|
Transmission electron microscopy 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)
Meteorit. Planet. Sci. 43 (7, Suppl.), A148.
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.
|