Morphologic and structural mapping of the central uplift of Betio Crater, Thaumasia Planum, Mars

The approximately 31.7-km-diameter Betio crater (23.15 degrees S, 281.38 degrees E), located within the Hesperian-aged Ridged Plains material in Thaumasia Planum, Mars, contains a well-preserved asymmetrical central floor pit ( approximately 10.8 km NW-SE and approximately 8.8 km NE-SW in diameter) covering an area of approximately 67 km (super 2) that exposes discrete megablocks of layered bedrock and preserves a variety of impact-generated deposits. High-resolution images taken by the Mars Reconnaissance Orbiter (MRO) are combined with other data sets to study and map the morphology and structure of the central floor pit. The excellent bedrock exposure of the floor pit enables the comparison of mapped structures with observations from terrestrial craters. Our mapping of the central uplift has revealed a variety of faults, folds (likely radial transpression ridges), and many breccia dikes, in addition to different types of impactites (e.g., breccias, impact melt deposits, and uplifted bedrock [i.e., parautochthonous bedrock]). Through structural mapping, we show that the central portion of the central uplift is characterized by smaller ( approximately 60-300 m in diameter) blocks with high dips of approximately 45 degrees -85 degrees , and the outer sections of the floor pit have larger (>800 m in diameter) blocks with shallow dip angles of approximately 5 degrees -15 degrees . Our work shows that extensive brittle deformation and brecciation increase toward the center of the crater and particularly in the SW sector of the central pit. There is also an overall decrease in block size toward the center of the crater.