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In the last two years our work
with the NanoSIMS has been very successful. The
downtime due to hardware problems went down
dramatically and with the help of our own
development efforts, we are now able to use the
instrument for a large variety of scientific
studies. Several significant discoveries in the
study of presolar grains and IDPs have been made
with the NanoSIMS in the short time this instrument
has been available. This has resulted in numerous
publications from our group, including four that
were published in the journal Science (DAULTON et
al., 2002; FLOSS et al., 2004; MESSENGER et al.,
2003a; NGUYEN and ZINNER, 2004a).
Interplanetary dust particles
(IDPs) are primitive samples of extraterrestrial
material with a fine-grained heterogeneous matrix.
We have used the NanoSIMS for extensive studies of
the C, N, O, Mg/Al, Si, and S isotopic compositions
of these particles on a sub-micrometer scale (FLOSS
and STADERMANN, 2003; 2004; FLOSS et al., 2004;
MESSENGER and KELLER, 2002; MESSENGER et al.,
2003a; 2003b; STADERMANN and BRADLEY, 2003). This
work led to the discovery of presolar silicates
(MESSENGER et al., 2003a) and the first observation
of C isotopic anomalies in these particles (FLOSS
et al., 2004). Most recent results include the
discovery of presolar corundum in IDPs (in
preparation) and of presolar phases in Antarctic
micrometeorites (in preparation).
Combined mineralogical and
isotopic studies of presolar grains on TEM grids
were used for the determination of SiC polytype
distributions (DAULTON et al., 2002; 2003) and for
the detailed characterization of high-density
(CROAT et al., 2004; STADERMANN et al., 2004a) and
low-density (CROAT et al., 2003a; 2003b; STADERMANN
et al., 2002; 2003; 2004b) presolar graphite
spherules and their sub-components. The latter
project included O and Ti isotopic measurements of
100 nm sized 'presolar grains within presolar
grains'.
Other lines of investigation
looked at the O isotopic compositions of presolar
spinel grains (ZINNER et al., 2002a; 2003b; 2004),
as well as the C, N, and Si isotopic compositions
of small SiC and Si3N4 particles (ZINNER et al.,
2002b; 2003a). We used the multi-collection and
combined mode capabilities of the NanoSIMS for C,
N, O, Mg/Al, Si, K, Ca, and Ti isotopic studies of
individual presolar graphites (AMARI et al., 2002;
2003a; 2004) and for C, Si, and Ti isotopic
measurements in presolar SiC grains of type X and Z
(AMARI et al., 2003b).
High-resolution NanoSIMS O
isotopic imaging of >70,000 densely packed oxide
grains was used to identify several hundred
presolar spinel and corundum grains (NGUYEN et al.,
2003a; 2003b; 2003c). A similar imaging study of
grain size separates from Acfer 094 led to the
discovery of presolar silicate stardust in
meteorites (NGUYEN and ZINNER, 2004a;
2004b).
Some development work using the
St. Louis NanoSIMS has been done in collaboration
with CAMECA to quantify the aging characteristics
of the new miniaturized electron multipliers
(SLODZIAN et al., 2003) and to evaluate the 'QSA'
effect (SLODZIAN et al., 2004). NanoSIMS imaging
was used for test measurements of elemental
distributions in aerosol particles (EBERT et al.,
2004).
References for
this section
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