Mercury's Crustal Thickness and Contractional Strain

Abstract

The crust of Mercury has experienced contraction on a global scale. Contractional deformation is expressed by a broadly distributed network of lobate thrust fault scarps. The most likely principal source of stress is global contraction from cooling of Mercury's interior. Global contraction alone would be expected to result in a uniformly distributed population of thrust faults. Mercury's fault scarps, however, often occur in long, linear clusters or bands. An analysis of the contractional strain as a function of crustal thickness, estimated in two crustal thickness models (CT1 and CT2) derived from gravity and topography data obtained during the MESSENGER mission, indicates the greatest contractional strain occurs in crust 50–60 km thick. On Earth, mantle downwelling can thicken and compress overlying crust, regionally concentrating thrust faults. Clusters of lobate scarps collocated with regions of thick crust suggest downward mantle flow contributed to the localization of lithosphere-penetrating thrust faults.