Venus Resurfacing Constrained by Geoid and Topography

Abstract

AbstractThe 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 3‐D 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 heat flow 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 heat flow decays over 1 Gyr after the cessation of mobile‐lid tectonics. The heat flow 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.