Dynamics of Lithospheric Overturns and Implications for Venus's Surface

Abstract

AbstractVenus is currently characterized by stagnant‐lid mantle convection, but could have previously experienced episodes of global resurfacing due to lithospheric overturn. Using numerical models of Venus's interior, we attempt to explain Venus's surface characteristics in the context of interior evolution and to understand how Venus's tectonic history has diverged from Earth's. For both the stagnant‐ and the episodic‐lid regime, we explore the role of reference mantle viscosity; for the latter regime, we also explore the role of the lithospheric yield stress. Our stagnant‐lid models predict thicker crust and younger surface than typically inferred from cratering statistics. When considering resurfacing episodes, the yield stress influences the frequency of overturns, which limits crustal thickness to better agree with previous independent estimates. Surface age is variable and depends on overturn frequency and resurfacing rate between overturns but reaches larger values just before an upcoming overturn event compared to values in the stagnant‐lid cases. Both regimes predict substantial lateral variations in surface age, instead of an end‐member uniform surface age indicating the cessation time of the last overturn, because ongoing volcanic resurfacing is spatially heterogeneous and dominates over tectonic resurfacing. Reviewing the crater‐based surface age variations suggests that the model‐predicted age spreads in the episodic scenario could be consistent with Venus's cratering record. Moreover, we find that a small fraction of crust can resist recycling during overturns. These outcomes indicate that overturn events may allow for surface age variations that reproduce Venus's surface better than stagnant‐lid models.