[meteorite-list] Dust in the wind

From: ensoramanda at ntlworld.com <ensoramanda_at_meteoritecentral.com>
Date: Tue, 3 Nov 2009 1:50:39 +0000
Message-ID: <20091103015039.TFI2T.251273.root_at_web01-winn.ispmail.private.ntl.com>

Hi Darren, All,

and here is where the detail is...sorry about the long link...never have figured out how to make those short links!!

http://docs.google.com/gview?a=v&q=cache:UCwD2iKBCesJ:www.dtm.ciw.edu/users/nittler/preprints/Busemann2009EPSL.pdf+*Busemann,+H.,+et+al.,+Ultra-primitive+interplanetary+dust+particles+from+the+comet+26P/Grigg%E2%80%93Skjellerup+dust+stream+collection,+Earth+Planet.+Sci.+Lett.+(2009),+doi:10.1016/j.epsl.2009.09.007&hl=en&gl=uk&pid=bl&srcid=ADGEESgM5kH7cXN7mr3Fi2-a0t_e6k4x_4CtwCzFw95JP96axFpuafqTzeMji9qnO9121azGdv-IPp2M6dxaXlZunUbm8f0oftwb1g_skGOPr2omUnnPrkic7ewhIXjgbfCizPQUpWxH&sig=AFQjCNEIVrqaqzoT7PnhncC1OXm4Y_o3fQ

Graham, UK


---- Darren Garrison <cynapse at charter.net> wrote:
> http://www.eurekalert.org/pub_releases/2009-11/ci-pf110209.php
>
> 'Ultra-primitive' particles found in comet dust
>
> Washington, D.C.?Dust samples collected by high-flying aircraft in the upper
> atmosphere have yielded an unexpectedly rich trove of relicts from the ancient
> cosmos, report scientists from the Carnegie Institution. The stratospheric dust
> includes minute grains that likely formed inside stars that lived and died long
> before the birth of our sun, as well as material from molecular clouds in
> interstellar space. This "ultra-primitive" material likely wafted into the
> atmosphere after the Earth passed through the trail of an Earth-crossing comet
> in 2003, giving scientists a rare opportunity to study cometary dust in the
> laboratory.
>
> At high altitudes, most dust in the atmosphere comes from space, rather than the
> Earth's surface. Thousands of tons of interplanetary dust particles (IDPs) enter
> the atmosphere each year. "We've known that many IDPs come from comets, but
> we've never been able to definitively tie a single IDP to a particular comet,"
> says study coauthor Larry Nittler, of Carnegie's Department of Terrestrial
> Magnetism. "The only known cometary samples we've studied in the laboratory are
> those that were returned from comet 81P/Wild 2 by the Stardust mission." The
> Stardust mission used a NASA-launched spacecraft to collect samples of comet
> dust, returning to Earth in 2006.
>
> Comets are thought to be repositories of primitive, unaltered matter left over
> from the formation of the solar system. Material held for eons in cometary ice
> has largely escaped the heating and chemical processing that has affected other
> bodies, such as the planets. However, the Wild 2 dust returned by the Stardust
> mission included more altered material than expected, indicating that not all
> cometary material is highly primitive.
>
> The IDPs used in the current study were collected by NASA aircraft in April
> 2003, after the Earth passed through the dust trail of comet Gregg-Skjellerup.
> The research team, which included Carnegie scientists Nittler, Henner Busemann
> (now at the University of Manchester, U.K.), Ann Nguyen, George Cody, and seven
> other colleagues, analyzed a sub-sample of the dust to determine the chemical,
> isotopic and microstructural composition of its grains. The results are reported
> on-line in Earth and Planetary Science Letters.*
>
> "What we found is that they are very different from typical IDPs" says Nittler.
> "They are more primitive, with higher abundances of material whose origin
> predates the formation of the solar system." The distinctiveness of the
> particles, plus the timing of their collection after the Earth's passing through
> the comet trail, point to their source being the Gregg-Skjellerup comet.
>
> "This is exciting because it allows us to compare on a microscopic scale in the
> laboratory dust particles from different comets," says Nittler. "We can use them
> as tracers for different processes that occurred in the solar system
> four-and-a-half billion years ago."
>
> The biggest surprise for the researchers was the abundance of so-called presolar
> grains in the dust sample. Presolar grains are tiny dust particles that formed
> in previous generations of stars and in supernova explosions before the
> formation of the solar system. Afterwards, they were trapped in our solar system
> as it was forming and are found today in meteorites and in IDPs. Presolar grains
> are identified by having extremely unusual isotopic compositions compared to
> anything else in the solar system. But presolar grains are generally extremely
> rare, with abundances of just a few parts per million in even the most primitive
> meteorites, and a few hundred parts per million in IDPs. "In the IDPs associated
> with comet Gregg-Skjellerup they are up to the percent level," says Nittler.
> "This is tens of times higher abundances than we see in other primitive
> materials."
>
> Also surprising is the comparison with the samples from Wild 2 collected by the
> Stardust mission. "Our samples seem to be much more primitive, much less
> processed, than the samples from Wild 2," says Nittler, "which might indicate
> that there is a huge diversity in the degree of processing of materials in
> different comets."
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Received on Mon 02 Nov 2009 08:50:39 PM PST