astronomy: a close encounter with a wild comet

NASA’s Stardust spacecraft has revealed comet Wild 2 to be unlike any other comet known. Researchers describe the strange astronomical object in a series of papers in the June 18 issue of Science. The spacecraft came within less than 150 miles of Wild 2 in January 2004, collecting samples of the particles swirling around its nucleus and taking the most detailed, high-resolution images of a comet ever. Researchers thought the comet would look like “a dirty, black, fluffy snowball,” but instead they saw a body with steep cliffs and deep craters, indicating that Wild-2 has a relatively solid core, able to withstand impacts from other objects in space. Other surprises included finding 20 jets of gas and dust being violently ejected from the comet’s surface, as well as discovering that the dust cloud surrounding the nucleus was made up of distinct, small, dense particle swarms. Wild 2 “may turn out to be typical of other comets, but it is unlike any other type of solar system body,” Donald Brownlee of the University of Washington at Seattle and lead author of one of the Science papers, stated in a press release. The spacecraft is scheduled to return to Earth in 2006, carrying thousands of captured interstellar particles, which researchers hope will help explain how the solar system formed.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 6/22/2004.