A Survey of Low-Velocity Collisional Features in Saturn's F Ring

TL;DR

This paper provides a comprehensive analysis of over 800 mini-jets in Saturn's F ring, revealing their distribution, morphology, and lifetimes, and inferring the properties of their moonlet progenitors.

Contribution

It offers the first detailed statistical study of F ring mini-jets, constraining the size, orbit, and collision dynamics of the underlying moonlet population.

Findings

Mini-jets are randomly distributed in longitude and time.

Mini-jets have typical lifetimes of about 1 day.

Repeated collisions suggest a population of <~1 km objects.

Abstract

Small (~50km scale), irregular features seen in Cassini images to be emanating from Saturn's F ring have been termed mini-jets by Attree et al. (2012). One particular mini-jet was tracked over half an orbital period, revealing its evolution with time and suggesting a collision with a local moonlet as its origin. In addition to these data we present here a much more detailed analysis of the full catalogue of over 800 F ring mini-jets, examining their distribution, morphology and lifetimes in order to place constraints on the underlying moonlet population. We find mini-jets randomly located in longitude around the ring, with little correlation to the moon Prometheus, and randomly distributed in time, over the full Cassini tour to date. They have a tendency to cluster together, forming complicated `multiple' structures, and have typical lifetimes of ~1d. Repeated observations of some features show significant evolution, including the creation of new mini-jets, implying repeated collisions by the same object. This suggests a population of <~1km radius objects with some internal strength and orbits spread over 100km in semi-major axis relative to the F ring but with the majority within 20km. These objects likely formed in the ring under, and were subsequently scattered onto differing orbits by, the perturbing action of Prometheus. This reinforces the idea of the F ring as a region with a complex balance between collisions, disruption and accretion.