Surfaces and atmospheres of the outer planets, their satellites and ring systems

This special issue of PSS represents select articles based on research presented during the PS3.02 and PS3.03 sessions of the European Geosciences Union (EGU) meeting in Vienna, Austria, from 2 to 7 April 2006, and includes updates since the meeting. These EGU sessions focused on recent observations and models on the atmospheres and surfaces of the giant planets and their satellites, as well as their ring systems. Particular attention was given to results from the Cassini-Huygens mission to Saturn and Titan, which has been returning a wealth of new data over the past 3 years, and revealing an astonishingly complex and dynamic system. Complementary Earth-based observations were also obtained during the Saturn approach phase and the early in-orbit phase. A series of papers in this issue therefore discuss results from this mission on all of these aspects of the Saturnian system: the planet, its moons and the rings. In particular, there are several studies reported here from session PS3.02 on the Kronian icy satellites and the rings. Studies of Saturn’s moon, Enceladus, are reported here by Roatch et al. who present a new global mosaic of Enceladus, derived from Cassini and Voyager images. The spatial resolution is about 110m/ pixel for the regions imaged by Cassini and lower resolution for the north polar Voyager images. Altobelli et al. present an overview of the Composite Infrared Spectrometer (CIRS) ring thermal measurements obtained since Saturn orbit insertion in 2004. This thermal mapping of Saturn’s rings shows that the largest temperature changes on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation are a secondary effect. Leyrat et al. present an overview of the thermal behavior of Saturn’s rings and their dependencies with the phase angle and the local hour angle, using azimuthal scans obtained by the Cassini CIRS instrument to date. The ring temperatures vary with ring longi-