The asteroid won't come this close again for more than a thousand years. JM8 bears a striking resemblance to Toutatis, a similar-sized, slowly rotating object also studied in detail with radar, said Dr. Scott Hudson of Washington State University, who is an expert in using radar images to determine the shapes of asteroids. However, although collisions are thought to be the primary process that determines asteroid spin states, we don't know how the slow, complex states come about. The radar imaging technique uses transmissions of sophisticated coded waveforms and computer determinations of how echoes are distributed in range and frequency, instead of their angular distribution, as in normal optical pictures. To get that kind of resolution with an optical telescope, you'd need a mirror several hundred meters across.
Radar certainly is the least expensive way of imaging Earth-approaching objects.
We also see a concavity that is about half as wide as the asteroid itself, but we're not sure yet whether or not it's an impact crater. This is hardly the first time that radar has revealed a near-Earth asteroid with peculiar characteristics, said Dr. Steven Ostro of JPL, who has led dozens of asteroid radar experiments. Radar studies have revealed a stunning array of exotically shaped worlds with compositions ranging from solid metal to low-density carbonaceous rock and rotation periods ranging from 11 minutes to more than a week. I really envy the coming generations of space explorers who will visit them. In addition to Benner, Hudson, Margot, Nolan and Ostro, the radar team included Drs.