July 4, 2005

NASA probe collides with comet in brilliant blast

By Nichola Groom and Nigel Hunt

PASADENA, Calif. (Reuters) - A NASA spacecraft collidedwith a comet half the size of Manhattan late on Sunday night,creating a brilliant cosmic smashup that capped a risky voyageto uncover the building blocks of life on Earth.

"We hit it just exactly where we wanted to," said DonYeomans, a scientist at NASA's Jet Propulsion Laboratory inPasadena.

The spectacular collision, 83 million miles away fromEarth, unleashed a spray of below-surface material formedbillions of years ago during the creation of the solar system.It was the first time a craft came in contact with a comet'snucleus.

"As of now, I think we have a completely differentunderstanding of our solar system," said laboratory directorCharles Elachi. "Its success exceeded our expectations."

The washing machine-sized probe, which performed threefinal targeting maneuvers in the mission's last two hours,crashed into comet Tempel 1's brightest spot right on schedule,snapping images of its rocky terrain up until 3.7 secondsbefore impact.

The craft was vaporized immediately following thecollision, which occurred at 23,000 mph (37,100 kph) -- thespeed it would take to fly from New York to Los Angeles inabout six minutes.

An image of the 10:52 p.m. (1:52 a.m. EDT, 0552 GMT onMonday) crash taken by Deep Impact, the mission's mother ship,showed a brilliant burst of material coming from the bottom ofthe avocado-shaped comet. The probe was released by Deep Impactabout 24 hours before the collision.

"The impact was bigger than I expected, and bigger thanmost of us expected," Yeomans said. "We've got all the data wecould possibly ask for and the science team is ecstatic."

Scientists and engineers in the $333 million mission'scontrol room cheered, applauded, and hugged one another uponconfirmation of the crash.


It could take months to analyze all the data from thecrash, according to Mike A'Hearn, the mission's lead scientist.Three hours after the impact, just 10 percent of the data hadbeen transmitted back to Earth.

"We are just basically starting our work now," he toldreporters early on Monday. "I look forward to a wealth of datawhich will take me to retirement."

Comets are made of gas, dust and ice from the solarsystem's farthest regions. They often show bursts of activity,during which their surfaces crack to create tails of dust.Scientists think comets may have been responsible for firstbringing water to Earth by crashing into its surface.

Experts had disagreed on how dense the comet's nucleuswould be, but the size of Sunday's blast appeared to rule out amore porous composition that would have brought the probe to aslower halt, A'Hearn said.

Images taken by the impactor, showing a comet's nucleus infar greater detail than ever before, revealed several circularcraters on the surface of Tempel 1.

The size of the crater formed by the copper-fortifiedimpactor was not yet known, but had been expected to range fromthat of a large house to a football stadium.

The mother ship, which recorded the impact of the blastfrom as close as 311 miles away, survived the missionunscathed, scientists said.

(Additional reporting by Gina Keating)