Space Mountain Produces Terrestrial Meteorites   
       
   Dec. 30, 2011: When NASA's Dawn spacecraft entered orbit around giant asteroid   
   Vesta in July, scientists fully expected the probe to reveal some surprising   
   sights. But no one expected a 13-mile high mountain, two and a half times   
   higher than Mount Everest, to be one of them.   
       
   The existence of this towering peak could solve a longstanding mystery: How   
   did so many pieces of Vesta end up right here on our own planet?   
       
   http://www.nasa.gov/mission_pages/dawn/multimedia/pia14869.html   
       
   A side view of Vesta's great south polar mountain. [more] For many years,   
   researchers have been collecting Vesta meteorites from "fall sites" around the   
   world. The rocks' chemical fingerprints leave little doubt that they came from   
   the giant asteroid. Earth has been peppered by so many fragments of Vesta,   
   that people have actually witnessed fireballs caused by the meteoroids tearing   
   through our atmosphere. Recent examples include falls near the African village   
   of Bilanga Yanga in October 1999 and outside Millbillillie, Australia, in   
   October 1960.   
       
   "Those meteorites just might be pieces of the basin excavated when Vesta's   
   giant mountain formed," says Dawn PI Chris Russell of UCLA.   
       
   Russell believes the mountain was created by a 'big bad impact' with a smaller   
   body; material displaced in the smashup rebounded and expanded upward to form   
   a towering peak. The same tremendous collision that created the mountain might   
   have hurled splinters of Vesta toward Earth.   
       
   "Some of the meteorites in our museums and labs," he says, "could be fragments   
   of Vesta formed in the impact -- pieces of the same stuff the mountain itself   
   is made of."   
       
   To confirm the theory, Dawn's science team will try to prove that Vesta's   
   meteorites came from the mountain's vicinity. It's a "match game" involving   
   both age and chemistry.   
       
   "Vesta formed at the dawn of the solar system," says Russell. "Billions of   
   years of collisions with other space rocks have given it a densely cratered   
   surface."   
       
   The surface around the mountain, however, is tellingly smooth. Russell   
   believes the impact wiped out the entire history of cratering in the vicinity.   
   By counting craters that have accumulated since then, researchers can estimate   
   the age of the landscape.   
       
   http://science.nasa.gov/media/medialibrary/2011/12/30/crosssections_strip.jpg   
       
   Cross-section of the south polar mountain on Vesta with the cross sections of   
   Olympus Mons on Mars, the largest mountain in the solar system, and the Big   
   lsland of Hawaii as measured from the floor of the Pacific, the largest   
   mountain on Earth. These latter two mountains are both shield vo   
   canoes.Credit: Russell et. al. (2011), EPSC   
       
   "In this way we can figure out the approximate age of the mountain's surface.   
   Using radioactive dating, we can also tell when the meteorites were   
   'liberated' from Vesta. A match between those dates would be compelling   
   evidence of a meteorite-mountain connection."   
       
   For more proof, the scientists will compare the meteorites' chemical makeup to   
   that of the mountain area.   
       
   "Vesta is intrinsically but subtly colorful. Dawn's sensors can detect slight   
   color variations in Vesta's minerals, so we can map regions of chemicals and   
   minerals that have emerged on the surface. Then we'll compare these colors to   
   those of the meteorites."   
       
   Could an impact on Vesta really fill so many museum display cases on Earth?   
   Stay tuned for answers..   
       
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   After revealing more Vesta surprises, Dawn will depart next summer for Ceres,   
   where it will arrive in 2015. Dawn's mission to Vesta and Ceres is managed by   
   the Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission   
   Directorate in Washington. JPL is a division of the California Institute of   
   Technology in Pasadena. Dawn is a project of the directorate's Discovery   
   Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala.   
   UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp.   
   in Dulles, Va., designed and built the spacecraft. 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. More information about the Dawn mission is at:   
   http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov. To follow the mission   
   on Twitter, visit: http://www.twitter.com/NASA_Dawn .   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.71   
    * Origin: NCS BBS (1:3828/7)