Linear structures on the small inner satellites of Saturn

Shape modelling methods developed for non-spherical worlds were applied to four satellites of Saturn: Prometheus, Pandora, Janus, and Epimetheus. This results in the first detailed shaded relief maps of their surfaces. Ridges and valleys are described with their implications for satellite history and asteroid 951 Gaspra. They probably result from fracturing during break-up of parent bodies and/or later large impacts. Prometheus and perhaps Gaspra may be coated with debris from parent body fragmentation as well as more recent regolith. These four satellites are covered by relatively few useful images, so the shapes are imperfectly known and positions of features on maps may be wrong by up to a few tens of degrees in some areas (worst where a feature is seen only near a limb). Nevertheless, these shape models are more useful than the previous triaxial ellipsoid models.