Geologic mapping of the northern leading hemisphere of Europa from Galileo solid-state imaging data

The northern leading hemisphere of Europa was imaged at regional mapping resolution (similar to 230 m/pixel) by the Galileo spacecraft SSI camera. We produced geologic maps from a regional-scale mosaic and a high resolution inset of this region. Twelve geologic units were sufficient to produce correlative geologic maps at both regional and local scales. Stratigraphic relationships indicate four major episodes in the geologic history of this area: The first episode includes background plains formation and modification, followed by a second period of extensive lineament formation. The third episode included extensive chaotic disruption of the surface at low and middle latitudes. The final episode includes the formation of new sets of ridges and bands, especially at high latitudes. The low crater density indicates that all these episodes in Europa's geologic history are geologically recent. The latitudinal distribution of chaos areas broadly matches that of areas of crustal thinning from models of tidal heating. We show that stress directions rotated clockwise with time, which is consistent with predictions from global stress models involving tidal deformation and nonsynchronous rotation of Europa's crust. On the basis of the change in lineament orientation with time, the reconstructed longitudinal positions of the studied area indicate that Europa's crust completed a full rotation relative to the tidally deformed interior.