ROBERT SIEGEL, HOST:
Scientists did something today that they have never done before. They successfully landed a probe named Philae - P, H, I, L, A, E - on the surface of a comet.
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STEPHAN ULAMEC: We are sitting on the surface. Philae is talking to us. More data to come.
SIEGEL: Stephan Ulamec is the lander's manager there. And joining us to explain this feat is NPR science correspondent Geoff Brumfiel. And Geoff, start by telling us the latest. What's going on?
GEOFF BRUMFIEL, BYLINE: Well, first, the good news - humanity now has a probe on the surface of a comet 300 million miles from Earth. Its scientific instruments are working and sending back data.
The bad news is we're not entirely sure if it's going to stay there. This probe had harpoons on it that were supposed to fire into the surface of the Comet the moment it landed, securing it, but they never did. And so at an afternoon briefing, Ulamec said that the data indicate the lander may have actually bounced off the comet.
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ULAMEC: The lander may have lifted off again. We touched down and are rebouncing very slowly. So maybe today we didn't just land once, we even landed twice.
SIEGEL: That's very good spin on bouncing. How serious is the situation actually?
BRUMFIEL: Well, it's hard to say. It all depends on the ground that the lander has landed on. Comets are these big balls of ice and dust and rock that orbit the sun. And this particular comet, called 67P, is about the size of Mount Fuji. Now we really didn't know much about it before we got there. We thought it might be sort of a lumpy, potato-y shaped thing. But it's not. It's got cliffs. It's got craters, huge boulders and dunes. It's a spectacular, bleak landscape. If the lander bounced a few feet over, it's no big deal. Hopefully it will settle back on a flat patch and everything will be fine, but it could also bounce into a boulder or bounce off a cliff. If that happens, it's kind of game over.
SIEGEL: Well apart from landing on the comet and staying there, what is the lander supposed to do actually?
BRUMFIEL: The lander is part of what's actually bigger mission called Rosetta. Now, Rosetta is a big spacecraft orbiting the comet, making all sorts of measurements. And this lander was sort of supposed to be Rosetta's hands on the comet. It can do things the spacecraft can't like drill into the surface and image the interior of the comet.
Now, why we care about comets is they're the building blocks of the solar system. They may have even delivered the water that's here on Earth today. So this lander and spacecraft may be able to teach us a lot about our own origins.
SIEGEL: So, bottom line - big success today?
BRUMFIEL: Well, I mean - you know, we don't know just how big yet because the lander communicates with Rosetta which communicates back to Earth, and right now Rosetta's on the opposite side of the comet. We need to wait a few hours to see if we can reestablish communications.
But you know what? I'm going to call it a success. Look, I mean, we've never tried to land on a comet before. We had no idea whether it was going to work or not, and the bottom line is we managed to touchdown. We know that, and we got some data back.
SIEGEL: Well, if it's good enough for you, I'll accept it. Can I just ask you, Geoff? This old image I have my mind that a comet is like a giant snowball - is that just wrong?
BRUMFIEL: I guess the first thing I'd say is it's not just an image you had in your mind. Scientists had this in their mind, too. I think what we're finding out from this mission is that a comet is sort of like a snowball, but it's like a lot of other things, too. It's a much more complicated body than we previously thought, and we're learning more every day.
SIEGEL: NPR's Geoff Brumfiel, thank you.
BRUMFIEL: Thank you very much. Transcript provided by NPR, Copyright NPR.