[meteorite-list] Mars Meteorites Inspire Director of Meteorite Center

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 30 Jan 2007 08:58:26 -0800 (PST)
Message-ID: <200701301658.IAA11244_at_zagami.jpl.nasa.gov>

http://www.asu.edu/news/stories/200701/20070129_Wadhwa.htm

Space rocks Wadhwa's world at meteorite center
Arizona State Universiry
January 29, 2007

It was a piece of Mars that set ASU geology professor Meenakshi "Mini"
Wadhwa on a career investigating meteorites. At the time, Wadhwa, who
directs the Center for Meteorite Studies in the School of Earth and
Space Exploration, was a graduate student at Washington University in
St. Louis and newly arrived from India.

"I had come from a terrestrial geology background, and I wanted to study
other planets," she says. "I knew about the lunar material from the
Apollo program, but not about any other extraterrestrial rocks."

Then one of her professors told her about the meteorites from Mars.

Incredulous at first that pieces of Mars were here on Earth, Wadhwa
knew immediately what direction her career would go. It soon
broadened to include all kinds of meteorites.

"Meteorites are rocky pieces from the first solid bodies to form when
our solar system was born," she says.

They include the oldest rocks known, which have an age of more than 4.5
billion years. This age is greater than the oldest rocks native to
Earth, and it defines the age of the solar system.

"One of my research programs is to resolve in detail the timeline for
the formation of these bodies," Wadhwa says.

Meteorites arrive on Earth through a haphazard process that begins in a
collision between rocky bodies in space called asteroids. These range in
size from perhaps a dozen yards across up to hundreds of miles in
diameter. As rocky fragments fly after the collision, some escape the
gravity of the parent object and sail off into space.

After drifting around the sun for perhaps millions of years, a rock
fragment may collide with Earth. If the fragment is larger than an inch
or so across - and if it escapes falling into the ocean - it will land
on the ground. (Space rocks smaller than an inch mostly burn up as they
pass through the atmosphere.) With luck, someone may find the meteorite
and let scientists examine it.

Because a meteorite doesn't arrive with a return-address label,
scientists first determine what kind of space rock it is. From that,
they draw a preliminary conclusion about its birthplace.

Most meteorites are primitive, rocky objects that formed in the same
cloud of gas and dust from which the sun and planets formed. Other
meteorites are made of mostly nickel-iron: These include the famous
Ca?on Diablo meteorite that blasted Meteor Crater in northern Arizona
some 49,000 years ago.

But scientists found other meteorites that didn't fit into existing
categories. One of these oddball space rocks landed in the village of
Chassigny, France, in 1815. Another fell on Shergotty, India, in 1865,
and a third landed at Nakhla, Egypt, in 1911. Taken together, these
meteorites somewhat resembled each other, and scientists took to calling
them the SNC meteorites, for Shergotty-Nakhla-Chassigny. The SNCs (or
"snicks" for short) are now known to be fragments of the planet Mars.

"If you just look at a Mars meteorite, you'd be hard-pressed to tell it
from an ordinary Earth rock," Wadhwa says.

Scientists finally identified these as coming from Mars by noting that
they contain trapped gases. As she explains, these "have a composition
matching the Martian atmosphere, as detected by the Viking landers in
the mid-1970s. That cinched a Martian origin."

Likewise, careful analysis showed that other oddball meteorites were
pieces of the moon. They were chemically similar to rock samples brought
back from the moon by Apollo astronauts. To date, about 40 lunar
meteorites and 36 Martian ones are known.

Housed at the Center for Meteorite Studies, ASU's meteorite collection
numbers more than 1,500 - including several Mars meteorites and two from
the moon. It's the largest meteorite collection at any university in the
world.

"We have such an incredible resource to work with," says Wadhwa, adding
that it was part of what drew her to ASU from the Field Museum in
Chicago, where she was the curator of meteorites.

"For me, as an analytical geochemist, there are wonderful facilities
here," she says.

Adding to the facilities will be a new, state-of-the-art mass
spectrometer, one of the tools for studying chemical elements within
meteorites.

Besides meteorites, Wadhwa's research involves developing new methods
for investigating tiny amounts of extraterrestrial materials, such as
those returned by the recent spacecraft missions Genesis and Stardust.
Wadhwa received the prestigious Guggenheim Fellowship in 2005 in support
of her work on the solar wind sample returned by NASA's Genesis
spacecraft. She also is a science team member of OSIRIS, a sample-return
mission to an asteroid; it is one of three Discovery-class missions NASA
is considering.

Robert Burnham, robert.burnham at asu.edu
(480) 458-8207
Received on Tue 30 Jan 2007 11:58:26 AM PST