269-2 Reinterpretation of the Apollo 16 Landing Site: Geologic Mapping and Sample Analysis

Session: Planetary Geologic Mapping Across the Solar System (Posters)

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Abstract:

The Apollo 16 landing site represents the only highlands-dominated, human-sampled region on the Moon. A major outstanding question is the origin of mafic materials found amidst the sample collection. Here, we have remapped the geology of the Apollo 16 landing site using new orbital data to provide additional insights into the provenance of impact and proximal basin-derived materials. 

An intermediate-scale, 1:250,000, geologic map has been completed for the Apollo 16 landing site region. The locations of 304 returned Apollo 16 samples, with attached geochemical data from previous studies, are being used to interpret the updated geologic units and to analyze the distribution of mafic mare material (interpreted as forming exogenously) and other impact-derived material found throughout the Apollo 16 stations. 

The following compositional criteria are used to identify mafic materials found at the Apollo 16 landing site: TiO2 > 2%; MgO > 11%; CaO/Al2O3 > 0.75; or MgO/Al2O3 > 1.25 (Delano, 1986; Korotev, 1994; Korotev et al., 2010; Ziegler et al., 2006). Of the 304 samples used in this study, 37 of them are identified as mafic materials, seven of which have two or more mafic identifiers. These samples were taken from Apollo 16 stations 6, 2, 5, 13, 11, 4, and 10 (in ascending order of the quantity of mafic samples found at each site). Stations 11, 13, 10, 6, 5, and 4 occur in a line that is oriented NNW to SSE. This linear orientation could indicate that the mafic materials were emplaced from the Imbrium impact, which is located NW of the landing site. Stations 4, 5, and 6 are directly west of the Nectaris basin and could be ejecta from that impact. Studying the mafic materials found in highland terrain is important for understanding the distribution of exogenous material across the lunar surface. This research provides a more comprehensive geological picture of the Apollo 16 landing site, constrains the potential origin of exogenous material within the highlands, and informs us about the process of impact transport across the lunar surface. The resulting data will be relevant for future missions that visit and sample the lunar highlands. 

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10249

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