Surface temperature and mantle viscosity influence the cooling efficiency of magmatic styles on Venus

Reconstructing Venus’s early evolution and determining whether it once had Earth-like, temperate conditions remain challenging because its surface is geologically young. Climate models suggest that Venus may have maintained mild temperatures and even liquid water until <1 Ga (Way et al., 2016), while other work suggests that Venus might have had high surface temperature over most of its history, with values possibly even higher than today (Noack et al., 2012). At the same time, the surface temperature is strongly linked to the volcanic and outgassing history, and thus to the presence of volatiles in the interior. Some studies suggest that the interior is intrinsically dry (Constantinou et al., 2024), while others indicate that at least the lower mantle might still contain volatiles (Smrekar & Sotin, 2012). The presence of volatiles can substantially affect the mantle viscosity that, in turn, affects the thermal, magmatic, and outgassing history.   

Venus’s geodynamic regime is heavily debated (Rolf et al., 2022), but recent evidence of ongoing volcanic activity (Herrick & Hensley, 2023) indicates that magmatic processes could still play a key role today. Early geodynamic models that included magmatism considered only extrusive magmatism, known as heat-pipe regime (Moore & Webb, 2013). Recent studies investigated scenarios where magmatic intrusions dominate, known as plutonic-squishy regime (Lourenco et al., 2020). Although current surface and lithospheric conditions suggest a highly intrusive magmatic style (Maia et al., 2025), the relative roles of intrusive and extrusive magmatism in regulating mantle cooling for different surface temperature scenarios and rheological conditions remain unexplored.

We test different surface temperature and mantle viscosity values and model their effect on the long-term cooling on Venus and Venus-like planets, using the geodynamic code GAIA in a 2D spherical annulus geometry (Hüttig et al., 2013; Fleury et al., 2024). We assume a temperature- and depth-dependent viscosity following an Arrhenius law (Hirth & Kohlstedt, 2003), and pressure- and temperature-dependent thermal conductivity and expansivity (Tosi et al., 2013). We model the decay of radioactive heat-producing elements and cooling of the core. Melting occurs when mantle temperatures exceed the solidus (Stixrude et al., 2009).

Our results show that surface temperature and mantle viscosity are key factors in determining the efficiency of planetary cooling for different magmatic styles (intrusive or extrusive). A high surface temperature, like Venus’s current 737 K, shows a more efficient cooling when intrusive magmatism is considered, while cooler surfaces (~500 K) lead to stronger mantle cooling for an extrusive magmatism scenario, for cases assuming a reference viscosity of ~10²¹ Pa s. Mantle viscosity modulates this behavior: lower viscosities (~10²⁰ Pa s) allow planets with cold surfaces to cool more efficiently if intrusions are present, while higher viscosities (~10²² Pa s) with hot surfaces cool more efficiently if extrusive magmatism dominates. These findings suggest that Venus’s surface conditions and mantle properties over time play a crucial role in its thermal and magmatic evolution, offering insights into the potential habitability of Venus-like exoplanets, where the balance between intrusive and extrusive magmatism likely governs long-term surface-mantle interactions and volatile cycling.