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M.S. Hanner (JPL/Caltech), J.P. Bradley (MVA, Inc.)
Infrared spectroscopy provides a direct link between laboratory measurements of interplanetary dust particles and astronomical observations of dust in space. Silicate minerals produce spectral features near 10 and 20 microns and the shape of these features is diagnostic of the mineral composition. Recent spectra of comet Hale-Bopp from the ground and from the ISO satellite allow mineralogical identification of the cometary silicates; both Mg-rich olivine and pyroxenes are present. The chondritic aggregate IDPs are the only type of meteoritic material resembling the composition of cometary dust at the submicron level. A component of these IDPs, the GEMS, consist primarily of glassy silicates bearing evidence of presolar (interstellar) origin. Infrared spectra of GEMS-rich material have now been measured, allowing direct comparison with the cometary spectra. In this paper, we compare the spectra and composition of GEMS with comets Hale-Bopp and Halley and discuss the probable interstellar origin of the GEMS and the cometary dust.