Pre-Orientale Southwest Peak-Ring Basin: Gravity Structure, Geologic Characteristics, and Influence on Orientale Basin Ring Formation and Ejecta Emplacement

The Orientale impact basin is the youngest and most well-preserved of lunar multi-ring basins. generally ring structures facies are distinctly anomalous in southwestern quadrant; outer Cordillera extends significantly outward, Outer Inner Rook mountain rings more poorly developed show characteristics, Montes Formation varies widely from its characteristics elsewhere interior. Based on gravity, image, topography data, we confirmed that southwest region represents location a pre-existing ~320 km rim–crest diameter peak–ring centered at 108.8°W, 28.4°S, characterized by an ~170 diameter. We model structure morphology this large pre-Orientale (about one-third Orientale) presence negative relief had distinctive influence development (disrupting otherwise circular continuity causing radial excursions their locations) emplacement ejecta (causing filling low represented basin, creating surface textures, resulting late stage movement response to topography. preservation Bouguer anomaly strongly suggest rim crest excavation cavity lies or within Mountain ring.