Abstract The delivery and evolution of carbonaceous materials to airless planetary bodies remain poorly constrained. This study characterized a porous, aggregated, carbon-rich dust particle (CE6-CDP) from Chang’e-6 lunar samples. CE6-CDP yielded a mean δ13CVPDB value of − 25.92 ± 3.62‰ and exhibited significant nitrogen enrichment. Nano-infrared spectroscopy further detected N–H, C = N, and C–H bonds, indicating that the carbonaceous material within CE6-CDP shows organic-like signatures. Graphitic carbon with tangled and concentric textures within CE6-CDP exhibited a comparable δ13CVPDB value (−27.31‰) but contained low nitrogen, suggesting possible graphitization of some organic precursors. The coexistence of organic-like carbonaceous material and graphitic carbon is consistent with dust ejection during an impact involving a larger carbon-rich projectile. This study indicates that extraterrestrial carbon may constitute an important lunar carbon reservoir and contribute to the dark surfaces of Mercury and Vesta. These findings provide new insights into carbon transport and evolution across airless planetary bodies.

The degassing of solar wind-related volatiles is thought to contribute to volatile cycling on the Moon. However, it remains uncertain which lunar minerals preferentially release them. Here, we report an unusual foamy texture found only on the surface of ilmenite crystals within a Chang'e-6 (CE-6) basalt clast. The distribution and chemical composition of this texture indicates that it results from in-situ melting of the ilmenite surface rather than from an impact-induced splash melt. Considering the evidence-including the long exposure time, presence of deep-seated planar defects, open vesicles, large spherical np-Fe0 particles, and a rutile-like mineral-the foamy texture is interpreted to result from the intense release of abundant solar wind-related volatiles (e.g., H/H2, He, and OH/H2O) by an impact-induced conductive heating event. Restriction of the foamy texture to the surface of ilmenite within the CE-6 basalt clast indicates that solar wind composition, especially for H-related volatiles, are released more intensely from ilmenite than from silicate minerals such as pyroxene and plagioclase. Our findings suggest that solar wind-related volatiles released from high-Ti mature regolith likely made a greater contribution to the lunar exosphere and the lunar surface volatiles, including polar deposits, relative to those from low-Ti immature regions. This has important implications for understanding volatile cycles and future in-situ resource utilization on the Moon.

The mechanisms governing the lunar water cycle and hydrogen isotope (D/H) fractionation driven by solar wind implantation and micrometeorite impacts remain poorly understood. Here, using synergistic simulation experiments, we show that micrometeorite impacts not only enhance the formation of solar wind-derived water through impact-induced mineral damage, but also enable the formed solar wind-derived water to be partially retained within the impact melt. Micrometeorite impacts also induce significant hydrogen isotope fractionation, resulting in the preferential retention of isotopically lighter water within the melt, while leaving the residual water isotopically heavier in the region surrounding the impact area due to thermally driven escape. We estimate that H2O released from minerals can migrate across the surface and ultimately contribute 4.34 & times; 109 - 2.39 & times; 1010 kg of water ice to the polar regions within 105 years. This study elucidates the solar wind and micrometeorites impact-driven water cycle and D/H fractionation on the Moon - processes that might also occur on other airless bodies such as Mercury and asteroids, and provides crucial insights into the origin of water in the terrestrial planets.

