Comet Findings Raise Fiery Mystery Comets are known as the icy bodies of the solar system. But new analysis of dust brought back by a space probe shows comets are also made up of minerals forged by fire.
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Comet Findings Raise Fiery Mystery

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Comet Findings Raise Fiery Mystery

Comet Findings Raise Fiery Mystery

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RENEE MONTAGNE, host:

The space mission that was supposed to help resolve questions about the origins of the solar system instead is adding new mysteries. The Stardust spacecraft spent seven years in space, and brought back thousands of particles of dust from the comet known as Wild Two. Some of those particles have scientists questioning their assumptions about comets, which are believed to contain substances from the earliest moments of the solar system. NPR's Howard Berkes reports.

HOWARD BERKES reporting:

Imagine a kid on Christmas morning, the excitement of tearing into gifts, and sustaining that joy for two months. That's what it seems Peter Tsou is going through. He is one of the lead NASA scientists on the Stardust space mission. He told a news conference yesterday that he's thrilled at the spacecraft's bounty of gifts. Tsou held up a chart showing the biggest one.

Dr. PETER TSOU (Scientist, NASA): We thought if we had one of those particles that we could see with our naked eye, we would be happy. Well, I gave [unintelligible], well forty-some. You can see this one here on top. This is almost, you can put your small finger through it. So, it's very exciting.

BERKES: Those relatively large particles of comet dust has been sliced by scientists into hundreds of samples, and studied by dozens of researchers on at least four continents. They've made some curious discoveries. A particle shaped like a heart found on Valentine's Day--a mineral called Olivine that is also found in the greenest sand of the beach at Lumahai on the Hawaiian island of Kauai.

There's no significance attached to either yet. But lead scientist Don Brownlee of the University of Washington labels another oddity the biggest surprise so far.

Dr. DON BROWNLEE (Astronomy, University of Washington): Fire and ice. In the coldest part of the solar system, we found samples that have formed at extremely high temperature. They were either red hot or white-hot grains. And after we collected a comet, the Siberia of the solar system. So, the hottest samples in the coldest place.

BERKES: Comets are frigid clouds of ice, dust, and gas. They cruise the coldest fringes of the solar system. So, finding minerals in comets forged by fire, raises some new questions. How did those minerals get from the hottest part of our solar system, from the blistering core near the sun, way out to the icy edge where comets formed? Or do the minerals come from more distant stars outside our solar system? Do we now rethink how comets formed?

Astronomer Don Brownlee of the University of Washington is confident one of the questions will get answered soon.

Dr. BROWNLEE: These are fascinating possibilities, but the fabulous thing is these are samples we have in the lab. We can study these at atomic level resolution. And most importantly, the isotopic properties, we can tell the difference, absolutely, for something that formed in our own solar system, and something that formed around another star.

BERKES: Brownlee adds that if the mineral samples are from other stars, they are ten times bigger than the samples scientists usually have for study. They could also be older than the sun.

Dr. BROWNLEE: So, it's a real exciting mystery story. So, stay tuned.

(Soundbite of laughter)

BERKES: There may be more mysteries to come. Scientists have yet to focus on particles of free-floating stardust gathered by the spacecraft. They're far smaller than the comet particles under scrutiny now. In fact, NASA is enlisting home computer users to help scan images of the dust collector, and help spot the microscopic particles.

Howard Berkes, NPR News.

MONTAGNE: The stardust mission has put comet Wild Two in the celestial body hall of fame. Find out what makes it stand out at npr.org.

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