Sample-based Spectral Mapping around Landing Sites on the Moon—Lunar Timescale Part 1

Abstract

Studying the geology of a terrestrial body and its evolution requires being able to set up a chronology. Crater statistics is a powerful tool to do so. However, calibration of this method, which is derived on the Moon, requires properly defined geological units, large enough for reliable crater statistics, and dated samples representative of these geological units. Yet, little effort has been put into choosing a representative set of lunar mission units and samples based on spectral information. Therefore, accuracy and precision of so-called cratering-chronology models remain limited. Here, we analyzed near-infrared orbital data to suggest a geological unit as a reference unit for Apollo 11, 12, 14-17 and Luna 16, 20, and 24 landing sites. We used near-infrared spectral information from orbital data and laboratory measurements to identify the set of samples that is the most representative of the landing-site reference units. We now provide spectrally constrained reference units, for which crater frequencies can be derived, and our sample recommendation will assign the reference age for updating the currently existing cratering-chronology models. We highlight that determining a reference geological unit in the highlands of the Moon is challenging because of the very nature of the terrain, while it is more straightforward for mare units. However, ejecta presence on these mare units comprises solvable challenges.