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Scientists Thrilled by Stardust Samples

Researchers say the intact comet particles brought back by a spacecraft's capsule exceed their 'grandest expectations.'

January 21, 2006|From Reuters

CAPE CANAVERAL, Fla. — Pristine comet samples returned this weekend by the Stardust spacecraft after a 2.9-billion-mile journey wildly exceeded scientists' expectations, project managers said Thursday.

A canister containing particles trapped during the Stardust space probe's 2004 encounter with comet Wild 2 (pronounced Vilt) landed on Earth on Sunday. The samples were taken to the Johnson Space Center in Houston for inspection.

"This exceeded all of our grandest expectations," Donald Brownlee, a University of Washington researcher and the principal Stardust investigator, said at a news conference.

The team was happy about the Stardust capsule's smooth landing in the Utah desert, but that was just the beginning.

When the sample canister inside the capsule was opened, scientists could see small black rocks and other particles that had been trapped in the probe's gel-filled collection device.

"We were totally overwhelmed by the ability to actually see this so quickly and so straightforwardly," Brownlee said.

The samples were trapped in aerogel, a substance that has the same ingredients as glass but is 99.9% air and has the lowest density of any solid substance.

The Stardust spacecraft lifted off seven years ago and aimed for a close encounter with comet Wild 2, a relative newcomer to the comparatively warmer region of space between the orbits of Mars and Jupiter.

The comet is believed to come from the Kuiper Belt region beyond Neptune but had a close approach to Jupiter in 1974, which deflected the icy body into its new orbit.

Because Wild 2 has not been circling near the sun for long, the comet may contain most of its original materials.

"We've brought back an ancient cosmic treasure from the very edge of the solar system," Brownlee said.

The chunks of Stardust's aerogel contain "hundreds and hundreds and hundreds of tracks" from comet particle impacts, some of which may end with a few atoms of water ice, Brownlee said.

One hole, which ends with an embedded rock, is so large, you can nearly poke a finger in, Brownlee said.

Scientists expect to get about 1 million particles larger than one-millionth of a meter in diameter.

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