Mantle dynamics on Venus: insights from numerical modelling
Summary
Numerical modelling studies of the various hypotheses of Venus' thermal evolution, such as the uniformitarian, catastrophic, differentiated planet hypothesis have been conducted. However, these studies often failed to investigate the influence of the mantle thickness and core-mantle boundary temperature on their results. As these parameters are not very well constrained, a modelling study was conducted to assess their influence. Besides that, the influence of the rarely used temperature-dependent conductivity was investigated and the first numerical validation of the subcrustal lid rejuvenation hypothesis was conducted. A two dimensional, Cartesian, square box was used with free slip boundary conditions and isothermal top and bottom boundaries. A temperature dependent viscosity with the inclusion of a yield stress was used. It was found that the mantle thickness determines whether or not a periodic regime can be accommodated: a thin mantle cannot result in a periodic regime. To a lesser extent, the core-mantle boundary temperature influences this as well. This is particularly the case, when it is combined with the temperature-dependent conductivity, which causes the periodic regime to be stable over a larger range of yield stresses. In order to obtain more realistic models in the future, additional heat sources should be added to the model in the form of shear heating, adiabatic heating and internal heat production.