Global picture of lunar basalt chronology based on the automatic classification of craters

One major pathway for studying lunar volcanism evolution is to construct a timeline for the emplacement of basalts. The crater size-frequency distribution is a pivotal method for dating lunar surface basalt units. Building upon two previously published lunar impact crater databases (diameters ≥1–2 km), this study integrated these databases and corrected for latitudinal distortions in crater morphology due to map projection. By utilizing morphological properties such as eccentricity, the depth-to-diameter ratio, and local spatial density, an automated classification model was constructed using the support vector machine method to distinguish primary craters from secondary craters superposed on specific geological units in the integrated0 lunar crater database. After correcting for the spatial variability in lunar impact cratering rates, global chronological maps of both maria and cryptomaria on the Moon were generated. The maps indicate that areas southwest of the Aristarchus plateau within the Oceanus Procellarum have the youngest geologic units, with model ages of ~1.5 Ga. The majority of young lunar mare basalts (<3.0 Ga) are located in northern Oceanus Procellarum, western Imbrium, southern Serenitatis, and the Procellarum-Insularum junction. The oldest mare basalts, with model ages >3.5 Ga, are located in Maria Tranquillitatis, Nectaris, and Fecunditatis. The model age of the southern mare unit in the Apollo Basin where Chang’e-6 landed, is also in alignment with the radioisotopic ages determined by the recently returned Chang’e-6 basalt samples. Finally, utilizing these newly updated chronological maps, the temporal variation in lunar basaltic eruption volumes is discussed.