Flexure of Venusian lithosphere measured from residual topography and gravity

Abstract

The elastic lithosphere thickness Te for various locations on Venus is estimated by modeling lithospheric flexure associated with rifts, coronae, chasmata, and the moats visible around certain large volcanoes. By modeling flexure using the residual topography, a range of elastic thicknesses was found, from around 10 to 40 km or greater. A number of these values are not well-determined and only constrain Te to be > 10 km. The shear stresses predicted from the topography, given these values for Te, reach several hundred MPa, with surface faulting visible in the synthetic aperture radar (SAR) images at many locations. The elastic thickness was also estimated at seven volcano-like structures by modeling the gravity predicted from the observed topography. This yielded elastic thickness estimates varying between approximately 20 and 60 km, which were generally more tightly constrained. However, an elastic thickness of 25 km fits almost all the observed profiles within uncertainty, and the results from modeling the gravity yield an average global elastic thickness of 29 ± 6 km. There is no evidence that the elastic thickness falls anywhere outside this range. The lack of large-scale regional variations in Te on Venus, in contrast to the situation observed on the Earth, is consistent with a lack of water and plate tectonics on Venus.