Science Seminars

9/29/2011 – Dynamical Surprises in Saturn’s Rings

Speaker: Glen Stewart, LASP
Date: Thursday, Sep 29, 2011
Time: 4pm
Location: Duane

Seminar Abstract:

Imagine what it would be like to observe a “protoplanetary” disk at a resolution of one kilometer over a time span of a 1000 orbits. The Cassini spacecraft has been observing the Saturn system at close range for the past 7 years. During this time, Saturn’s rings have been found to be more complex and time-variable than had been surmised after the Voyager flyby missions 30 years ago. Some highlights of the Cassini observations and their dynamical interpretation will be described. In particular, the rings appear to be marginally gravitational stable, so that the rings break up into high and low density regions and are therefore inhomogeneous on nearly all scales. The effective viscosity of the rings is dominated by gravitational interactions between elongated clumps of particles and exhibits a non-Newtonian rheology. Narrow ringlets perturbed by nearby moons are subject to negative diffusion where particle collisions act to decrease the width of the ring. The total mass of the rings is still poorly constrained, but will be directly measured by the Cassini spacecraft at the end of its mission.