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In images from Dawn's framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes. Vesta is unique among asteroids visited by spacecraft to date in having such wide variation, supporting the notion that it is transitional between the terrestrial planets - like Earth, Mercury, Mars and Venus - and its asteroid siblings. Image and caption courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

When scientists examined a photograph of Vesta, the second largest object in the asteroid belt, they were surprised to find what the massive object was made of.

Vesta is composed of many different layers of rock and material. This means that Vesta’s classification is somewhere between that of an asteroid and a planet. It’s one of the most ‘unique’ asteroids a spacecraft has visited, according to NASA.

Shall we call it a plasteroid? Or a planetoid? Maybe Vesta is a dwarf planet?

“Vesta’s iron core makes it special and more like terrestrial planets than a garden-variety asteroid,” said Carol Raymond, Dawn’s deputy principal investigator at NASA’s Jet Propulsion Laboratory in a release. “The distinct compositional variation and layering that we see at Vesta appear to derive from internal melting of the body shortly after formation, which separated Vesta into crust, mantle and core.”

The discovery was due to NASA’s Dawn Mission, which is now orbiting Vesta at its closest distance yet.

This image of the giant asteroid Vesta was obtained by NASA's Dawn spacecraft on Nov. 27 as it was spiraling down from its high altitude mapping orbit to low altitude mapping orbit. Low altitude mapping orbit is the closest orbit Dawn will be making, at an average of 130 miles above the giant asteroid's surface. Image and caption courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn has been orbiting Vesta since this past July. The spacecraft will leave the giant object in July 2012 for its next adventure: researching the dwarf planet Ceres.

Read more about asteroids here.