent amount of reactive available phosphorus into the mix? I feel like how much lightning was around billions of years ago is like a tough thing to estimate now. Yeah, I mean, there are a lot of unknowns here. I mean, the Earth just looked completely different. Sure, like how much land was even exposed and available to strike. And what was the land made of? And, you know, it's, there's a lot to consider.

But, you know, we do have climate models that, you know, can sort of try to understand what the composition of the atmosphere would have been like, what the weather might have been like, how much lightning could be generated theoretically. And so Benjamin Hess and some colleagues gave it their best shot. You know, they used those kinds of models and found that from four and a half billion years ago when the Earth formed to around 3.5 billion years ago when life appeared, there were upwards of a billion lightning strikes a year. Okay. So how much usable phosphorus would that have supplied? A lot. Surprisingly a lot. They calculate that when life was getting its start, the amount created by lightning would have been about the same amount delivered by meteorites. Okay. All right. That's definitely. more than I thought, but I have to imagine they're not saying meteorites aren't

important, right? Just that lightning was also zapping us up some phosphorus. Well, not us. I mean, humans did not exist for billions of years. The first life could have gotten phosphorus from lightning. That's what they think. I mean, it's really impossible to say what the source was, and you're right.

I mean, they're not dissing meteorites, right? I mean, meteorites definitely brought a lot. I mean, they're not saying it wasn't a meteorite that brought phosphorus that life needed. Although Benjamin Hess did note that lightning does have some benefits over meteorites. Lightning doesn't destroy an entire 100 kilometer area when it strikes. I mean, fair point, fair point.

So what do other folks think about this idea, like astrobiologists and people who think about the ways life can form? So I called up Hillary Hartnett. She's a professor of biogeochemistry at Arizona State University. And she told me, yeah, I mean, it's kind of cool. It's pretty cool. This idea that lightning could basically release phosphorus from early Earth's rocks. And, you know, she thinks a lot about planets around other stars and what they would need for life. And she says, we hardly know anything about how much phosphorus they might have, but not every planet gets pummeled by meteors.

So it's just nice to have a new way, a kind of different mechanism for life to potentially get one of the ingredients it needs. All right, Nell Greenfield, boys. Thank you for this electrifying little window. into lightning strikes, and all they may have done for us in the past. The next time I see a lightning storm, I will think of you, and a Folgerite. Is that right? Folgerite. Fulgarite.

I think that's how you say it. That's how I've chosen to say it. Okay, now Grie from Wives, I appreciate you. I appreciate you, Maddie. This episode is produced by Thomas Liu, edited by Viet Leigh and Giselle Grayson, fact-checked by Rasha O'Ready. The audio engineer for this episode was Gilly Moon. I'm Maddie Safaya, and this is Shortwave from NPR.