[meteorite-list] Scientists Comb Antarctica For Meteorites

[Ron Baalke]

http://www.columbusdispatch.com/science/science.php?story=dispatch/2006/11/21/20061121-D6-01.html

PICKING UP THE PIECES

To paint a picture of our universe, a team of scientists combs
Antarctica for meteorites

Mike Lafferty
THE COLUMBUS DISPATCH
November 21, 2006

When Ralph Harvey scans Antarctica's icy terrain, it becomes clear just
how rough-and-tumble the solar system was 4 billion years ago.

Large planetary bodies colliding, asteroids smashing into one another,
pieces of rock flying everywhere.

"At a minimum, the inner solar system had a rough coming-of-age moment,"
said Harvey, a Case Western Reserve University geologist who spends a
month or so in November and December with a team that combs icy
Antarctic wastes for meteorites.

Scientists want to know as much as possible about this time of planet
formation. Meteorites, which amount to the dust left over from the
cataclysm, provide a glimpse into that past.

And Antarctica is a perfect spot to find them.

"If you want to find something, lay it out on a big white sheet. If you
find any rocks out there, they had to fall from the sky," said Harvey,
who heads the U.S. Antarctic Search for Meteorites, which has its
headquarters at Case Western.

In 30 years, the team has discovered about 15,300 meteorites, all of
which are available for scientists to study.

About one in a thousand meteorites is from the moon or Mars. The
remainder comes from the asteroid belt.

Meteorites have fallen pretty evenly over the world during the past 4.5
billion years. Most likely fell, and still fall, into the oceans.

In places such as Ohio, they've been pulverized by glaciers, weathered
away by the humid climate, and covered by soil and leaves.

Harvey's team meets in McMurdo Station in Antarctica, then heads out to
spend most of the time in the field, living in tents and scouting likely
spots for meteorites. Places where mountains or hills poke above the ice
sheet are usually good bets.

Meteorites flow toward the ocean and are buried in the moving ice sheet.
They accumulate in the nooks and crannies where the terrain pierces the
ice.

And if they are in spots where the ice evaporates as much as 4 inches a
day under the 24-hour summer sun, a process called sublimation, they pop
up like magic.

"It's a thrill to find one. This is a rock as old as the solar system,
and it's never been seen before," Harvey said.

The downside is the weather, which sometimes reduces a season of
searching into one good day. Storms killed much of the hunting season
last year, but among the 238 finds was a rare, golf-ball-size moon rock.

Only about 100 lunar meteorites have been found on Earth, and this was
only the second discovered in Antarctica. The find was less than a
half-mile from camp, which on a continent of ice, is virtually like
tripping over it.

Such discoveries give scientists a different perspective on the moon.
Most of the rocks that researchers look at were hauled back from the
lunar surface by Apollo astronauts, said Randy Korotev, a lunar
geologist from Washington University in St. Louis.

The Apollo moon rocks were from more unusual spots on the moon and were
found relatively close together.

Korotev, who has collected with Harvey, said he depends on the Case
Western researcher for a steady supply of meteorites. But the short
season and the difficulty of finding them in Antarctica's icy vastness
make it impossible for Harvey to meet the greater scientific demand.

So, Korotev checks Internet auction sites a couple of times each week
for meteorites. On any given day, there are hundreds of meteorites for
sale on eBay, ranging in price from a few dollars to thousands.

He said he has purchased about six meteorites from eBay as well as
others from dealers who advertise on the Internet.

"I get e-mail...offering to sell me meteorites. They show me nice
pictures. These guys also show up at gem and mineral shows with big
bushels of rocks."

Before they can be studied, meteorites have to be examined, classified
and cataloged.

That's important to a prospector who wants to sell to scientists because
it establishes the legitimacy of the find and increases its value.

In exchange for classification, dealers surrender a small portion of a
find to the institution conducting the survey so the rock can be thinly
sliced and doled out for research.

Trade exploded in the 1990s, when a rare meteorite discovered in
Australia fetched $40,000 a gram. Suddenly, prospectors began combing
spots in Australia, the American Southwest and the Sahara.

"I have no problem with the prospectors and the collectors. They're out
in the field doing the legwork. They're pounding the ground," said Dante
Luaretta, a planetary scientist at the University of Arizona.

"We find meteorites in Antarctica because of Ralph (Harvey) and his
efforts. But the big bonanza has been the Sahara. It's produced five
times more meteorites because people live there and are looking."

Retired Arizona plumber Marvin Kilgore spent 15 years in the Sahara
searching for meteorites.

"Some scientists felt they were the only ones who should be able to
touch the stuff," he said. "The older scientists had always got their
stuff for free or next to nothing."

Kilgore trained nomads to hunt and then bought their finds.

"When you take all the nomads in the Sahara, those guys cover a lot of
ground. They all have vehicles now because they have more money than
they ever had in their lives, from finding meteorites."

The result is the market is flooded with meteorites, which has driven
down prices.

Luaretta, however, said the best days of searching in the Sahara have
passed and that prices will climb again. Even mundane meteorites from
the asteroid belt soon will be in demand as the U.S. and China ramp up
the search for ways to mine asteroids for minerals, rocket fuel and
other material to aid space exploration.

In February, Luaretta formed a meteorite salvage center at Arizona to
purchase space rocks for research. He hired Kilgore to run it.

"At the rate we're picking them up, at least within this generation,
we'll have picked up all the meteorites that have fallen since the
beginning of time," Kilgore said.