Comet is hit with a spectacular smack

WASHINGTON — If you could hear sounds in space, it would have been a big bang. NASA's Deep Impact spacecraft slammed into a comet early Monday with such force that the resulting blast of icy debris stunned scientists with its size and brightness.

With the flyby stage of the two-part spacecraft watching from a safe distance, an 820-pound copper-core "impactor" craft smashed into the nucleus of comet Tempel 1 at 23,000 miles an hour, sending a huge bright spray of debris into space.

"The impact was spectacular," said Dr. Michael A'Hearn of the University of Maryland, the project's principal scientist. "It was much brighter than I expected."

Culminating a six-month journey to a point 83 million miles from Earth, the impactor guided itself to a sunlit point near the bottom of the elongated comet where they collided at 1:52 a.m. Eastern time with a force equal to 4.5 tons of dynamite.

"We've touched a comet and we've touched it hard," Dr. Peter H. Schultz of Brown University, another main investigator, said at one of two news conferences at NASA's Jet Propulsion Laboratory in Pasadena, Calif., which controlled the flight.

The purpose of the $333 million mission was to make the most detailed study of a comet to date, striking the mountain-size hunk of ice and rock, and creating a crater from which would spew some of the primal material that makes up its core. The material, to be analyzed using instruments on the flyby craft, may hold clues to the formation of the solar system 4.5 billion years ago.

Depending upon the composition of the comet, scientists speculated that the impact could excavate a crater as large as a sports stadium or as small as a house.

A'Hearn said the blast was so bright that initial images did not reveal the size and depth of the impact crater. Those are to be revealed in later images recorded by the flyby spacecraft when they are received and processed on earth, he said. In some pictures, he said, scientists see a feature or shadow where the crater would be, but it will take a week or more of image processing to be sure.

"Obviously, it was a very big impact," A'Hearn said.

Schultz said he did not want to guess the size of the crater. But he added: "I don't think it's house-sized. I think it's bigger than that."