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Mission to asteroid answers, raises questions

Posted May 11, 2012

Dawn spacecraft at Vesta (Courtesy NASA/JPL)

NASA announced initial findings of the Dawn mission currently studying the giant asteroid Vesta on Thursday.

Researchers describe Arizona-sized Vesta as a “special fossil," a proto-planet left over from the time when our solar system was forming. Thursday's findings confirmed some theories and brought others into question.

"Dawn's visit to Vesta has confirmed our broad theories of this giant asteroid's history, while helping to fill in details it would have been impossible to know from afar," said Carol Raymond, deputy principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Study of Vesta started long before Dawn’s launch in 2007. Telescope observations both from the ground and the Hubble Space Telescope mapped Vesta’s battered surface leading researchers to theories about the asteroid’s violent past.

For years, scientists have been studying howardite-eucrite-diogenite (HED) meteorite samples believed to have come from Vesta. Dawn confirmed those meteorites to be from a Connecticut-sized crater at Vesta’s south pole based on the unique mineral composition there. You can see a piece of Vesta in the Postcards from Space exhibit at the recently opened Nature Research Center at Raleigh's Museum of Natural Sciences. A sizable sample from the nearly 600 pounds observed falling in Western Australia in 1960 is on display there.

One of the biggest surprises for investigators was the relative young age of craters on Vesta. These impacts were found to have occurred about 1-2 billion years ago, reshaping scientists’ view of how the asteroid belts have evolved over time.  

"The large impact basins on the moon are all quite old," said David O'Brien, a Dawn participating scientist from the Planetary Science Institute in Tucson, Ariz. "The fact that the largest impact on Vesta is so young was surprising."

"Comparing the two gives us two story lines for how these fraternal twins evolved in the early solar system." said Vishnu Reddy, of the Max Planck Institute for Solar System Research in Germany.

Vesta’s similarity to planets was reinforced by the discovery of an iron core about 137 miles in diameter. The core could even be large enough to help generate an Earth-like magnetic field.

Scientists expect to learn much about the early days of our solar system from this mission. It provides study of two very different targets for the price of one mission. Vesta’s dry, evolved surface indicated ancient lava flows, much like the inner planets.

Dawn will continue observations at Vesta until Aug 26. It then departs for the 2 1/2 year trip to dwarf planet Ceres which, with its clay-like surface and evidence of water, is similar to the icy moons of the outer planets.

Mark your calendar for Astronomy Days

You can see that piece of Vesta for yourself at Astronomy Days, May 19, and 20 at the North Carolina Museum of Natural Sciences. Families can also walk through NASA’s Destination Station exhibit and get involved with other space-themed exhibits, workshops and activities during this free event.

There will also be presentations on exploration of Pluto and beyond, the burgeoning field of astrobiology, the origins of planetary systems in our galaxy and more.

I’ll be giving a talk on the U.S.’s transition from the NASA’s Space Shuttle program to commercially developed and run programs to get astronauts from American soil to the International Space Station Saturday morning at 9:30 a.m. in the spectacular, three-story Daily Planet theater and again the following day at 3:15 p.m. Stop by and say hi!

For more information see http://naturalsciences.org/programs-events/astronomy-days-0

Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.


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