MARY LOUISE KELLY, HOST:
Antarctica is the world's premier hunting ground for meteorites. One reason is that space rocks stand out against the ice.
MARIA VALDES: Although meteorites fall in a random fashion all over the globe pretty evenly, the probability of finding a meteorite is enhanced if the background is a plain color, like snow or ice or sand in the case of the Sahara or the Atacama.
KELLY: Maria Valdes is a cosmochemist with the Field Museum in Chicago. She and three other scientists just spent a month on the icy continent and found five meteorites...
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VALDES: And what is that?
UNIDENTIFIED PERSON: Good chance.
KELLY: ...Including a big one, the size of a cantaloupe, weighing in at nearly 17 pounds. One way they hunted for the space rocks was riding snowmobiles across fields of blue ice.
VALDES: We would get into a V formation with the field guide at the front and two scientists on either side and driving very slowly, 5 to 10 kilometers an hour, just looking back and forth for any black rock against the ice.
KELLY: And if you find something, you just lean down, pick it up, throw it in your sack. How does that work?
VALDES: We try not to touch it just not to contaminate it. But we would call over the others. We had walkie-talkies with us, and we would radio everyone over to come and look. We'd all get down on the ice very close and just visually make a quick judgment right there whether or not it was a meteorite. It was generally pretty obvious.
KELLY: How is it obvious? How do you know a rock is a meteorite and not just a plain old rock you're about to haul back?
VALDES: Yeah, and that's true. There are a lot of terrestrial rocks that do look like meteorites. We call these meteor wrongs. But what we're looking for is a telltale fusion crust in the first place. This is a glassy crust that develops all over the meteorite as it enters our atmosphere at high speeds and melts slightly. And then secondarily, we can also see if it's very heavy for its size, if it's very dense because generally...
KELLY: Right. I was wondering. I mentioned the one that was the size of a cantaloupe and nearly 17 pounds...
VALDES: Exactly.
KELLY: ...Which would be an extremely heavy cantaloupe.
VALDES: Exactly, yeah, because generally, meteorites can be pretty metal-rich. And so they look like they're going to be a certain weight. And then you go to pick them up, and you realize, oh, no, this is much heavier. And what's special about the big one in particular is that although Antarctica gives us most of the meteorites that we have in our collections now, of the 45,000 that have been collected in Antarctica so far, only about a hundred have been larger than the one that we found. Yeah.
KELLY: OK. And I heard you found this - the really big one, the cantaloupe-sized one, on your very last day of hunting. What was that like? Tell me the story.
VALDES: Yeah. You know, we had already had a fruitful experience. We had found four meteorites, about 150 grams or less up until that point. And we were about to go home, pack up our tents and drive the snowmobiles back to base. It was literally the last hour of the last day. And we stumbled upon this huge meteorite just sitting by itself in the middle of a blue ice field. And it really didn't take long at all for us to all determine that this was a meteorite. We got so excited. And we were like, what amazing luck to have this happen just as we were about to give up and go home, you know?
KELLY: Yeah. So everything's gotten sent to this lab in Belgium. They will analyze them. What sort of things are you hoping you might learn?
VALDES: So as a cosmochemist, we are - we're interested in the chemistry of solar system materials. And this is because solar system materials are basically windows into solar system history. They're time capsules that record in their chemical compositions the conditions of the solar system when these rocks formed 4 1/2 billion years ago. They record any movement within the solar system, where in the solar system they derived from, how the planets or rocky bodies that they come from evolved over time. They really have a wealth of information wrapped up in their chemistry. So that's what I'm interested in teasing out from these rocks.
KELLY: Maria Valdes is a cosmochemist with the Field Museum in Chicago. Thanks so much for sharing your discovery with us.
VALDES: Thanks so much.
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