the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Feb 2026
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.
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Status: open (until 06 Apr 2026)
- RC1: 'Comment on egusphere-2026-876', Benjamin Bultel, 19 Mar 2026 reply
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The manuscript (MS) « Spectral analyses of lunar regions observed by MAJIS during the JUICE Earth-Moon flyby» by Francesca Zambon and collaborators reports on the MAJIS opportunity of Moon observations during a flyby. This work demonstrates the potential of MAJIS to characterise both the Moon and Jovian moons' surfaces. I have a few minor comments detailed below. First, about the ratioing method used. Second, about the figures and their clarity. Third, about the comparison between the MAJIS results and those from other instruments.
Ratioing method:
This method is not often used on the Moon (not systematically as for Mars). Dust is less of a problem since the regolith is mainly produced by microbombardment and is representative of the rock just below. There is also less instrumental artefact systematically present at a given spectral window (nothing like the 1.6µm artefact on CRISM data for example). Could the authors clarify how they checked that the “signal” removed by ratioing is mainly noise? Is there, for instance, a visual inspection of the denominator spectrum?
The ratioing method appears to work very well to suppress the 1.3 µm artefact. I wonder whether this also implies that detecting feldspar-rich surfaces or glassy materials will become significantly more difficult when using this approach. A short comment on this potential limitation would be helpful.
Figures:
Figure 5: could be improved by adding numbers to each spectrum and region, as it is difficult to see them in the figures. Also, maybe stack the spectra in panel b so they're clearer to see.
Figure 7: in Fig7a, the southeast seems to be very noisy. Maybe the threshold for detection of a band (stretching)could be modified to make this better? Using a different figure for Mare vs Highland to show a different range of values could give a better idea of the differences between these two areas.
Comparison to other datasets:
This is an excellent idea. This comparison is done on maps only, and they are difficult to read as is. The trend seems to be confirmed, but this is a very rough estimation. For instance, a more direct comparison between MAJIS and M3/Kaguya or Clementine in specific regions (e.g., between Figures 11 and 13a) could strengthen the discussion. Alternatively, as specific craters have been targeted with the MAJIS data, what about comparing directly with the M3 or Kaguya Spectral Profiler spectra to illustrate the differences more concretely? If such a comparison is not feasible, a brief explanation of the limitations would be useful.