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What scientists hope to learn from a wisp of comet dust

Star dust from NASA's mission is expected to shed light on the genesis of the Earth's solar system.

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For the first time since the end of the Apollo program more than 30 years ago, scientists have harvested bits of our cosmic neighborhood and brought them back to Earth.

Where Apollo retrieved the equivalent of salt and pepper in 842 pounds of moon rocks, NASA's Stardust mission brought back planetary saffron - dust from a comet and from distant stars, represented by a million tiny grains that would barely cover the bottom of a thimble.

Tuesday, scientists are set to get their first peek at collectors bearing the dust - the culmination of a seven-year, nearly 3 billion mile trip to explore Comet Wild 2. The mission came to a picture-perfect end in the predawn hours Sunday morning, when a capsule bearing the samples threaded its way between two major storm systems, parachuting onto the desert floor at the US Army's Dugway Proving Ground in Utah.

The samples Stardust has gathered are expected to shed light on the conditions in which the solar system formed some 4.5 billion years ago and on the basic building blocks available for its construction. Scientists have long studied the gases comets purge when their ices vaporize as they approach the sun. And other flyby missions have allowed scientists to draw some crude conclusions about cometary dust.

But this sample-return mission will allow for far more detailed studies using room-size microscopes and mile-long particle accelerators.

"Comets are like libraries, storing the record of our formation in tiny particles," says Donald Brownlee, astronomy professor at the University of Washington and the mission's lead investigator.


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