NASA's Deep Impact Keeps Date with a Comet NASA's Deep Impact spacecraft successfully crashed into Comet Tempel 1 early Monday. Scientists arranged the collision in an effort to learn more about the comet's physical makeup.

NASA's Deep Impact Keeps Date with a Comet

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NASA's Deep Impact mission is apparently a smashing success. Just before 2 AM Eastern time and some 83 million miles from Earth, the comet Tempel 1 plowed into a NASA probe. The collision created a gigantic explosion and loads of data for scientists to puzzle over. NPR's David Kestenbaum reports.


Unlike some other missions, where, say, a landing is preceded by a few scary minutes of silence, scientists knew pretty quickly things were going well. The probe that was supposed to get in the way of the comet stopped sending back pictures, meaning it had been vaporized. Good news to those in the Jet Propulsion Lab in California.

(Soundbite of applause)

Unidentified Man: Oh, my God. Look at that! Oh, yeah!

KESTENBAUM: Within moments a picture appeared on a big screen. It was taken by the main spacecraft cruising nearby and showed the comet looking a bit like a stone or a misshapen dinner roll. And on the bottom, a giant explosion, debris shooting out in all directions. Don Yeomans is a scientist on the mission.

Mr. DON YEOMANS (Deep Impact Mission): Whoo! Look at that! Jeez! And we thought it was going to be subtle. Oh, my Lord.

KESTENBAUM: It's too early to know much in detail about the collision. Scientists on the team have a betting pool on what the crater will look like. Comets are thought of as dirty snowballs, but no one knows how dense the snowball is or if it's covered with ice. A preliminary look at the impact suggests the comet did have a hard surface. Researchers are also eager to analyze measurements of the debris. It had been trapped in the comet for four and a half billion years and is thought to be a clean sample of the stuff that came together to form the Earth and the other planets.

In the Hollywood movie "Deep Impact," scientists try to deflect a comet that's headed for Earth. While this mission could be considered practice for such a day, it's just that, practice. Michael A'Hearn is an astronomer at the University of Maryland.

Mr. MICHAEL A'HEARN (University of Maryland): Any serious attempt to deflect a comet with an impact, however, requires a much, much larger impact than we delivered. The orbital change from our impact is predicted to be so small that it is unmeasurable.

KESTENBAUM: The equivalent of an airplane running into a gnat. In general, the fireworks were hard to see from Earth if you didn't have a big telescope. Carey Lisse has worked on the mission's science team for over six years. He went to the Mauna Kea observatory on Hawaii to watch. We reached him in the control room there, which is atop an old volcano.

Mr. CAREY LISSE (Deep Impact Mission): We were outside, looking up. We had a fantastic sky, dark. You can see the galaxy, you can see hundreds of stars from here. It's one of the best seats on the planet. It was wonderful. We all ran out five minutes before, and we looked and looked. And I was expecting a huge, beautiful flash in the sky, and we would be the first to see it. And we didn't see anything to the naked eye.

KESTENBAUM: Lisse is very impressed, though, by the pictures taken the Impactor before it was vaporized by the comet.

Mr. LISSE: Nobody's ever seen a comet this close up before. There are craters, and there are bright patches. And they're nothing like a snowball or, you know, a loose, lumpy pile of ice. They're fantastic, nothing like we expected.

KESTENBAUM: Another team member, Tony Farnham, watched from an observatory on Kitt Peak in Arizona. Farnham says he was among the last on the team to see how things went because the Web site carrying the pictures was swamped. Fortunately, he had a telescope of his own.

Mr. TONY FARNHAM (Deep Impact Mission): What I saw through the telescope--I was taking a series of three images. We did not see an impact flash at the time of impact. But after that, it brightened gradually.

KESTENBAUM: Images taken from the Hubble telescope show the debris spread over a thousand miles out into space. Carey Lisse, on Hawaii, says it's time to break out the champagne, but he's at 14,000 feet, and alcohol isn't allowed. The air is thin, and it's intoxicating enough just being there. David Kestenbaum, NPR News.

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