^1,2Yiheng Dai,^1,2Zhiheng Xie,^1,2Zezhou Li,^2,3Tianyi Jia,^2,3Ruimin Wang,⁴Zongjun Yin,^2,3Bing Shen,^1,2Jihan Zhou
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE009028]
¹Beijing National Laboratory for Molecular Sciences, Center for Integrated Spectroscopy, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
²Research Institute of Extraterrestrial Material at Peking University (RIEMPKU), Beijing, China
³Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, China
⁴State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
Published by arrangement with John Wiley & Sons

Meteoroid impacts, a key process of space weathering, significantly alter the structures, compositions and properties of lunar regolith. However, the phase separation phenomena, common in lunar regolith and induced by impact, remain poorly understood. This uncertainty arises from the structural complexity and the scarcity of identified impact-induced phase separation features. Here we report the impact-induced formation of chemically distinct amorphous silicate nanodroplets, including iron-rich droplets within a silicon-rich glass matrix and vice versa, on the surface of a Chang’e-5 lunar regolith grain. These nanodroplets are partially ripened aggregates, and their formation is attributed to metastable liquid immiscibility driven by local chemical heterogeneities and rapid quenching. Additionally, troilite-kamacite remnants and skeletal crystallites of ilmenite and apatite provide direct evidence of impact and fast post-impact quenching, respectively. These findings suggest that quenched impact melts in airless bodies can undergo unmixing, forming immiscible conjugated nanodroplets, and exhibiting diverse behaviors under specific post-impact conditions.

¹Xue Su,¹Youxue Zhang,²Yang Liu,¹Robert M. Holder
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009027]
¹Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

Volcanic glass beads on the Moon have traditionally been thought to only record volatile loss during pyroclastic eruptions. However, recent discoveries have shown that lunar orange glass beads, representing primitive high-Ti basalts, experienced both outgassing and in-gassing of volatile elements such as Na, K, Cu, and S. In this work, we examine lunar green glass beads from samples 15421 and 15366, representing primitive very-low-Ti basalts, for the distribution of Na, K and Cu using EMP analyses and LA-ICP-MS mapping. It is found that all studied lunar green beads show increased Na, K and Cu concentrations near the bead surfaces, indicative of in-gassing. A quantitative model was developed to simulate the concentration evolution of Na and Cu in individual green glass beads during eruption and cooling. The presence of similar in-gassing diffusion profiles of volatile elements in beads from different eruptions indicates a common behavior of lunar volcanic gas. In addition to volatile in-gassing, LA-ICP-MS mapping of Na and K in one green bead from sample 15366 shows features suggesting collision of melt droplets during the fire-fountain eruption, revealing more details in the dynamic aspects of lunar fire-fountain eruptions. Compared to orange glass beads, the varying boundary conditions of green glass beads during formation may suggest that their eruption plume evolved and dissipated more rapidly, potentially linked to changes in the global lunar atmosphere.