Asteroid Hunters; April 1993; Scientific American Magazine; by Corey S. Powell; 2 Page(s)

Astronomers who stalk the stray rocks that hurtle through the earth's part of the solar system are literally a rare breed. "Fewer people are involved in searching for near-earth asteroids than work in a McDonald's," reports David Morrison of the National Aeronautics and Space Administration's Ames Research Center. One of the most noteworthy is Steven J. Ostro of the Jet Propulsion Laboratory in Pasadena, Calif.--the world's sole expert in studying asteroids by radar.

Last December, Ostro and his collaborators bounced a 400,000-watt radio signal from the Goldstone Deep Space Communications Complex in California off the asteroid Toutatis as it passed within a celestial hairbreadth of the earth. When Ostro's team analyzed the echoes, it recovered a "breakthrough" portrait of a remarkable object that consists of two battered rocks stuck together like Siamese twins. Three years ago Ostro and his colleagues produced a much fuzzier image of the asteroid Castalia, which indicated that it, too, is binary. "It's an amazing thing," says Morrison, who likens the discovery of twin asteroids to Galileo's observation that many stars are double.