"Vesta had sufficient radioactive material inside when it coalesced, releasing heat that melted rock and enabled lighter layers to float to the outside. Scientists call this process differentiation," Dr.
Phillips explained. "That's why Dawn scientists prefer to think of Vesta as a protoplanet which is the next step up from a planetoid. It is a dense, layered body that orbits the
Sun and began in the same fashion as Mercury, Venus, Earth and Mars, but somehow never fully developed."
Dr. Phillips also said "Other space rocks have collided with Vesta and knocked off bits of it. Those became debris in the asteroid belt known as Vestoids, and even hundreds of meteorites that have ended up on Earth. But Vesta never collided with something of sufficient size to disrupt it, and it remained intact. As a result, Vesta is a time capsule from that earlier era."
Asteroid, planetoid, protoplanet? How astronomers will ultimately classify Vesta is unknown, but NASA's Dawn spacecraft is about to get some up close views of this oh, so very heavenly body. Stay tuned.
Lou Varricchio, M.Sc., was a science writer at the NASA Ames Research Center in California. He maintains his space agency connections through the NASA-JPL Solar System Ambassador Program, an education outreach effort of the Jet Propulsion Laboratory.