¹Shuai Li, ^2,3,4Daniel P. Moriarty III, ⁵Carle M. Pieters, ⁶Rachel L. Klima, ⁶Angela M. Dapremont
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116668]
¹Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI, USA
²NASA Goddard Space Flight Center, Greenbelt, MD, USA
³Department of Astronomy, University of Maryland, College Park, MD, USA
⁴Center for Research and Exploration in Space Science & Technology II, University of Maryland, College Park, MD, USA
⁵Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
⁶Johns Hopkins University Applied Physics Laboratory (JHUAPL), Laurel, MD, USA
Copyright ELsevier

This study presents high-resolution (140 m/pixel) controlled mosaics of Moon Mineralogy Mapper (M3) data in the lunar polar regions (80°–90° N/S), with a focus on assessing mineralogy and water content across the Artemis exploration zone. M3 extensively sampled the lunar polar regions, providing a high spatial resolution, hyperspectral imaging dataset that uniquely covers reflectance absorptions of major minerals and water on the lunar surface. We developed a methodology to preferentially use M3 image cubes acquired when the star tracker was operational to ensure accurate spatial registration of M3 pixels in our new mosaics. Integrated band depth (IBD) analyses were conducted to map distributions of hematite and other mineral species at the Artemis exploration zone. We also derived water contents at the Artemis sites from our new M3 mosaics. Our findings indicate that the Artemis exploration zone is largely dominated by mature regolith that is probably rich in plagioclase. Hematite is predominantly concentrated on east-facing slopes, likely due to enhanced oxidation from Earth wind oxygen interacting with the lunar regolith. Pyroxene-rich exposures are observed in three Artemis candidate landing regions and they are all associated with fresh impact craters. The water distribution is highly variable, with higher concentrations on pole-facing slopes and near permanently shadowed regions, likely controlled by low surface temperatures. High water contents are observed at hematite exposures, which reinforces that water may play a crucial role in hematite formation on the Moon. These results provide valuable insights for future lunar exploration, aiding in the selection of landing sites, planning of traverse routes, and informing in situ resource utilization (ISRU) for the Artemis missions.

^1,2,3Kengo T.M. Ito, ¹Sota Niki, ⁴Hikaru Hasegawa, ¹Kanoko Kurihara, ²Tokiyuki Morohoshi, ⁴Takashi Mikouchi, ¹Takafumi Hirata, ⁵Martin Bizzarro, ²Tsuyoshi Iizuka
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.05.022]
¹Geochemical Research Center, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
²Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
³Division of Sustainable Energy and Environmental Engineering, The University of Osaka, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
⁴The University Museum, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
⁵Center for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
Copyright Elsevier

Brachinites are a group of primitive achondrites composed mostly of ferroan olivine, which may have formed as partial melting residues or cumulates on an incompletely differentiated planetesimal. To constrain the petrogenetic origin of brachinites and the thermal history of the parent body, we report the first study that integrates mineralogical, rare earth element (REE), and U–Pb age data for brachinite Ca-phosphates, apatite and merrillite, using very coarse grains up to ∼ 500 µm in diameter found in Northwest Africa 10932. The mineralogical data reveal partial replacement of apatite by merrillite concurrent with the reaction of olivine and a S-rich vapor to form symplectitic clinopyroxene-troilite/Fe-Ni metal intergrowths during thermal metamorphism. Apatite cores surrounded by merrillite rims exhibit REE zoning resulting from diffusion during metamorphism. Diffusion modeling of the REE zoning using the olivine-chromite equilibration temperature of 978 ± 11 ˚C constrains the duration of the metamorphism to be 104 yr. This timescale is far longer than that of shock metamorphism, and therefore requires an internal heat source such as adjacent magma. The apatite cores and merrillite rims yielded identical U–Pb ages of 4482 ± 29 Ma (2σ) reflecting complete resetting of the U–Pb system during metamorphism. This metamorphic age is distinctly younger than the Mn–Cr age of 4565 Ma reported for the Brachina meteorite, revealing indigenous thermal activity over ∼ 80 Myr on the parent body. Reconciling the protracted thermal activity with the primitive brachinite composition suggests that brachinites were derived from a moderately shallow region of the parent body, whose interior was differentiated into a core and mantle. Moreover, the metamorphic age is identical to the reported U–Pb age of apatite in the andesitic meteorites Graves Nunataks 06128 and 06129 [4460 ± 30 Ma (2σ)]. This correspondence supports the hypothesis that the andesitic meteorites are samples of partial melts extracted from the ultramafic residues represented by brachinites and further suggests that the transformation from apatite to merrillite in the brachinite source region released a metasomatic Cl-rich fluid to form chlorapatite in the shallower crustal region.