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.

This image was taken during the close approach phase of Stardust's Jan 2, 2004 flyby of comet Wild 2. It is a distant side view of the roughly spherical comet nucleus. One hemisphere is in sunlight and the other is in shadow -- analogous to a view of the quarter moon. Several large depressed regions can be seen. Comet Wild 2 is about five kilometers (3.1 miles) in diameter. Credit: NASA/JPL

"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 breached. 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.

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.

Video coverage for subscribers only:
   VIDEO: TUESDAY'S POST-FLYBY ENGINEERING AND SCIENCE REPORT QT
   VIDEO: STARDUST IMAGES PRODUCE THIS MOVIE OF COMET FLYBY QT
   VIDEO: SIMULATION OF IMPACTS THAT STARDUST SUSTAINED QT

   VIDEO: STARDUST SURVIVES CLOSEST APPROACH TO COMET QT
   VIDEO: FIRST IMAGES RELEASED AT NEWS CONFERENCE QT

   VIDEO: PRE-ENCOUNTER INTERVIEW WITH PROGRAM MANAGER QT
   VIDEO: MISSION PLANNER DESCRIBES STARDUST'S CHALLENGES QT
   VIDEO: DESCRIPTION OF THE STARDUST SCIENCE PROGRAM QT
   VIDEO: REPORT ON THE STARDUST SCIENCE INSTRUMENTS QT
   VIDEO: INTERVIEW EXPLAINS STARDUST'S CAMERA SYSTEM QT
   VIDEO: LEARN MORE ABOUT THE EXOTIC AEROGEL MATERIAL QT
   VIDEO: AN INTERVIEW WITH STARDUST'S NAVIGATOR QT
   VIDEO: A LOOK AHEAD TO DEEP IMPACT COMET MISSION QT

   VIDEO: OVERVIEW OF THE SEVEN-YEAR STARDUST MISSION QT
   VIDEO: ANIMATION OF STARDUST COLLECTING COMET SAMPLES QT
   VIDEO: STARDUST RETURNS TO EARTH AND PARACHUTES TO UTAH QT
   VIDEO: ENCOUNTER DETAILED BY 39-MINUTE NEWS CONFERENCE QT
   ADDITIONAL VIDEO COVERAGE
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