Abstract DGP2026-130

The interior structure and geodynamic style of Venus are largely unknown. One of the most informative ways available to investigate the planet’s interior is through the joint analysis of gravity and topography data, which were lastly obtained by NASA’s Magellan mission (1990-1994). Several studies have shown that the long-wavelength (over ~1000 km) gravity and topography signature of Venus is dominated by convective flows in the mantle (e.g. Sjogren et al., 1980, Banerdt et al. 1986, Kiefer et al. 1986), commonly referred to as dynamic support.

The analysis of long-wavelength gravity and topography were performed by several to better understand Venusian mantle properties. Many of these made use of the dynamic loading model developed by Hager and Clayton (1989), where mantle flows, triggered by density anomalies, depend on radial viscosity variations. This model has been applied by several studies to estimate the spatial distribution of mantle mass anomalies (e.g. James et al. 2013) and to investigate the planet mantle viscosity structure (Pauer et al. 2006, Maia et al. 2023). However, these studies make use of a simplistic and inefficient approach to model the viscosity profile, in which the mantle is divided in 4–5 layers of constant viscosity which can freely vary in magnitude. This approach has the drawback of having a large number of free parameters, which linearly increase with the number of viscosity layers added, and allow for physically unrealistic viscosity structures.

We present a new investigation that performs a more robust parametrization to estimate the viscosity profile of the mantle. This is done through the use of pressure- and temperature-dependent Arrhenius Equation. This approach not only allows for more physically robust viscosity structure constraints, but directly provides insights on key rheological parameters, such as the activation volume, mantle potential temperature and thermal lithosphere thickness, which are essential to constrain geodynamic models. Similar to Maia et al. (2023), we adopt the nested sapling technique to perform the inversion and a multitaper spatio-spectral localization approach (Wieczorek and Simons, 2007) to suppress the signals of highlands predominantly supported by thickened crust.

The next step of this investigation is to apply the inversion to more localized regions of Venus, namely Atla, Beta and Phoebe Regio. This would allow us to verify if Venus’s mantle shows lateral viscosity variations and to investigate if the low viscosity zone predicted in Maia et al. (2023) is global or regional.