¹Xiaoying Liu, ¹Chi Zhang, ¹Zongyu Yue, ¹Lixin Gu, ¹Jing Li, ¹Heng-Ci Tian, ¹Sen Hu, ¹Yangting Lin
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.116969]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Copyright Elsevier

Meteorite impact is a key process on the Moon, having profoundly reshaped the lunar surface, modified the physical properties of lunar regolith, and transported water and other volatiles on the surface. However, the temperature-pressure conditions of impact-induced plumes and their duration were poorly constrained. Here, we report the first discovery of immiscibility a FeNi-P-S bead from Chang’e-5 lunar soils, which consists of abundant spherules of metallic FeNi and sulfide both evenly dispersed in phosphide-rich matrix. The observed texture and compositions are consistent with quenching of an FeNi-P-S melt droplet, generated during an iron meteorite impact. The initial droplet was homogeneous and formed at >1800 °C and > 11–16 GPa within the impact plume, based on high-pressure experiments of the Fe-P-S system. As the plume expanding, FeNi spherules emerged from the droplet at 11–16 GPa, estimated by P partitioning between the metal and P-S-rich melt. Subsequent separation of the P-S-rich melt into immiscible sulfide-rich spherules and phosphide-rich mesostasis occurred at 1 bar–3 GPa and 1000–1100 °C. The duration of the pressure declining from >11–16 GPa to 1 bar–3 GPa was estimated to be 0.5–1 s, combining the impact plume expansion model with the cooling rate inferred from the metallic bead. This study demonstrates that high-pressure conditions of impact plumes can be retained for second timescales, which is critical for chemical reactions and water and other volatile migration on the Moon’s surface.

¹Edward A. Cloutis et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.116952]
¹Centre for Terrestrial and Planetary Exploration, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB R3B 2E9, Canada
Copyright Elsevier

Four carbonaceous chondrite (CC) meteorites – MET 00432, Tagish Lake, Tarda, and WIS 91600 – have been proposed to be members of a CC grouplet, hereafter termed the Carbonaceous Tagish Lake Grouplet (CTG). We investigated their possible affinities via a spectral reflectance-focused study of them, as chips and variously sized powders. We also considered possible spectrum-altering effects of space weathering and composition of the organic component on such red-sloped spectra. Ultraviolet-region spectra (200-400 nm) exhibit absorption features attributable to unspecific Fe2+-O and/or Fe3+-O charge transfers, possibly due to Fe-rich phyllosilicates. Both albedo and spectral slope vary as a function of grain size. The 0.35-2.50 μm interval is characterized by dark, variably red-sloped spectra with low albedos in the visible region (<6% reflectance at 0.550 μm). Spectral slopes are redder for powders than slabs or chips. CTG spectra also exhibit shallow (<4% deep) absorption bands attributable to known components, such as magnetite and phyllosilicates, particularly in the 1 μm region. Spectral analysis of an extensive suite of phyllosilicate+opaque mixtures suggests that only a subset of CTG opaque components can cause darkening and overall red spectral slopes, in particular low H/C ratio carbonaceous compounds. Other opaque components, such as iron sulfides, magnetite and other carbonaceous materials, some of which are red-sloped when pure, cause spectral bluing or only slight spectral reddening. Albedo and spectral slopes and shapes are affected by physical properties, such as grain size, as well as the types, compositions, abundances, dispersion, and grain sizes of opaque components. At longer wavelengths (to 14 μm), CTG spectra exhibit a number of absorption features that can be related to their silicate, carbonate, and organic components. A prominent absorption feature is present in the 2.7-3.1 μm region attributable to phyllosilicates ± H2O, some of which is likely attributable to terrestrial alteration. Petrological, mineralogical, and isotopic information provide support for these meteorites having strong affinities to each other and comprising a grouplet. Additional CTG meteorites may lurk among the many tens of CCs that have been incompletely characterized.