[meteorite-list] University Of Hawaii Scientist May Help Lead Asteroid Mission

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:42:03 2004
Message-ID: <200101231629.IAA19552_at_zagami.jpl.nasa.gov>

http://starbulletin.com/2001/01/22/news/story6.html

     UH scientist may help lead asteroid mission
     By Helen Altonn
     Star-Bulletin (Hawaii)
     January 22, 2001

     University of Hawaii planetary scientist Thomas McCord is one of
     the key investigators in a proposed mission to explore two of the
     first bodies in the solar system: asteroids Ceres and Vesta.

     The mission is called Dawn because the two most massive asteroids
     have preserved a record of the earliest moments of formation of
     terrestrial planets at the dawn of the solar system.

     The University of California-Los Angeles proposed the mission,
     which NASA selected for further study. Orbital Sciences Corp. and
     the Jet Propulsion Laboratory are partners in the venture, and
     various universities are participating.

     McCord, with the Hawaii Institute of Geophysics and Planetology,
     said other asteroids have been studied in fly-by missions, but
     they were very small.

     "These are the largest asteroids, and they are evolved to some
     extent. That is, they're not just inert rocks. They're big enough
     that there has been thermal evolution."

     Vesta is the brightest asteroid and the only one ever seen with
     the naked eye. It has lava on the surface, which McCord discovered
     in 1972.

     The basalts indicate the asteroid is hot enough inside to melt the
     rock and volcanism has occurred -- most likely much earlier in
     time, he said.

     Ceres, the largest known asteroid, was the first discovered in the
     solar system 200 years ago with a small telescope atop the royal
     palace in Palermo, Italy.

     McCord said Ceres appears to have water in minerals on the
     surface, evolving from materials inside the asteroid. But so far,
     no basalt, lavas or evidence of volcanism or melting of rocks have
     been found, he said.

     "It is extremely interesting, to say the least," he said, because
     the two asteroids are so different.

     Meteorites believed to be from Vesta indicate it was formed in
     only 5 million to 15 million years, while it took Mars about 30
     million years and the Earth, 50 million.

     No meteorites have been identified from Ceres, but it also is
     expected to have formed in the first 10 million years.

     Scientists are interested in determining Vesta's volcanic history
     and how extensive the volcanism was, McCord said, "so we can apply
     that knowledge to understanding how bodies in general of that size
     evolved."

     The asteroids are smaller than Earth's moon but larger than most
     or all of the asteroids, he said. "They're in an in-between size
     range, and we don't know how those small bodies evolved thermally
     very well.

     "Here we have two examples, both thermally evolved, but both
     different ways -- one with release of water and hydrated minerals,
     the other with volcanism."

     Perhaps the objects were made of different materials when they
     were formed, one with very wet material and the other not, McCord
     suggested.

     "But we don't know. That takes some special creation itself. It's
     not too logical. At the moment there is no explanation for
     different evolution."

     McCord will lead work with two spectrometers being built by
     Germans for the spacecraft. He has worked with them for years on
     development of instruments for space missions.

     Another unique aspect of the Dawn mission will be use of ion
     engines to power the spacecraft to the asteroid belt, McCord
     noted.

     It will orbit Vesta in an ever-tightening circle, then spiral
     outward and head to Ceres for a rendezvous.

     "This would be the first full science mission using that
     propulsion system," McCord said. The thrust is weaker but lasts
     longer, so the spacecraft can go farther, he said.

     If it performs well, he said, a number of science exploration and
     engineering missions could be done that are now impractical to do.

     Scientists are preparing a detailed plan for NASA approval and
     funding of the Dawn mission, scheduled in July 2005.

     UCLA lead investigator Christopher Russell said, "The data
     returned by the Dawn mission will open up a treasure trove of
     information" in meteorites and asteroid samples.

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Received on Tue 23 Jan 2001 11:29:30 AM PST