Comet gets starry-eyed once-over

CORNELL (US) — Despite resembling a flight through artillery fire, the February 14 close encounter of the Stardust spacecraft and the comet Tempel 1 was well worth the experience.

“If you ask me, was this mission 100 percent successful in terms of the science? I would have to say—no,” says Joe Veverka, Cornell University professor of astronomy and principal investigator for Stardust-NExT, responsible for overseeing the NASA mission. “It was 1,000 percent successful.”

The Valentine’s Day mission sent the Stardust spacecraft, which collected dust from the comet Wild 2 in 2004 and dropped it off on Earth in 2006, on a second assignment: this time to the 88.2 billion-ton (40 trillion kg) Tempel 1 for a new look at the comet that was first visited by the Deep Impact spacecraft in 2005.

Six years ago, Deep Impact sent an 800-pound probe smashing into Tempel 1, giving scientists new information about the comet’s structure and composition—but also creating a plume of ejecta that obscured the resulting crater.

The new mission’s goals, therefore, were to get a first look at the crater, so  researchers could see how the comet formed and evolved; to show how the comet’s surface changed after an orbit around the sun;  and to get a look at terrain that hadn’t been seen before.

The flyby scored three for three.

Among the 72 resulting high-resolution images, some show the crater, which is about 150 meters in diameter with a small mound of debris in the center—material that was sent flying by the impact and fell back to the surface.

Other images show an area that was heavily pitted in 2005, but is smoothed out in the new images, indicating substantial erosion. And images of new territory show a variety of intriguing features, including areas of extensive layering.

“To understand how this comet works, we have to put everything together,” Veverka says.

The spacecraft used two external instruments to detect and analyze the dust surrounding the comet’s nucleus. At just 112 miles (181 km) apart at the closest approach, there was a lot of dust to fly through—not to mention larger particles that battered the spacecraft in fits and starts.

“This is the way comets act,” says Don Brownlee, Stardust-NExT co-investigator and professor of astronomy at the University of Washington.

“They don’t just spew off things in a uniform way. They send it out in bursts and puffs … clods of dirt and ice and rock that come apart. So a good analogy [would be] a B17 in World War II flying through flak.”

Stardust-NExT is managed by JPL, a division of the California Institute of Technology, for the NASA Science Mission Directorate. Lockheed Martin Space Systems built the spacecraft and manages day-to-day mission operations.

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