asteroids

Posted by smartshyam on Nov. 11, 2013, 8:50 a.m.

The discovery of mysterious rocks on the brightest large asteroid in the solar system, Vesta, deepens the mystery surrounding the huge object's origins, researchers say.

Vesta is the second-largest asteroid in the solar system. The 330-mile-wide (530-kilometer) protoplanet is also the brightest large asteroid, with a surface about three times more luminous than Earth's moon.

The vast size of Vesta helped it hold onto its heat during its birth, enabling lighter molten rock to float outward while denser rock sank inward. As such, Vesta developed an onion-like structure like Earth's, differentiated into an outer crust, a central core and a mantle layer between the two. [Photos of Asteroid Vesta by NASA's Dawn Probe]

Cosmic impacts regularly blast rocks off Vesta. A class of meteorites known as diogenites are thought to come from Vesta's mantle or lower crust, and sometimes possess substantial amounts of a green mineral known as olivine, a major ingredient of Earth's upper mantle. As such, investigators expected to find olivine in places on Vesta where large impacts unearthed deeply buried rocks.

Now scientists have spotted olivine on Vesta, but not where it was expected it to be. Instead of discovering olivine in Vesta's deep southern craters, they surprisingly found it near shallower northern craters, mixed with the most common type of rock found on Vesta's surface. This suggests olivine might exist within Vesta's crust instead of deeper within its mantle.

Researchers analyzed data from NASA's Dawn spacecraft, which became the first probe to visit Vesta when it orbited the protoplanet in 2011 and

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