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Correlated high spatial resolution elemental and
isotopic characterization of Wild 2 cometary
samples.
Stadermann F. J., Floss C., and Bose M. (2007)
Lunar Planet. Sci. XXXVIII, Abstract #1334.
ABSTRACT
NASA's Stardust mission was successfully completed with
the return of the first bona fide cometary samples
for laboratory studies, and the preliminary examination
yielded some unexpected results about the composition and
origin of cometary matter. From an isotopic point of view,
the most important findings were (a) the fact that the
majority of the samples are isotopically normal, (b) the
observation of CAI-like (Ca-Al-rich inclusions) material
with a 16O-enriched composition similar to what
has been seen in meteorites, (c) the detection of D and N
anomalies indicative of an interstellar heritage of some
organics, and (d) the discovery of one - but only one -
incontrovertible circumstellar grain.
While isotopic data alone can provide important clues
about a given sample, essential insight can frequently only
be gained by combining isotopic information with spatially
correlated elemental and mineralogical data. Such a
complementary analytical approach is especially mandatory in
cases of rare or valuable samples such as the cometary
matter from Wild 2. For samples that are heterogeneous on a
submicrometer scale, the NanoSIMS is the optimal tool for a
detailed isotopic characterization. Transmission electron
microscopy (TEM) is the technique of choice for detailed
mineralogical information and as such provides an ideal
complement to the NanoSIMS. Many types of samples, however,
are not electrontransparent and thus not immediately
accessible for TEM measurements. In such cases, however, it
is still possible to use Auger spectroscopy for elemental
imaging on a spatial scale of tens of nanometers, well below
the working range of EDX characterization. Here we describe
the application of complementary high resolution isotopic
and elemental imaging for the analysis of cometary
samples.
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