Abstract

We have utilized the IRS imaging spectrometer on board the Spitzer Space Telescope (SST) to obtain observations of comet 9P/Tempel 1 during the Deep Impact encounter. Detailed, highly structured 5 - 35 μm spectra of the ejecta were obtained, which represent the best measurement to date of the sub-surface solid material of a comet. Emission signatures due to silicates, carbonates, phyllosilicates, water ice, amorphous carbon, and sulfides were found. The atomic abundance of the observed material was consistent with solar system abundances. The material that was ejected by the impact was pristine and unaltered, except for the de-aggregation of loosely held dust grains into submicron building blocks. The presence of a large amount of unaltered crystalline silicates, phyllosilicates, and carbonates in the comet's interior has fundamental implications for the nature of the material incorporated into the comet 4.5 Byrs ago. Comparison of the our results to the cometary material returned by the STARDUST spacecraft may provide a fundamental cross-check for the spectral decomposition models presented here.