[meteorite-list] NASA's Dawn Sees New Surface Features on Giant Asteroid Vesta

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 21 Mar 2012 10:58:12 -0700 (PDT)
Message-ID: <201203211758.q2LHwCWb006149_at_zagami.jpl.nasa.gov>

March 21, 2012

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

Jia-Rui C. Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
jccook at jpl.nasa.gov

RELEASE: 12-091

NASA'S DAWN SEES NEW SURFACE FEATURES ON GIANT ASTEROID VESTA

WASHINGTON -- NASA's Dawn spacecraft has revealed unexpected details
on the surface of the giant asteroid Vesta. New images and data
highlight the diversity of Vesta's surface and reveal unusual
geologic features, some of which were never previously seen on
asteroids.

Vesta is one of the brightest objects in the solar system and the only
asteroid in the so-called main belt between Mars and Jupiter visible
to the naked eye from Earth. Dawn found that 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 4 billion
years ago," said Jian-Yang Li, a Dawn participating scientist at the
University of Maryland, College Park. "We're eager to learn more
about what minerals make up this material and how the present Vesta
surface came to be."

Bright areas appear everywhere on Vesta but are most predominant in
and around craters. The areas vary from several hundred feet to
around 10 miles across. Rocks crashing into the surface of Vesta seem
to have exposed and spread this bright material. This impact process
may have mixed the bright material with darker surface material.

While scientists had seen some brightness variations in previous
images of Vesta from NASA's Hubble Space Telescope, Dawn scientists
also did not expect such a wide variety of distinct dark deposits
across its surface. The dark materials on Vesta can appear dark gray,
brown and red. They sometimes appear as small, well-defined deposits
around impact craters. They also can appear as larger regional
deposits, like those surrounding the impact craters scientists have
nicknamed the "snowman."

"One of the surprises was the dark material is not randomly
distributed," said David Williams, a Dawn participating scientist at
Arizona State University, Tempe. "This suggests underlying geology
determines where it occurs."

The dark materials seem to be related to impacts and their aftermath.
Scientists theorize carbon-rich asteroids could have hit Vesta at
speeds low enough to produce some of the smaller deposits without
blasting away the surface.

Higher-speed asteroids also could have hit the asteroid's surface and
melted the volcanic basaltic crust, darkening existing surface
material. That melted conglomeration appears in the walls and floors
of impact craters, on hills and ridges, and underneath brighter, more
recent material called ejecta, which is material thrown out from a
space rock impact.

Vesta's dark materials suggest the giant asteroid may preserve ancient
materials from the asteroid belt and beyond, possibly 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 in Laurel, Md.
"Dawn's ability to image the melt marks a unique find. Melting events
like these were suspected, but never before seen on an asteroid."

Dawn launched in September 2007. It will reach its second destination,
Ceres, in February 2015.

"Dawn's ambitious exploration of Vesta has been going beautifully,"
said Marc Rayman, Dawn chief engineer at NASA's Jet Propulsion
Laboratory (JPL) in Pasadena, Calif. "As we continue to gather a
bounty of data, it is thrilling to reveal fascinating alien
landscapes."

Dawn's mission is managed by JPL for NASA's Science Mission
Directorate in Washington. 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.

To view the new images, visit:

http://www.nasa.gov/dawn
        
-end-
Received on Wed 21 Mar 2012 01:58:12 PM PDT