Mantle plume interactions and the spacing of Tharsis and Elysium on Mars

Tharsis and Elysium are the two largest magmatic provinces on Mars and are characterized by large geoid anomalies and extensive volcanism. Such features on Earth and other terrestrial planets have been explained by mantle plumes. Analytical and numerical studies indicate that the flow excited by one plume can draw neigboring plumes nearer, leading to clustering and merging of mantle plumes. If Tharsis and Elysium, which lie some 98 degrees from each other and have been active for much of Mars' history, are indeed underlain by large plumes, then there might be significant interactions between the two. We investigate the spacing of model mantle plumes by calculating the Stokes flow that one plume excites in the neighborhood of another in order to determine a characteristic interaction distance. We find that plumes beneath Tharsis and Elysium fall outside of the separation at which we would expect them to cluster.