Searching for Signs of Life in Asteroid Impacts

IRA FLATOW: Asteroids slamming into Earth usually conjure up images of death and destruction, a cloud of dust snuffing out life around the globe. It is the stuff of Hollywood disaster movies. And sometimes, actual asteroid impacts can cause real damage. The space rock that exploded over Russia in 2013 was estimated to have released 440 kilotons of energy. It exploded in the air. It blew out windows and injured people on the ground. But maybe asteroids are getting a bad rap. There’s a scientist who has a different take on these impact events and is using, shall we say, an unconventional lab to test out one of his theories. He’s recreated asteroid impacts using a really powerful sort of giant musket.

You intrigued? Well, we sent producer Alexa Lim on a trip out to California to watch one of his experiments.

ALEXA LIM: The first place I meet geologist Peter Schultz is at a gun range, a strange spot for a quiet conversation about science. But this isn’t your usual gun range. There aren’t any paper targets or pistols here. It’s a high tech lab run by the NASA Ames Research Center out in California. And the gun, well, that’s not usual either. It’s bright orange, two stories high, and it fills up a garage that was once a workshop for the Apollo program. Peter and his crew crank the gun into position.

PETER SCHULTZ: This section here, you put in a lot of gunpowder. It explodes, it takes a cylinder like this. The explosion will actually shove this down into a tapered tube. At the end of the paper tube, it’s got hydrogen gas. And that hydrogen gas expands very rapidly. And then that will carry the projectile down into the chamber.

ALEXA LIM: That sounds like a bad idea.

[LAUGHTER]

ALEXA LIM: The shot sounds pretty impressive, but it’s what happens after that’s important. First, there’s an explosion of energy. That creates a curtain of dust and debris. And then there’s the heat, heat so intense it can melt soil, rocks, and anything nearby. And what happens next? Well, that’s the question Peter’s investigating, because under the right conditions, what can emerge from that molten chaos is a certain type of rock known as impact glass. He shows me a sample of it.

PETER SCHULTZ: When you look at this in detail, you’ll see how it looks like a twisted– almost like molasses. It looks like somebody did this in the kitchen. It’s gorgeous.

ALEXA LIM: And this gun range is Peter’s own test kitchen. He wants to see if he can make this stuff himself. So he’s going to shoot a pea-sized bullet, made out of Pyrex at a sandpit, at 11,000 miles per hour. That’s three miles per second. It takes a while to load up a 20 foot gun, just about under an hour. While the crew runs safety checks, Peter fills me in on what set him off on his hunt for impact glass.

PETER SCHULTZ: I’ve been interested in this stuff since third grade. I used to make models of the moon out of plaster. I would use different types of nail heads to simulate different types of craters. But there was the moon, kind of like a mirror of the Earth. But where all of the craters on the Earth?

ALEXA LIM: Isn’t it kind of easy to find a big hole?

PETER SCHULTZ: You’d think it’d be easy to find, right? But it’s not just the hole, it’s filled in. So it’s buried, or you’re seeing it offshore, where it wasn’t offshore before, but it is now, because the oceans rose after the glacial periods and they’ve eaten away the evidence.

ALEXA LIM: So how do you find these craters that have been buried or washed away? You follow the glass. For example, take the Chicxulub meteorite, you know the one that smacked into the Yucatan and took out the dinosaurs, Peter says that impact glass from that collision has been found all the way in present day Colorado. Piece together the trail of impact glass, and it could point to these hidden craters, and help tell the story of these impact events. It was during this hunt for craters back in the early ’90s that Peter got word of a geologist who was investigating a mysterious layer of rock in the Pampas region of Argentina.

MARCELO SARANTES: SARANTES: My name is Marcelo Sarantes. And I’m professor at the National University of La Pumbo.

ALEXA LIM: Marcelo is now a professor and researcher. But 20 years ago, he was a PhD student living near the coast of Argentina. He was studying a group of sea cliffs that contained rocks that looked volcanic, except there was just one problem.

