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Europa's surface composition and evidence for cryovolcanic activity canprovide insight into the properties and composition of the subsurface ocean,allowing the evaluation of its potential habitability. One promising avenue forrevealing the surface processing and subsurface activity are the relativefractions of crystalline and amorphous water-ice observed on the surface, whichare influenced by temperature, charged particle bombardment, vapor deposition,and cryovolcanic activity. The crystallinity observed on Europa's leadinghemisphere cannot be reproduced by thermophysical and particle flux modelingalone, indicating that there may be additional processes influencing thesurface. We performed a spectral mixture analysis on hyperspectral image cubesfrom the Galileo Near-Infrared Mapping Spectrometer (NIMS) to identify howsurface crystallinity is influenced by physical processing at a high spatialresolution scale. We focus specifically on two image cubes, 15e015 closer tothe equator and 17e009 closer to the south pole, both on the leadinghemisphere. We performed a nonnegative least-squares spectral mixture analysisto reveal both the non-ice composition and the water-ice crystallinity of thesurface. We found that amorphous water-ice dominates the spectrum at theequator and the south pole. We estimated a mean crystallinity of ~35% withinthe 15e015 NIMS cube and a mean crystallinity of ~15% within the 17e009 NIMScube, which is consistent with ground-based spectroscopically derivedcrystallinities. We also identified a correlation of magnesium sulfate,magnesium chloride, and hydrated sulfuric acid with lineae and ridges, whichmay provide evidence for surface processing by upwelling subsurface material.

Europa's Surface Water-ice Crystallinity and Correlations between Lineae and Hydrate Composition