Convective modelling of gravity, topography and melt generation at the Tharsis Rise, Mars

The observed long-wavelength gravity and topography at the Tharsis Rise, and the inferred heat flux and melt generation rate, are modelled using a convection code. The code is axisymmetric and isoviscous and incorporates a conductive lid and the effects of lithospheric rigidity on the observables. Models which fit the observations have high mantle viscosities (5-28×10 Pa s) and 80% or less internal heating. Although the melt generation results are sensitive to the (poorly known) mantle temperature, the other observables are not. The high viscosities are consistent with a dry, and probably cold, Martian mantle, and are also suggested by simple scaling arguments. The internal heating rates are consistent with values obtained from parameterized thermal evolution models.