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J. M. Sunshine (SAIC), M. F. A'Hearn (Univ. of Maryland), P. H. Schultz (Brown University), O. Groussin, L. Feaga (Univ. of Maryland), Deep Impact Science Team
On July 4, 2005 NASA's Deep Impact mission successfully carried out an impact experiment with the comet 9P/Tempel 1. We report here on the compositional results of the ejecta mechanically excavated from the interior of the comet. Spectra from the on-board infrared spectrometer (1.05 to 4.8 microns; R~200-900) include strong water ice absorptions in data collected from 1 second to 45 minutes after the impact. Based on surface temperatures mapped prior to impact and a lack of absorption features, water ice is not present on the surface of the comet. Thus, the ice component in the ejecta represents a large source of the overall volatile increase observed post-impact. With maximum spatial resolution of 85 m/pixel and temporal resolution as high as 0.7 seconds, we compare the spectral data with visible imagery to understand the distribution of ice with respect to cratering physics to constrain the depth of origin and extent of the ice component. We note that ice absorptions are detectable 45 minutes after impact consistent with microscopic ice particles whose lifetime is on the order of hours. These results are compared to changes in water emission to trace the sublimation path of the ice grains and better understand the relatioship between coma constituents and comet interiors.
This work was funded by NASA through the Deep Impact project.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.