Abstract:The Chang'e 6 (CE6) mission achieved the first sample return from the lunar farside in 2024, recovering 1 935.3 g of regolith. This study focuses on ilmenite in CE6 lunar soil breccia and basalt clasts, integrally employing characterization techniques such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA), high-resolution transmission electron microscope (HRTEM), electron energy-loss spectroscopy (EELS), and three-dimensional electron diffraction (3DED) to systematically investigate the mineralogical characteristics of ilmenite with different occurrences in the CE6 lunar soil. The results indicate that ilmenite in basaltic clasts exhibits characteristics of primary magmatic origin, whereas ilmenite in breccia clasts commonly displays shock-metamorphic features such as mechanical fragmentation and impact melting. Raman spectra show no resolvable differences in peak positions or full width at half maximum (FWHM) among ilmenite grains with different occurrences. HRTEM observations reveal neither dislocation development nor amorphization, confirming the preservation of lattice integrity despite prolonged exposure to lunar surface impact processes. Compositional variations between ilmenite in basalt and breccia clasts are minor, and no significant changes in Ti or Fe valence states were detected. Notably, compared to ilmenite from basalt clasts, those from breccia clasts display relative enrichment in trace elements and a higher abundance of oxygen vacancies, which could be ascribed to shock metamorphism. These findings provide robust mineralogical evidence for the exceptional resistance of ilmenite to impact-induced structural modification and refine our understanding of its occurrence and stability within the lunar surface environment.

Abstract:The Chang'e-5 (CE5) and Chang'e-6 (CE6) missions returned lunar regolith samples from the Procellarum KREEP Terrane (PKT) on the Moon's nearside and the South Pole-Aitken Basin (SPA) on the farside, respectively, providing invaluable materials for comparative studies of geological differences between the Moon's two hemispheres. Spinel group minerals are significant accessory phases in various lunar rocks. Owing to their complex isomorphic substitution, spinel can offer unique constraints on the petrogenesis of lunar lithologies. This study systematically investigates the petrographic and compositional characteristics of spinel grains in the Chang'e samples. In CE5 basalt samples, spinel crystals predominantly occur as inclusions in olivine grains. They evolve toward titanium-iron end member with progressive magma differentiation. Spinel in CE5 breccias and impact melt fragments generally exhibit similar features to those in basalts. In CE6 basalts, spinel grains are mainly hosted by pyroxene or occur as interstitial phase coexisting with fayalite and ilmenite, rarely found in olivine. They share a similar compositional evolution trend to CE5 basalts. Moreover, CE6 samples also contain diverse types of spinels derived from distinct sources, including Mg-suites, aggregates from lunar mantle, and impact-generated fragments with nonlunar signatures. Based on spinel compositions in basalts, thermodynamic models were conducted to constrain the parental magma compositions of CE5 and CE6 low-Ti basalts. Our results indicate that compositions of bulk basalts or melt inclusions are not appropriate proxies for the real parental magma. In addition, both the model results and the trace-element analyses of spinel samples suggest the crystallization sequences of the CE5 and CE6 basalts are different. Therefore, when reconstructing magma compositions from equilibrium melt with different lunar minerals, it is essential to consider the specific stage of magmatic evolution represented by the mineral.

Abstract:The formation mechanism of high-valence iron oxides on the lunar surface is one of the key issues in planetary science. To reveal the formation conditions and evolutionary processes of such minerals, this study conducted detailed microstructural characterization and iron valence-state analyses of spherical magnetite particles identified in Chang'e-5 lunar soil. The results show that the particle is composed of micrometer-scale magnetite grains cemented by Si—O amorphous material lacking volatile elements such as F and Cl. Combined with its spherical morphology, internal cavity, aggregated grain texture, and Si—O-rich amorphous material between grains, these features suggest that the spherical magnetite most likely formed in an impact-induced, oxygen-bearing silicate vapor/melt environment. Together with recent discoveries of high-valence iron oxides in Chang'e-5 and Chang'e-6 lunar soils, this study further demonstrates that impact-induced oxidation is a key mechanism for the formation of Fe³⁺-bearing minerals on the lunar surface, providing new constraints on local oxidizing environments and the origin of magnetic anomalies on the Moon. In addition, the Fe³⁺/ΣFe ratio within the outermost ~40 nm of the magnetite decreases to ~56.3%, which is highly consistent with the reduction depth caused by solar-wind H⁺/He⁺ implantation. This provides direct in situ mineralogical evidence for solar-wind-induced reduction of magnetite and has important implications for evaluating the effects of space weathering on the spectral characteristics of magnetite and for future lunar remote-sensing exploration.

