Science Seminars

11/18/2010 – Saturn’s rings under a microscope: Cassini UVIS results

Speaker: Miodrag Sremcevic
Date: Thursday, Nov 18, 2010
Time: 4:00pm
Location: Duane D-142

Seminar Abstract:

After 6 years of Cassini mission the Ultraviolet Imaging Spectrograph (UVIS) instrument recorded more than hundred stellar occultations by Saturn’s rings. Most of the observed occultations have excellent resolution on the order of ten meters or even better. In this talk we give overview of UVIS results on the rings small scale structure. The high resolution and multitude of observations allows us to infer the orientation and two-dimensional picture of the underlying ring structure. Saturnian main rings are anything but bland and homogeneous at meters scale. Most of the A ring and outer B ring show 10-50m structures pitched by about 20 degrees from the orbital motion. These observations are consistent with Toomre type self-gravity wakes, and allow us to directly infer their spatial scalings. The inner A ring and lower optical depth regions in the B ring show 100-200m scale regular waves. These waves have no pitch angle and are consistent with a viscous oscillatory instability, better known as overstability. The most surprising aspect of these waves is their patchy appearance throughout the rings. In higher optical depth regions of the B ring the most dominant structure is irregular with spatial scales of about 100m. The B ring results are the most puzzling, as one explanation hints at surprisingly low total mass of the B ring.