Mimas' far-UV albedo: Spatial variations
Johnson, Robert E.; Buratti, Bonnie J.; Hendrix, Amanda R.; Paranicas, Chris; Hansen, Candice J.; Kollmann, Peter; Roussos, Elias; Cassidy, Timothy A.; Teolis, Ben; Todd Bradley, E.
United States, Germany
Abstract
We present Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of Mimas at far-ultraviolet wavelengths (170-190 nm) which show an interesting albedo gradient across the anti-saturnian hemisphere. We discuss the photometric behavior of Mimas in the far-UV and review the important exogenic processes and their expected effects, relevant over a wide range of wavelengths. We suggest that the UVIS images display the brightening effects of E-ring grain accretion on Mimas' trailing hemisphere; we also show VIMS results that are consistent with E-ring grain accretion on the trailing hemisphere. The UVIS results also suggest the presence of hydrogen peroxide, predominantly in the southern hemisphere, produced by photolysis; this is expected to be a seasonal effect as a result of enhanced UV insolation during the recently-ended southern summer.