Abstract:Trivalent iron (Fe³⁺) has been confirmed to exist on the highly reduced lunar surface, yet its formation mechanism remains unclear. In this study, using the electron microprobe flank method, we detected Fe³⁺ (Fe³⁺/ΣFe=0～0.31) within 15 impact glass spherules from the Chang'e-5 (CE-5) returned samples. We propose that during meteorite impacts, disproportionation of Fe²⁺ occurs within the melt, generating Fe³⁺; this same disproportionation reaction simultaneously produces metallic iron (Fe⁰), representing a significant pathway for the formation of metal iron particles within impact glass beads. The Fe³⁺/ΣFe ratio in CE-5 impact glass beads containing metallic iron particles show certain negative correlation with Na₂O, K₂O, and P₂O₅, and a positive correlation with CaO and MgO, supporting the impact process simultaneously causing the volatilization of volatile elements and the disproportionation reaction of iron. The origin of Fe³⁺ in homogeneous impact glass beads is the impact process. We observe no correlation between Fe³⁺/ΣFe and Cl as well as SO₃ in the CE-5 glass beads, suggesting that the impact process is highly complex: while disproportionation occurs, the melt simultaneously undergoes high-temperature degassing and subsequent re-incorporation of volatile elements from the impact vapor phase, which compensates partly their loss due to the impact process. This study suggests that the evaporation and reabsorption of volatile elements and the disproportionation reaction of iron occur simultaneously during the impact process, with no obvious causal relationship. Some glass beads containing metallic iron particles exhibit extremely low Fe³⁺ /ΣFe ratios, and the origin of metallic iron particles within the glass beads is complex and not solely attributable to disproportionation reactions.

Abstract:To constrain the microscale redistribution behavior of volatile components, with S as the main focus, under transient thermal events on the lunar surface, this study employed atom probe tomography (APT) to perform three-dimensional nano- to atomic-scale characterization of a microregion on the surface of a Chang'e-6 lunar soil glass bead. The results show that this microregion is dominated by heterogeneous silicate glass enriched in O, Si, and Al. A columnar microstructural discontinuity was identified within the glass matrix. Across this structure, the concentrations of major elements remain broadly continuous, whereas the trace element S shows local depleted in its core. Meanwhile, density isosurfaces extracted from multiple major elements in this region all show similar columnar structures, which are attributed to local electric-field distortion induced by the physical interface and to trajectory overlap effects during APT analysis. Taken together, these chemical distribution characteristics and physical imaging effects indicate that this structure is not a phase boundary formed by chemical differentiation, but is more likely a microscale physical defect related to local thermal-event modification. The local depletion of S may reflect the redistribution of volatile components, with S being the main focus of this study. These results provide atomic-scale observational constraints on the local distribution of trace volatile components in lunar soil and their relationship with microstructures.

Abstract:GRV 022905 is a winonaite recovered from the Grove Mountains in Antarctica. In this study, we employed optical microscopy, scanning electron microscopy with backscattered electron (BSE) image, and electron probe microanalysis (EPMA) to investigate its petrological and mineral chemical features. The meteorite displays typical thermal metamorphic recrystallization features, including abundant triple junctions, while no chondrules or relict chondrules are observed. Mineral chemical analyses reveal that the primary mineral assemblage consists of forsterite (Fa_4.8±0.2), enstatite (Fs_4.5±0.2Wo_2.9±0.1), chromian diopside (Fs_2.3±0.2Wo_41.5±0.5), plagioclase (An_25.5±1.5Ab_70.0±1.2Or_4.5±0.2), kamacite, and minor troilite, with accessory minerals such as schreibersite and apatite. Petrographic and compositional data indicate that the sample experienced FeNi metal-troilite partial melting accompanied by melt migration, resulting in depletion of troilite and low Ni content in kamacite. Textural evidence, such as K-rich feldspar (An_2.3Ab_78.4Or_19.3) filling interstices between other mineral grains and plagioclase enclosing subhedral to euhedral orthopyroxene grains (about 10 μm in size), suggests the occurrence of silicate partial melting. GRV 022905 probably represents a product modified by multiple superimposed thermal events, and its petrogenesis can be interpreted by a three-stage thermal evolution model.

