Chang'E-5 samples provide unique insights into the composition of the lunar interior similar to 2 billion years ago, but geochemical models of their formation show a significant degree of discrepancy. Trace element abundance measurements in olivine grains in Chang'E-5 sub-sample CE5C0600YJFM002GP provide additional constraints on the basalt source. Geochemical modeling indicates that low-degree (4 %) batch melting of an olivine-pyroxenite lunar magma ocean cumulate, incorporating high levels of trapped lunar magma ocean liquid and plagioclase, can reproduce the rare earth element, Sr, Rb, Sc, Co and Ni abundances in our and previously reported Chang'E-5 samples, as well as observed Rb-Sr and Sm-Nd isotope systematics. Overall, these results strengthen the direct geochemical links between lunar magma ocean evolution and basaltic volcanism occurring similar to 2.5 billion years later. Additionally, Chang'E-5 high-Fo olivine is enriched in the volatile element Ge (1.38-3.94 mu g/g) by similar to 2 orders of magnitude compared to modeled results (< 0.02 mu g/g). As Ge is a mildly compatible element with bulk Ge partition coefficients close to 1, a Ge-depleted initial LMO proposed by previous research cannot yield a high-Ge mantle source for Chang'E-5 basalt, even when invoking assimilation of high-Ge LMO cumulates. The overabundance of Ge requires either a high-Ge, volatile rich initial bulk Moon with chondritic composition or a late Ge chloride vapor-phase metasomatism.

Lunar regolith samples contain fragments of endogenic rocks and exogenous meteorites. We report the first discovery of a chondrule fragment preserved in Chang'e-5 (CE-5) regolith samples. Forsterite and enstatite phenocrysts have extremely high Mg# (> 99) and high Mn/Fe ratios in this chondrule fragment. Its glass mesostasis is heterogeneous and contains hydrogen and carbon, as indicated by Raman peaks. The mineral assemblage, chemical composition, and oxygen isotope anomaly of this fragment are similar to those of type-I chondrules from carbonaceous chondrites. This fragment and other chondritic relics with 3.4 Ga. This contrast suggests that there may have been a change of impactors to the Earth-Moon system during the Imbrian period. Furthermore, this CE-5 chondrule fragment is a direct record of volatile addition to the Moon's surface from meteorites during the Eratosthenian period.

The formation of a unique microstructure of minerals on the surface of airless bodies is attributed to space weathering. However, it is difficult to distinguish the contributions of meteorite impacts and solar wind to the modification of lunar soil, resulting in limited research on the space weathering mechanism of airless bodies. The thermochemical reactivity of troilite can be used to distinguish the contributions of impact events and solar wind to the modification of lunar soil and provide evidence for space weathering of lunar soil. We examined the structure of troilite particles in the Chang'e-5 lunar soil and determined whether an impact caused the thermal reaction. Microanalysis showed that troilite underwent substantial mass loss during thermal desulfurization, forming a crystallographically aligned porous structure with iron whiskers, an oxygen-rich layer, and other crystallographic and thermochemical evidence. We used an ab initio deep neural network model and thermodynamic calculations to conduct experiments and determine the anisotropy and crystal growth of troilite. The surface microstructure of troilite was transformed by the thermal reaction in the vacuum on the lunar surface. Similar structures have been found in near-Earth objects (NEOs), indicating that small bodies underwent the same impact-induced thermal events. Thus, thermal reactions in a vacuum are likely ubiquitous in the solar system and critical for space weathering alterations of the soil of airless bodies.

