Chang'E-1 Research Articles

In-Situ Radar Observation of Shallow Lunar Regolith at the Chang’E-5 Landing Site: Research Progress and Perspectives

China accomplished a historic milestone in 2020 when the mission Chang’e-5 (CE-5) to the Lunar’s surface was successfully launched. An extraordinary component of this mission is the “Lunar Regolith Penetrating Radar” (LRPR) housed within its lander, which currently stands as the most advanced payload in terms of vertical resolution among all penetrating radars employed in lunar exploration. This provides an unprecedented opportunity for high-precision research into the interior structure of the shallow lunar regolith. Previous studies have achieved fruitful research results based on the data from LRPR, updating our perception of the shallow-level regolith of the Moon. This paper provides an overview of the new advancements achieved by the LRPR in observing the basic structure of the shallow regolith of the Moon. It places special emphasis on the role played by the LRPR in revealing details about the shallow lunar regolith’s structure, its estimated dielectric properties, the provenance of the regolith materials from the landing area, and its interpretation of the geological stratification at the landing site. Lastly, it envisions the application and developmental trends of in situ radar technology in future lunar exploration.

Yutu-2 Radar Observations at the Chang’E-4 Landing Site: The Shallow Geological Structure and Its Dielectric Properties

China has successfully carried out five lunar exploration missions since 2007. These missions indicate that China has successfully implemented a three-step lunar exploration program of “orbiting, landing, and returning”. Among them, the Lunar Penetrating Radar (LPR) carried by the Yutu-2 rover in the Chang’E-4 (CE-4) mission is the only one still operating on the far side of the Moon. Up to now, the Yutu-2 radar has measured a large amount of scientific data, and its observations are of great significance to human cognition of the geological evolution of the lunar surface and the exploration of possible lunar in situ resources. This paper reviews the scientific results obtained by previous researchers based on the radar exploration data of Yutu-2, focusing mainly on three aspects, e.g., the geological structure of the shallow surface at the CE-4 landing site, the dielectric properties of the shallow subsurface materials and the special geological features. Finally, the prospects of Yutu-2 radar research priorities and future exploration, and the application trend of Moon-based ground-penetrating radar are given.

YOLO-Crater Model for Small Crater Detection

Craters are the most prominent geomorphological features on the surface of celestial bodies, which plays a crucial role in studying the formation and evolution of celestial bodies as well as in landing and planning for surface exploration. Currently, the main automatic crater detection models and datasets focus on the detection of large and medium craters. In this paper, we created 23 small lunar crater datasets for model training based on the Chang’E-2 (CE-2) DOM, DEM, Slope, and integrated data with 7 kinds of visualization stretching methods. Then, we proposed the YOLO-Crater model for Lunar and Martian small crater detection by replacing EioU and VariFocal loss to solve the crater sample imbalance problem and introducing a CBAM attention mechanism to mitigate interference from the complex extraterrestrial environment. The results show that the accuracy (P = 87.86%, R = 66.04%, and F1 = 75.41%) of the Lunar YOLO-Crater model based on the DOM-MMS (Maximum-Minimum Stretching) dataset is the highest and better than that of the YOLOX model. The Martian YOLO-Crater, trained by the Martian dataset from the 2022 GeoAI Martian Challenge, achieves good performance with P = 88.37%, R = 69.25%, and F1 = 77.65%. It indicates that the YOLO-Crater model has strong transferability and generalization capability, which can be applied to detect small craters on the Moon and other celestial bodies.

Inversion of the Lunar Subsurface Rock Abundance Using CE-2 Microwave Brightness Temperature Data

The rock strongly affects the surface and subsurface temperature due to its different thermophysical properties compared to the lunar regolith. The brightness temperature (TB) data observed by Chang’E-1 (CE-1) and Chang’E-2 (CE-2) microwave radiometers (MRM) give us a chance to retrieve the lunar subsurface rock abundance (RA). In this paper, a thermal conductivity model with an undetermined parameter β of the mixture has been employed to estimate the physical temperature profile of the mixed layer (rock and regolith). Parameter β and the physical temperature profile of the mixed layer are constrained by the Diviner Channel 7 observations. Then, the subsurface RA on the 16 large (Diameter > 20 km) Copernican-age craters of the Moon is extracted from the average nighttime TB of the CE-2 37 GHz channel based on our previous rocky TB model. Two conclusions can be derived from the results: (1) the subsurface RA values are usually greater than the surface RA values retrieved from Diviner observations of the studied craters; (2) the spatial distribution of subsurface RA extracted from CE-2 MRM data is not necessarily consistent with the surface RA detected by Diviner data. For example, there are similar RA spatial distributions on both the surface and subsurface in Giordano Bruno, Necho, and Aristarchus craters. However, the distribution of subsurface RA is obviously different from that of surface RA for Copernicus, Ohm, Sharonov, and Tycho craters.

