Peculiar Rainbows in Saturn's E Ring: Uncovering Luminous Bands Near Enceladus

Abstract

International audienceWe 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° to the ecliptic and 43° to Saturn's ring plane, appear continuous across images when projected in the J2000 frame. A bright stripe, most visible at wavelengths around 5 μm, 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