Vapor-deposited digenite in Chang'e-5 lunar soil.

Frequent impacts on the Moon have changed the physical and chemical properties of the lunar regolith, with new materials deposited from the impact-induced vapor phase. Here, we combined nanoscale chemical and structural analysis to identify the mineral digenite (4Cu2S·CuS) in Chang'e-5 lunar soil. This is the first report of digenite in a lunar sample. The surface-correlated digenite phase is undifferentiated in distribution and compositionally distinct from its hosts, suggesting that it originated from vapor-phase deposition. The presence of an Al-rich impact glass bead suggests that a thermal effect provided by impact ejecta is the main heat source for the evaporation of Cu-S components from a cupriferous troilite precursor, and the digenite condensed from these Cu-S vapors. A large pure metallic iron (Fe0) particle and high Cu content within the studied Cu-Fe-S grain suggest that this grain was most likely derived from a highly differentiated and reduced melt.

Guo Z ，Li C ，Li Y ，Wu Y ，Zhu C ，Wen Y ，Fa W ，Li X ，Liu J ，Ouyang Z ... -  《-》

Sub-microscopic magnetite and metallic iron particles formed by eutectic reaction in Chang'E-5 lunar soil.

Ferric iron as well as magnetite are rarely found in lunar samples, and their distribution and formation mechanisms on the Moon have not been well studied. Here, we discover sub-microscopic magnetite particles in Chang'E-5 lunar soil. Magnetite and pure metallic iron particles are embedded in oxygen-dissolved iron-sulfide grains from the Chang'E-5 samples. This mineral assemblage indicates a FeO eutectoid reaction (4FeO = Fe3O4 + Fe) for formation of magnetite. The iron-sulfide grains' morphology features and the oxygen's distribution suggest that a gas-melt phase reaction occurred during large-impact events. This could provide an effective method to form ubiquitous sub-microscopic magnetite in fine lunar soils and be a contributor to the presentation of ferric iron on the surface of the Moon. Additionally, the formation of sub-microscopic magnetite and metallic iron by eutectoid reaction may provide an alternative way for the formation of magnetic anomalies observed on the Moon.

Guo Z ，Li C ，Li Y ，Wen Y ，Wu Y ，Jia B ，Tai K ，Zeng X ，Li X ，Liu J ，Ouyang Z ... -  《Nature Communications》

First classification of iron meteorite fragment preserved in Chang'e-5 lunar soils.

Liu X ，Gu L ，Tian HC ，Li J ，Tang X ，Hu S ，Lin Y ... -  《-》

Redox condition changes caused by impacts: Insights from Chang'e-5 lunar glass beads.

Lunar materials are overall more reducing compared with their terrestrial counterparts, but the mechanism remains to be elucidated. In this study, we present a possible explanation for the changes in redox state of the lunar regolith caused by impact events, based on our investigations of the impact glass beads from Chang'e-5 mission. These glass beads contain iron metal grains and show concentration gradients of FeO and K2O (with or without Na2O) from their rims to centers. The compositional profiles exhibit error-function-like shapes, which indicates a diffusion-limited mechanism. Our numerical modeling results suggest that the iron metal grains on the surface of the glass beads were generated through the reduction of FeO by elemental K and (or) Na produced during the impact events. Meanwhile, the iron metal grains inside the bead may have formed due to oxygen diffusion driven by redox potential gradients. Furthermore, our study suggests that impact processes intensify the local reducing conditions, as evidenced by the presence of calcium sulfide particles within troilite grains that coexist with iron metal grains on the surface of the glass beads. This study provides insights into the oxygen diffusion kinetics during the formation of iron metal spherules and sheds light on the changes in redox conditions of lunar materials caused by impact events.

Pang R ，Yang J ，Li R ，Liu S ，Li Q ，Zhu D ，Du W ，Liu Y ... -  《-》

Diverse glasses revealed from Chang'E-5 lunar regolith.

Zhao R ，Shen L ，Xiao D ，Chang C ，Huang Y ，Yu J ，Zhang H ，Liu M ，Zhao S ，Yao W ，Lu Z ，Sun B ，Bai H ，Zou Z ，Yang M ，Wang W ... -  《-》