In mid-July, NASA's Dawn spacecraft swung into a yearlong orbit around Vesta, the second-most massive object in the asteroid belt between Mars and Jupiter. Since then, it has been snapping pictures of the protoplanet's rugged surface and beaming them back to Earth, revealing images of craters, mountains, rocky plains and steep slopes.
On December 12, Dawn maneuvered into its closest orbit yet around the giant asteroid, beginning a new phase of observations, according to NASA. The spacecraft is now circling Vesta at an altitude of about 130 miles.
Scientists have recently concluded that Vesta evolved more like a planet than an asteroid with geologic processes that likely formed an inner iron core.
"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, Pasadena, Calif. "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."
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