The behavior of volatile elements during silicate evaporation and condensation is crucial for understanding planetary formation. The Hertz-Knudsen-Langmuir equation suggests that the species evaporating from silicates are theoretically the same as those condensing simultaneously. However, recent findings from Chang’E-5 (CE-5) impact glass beads have challenged this view, with the sodium (Na) and potassium (K) oxides from the glass beads evaporating and subsequently Na and K condensing as atomic species. Here, we report two Chang’E-6 (CE-6) impact glass beads of highland origin that exhibit similar geochemical features to the previously reported CE-5 mare basaltic beads. The convergence of evidence from the distinct compositional terranes of CE-5 and CE-6 demonstrates that the condensation of atomic Na and K vapor is a common process during lunar impact events, independent of the target rock composition. Thermodynamic calculations show that at temperatures exceeding 2000 K during evaporation, O2 dissociates into atomic O, which preferentially escapes from the rock-vapor produced by impact due to its lower atomic mass than Na or K under lunar low-gravity conditions. This produces an oxygen-depleted transient atmosphere that leads to the condensation of atomic Na and K, triggering a redox reaction that incorporates the alkali metals into the melt as their oxides. In contrast, Apollo volcanic glass beads formed at relatively lower temperatures (<1800 K) without O2 dissociation, so there was no atomic Na or K condensation. These results fundamentally redefine our understanding of volatile behavior during lunar impact events and provide a new framework for interpreting surface geochemical processes on airless bodies.

Lunar regolith has undergone prolonged space weathering, primarily driven by solar wind irradiation and micrometeorite impacts, which has substantially altered the mineral’s surface properties. The extent of solar wind radiation damage on mineral surfaces varies, depending on differences in the mineral structure, composition, and exposure duration. Here, we investigated space weathering features of two FIB foils from two Chang’e-6 lunar grains, minerals including chromite, titanomagnetite, ilmenite, pyroxene, and merrillite. These minerals exhibited diverse responses to solar wind irradiation with an increasing resistance sequence: pyroxene < titanomagnetite < ilmenite < (chromite, merrillite). Through a comparative analysis of their damage characteristics, ilmenite generated a higher abundance of space weathering products (e.g., vesicles), suggesting it possesses superior resource utilization on the Moon. Furthermore, nanophase metallic iron (npFe0) formed in all iron-bearing minerals, with its particle size positively correlating with bulk iron content. In chromite, both the npFe0 particle size and vesicle increased with prolonged solar wind radiation exposure. This study enhances our understanding of space weathering in lunar minerals, providing insights relevant to the evolution of lunar regolith, while also establishing its significance for guiding the in situ utilization of lunar surface resources.

Studies of Chang'e-5 samples have indicated a high content of solar wind-derived water at middle latitudes on the lunar surface. However, the implantation-diffusion and retainment of solar wind-derived water at lunar daytime temperatures remains unclear, leaving the formation and preservation of solar wind-derived water in minerals poorly understood. Here, we conducted experiments on 1.5 keV deuterium (D) ions implanted into silicate minerals at 356 K to simulate the solar wind proton implantation at noon in the middle latitudes of the Moon. The results showed that OD formed and partial D reached several micrometers depth in the minerals after implantation, which was a result of radiation-enhanced diffusion. The diffusion coefficient was estimated to be 10(-11)-10(-12) cm(2) s(-1) and was affected by the implantation fluence, temperature, and mineral crystal structure. This study provides insights into the distribution of water on the lunar surface by investigating the formation and diffusion of solar wind-derived water preserved in different minerals at elevated temperatures.

