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Comet Encounter
Image courtesy NASA/JPL-Caltech/Cornell
Like a potato emerging from the shadows, the icy core of comet Tempel 1 looms into view in a new picture from NASA's Stardust spacecraft released Tuesday.
The image was snapped at 11:39 p.m. ET during a close flyby that brought the office desk-size craft within 110 miles (178 kilometers) of the 3.7-mile-wide (6-kilometer-wide) comet. Stardust took 72 high-resolution pictures during the encounter, 60 of which had been successfully beamed back to Earth as of Tuesday afternoon ET.
The comet and spacecraft are both seasoned pros when it comes to NASA missions. In 2005 Tempel 1 was visited by a NASA probe called Deep Impact, which smashed an 800-pound (363-kilogram) metal slug into the comet's core, or nucleus (see pictures of the comet impact). And in 2004 Stardust collected samples from the comet Wild 2 (pronounced "Vilt 2").
The Stardust-NExT mission involved retargeting Stardust for a Valentine's Day rendezvous with Tempel 1 after the comet had made a complete trip around the sun.
"This is the first time we've ever had the opportunity to visit a comet twice," Stardust-NExT project manager Tim Larson said today during a press briefing.
Tempel 1, he added, "comes as close to the sun as the orbit of Mars, and that's about where we met it last night with the spacecraft."
Published February 16, 2011
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Tempel 1's Close-up
Image courtesy NASA/JPL-Caltech/Cornell
Proposed in 2006, the Stardust-NExT mission had three main science objectives that involved taking pictures, according to Joe Veverka, the Stardust-NExT principal investigator, based at Cornell University in Ithaca, New York.
"First of all, we wanted to look again at areas on Tempel 1 that we had seen before with Deep Impact and, for the first time, see what changes that occur on a comet when it gets close to the sun," Veverka said during the briefing.
"We also wanted the opportunity to look at the Deep Impact impact site, and we wanted to take the opportunity to extend our exploration and see areas on Tempel 1 not seen before."
Based on the images that scientists have seen so far—such the one above taken at 11:39 p.m. ET Monday—the mission hit the mark: "Was this mission 100 percent successful?" Veverka asked. "I'd have to say no, it was 1,000 percent successful!"
Published February 16, 2011
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Valentine's Visit
Image courtesy NASA/JPL-Caltech/Cornell
Two small, circular craters—visible in a picture taken by the Stardust craft Monday night—flank the region of comet Tempel 1 that was hit during the 2005 Deep Impact mission. The cosmic smashup had sent up a bright spray of ice and dirt, obscuring the crater site in pictures taken at the time.
"That created a lot of mystery, but it also helped create this mission," said Pete Schultz, a Stardust-NExT co-investigator at Brown University in Providence, Rhode Island.
The path and timing of the Stardust-NExT flyby was carefully calculated so that scientists could get a look at the impact site. The new pictures prove that Deep Impact made a crater, about 492 feet (150 meters) wide—too small to be seen in this picture. The pit is not very sharply defined, though, with a small mound in its center.
"The bottom-line message is that the surface of the comet at the impact site is very weak, so the crater partly healed itself," Schultz said.
Published February 16, 2011
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Target Sighted
Image courtesy NASA/JPL-Caltech/Cornell
From thousands of miles away, Tempel 1 looks like no more than a mote of dust in a picture taken by the Stardust spacecraft as it approached the comet Monday night. Not visible in the new pictures is the larger halo of ice grains and dust that surrounds the comet's nucleus.
When a comet gets close to the sun—as Tempel 1 was during the flyby—ices on its surface sublimate, or turn directly from solid to gas. As this happens, "comets send out clouds of dust and ice and rock that come apart," said Stardust-NExT co-investigator Don Brownlee of the University of Washington in Seattle.
"It's a very dramatic environment." (Also see "Comet Is Cosmic Snow Globe, NASA Flyby Shows.")
In fact, Stardust recorded thousands of impacts with dust and ice grains as it swooped close to Tempel 1. Even so, the spacecraft emerged healthy, and mission managers plan to collect more data and pictures of the comet over the next few weeks as Stardust bids Tempel 1 adieu.
Published February 16, 2011
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