Probing the origin of the dark material on Iapetus

Among the icy satellites of Saturn, Iapetus shows a striking dichotomy between its leading and trailing hemispheres, the former being significantly darker than the latter. Thanks to the VIMS imaging spectrometer on-board Cassini, it is now possible to investigate the spectral features of the satellites in Saturn system within a wider spectral range and with an enhanced accuracy than with previously available data. Statistical techniques such as clustering methods are powerful tools for exploring the spectral data of planetary and satellite surfaces, since they allow to identify spectral units between the data of a single celestial body in correlation with the surface geology and to emphasise correlations among the spectra of different bodies. In this work, we present an application of the G-mode method to the high resolution, visible and near infrared data of Phoebe, Iapetus and Hyperion collected by Cassini/VIMS, in order to search for compositional correlations. We also present the results of a dynamical study on the efficiency of Iapetus in capturing putative dust grains travelling inward in Saturn system with the aim of evaluating the viability of Poynting-Robertson drag as the physical mechanism transferring the dark material to the satellite. The results of spectroscopic classification are used jointly with the ones of the dynamical study to describe a plausible physical scenario for the origin of Iapetus’ dichotomy.