The inner moons of Saturn – Mimas, Enceladus, Tethys, Dione and Rhea - exhibit remarkable large spatial scale albedo and color variations. The albedo trends with orbital distance can be linked to a combination of processes including E-ring grain bombardment and charged particle bombardment. One of the fascinating concepts learned about the Saturn system by instruments on the Cassini orbiter is that, though their surface compositions are dominated by water ice, and evidently linked to E ring grain bombardment, the icy satellites are spectrally red: they are absorbing in the ultraviolet-visible wavelength region (wavelengths &lt; ∼550 nm) – a spectral characteristic not typical of water ice. Thus, some basic questions are: What is the species or process that causes this UV– visible spectral redness? Is the absorber a photolytic or radiolytic (i.e. space weathered) product, or a combination of both? Is it native to the Saturn system? What is the relationship (if any) to the Enceladus plume gases and E-ring?<br/>The usual approach to answering surface composition questions is to use visible and near-infrared (VNIR) spectra, and indeed this has been done with success in the Saturnian system. However, VNIR spectra alone often do not tell the entire compositional story. The reddish UV-visible absorption, present to varying degrees on all of the satellites, could be due to several contributors, all of which are not very spectrally active in the near-IR. In this presentation, I investigate the system-wide trends affecting the surface compositions of Saturn’s inner icy moons. Here I look at visible and UV (300nm) geometric albedos and UV absorption depths of the leading and trailing hemispheres, to understand their relationships to E ring flux, plasma flux and energetic electron intensity. I use composite spectra to quantify the effects of dust, plasma and energetic electrons on the visible color and on the UV albedo and absorption.

Multi-spectral observations of Saturn's icy moons to probe exogenic effects

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.