Context. Space weathering on airless bodies results in the formation of nanophase metallic iron (np-Fe-0) particles, which will cause spectra darkening and reddening. However, the effects of temperatures and iron contents on np-Fe-0 particles formation by H+ irradiation have not yet been well understood. Aims. This research focuses on revealing how temperatures and iron contents affect the formation of solar wind-derived np-Fe-0 particles. Methods. We selected Chang'e 5 (CE-5) olivine and pyroxene grains with different iron contents and removed their native space weathering rim. H+ irradiation experiments were conducted at 87 +/- 2 degrees C and room temperature, with an energy of 1.5 keV and a fluence of 1.0 x 10(18) ion/cm(2). Raman spectroscopy (Raman) was used to determine the mineral phases and the changes of chemical bonds before and after H+ irradiation. Fourier transform infrared spectroscopy (FTIR) was used to observe the Christiansen features (CFs), Reststrahlen bands (RBs), and the formation of water (OH/H2O) before and after H+ irradiation. Transmission electron microscopy (TEM) and dispersive X-ray spectroscopy (EDS) were used to observe the microstructure and composition of np-Fe-0 particles, while electron energy loss spectroscopy (EELS) was used to analyze the valence states of iron. Results. Np-Fe-0 particles are only produced in the minerals with high iron contents after H+ irradiation at 87 +/- 2 degrees C, rather than minerals with high iron contents but irradiated at room temperature or minerals with low iron content irradiated at 87 +/- 2 degrees C. Compared with the np-Fe-0 particles that are formed by impact melting, solar wind irradiation can effectively lower the formation temperature by about one magnitude. Conclusions. This research provides direct evidence of np-Fe-0 particle formation by H+ irradiation experiments and clarifies the necessary conditions, indicating solar wind irradiation is an effective way for np-Fe-0 particles formation. The variation in iron contents and temperatures will help us to recognize the formation of np-Fe-0 particles at different lunar regions and other airless bodies such as Mercury and asteroids, evaluating the effect of space weathering on remote sensing more precisely.

M-type asteroids are historically thought to be exposed metallic cores of differentiated planets with a composition dominated by pure iron and nickel. However, recent spectral and radar observations reveal an insufficient number of M-type asteroids in the main belt. Here, we report unusual space weathering characteristics associated with a natural metal grain found in Chang'e 5 lunar soil. Microcraters, impact glass, iron whiskers, and unique vesicular rims on the surface of this grain help to explain the unusual properties of some potential M-type asteroids, including low thermal inertia and density. Our findings indicate that space weathering processes, including micrometeorite bombardment and solar wind irradiation, conceal the real surface signatures of M-type asteroids. Furthermore, the presence of He and Ge alloy on the metal grain suggests that M-type asteroids are not only a large metallic Fe and Ni reservoir but also a potential source of noble gases and precious metals.

The image of a bone-dry surface in the Moon's non-polar regions impinged by the Apollo missions was changed by the detection of widespread absorption near 3 mu m in 2009, interpreted as a signature of hydration. However, debates persist on the relative contribution of molecular water (H2O) and other hydroxyl (OH) compounds to this hydration feature, as well as the cause of the potential temperature-dependence of the OH/H2O abundance. Resolving these debates will help to estimate the inventory of water on the Moon, a crucial resource for future space explorations. In this study, we measured the abundance and isotope composition of hydrogen within the outermost micron of Chang'e-5 soil grains, collected from the lunar surface and from a depth of 1 m. These measurements, combined with our laboratory simulation experiments, demonstrate that solar-wind-induced OH can be thermally retained in lunar regolith, with an abundance of approximately 48-95 ppm H2O equivalent. This abundance exhibits small latitude dependence and no diurnal variation. By integrating our results with published remote sensing data, we propose that a high amount of molecular water (similar to 360 +/- 200 ppm H2O) exists in the subsurface layer of the Moon's non-polar regions. The migration of this H2O accounts for the observed latitude and diurnal variations in 3 mu m band intensity. The inventory of OH and H2O proposed in this study reconciles the seemingly conflicting observations from various instruments, including infrared/ultraviolet spectroscopies and the Neutral Mass Spectrometer (NMS). Our interpretation of the distribution and dynamics of lunar hydration offers new insights for future lunar research and space missions.

The existence of molecular H 2 O and evolution of solar wind–derived water on the lunar surface remain controversial. We report that large amounts of OH and molecular H 2 O related to solar wind and other multiple sources are preserved in impact glasses from Chang’e-5 (CE5) lunar soil based on reflectance infrared spectroscopy and nanoscale secondary ion mass spectrometry analyses. The estimated water content contributed by impact glasses to CE5 lunar soil was ~72 ppm, including molecular H 2 O of up to 15 to 25 ppm. Our studies revealed that impact glasses are the main carrier of molecular H 2 O in lunar soils. Moreover, water in CE5 impact glasses provides a record of complex formation processes and multiple water sources, including water derived from solar wind, deposited by water-bearing meteorites/micrometeorites, and inherited from lunar indigenous water. Our study provides a better understanding of the evolution of surficial water on airless bodies and identifies potential source and storage pathways for water in the terrestrial planets.

