Polarization Analysis of Enceladus’ Surface

Abstract

Enceladus, the sixth largest moon of Saturn, is known to be a geologically active icy body. Observations by NASA's Cassini spacecraft show that Enceladus has cryovolcanoes on its south pole as well as a global subsurface ocean hidden beneath its frozen crust. Photographs from NASA's Cassini Spacecraft during flybys of Enceladus document Enceladus's surface and the cryovolcano plumes. It is known that larger particles ejected from the cryovolcanoes deposit on the surface, while smaller particles escape into Saturn's E-ring. Cassini observations of the sunlight scattered by the plume particles on the surface may provide information about the plume composition and potentially the dynamics of the ocean below. This work presents Enceladus’ disk-averaged degree of linear polarization (DoLP), which has yet to be analyzed, and compares it to spherical, spheroidal, cylindrical, and hexagonal ice particles simulated by light scattering codes ADDA and T-Matrix using a multiple-scattering approximation. The Pearson correlation coefficient is used to quantify the fit of each morphology to the surface polarization data in the GRN (569 nm) and MT2 (727 nm) wavelength filters. The polarization of Enceladus’ surface implies the particles are likely non-spherical, and possibly occur in a narrow size distribution near a mean of two microns in radius.