NASA’s Stardust-Next spacecraft flew past Comet Tempel 1 at 8:38 Pacific time Monday night, snapping photos as it sped by.

In 2005, the Deep Impact probe blew a crater into Tempel 1 with an 800-pound metal slug. Since then, Tempel 1 has completed an orbit around the sun, losing ice and other material to the sun’s hot glare along the way. The new images will give astronomers new insight into how a comet is slowly destroyed by the sun.

“This is something we’ve never been able to see before,” said principal investigator Joe Veverka of Cornell University in an interview on NASA TV during the flyby. “We know every time a comet comes close to the sun, it loses material. But we don’t know where those changes occur.”

Stardust-Next, which originally launched as “Stardust” in 1999, swooped within 124 miles of Tempel 1’s icy, dirty core at about 24,300 miles per hour.

The spacecraft took a total of 72 science images, 46 as it approached and 26 as it receded from the comet. As it approached, it snapped pictures once every 6 seconds.

The new images started arriving at NASA’s Jet Propulsion Lab in Pasadena, California, about three hours after the spacecraft made its closest approach. Each image took 15 minutes to download. The Stardust crew wanted to download the five closest images first, but an unknown error sent the photos in the order in which they were taken. The astronomers had to wait until 6 a.m. Tuesday Pacific time to get the good stuff.

Luckily, the images were everything the science team hoped for.

“If you ask me, was this mission 100 percent successful, in terms of the science? I would have to say no,” Veverka said in a press conference Feb. 15. “It was 1,000 percent successful!”

Stardust-Next shot photos of new terrain that had never been seen before, as well as areas on Tempel 1 that had been covered by Deep Impact. The images showed that several regions changed significantly over the past five years. One of the most interesting areas looks like a blanket of material that erupted from beneath the comet’s surface and flowed downhill. That flow is now receding due to erosion, Veverka said.

“It goes much against the idea that [comets are] just icy dirtballs where nothing has happened since their formation,” Veverka said. “Apparently a lot of things have happened.”

The spacecraft also found the crater Deep Impact blew in the comet’s surface. Deep Impact never saw its handiwork, because the crater was obscured by all the dust and ice kicked up in the impact.

“That created a lot of mystery, and it also helped create this mission,” said Stardust-Next co-investigator Pete Schultz of Brown University.

The crater is about 150 meters (492 feet) across, and has a small central mound. It looks as if the cloud of material Deep Impact excavated fell back to the surface.

“The surface of the comet where we hit is very weak. It’s fragile,” Schutlz said. “The crater partly healed itself.”

Flying close to a comet is a risky business. Comets spew jets of gas and dust from beneath their surfaces, which act as little rocket thrusters, making the comet’s position hard to predict. In the final 16 hours, the spacecraft has to navigate on its own — signals from Earth would be too slow to direct last-second turns. And for five minutes before and after closest approach, Stardust-Next had to roll on its side to make sure the cameras were pointing straight at the comet’s heart, a maneuver that could have temporarily cut off communication with Earth.

The spacecraft also has to fly through the hailstorm of the comet’s coma, where clumps of dirt and ice collide and come apart. Co-investigator Don Brownlee of the University of Washington compared the spacecraft’s flight to a B-17 in World War II flying through flak. Stardust-Next’s instruments recorded about 5,000 dust strikes during the flyby, about 12 of which were large enough — a millimeter across — to pierce the spacecraft’s main shield.

But Stardust-Next is a flyby veteran. The spacecraft has traveled a total of 3,525,327,446 miles since its 1999 launch, It visited asteroid Annefrank in 2002 and comet Wild 2 (pronounced “willed two”) in 2004. Stardust caught particles from Wild 2’s cloudy coma in an instrument that resembled a catcher’s mitt, and in 2006 sent them back to Earth, where they are still being analyzed.

The flyby went without a hitch, the Stardust team said. The spacecraft was in almost the perfect position to photograph the comet when it arrived, and only had to roll half-a-degree to adjust its cameras.

The spacecraft’s near-perfect performance is particularly impressive considering its age. The 12-year-old probe was put together from recycled parts cribbed from the Voyager mission of the 1970s, the Galileo spacecraft in 1989 and the Cassini probe in 1997.

Reusing an already recycled spacecraft makes this mission space science on a shoestring, said Ed Weiler, NASA associate director for the science mission directorate. The extended mission, from after the Wild 2 samples returned to Earth until today, cost about $29 million. It would have cost about $500 million to start from scratch.

But Tempel 1 will be Stardust’s last stop. The spacecraft is running on fumes. It will continue to take photos of the comet over it shoulder for another week or two, until its fuel runs out. Then it will at last retire into the blackness of space.

Images: NASA/JPL-Caltech/Cornell. Animation: Dave Mosher/Wired.com.

See Also: