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NASA probe carrying comet dust to return to Earth

Posted on: Wednesday, 11 January 2006, 12:58 CST

By Nichola Groom

LOS ANGELES (Reuters) - A space capsule with samples of comet dust is set to parachute into the Utah desert on Sunday, capping a seven-year mission that scientists hope will give them clues about the origins of the solar system 4.5 billion years ago.

The spaceship Stardust's 2.9 billion mile round-trip mission took it halfway to Jupiter to catch particles from comet Wild 2 two years ago.

On Sunday, the ship will remain in space while a 100-pound (45 kg) capsule loaded with comet dust returns to earth and lands at the U.S. Air Force Utah Test and Training range at 3:12 a.m. local time (5:12 a.m. EST or 1012 GMT).

If the night is clear, the descent should be visible from the ground in northern California, Oregon and Nevada.

It is the first time since 1972 that any extraterrestrial solid material has been collected and brought back to Earth, and the first time ever for comet particles.

Comets are thought to be leftovers from the process of planet formation, and scientists said the dust collected by Stardust will give them their first opportunity to study pristine samples of materials formed billions of years ago.

"We are collecting the actual building blocks the solar system was formed from 4.5 billion years ago," said Don Brownlee, an astronomy professor at the University of Washington who served as principal investigator for the Stardust mission. "We believe that the particles have a lot of information stored in them."

The largest particles will be visible to the naked eye, Brownlee said, though most will be a tenth as wide as a piece of human hair. They were captured by a tennis-racket-sized space probe containing ice-cube sized compartments lined with aerogel, a porous substance that is 99.9 percent air.

The spacecraft came within 147 miles of Wild 2 to collect the particles on January 2, 2004. It was launched from Cape Canaveral, Florida in February 1999.

During its descent over the desert, the capsule is scheduled to deploy two parachutes, though NASA officials said they have prepared for the possibility of a hard landing.

A NASA probe called Genesis crashed to Earth in 2004 when its parachute failed to open. That craft had been on a three-year mission to collect solar wind ions, which were recovered by scientists even though the spacecraft was destroyed.

Stardust's project manager, Tom Duxbury, said that after the Genesis incident and the Columbia shuttle disaster, the mission's team spent six months testing and reviewing the spacecraft's design to make sure there were no errors.

"We are totally prepared, both for if everything goes perfectly and if the spacecraft acts up a little bit," Duxbury said, adding that the Stardust capsule is smaller and more rugged than the Genesis capsule.

The capsule will be retrieved in the desert by helicopters or ground vehicles, depending on the weather. The samples will then be flown to the Johnson Space Center in Houston.

The Stardust mother ship will remain in space and may be used in future missions to study planets, asteroids or comets, Duxbury said.

Source: REUTERS

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