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Bob Pepin holds a piece of aerogel--a space-age glass foam

U physicist Bob Pepin holds a piece of aerogel, which is a dry glass foam with a density one-thousandth that of water, useful for catching high-speed microscopic particles.

Physicist awaits his piece of Stardust

The University's Bob Pepin is among the scientists who will study dust from a comet and interstellar space

By Deane Morrison

January 13, 2006; updated January 24

At just after 4 a.m. CST Jan. 15, the payload of NASA's Stardust mission, launched in 1999, parachuted to the Utah desert with the first-ever samples of comet dust, collected from Comet Wild-2 (pronounced "Vilt two") in 2004. University of Minnesota physics professor Bob Pepin is delighted by its safe return, because he will receive a sample of that dust. Pepin, whose projects with NASA go back to the Apollo moon missions, will analyze those samples for their helium and neon content.

"Because some scientists have proposed that comets have contributed these gases to the atmospheres of Earth, Venus, and Mars, learning about these gases in comets would be fascinating," says Pepin.

The samples were collected in a space-age substance called aerogel, a silicon "sponge" with one-thousandth the density of water. The samples hit the aerogel at 13,000 miles per hour, or six times the speed of a bullet. Aerogel, says Pepin, is specially designed to slow down and capture dust particles.

The Stardust mission is also bringing back samples of high-speed dust particles believed to have originated outside the solar system They are not coming from the direction of the sun, and nothing in the solar system is thought capable of producing them. Actually, their high speed--about 25 kilometers per second--may be just an illusion due to their collisions with objects in our solar system as it moves around the center of the Milky Way galaxy.

Pepin expects it will be at least several weeks before he receives samples of Stardust.

In September 2004 the world witnessed the crash landing in Utah of NASA's Genesis mission. (Stardust is destined to land in the same area, but Pepin says there are no serious worries about a crash this time.) Genesis had collected tiny particles streaming from the sun in what is called the solar wind. Pepin is also studying particles from Genesis, which were captured in gold foil that was exposed to the solar wind deep in space. To listen to an audio vignette on Bob Pepin's Stardust research, click on University of Minnesota Moment. University of Minnesota Moment is a daily radio feature highlighting University expertise on a wide range of timely topics.