The Mantle Viscosity Structure of Venus

The long-wavelength gravity and topography of Venus are dominated by mantle convective flows, and are hence sensitive to the planet's viscosity structure and mantle density anomalies. By modeling the dynamic gravity and topography signatures and by making use of a Bayesian inference approach, we investigate the viscosity structure of the Venusian mantle by constraining radial viscosity variations. We performed inversions under a wide range of model assumptions that consistently predicted the existence of a thin low-viscosity zone in the uppermost mantle. The zone is about 235 km thick and has a viscosity reduction of 5-15 times with respect to the underlying mantle. Drawing a parallel with the Earth, the reduced viscosity could be a result of partial melting as suggested for the origin of the asthenosphere. These results support the interpretation that Venus is a geologically active world predominantly governed by ongoing magmatic processes.

Automated summary

In this study, the viscosity structure of the Venusian mantle was investigated by modeling the dynamic gravity and topography signatures and using a Bayesian inference approach. The results revealed the existence of a thin low-viscosity zone in the uppermost mantle, about 235 km thick, with a viscosity reduction of 5-15 times compared to the underlying mantle. This reduced viscosity may be a result of partial melting, similar to the asthenosphere in Earth, indicating that Venus is predominantly governed by ongoing magmatic processes.