Mineralogy of Surface Materials at the Chang'E‐5 Landing Site and Possible Exotic Sources From In Situ Spectral Observations

AbstractChina's Chang'E‐5 (CE‐5) mission landed at 43.06°N and 51.92°W on 1 December 2020, within the Northern Oceanus Procellarum region of the Moon. The CE‐5 landing site is situated within a young lunar basalt unit estimated to be around 2.0 Ga. A comprehensive understanding of the lunar regolith composition within the CE‐5 region is pivotal as it furnishes additional scientific evidence concerning its origin. This, in turn, would further improve our understanding of lunar geology and evolution. In our studies, we employed a variety of spectral data and derived products including the CE‐5 Lunar Mineralogical Spectrometer data, the ferrous mineral abundance derived from Kaguya Multiband Imager, and the Chandrayaan‐1 Moon Mineralogical Mapper data. These data enabled us to determine and analyze the compositions of the diverse materials present in the CE‐5 region and to pinpoint the origins of exotic materials found therein. Our results indicated that the exotic material within the CE‐5 region is principally composed of clinopyroxene and plagioclase (Pl). Further analysis unveils that the CE‐5 regolith embodies a blend of two distinct varieties of clinopyroxene, designated as Type A and Type B, along with feldspar. This discovery markedly diverges from the conclusions drawn by preceding studies, which relied solely on remote sensing data. Moreover, the exotic materials are predominantly constituted by the ejecta of Harpalus and Aristarchus craters. This finding furnishes a substantial geological background for the analysis of exotic materials in the samples returned by the CE‐5 mission in forthcoming studies.

Origin and implication of pentlandite in Chang'e-5 lunar soils

Sulfides are important accessary minerals in lunar rocks and have great implications for lunar magma activity and subsequent evolution. Pentlandite, as one of important sulfides, has been found over 40 years. Its origin is however remain controversial. Here, we studied the texture, chemistry and crystallography of pentlandite and associated sulfides in Chang'e-5 (CE-5) lunar soils. Pentlandites occurred as lamella and veinlets in troilites, forming a troilite-pentlandite assemblage in basalt but troilite-pentlandite-taenite assemblage in breccia. Transmission electron microscopy (TEM) analyses provide the first robust evidence in lunar samples that pentlandites from both basalts and breccias were exsolved from troilite, rather than originate from the reaction between mobilized sulfur and metallic FeNi, or mobilized Ni with troilite. Considering that troilites in breccias have higher Ni content than basalts, we speculated the origin of pentlandite in breccia might involve a geological process with addition of exotic meteorites. These findings provide new clues for exploring the origin and geological evolution of sulfides on the Moon.

Variations in lunar regolith properties with depth as revealed by Chang'e-5 samples

The lunar regolith layer preserves abundant information on the internal properties of the Moon as well as the space-surface interactions. By gardening and overturning through time, the regolith layer is heterogenous and soils from different depths could record the complex evolution history of the Moon. Chang'e-5 (CE-5) successfully returned scooped samples and drilled samples from the northeastern Oceanus Procellarum of the Moon. In this study, one scooped sample (0–3 cm depth, S0) and two drilled samples (~10 cm depth, S10; and ~ 65 cm depth, S65) were employed to analyze their granulometry and mineralogy by micro Raman spectroscopy. The grain size increases with depth, and the median grain size of S0, S10, and S65 are Φ5.45 (30.2 μm), Φ4.47 (45.0 μm), and Φ3.37 (96.4 μm), respectively. Their mineral types and contents are pyroxene (33.4–40.5 vol%), plagioclase (30.4–33.8 vol%), olivine (9.0–13.1 vol%), glass (6.9–10.7 vol%), FeTi oxide (6.7–7.5 vol%), cristobalite (0.2–3.8 vol%), quartz (0.4–0.9 vol%), and phosphate (0.2–0.6 vol%). The size-dependent mineral modes reveal the relationship between grain size and mineralogy. The mineral modal abundances of 3 soil samples at different depths are roughly similar to that of CE-5 basalts. Raman peak position of quartz may record a peak shock pressure of 31.4 GPa. 5–9 vol% plagioclase amorphization reflects that at least 2–9% exogenous materials in CE-5 soil samples are ejected from craters with diameters larger than 3 km located beyond 50 km from the landing site.