MARCELO SARANTES: The problem is that the nearest volcano was 800 kilometers away. And these pieces were big, 10 centimeters sometimes, even 15 centimeters long. Big pieces to be far away from a volcano.

ALEXA LIM: But Peter had a hunch. He thought these might be impact glass. So he flew to Argentina to meet up with Marcelo.

PETER SCHULTZ: I was using my frequent flyer miles just on this one lark, and I had no clue what I was about to find.

ALEXA LIM: Peter and Marcelo started collecting samples of rocks from all over the area. They eventually went on to identify glass from seven potential impact events. But early on, they stumbled onto something truly strange.

PETER SCHULTZ: We saw something that looked like imprints of grass. And we saw things that looked like maybe grass trapped inside.

ALEXA LIM: They found little blades of grass inside these rocks, rocks that had been scorched into existence.

PETER SCHULTZ: I started thinking, geez, this is really unusual. Maybe we should look at this material that looks like grass and look at it more carefully. This may be a place where you could hide past life inside.

ALEXA LIM: Meteorite impacts can wipe out life in less than a second, but Peter thinks that impact glass may actually preserve life, like a time capsule. It can give a snapshot of what the world was like at that exact moment, the soils, the climate, and even life. Peter digs out a piece of impact glass from Argentina so I can look at it myself under the microscope. I imagined that it would be shiny and smooth, but this rock, it’s dull and full of small holes.

PETER SCHULTZ: And here, if you look inside, you can see that there is these striations.

ALEXA LIM: Yeah, so there’s darker material, and then it’s surrounded by lighter material.

PETER SCHULTZ: That’s grass.

ALEXA LIM: How old is that grass?

PETER SCHULTZ: This graph is 9 million years old.

ALEXA LIM: I can see a single blade of grass. It looks like the outline of a frayed end of an old shoelace. And it’s not an imprint. This is the grass itself, the cellular structure. It’s a relic from our prehistoric past, before the Pampas region was the windblown plains it is today, even before humans evolved. And somehow, the single blade of grass survived the fire and brimstone of an asteroid impact. And now, 9 million years later, I’m here staring directly at it. As I’m looking into this microscope, freaking out about how much history this ancient piece of grass holds, Peter hits me with another one of his ideas.

PETER SCHULTZ: Why not look at this on Mars? If it happened to Earth in this environment, why not Mars?

ALEXA LIM: Meteorites strike Mars and form impact glass there too. Maybe a catalog of past life on the red planet is hiding inside these dull rocks, preserved and waiting for something or someone to pick it up. Peter, Marcelo and their team published a study a few years ago, describing that idea. And their theory on how a piece of grass can survive the extreme heat of an impact, well, it’s kind of like frying a French fry. When the grass is heated quickly at very high temperatures, the water and outer layers take up most of the heat and burn off.

The intersection is shielded from that direct heat and can be left intact, trapped inside. That’s the theory at least, and that’s why we’re staring down the barrel of this two-story gun, to study how this process works. Peter and his grad student, Stephanie Quintana, are busy setting up the target. They smooth out the sandpit until it’s perfectly even. He sprinkles on small pieces of pompous grass, like he’s finishing off a birthday cake.

PETER SCHULTZ: It coat looks like miniature celery. And if all goes well, we’ll see these pieces trapped inside the impact glass created by the energy of the impact.

ALEXA LIM: How are you feeling?

PETER SCHULTZ: Nervous.

ALEXA LIM: Why are you nervous.

PETER SCHULTZ: It might not work. You always worry, will it work? Sometimes it doesn’t. Sometimes the gun fails. It’s an experiment.

ALEXA LIM: Everyone crowds into the control room to watch the impact. Multiple cameras film the sandpit at 25,000 frames per second.

SPEAKER 1: Ready lights are green, paddles in.

PETER SCHULTZ: Oh, we did damage. The shot worked. There’s a small crater off to the side. I don’t know what that’s about.

SPEAKER 1: 5.28 kilometers per second.

PETER SCHULTZ: Sweet. There it goes. There’s a piece of glass. That’s what we got to go find.

