Dear Jeff and list, Jeff, a third try. Oxygen isotopic analysis: Z. Sharp, University of New Mexico
Oxygen isotopic analyses of three small (2-5 mg) pieces of GRA 06129 yielded the following results which fall in the Earth, Moon and enstatite meteorite field: δ17O = 3.04, δ18O = 6.01, Δ18O = -0.09 δ17O = 2.89, δ18O = 5.63, Δ18O = -0.03 δ17O = 3.05, δ18O = 6.01, Δ18O = -0.07 [where Δ18O = δ17O - 0.52 x δ18O] Dirk...Tokyo --- On Sat, 1/10/09, Jeff Kuyken <[email protected]> wrote: > From: Jeff Kuyken <[email protected]> > Subject: Re: [meteorite-list] Scientists Publish 1st Ever Evidence of > Asteroidswith Earth-like Crust > To: [email protected], "Meteorite List" <[email protected]> > Date: Saturday, January 10, 2009, 11:32 PM > 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 ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