The youngest lunar zircon reveals an extremely fractionated nature of Chang’e-5 basalt

The U(Pb)-Pb age of zircon is commonly used to represent the crystallization age for igneous rocks due to its high closure temperature and robust resistance to impact disturbance. However, no zircon crystallization age has yet been reported for Chang'e-5 (CE-5) basalt due to their limited occurrence in mare basalt. In this study, rare zircon grains from CE-5 lunar samples were investigated by the in-situ Pb isotopic analysis, and a precise zircon crystallization age of 2036 ± 19 Ma was determined from Pb-Pb isochron. This is hitherto the youngest reported crystallization age of lunar zircon, similar to the ages of CE-5 lunar basalts obtained by zirconium (Zr)-bearing minerals such as baddeleyite, tranquillityite, and zirconolite. Petrographic evidence and rare-earth element geochemistry indicate that zircon in the CE-5 lunar basalts were formed by the reaction of early-formed baddeleyite with SiO2 melt within the latest residue of extreme fractionation of a non-KREEP (an acronym for potassium, REE, and phosphorus) basaltic magma. In contrast to the prevailing view that lunar zircon have formed in late-stage enriched melts resulting from extensive fractional crystallization of the Lunar Magma Ocean, this study shows that zircon could be derived from extreme fractionation of non-KREEP basaltic magma unrelated to Lunar Magma Ocean.

Comparative Analysis of Diurnal Thermal Radiation Variation among Lunar Craters of Different Ages Using CE-2 MRM Data

Microwave radiometer (MRM) is one of the important payloads on the Chang’e-2 (CE-2) Lunar satellite. In the Chang’e satellite’s observation of the microwave radiation brightness temperature (TB) on the lunar surface, there are some “cold spots” of microwave thermal radiation at night containing the Jackson crater. In order to compare the diurnal radiation TB differences of “cold spots” on the lunar surface, two typical craters at similar latitudes on the northern hemisphere on the lunar farside were selected: Jackson, which represents the new craters with a large number of discrete rocks on their surfaces; and Morse, which no longer has a large number of rocks after long-term meteorite impact and lunar evolution. In this paper, the diurnal variation of CE-2 MRM data in the two craters is presented, and a comparative analysis is made with the (FeO + TiO2) abundance (FTA) obtained by Clementine UV-VIS data and the rock abundance (RA) data of LRO Diviner. We find that the variation of the "cold spots" of lunar surface thermal radiation is closely related to the RA distribution in the newly formed craters on the lunar surface, and also has a certain correlation with the FTA.

Low Ni and Co olivine in Chang’E-5 basalts reveals the origin of the young volcanism on the Moon

Mare basalts returned by the Chang’E-5 (CE5) mission extend the duration of lunar volcanism almost one billion years longer than previously dated. Recent studies demonstrated that the young volcanism was related neither to radiogenic heating nor to hydrous melting. These findings beg the question of how the young lunar volcanism happened. Here we perform high-precision minor element analyses of olivine in the CE5 basalts, focusing on Ni and Co. Our results reveal that the CE5 basalt olivines have overall lower Ni and Co than those in the Apollo low-Ti basalts. The distinctive olivine chemistry with recently reported bulk-rock chemistry carries evidence for more late-stage clinopyroxene-ilmenite cumulates of the lunar magma ocean (LMO) in the CE5 mantle source. The involvement of these Fe-rich cumulates could lower the mantle melting temperature and produce low MgO magma, inhibiting Ni and Co partitioning into the magma during lunar mantle melting and forming low Ni and Co olivines for the CE5 basalts. Moreover, the CE5 olivines show a continuous decrease of Ni and Co with crystallization proceeding. Fractional crystallization modeling indicates that Co decreasing with crystallization resulted from CaO and TiO2 enrichment (with MgO and SiO2 depletion) in the CE5 primary magma. This further supports the significant contribution of late-stage LMO cumulates to the CE5 volcanic formation. We suggest that adding easily melted LMO components resulting in mantle melting point depression is a key pathway for driving prolonged lunar volcanism. This study highlights the usefulness of olivine for investigating magmatic processes on the Moon.

