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Specks of 'fire and ice' in comet dust

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Scientists say the minerals found in the samples include magnesium olivine and other compounds.

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National Aeronautics and Space Administration (NASA)
University of Washington

(CNN) -- Scientists with NASA's Stardust mission said they have found "fire and ice" in dust from the tail of Comet Wild-2, findings they called surprising on Monday.

"Remarkably enough, we have found fire and ice," said Stardust principal investigator Don Brownlee of the University of Washington.

"In the coldest part of the solar system, we have found samples that have formed at extremely high temperatures. So, the hottest samples in the coldest place."

Launched in 1999, the Stardust spacecraft orbited the sun on a long intercept course with Wild-2.

On January 2, 2004, it flew through the comet's tail, collecting bits of dust in a tennis racket-shaped collector resembling an ice-cube tray, filled with a substance called aerogel -- a low-density silica glass, nearly as light as air. The aerogel cushioned the fast-moving particles for the trip back to Earth.

On January 15 of this year, the Stardust spacecraft passed by Earth and jettisoned a 100-pound capsule containing the dust samples. It entered the atmosphere over the Pacific Ocean traveling almost 29,000 miles per hour, and streaked across the sky over Oregon and Nevada on its way to its landing zone at the Air Force Utah Test and Training Range west of Salt Lake City.

The sample canister was soon transported to NASA's Johnson Space Center in Houston, Texas, where it was opened and where the samples will be housed on a long-term basis.

Scientists have pored over the samples for a little more than a month. So far, six of the 132 "cells" containing the aerogel have been removed, and the some of the larger dust particles have been extracted and analyzed.

Scientists say the minerals found in the samples include magnesium olivine, and other compounds rich in calcium, aluminum and titanium.

While none of these minerals are new to the scientists, they do express some surprise at finding them in a comet. Scientists believe comets are icy, rocky debris left over from the formation of the solar system 4.5 billion years ago. While they orbit the sun, comets populate the frigid fringes of the solar system, and any minerals frozen inside them are preserved in a deep freeze.

"We found mineral grains that are considered very high-temperature minerals -- they normally form under extremely high temperature conditions," Brownlee said. "And yet they were collected in a comet, the Siberia of the solar system."

So how is it that these high-temperature minerals came to reside deep inside a comet, far from the blast furnace where they were formed?

"There are two major possibilities," Brownlee said. "One that they formed in the innermost, hotter-most regions of our solar system when the sun and planets were forming, and they were thrown out -- all the way out to the Pluto region of the solar system. The other possibility is they were formed around other stars, in hot regions around other stars."

The goal of the Stardust mission is to study how the solar system formed and evolved. This early analysis of the Stardust samples seems to be evidence that the early solar system was a dynamic, explosive place.

"If these are really from our own sun, they've been ejected out, ballistically out, all the way across the entire solar system, and landed out there," said Stardust scientist Mike Zolensky. "These materials where basically on a big conveyor belt -- being shot out, and then gradually drifting in, and then being shot out again."

"It's like everything else in science," he said. "You learn something about one thing, and it raises more questions somewhere else. So we can't write all the answers right now, it's just great we have new mysteries to worry about now."

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