Lunar glasses are characterized by complex origin (i.e., volcanism or impact), compositional diversity (e.g., picritic, basaltic, or feldspathic), and visible/near-infrared spectra similarity. This makes it is problematic to distinguish different types of lunar glasses in laboratory and remote data. In this study, we present micro-FTIR (Fourier Transform Infrared) spectroscopy spectra (550-1450 cm(-1)) of a suite of lunar volcanic origin glasses (i.e., pyroclastic glasses) and impact-generated glasses (i.e., mare and highland impact glasses), identified in lunar breccia meteorite Northwest Africa 7948. The results show that lunar pyroclastic glasses, mare impact glasses, and highland impact glasses exhibit different FTIR spectral characteristics: (1) the Christiansen Feature positions of pyroclastic glasses are generally at a longer wavelength (i.e., >similar to 8.3 mu m equivalent to <similar to 1,205 cm(-1)) than the spectra of mare and highland impact-generated glasses (i.e., similar to 1,205 cm(-1)); (2) a relatively strong minor peak was distinctly observed at longer wavelength (similar to 13.5-16.5 mu m equivalent to similar to 600-750 cm(-1)) for highland impact glasses. Therefore, new supplementary FTIR diagnostic criteria were proposed to discern different types of lunar glasses. Our studies demonstrated that midinfrared spectra could provide an effective tool to non-destructively and quickly distinguish lunar glasses in laboratory (e.g., for the future Chang'E-5 returned soils).

Plain Language Summary Lunar surface soils commonly contain a wide range of glass components derived from volcanic eruptions and/or impact events, which are difficult to distinguish via visible/near-infrared spectra. We characterized a suite of volcanic origin glasses (i.e., pyroclastic glasses) and impact-generated glasses (i.e., mare and highland impact glasses) from lunar breccia meteorite Northwest Africa 7948 using scanning electron microscope, Electron Probe Micro-Analyser, and micro-Fourier Transform Infrared (FTIR) techniques. The results revealed that the pyroclastic and impact glasses display varying FTIR spectral features. We therefore propose a new supplementary diagnostic FTIR criterion to help to discern different types of lunar glasses. Our results show that FTIR spectra of lunar glasses would enable us to distinguish different types of glass components.