The Calm After the Cometary Storm
January 6, 2004
Having weathered its out-of-this-world sandblasting by cometary
particles hurtling toward it at about six times the speed of a
rifle bullet, NASA's Stardust spacecraft begins its two-year,
1.14 billion kilometer (708 million mile) trek back to its
planet of origin.
"On January 2, comet Wild 2 gave up its particles but it did not
do so without a fight," said Stardust Project Manager Tom
Duxbury of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"Our data indicates we flew through sheets of cometary particles
that jostled the spacecraft and that on at least 10 occasions
the first layer of our shielding was breeched. Glad we had a
couple more layers of the stuff."
Stardust entered the comet's coma the vast cloud of dust and
gas that surrounds a comet's nucleus - on December 31, 2003.
From that point on it kept its defensive shielding between it
and what scientists hoped would be the caustic stream of
particles it would fly through. And fly through cometary
particles Stardust did, but not in the fashion the team
envisioned while designing the mission.
"We thought we would see a uniform increase in the number of
particles the closer we came to the comet's nucleus and then a
reduction," said University of Washington scientist Dr. Don
Brownlee, Stardust's Principal Investigator. "Instead, our data
indicate we flew through a veritable swarm of particles and then
there would be almost nothing and then we would fly through
another swarm."
Stardust scooped up these cometary particles, impacting at 6.1
kilometers per second (3.8 miles per second), for almost
instantaneous analysis from onboard instruments and stored other
particles for later, in-depth analysis, here on Earth. Along
with this cosmic taste testing, the spacecraft also took some
remarkable images of comet Wild 2's five-kilometer wide (3.1-
mile wide) nucleus.
"Our navigation camera was designed to assist in navigation, not
science," said Stardust's imaging team lead Ray Newburn. "But
these are the best images ever taken of a comet and there is a
remarkable amount of information in those 72 pictures. Not only
did we image the jets of material spewing out from the comet,
but for the first time in history we can actually see the
location of their origin on the surface of the comet."
At about 11:25 am Pacific Standard Time (2:25pm EST) on Jan. 2,
only minutes after its closest approach with the comet, Stardust
pointed its high gain antenna at Earth and began transmitting a
data stream that took over 30 hours to send but will keep
cometary scientists busy for years to come. About six hours
later another event took place that goes a long way to literally
increasing the scientists task load exponentially.
"Six hours after encounter we retracted the collector grid, with
what we are all confident is an abundance of cometary particles,
into the spacecraft's sample return capsule," added Duxbury.
"The next time the sample return capsule is going to be opened
is in a clean room at the Johnson Space Center in the days
following Earth return in January 2006."
Scientists expect in-depth terrestrial analysis of the samples
will reveal much about comets and the earliest history of the
solar system. Chemical and physical information locked within
the particles could be the record of the formation of the
planets and the materials from which they were made. More
information on the Stardust mission is available at
http://stardust.jpl.nasa.gov.
Stardust, a part of NASA's Discovery Program of low-cost, highly
focused science missions, was built by Lockheed Martin Space
Systems, Denver, Colo., and is managed by JPL for NASA's Office
of Space Science, Washington, D.C. JPL is a division of the
California Institute of Technology in Pasadena.
