Martian plate tectonics

Abstract. The northern lowlands of Mars may have been produced by plate tectonics. Preexisting old thick highland crust was subducted, while seafloor spreading produced thin lowland crust during Late Noachian and Early Hesperian time. In the preferred reconstruction, a breakup margin extended north of Cimmeria Terra between Daedalia Planum and Isidis Planitia where the highland-lowland transition is relatively simple. South dipping subduction occurred beneath Arabia Terra and east dipping subduction beneath Thatsis Montes and Tempe Terra. Lineations associated with Gordii Dotsum are attributed to ridge-parallel structures, while Phelegra Montes and Scandia Colles are interpreted as transform-parallel structures or ridge-fault-fault triple junction tracks. Other than for these few features, there is little topographic roughness in the lowlands. Seafloor spreading, if it occurred, must have been relatively rapid. Quantitative estimates of spreading rate are obtained by considering the physics of seafloor spreading in the lower C 0.4 g) gravity of Mars, the absence of vertical scarps from age differences across fracture zones, and the smooth axial topography. To the first order, the height of vertical scarps across fracture zones does not involve gravity. Crustal thickness at a given potential temperature in the mantle source region scales inversely wit