Venus Resurfacing Constrained by Geoid and Topography

The primary explanations for the young crater age of the surface of Venus are progressive volcanic resurfacing and a period of mobile-lid tectonics. The role of initial conditions, mantle potential temperature, and core potential temperature on Venus surface mobility are explored using 3D spherical mantle convection calculations with a lithospheric yield-stress that allows the fluid to adopt either a stagnant or mobile lid. The small offset between the center of mass and center of figure (CM-CF) of Venus is reproduced in calculations that never undergo a period of mobile-lid convection. The CM-CF offset has never been used in the evaluation of geodynamic models for Venus. The mobile-lid calculations have a CM-CF offset that is four times the observed offset and, the offset increases significantly at the onset of a mobile lid/resurfacing event. Furthermore, the rapid increase in core mantle boundary heatflow that occurs as the cold lithospheric material interacts with the core mantle boundary during a mobile-lid event is sufficient to power a core dynamo, even in the absence of inner core solidification. The core mantle boundary heatflow decays over 1 Gyr after the cessation of mobile-lid tectonics. The heatflow never reaches a level that would power a thermally-driven dynamo in calculations that do not undergo mobile-lid convection. The calculations indicate that Venus young surface age is not the result of a mobile-lid resurfacing event while progressive resurfacing is consistent with the observations.