Constraints of the topography, gravity and volcanism on Venusian mantle dynamics and generation of plate tectonics

Venusʹs mantle convection model was studied in a three-dimensional spherical shell domain with depth- and temperature-dependent viscosity. Numerical results show that key observations of Venus including the number of major “hotspot” volcanic systems, spectral patterns of the surface topography and geoid at long- and intermediate-wavelengths can be explained in models that have a spinel-to-post-spinel endothermic phase change of −3.5 MPa/K Clapeyron slope and averaged mantle viscosity of 2×1021 Pa s (i.e., convective Rayleigh number of 1.8×107). Our models with the endothermic phase change show relatively weak time-dependence, suggesting that the phase change may not be the primary cause for “catastrophic” resurfacing on Venus. Our calculations also show that Venus cannot have a weak asthenosphere that is similar to that on the Earth, in order to match the observations, thus supporting a key role of asthenosphere in producing plate tectonics.