The influence of a long-lived basal magma ocean on the coupled core-mantle evolution of Mars

Recent seismic observations suggest the presence of a basal molten layer above the Martian core that may represent a long-lived basal magma ocean (BMO). However, its influence on the coupled thermal evolution of the Martian mantle and core remains poorly understood. Here, we employ a two-dimensional mantle convection model coupled with parameterized thermal evolution models for the core and BMO to investigate the long-term interior evolution of Mars. Our results show that a long-lived BMO modifies core-mantle thermal coupling by regulating heat exchange between the core and mantle and maintaining elevated temperatures in the lowermost mantle. In particular, enrichment of heat-producing elements (HPEs) within the BMO enhances deep interior heat retention, suppresses secular core cooling, inhibits inner-core growth, and promotes present-day mantle plume activity. We further find that reconciling a long-lived BMO with a present-day solid inner core requires both limited enrichment of HPEs within the BMO and relatively high core liquidus temperatures, which may be difficult to satisfy simultaneously. These results offer constraints on the thermal and magnetic evolution of Mars and highlight the importance of coupled mantle-BMO-core dynamics on Mars.