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[47.04] Emissivity spectra of mixtures of ices, silicates and organics: understanding the thermal infrared spectra of Saturn'a ice moons.

J. M. Carvano (LESIA - Observatoire de Paris), A. Migliorini (LESIA - Observatoire de Paris/ Department of Astronomy, University of Padova), M. A. Barucci (LESIA - Observatoire de Paris)

The thermal infrared spectra of several icy satellites seem to have in common the absence of emissivity features. This was the case of Ganymede and Calisto, observed by the Galileo spacecraft also for Phoebe and Iapetus, recently observed by Cassini/CIRS. However, several materials that have been identified in the surface of these bodies present emissivity features in the observed ranges. In particular, water and CO₂ices, which have been detected in the surface of Phoebe by Cassini/VIMS have features in the thermal infrared with sufficient contrast to have been detect by CIRS. Here we study the physical cause of the absence of features by simulating the efects of intimate mixtures using models of directional emissivity for optically thick and optically thin surfaces for different particle sizes and abundances. The simulations include a set of materials detected in the surface of Phoebe, like CO₂ ice, water ice, hydrated silicates and organics.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.