Are comets cold, billowing clouds of ice, dust and gases formed on
the edges of the solar system? Or is their composition more varied, their history more complex? Dr. Don Brownlee is at the forefront of the study of comets, meteorites and the solar system. The work he and his colleagues are doing is unlocking new information about the formation of comets,
and of the solar system.

Dr. Don Brownlee first envisioned a comet mission more than 25 years ago.

On Jan. 15, a light in the night sky over the Western United States marked the entry of the Stardust capsule into the earth’s atmosphere. The capsule landed safely in the Utah desert after its seven-year, 2.88 billion-mile voyage. Stardust, part of NASA’s series of Discovery missions and managed by the Jet Propulsion Laboratory in Pasadena, Calif., is a mission to collect particles from the comet Wild 2.

Brownlee was moved when he saw a picture of the return capsule. He said in a recent University Week interview, “It’s hard to describe the emotion. It was very exciting when I first saw the picture of the capsule in the mud. It almost brought a tear to my eye.”

Professor of Astronomy at the University of Washington, Brownlee studies cosmic dust. He is also Stardust’s principal investigator. He first envisioned this type of comet mission a quarter of a century ago.

In the same interview, Brownlee refers to the samples Stardust collected as a “cosmic library.” The material brought back is like a library, a history library to be exact, one that contains 4.6 billion years worth of information. That’s because the particles in the sample collected from Wild 2 in January 2004 contain material preserved from the formation of the solar system. And although Stardust is not the first spacecraft to visit a comet, it is the first designed to collect and bring back material from outside the orbit of the moon. This material contains evidence — evidence about how the sun and solar system formed.

The samples from Wild 2 have surprised scientists. They indicate that the formation of at least some comets may have included materials ejected by the early sun to the far reaches of the solar system. This information could alter the way scientists view the formation and composition of comets. Stardust curator Michael Zolensky says the samples suggest comets are composed of a mixture of materials formed at all temperature ranges, at places very near the early sun and at places very remote from it.
“The interesting thing,” Brownlee said, “is we are finding these high-temperature minerals in materials from the coldest place in the solar system.”

The particles were traveling at the speed of bullets when they were collected by Stardust. A light, glasslike aerogel in the return capsule was designed to keep the particles from being altered on impact. (Photo Credit: NASA)

The high-temperature minerals found in the Stardust sample include iron, calcium, aluminum and titanium. One surprising mineral found in the dust trail of Wild 2 is olivine, a material similar to the green beach sand found in Hawaii.

So what’s next for Brownlee, now that the Stardust Mission is over? Right now, he says he and his colleagues are immersed in a six-month long preliminary examination period.

“During this time,” he told UWTV, “we do all that we can do on a limited number of samples. This work involves all possible types of analytical instruments that can be used on small samples.”

Brownlee is also involved in a number of other missions and proposals, including the Kepler Mission, a search for habitable planets.

To learn more about the incredible Stardust Mission, what scientists are learning from that mission and how Stardust is changing the way scientists like Dr. Brownlee think about comets, watch a special program with Brownlee airing Monday, May 29th at 5 p.m. PT.

EDITOR’S NOTE: Check out Stardust@Home, a project that enables the public to help scientists locate interstellar dust in the Stardust collector.