May 10, 2012
Dawn Mission Reveals Asteroid Vesta’s Secrets
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Lee Rannals for RedOrbit.com
Carol Raymond, Dawn deputy principal investigator at NASA´s Jet Propulsion Laboratory, said that Dawn's success has transformed scientists' perspective of Vesta from a fuzzy form, into a planetary body.
She said that the asteroid formed within 2 million years after the first solids formed in the solar system.
"We know now that Vesta is the only intact planetary building block surviving from the early days in the solar system," she said during a NASA news conference about the findings.
The findings confirm a theory that Vesta was the parent asteroid of Howardite—Eucrite—Diogenite (HED) meteorites that have been found on Earth.
These meteorites are a complex assortment of rocks, whose properties indicate that it came from an igneous process not much different from the magmatic rocks found on Earth.
Harry McSween, of the Dawn surface composition working group and the University of Tennessee, Knoxville, said Vesta's surface is compositionally heterogenous, like HED meteorites.
He said that Dawn's observations have convinced "most of us" that the asteroid is the HED parent body.
Vesta is unlike any other object that we have visited in our solar system, according to Vishnu Reddy, Dawn framing camera team member, Max Planck Institute for Solar System Research.
He said there is a "wide range of brightness variation" on the asteroid. On some parts, "we see areas as bright as snow," Reddy told the conference.
As part of what shows the age of the asteroid, the scientists said they were unable to see original crust on Vesta because it has been pulverized by impacts.
David O´Brien, Dawn participating scientist and part of the Planetary Science Institute, said Dawn has revealed a wide range of craters on Vesta, and scientists have catalogued close to 2,000 craters on the surface of the asteroid.
He said that of the 2,000 craters, the hardest craters to pick out among the images are the largest ones.
"Vesta dates back to the beginning of the solar system," O'Brien said at the conference. "Its been recording impacts from asteroids ever since that point."
To show the age, one crater impact known as the Rheasilvia Basin is from a 1 billion year old impact, while the Veneneia Basin is from a 2 billion year old impact. Scientists are able to determine the age of these impacts through the global crater catalogues of impacts.
In the southern region of Vesta, there is relatively few craters found, compared to the northern region which has a very densely cratered surface. O'Brien said that this is because the formation of the Rheasvilvia impact covered that area, essentially resurfacing the southern surface.
"An age of about 1 billion years for Rheasilvia is unexpectedly young," NLSI team member Dr. Simone Marchi, lead author a paper published in the journal Science about the new analysis, said in a press release.
"This result has important implications for our understanding of the evolution of the Vesta, its asteroid family and the inner main asteroid belt in general. We have just started exploring Vesta's secrets, and I'm sure other intriguing results will come along shortly."
O'Brien also mentioned that there is 250,000 cubic miles of surface material that has ejected from this asteroid into space, which is enough to fill the Grand Canyon a thousand times over. This also adds to the evidence that Vesta is the parent body of the HED meteorites.
Because of HED meteorites found on Earth, McSween said at the news conference that "we are now unraveling the geologic history of Vesta in ways that would not be possible without samples."
Image 2 (below): This image, made from data obtained by NASA's Dawn spacecraft, shows the mineral distribution in the southern hemisphere of the giant asteroid Vesta. Image credit: NASA/JPL-Caltech/UCLA/INAF/MPS/DLR/IDA [ Image Gallery ]