Cassini Imaging Science: initial results on Saturn's rings and small satellites.

Images acquired of Saturn's rings and small moons by the Cassini Imaging Science Subsystem (ISS) during the first 9 months of Cassini operations at Saturn have produced many new findings. These include new saturnian moons; refined orbits of new and previously known moons; narrow diffuse rings in the F-ring region and embedded in gaps within the main rings; exceptionally fine-scale ring structure in moderate- to high-optical depth regions; new estimates for the masses of ring-region moons, as well as ring particle properties in the Cassini division, derived from the analysis of linear density waves; ring particle albedos in select ring regions; and never-before-seen phenomena within the rings.

Cassini Imaging Science: initial results on Phoebe and Iapetus.

The Cassini Imaging Science Subsystem acquired high-resolution imaging data on the outer Saturnian moon, Phoebe, during Cassini's close flyby on 11 June 2004 and on Iapetus during a flyby on 31 December 2004. Phoebe has a heavily cratered and ancient surface, shows evidence of ice near the surface, has distinct layering of different materials, and has a mean density that is indicative of an ice-rock mixture. Iapetus's dark leading side (Cassini Regio) is ancient, heavily cratered terrain bisected by an equatorial ridge system that reaches 20 kilometers relief. Local albedo variations within and bordering Cassini Regio suggest mass wasting of ballistically deposited material, the origin of which remains unknown.

Cassini Imaging Science: initial results on Saturn's atmosphere.

The Cassini Imaging Science Subsystem (ISS) began observing Saturn in early February 2004. From analysis of cloud motions through early October 2004, we report vertical wind shear in Saturn's equatorial jet and a maximum wind speed of approximately 375 meters per second, a value that differs from both Hubble Space Telescope and Voyager values. We also report a particularly active narrow southern mid-latitude region in which dark ovals are observed both to merge with each other and to arise from the eruptions of large, bright storms. Bright storm eruptions are correlated with Saturn's electrostatic discharges, which are thought to originate from lightning.