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Transmission electron miscroscopy of in situ
presolar silicates in Alan Hills 77307.
Stroud R. M., Nguyen A. N., Alexander C. M. O'D, Nittler
L. R., and Stadermann F. J. (2008)
71st Meteoritical Society Meeting, Abstract #5201.
ABSTRACT
Presolar grains are dust grains that condensed in the
outflows from stars that predate the Sun. They exhibit
isotopic signatures that deviate so far from solar values
that they can only be explained as the results of
nucleosynthesis in stars. Silicates are the most abundant
unequivocally presolar grain phase, with concentrations
exceeding 100 ppm in some anhydrous interplanetary dust
particles and primitive meteorites, e.g., ALHA77307.
Previous coordinated secondary ion mass spectrometry (SIMS)
and scanning Auger electron spectroscopy studies of
ALHA77307 have identified over 100 individual presolar
silicate grains, with a wide range of compositions, e.g.,
Fe-rich, Ca-Al-rich, pure SiO2. In order to
better understand the structure and composition of the
silicate grains, and the rela-tionship to the surrounding
matrix material, we have begun focused ion beam-enabled in
situ transmission electron microscopy studies.
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