Surviving Wild Comet Impacts

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Team Stardust, NASA’s first dedicated sample return mission to a comet, passed a huge milestone today by successfully navigating through the particle and gas-laden coma around comet Wild 2 (pronounced "Vilt-2"). During the hazardous traverse, the spacecraft flew within 240 kilometers (149 miles) of the comet, catching samples of comet particles and scoring detailed pictures of Wild 2′s pockmarked surface.

close view of wild-2
During the comet flyby, the closest view yet of a comet at about 149 miles.
Credit: NASA/JPL

The control room at NASA’s Jet Propulsion Laboratory in Pasadena erupted in cheers and clapping at 11:40 a.m. PST (2:40 p.m. EST) as monitors showed an uninterrupted flow of data from the Stardust spacecraft during its closest encounter point with the comet.

"Things couldn’t have worked better in a fairy tale," said Tom Duxbury, Stardust project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. "We’ve flown through the worst of it and we’re still in contact with our spacecraft," Duxbury said. "We’re still exuberant. What a deal."

"These images are better than we had hoped for in our wildest dreams," said Ray Newburn of JPL, a co-investigator for Stardust. "They will help us better understand the mechanisms that drive conditions on comets."

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Principal Investigator Don Brownlee, announces at press conference: "These are the best pictures ever taken of a comet".
Credit: NASA/JPL

"These are the best pictures ever taken of a comet," said Principal Investigator Dr. Don Brownlee of the University of Washington, Seattle. "Although Stardust was designed to be a comet sample return mission, the fantastic details shown in these images greatly exceed our expectations."

Stardust’s navigation camera, which is fixed to the spacecraft body, took images of the comet nucleus. The camera was protected from direct hits because it faces away from the direction of the particle onslaught. It recorded images of the comet through the reflection in a movable mirror. The mirror provided image-motion compensation –that is, itmoved to keep the reflection of the comet in the camera’s field-of-view and minimize image smearing during the flyby.

The collected particles, stowed in a sample return capsule onboard Stardust, will be returned to Earth for in-depth analysis. That dramatic event will occur on January 15, 2006, when the capsule makes a soft landing at the U.S. Air Force Utah Test and Training Range.

The microscopic particle samples of comet and interstellar dust collected by Stardust will be taken to the planetary material curatorial facility at NASA’s Johnson Space Center, Houston, Texas, for analysis.

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Micron-sized dust particles to be returned to Earth trapped in a silica aerogel in two years time.
Credit: NASA/JPL

Stardust has traveled about 3.22 billion kilometers (2 billion miles) since its launch on February 7, 1999. As it closed the final gap with its cometary quarry, it endured a bombardment of particles surrounding the nucleus of comet Wild 2.

To protect Stardust against the blast of expected cometary particles and rocks, the spacecraft rotated so it was flying in the shadow of its "Whipple Shields."

The shields are named for American astronomer Dr. Fred L. Whipple, who, in the 1950s, came up with the idea of shielding spacecraft from high-speed collisions with the bits and pieces ejected from comets.

The system includes two bumpers at the front of the spacecraft — which protect Stardust’s solar panels — and another shield protecting the main spacecraft body. Each shield is built around composite panels designed to disperse particles as they impact, augmented by blankets of a ceramic cloth called Nextel that further dissipate and spread particle debris.

aerogel_capture
Ultra-lightweight aerogel capture frame.
Credit: NASA/JPL

"Everything occurred pretty much to the minute," said Duxbury. "And with our cometary encounter complete, we invite everybody to tune in about one million, 71 thousand minutes from now when Stardust returns to Earth, bringing with it the first comet samples in the history of space exploration."

Scientists believe 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 cometary particles could be the record of the formation of the planets and the materials from which they were made.

Wild-2 is considered an ideal target in part because it has only recently been deflected from a distant orbit into its current orbit which brings it into the inner solar sytem. Its drastic orbit change resulted from a very close approach that the comet made to Jupiter in September 1974. Before that, the comet was in a much longer orbit and had made fewer passages of the Sun, so it is more pristine than most short-period comets. Since Comet Wild-2′s orbit change in 1974, it has looped in toward the Sun three times. Comet scientists anticipate that 1 to 5 percent of Wild-2′s nucleus surface could be active with gas and dust jets erupting from the surface.


Related Web Pages

Stardust
Washington University, Seattle
Live Webcam of Stardust Mission
Early Wild Success for Stardust
Telescopes for Stardust
Harpooning a Comet
Two-Way Asteroid Trip Takes Off
Tale of a Comet
We Are All Made of Stars
Winter Boon From Deep Space