NASA 'Deep Impact' Probe Targets Comet

A space research mission offers some real fireworks for the Fourth of July. The space probe Deep Impact will launch a projectile Monday at Temple 1, a comet NASA has watched for years, and it may be possible to see the collision from Earth. Dave Eicher, editor-in-chief of Astronomy magazine, details the mission for Farai Chideya.

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On July 4th, the spacecraft Deep Impact will launch a projectile at Tempel 1, a comet NASA has been watching for a few years. The collision will help scientists learn more about comets, and it will also make for some stratospheric fireworks on Independence Day. Our correspondent Farai Chideya spoke with Dave Eicher, editor in chief of Astronomy magazine. He described what's going to happen.

Mr. DAVE EICHER (Editor in Chief, Astronomy): This is a very unusual thing. It's never happened before that we've fired a very large bullet that's made largely of copper and aluminum, the size of a washing machine, at a comet that's about--the comet's nucleus is about four or five miles across--to make a big crater. It's very strange. It's something that people have thought about doing for about 30 years, but there are several reasons for doing it, and the main one is to find out: What are comets really made of? We have a pretty good idea that they're made of dirty ice, but beyond that, we don't really know the details of what they're made of.

FARAI CHIDEYA reporting:

Now you mentioned dirty ice, and some people call comets `dirty snowballs.' You're literally talking about ice, as in water. These are big floating icebergs or something?

Mr. EICHER: We are, indeed. We're talking about frozen carbon dioxide, frozen other kinds of gases, but also water ice, and it's thought by most astronomers now that, originally, comets contributed a huge amount of water to Earth and a lot of what is now in our ocean.

CHIDEYA: Now when you talk about early material from the solar system, what sorts of things are NASA folks looking for?

Mr. EICHER: We can't really understand the solar system and how it got going unless we can really understand the origins and the conditions that happened when the solar nebula, this cloud of gas and dust, contracted down and the star turned on and the planets got going. With comets, we're looking not at sort of a rocky impact world that shows us the way things were and it simply hasn't changed because there's not flowing water on it; but we want to see active material, this water, this ice, to smash into the comet and to study the spectra, the spectra of the material that gets shot up in a big plume with this collision. That will tell astronomers a lot, they hope, about what the original early days of the solar system were like.

CHIDEYA: Now final question: This has obviously been planned far in advance to occur on Independence Day. What is this collision going to look like from the Earth, and how should people set about viewing it?

Mr. EICHER: We don't know exactly. We know that the comet is in our sky. Tempel 1 is up in the sky and in the--that's actually a fairly easy thing to see, because it's near Jupiter. The moment that this happens, and for a few minutes afterwards, the comet may brighten, and it may even brighten considerably. Nobody knows. But it's a comet that you need binoculars or a small telescope to see now, for minutes or even for an hour or two after this collision. So if you have a small telescope, even a pair of binoculars, you may be able to see the results from this unique event.

CHIDEYA: All right. Well, I'm sure a lot of people are going to keep their eyes on that.

Dave Eicher is the editor in chief for Astronomy magazine. Thank you for joining us.

Mr. EICHER: Thanks for having me.

CHIDEYA: Farai Chideya, NPR News.

GORDON: This is NPR News.

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