The Thermal State and Interior Structure of Venus: Insights from Global Geodynamic Models

Similar to the Earth in size, mass, and potentially composition, Venus is often referred to as our sister planet. However, today’s Venus represents one of the most extreme places in the Solar System. It possesses a dense CO₂ atmosphere with a surface pressure 90 times higher than the Earth and surface temperatures able to melt lead. Its young surface is dominated by volcanic features at all spatial scales (Hahn & Byrne, 2023), and recent reanalysis of Magellan radar data suggests that Venus might be volcanically active today (Herrick & Hensley, 2023; Sulcanese et al., 2024).

The large variety of tectonic features at Venus’ surface range from rift zones of thousands of kilometers in length (Foster and Nimmo, 1996), to wide-spread distribution of wrinkle ridges (Billoti and Suppe, 1999), and a substantial number of round formations consisting of a ring wall and radial cracks and fractures in the interior (the so-called coronae), some of which have been associated with regional subduction processes (Davaille et al., 2017). These tectonic structures bear witness of geological processes that have shaped Venus’ surface.

Limited constraints for the deep interior of Venus are available from measurements of the tidal Love number k₂ = 0.295±0.066 (Konopliv & Yoder, 1996), which is sensitive to the size and state of the core, and from the moment of inertia factor (MoIF), which describes the distribution of mass in the interior suggesting a core radius of 3500±500 km (Margot et al., 2021). The phase lag of the deformation, whose value is particularly sensitive to the thermal state of the interior, has not yet been measured but will be constrained by future missions.

Venus has a higher correlation of gravity and topography for long wavelengths and a globally large apparent depth of compensation (Sjogren et al., 1980). Recently, Maia et al. (2023) showed that a viscosity jump at 700 km depth (corresponding to ringwoodite-bridgmanite phase transition) is inconsistent with the observations, while a 250-km-thick low-viscosity layer at the base of the lithosphere is favored by the data.

In this study, we run global scale thermal evolution models in a 3D spherical geometry to investigate the full thermal evolution and the spatial distribution of the temperature field in the interior of Venus at present day. We use the geodynamical convection code GAIA-v2 (Hüttig et al., 2013) and solve numerically the conservation equations of mass, linear momentum. Our models use a pressure- and temperature-dependent viscosity following Arrhenius law, and include pressure- and temperature-dependent thermal expansivity and conductivity adopting the parametrizations described in Tosi et al., (2013). We consider partial melting and the effects of magmatic intrusions that can considerably affect the thermal state of the lithosphere (Herrera et al., 2026), leading to the so-called plutonic squishy lid geodynamic regime (Lourenço et al., 2020). In this regime, regional scale surface mobilization and lithospheric foundering can occur.

Our models consider the effects of core cooling and radioactive decay as appropriate for thermal evolution modeling. We include the effect of solid-solid phase transitions and vary the size of the core and the viscosity of the mantle. For the viscosity we test reference values of 1e20, 1e21, and 1e22 Pa s, and vary its increase with depth over several orders of magnitude. As the interior structure of Venus is poorly constrained, we investigate models with a core radius between 3025 km and 4000 km (Margot et al., 2021).

We find that only models with a core radius between 3025 km and 3750 km are compatible with current estimates of the tidal Love number k₂. Our models also show a lower tidal quality factor for Venus compared to solid Earth, which suggests a hotter interior. The increase of viscosity with depth needs to be lower than two orders of magnitude to avoid a significant decrease of the spectral correlation and admittance, at odds with observations. Models compatible with high thermal gradients, as inferred from elastic lithosphere thickness studies (see Maia et al. 2025, for a summary), suggest that a substantial fraction of melt produced in the interior remains trapped in the lithosphere as magmatic intrusions. In such cases, we observe a strong interaction between plumes and the lithosphere, amplified by the presence of magmatic intrusions.

Future measurements of the NASA VERITAS (Smrekar et al., 2022) and ESA EnVision (Straume-Lindner et al., 2025) missions will provide unprecedented information to address the interior structure and thermal history of Venus, and will help refine models of the interior evolution.

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