The Schrödinger basin on the lunar farside is ∼320 km in diameter and the best-preserved peak-ring basin of its size in the Earth–Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K–T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-agency International Space Exploration Coordination Group.

The diameter range of 15 to 20 km is within the transition from simple to complex impact craters located on the Moon. This range spans roughly a factor of 3 in impact energy for the same impactor speed, composition, and trajectory angle. We analyzed the global population of well‐preserved craters in this size range in order to assess the effects of target and impactor properties on crater shapes and morphologies. We observed that within this narrow diameter range, simple craters are confined to the highlands, and complex craters are more abundant in the mare. We found unusually deep craters around the highlands‐mare boundaries and favor the hypothesis that they form by impact cratering on high‐porosity terrain. We infer that target properties primarily contribute to the observed morphological variations in the craters. Simple crater formation is favored by a terrain that is more homogeneous in strength and topography, while transitional and complex crater formation is aided by heterogeneity in lithology, topography, or strength, or a combination of these parameters. Clearly visible impact melt deposits in a small percentage of simple craters, and two cases of craters differing in morphologies from their nearest neighbors in similar geologic settings, suggest that variation in impactor properties such as impact velocity and impactor size may have some role in causing morphological differences between similar‐sized craters.

From a group of well‐preserved lunar simple craters in the 15‐ to 20‐km diameter range and with the help of Lunar Orbiter Laser Altimeter topography data, we identified a subset of eight deep craters (depth/diameter ratio > 0.20). These craters are in the regions around the mare‐highlands boundaries, which are characterized as having the highest porosity on the lunar surface. To understand the cratering mechanics behind the formation of these craters, a geologic investigation of the terrains of these craters was performed. We evaluated the depth/diameter ratios of smaller simple craters surrounding several 15‐ to 20‐km diameter craters, analyzed the morphometry of the craters, and visually examined the cavities using multiple data sets. We conclude that deep transient cavities were formed from compaction of porous target material. The result was a deeper than normal simple crater without an identifiable increase in the volume of excavated material, as inferred from the craters' rim heights and shapes. While all of these craters formed in areas of high porosity, not all craters in high‐porosity regions are deep. It may be that some unusual impactor property is also required to produce a deep crater, such as a high velocity impact, a near‐vertical impact, or a dense impactor that yielded a large penetration depth.