The Stardust Mission returned samples from the coma of comet Wild-2, which probably came from the Kuiper Belt. Elemental analyses of the returned material should cast light on the physical conditions in which comets formed and aid in modeling data acquired remotely.

Wild-2 particles were captured in aerogel, where they left visible tracks.

Examination of the tracks shows that the particles disaggregated as they slowed. Members of the Stardust Preliminary Examination Team used x-ray microprobes to analyze several elements along a few ‘whole tracks.’ The elemental compositions resemble those of CI chondrites, but in general are enriched in volatile and moderately volatile elements.

Carbon and nitrogen have been observed remotely in Wild-2. Their concentrations and distributions in Wild-2 particles in are of interest for taxonomic reasons and as possible indicators of formation conditions.

An analytical reaction method based on nuclear reactions and developed at the Lab. Pierre Sue gives N and C atom concentrations for grains as small as 15 micrometers and should be applicable to Wild-2 particles. To illustrate, we show results for the carbonaceous meteorites Murchison, Tagish Lake and two cosmic spherules.