Tags: NASA | Stardust | Mission | Bring | Comet | Dust | Earth

NASA Stardust Mission To Bring Comet Dust to Earth

Tuesday, 27 December 2005 12:00 AM

WASHINGTON -- After spending nearly seven years in space and traveling more than 4.6 billion kilometers, NASA's Stardust spacecraft returns to Earth's atmosphere January 15, 2006, to release a capsule that will parachute to the ground, carrying precious samples of cometary and interstellar dust.

Scientists believe the cargo will help answer basic questions about comets and the origins of the solar system.

"Comets are some of the most informative occupants of the solar system," said Mary Cleave, associate administrator for NASA's Science Mission Directorate.

"The more we can learn from science exploration missions like Stardust," she added, "the more we can prepare for human exploration to the moon, Mars and beyond."

Stardust is the first spacecraft with the ability to retrieve samples obtained in deep space and return them to Earth for research.

The mission is a joint effort among NASA, several universities and industry partners. It is the fourth in a series of NASA Discovery missions that are economical and use high-performance technology.

The $168.4 million mission (not including the Delta 7426 launch vehicle) was launched from Cape Canaveral Air Force Station in Florida in February 1999. Stardust has circled the sun three times in nearly seven years.

"Our mission is called Stardust in part because we believe some of the particles in the comet will be older than the sun and planets that formed around other stars," said Stardust principle investigator Don Brownlee at a December 21 NASA briefing. "We call them stardust."

On the way to its comet encounter, the spacecraft collected interstellar dust on two different solar orbits.

On January 2, 2004, after traveling 3.41 billion kilometers across the solar system, Stardust made its closest approach of comet Wild 2 at a distance of 240 kilometers.

During this flyby, a special collector captured particles of the comet as the spacecraft flew through the coma – or cloud of dust and debris – surrounding Wild 2.

Aerogel, a silica-based material contained in a tennis-racket-shaped grid, was developed specially to help capture the comet material without damaging it.

Along with this cosmic sampling, the spacecraft also took remarkable images of comet Wild 2's nucleus.

The otherworldly landscape included such features as steep near-vertical cliffs, house-size boulders, pinnacles, flat-floored craters with near-vertical walls, overhangs and materials of varying brightness.

The images showed a complex rugged surface that is quite different from those of other comets, asteroids and moons that have been imaged.

Deep depressions on the comet suggest that regions of the surface have eroded to depths of 100 meters or more. One of the most spectacular findings was that the comet had more than 20 active jets – localized hotspots – spewing gas and dust into space.

Six hours after the comet encounter, the spacecraft carried out a half-hour process of retracting and stowing the sample collector with its cometary pickings. From that point on, the sample canister has been sealed.

In the hours and days following the encounter, images and other science and engineering data recorded onboard during the event were transmitted to Earth.

On January 5 and January 13, 2006, mission navigators will command the spacecraft to perform targeting maneuvers. On January 15, 2006, Stardust will release its sample return capsule. Four hours later, the capsule will enter Earth's atmosphere 125 kilometers over the Pacific Ocean.

The velocity of the sample return capsule, as it enters Earth's atmosphere at 46,440 kilometers per hour, will be the fastest of any human-made object on record.

The capsule will release a drogue parachute (a small parachute used to pull a main parachute from its storage pack) at about 32 kilometers. When the capsule has descended to about 3 kilometers, the main parachute will deploy.

The capsule is scheduled for a soft landing at the U.S. Air Force Utah Test and Training Range, southwest of Salt Lake City, at 5:12 a.m. EST.

After the capsule lands, if weather permits, a helicopter crew will fly it to the U.S. Army Dugway Proving Ground in Utah for initial processing. If weather is bad, special off-road vehicles will retrieve the capsule and return it to Dugway.

Samples then will be moved to a special laboratory at NASA's Johnson Space Center in Texas, where they will be preserved and studied.

"Locked within the cometary particles is unique chemical and physical information that could be the record of the formation of the planets and the materials from which they were made," Brownlee said.

NASA expects most of the collected particles to be no more than a third of a millimeter across. Scientists will slice the particle samples into even smaller pieces for study.

"It's really exciting to me," Brownlee added, "that this message, this cosmic library, is in a box and it's on the way back to Earth. We will have it soon and have it in the lab to do whatever we can to try to read those records of our earliest history."


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WASHINGTON -- After spending nearly seven years in space and traveling more than 4.6 billion kilometers, NASA's Stardust spacecraft returns to Earth's atmosphere January 15, 2006, to release a capsule that will parachute to the ground, carrying precious samples of cometary...
Tuesday, 27 December 2005 12:00 AM
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