April 9, 2006

Talk About Dust Collectors

Source: New York Times
Published: 4/9/2006
Written by: Marcelle Fischler

Two years ago, beyond the orbit of Mars, NASA's seven-year Stardust mission whooshed past the comet Wild 2, capturing samples of comet dust using a weblike material called aerogel.

After a journey of 2.88 billion miles, the canister filled with comet dust landed back on Earth in January. Recently some of the dust particles, none more than one-sixth to one-eighth the width of a human hair, arrived by FedEx at the National Synchrotron Light Source at Brookhaven National Laboratory.

George J. Flynn, a scientist in the physics department at the State University of New York at Plattsburgh, used an infrared microscope to analyze the dust.

"We have, we think, the pristine dust of the solar system," said Dr. Flynn, who hopes to find out if it played any significant role in the origin of light. "We have the stuff that was there when comets were forming. It's been frozen since then until we collected it."

There was no way to mix up the comet dust with the lint on his shirt, Dr. Flynn said. "This was collected at very high velocity," the only way it could get into the aerogel, he said. "About six kilometers per second, six times the speed of a rifle bullet."

Working with Lindsay P. Keller, a space scientist from the Johnson Space Center in Houston, Dr. Flynn determined that the specks of dust were crystals of a mineral called pyroxene, which previously had been identified in a few comets using telescopic measurements.

Dr. Flynn and Antonio Lanzirotti, a geologist from the University of Chicago, observed that the particles fragmented as they moved through the aerogel, leaving debris along the ice cream cone-shaped entry track.

"This indicates that comet dust is very weak," Dr. Flynn said, compared with Earth rocks and meteorites that were shot into the aerogel for practice.

The scientists discovered that the "average composition of the comet particles is similar to the average composition of the sun, measured by astronomers," he said.

The comet dust has not changed much, he added, "since the comet formed at the beginning of the solar system over four and a half billion years ago."

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