"Hot" Rocks Found in Icy Comet

March 14, 2006

Comet Wild 2 has spent most of its life in the most frigid reaches of our solar system. But at the comet, NASA's Stardust spacecraft has found minerals born of intense heat near the sun or other stars, scientists announced yesterday afternoon.

The surprising finding may alter our understanding of how comets form, they said.

(Watch video: Stardust Probe Mission Overview.)

Scientists have long thought of comets as cold, billowing clouds of ice, dust, and gases that formed on the edge of our solar system. The new discovery suggests that comets may have more complex histories.

"In the coldest part of the solar system, we have found samples that formed at extremely high temperatures—so the hottest samples [are in] the coldest place," said Donald Brownlee, an astronomy professor at the University of Washington in Seattle.

"It is quite exciting to find these things at the edge of the solar system," added Brownlee, who spoke at a briefing with reporters Monday at NASA's Johnson Space Center in Houston, Texas.

Brownlee is the principal investigator for the Stardust mission. The spacecraft launched February 7, 1999, to collect dust swirling off Wild 2 (pronounced Vilt 2). The capsule containing the dust samples landed in the Utah desert on January 15.

Findings from preliminary analysis of these samples were presented yesterday in Houston at the Lunar and Planetary Institute's annual science conference.

Star Origins

Many of the mineral samples examined could not have formed in or around the icy comet, Brownlee said. Rather, they were either shot out to the region near Pluto from the innermost and hottest regions of our solar system, or they formed in hot regions around other stars (interactive map of our solar system).

Further analysis of the samples will reveal whether the minerals came from our solar system or formed elsewhere in the universe, he added.

They key will be in the chemical signatures of the minerals, Brownlee said. Minerals from our solar system are chemically distinct from those found around other stars.

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