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What Dawn Found: NASA Unveils Discoveries on Giant Asteroid

The avocado-shaped asteroid's history of celestial collisions might help reveal more about how Earth and other planets emerged

By Jonathan Lloyd

| Friday, May 11, 2012 | Updated 6:36 AM PDT

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A view of asteroid Vesta's south pole, which might provide a celestial record of how Earth and other planets emerged.

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The high-resolution imagery of Spacecraft Dawn has revealed more about asteroid Vesta, a "left-over planetary building block" that took a celestial pounding and might help scientists better understand how Earth and other rock planets emerged.

Science: Dawn at Vesta | NASA: Dawn Mission | Where's Dawn?

What Dawn found was the subject of a news conference with project managers Thursday at NASA's Jet Propulsion Laboratory in Pasadena. The findings, reported in the journal Science, indicate Vesta was hammered by celestial objects, probably smaller asteroids, including a back-to-back clobbering that might have shattered any other asteroid.

But Vesta is still around to tell its story.

"Vesta got whacked twice with large impacts,'' said Christopher Russell of the University of California, Los Angeles, who leads a team of scientists studying the asteroid.

The double strikes were only recently revealed using Dawn's high-resolution imagery.

That Vesta has been taking a pounding for so long basically makes the rock a pock-marked record of how objects in the solar system smashed into each other. Some of the debris from celestial collisions was hurled into space and fell to Earth as meteorites.

"Vesta has really expanded the ideas about the diversity that we might encounter as we go out into the asteroid belt and look at the myriad pieces that might be providing us with information about the early solar system," said JPL's Carol Raymond, Dawn deputy principal investigator.

About 1 out of every 20 meteorites found on Earth came from Vesta. Scientists described it as a "parent" of a class of meteorites that have arrived on Earth.

The double-impacts occurred about one billion years apart, according to scientists. The older of the two craters was carved out about 2 billion years ago. It was, until recently, obscured by the larger crater.

Spacecraft Dawn launched in 2007 en route to giant space rocks in an asteroid belt that orbits the sun between the orbits or Mars and Jupiter. In a belt of potato-shaped rocks, Vesta stands out -- it's shaped like an avocado and it is the second-largest object in the asteroid belt.

Dawn will leave Vesta in August and head to an even larger asteroid -- Ceres. It is expected to arrive on Ceres in 2015.