Abstract:Martian soil simulants serve as substitute materials for authentic martian soil and have been widely employed in scientific research and engineering tests. The Martian Garden commercially supplies two martian soil simulants to global researchers: MMS-1 and the enhanced MMS-2. Although both have been utilized in numerous studies, critical essential data on their chemical and mineralogical compositions as well as spectral properties remain lacking, which limits the evaluation of material applicability and in-depth analysis of the related experimental results. In this study, we systematically characterized the chemical and mineralogical compositions as well as spectral properties of MMS-1 and MMS-2 using X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), electron probe microanalysis (EPMA), Fourier transform infrared spectroscopy (FTIR), visible-near infrared spectroscopy (VNIR), and scanning electron microscopy (SEM), followed by an evaluation of their applicability based on these results. The results indicate that the major chemical components of MMS-1 and MMS-2 (such as SiO₂, Al₂O₃, Fe₂O₃, MgO, and CaO) exhibit certain deviations from both the reference data provided by The Martian Garden and the chemical compositions of martian soils in situ measured at various landing sites. Nevertheless, they show a relatively high degree of similarity to the chemical compositions of soils or rocks at certain specific sampling points along the rover traverse paths. MMS-1 primarily consists of andesine, accompanied by minor pyroxene, Al-rich smectite, Mg-rich smectite, Fe(Ⅲ)-rich smectite, quartz, calcite, and hematite, along with trace amounts of gypsum, alunite, olivine, and amorphous silica, and possibly minor illite and indialite. Its VNIR spectrum closely matches observations from Mars orbiters on the global scale. MMS-2, built upon MMS-1, incorporates additional hematite, quartz, gypsum, and periclase, and possibly glauconite, with spectral features more consistent with the orbital data from localized gypsum-enriched areas on Mars. Overall, both MMS-1 and MMS-2 can be regarded as high-quality martian soil simulants. MMS-1 exhibits chemical composition, mineralogical assemblage, and spectral features that are highly similar to those of authentic martian soil, making it a suitable experimental material for scientific investigations related to Mars, including martian geological evolution. In contrast, MMS-2, as a simulant enriched in secondary minerals, confers distinct advantage for investigating the role of secondary minerals in martian soil amelioration. Following detailed characterization of their physical and mechanical properties, MMS-1 and MMS-2 are also applicable to rover engineering tests and in-situ resource utilization (ISRU) studies.

Abstract:The origin of the Moon is a key issue for understanding the early evolution of the Earth-Moon system and the inner Solar System. Since the Apollo era, the giant impact hypothesis has remained one of the leading hypotheses for the origin of the Moon, but the broad isotopic similarities between Earth and Moon have also imposed important challenges on this model. In recent years, advances in high-precision isotopic analysis, progress in lunar sample chronology, and the return of samples by Chang'e-5 and Chang'e-6 missions have substantially improved our understanding of lunar formation, magma-ocean evolution, and late-stage volcanisms. This paper reviews recent progress in geochemistry, petrology, and isotopic geochronology, with emphasis on the giant-impact origin of the Moon, and the subsequent evolution of the lunar magma ocean. Current studies broadly support lunar formation within several tens to more than one hundred million years after Solar System formation, although significant disagreement remains among different isotopic systems and their interpretations. Samples returned by Chang'e-5 and Chang'e-6 extend known lunar volcanism to about 2.0 Ga and 2.8 Ga, respectively, and provide key constraints for improving the lunar crater chronology and understanding the thermal asymmetry between the nearside and farside.

