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 <[email protected]> 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." > ______________________________________________ > 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
