Data returned by the NEAR spacecraft show that the asteroid Eros is not just a single, solid space rock. Previous images had indicated the asteroid might have regolith, a loose layer of rock bound to the asteroid by gravity. Recent observations, announced at the conference, confirm that suspicion.

The rubble may represent leftovers from catastrophic events, when other space rocks crashed into Eros, researchers said. Eros certainly bears the scars of a violent past.

"Its a battered place," said Cornell Universitys Dr. Peter Thomas. "There are lots of boulders scattered on the surface."

Researchers have speculated that some asteroids are mostly made of loose collections of smaller rocks. If an asteroid were ever found to be on a collision course with Earth, knowing if it were a solid rock or a rubble pile might determine what method to use in an effort to deflect the space rock.

Initial scans of the asteroid with an X-ray spectrometer have detected the presence of magnesium, iron, silicon and possibly aluminum and calcium.

NEAR rendezvoused with Eros on February 14 and currently orbits the asteroid at a distance of about 124 miles (200 kilometers). Scientists plan to lower NEARs orbit to about 62 miles (100 kilometers) in April.