The role of pre-existing faults and fractures in shaping polygonal impact craters and its tectonic implications in the southern Margaritifer Terra region, Mars

Abstract

The presence of polygonal-shaped craters, i.e., craters with complete or incomplete polygonal rims along with circular or elliptical outlines, on the surface of celestial bodies has been known for nearly a century. However, many investigations on their distribution and formation have not been carried out, until recently. Scientists have proposed that the polygonal shapes of the crater rims owe their origin to the pre-existing structurally weak planes like faults/fractures in the area adjacent to the impact. The present study area is the southern part of Margaritifer Terra, Mars; a mid-Noachian terrain, which has craters of different morphologies, including the polygonal impact craters (PICs). The study focuses on the reason for the development of PICs by identification and mapping of a population of 50 selected polygonal craters along with morphotectonic features namely grabens, wrinkle ridges, and lobate scarps. The analysis of orientations of the straight segments of polygonal crater rims shows marked resemblance with orientations of these morphotectonic features conforming to their control on the rim geometries.