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

[Ron Baalke]

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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