April 24, 2000
-- Like an excited kid hoping to snag a fly ball at a professional
baseball game, NASA's Stardust spacecraft has extended its high-tech
"catcher's mitt" to collect a valuable space souvenir
-- a batch of interstellar dust particles.
The dust is contained in a stream of particles that flows through
our solar system, and scientists are anxious to study it so they
can learn more about the formation of Earth, other planets and
life.
"We can see this material with the naked eye as
a black zone running along the center of the Milky Way,"
said Dr. Donald Brownlee of the University of Washington in Seattle,
principal investigator for Stardust. "These particles contain
the heavy chemical elements that originated in the stars. Since
every atom in our bodies came from the inside of stars, by studying
these interstellar dust particles we can learn about our cosmic
roots."
Stardust is equipped with a special
collector containing aerogel,
a unique substance that can trap the particles and store the
precious cargo safely until it's returned to Earth. The aerogel
collector has two sides, one designed to gather the interstellar
dust and one for comet dust collection, which will take place
later in the mission. Engineers orient the spacecraft to control
which side of the collector is exposed to a dust stream.
Right now, Stardust is oriented so that the interstellar dust
particles are hitting the backside of the collector. This collection
began on February 22, when the spacecraft's sample return capsule
opened and the aerogel collector was moved out of the capsule.
It will remain in this configuration until May 1, when the collector
will return to its stowed position for safe storage until mid-2002,
when another period of interstellar dust collection is scheduled.
Right: Nobody really knows what a
typical interstellar dust grain looks like. By studying how dust
absorbs, emits, and reflects light, astronomers do know that
interstellar dust is much different than the cell and lint based
dust found around a typical house. Recent work indicates that
most dust grains are not spherical. The above picture shows the
result of a fractal
adhesion model for dust grains involving random conglomerates
of spherical compounds of different properties, here artificially
highlighted by different colors. [more
information]
"The project's name, 'Stardust,' reflects the importance
of this event," said Stardust Project Manager Dr. Kenneth
Atkins of NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
"It's the first time anyone has attempted to catch anything
like this and bring it home. After all the design, building,
testing, and now the flying of this spacecraft over the past
four years, the moment of truth for the collector is here. These
tiny particles zip by at 20 to 25 kilometers per second (about
45,000 to 56,000 miles per hour) relative to the spacecraft.
The aerogel must slow them to a stop in fractions of an inch."
Left: Dust particles shot into a sample of
aerogel during ground tests created these microscopic tracks
in the translucent, ultra-lightweight material.
In late December 2003, the collector will be deployed again in
preparation for the gathering of comet dust samples when Stardust
flies by Comet Wild-2 on January 2, 2004. Once the samples of
both interstellar dust and comet dust are tucked safely inside
the aerogel collector, it will be retracted into the sample return
capsule. Stardust will begin the return trip to Earth and make
a soft landing at the U.S. Air Force's Utah Test and Training
Range in 2006. The sample canister will be taken to the planetary
material curatorial facility at NASA's Johnson Space Center,
Houston, Texas. The samples will be carefully extracted and then
examined by scientists.
"I'm thrilled at the thought of being able to look at and
study these particles firsthand," Brownlee said.
More information on the Stardust mission is available at http://stardust.jpl.nasa.gov/
.
Stardust was launched on February 7, 1999. The mission is
managed by JPL for NASA's Office of Space Science, Washington,
D.C. Lockheed Martin Astronautics, Denver, Co, built and operates
the spacecraft. Science instruments were provided by JPL, the
University of Chicago and the Max Planck Institute, Garching,
Germany. JPL is a division of the California Institute of Technology,
Pasadena.
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