Astronomer thrilled with comet-dust catch

Don Brownlee's first glimpse of his comet-dust catcher wasn't encouraging.

"I didn't see anything," the University of Washington astronomer said Tuesday by phone from NASA's Johnson Space Center in Houston.

Then a technician flipped the collector grid over, and a collective gasp escaped from the moon-suited scientists crowded around.

"It's better than we could have possibly hoped for," Brownlee said. "We have a huge number of impacts, and some are quite big and visible to the naked eye."

Some of the largest particles shattered into bits of black debris when they hit the collector, which is made up of a super-light material called aerogel. Many other particles left visible tracks as they plowed into the aerogel at more than 13,000 mph, then stopped intact.

"I remember warning people not to be disappointed if these tracks were very hard to see, but they are absolutely stunning," said Brownlee, who is principal investigator for the $212?million mission.

He was calling from outside a special clean room built to process comet particles captured by the Stardust spacecraft and returned to Earth on Sunday. It's the first time NASA has brought solid material back from space since Apollo 17 delivered 244 pounds of moon rocks in 1972.

Stardust traveled seven years and nearly 3 billion miles, passing within 150 miles of the comet called Wild-2. During the close encounter in 2004, the spacecraft held its tennis-racket-shaped collector in the path of gas and dust shooting from the comet.

But until the collector was opened Tuesday, no one knew whether the device had actually snagged any particles.

"You just don't know if nature is going to cooperate or not," Brownlee said. "It has been a magic mission."

He and other scientists are eager to examine the particles in detail, because comets are believed to be the most pristine remnants of the original material from which the sun and planets formed 4.5?billion years ago.

The research team will spend about a week photographing the collector and examining it under a microscope before they begin the painstaking process of extracting particles, most of which are less than one-fifth the diameter of a hair.

Specialized Tools , including some whimsically referred to as micro-pickle forks, were developed to pluck particles from the aerogel. Brownlee and his UW colleagues at UW have developed a technique to carve particles out.

With many thousands of grains to process, that could take a while. Brownlee won't have to wait much longer, though, to delve into the cosmic treasure chest. He expects to have the first bits of comet dust back in his Seattle lab within a week or two.