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Space

NASA probe to return bits of comet to Earth

The Stardust probe was to land early this morning - and perhaps bring clues to the origins of the solar system.

TOOELE, Utah - The last time NASA scientists hunkered down at a remote Utah Army base, they stared wide-eyed as a space probe carrying solar wind atoms crashed into the salt flats and split open like a giant clamshell.

Flash forward two years.

With nerves on edge, scientists anxiously awaited the return of another space probe, this one named Stardust and bearing the first comet dust ever carried to Earth. A capsule bearing those samples was to be released late Saturday and expected to land on the Army's Dugway Proving Ground early today. Memories of the ill-fated 2004 Genesis landing, in which the space probe's parachutes failed to open, are still vivid.

Scientists found that gravity switches that had been installed incorrectly caused the failure. However, they were able to salvage the tiny cosmic samples for study.

After that mishap, engineers performed a thorough check on Stardust's systems, and said they felt certain it wouldn't suffer the same fate as Genesis.

"I don't think you can ignore the Genesis situation. You just have to embrace it and apply the lessons learned from it," said Ed Hirst, mission system manager at NASA's Jet Propulsion Laboratory, which is managing the $212-million project.

Stardust left on a seven-year, 2.9-billion-mile journey that was highlighted by a flyby of comet Wild 2, a jet-black ball of ice and dust that was about 500-million miles away from Earth when the probe was launched in 1999.

The goal was to return with microscopic samples that scientists say could provide clues to the solar system's origins.

The 850-pound Stardust, outfitted with armored bumpers, survived a harrowing blast of debris as it flew past Wild 2 to collect dust in 2004. During its journey, it also captured interstellar dust - tiny space particles believed to be from ancient stars that exploded and died.

Scientists say they think about 1-million microscopic comet and dust samples, most tinier than the width of a human hair, are now safely locked away in a canister inside Stardust.

Late Saturday, the Stardust mothership was to release the 100-pound capsule, expected to nosedive through Earth's atmosphere at about 29,000 mph toward Dugway Proving Ground, about 80 miles southwest of Salt Lake City.

The first parachute deploys at 100,000 feet while the capsule is moving at supersonic speed, followed by a larger chute, which guides it to a landing.

During the Genesis landing, Hollywood stunt pilots were dispatched in helicopters to snatch the probe in mid-air. But Genesis' parachutes never opened, and the capsule crash-landed at nearly 200 mph.

For Stardust, a helicopter recovery team flies to the landing site only after the capsule has landed. The next step for the capsule and its contents is a clean room on the base for processing. The mothership, meanwhile, must fire its thrusters to remain in perpetual orbit around the sun.

Once the capsule is ready, it will be shipped to NASA's Johnson Space Center in Houston, where scientists will pry open the canister and examine the samples under a microscope.

Scientists say they hope the samples will build on their knowledge of comets gleaned by NASA's Deep Impact mission last year, which smashed a probe into a comet, revealing its pristine interior.

[Last modified January 15, 2006, 01:48:18]