ALEXA LIM: After a couple of persistent digs in the pit, Peter finally finds a few shards of freshly made impact glass. Under the microscope, I can see that outline of shoelace like fibers of the trapped grass. The experiment worked. There are still big unanswered questions. How would this process scale up in the real world? Could this capture things like bacteria? And could this even happen in the Martian environment? Peter’s idea that impact glass might preserve ancient life has been 20 years in the making. Decades of gathering clues, piecing together ideas, and exploring his hunches.

PETER SCHULTZ: Now, realize, when you get these clues, these glimpses of things, you need to ask the next question, when you can take off, and jump on a plane, and go down and follow your nose and do it.

ALEXA LIM: And he may get one step closer to testing his idea outside of the lab, and far beyond the plains of Argentina. Because researchers have used data from a NASA orbiter to detect impact glass in craters on Mars. And if Peter’s lucky, one of those craters could be the landing site for the Mars 2020 Rover. Of course, he won’t be able to cash in his frequent flier miles for that trip. He’ll just have to wait back on Earth with the rest of us to find out if his hunch is right. For Science Friday, I’m Alexa Lim.

IRA FLATOW: That was Peter Schultz, a geologist and professor emeritus from Brown University. And Alexa is here to tell us about her trip. Sounds exciting, sounds like fun.

ALEXA LIM: Hey, Ira. Yeah, it was exciting. Well, actually, when you first walk up to it, it looks like a regular garage. They have the corrugated steel door. So it looks like you’re getting your oil changed. But then when you walk in, there’s the giant gun.

IRA FLATOW: Let Me just remind everybody, I’m Ira Flatow. This is Science Friday from PRI, Public Radio International, talking with Alexa about what her trip was like. So there’s this giant– is it lying flat? You said it was two stories long.

ALEXA LIM: It’s two–

IRA FLATOW: It’s flat?

ALEXA LIM: It’s lying flat when you first get in there, but then they can crank it up to two different heights and different degrees, because the most common angle for an impact to come into the earth is 45 degrees. But you know, they’re scientists, so they want different angles. So you can go down or up 15 degrees from there.

IRA FLATOW: On our website, we actually have a video up there, a great video.

ALEXA LIM: Right, yeah, we have– so this, we actually conducted the experiment. And this impact takes about an eighth of a second. So there’s a lot of setup. But it creates this tiny explosion. And we actually have the video. It’s slowed down. It’s 25,000 frames per second. But you can see it. If you look close enough, you can see the fireball. And when you think of the impact, you probably think of a lot of chaos. But Peter, he’s interested in the process that actually happens, like a cone forms, and you can see the swirl of the debris and everything.

IRA FLATOW: I was listening to the story, and he sounded excited himself when that thing shot off.

ALEXA LIM: Yeah, and he’s done this for, I don’t know, 30 years. He’s been the main guy with this gun. And he gets excited every time.

IRA FLATOW: So he’s going to keep doing this until when? And what’s the– until he figures out what’s going on?

ALEXA LIM: I mean, he just retired from Brown. But he’s still working there. He’s still doing research. And he really wants to understand just the process of this. He wants to understand maybe like this impact glass can capture grass on the ground, or maybe it gets flung out, and just kind of picks up stuff as it rolls over.

IRA FLATOW: So it’s sort of a proof of concept, that we could be looking, when we go looking at asteroid remnants, we could find pieces of who knows what’s in them.

ALEXA LIM: It’s possible. This is a peashooter. He’s shooting at like dinner sized plate targets. So how does this scale up. That’s what he wants to know. He needs to know the process more.

IRA FLATOW: It sounds like it was a lot of fun.

ALEXA LIM: Yeah, it was really exciting. And we also have a website that our digital producer, Daniel Peterschmidt built out, and it’s amazing. We have an animated version of this story. And like I said, if you see the video, it’s your moment of zen for the week. It’s hypnotizing.

IRA FLATOW: It’s true, it’s mesmerizing. This object is slamming into it at three miles a second. And it’s up on our website at sciencefriday.com/thelongshot. Thank you, Alexa.

ALEXA LIM: You’re welcome.

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