An investigation of potential pyroclastic deposits on the southeast limb of the Moon

We investigated the physical and spectral properties of potential dark mantling deposits (PDMDs) previously and newly identified on the SE limb of the Moon, near the craters Humboldt and Petavius. The goals of this investigation were to constrain the composition and mode of emplacement of these poorly studied deposits, to identify interdeposit variations, and to use these results to draw conclusions about regional and subsurface geologic processes. Our investigation involved an assessment of both the physical properties (size, texture, morphology) and spectral properties (albedo, absorption bands, color ratios) utilizing remote sensing data from multiple lunar orbital missions. We found that many of the SE Limb deposits previously identified as possibly pyroclastic in origin were likely effusively emplaced. However, we also identified several likely pyroclastic deposits, including three not previously mapped. We found that the volcanic deposits across the study area comprise three major spectral groups: one similar to Mare Fecunditatis, one similar to Mare Australe, and one similar to known glassy pyroclastic deposits elsewhere on the Moon. We conclude that volcanism across the SE limb was likely fed from at least two distinct magma source regions, and that the type and extent of surface expression of this volcanic activity was possibly influenced by regional variations in crustal thickness. Our documentation and analysis of the complex volcanic history in this region of the Moon supports ongoing efforts to develop increasingly detailed interpretations of the volcanic history of the entire Moon.