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Large-scale features of the crustal structure on Mars, including the hemispherical dichotomy and Tharsis, were established very early in planetary history. Geodynamical models for the origin of the dichotomy and Tharsis, such as lithospheric recycling and a plume from the core-mantle boundary, respectively, involve solid-state mantle flow and are difficult to reconcile with timing constraints. An alternative point of view is that the martian crustal asymmetry and Tharsis can be associated with the upwelling and spreading of large, impact-induced melt regions, i.e., local magma oceans.

While the local magma ocean–induced upwelling model satisfies timing constraints on dichotomy and Tharsis formation, it neglects any interaction with longer-timescale mantle dynamics and cannot explain recent volcanic activity at Tharsis. In this study, fully 3-D, spherical shell simulations are used to investigate coupling between local magma oceans and mantle dynamics with radiogenic heating and core heatflow. For low core heat flux, it is found that upwellings driven by local magma ocean buoyancy are transient features of planetary evolution that is dominated by sublithospheric instabilities. With increasing core heat flux, local magma ocean–induced upwellings strongly influence the pattern of thermal plumes from the core-mantle boundary, which can remain stable for ∼4.5 b.y. The predicted melt volumes, present-day melting rate, and crustal structure are compared to observational constraints.

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