Astronomers operating two huge radar telescopes have taken pictures of a near-Earth asteroid discovered barely three months ago. They used the Arecibo Radar Observatory in Puerto Rico and the Goldstone Solar System Radar in California like million-watt flashlights to bounce powerful radar pulses off the two-mile-wide flying mountain, dubbed 1999 JM8, as it flew to within 5.3 million miles of Earth during early August. Images constructed from the radar reflections reveal craters 330 feet wide and a surface that says a lot about how life has panned out so far for 1999 JM8.

"The density of the craters suggest that the surface is geologically old, and is not simply a 'chip' off a parent asteroid," says Michael Nolan of Arecibo.

Various theories hold that asteroids are relics that never formed a planet, like 1999 JM8, or the shattered debris of larger planetoids that careened into each other.

But scientists are particularly excited about what observations of this quality bode for the future of Earth-based asteroid astronomy.

"Our finest resolution is 15 meters (49 feet) per pixel, which is finer than that obtained of any other asteroid, even by spacecraft," says Arecibo's Dr. Jean-Luc Margot of the 1999 JM8 images. "To get that kind of resolution with an optical telescope, you'd need a mirror several hundred meters across."

Arecibo is benefiting from a recent upgrade that might let it bounce signals off thousands of asteroids throughout the main belt, which lies between Mars and Jupiter.

Radar astronomers are also enjoying the fruits of several surveys now underway to detect Earth-orbit crossing asteroids. It was one of these surveys, the MIT/U.S. Air Force Lincoln Near Earth Asteroid Research project, that found 1999 JM8 with a New Mexico-based telescope on May 13, 1999.

"The discovery of this object weeks before its closest approach was a stroke of luck," says JPL's Lance Brenner, who lead the radar mapping team. "The asteroid won't come this close again for more than a thousand years."