Micrometeorite impacts are one of the main drivers of lunar space weathering and can alter the properties of lunar regolith. However, the details of such processes are not well understood yet. We used transmission electron microscopy to study a micrometeorite impact crater on a glass bead returned by Chang'e-5. We detected Ti-oxide deposits on the crater rim and identified their detailed structure as rutile (TiO2), trigonal Ti2O and triclinic Ti2O. The trigonal Ti2O and triclinic Ti2O are newly discovered mineral phases in lunar samples. We show that these Ti-oxide deposits could have formed by vaporization or deposition processes following a high-velocity microimpact on the lunar regolith. We suggest that such Ti minerals are previously overlooked space-weathering products on the Moon. Similar alterations to photocatalytic properties and reflectance spectra of regolith may also happen on other airless planetary bodies in the Solar System. Micrometeorite impacts are an important process in forming several Ti oxides, including rutile (TiO2) and new Ti minerals (trigonal Ti2O and triclinic Ti2O). These Ti oxides can alter the photocatalytic properties and reflectance spectra of regolith on the Moon and other airless planetary bodies in the Solar System.

Context. The solar wind protons implanted in silicate material and combined with oxygen are considered crucial for forming OH/H2O on the Moon and other airless bodies. This process may also have contributed to hydrogen delivery to planetary interiors through the accretion of micrometre-sized dust and planetesimals during early stages of the Solar System. Aims. This paper experimentally investigates the depth distribution of solar wind protons in silicate materials and explores the mechanisms that influence this profile. Methods. We simulated solar wind irradiation by implanting 3 keV D-2(+) ions in three typical silicates (olivine, pyroxene, and plagio-clase) at a fluence of similar to 1.4 x 10(17) ions/cm(2). Fourier transform infrared spectroscopy was used to analyse chemical bond changes, while transmission electron microscopy (TEM) characterised microstructural modifications. Nanoscale secondary ion mass spectrometry (NanoSIMS) was employed to measure the D/O-16 ratio and determine the depth distribution of implanted deuterium. Results. The newly produced OD band (at 2400-2800 cm(-1)) in the infrared spectrum reveals the formation of O-D bonds in the irradiated silicates. The TEM and NanoSIMS results suggest that over 73% of the implanted D accumulated in fully amorphous rims with a depth of 70 nm, while 25% extended inwards to similar to 190 nanometres, resulting in partial amorphisation. The distribution of these deuterium particles is governed by the collision processes of the implanted particles, which involve factors such as initial energy loss, cascade collisions, and channelling effects. Furthermore, up to 2% of the total implanted D penetrated the intact lattice via diffusion, reaching depths ranging from hundreds of nanometres to several micrometres. Conclusions. Our results suggest that implanted solar wind protons can be retained in silicate interiors, which may significantly affect the hydrogen isotopic composition in extraterrestrial samples and imply an important source of hydrogen during the formation of terrestrial planets.

Microwave sintering is a key technology for future lunar habitats, which has been verified by various lunar soil simulant experiments. However, nanophase iron (np-Fe0), a unique component of the real lunar regolith, has been ignored in previous studies of the microwave sintering of lunar soil simulants. In this study, microwave-sintering experiments of lunar soil simulant CLRS-2 with and without np-Fe0 at different temperatures were conducted. A comparison of the microstructure and chemical composition of sintered products indicates that all products of samples with 1.0 wt% np-Fe0 exhibit better properties than those without np-Fe0 after heating at equivalent temperatures. Adding np-Fe0 to the lunar soil simulant CLRS-2 couples well with microwaves, which may increase the real heating temperature in a sample, resulting in the product being solidified at 700 degrees C and a relatively dense product forming at 900 degrees C, thus improving the sintering efficiency. This study suggests that microwave sintering is an effective potential technology for future lunar habitats and road hardening because of the wide distribution of np-Fe0 in the lunar regolith. The technical parameters given in this study can provide an important guide for future lunar construction by microwave sintering. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.

