Viscosity and Thermal Conductivity of Iron‐Rich Silicate Melts at the Martian Core‐Mantle Boundary: Implications for a Basal Molten Layer

Seismic observations from the NASA InSight mission have sparked broad interest in the potential existence of a basal molten layer (BML) at the core‐mantle boundary of Mars. Resolving the physical properties of this putative layer is crucial for understanding the thermal evolution and dynamo history of the planet. While previous studies have proposed a conductive state for the BML based on high reference viscosities of the solid mantle, the actual mechanism of heat transport—conduction or convection—remains unresolved due to the lack of constraints on key parameters, including density, viscosity, and thermal conductivity. Here, we employ molecular dynamics simulations to determine these properties of iron‐rich silicate melts under deep‐mantle conditions. Our results indicate that the gravitational stability of the BML requires at least ∼30 wt% FeO, corresponding to a minimum melt density of ∼4.0 g/cm 3 . This FeO concentration is significantly higher than that of the overlying Martian mantle, implying viscosities in the range of 0.01–0.4 Pa·s, many orders of magnitude lower than the high viscosities assumed in previous models, and thermal conductivities of 2.3–2.7 W/m/K. Scaling analysis and geodynamic simulation reveal that when BML viscosity falls below 10 19 Pa·s, convection dominates heat transport and intensifies with decreasing viscosity, which strongly enhances core heat flux and accelerates core cooling, thereby influencing Martian mantle dynamics.