Stardust in Comets

Comet nuclei most likely contain both solar nebula condensates and intact pre-solar grains that survived in the outer solar nebula. Based on infrared spectroscopy, in situ sampling, and analysis of interplanetary dust particles (IDPs), cometary dust is an unequilibrated mixture of crystalline and glassy silicates, organic refractory material, iron sulfide, and other minor components. Isotopic anomalies in deuterium, nitrogen, and oxygen indicate that at least some of the organic refractory material and a fraction of the silicate grains are of pre-solar origin. 5 to 45 micron spectra of comet Hale-Bopp displayed strong emission peaks of crystalline forsterite. Spectral features of glassy olivine and pyroxene and crystalline enstatite were present as well. Spitzer will extend such spectroscopy to many other, fainter comets. NASA's Stardust mission encountered comet 81P/Wild 2 on 2 January 2004 and collected a sample of freshly released dust for return to Earth on 15 January 2006. These particles will be analyzed to determine isotopic, elemental, and mineralogic composition. In this talk, dust composition and origins will be discussed and the Stardust mission will be described.