The asteroid s solidity and primordial composition suggest Eros did not form when smaller pieces clumped together, but instead broke off an even bigger object during a huge collision as the solar system was born. Researchers long suspected chondrites came from S-class asteroids, located mostly in the inner part of the Asteroid Belt between Mars and Jupiter. These are the same chunks that formed the Earth. Nevertheless, a spiral pattern of grooves encircling the asteroid resembles layering a mystery not yet solved, Zuber said. In sketch map, dashed lines show boundaries of possible landslides.
Black squares are large blocks of rock.
The saddle is a low ridge connecting two peaks. Himeros, which is less cratered than the rest of Eros, may be the surface where Eros broke off a larger object that was struck by yet another space rock, Zuber said. Or Himeros may just be the place where part of Eros was knocked off during a collision with a similar-size object. Once thought to be a rubble pile held together only by gravity, Eros topography shows the asteroid was shaped both by gravity and by the material strength of its solid bedrock. She said the slides likely were triggered when other objects hit Eros.