High-resolution Magellan stereo topography at Salme Dorsa

Abstract:

Most of the proposed cases of subduction at Venus have arisen from studies of large coronae like Artemis and Latona. However, there are other cases where the topographic and morphologic features show significant lithospheric bending and are suggestive of subduction. Salme Dorsa, a relatively small ridge belt just east of Fortuna Tessera, is such a case. Away from its western margin, Magellan altimetry and previous stereo-derived topography show a trough and a bulging high in manner similar to what is seen at subducting margins on Earth. Lateral stresses imposed by Ishtar Terra and Fortuna Tessera would lead to compression, shortening and thickening at Salme. Our processing of Magellan stereo data from the original F-BIDRs into digital elevation models (DEM’s) has revealed the topography at Salme Dorsa to an unprecedented degree of detail. While Magellan altimetry and previous stereo data agree on the bended lithospheric topography towards the west, they show the majority of the ridge belt consisting of low topography and not properly correlating with some of the morphologic features seen in the radar images. Our DEM agrees with the previous bending profiles, but shows the trough to be much narrower and the majority of the belt to correspond to elevated topography. The trough, 50-km wide and at an elevation of 900 m at its deepest point in previous data, is much narrower, close to 20 km, and shallower by 300 m. The most notable difference is that our DEM now resolves the proper height and width of the belt (1200 m and 120 km, respectively), with individual ridges being 400 m high and 20 km wide. The overall topographic profile is consistent with crustal shortening and potentially depicts multi-wavelength deformation suggestive of rheological layering. The better topographic data can now serve to properly constrain different loading contributions and deformation models. Our high-quality, high-resolution (300-m postings) stereo-derived DEMs illustrate how much medium- and fine-scale detail has been missed thus far in the study of Venus, and they make the case for a renewed effort, like the one being proposed for VERITAS, to map the surface of Venus in global fashion at far better resolutions.