By ALICIA CHANG, AP Science Writer
It sounded like science fiction -- NASA scientists used a space probe to chase down a speeding comet 83 million miles away and slammed it into the frozen ball of dirty ice and debris in a mission to learn how the solar system was formed.
The unmanned probe of the Deep Impact mission collided with Tempel 1, a pickle-shaped comet half the size of Manhattan, late Sunday as thousands of people across the country fixed their eyes to the southwestern sky for a glimpse.
The impact at 10:52 p.m. PDT was cause for celebration not only to scientists at NASA's Jet Propulsion Laboratory in Pasadena, but also for the more than 10,000 people camped out at Hawaii's Waikiki Beach to watch it on a giant movie screen.
"It's almost like one of those science fiction movies," said Steve Lin, a Honolulu physician.
The cosmic smash-up did not significantly alter the comet's orbit around the sun and NASA said the experiment does not pose any danger to Earth -- unlike the scary comet headed for Earth 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.
"A lot of people said we couldn't do this or wouldn't be able to pull it off," said Rick Grammier, the mission's project manager. "It happened like clockwork and I think that's something to be proud of on America's birthday."
Rough images by the mothership that released the probe on its suicide mission 24 hours earlier showed a bright white flash from the comet upon impact, which hurled a cloud of debris into space. When the dust settles, scientists hope to peek inside the comet's frozen core -- a composite of ice and rock left over from the early solar system.
In Darmstadt, Germany, David Southwood of the European Space Agency congratulated NASA and controllers erupted into applause upon impact. "The Deep Impact mission brought the world together in an excellent opportunity to make a new step into the advancement of cometary science," he said.
The European agency was observing and photographing the comet collision 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 ESA's Rosetta mission. "The whole thing was so flawlessly put in place and executed it deserves some respect."
The camera of the Deep Impact probe temporarily blacked out twice, probably from being sandblasted by comet debris, NASA scientists said. Still, the probe -- on battery power and tumbling toward the comet, using thrusters to get a perfect aim -- took pictures right up to the final moments, revealing crater-like features. The last image was taken three seconds before impact.
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.
Scientists had compared the barrel-shaped probe's journey to standing in the middle of the road and being hit by a semi-truck roaring at
23,000 mph. They expect the crater left behind to be anywhere from the size of a large house to a football stadium and between two and 14 stories deep.Soon after the crash on the comet's sunlit side, the mothership prepared to approach Tempel 1 to peer into the crater site and send more data back to Earth. The spacecraft was to fly within 310 miles of the comet before activating its dust shields to protect itself from a blizzard of debris.
Comets are frozen balls of dirty ice, rock and dust that orbit the sun. A giant cloud of gas and dust collapsed to create the sun and planets about 4.5 billion years ago and comets formed from the leftover building blocks of the solar system.
NASA's fleet of space telescopes, including the Hubble Space Telescope, Chandra X-ray Observatory and Spitzer Space Telescope, and dozens of ground observatories recorded the impact.
Deep Impact launched Jan. 12 from Cape Canaveral, Fla., on its 268 million-mile voyage. Scientists say the choice of the mission name was a coincidence and not inspired by the movie.
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