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'Dawn' breaks discovery of double crater on Vesta, says NASA

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The NASA Dawn spacecraft mission has made some surprising discoveries about the asteroid Vesta, the parent body of an asteroid belt between Mars and Jupiter.

Carol Raymond, with the Jet Propulsion Laboratory, told KPCC that the data Dawn gathers could help scientists better understand how Earth and other planets emerged.

"Vesta’s history appears to be more similar to rocky terrestrial planets -  Mars, Mercury, and the Earth’s moon - than to its larger sibling Ceres, which will be the second target of the Dawn mission," says Raymond.

Scientists say cosmic collisions, likely with a smaller asteroids, are to blame for Vesta's scars. High-resolution images have revealed, however, that two massive overlapping craters are creating the huge depression (the southern hemisphere depressions were first seen the Hubble Space Telescope).

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

Scientists determined that a rim nearby to a 310-mile-wide crater belonged to a smaller, older crater gouged by an impact 2 billion years ago.

"It looked kind of weird. We thought, 'What the heck is that?'" recalled Paul Schenk of the Lunar and Planetary Institute in Houston who is part of the mission. It had been obscured by the larger crater.

David O'Brien, a mission team member from the Planetary Science Institute in Tucson, says debris blown out by the double impact was enough to fill 400 Grand Canyons.

Some of the material fell to Earth -- scientists estimate that 1 out of every 20 meteorites found on our planet came from the frosty Vesta.

Considered an atypical asteroid by scientists, Vesta survived the pounding without shattering. At 330 miles across, it's the second largest object in the asteroid belt.

Dawn will fade from Vesta's view sometime in August to shed light on an even larger celestial body, Ceres. The spacecraft is expected to arrive on that asteroid in three years.


With contributions from KPCC staff

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