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The distribution of presolar grains in CI and CO
meteorites
Marhas K. K., Hoppe P., Stadermann F. J., Floss C.,
and Lea A. S. (2006) Lunar Planet. Sci. XXXVII,
Abstract #1959.
ABSTRACT
Presolar grains have been identified by huge isotopic
anomalies in the chemical residues from primitive
meteorites. Recently, presolar silicates, which can not be
separated by conventional chemical procedures, have been
identified in-situ in polished thin sections. To date, more
than 100 presolar silicates have been reported from various
type 3.0 unaltered primitive meteorites, with a maximum
abundance reported for Acfer 094 of 180 ppm. In addition to
the information inferred from astronomical observations, the
abundance as well as mineralogy and chemical composition of
presolar grains from different meteorite classes can help to
understand (1) the different processes effecting the growth
of these grains in circumstellar environments, (2) the
variations/alterations taking place within different
peterological types of meteorites, and (3) the destruction
of grains in the ISM. A larger data set on presolar
silicates from various meteorite classes is needed to obtain
information on all of these aspects. Previous work on the
Tagish Lake meteorite indicated an abundance of 4 ppm for
presolar silicates (matrix area covered ~ 29250
µm2) and also a probable carbonaceous
presolar grain within the matrix area of 5400
µm2. Here, we report on the continued
in-situ search for various types of presolar grains
(oxides/silicates/nitrides/carbides) in the Tagish Lake
meteorite and on new results of an in-situ search for
presolar silicates and oxides in Yamato 81025.
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