NASA’s Dawn spacecraft scientists say they have discovered “unexpected details” on the surface of the giant asteroid Vesta, which is one of the brightest objects in the solar system, potentially paving the way for new insights into the geologic makeup of asteroids and how they formed and evolved through the ages.
New images and data captured via the Dawn spacecraft have apparently revealed unusual geologic features on Vesta’s surface, some of which have never been seen before on asteroids.
The Dawn scientists discussed their findings yesterday at the Lunar and Planetary Science Conference in Texas.
According to NASA, Vesta is one of the brightest objects in the solar system and the only asteroid in the main belt between Mars and Jupiter visible to the naked eye from Earth.
The space agency said Dawn found some areas on Vesta can be nearly twice as bright as others, revealing clues about the asteroid’s history.
"Our analysis finds this bright material originates from Vesta and has undergone little change since the formation of Vesta over 4bn years ago," said Jian-Yang Li, a Dawn participating scientist at University of Maryland. "We’re eager to learn more about what minerals make up this material and how the present Vesta surface came to be."
In this image from NASA’s Dawn spacecraft, the scientists said bright material extends out from the crater Canuleia on Vesta. The bright material appears to have been thrown out of the crater during the impact that created it, they said. Image by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/UMD
The scientists said bright areas appear everywhere on Vesta but are most predominant in and around craters. These areas vary from several hundred feet to around 16km across.
They revealed how rocks crashing into the surface of Vesta appear to have exposed and spread this bright material. This impact process may have mixed the bright material with darker surface material, said the scientists.
In the past, NASA’s Hubble Space Telescope had captured images of Vesta that depicted brightness variations, but yesterday the Dawn scientists said they did not anticipate such a variety of distinct dark deposits across its surface. The dark materials on Vesta can appear dark grey, brown and red, they said.
"One of the surprises was the dark material is not randomly distributed," said David Williams, a Dawn participating scientist at Arizona State University. "This suggests underlying geology determines where it occurs."
Carbon-rich asteroids hit Vesta?
NASA said the dark materials seem to be related to impacts and their aftermath. The scientists are now of the theory that carbon-rich asteroids could have hit Vesta at speeds low enough to produce some of the smaller deposits without blasting away the surface.
They said higher-speed asteroids also could have hit Vesta’s surface and melted the volcanic basaltic crust.
NASA said Vesta’s dark materials suggest the giant asteroid may preserve ancient materials from the asteroid belt and beyond, potentially from the birth of the solar system.
"Some of these past collisions were so intense they melted the surface," said Brett Denevi, a Dawn participating scientist at the Johns Hopkins University Applied Physics Laboratory.
"Dawn‘s ability to image the melt marks a unique find. Melting events like these were suspected, but never before seen on an asteroid," he said.
Dawn launched in September 2007 and is managed by NASA’s Jet Propulsion Laboratory. It is aiming to reach its second destination, Ceres, in February 2015.
The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.