[meteorite-list] Stardust Payload May Offer a Big Payoff

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Jan 9 00:20:50 2006
Message-ID: <200601090519.k095JC506163_at_zagami.jpl.nasa.gov>

http://www.chron.com/disp/story.mpl/space/3571442.html

NASA craft's payload may offer a big payoff

A long-awaited mission returning with cosmic dust that could explain our
very origins

By MARK CARREAU
Houston Chronicle
January 6, 2006

After seven years of collection work in the inner solar system, a NASA
spacecraft is hurtling back to Earth with a cargo of microscopic
particles that may hold clues to the earliest formation of the planets
and the distribution of materials responsible for life.

Aptly named Stardust, the unmanned craft is on course for a fiery plunge
into the Earth's atmosphere early Jan. 15, descending in darkness by
parachute to the Utah desert.

Eager scientists plan to pore over thousands of space particles, which
were snatched by Stardust from the comet Wild-2 on Jan. 2, 2004, and
from a stream of interstellar dust flowing through the solar system in
2000 and 2002.

The extraterrestrial samples, with a collective mass estimated at less
than a thousandth of a gram, will join the Apollo moon rocks in storage
at NASA's Johnson Space Center in Houston.

Comet particles will be parceled out to researchers worldwide for
chemical and physical assessments.

"This was a fantastic opportunity to collect the most primitive
materials in the solar system," said Don Brownlee, the University of
Washington scientist who serves as the mission's principal investigator.
"We believe some of the particles from the comet will in fact be older
than the sun and the planets."

Launched Feb. 7, 1999, on a $212 million mission, Stardust spiraled
outward from the Earth toward a rendezvous with Wild-2. Scientists think
the comet, formed about 4 billion years ago, circled the sun from the
outer solar system until a gravitational tug from Jupiter in 1974 pulled
it within range of the robotic spacecraft.
      
A bull's-eye

On Jan. 2, 2004, Stardust scored a bull's-eye, swooping within 149 miles
of Wild-2's 3.3-mile-wide icy core and snatching from a stream of tiny
fragments. The fragments joined equally small pieces of interstellar
dust trapped on board.

Scientists puzzle over the role of comets in the formation of the solar
system. Many think these collections of rock and ice served as
intermediate building blocks and that vast clouds of comets on the
frontier of the solar system are remnants from the construction process.

They theorize that comets that collided with Earth during the final
stages may have been the source of water that formed the oceans and the
chemical elements considered precursors for life.

Much earlier in the history of the universe, these elements were forged
in the first generations of stars. As the earliest stars exhausted their
supplies of hydrogen fuel, they exploded. The detonations created new,
more complex chemical elements that were dispersed into space, where
they became the raw materials for new stars and perhaps planetary systems.

"We are using (Wild-2) as a kind of library, a carrier that scarfed up
the building blocks of the solar system and preserved them far from the
sun at low temperatures for 4.5 billion years and has now dumped them
off," Brownlee said.

As Stardust's journey draws to a close, NASA is preparing for the launch
of New Horizons, another mission to explore the planet-building process.

Slated for a Jan. 17 liftoff, New Horizons will make a decadelong
journey to distant Pluto. An icy object that seems more than a comet but
less than a planet, Pluto may reveal still more about how the solar
system was constructed.

As Stardust nears Earth late on Jan. 14, the spacecraft is programmed to
eject a 100-pound, mushroom-shaped re-entry capsule containing the dust
from the comet and stars.

Its trajectory will steer the capsule into the Earth's atmosphere high
above the Pacific Ocean four hours later. Traveling at more than 28,000
mph, Stardust will create a bright streak in the night sky as it crosses
northern California, Nevada and Utah.

The probe will head for a landing on the U.S. Air Force Utah Test and
Training Range, southwest of Salt Lake City. The first of two parachutes
is programmed to deploy at an altitude of 20 miles, about 105,000 feet.

The recovery capsule should settle onto a stretch of desert terrain at
4:12 a.m., CST. Recovery teams will rely on radar and a radio beacon on
the capsule to home in on the landing site.

Scientists don't plan to open the capsule until it is flown to a
receiving lab at the Johnson Space Center on Jan. 17, said NASA's Mike
Zolensky, a co-investigator who will supervise the operation.

Slicing a grain

The opening will take place in a lab facility, with a cleanliness
standard 100 times that of a hospital operating room, to protect the
space materials from earthly contaminants that could pollute the samples
before they are turned over to a team of 200 experts from Europe,
Russia, Japan, Canada and South America as well as the United States.

The fragments snagged by Stardust are trapped in aerogel, a springy
lightweight material made from silica. Scientists will use microscopes
with special extraction tools to remove the comet and star grains.

"You might wonder what you can do with particles that are microscopic,
and in fact you can do a huge amount of analysis on one grain," Zolensky
said. "You can take a grain and slice it like you were slicing a loaf of
bread into hundreds of slices."
Received on Mon 09 Jan 2006 12:19:11 AM PST