THE RADIAL DISTRIBUTION OF WATER ICE AND CHROMOPHORES ACROSS SATURNS SYSTEM

Over the past eight years, the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini orbiter has returned hyperspectral images in the 0.35-5.1 mum range of the icy satellites and rings of Saturn. These very different objects show significant variations in surface composition, roughness, and regolith grain size as a result of their evolutionary histories, endogenic processes, and interactions with exogenic particles. The distributions of surface water ice and chromophores, i.e., organic and non-icy materials, across the Saturnian system, are traced using specific spectral indicators (spectral slopes and absorption band depths) obtained from rings mosaics and disk-integrated satellites observations by VIMS. Moving from the inner C ring to Iapetus, we found a marking uniformity in the distribution of abundance of water ice. On the other hand, the distribution of chromophores is much more concentrated in the rings particles and on the outermost satellites (Rhea, Hyperion, and Iapetus). A reduction of red material is observed on the satellites surfaces orbiting within the E ring environment likely due to fine particles from Enceladus plumes. Once the exogenous dark material covering the Iapetus leading hemisphere is removed, the texture of the water ice-rich surfaces, inferred through the 2 mum band depth, appears remarkably uniform across the entire system.