[meteorite-list] Finding Bits Of Mars On Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:03 2004
Message-ID: <200401161906.LAA16146_at_zagami.jpl.nasa.gov>

http://www.cleveland.com/news/plaindealer/index.ssf?/base/news/1074249382127740.xml

Cleveland geologist's cool job: finding bits of Mars on Earth
John Mangels
The Plain Dealer (Cleveland, Ohio)

Long before NASA's robotic rovers began gingerly prospecting Mars' rusty
surface, Ralph Harvey was recovering stones from the Red Planet. And though
the last Apollo crew left the lunar highlands 31 years ago, Harvey and his
colleagues are still collecting moon rocks.

Harvey isn't an astronaut, and he has never left Earth. The planetary
geologist from Case Western Reserve University leads a team that each year
scours the blue ice of the Antarctic - the best meteorite-hunting grounds on
the planet.

The samples they have retrieved are giving scientists new insights about
conditions in the galactic nursery that spawned our solar system.

"It's a space mission for me, without the helmet," said Harvey, who returned
to Cleveland two weeks ago. Other team members will keep hunting for
meteorites and scouting for future search sites until late January.

With President Bush's recently announced plan to return American astronauts
to the moon and eventually voyage on to Mars, scientists are anticipating
the hands-on study of those bodies' quirky and sometimes mysterious geology.

But such research doesn't necessarily require a rocket trip.

The accommodating solar system sends some of its samples to Earth in the
form of meteorites - asteroid rubble snagged by our planet's gravity and, as
researchers have only recently realized, pieces of the moon, Mars, and
possibly other nearby planets, too.

The lunar and Martian fragments were blasted into space by asteroid or comet
strikes.

Meteorites have fallen to the ground for eons all across the Earth, but in
most places are neatly camouflaged by our own planet's rocky surface.

Not so in Antarctica, nature's version of white linoleum. Anything that
plops onto the vast, windswept ice sheets at the bottom of the world stands
out like a piece of chocolate on a freshly mopped kitchen floor.

The six Apollo moon-landing missions between 1969 and 1972 returned 2,200
samples of rocks, pebbles and dust. Since 1976, the Antarctic expeditions
led by Harvey and his predecessor, University of Pittsburgh geologist
William Cassidy, have recovered nearly 14,000 meteorite samples, including
seven from the moon and five from Mars.

"There are so many interesting samples in the [Antarctic] collection - they
really form the backbone of planetary science," said meteorite curator Kevin
Righter of the astromaterials collection at NASA's Johnson Space Center in
Houston. "The service that Ralph and Bill Cassidy have done for the
community is huge."

While this season's search team combs the LaPaz ice field 217 miles
northwest of the South Pole Station, NASA's Spirit rover is preparing to
roam the bottom of an immense crater at the Martian equator, scrutinizing
rocks along the way. Humans and robots are doing similar work, in similarly
harsh conditions (Mars is colder, but in Earth's thicker atmosphere, the
winds blow much harder).

NASA intentionally modeled its robots on human field geologists like Harvey,
giving them the equivalent of a rock hound's hammer and magnifying lens. But
to minimize risk, the rovers are tentative and child-like, requiring a good
deal of pointing and prodding from their human handlers 170 million miles
away to get from one rock to the next.

"Human beings have this amazing ability to summarize and prioritize a scene
in an instant, to move right to the keys to the puzzle," said Harvey, who
helped test a NASA-financed meteorite-hunting rover during the 1999
Antarctic expedition. "Robots are a long way from that."

The Antarctic searches also are far cheaper than their Mars counterparts. It
cost roughly $1 million for the 12-member team's two-month expedition, with
grants from NASA and the National Science Foundation. At $820 million,
Spirit and its twin rover Opportunity - scheduled to land on Mars Jan. 24 -
are expected to last at least three months before their batteries die.

The Mars rovers' advantage is what geologists call "ground truth" - the
rocks the robots examine are linked to, and convey specific contextual
geologic information about, the craters or other sites in which they are
found. That can't be said of meteorites that end up in the Antarctic ice,
since their origins are more vague.

Still, the Antarctic samples have secrets to reveal, and scientists can
subject them to sophisticated lab analysis that the rovers can't duplicate.
Even the most common asteroids are imprinted with a geologic and chemical
record of the conditions at the solar system's birth more than 4.5 billion
years ago, and with the changes the rocks have experienced in their long
journey through space and time. Those clues are helping researchers better
understand the distribution of materials and the nature of forces that
wrought planets and suns from great roiling clouds of interstellar dust.

Some asteroids have picked up hitchhikers, tiny grains of diamond, aluminum
oxide, graphite and other minerals that couldn't have been produced by
processes in our solar system.

These rare components appear to have originated far from here, in the exotic
and violent neighborhoods of massive stars or recently exploded supernovae.

This year's Antarctic search has been especially productive, Harvey said,
yielding 655 meteorite samples as of last Saturday. One of the best finds
was a 50-pound basketball-sized specimen whose interior was flecked with
chondrules - distinctive round deposits that are some of the first solids to
appear as dust coalesced into our solar system. Scientists still don't know
exactly how they formed.

The LaPaz ice field proved to be a good hunting ground, but Harvey's team
feels a particular urgency to return next season to finish the job.

Word of their success no doubt will spread, and private expeditions are
almost certain to follow.

The meteorites the National Science Foundation crew finds are made available
to scientists from around the world for study. Rocks collected by the
private crews end up in private collections or are sold to bidders.

"God bless the people who realize in science how important altruism can be,"
Harvey said.

"The expeditions who use our information to help a tourist pick up a
meteorite and lock it away in a private collection, it's a travesty to me."

To reach this Plain Dealer reporter:

jmangels_at_plaind.com, 216-999-4842
Received on Fri 16 Jan 2004 02:06:35 PM PST