Understanding crust–atmosphere interactions on Venus is fundamentally important to interpretations of Venus’ surface spectroscopic data. Olivine, in basaltic crust, is oxidized under a heated CO2 atmosphere. However, the oxidation rates, product assemblages and spectral characteristics of olivine samples with different Fa# values remain largely unclear. Herein, we investigated the oxidation of olivine with different Fa# values (Fa09, Fa29 and Fa71) under CO2 atmosphere at 470 °C and 900 °C and characterized the oxidation products (both microscopically and macroscopically), conversion rates and VNIR spectra. The results showed that the oxidation of olivine produced magnesioferrite, magnetite, laihunite, hematite and maghemite at 470 °C and hematite, magnetite, magnesioferrite and amorphous SiO2 at 900 °C. Both high temperature and high Fa# values accelerated the oxidation rates. The production of oxide coatings on olivine grains (74 μm in size) was estimated to be completed within tens to hundreds of years at 470 °C in natural settings, with even shorter periods under higher temperatures. Thus, CO2 oxidation would quickly eliminate olivine spectral characteristics, and spectral parameters at 850 and 1020 nm, as well as other relevant spectral windows (considering shifts induced by the elevated temperature), could be used to trace olivine oxidation processes. This work presented a case study connecting microscopic features to spectral characteristics for Venus’ surface–atmosphere interactions. Further studies considering more realistic Venus’ surface–atmosphere conditions will be essential to better interpret the measured spectroscopic data and determine the origins of the high emissivity detected on elevated terrain on Venus.

Metallic iron (Fe0) particles with sizes ranging from a few nanometers to the submicroscopic scale and formed by space weathering are specific components of lunar soil. Previous studies have suggested that the iron significantly alters the optical properties of lunar soil. For example, nanophase metallic iron (npFe0) causes both reddening and darkening of the lunar soil spectrum, and submicroscopic metallic iron (SMFe) only causes darkening. Here, we prepared SMFe particles with an average size of -180 nm embedded within melt glasses through carbothermal reduction experiments to analogize agglutinated glasses in the lunar soil. We evaluated the effect of SMFe content on visible and near-infrared (VIS-NIR) reflectance spectra of these lunar soil samples simulants. The spectral data show that SMFe content plays a key role in the optical properties of samples, including the average reflectance in the VIS-NIR range (400-2150 nm), and the absorption depth at -2 & mu;m. A small amount (0.05 wt%) of SMFe mainly causes significant spectral darkening, and the average reflectance is reduced by 50% when the SMFe content rises to 0.36 wt%. Both the average reflectance and the absorption depth at -2 & mu;m show a negative correlation with the SMFe content. We developed a quantitative model relating the spectral characteristics and the SMFe abundance based on experimental results. Thus, the SMFe contents play a key role in altering spectral characteristics of airless bodies during remote sensing spectroscopic detection.

