Potential bedrock exposures of Schrödinger impact melt sheet and/or polymict impact breccias within a crater floor fracture system and volcanic vent

Abstract

The Schrödinger impact basin provides significant geological targets for future exploration, including impact melts, multi-kilometer-long exposures of magmatic rocks from deep within the lunar crust, volcanic mare, pyroclastic ash deposits, potentially with mantle xenoliths, and a geophysical setting for examining the near-rim structure of the South Pole-Aitken mega-basin. Surveyor, Ranger, and Apollo programs confirmed that constant gardening of the lunar surface by impact cratering processes reduces the availability of outcrops, which are those key bedrock exposures that geologists on Earth use as the most reliable sources of information about planetary evolution. Lunar Reconnaissance Orbiter Camera (LROC) images of the lunar surface are providing data needed to identify bedrock exposures on the Moon, and tracked boulders leading to rock exposures, in locations suitable for future exploration. One such rocky exposure occurs within a volcanic vent within the Schrödinger impact basin. We consider six working hypotheses for its origin and conclude it likely represents a bedrock exposure of impact melt and/or impact breccia produced by the Schrödinger impact event or, alternatively, pristine lava rock associated with the vent's pyroclastic origin. While elsewhere in the basin those units are covered with regolith and younger volcanic deposits, the opening of a crater floor fracture and pyroclastic eruption of volcanic material cleared a vertical exposure through the impact or eruptive lithologies, which remain accessible for exploration today.