Recently, possible exceptionally young mare volcanic glass beads were discovered in Chang'e-5 (CE-5) samples. Isotopic dating suggests an age of approximately 120 Ma, presenting new challenges to existing lunar thermal evolution models. Thus, our research focuses on the source region of Rima Mairan, a branch of Rima Sharp, and its surrounding area, located southeast of the CE-5 landing site. In this area, numerous small irregular mare patches (IMPs) were identified and analyzed to explore their formation timing and possible origins. To investigate the debated formation ages of IMPs (<100 Ma or >3.5 Ga), we carried out statistical, classification, morphological, and chronological analyses and find: (a) Approximately 75% of small IMPs are located within or along crater rims (50–500 m in diameter). (b) Morphological measurements and diffusion modeling estimate the ages of these craters from 2 Ga to the present, indicating a gradual, time-variable formation process rather than a single event. (c) Surface features such as lobate contacts, limited thickness (～6 m), and compositional similarities to CE-5 basalts imply that they were likely influenced by late-stage localized magmatic or thermal processes after 2 Ga. However, their final morphology may also record modification using non-volcanic processes such as collapse, regolith redistribution, or seismic activity. These findings reveal complex resurfacing processes possibly sustained by localized thermal anomalies, suggesting that geological activity persisted longer than previously thought. Further high-resolution imaging and in situ analyses are needed to clarify IMP origins, evaluate their relationship to CE-5 materials, and refine models of late-stage lunar thermal evolution.

Article link: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JE009017