Particles co-orbital to Janus and Epimetheus: a firefly planetary ring

TL;DR

This paper reports the discovery and analysis of a unique, transient co-orbital ring with firefly-like visibility around Saturn's moons Janus and Epimetheus, explaining its formation, behavior, and short particle lifetime.

Contribution

It introduces a new co-orbital planetary ring, details its variable visibility, and models its rapid particle replenishment through micrometeorite impacts.

Findings

Ring width is 30-50% larger than previously thought.

Ring particles have a lifetime of less than two decades.

Replenishment model explains the ring's existence and firefly behavior.

Abstract

The Cassini spacecraft found a new and unique ring that shares the trajectory of Janus and Epimetheus, co-orbital satellites of Saturn. Performing image analysis, we found this to be a continuous ring. Its width is between 30% and 50% larger than previously announced. We also verified that the ring behaves like a firefly. It can only be seen from time to time, when Cassini, the ring and the Sun are arranged in a particular geometric configuration, in very high phase angles. Otherwise, it remains "in the dark", not visible to Cassini's cameras. Through numerical simulations, we found a very short lifetime for the ring particles, less than a couple of decades. Consequently, the ring needs to be constantly replenished. Using a model of particles production due to micrometeorites impacts on the surfaces of Janus and Epimetheus, we reproduce the ring, explaining its existence and the "firefly" behavior.