Context. Olivine responds to space weathering in the fastest and most profound way, which results in significant space weathering spectral alteration effects (SWSAEs) on airless silicate bodies. Although Mg-rich olivine (Fa 10 ) has been subjected to extensive studies, SWSAEs of Fe-rich (Fa# > 20) or Fa-dominant (Fa# ⩾ 50) olivine are still poorly understood. Aims. We aim to systematically characterize the space weathering effects and the associated spectral alterations of Fe-rich olivine on the surface of Phobos and the Moon. Methods . We conducted nanosecond pulsed laser irradiation experiments on a set of synthetic Fe-rich olivine (Fa 29 , Fa 50 , Fa 71 , and Fa 100 ) with energy levels simulated for Phobos and the Moon and analyzed the irradiated olivine for microscopic characteristics and near-infrared (NIR) and Raman spectroscopy. Results . Micron-level thick alteration layers are found in Fa 100 compared to those hundreds of nanometers thick in Fa 29 , Fa 50 , and Fa 71 . With increasing irradiation energy levels and Fa# values, nanophase iron (np-Fe 0 ) particles increase in size but decrease in quantity. The np-Fe 0 formed via in situ decomposition are ubiquitously present, while those formed via vapor deposition are primarily found in Fa 29 but rarely in Fa# ⩾ 50. The size fraction of intermediate (10–40 nm) and large (40–60 nm) np-Fe 0 proportionally increases with Fa# values. The NIR spectra of weathered olivine show darkening over reddening in most cases, but Fa100 under the most irradiated condition shows brightening-reddening spectral effects. The Raman spectra of weathered olivine show a reduction in intensity without peak shifts. Conclusions . The Fa# values of olivine are a more critical factor in controlling the SWSAEs on Phobos than those on the Moon. If Phobos and Deimos contain substantial Fe-rich or Fa-dominant olivine, similar to Mars, thick alteration rims and large np-Fe 0 formed via space weathering may cause darkening-reddening and potentially brightening-reddening spectral effects on the Martian moons.

小行星的有机物记录了太阳系早期有机物的形成发展历史,为地球早期生命前体出现的研究提供了重要依据,对于研究生命起源和演化具有重要意义.本文综合分析了小行星表面可能存在的有机物成分、种类及其赋存状态,利用红外光谱开展地面模拟实验,探讨有机物的红外光谱特征及其影响因素.结果表明,不同类型有机物的红外光谱特征与其类型、结构、温度和压力等有关.研究确定了小行星表面主要有机物的红外光谱识别标志,初步提出了小行星有机物红外光谱探测仪器的基本指标参数.

: Nanophase iron (np-Fe 0 ) is a major product of space weathering and its presence significantly alters the reflectance spectral characteristics of lunar soil. Previous studies have established that the np-Fe 0 particles originate from the reduction of ferrous ions in the plasma, in-situ decomposition of olivine and pyroxene, and disproportionation of ferrous ions in solid ferrosilicates. In this study, sample charging effects were eliminated and in situ nanoscale valence state analysis of iron-bearing phases in Chang’E-5 lunar soil was conducted by combining focused ion beam (FIB) microscopy, Auger electron spectroscopy (AES), and transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS) techniques. The results indicate that the contents and valence states of iron in the np-Fe 0 particles, amorphous matrix, and ferrosilicates differ. The np-Fe 0 particles were found to be composed of pure metallic iron, whereas ferrous and ferric iron ions were present in olivine crystals and the amorphous matrix, respectively. The discovery of both metallic and ferric iron in the amorphous matrix of Chang’E-5 lunar soil offers new insights regarding the disproportionation reaction of Fe 2+ on the lunar surface. This study demonstrates that the combination of FIB, AES, and TEM-EELS is an effective and precise approach for analyzing the valence states of iron-bearing phases in lunar soil, which can be extended to other extraterrestrial samples and other multivalent elements.

The formation and distribution of lunar surficial water remains ambiguous. Here, we show the prominence of water (OH/H2O) attributed to solar wind implantation on the uppermost surface of olivine, plagioclase, and pyroxene grains from Chang'E-5 samples. The results of spectral and microstructural analyses indicate that solar wind-derived water is affected by exposure time, crystal structure, and mineral composition. Our estimate of a minimum of 170 ppm water content in lunar soils in the Chang'E-5 region is consistent with that reported by the Moon Minerology Mapper and Chang'E-5 lander. By comparing with remote sensing data and through lunar soil maturity analysis, the amount of water in Chang'E-5 provides a reference for the distribution of surficial water in middle latitude of the Moon. We conclude that minerals in lunar soils are important reservoirs of water, and formation and retention of water originating from solar wind occurs on airless bodies.