LIMB PROFILE ANALYSIS OF RIDGES ON ENCELADUS
Our method of analyzing limb images with derived elevation profiles emphasizes regional structure and individual ridge morphology. Profiles are derived from images that include smaller limb arcs at higher resolution than previously derived by Thomas (Icarus 208, 395–401, 2010). These limb images and corresponding profiles are compared with the ISS Enceladus global basemap and supplemental reprojected images to corroborate ground trace locations. Discernible features, starting with the most prominent, are then located and linked among the derived profiles and all images. The heights of key features, calculated using shadow lengths, and their distances from respective ground trace are used to evaluate the visibility of those features on the skyline. We can then identify those individual ridges that are unobstructed by nearby features in either the foreground or background. The derived elevation profiles of those unobstructed ridges can indicate characteristics such as symmetry and slope angle. For instances where the ground traces of multiple limb images cross or are in close proximity, along-trend changes in ridge characteristics are examined. The basemap and supplemental images detail the associated surface features, ridge and trough linearity, and other relevant characteristics, which can be integrated with the cross-sectional ridge morphology to help constrain origin. Current analyses can resolve a feature with topographic changes of 0.2 km when spanning 1 km along the skyline. Additional work will resolve smaller features and those with less drastic changes. Preliminary results suggest the large ridges of the trailing hemisphere are symmetric while ridge profiles to the northeast are asymmetric and may indicate tilted blocks. Regional changes in average topography both within apparently similar terrain and along borders between different terrain types are also analyzed.