Photogeologic analysis of impact melt‐rich lithologies in Kepler crater that could be sampled by future missions

Abstract

Kepler is a 31 km diameter Copernican age complex impact crater located on the nearside maria of the Moon. We used Lunar Reconnaissance Orbiter imagery and topographic data in combination with Kaguya terrain camera and other image data sets to construct a new geomorphologic sketch map of the Kepler crater, with a focus on impact melt‐rich lithologies. Most of the interior melt rocks are preserved in smooth and hummocky floor materials. Smaller volumes of impact melt were deposited in rim veneer, interior and exterior ponds, and lobe‐like overlapping flows on the upper crater wall. Based on shadow lengths, typical flows of melt‐rich material on crater walls and the western rim flank are ∼1–5 m thick, and have yield strengths of ∼1–10 kPa. The melt rock distribution is notably asymmetric, with interior and exterior melt‐rich deposits concentrated north and west of the crater center. This melt distribution and the similarly asymmetric ray distribution imply a slightly less than 45° impact trajectory from the southeast. The exposed wall of Kepler displays distinct layering, with individual layers having typical thicknesses of ∼3–5 m. These are interpreted as flows of Procellarum mare basalts in the impact target. From the point of view of exploration, numerous fractures and pits in the melt‐rich floor materials not only enable detailed studies of melt‐related processes of impact crater formation, but also provide potential shelters for longer duration manned lunar missions.