The origin of hierarchical cracks in floor-fractured craters on Mars and the Moon

Abstract

Numerous craters showing floor fractures have been identified on the Moon and Mars. Whereas on the Moon, the floor morphology, crater geology and fracture characteristics suggest that the floor deformation is caused by underlying magmatic intrusions, the origin of fractures and floor modifications of Martian floor-fractured craters (FFCs) remains debated. Here, we focus on FFCs displaying hierarchical crack patterns. We use different quantitative fracture characteristics to investigate the physical processes at the origin of cracks and compare their variations to scaling laws derived theoretically and from desiccating laboratory experiments. We show that cracks on a large set of Martian FFCs close to Valles Marineris differ from that of Lunar FFCs: they may be explained by tensile stresses caused by the shrinkage of a material adhering on the crater floor, similar to desiccating cracks. Other Martian FFCs close to Syrtis Major show cracks more similar to those caused by a magmatic intrusion.