PLANETARY SCIENCE:
Asteroids Form Rocky Relationships
Richard A. Kerr
Sightings of asteroids with companions--the latest of them just reported on the Web--are convincing astronomers that such pairs are far from rare. The first direct proof that asteroids can have moons of their own came when the Galileo spacecraft flew by 56-kilometer Ida in 1993 and photographed tiny Dactyl, a 1.5-kilometer body orbiting about 100 kilometers away. Now astronomers observing from the ground have detected a 15-kilometer satellite orbiting about 1200 kilometers from the 214-kilometer asteroid Eugenia.