Geological evidence for a migrating Tharsis plume on early Mars

The Tharsis bulge is the largest magmatic/volcanic center on Mars and in the solar system, having a volume of ~ 3 × 108 km3, with the majority of its mass emplaced more than 3.7 billion years ago. The igneous history of Tharsis has been implicated in the generation of an atmosphere and hydrosphere capable of clement conditions on early Mars. It has been proposed that an early plume migration from the southern highlands of Mars relative to a one-plate lithosphere led to the development of the Tharsis bulge in its current location along the Martian crustal dichotomy. We used geologic mapping, crustal magnetic data, crater age-dating and crater morphometry to detail a previously-unidentified path of putative plume migration. Our results indicate that extensive volcanic resurfacing occurred from a location near the present south pole to the equator around 3.8 billion years ago, obliterating older cratered terrains. The resurfacing path is manifest as smooth volcanic plains embaying ancient massifs and infilling large impact craters as well as a lack of a magnetic signature in this portion of the crust. Our results have significant ramifications for mantle dynamics and the early geologic history of Mars.