Peculiar rainbows in Saturn's E ring: Uncovering luminous bands near Enceladus

TL;DR

This study identifies luminous, stripe-like diffraction patterns in Saturn's E ring caused by periodic ice particle structures, revealing new insights into ring composition and Enceladus' plume activity.

Contribution

It uncovers a novel diffraction-based phenomenon in Saturn's E ring linked to periodic ice structures, advancing understanding of ring particle arrangements.

Findings

Stripe-like diffraction patterns observed in E ring.

Periodic structure likely composed of fresh ice particles.

Patterns linked to Enceladus' plume activity.

Abstract

We report observations of stripe-like features in Enceladus' plumes captured simultaneously by Cassini's VIMS-IR and ISS NAC instruments during flyby E17, with similar patterns seen in VIMS-IR data from flyby E13 and E19. These parallel stripes, inclined at approximately 16$^{\circ}$ to the ecliptic and 43$^{\circ}$ to Saturn's ring plane, appear continuous across images when projected in the J2000 frame. A bright stripe, most visible at wavelengths around 5 $\mu$m, acts as the zeroth-order diffraction peak of a reflection grating with an estimated groove spacing of 0.12$-$2.60 mm, while adjacent stripes are attributed to higher-order diffraction peaks. We suggest that this light-dispersing phenomenon originates from an inclined periodic structure within Saturn's E ring. This structure, constrained between Saturn's G ring and Rhea's orbit, likely consists of fresh ice particles supplied by Enceladus' plumes.