Apatite is ubiquitous in lunar samples and has been used widely for estimating volatile abundances in the lunar interior. However, apatite compositional and isotopic variations within and between samples have resulted in varying and ambiguous results. Understanding apatite petrogenesis will help with both identifying the appropriate composition for volatile estimation and interpreting isotopic variations. Here we report a comprehensive petrogenetic investigation of apatite in Chang'E-5 (CE5) basaltic sample CE5C0800YJYX013GP. Apatite displays both intra-grain and inter-grain compositional variations with F and Cl contents falling in the ranges of 0.97-2.47 wt% and 0.24-1.09 wt%, respectively. These apatite compositions show relatively low F and high Cl characteristics in comparison to apatites of Apollo high-Ti and low-Ti mare basalts, but are similar to those reported for lunar meteorites LAP 04841 and MIL 05035. We discern three zoning profiles: fractional crystallization (FC)-dominated, degassing-induced and a third indicated by REE-enriched cores, which are interpreted as representing different generations of apatite. FC-dominated zoning is characterized with decreasing F and increasing Cl and S contents from core to rim; while the opposite is true for the degassing-induced zoning. Regardless of the zoning patterns, apatite Cl and S contents display positive correlations, with S contents up to similar to 3000 ppm, much higher than previous reports for Apollo samples (up to similar to 600 ppm). We demonstrate that the fractional crystallization model proposed by Boyce et al. (2014) in combination with H2O degassing and high S contents in melt (likely at sulfide saturation) can explain these high Cl and S contents observed in CE5 apatite. Based on the core composition of the FC-dominated zoning profile, which has the lowest incompatible element concentrations, bulk F, Cl and H2O contents in the parental melt are estimated to be similar to 72 +/- 21, similar to 43 +/- 14 and similar to 1576 +/- 518 ppm, respectively. These estimates have lower F/Cl ratios than those measured in olivine-hosted melt inclusions from Apollo mare basalts. By adopting the petrogenetic model for CE5 basalt proposed by Su et al. (2022), i.e., 10 % partial melting of a hybrid mantle source, followed by similar to 30-70 % fractional crystallization (similar to 50 % for our sample), we estimate the F, Cl, H2O and S contents in the mantle source are in the ranges of similar to 2.5-4.6, similar to 0.7-1.4, similar to 53-105 and similar to 38-125 ppm, respectively, similar to estimates for both depleted Earth mantle and primitive lunar mantle. However, by adopting the model of Tian et al. (2021), 2-3 % partial melting of a mantle source composed of 86 PCS+2% TIRL (PCS, percent crystallized solid; TIRL, trapped instantaneous residual liquid), followed by 43-88 % fractional crystallization, these estimates will be 5-10 times lower. To be certain whether the relatively low F and high Cl characteristics of CE5 apatite imply an enriched mantle source requires further evaluation of the petrogenetic models for CE5 basalt.

Facing the challenges of in-situ utilization of lunar regolith resources, applying an external electric field to manipulate lunar particles has become a promising method for space particle control, which mainly depends on the particle charging properties in the applied electric field. Using the surficial lunar regolith samples brought back from the Moon by the Chang'e-5 mission (CE5 LS), this work successively studied their charging properties, particle dynamics, and their collision damages to aerospace materials under the action of an external electric field in high-vacuum conditions. The results indicated that the charging process and electrostatic projection of lunar regolith particles under high-vacuum conditions were different from those under atmosphere conditions. The particle diameter range of CE5 LS used in the experiment is 27.7-139.0 lm. For electric field strength of 3-12 kV cm-1, the charge obtained by CE5 LS is 4.8 x 10-15- 4.7 x 10-13 C and the charge-to-mass ratio is 1.2 x 10-5-6.8 x 10-4 C kg-1. The CE5 LS is easier to be negatively charged in an external electric field. Furthermore, significant damages were observed on the target impact surfaces, indicating severe influences of lunar regolith particles on aerospace materials. Our work contributes to a more comprehensive understanding of physical mechanisms controlling the lunar regolith shielding and utilization, and will inspire broad efforts to develop the lunar in-situ engineering solutions. (c) 2024 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Leading national space exploration agencies and private enterprises are actively engaged in lunar exploration initiatives to accomplish manned lunar landings and establish permanent lunar bases in the forthcoming years. With limited access to lunar surface materials on Earth, lunar regolith simulants are crucial for lunar exploration research. The Chang'e-5 (CE-5) samples have been characterized by state-of-the-art laboratory equipment, providing a unique opportunity to develop a high-quality lunar regolith simulant. We have prepared a high-fidelity PolyU-1 simulant by pulverizing, desiccating, sieving, and blending natural mineral materials on Earth based on key physical, mineral, and chemical characteristics of CE-5 samples. The results showed that the simulant has a high degree of consistency with the CE-5 samples in terms of the particle morphology, mineral and chemical composition. Direct shear tests were conducted on the simulant, and the measured internal friction angle and cohesion values can serve as references for determining the mechanical properties of CE-5 lunar regolith. The PolyU-1 simulant can contribute to experimental studies involving lunar regolith, including the assessment of interaction between rovers and lunar regolith, as well as the development of in-situ resource utilization (ISRU) technologies. (c) 2024 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The extent of volatile elements on the surface and interior of the Moon remains a highly debated topic. Previous studies conducted on bulk lunar soil samples and solar wind samples collected by the Genesis mission indicate a discernible isotope mass- or non-mass-dependent fractionation of krypton and xenon. However, a detailed investigation of these processes is missing, particularly in determining the possible incorporation of cometary volatiles in the lunar regolith. New lunar soil samples returned by the Chang'e-5 mission provide a chance to answer these key questions. In this study, noble gas isotopes of nine subsamples from a Chang'e-5 scooped sample were analysed through stepwise-heating and total fusion laser extraction. The results reveal that a simple binary mixture of solar wind and cosmogenic components did not explain alone the isotopic composition of these samples. The Xe data shows insignificant amounts of atmospheric Xe and presents clear evidence of cometary contributions to the lunar regolith, with a significant depletion of 134,136Xe compared to that in the solar wind. Additionally, a meteoritic component is identified. Compared to the Apollo results, our findings further validate the theory of Earth's atmospheric escape, substantiate the plausibility of these exogenous admixtures to elucidate the isotopic fractionation mechanisms of Kr and Xe within the lunar regolith, and provide novel insights into long-term constancy in the solar wind composition.

