Seems like the second-largest object in the asteroid belt is really not an asteroid at all, conclude scientists working on NASA's Dawn mission, which is currently studying a 330-mile wide body called Vesta.

"Vesta is unlike any other asteroid we have visited so far. There is nothing in the asteroid belt that you can actually compare directly with Vesta," Vishnu Reddy, a Dawn co-investigator at the Max Planck Institute for Solar System Research in Germany and at the University of North Dakota, said at the American Geophysical Union conference in San Francisco this week.


Since putting itself into orbit around Vesta in July, Dawn has found evidence that the object evolved more like a planet, with geologic processes that formed an inner core, most likely made of iron, and a mix of minerals on its surface.


Scientists don't know how Vesta survived the impacts that destroyed so many other objects in the Main Asteroid Belt, which lies between Mars and Jupiter. Vesta does bear the scars of brutal beatings, including a 290-mile diameter impact crater that left basin walls three times higher than Mount Everest.

ANALYSIS: Asteroid Has Mountain 3 Times Bigger Than Everest

"There were several large impacts that have tried to destruct Vesta," Reddy told Discovery News. "We don't know whether its general structure has something to do with the way it has been protected and still intact today. We're not sure if it has something to do with Vesta's location. We have a family of objects (meteorites) that actually are pieces of Vesta … so we know that some pieces have been taken off. The question is why has it remained intact? I don't know."

After a year of study at Vesta, Dawn is scheduled to move on to the largest object in the region, the dwarf planet Ceres.

ANALYSIS: Take a Spin Around Asteroid Vesta!

Image: This image using color data obtained by the framing camera aboard NASA's Dawn spacecraft shows Vesta's southern hemisphere in color, centered on the Rheasilvia formation. Rheasilvia is an impact basin measured at about 290 miles (467 kilometers) in diameter with a central mound reaching about 14 miles (23 kilometers) high. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA