[meteorite-list] Mountain on Vesta Produces Terrestrial Meteorites

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 30 Dec 2011 19:34:11 -0800 (PST)
Message-ID: <201112310334.pBV3YBZs001394_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/science-news/science-at-nasa/2011/30dec_spacemountain/

Space Mountain Produces Terrestrial Meteorites
NASA Science News
December 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?

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.

"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 at NASA <http://science.nasa.gov/>

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
<http://dawn.jpl.nasa.gov/>. To follow the mission on Twitter, visit:
http://www.twitter.com/NASA_Dawn .
Received on Fri 30 Dec 2011 10:34:11 PM PST