[meteorite-list] NASA Finds New Type of Comet Dust Mineral (Brownleeite)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 12 Jun 2008 13:44:08 -0700 (PDT)
Message-ID: <200806122044.NAA07057_at_zagami.jpl.nasa.gov>

June 12, 2008

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

William P. Jeffs
Johnson Space Center, Houston
281-483-5111
william.p.jeffs at nasa.gov
RELEASE: 08-143

NASA FINDS NEW TYPE OF COMET DUST MINERAL

HOUSTON -- NASA researchers and scientists from the United States,
Germany and Japan have found a new mineral in material that likely
came from a comet.

The mineral, a manganese silicide named Brownleeite, was discovered
within an interplanetary dust particle, or IDP, that appears to have
originated from comet 26P/Grigg-Skjellerup. The comet originally was
discovered in 1902 and reappears every 5 years. The team that made
the discovery is headed by Keiko Nakamura-Messenger, a space
scientist at NASA's Johnson Space Center in Houston.

"When I saw this mineral for the first time, I immediately knew this
was something no one had seen before," said Nakamura-Messenger. "But
it took several more months to obtain conclusive data because these
mineral grains were only 1/10,000 of an inch in size."

A new method of collecting IDPs was suggested by Scott Messenger,
another Johnson space scientist. He predicted comet
26P/Grigg-Skjellerup was a source of dust grains that could be
captured in Earth's stratosphere at a specific time of the year.

In response to his prediction, NASA performed stratospheric dust
collections, using an ER-2 high-altitude aircraft flown from NASA's
Dryden Flight Research Center at Edwards Air Force Base, Calif. The
aircraft collected IDPs from this particular comet stream in April
2003. The new mineral was found in one of the particles. To determine
the mineral's origin and examine other dust materials, a powerful new
transmission electron microscope was installed in 2005 at Johnson.

"Because of their exceedingly tiny size, we had to use
state-of-the-art nano-analysis techniques in the microscope to
measure the chemical composition and crystal structure of Keiko's new
mineral," said Lindsay Keller, Johnson space scientist and a
co-discoverer of the new mineral. "This is a highly unusual material
that has not been predicted either to be a cometary component or to
have formed by condensation in the solar nebula."

Since 1982, NASA routinely has collected cosmic and interplanetary
dust with high-altitude research aircraft. However, the sources of
most dust particles have been difficult to pin down because of their
complex histories in space. The Earth accretes about 40,000 tons of
dust particles from space each year, originating mostly from
disintegrating comets and asteroid collisions. This dust is a subject
of intense interest because it is made of the original building
blocks of the solar system, planets, and our bodies.

The mineral was surrounded by multiple layers of other minerals that
also have been reported only in extraterrestrial rocks. There have
been 4,324 minerals identified by the International Mineralogical
Association, or IMA. This find adds one more mineral to that list.

The IMA-approved new mineral, Brownleeite, is named after Donald E.
Brownlee, professor of astronomy at the University of Washington,
Seattle. Brownlee founded the field of IDP research. The
understanding of the early solar system established from IDP studies
would not exist without his efforts. Brownlee also is the principal
investigator of NASA's Stardust mission.

The comet researchers include Messenger; John Jones, a co-discoverer
of the mineral from Johnson; Simon Clemett and Michael Zolensky in
Johnson's Astromaterials Research and Exploration Science
Directorate; Russ Palma, Minnesota State University at Mankato;
Robert Pepin, University of Minnesota, Minneapolis; Wolfgang Kl?ck,
R?ntgenanalytik Messtechnik GmbH, Germany; and Hirokazu Tatsuoka,
Shizuoka University, Japan.

For additional information on NASA programs, visit:

http://www.nasa.gov

        
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Received on Thu 12 Jun 2008 04:44:08 PM PDT