Knowledge regarding the abundance and distribution of solar wind (SW)-sourced water (OH/H2O) on the Moon in the shallow subsurface remains limited. Here, we report the NanoSIMS measurements of H abundances and D/H ratios on soil grains from three deepest sections of the Chang'E-5 drill core sampled at depths of 0.45-0.8 m. High water contents of 0.13-1.3 wt.% are present on approximately half of the grain surfaces (topmost similar to 100 nm), comparable to the values of Chang'E-5 scooped soils. The extremely low delta D values (as low as -995 parts per thousand) and negative correlations between delta D and water contents indicate that SW implantation is an important source of water beneath the lunar surface. The results are indicative of homogeneous distribution of SW-derived water in the vertical direction, providing compelling evidence for the well-mixed nature of the lunar regolith. Moreover, the findings demonstrate that the shallow subsurface regolith of the Moon contains a considerable amount of water.

Remote sensing data revealed that the presence of water (OH/H2O) on the Moon is latitude-dependent and probably time-of-day variation, suggesting a solar wind (SW)-originated water with a high degassing loss rate on the lunar surface. However, it is unknown whether or not the SW-derived water in lunar soil grains can be preserved beneath the surface. We report ion microprobe analyses of hydrogen abundances, and deuterium/hydrogen ratios of the lunar soil grains returned by the Chang'e-5 mission from a higher latitude than previous missions. Most of the grain rims (topmost similar to 100 nm) show high abundances of hydrogen (1,116 to 2,516 ppm) with extremely low delta D values (-908 to -992 parts per thousand), implying nearly exclusively a SW origin. The hydrogen-content depth distribution in the grain rims is phase-dependent, either bell-shaped for glass or monotonic decrease for mineral grains. This reveals the dynamic equilib-rium between implantation and outgassing of SW-hydrogen in soil grains on the lunar surface. Heating experiments on a subset of the grains further demonstrate that the SW-implanted hydrogen could be preserved after burial. By comparing with the Apollo data, both observations and simulations provide constraints on the governing role of temperature (latitude) on hydrogen implantation/migration in lunar soils. We predict an even higher abundance of hydrogen in the grain rims in the lunar polar regions (average similar to 9,500 ppm), which corresponds to an estimation of the bulk water content of similar to 560 ppm in the polar soils assuming the same grain size distribution as Apollo soils, consistent with the orbit remote sensing result.