October 27, 1998

Space shuttle experiment features UF handiwork

By RAY WASHINGTON
Sun Staff Writer

GAINESVILLE - Much of the nation and the world will be transfixed this week as 77-year-old former astronaut and U.S. Sen. John Glenn hurls into space as a human experiment to help scientist explore how the body comes apart at the end of life.

But University of Florida astrophysicist Bo Gustafson and his colleagues also will be focused on an experiment that uses a UF-designed instrument placed aboard Discovery to shed light on a how dust particles come together at the beginning of planetary creation.

"It all really starts with dust," said Gustafson, creator of a light-scattering unit that's central to a larger instrument designed to reveal the secrets of dust agglomeration.

The unit, built at UF in 1996, is designed to "test theoretically models of how light propagates through a cloud of gas or dust."

Before planets can form, Gustafson said, dust grains must come together to form planetesimals, which then are pulled together by gravity to form planets.

The formation of planets from planetesimals is relatively well understood. But the process by which planetesimals are formed from dust particles is less clear.

To explain the possibilities scientists have developed various theories, some of which conflict. Fundamental to most theories is the role of the transfer of radiative energy in the formation process. Energy can either cause gas to evaporate, or to condense, on dust particles. That, in turn, influences whether colliding dust particles stick together.

Gustafson and his co-investigators want to gather data that could be useful in creating new theoretical models that would help explain the process. Current theory doesn't do that well, positing a planetesimal formation process that would take more time than the few hundreds of millions of years in which planets are thought to form.

"The aggregation phase, where individual dust particles stick together and also break apart as they collide is, I have to say this, a 'sticking point,'" Gustafson said.

Earth has not proved to be the ideal environment in which to test dust theories. To overcome the limits gravity places on the experiments, scientists have attempted to test dust reactions in micro-gravity situations by dropping instruments from specially designed tall towers, or by sending them aloft on rocket flights. But towers provide only seconds to observe the dust reactions, and rockets allow only minutes. The shuttle will allow scientists the relative luxury of days in which to measure dust reactions.

"We need to simulate many different situations," Gustafson said. "We can't just take a few numbers. We need a range. And this range takes time."

The Discovery dust experiments - a collaboration between UF and German scientists - represents the first shuttle-based experiments for UF's Department of Astronomy in a decade. Success could mean an important place for UF in NASA's program for studying the beginnings of life in the universe, Gustafson said.