How the Enceladus Dust Jets Form Saturn's E Ring
Abstract
Pre--Cassini models of Saturn's E ring failed to reproduce its peculiar vertical structure inferred from earth-bound observations. After the discovery of an active ice- volcanism of Saturn's icy moon Enceladus the relevance of the directed injection of particles for the vertical ring structure of the E ring was swiftly recognised. However, simple models for the delivery of particles from the plume to the ring predict a too small vertical ring thickness and overestimate the amount of the injected dust. Here we report on numerical simulations of grains leaving the plume and populating the dust torus of Enceladus. We run a large number of dynamical simulations including gravity and Lorentz force to investigate the earliest phase of the ring particle life span. The evolution of the electrostatic charge carried by the initially uncharged grains is treated selfconsistently. Freshly ejected plume particles are moving in almost circular orbits because the Enceladus orbital speed exceeds the particles' ejection speeds by far. Only a small fraction of grains that leave the Hill sphere of Enceladus survive the next encounter with the moon. The flux and the size distribution of the surviving grains, replenishing the ring particle reservoir, differs significantly from the flux and the size distribution of the ejected plume particles. Our numerical simulations reproduce the vertical ring profile measured by the Cassini dust instrument CDA. From our simulations we calculate the deposition rates of plume particles hitting Enceladus' surface. We find that at a distance of 100 m from a jet a 10 m sized ice boulder should be covered by plume particles in 105 to 106 years.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSM.P32A..05K
- Keywords:
-
- 5420 Impact phenomena;
- cratering (6022;
- 8136);
- 5421 Interactions with particles and fields;
- 5465 Rings and dust;
- 5470 Surface materials and properties