Comet collision with NASA probe wows scientists

PASADENA, Calif. -- When space history books are rewritten, NASA's success at blasting a crater in a comet is sure to be included as more than just a footnote.

It's not the same as putting a man on the moon or blasting average citizens up into space. But like putting robots on Mars, early suggestions are that it captured the public imagination.

NASA's Deep Impact Web site registered nearly 1 billion hits when the space probe collided with comet Tempel 1 late Sunday -- about twice as many hits as the twin Mars rovers got when they parachuted to the Red Planet last year.

The cosmic fireworks from the collision were not red, white and blue and were only visible through telescopes. But their sharp flash of light gave scientists "something to be proud of on America's birthday," said Rick Grammier, the mission's project manager at Jet Propulsion Laboratory.

"This is the first time we had the opportunity to get up close and personal with an ancestor like this," said Richard Berendzen, a professor of astronomy and physics at American University in Washington, D.C. It's an ancestor that might reveal secrets of the solar system.

About 12 hours after the barrel-sized Deep Impact space probe smashed into a comet half the size of Manhattan, scientists showed off dramatic, sci-fi-like images. Photos shot by the probe as it awaited its suicidal collision revealed for the first time the surface of the comet Tempel 1 as it closed in at 23,000 mph.

The close-ups revealed not so much the pickle-shaped comet that scientists originally thought, but one that looked more like a potato, lumpy and pocked. Michael A'Hearn, an astronomer at the University of Maryland and Deep Impact principal investigator, likened it to a muffin or loaf of bread.

The impact released a bright flash followed by a larger one as a plume of trapped gas and debris spewed from the comet's belly into space, backlit by the sun. The cloud blocked scientists' view of the excavated crater and it could be weeks before the dust disappears. Still, scientists were confident they accomplished their mission because they were able to see the crater's shadow in the photos.

"Our experiment went very, very well," said co-investigator Pete Schultz of Brown University, who seemed to be brimming with enthusiasm. "We touched a comet and we touched it hard."

Scientists said the comet appears to have a soft, dusty surface with crater-like features. Trapped ice seems to be below the surface, possibly containing the primordial ingredients of the solar system, Schultz said. Scientists are hoping to get to the core of this rocky, ice-filled structure to learn about the origins of the sun and planets.

A giant cloud of gas and dust collapsed to create Earth's solar system about 4.5 billion years ago, and comets formed from the leftover building blocks of the solar system.

The mission also gives scientists some information about how they might one day stop a comet if one threatens Earth -- but they would need a far larger strike to make a significant dent in turning a comet off-course, A'Hearn said.

Launched on its mission Jan. 12 from Cape Canaveral, Fla., the Deep Impact spacecraft traveled 268 million miles to get the comet in its sights. Late Saturday, it released its copper "impactor" probe and pointed it toward Tempel 1, 83 million miles from Earth. The probe made a 24-hour solo flight toward the comet, heading for a smash-up.

The camera of the probe temporarily blacked out twice, probably from being sandblasted by comet debris, NASA scientists said. Still, on battery power and tumbling toward the comet, using thrusters to get a perfect aim, it took pictures right up to the final moments. The last image was taken three seconds before impact.

Soon after it crashed on the comet's sunlit side, the mothership came within 310 miles of the comet and took pictures of the receding comet as it flew away. More images will be produced by an arsenal of space observatories in the coming days.

The energy produced from the impact was equivalent to exploding five tons of dynamite and it caused the comet to shine six times brighter than normal.

The crash was not visible from Earth except through a telescope in western parts of the Western Hemisphere. But the impact late Sunday was cause for celebration, not only to scientists in mission control, but for the more than 10,000 people camped out at Hawaii's Waikiki Beach to watch it on a giant movie screen.

Brian Spears, a 19-year-old anthropology student and Star Trek fan from San Bernardino, Calif., called the event "really a key point in our whole lives. We might find out the origins of how we came along."

"It's almost like one of those science fiction movies," said Steve Lin, a Honolulu physician.

The cosmic crash did not significantly alter the comet's orbit around the sun and NASA said the experiment never posed any danger to Earth -- unlike the scary comet in the 1998 movie, "Deep Impact."

Scientists at mission control erupted in applause and exchanged hugs as a voice on a speaker proclaimed, "Team, we got a confirmation."

It was a milestone for the U.S. space agency, because no other space mission has flown this close to a comet. In 2004, NASA's Stardust craft flew within 147 miles of Comet Wild 2 en route back to Earth carrying interstellar dust samples.

In Darmstadt, Germany, controllers at the European Space Agency erupted into applause when the collision occurred. "The Deep Impact mission brought the world together in an excellent opportunity to make a new step into the advancement of cometary science," said the ESA's David Southwood.

The European agency was photographing the event with its Rosetta spacecraft, which will attempt to rendezvous with a comet in 2014.

"I had some doubts, quite frankly, but it was quite spectacular and a deserved success," said Manfred Warhaut, who heads the Rosetta mission. "The whole thing was so flawlessly put in place and executed it deserves some respect."

---

On the Net:

Deep Impact mission: http://www.nasa.gov/deepimpact