The Shape of Saturn's Huygens Ringlet Viewed by Cassini ISS

TL;DR

This study models Saturn's Huygens Ringlet shape using Cassini data over 8 years, revealing complex structures, embedded bodies, and resonances, with implications for ring dynamics and morphology.

Contribution

Develops a new model treating each edge of the ringlet separately, incorporating observed modes and irregular structures, advancing understanding of ringlet dynamics.

Findings

Detection of m=2 modes forced by Mimas resonance

Identification of long-lived irregular structures

Locations of embedded massive bodies inferred from wake structures

Abstract

A new model for the shape of the prominent eccentric ringlet in the gap exterior to Saturn's B-ring is developed based on Cassini imaging observations taken over about 8 years. Unlike previous treatments, the new model treats each edge of the ringlet separately. The Keplerian component of the model is consistent with results derived from Voyager observations, and $m=2$ modes forced by the nearby Mimas 2:1 Lindblad resonance are seen. Additionally, a free $m=2$ mode is seen on the outer edge of the ringlet. Significant irregular structure that cannot be described using normal-mode analysis is seen on the ringlet edges as well. Particularly on the inner edge, that structure remains coherent over multi-year intervals, moving at the local Keplerian rate. We interpret the irregular structure as the signature of embedded massive bodies. The long coherence time suggests the responsible bodies are concentrated near the edge of the ringlet. Long wake-like structures originate from two locations on the inner edge of the ringlet, revealing the locations of the two most massive embedded bodies in that region. As with the Voyager observations, the Cassini data sets showed no correlation between the width and the radius of the ringlet as would be expected for a self-gravitating configuration, except for a brief interval during late 2006, when the width-radius relation was similar to those seen in most other narrow eccentric ringlets in the Solar System.