The Rise and Fall of Crustal Porosity: Insight on Early Martian History

Abstract

Beneath the late InSight Mars lander, the seismic wave speed at depth sharply increases at two intra-crustal boundaries [1-5]. This indicates the crust below InSight contains three separate layers with distinct compositions and/or porosities. Differences in composition might suggest differences in the timing or mechanism behind each layer’s formation, while differences in porosity may arise from the closure or generation of porosity at depth. We focus on the latter and ask what the depth of such porosity transitions would suggest about early Martian history—namely by investigating the closure of porosity through viscous creep and the generation of porosity by impact-induced tensile fragmentation.