2005年NPR美国国家公共电台七月-NASA Space Probe Rea

The Fourth of July fireworks started early. Scientists wearing red-and-blue shirts jumped up and down at the Jet Propulsion Laboratory here in California, upon receiving word from 83 million miles away that a comet had smashed into a NASA probe. The first pictures of the impact show a giant explosion throwing debris 1 over a mile into space. Scientists hope data from the experiment will shed some light on how the planets in our solar system formed billions of years ago. NPR's science correspondent David Kestenbaum joins me now, good morning.

Good morning.



So, pretty big excitement in the control room there.

It's really dramatic because they had pictures going all the way up till the final seconds before the probe was destroyed, so the probe has this camera on it. And you'll see the comet getting bigger and bigger and bigger, and when it's really close, you can actually see it looks somewhat like, it looks like a stone you might pick up off the beach sort of partially 2 weathered but not entirely 3 smooth. And then that's the last picture, because the craft gets vaporized. And but they had a second spacecraft nearby that was watching the whole thing and that's in fact a picture that was just the whole room erupted in applause. It looks like an artist drawing or a painting, you could see the comet and the bottom 3rd of it or so was completely obscured by a giant explosion.



Now I have seen this described, this event described as a speeding bullet managing to hit another speeding bullet. Was it really that hard?

The hard part was that the comet, it doesn't really just go straight, it has these little outbursts where some gas will burst off in one direction. One scientist called them sneezes. And that causes the comet to wander around a bit. It's sort of like a knuckle 4 ball pitch. So the probe that, its job was to get run over to stay in the path of the comet, had actually to do some course corrections to make sure it stayed in the right place.



Now scientists had predicted that this would create a crater 5 some said as small as a house or as big as a football field. The how, what did it turn out to be?

It was clearly a really big explosion; I think they don't quite know the size of the crater at this point. But that's the sort of thing they wanna look at, the idea here is that comets have inside them, material that hasn't literally 6 seen the sun for 4.5 billion years. The comets were put together at the same time as the planets were, but the comets have been really unchanged over all these years. And so, by looking at the shape of the crater and by studying the debris that comes out, they hope to understand what that early material was like. One scientist said that we have a wealth of data here that's gonna take me into my retirement 7.



Well, did the collision change, eh the course of the comet?

The head of JPL said this morning that there is a comet out there in the sky wondering what in the heck hit it, but really it's the probe that got run over and got vaporized. The probe weighs something like 800 pounds, the comet is much bigger, it's 10 miles across. So in the scheme of things were pretty small. And if a comet were heading toward the earth, you'd have to do something pretty dramatic to deflect 8 it. Although one scientist was saying that this, the Impactor created what they call a jet, so a small, a bursting of material out to one side that over the long long period, that would actually deflect the comet slightly, so in the sense this is a sort of thing you could do if you had a comet you caught it early enough and realized that it was eventually gonna in many orbits hit the earth you could deflect it slightly by something like this.



NPR science correspondent David Kestenbaum, thanks very much.

You are welcome.

And you can see pictures of the comet's collision with the space probe at npr.org.