Abstract:Baddeleyite (ZrO₂) is an important Zr-bearing mineral in lunar mafic-ultramafic rocks. Owing to its high uranium content, low initial lead, and high U-Pb closure temperature, this mineral serves as a unique chronometer for constraining the timing of lunar magmatic and impact events. This paper reviews recent advances in the study of lunar baddeleyite, focusing on its major formation mechanisms (magmatic crystallization, zircon decomposition, and tranquillityite decomposition) and corresponding morphological features. This paper further discusses how phase transformations recorded in baddeleyite can be used to infer high-temperature and high-pressure events, and summarizes its key contributions to constraining the formation of the lunar crust, mare volcanism, and large-scale impact events. Finally, this review highlights existing challenges in thermodynamic constraints, micro-scale element migration, and U-Pb system complexity in the study of lunar baddeleyite, and outlines future research directions combining high-resolution microanalytical and experimental approaches.

Abstract:Impact cratering is a critical exogenic process driving the Moon's geological evolution, and the high-pressure mineral phases formed during this process serve as natural thermobarometers and chronometers to record these extreme physical events. The formation processes of high-pressure mineral phases in shocked materials are closely related to the pressure-temperature-time paths of impact events. Therefore, high-pressure mineral phases and their formation mechanisms are extensively utilized for estimating shock conditions and constraining the impact history of the inner Solar System. Meanwhile, as the analogy samples for interior materials in terrestrial planets, high-pressure minerals aid the understanding of mantle transition zones and lower mantle compositions. Therefore, the research of high-pressure mineral phases has great geological significances. This paper reviews the research progress of high-pressure mineral phases formed on the Moon. It elaborates on the physical mechanisms underlying shock-induced mineral phase transitions and the preservation mechanisms of high-pressure mineral phases. In addition, this paper systematically summarizes the mineralogical characteristics, occurrences, and formation mechanisms and conditions of the 15 high-pressure mineral phases currently identified in lunar samples, including stishovite, seifertite, ringwoodite, and majorite. Finally, this paper outlines future prospects of analysing samples returned by future deep space explorations in conjunction with dynamic high-pressure and high-temperature experimental simulations, which will provide critical evidence for reconstructing the lunar impact history and the evolution of the Earth-Moon system.

Abstract:New minerals from the lunar preserve direct mineralogical evidence for the formation, transformation and preservation of lunar materials under the Moon's extreme physicochemical conditions, including low oxygen fugacity, dryness, high vacuum, intense irradiation and repeated impact processing, serving as a crucial link between lunar sample studies and planetary evolution. Based on returned samples from the Apollo, Luna, Chang'e missions and lunar meteorites, this paper summarizes and discusses the mineral classification, genetic mechanisms and mineralogical significance of new minerals from the lunar. The results show that a total of 10 new minerals from the lunar have been discovered and approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA-CNMNC) to date. Among them, the new minerals from returned lunar samples all come from the Apollo and Chang'e missions, including pyroxferroite, armalcolite, tranquillityite, yoshiokaite, changesite-(Y), magnesiochangesite-(Y) and changesite-(Ce). The new minerals from lunar meteorites samples include hapkeite, donwilhelmsite and magnesiochangesite-(Ce). These new minerals from the lunar can be classified into the oxygen-containing salt mineral class (mainly silicates and phosphates), the oxide and hydroxide mineral class (mainly oxides), and the class of native elements, intermetallic compounds, and carbides, silicides, nitrides, and phosphides (mainly silicides). Their genesis primarily involves dry and highly reduced magmatic differentiation, impact melting-devitrification and high-pressure phase transformation and vapor-phase deposition space weathering. In recent years, the discovery of the changesite-series rare-earth phosphates, provids new mineralogical constraints on lunar magmatic evolution, behavior of rare earth elements differentiation, and the diversity of lunar materials. Investigations of lunar-related mineral phases that have been previously reported but are not approved as new mineral species are also of great significance for understanding impact metamorphism, volatile preservation, redox processes, and lunar regolith evolution.