The Mantle Viscosity Structure of Venus

Abstract

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.

Dynamic Component of the Asthenosphere: Lateral Viscosity Variations Due To Dislocation Creep at the Base of Oceanic Plates

“…The presence or absence of asthenosphere is often debated in the context of Venus (e.g., Pauer et al, 2006). Recently, Maia et al (2023) performed a global inversion of Venus's geoid and topography using a Bayesian inference approach. They inferred a ∼235 km thin, low-viscosity zone with a viscosity reduction of 5-15 times with respect to the underlying mantle.…”

Estimates on the Possible Annual Seismicity of Venus

“…They interpreted these changes as new volcanic flows and hence ongoing volcanic activity on Venus. In addition, recent gravity and topography analysis indicate that Venus has a thin low viscosity zone which could be interpreted as an indication of partial melting in the mantle (Maia et al., 2023). In line with that, recent estimates from scaling the volcanism of Earth to Venus yield 12–42 volcanic eruptions on Venus in a year, depending on assumptions on the amount of volcanism associated with plume‐induced subduction at coronae (Byrne & Krishnamoorthy, 2022; Van Zelst, 2022).…”