Astronomers also believe that fragments gouged out of Vesta during ancient collisions have fallen to Earth as meteorites, making Vesta only the fourth solar system object, other than Earth, the Moon and Mars, where scientists have a confirmed laboratory sample.
Resolving features down to 80 km across, Hubble reveals a surprisingly diverse world with an exposed mantle, ancient lava flows and impact basins. Though only 525 km across, it once had a molten interior. This contradicts conventional ideas that asteroids essentially are cold, rocky fragments left behind from the early days of planetary formation.
Before these observations, only the smaller and less geologically diverse asteroids, Ida and Gaspra, have been observed in detail by the Jupiter-bound Galileo spacecraft. Unlike Vesta, these smaller objects are pieces torn off larger bodies by collisions that occurred perhaps only a few hundred million years ago.