Venus topography and kilometer-scale slopes

During the first 8 months of the Magellan mission, the radar altimeter has made some three million measurements of the surface of Venus covering the latitude range from 85°N to 80°S. Methods involving range correlation, Doppler filtering, multi-burst summation, and range migration are used to focus the observations and to achieve high surface resolution. Results are presented as maps of the global distribution of topography, meter-scale roughness, and power reflection coefficient. The results are similar to those reported in previous experiments (surface heights exhibit a unimodal distribution with more than 80% of the surface lying within 1 km of the 6051.84-km mean radius) but the higher resolution of the Magellan altimeter has disclosed several surprisingly steep features, e.g., the southwest face of the Maxwell Montes, the southern face of the Danu Montes, and the chasmata to the east of Thetis Regio, where average kilometer-scale slopes of greater than 30° are not uncommon. This conclusion is corroborated by close inspection of synthetic aperture radar imagery.