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Calibrating the abundance determinations of
presolar grains in Wild 2 cometary matter.
Stadermann F. J., Floss C., Gavinsky A., Kearsley A.
T., and Burchell M. J. (2009)
Lunar & Planet. Sci. 40, Abstract #1188.
ABSTRACT
Presolar dust grains which condensed in the environments of
evolved stars carry an isotopic memory of the nucleosynthetic
conditions at the time of their formation. Their anomalous isotopic
compositions make it possible to identify them today as ppm-level
inclusions in several types of primitive solar system materials. Such
presolar grains have been located in meteorites, interplanetary dust
particles, Antarctic micrometeorites, and in samples from comet Wild 2
collected by NASA's Stardust mission. The abundance of presolar grains
is a representation of the 'primitiveness' of its host material, with
the least altered material containing the highest density of such
grains. Although the residence of comet Wild 2 in the cold Kuiper belt
appears to represent an ideal environment for long-time preservation of
primitive components, laboratory searches so far have found only few
grains with clearly presolar isotopic signatures. The relatively low
abundance of such presolar grains in cometary samples could be
explained by extreme dilution with presolar-grain-free matter from the
hot inner solar system, but this opens many new questions about
mechanisms of transport and mixing in the solar nebula. A precise
determination of the presolar grain abundance in matter from Wild 2
therefore represents a key element in our understanding of cometary
history. Here we describe efforts to more accurately calibrate this
abundance with the help of hypervelocity laboratory shots of meteoritic
reference material.
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