Hey all,
Does anyone know if there are any Oxygen Isotope results available? Where do
these plot?
Cheers,
Jeff
----- Original Message -----
From: "Mike Groetz" <[email protected]>
To: "Meteorite List" <[email protected]>
Sent: Sunday, January 11, 2009 1:13 AM
Subject: [meteorite-list] Scientists Publish 1st Ever Evidence of
Asteroidswith Earth-like Crust
http://media-newswire.com/release_1083611.html
(Media-Newswire.com) - COLLEGE PARK, Md. - Two rare meteorites found in
Antarctica two years ago are from a previously unknown, ancient asteroid
with an outer layer or crust similar in composition to the crust of
Earth's continents, reports a research team primarily composed of
geochemists from the University of Maryland.
Published in the January 8 issue of the journal Nature, this is the first
ever finding of material from an asteroid with a crust like Earth's. The
discovery also represents the oldest example of rock with this composition
ever found.
These meteorites point "to previously unrecognized diversity" of materials
formed early in the history of the Solar System, write authors James Day,
Richard Ash, Jeremy Bellucci, William McDonough and Richard Walker of the
University of Maryland; Yang Liu and Lawrence Taylor of the University of
Tennessee and Douglas Rumble III of the Carnegie Institution for Science.
James Day looking at a portion of the meteorite in the University of
Maryland's isotope geochemistry lab. In the background is a mass
spectrometer used to analyze the meteorite samples. Prof. James Day
looking at a portion of the meteorite in the University of Maryland's
isotope geochemistry lab. In the background is a mass spectrometer used to
analyze the meteorite samples.
"What is most unusual about these rocks is that they have compositions
similar to Earth's andesite continental crust -- what the rock beneath our
feet is made of," said first author Day, who is a research scientist in
Maryland's department of geology. "No meteorites like this have ever been
seen before."
Day explained that his team focused their investigations on how such
different Solar System bodies could have crusts with such similar
compositions. "We show that this occurred because of limited melting of
the asteroid, and thus illustrate that the formation of andesite crust has
occurred in our solar system by processes other than plate tectonics,
which is the generally accepted process that created the crust of Earth."
The two meteorites (numbered GRA 06128 and GRA 06129) were discovered in
the Graves Nunatak Icefield during the US Antarctic Search for Meteorites
(ANSMET) 2006/2007 field season. Day and his colleagues immediately
recognized that these meteorites were unusual because of elevated contents
of a light-colored feldspar mineral called oligoclase. "Our age results
point to these rocks being over 4.52 billion years old and that they
formed during the birth of the Solar System. Combined with the oxygen
isotope data, this age points to their origin from an asteroid rather than
a planet," he said.
There are a number of asteroids in the asteroid belt that may have
properties like the GRA 06128 and GRA 06129 meteorites including the
asteroid (2867) Steins, which was studied by the European Space Agency's
Rosetta spacecraft during a flyby this past September. These so-called
E-type asteroids reflect the Sun's light very brightly, as would be
predicted for a body with a crust made of feldspar.
According to Day and his colleagues, finding pieces of meteorites with
andesite compositions is important because they not only point to a
previously unrecognized diversity of Solar System materials, but also to a
new mechanism to generate andesite crust. On the present-day Earth, this
occurs dominantly through plates colliding and subduction - where one
plate slides beneath another. Subduction forces water back into the mantle
aiding melting and generating arc volcanoes, such as the Pacific Rim of
Fire - in this way new crust is formed.
"Our studies of the GRA meteorites suggest similar crust compositions may
be formed via melting of materials in planets that are initially volatile-
and possibly water-rich, like the Earth probably was when if first formed"
said Day." A major uncertainty is how evolved crust formed in the early
Solar System and these meteorites are a piece in the puzzle to
understanding these processes."
This research was funded by the NASA cosmochemistry program.
______________________________________________
http://www.meteoritecentral.com
Meteorite-list mailing list
[email protected]
http://six.pairlist.net/mailman/listinfo/meteorite-list
______________________________________________
http://www.meteoritecentral.com
Meteorite-list mailing list
[email protected]
http://six.pairlist.net/mailman/listinfo/meteorite-list
