The local topography of Uruk Sulcus and Galileo Regio obtained from stereo images

High resolution (<100 m/pixel) stereo images obtained by the Galileo SSI camera are analyzed using photogrammetric techniques to derive local Digital Terrain Models (DTMs) of Ganymede's surface. The models cover areas of 22 x 56 km in Uruk Sulcus and 63 x 102 km in Galileo Regio and have spatial resolutions of 500 m/pixel and 1000 m/pixel, respectively. For Uruk Sulcus, the DTM features a wave-like topography with wavelengths of 2-6 km and amplitudes of up to 500 m. Individual topographic highs show asymmetric shapes with slopes of up to 20 degrees and terracing, The terrain model in Galileo Regio has isolated knobs, furrows of up to 10 km in width, and ridges of up to 1 km in height, Surface roughness in Galileo Regio at DTM scales is markedly higher than in Uruk Sulcus. Bowl-shaped craters are identified in the models with depth to diameter ratios of about 1:12 (Uruk Sulcus) and 1:9 (Galileo Regio), This is in approximate agreement with data for simple craters measured in Voyager images. The large complex 20-km crater Ea is found to have a central dome 300 m above the crater floor, reaching more than half of the crater rim's height. These unique topographic data, at far higher resolution than what could be derived from Voyager images, will provide new insights into the formation of Ganymede's surface. (C) 1998 Academic Press.