Of Horseshoes and Heliotropes: Dynamics of Dust in the Encke Gap

Abstract

The Encke Gap is a 320-km-wide opening in Saturn's outer A ring that contains the orbit of the small moon Pan and an array of dusty features composed of particles less than 100 microns across. In particular, there are three narrow ringlets in this region that are not longitudinally homogeneous, but instead contain series of bright clumps. Using images obtained by the Cassini spacecraft, we track the motions of these clumps and demonstrate that they do not follow the predicted trajectories of isolated ring particles moving under the influence of Saturn's and Pan's gravitational fields. We also examine the orbital properties of these ringlets by comparing images taken at different longitudes and times. We find evidence that the orbits of these particles have forced eccentricities induced by solar radiation pressure. In addition, the mean radial positions of the particles in these ringlets appear to vary with local co-rotating longitude, perhaps due to the combined action of drag forces, gravitational perturbations from Pan, and collisions among the ring particles. The dynamics of the dust within this gap therefore appears to be much more complex than previously appreciated.

59 pages, 23 figures, accepted for publication in Icarus. Revised to include small wording changes made in proofs, and fix a small typo in the final figure

References in corpus (2)

• The shape and dynamics of a heliotropic dusty ringlet in the Cassini Division
• Modeling the Seasonal Variability of the Plasma Environment in Saturn's Magnetosphere between Main Rings and Mimas

Cited by in corpus (14)

• Particle Concentration At Planet Induced Gap Edges and Vortices: I. Inviscid 3-D Hydro Disks
• Planetary Rings
• Non-circular features in Saturn's D ring: D68
• A new pattern in Saturn's D ring created in late 2011
• Seasonal structures in Saturn's dusty Roche Division correspond to periodicities of the planet's magnetosphere
• Bright clumps in the D68 ringlet near the end of the Cassini Mission
• Analysing the region of the rings and small satellites of Neptune
• Accretion of Ornamental Equatorial Ridges on Pan, Atlas and Daphnis
• On the tidal environment of an outwardly migrated F-ring
• Evidence that a novel type of satellite wake might exist in Saturn's E ring
• A curious ringlet that shares Prometheus' orbit but precesses like the F ring
• Particle dynamics in the central ringlet of Saturn's Encke gap
• Dust in the arcs of Methone and Anthe
• Changes in a Dusty Ringlet in the Cassini Division after 2010