Spectral analyzes of lunar regions observed by MAJIS during the JUICE Earth-Moon flyby

Abstract. The Moons and Jupiter Imaging Spectrometer (MAJIS) instrument onboard the ESA Jupiter Icy Moon Explorer (JUICE) mission acquired the first hyperspectral data of the lunar surface since Chandrayaan-1/Moon Mineralogy Mapper (M³), Cassini/VIMS, and the more recent Chandrayaan-2/Imaging Infrared Spectrometer (IIRS). In this study, we present a mineralogical and spectral analysis of a portion of the lunar nearside, including Mare Tranquillitatis, Mare Fecunditatis, and adjacent highland terrains, as observed by MAJIS. Due to high-phase and high-incidence illumination conditions, our analysis primarily focuses on two specific MAJIS observations. MAJIS spectra reveal prominent absorption features near 1 and 2 μm, indicative of both low- and high-calcium pyroxenes, confirming the dominance of mafic minerals—particularly in mare regions and fresh impact craters along with associated ejecta, such as those from Maskelyne G and Messier/Messier A. These areas are characterised by deeper absorption bands compared to surrounding terrains. Variations in spectral slopes are also observed and are associated with both surface maturity and compositional differences, consistent with the spectral characteristics of the observed regions retrieved by previous instruments. We apply thermal emission correction to investigate potential features above 2.6 μm, to discriminate possible absorption bands in the MAJIS infrared spectral range. Nevertheless, further work is required to fully explore this spectral range. Finally, comparison with datasets from previous missions demonstrates strong consistency in derived spectral parameters, validating the performance of MAJIS for lunar mineralogical studies. These findings highlight MAJIS’ capability to characterise both composition and maturity of the lunar surface, while also emphasising its potential for future investigations in the Jovian system.