[meteorite-list] Stardust Nears End of Epic Journey; Researchers Await Its Treasure

[Ron Baalke]

http://www.uwnews.org/article.asp?articleID=21550

Office of News and Information
University of Washington, Seattle, Washington

CONTACT:
Vince Stricherz, 206-543-2580

Jan. 3, 2006

Stardust nears end of epic journey; researchers await its treasure

Donald Brownlee's heart skipped a beat six years ago when the launch of 
the Stardust spacecraft didn't happen as planned. The University of 
Washington astronomy professor has experienced many other tense times 
since the historic mission blasted off a day late, and its return to Earth 
on Jan. 15 will be just one more white-knuckle moment.

Just before 3 a.m. MST [1000 UTC], the spacecraft will jettison its return 
capsule, which will plunge into Earth's atmosphere at nearly 29,000 miles 
per hour, the greatest return speed ever recorded. A few moments later, 
after the capsule slows to just faster than the speed of sound, a 
parachute will apply the brakes and Stardust will settle to the ground on 
the Air Force's Utah Testing and Training Range southwest of Salt Lake 
City.

"There's a lot at stake. You just hope everything works, and I am 
confident it will work," said Brownlee, the mission's principal 
investigator, or lead scientist.

The return capsule contains tiny bits of dust captured two years ago as it 
spewed from a comet called Wild 2. The tennis-racquet-shaped collector 
used a remarkably light and porous material called aerogel to capture the 
particles, each much smaller than a grain of sand and traveling six times 
the speed of a bullet fired from a rifle. Earlier, the reverse side of the 
collector snared interstellar dust grains flowing into the solar system 
from other stars in our galaxy. In all, the capsule contains tens of 
thousands of comet grains and about 100 bits of interstellar dust.

"It's really quite an epic thing. I think it tends to get overlooked 
because it's just a little mission, and there aren't any people on board," 
Brownlee said. "But the really big part of the research is just getting 
ready to start, when the material goes to the laboratory. The train is 
headed for the station and we're all waiting for it."

Stardust is part of the National Aeronautics and Space Administration's 
series of Discovery missions and is managed by the Jet Propulsion 
Laboratory in Pasadena, Calif. Besides the UW, other collaborators are 
Lockheed Martin Space Systems; The Boeing Co.; Germany's Max-Planck 
Institute for Extraterrestrial Physics; NASA's Ames Research Center; and 
the University of Chicago.

After the capsule touches down in the Utah desert, a canister bearing the 
aerogel collector grid will be removed and taken to the Johnson Space 
Center in Houston, where the samples will be cataloged and sent to 
scientists around the world. Brownlee expects them to provide key 
information on the formation of the solar system 4.6 billion years ago and 
possibly to shed light on the origins of life on Earth. Scientists are 
likely to study Stardust's treasure for decades to come.

Stardust was launched on Feb. 7, 1999, and set off on three giant loops 
around the sun. It began collecting interstellar dust in 2000 and met Wild 
2 (pronounced Vilt 2) on Jan. 2, 2004, when the spacecraft weathered a 
hailstorm of comet particles and snapped exceptional close-up photographs 
of the comet's surface. During its 2.88 billion-mile voyage Stardust made 
one pass by Earth to get a speed boost from the planet's gravity, and 
later staged a dress-rehearsal for the comet encounter when it maneuvered 
very close to Asteroid 5535 Annefrank.

The tensest moment other than the comet encounter came in November 2000, 
while the spacecraft was cruising along some 130 million miles from the 
sun. A huge solar flare, 100,000 times more energetic than usual, engulfed 
Stardust and its special digital cameras that help the spacecraft know 
where it is by viewing the stars and making comparisons with a 
comprehensive star chart stored in the onboard computer. The high-energy 
solar flare electrified pixels in the cameras, producing dots that the 
computer interpreted as stars. Suddenly the spacecraft did not know where 
it was and, in a preprogrammed act of self-preservation, it turned its 
solar panels toward the sun, losing communication with Earth.

Ground controllers finally found a faint signal and were able to contact 
Stardust and correct the problem. A little more than three years later the 
spacecraft finally met the target that scientists had been aiming for 
since 1974, when a close encounter with Jupiter altered Wild 2's orbit and 
brought it to the inner solar system. That made the mission feasible.

Scientists have collected thousands of meteorites and cosmic dust 
particles on Earth, Brownlee noted, but with few exceptions the origin of 
those materials is unknown. Now there will be samples of material from 
another known body in space, and those grains can be compared with all the 
previously collected meteorites and bits of dust to see if there are 
similar origins. The Wild 2 samples are cryogenically preserved solar 
system building blocks, kept close to their original state because they 
have existed mostly at the outer edge of the solar system.

"Virtually all the atoms in our bodies were in little grains like the ones 
we're bringing back from the comet, before the earth and sun were formed," 
Brownlee said. "Those grains carry elements like carbon, nitrogen and 
silicon from one place to another within our galaxy, and they helped form 
the sun, the planets and their moons."

Stardust's photographs of Wild 2 also are cause for further study. 
Brownlee still marvels at the rugged surface the pictures disclosed, a 
surface very different from the smoother cores of the other three comets 
-- Tempel 1, Borrelly and Halley -- that have been photographed up close.

"For unknown reasons, the surface of Wild 2 looks quite different -- 
spectacularly different -- from asteroids, moons, planets and even from 
other comets," he said.

Stardust Milestones

* Farthest distance solar powered spacecraft has traveled from the sun, 
  253 million miles
* Longest distance traveled by a return mission, 2.88 billion miles
* First solid sample return mission since the Apollo program
* First sample return mission from beyond the moon
* First interstellar dust collection on Feb. 22, 2000
* Close encounter with Asteroid 5535 Annefrank on Nov. 1, 2002
* Return to Earth of microchips engraved with the names of more than 1 
  million people, plus the names from the Vietnam Veterans Memorial in 
  Washington, D.C.
* Fastest re-entry speed of any return capsule, nearly 29,000 miles per 
  hour

For more information, contact Brownlee at (206) 543-8575  

STARDUST WEB SITE,
     http://stardust.jpl.nasa.gov

[NOTE: Images supporting this release are available at
http://www.uwnews.org/article.asp?articleID=21550 ]