Exploring the effects of the rocket exhaust of the Chang'E-5 lander on the lunar regolith using LROC NAC and landing camera images

During the Chang'E-5 (CE-5) lander descent process, the rocket exhaust disturbed the lunar surface of the landing area, which may have affected the properties of the collected samples. Therefore, it is necessary to explore the effects of lander exhaust on the landing area. In this paper, the images obtained by the Narrow Angle Camera (NAC) onboard the Lunar Reconnaissance Orbiter (LRO) were used to determine the exhaust-disturbed area. It is found that this area was featured by an increased reflectance of ∼10 ± 1% compared with the background (from I/F = 0.048 to 0.053). According to the magnitude of the change in the reflectance of the landing region, the disturbed area was divided into the focus disturbed zone (FDZ) and the diffuse disturbed zone (DDZ). The DDZ extends from the edge of the FDZ and has a lower reflectance anomaly. The whole exhaust-disturbed area was found to extend mainly via the north-south direction and to have the shape of an irregular ellipse. This spatial extent is highly related to the topographic factors rather than the obstacle avoidance process according to the topography and landing process. The phase function of the lunar surface was used to analyze the photometric performance of the disturbed area. The lower slope of the phase function in FDZ demonstrates less backscattering and a smoothing effect of the disturbed lunar surface. The CE-5 high-resolution LCAM images captured the smoothing and brightening effects of the lunar surface, which confirmed the variation in regolith properties. These effects are consistent with the inference from the NAC observations. The damage to the “fairy-castle” structure of the lunar surface could also contribute to surface smoothing. This study can provide a reference for the subsequent analyses of lunar samples and can help to enhance the understanding of the effect of lander exhaust on the lunar regolith.

Comparison of laboratory and in situ reflectance spectra of Chang’e-5 lunar soil

Context.Reflectance spectra provide essential information on the mineralogical composition of a planetary surface. However, the spectral characteristics of lunar soil are significantly influenced by its photometric properties, coupled with space weathering and particle size.Aims.China’s Chang’e-5 (CE5) mission returned lunar soil samples and obtained in situ spectra of the sampling site, enabling us to compare the laboratory and in situ analyses of the same sample.Methods.In this study, we measured the reflectance spectra of the bulk CE5 soil and two size fractions (<45 and 45–355 μm) at various phase angles (41.3° to 101.3°).Results.The photometric properties of the CE5 samples exhibit back scattering, whereas an in situ measurement appears as forward scattering, indicating that in situ photometric experiments are always necessary for spectral exploration on the Moon. In addition, the scattering properties of the <45-μm fraction are closer to the in situ spectral data, suggesting that the finer fraction could be more representative of pristine lunar soil. The maturity of CE5 soil is estimated to be submature to mature based on the spectral ratio between 750 nm and 950 nm.

Study on Differential Phase Delay of Same‐Beam VLBI in Rendezvous and Docking of Chang'E‐5

AbstractThe Chang'E‐5 (CE5) ascender achieved lunar orbit autonomous rendezvous and docking with orbiter‐returner successfully on 5 December 2020. Same‐beam Very Long Baseline Interferometry (VLBI) (SBI) observations were performed for the first time for autonomous rendezvous and docking in lunar orbit. In this paper, by studying the CE5 rendezvous and docking data observed by the Chinese VLBI network and analyzing the residual differential phase delay of the autonomous control phase, we successfully captured the maneuver of the 5 km holding of the orbiter‐returner. The differential phase delay (DPD) data of the far‐range guidance phase were used to perform orbit determination of the ascender and orbiter‐returner successfully. The results of orbit determination show that the DPD data can improve the relative position accuracy between the ascender and the orbiter‐returner, and the residual root mean square of the DPD data is 5 ps. Furthermore, when one of the probes has only DPD data, its orbit can also be determined.

Large Area High-Resolution 3D Mapping of the Von Kármán Crater: Landing Site for the Chang’E-4 Lander and Yutu-2 Rover

We demonstrate the creation of a large area of high-resolution (260 × 209 km2 at 1 m/pixel) DTM mosaic from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images over the Chang’E-4 landing site at Von Kármán crater using an in-house deep learning-based 3D modelling system developed at University College London, called MADNet, trained with lunar orthorectified images and digital terrain models (DTMs). The resultant 1 m DTM mosaic is co-aligned with the Chang’E-2 (CE-2) and the Lunar Orbiter Laser Altimeter (LOLA)—SELenological and Engineering Explorer (SELENE) blended DTM product (SLDEM), providing high spatial and vertical congruence. In this paper, technical details are briefly discussed, along with visual and quantitative assessments of the resultant DTM mosaic product. The LROC NAC MADNet DTM mosaic was compared with three independent DTM datasets, and the mean differences and standard deviations are as follows: PDS photogrammetric DTM at 5 m grid-spacing had a mean difference of −0.019 ± 1.09 m, CE-2 DTM at 20 m had a mean difference of −0.048 ± 1.791 m, and SLDEM at 69 m had a mean difference of 0.577 ± 94.940 m. The resultant LROC NAC MADNet DTM mosaic, alongside a blended LROC NAC and CE-2 MADNet DTM mosaic and a separate LROC NAC, orthorectified image mosaic, are made publicly available via the ESA planetary science archive’s guest storage facility.

Revealing regolith substructure by Chang’E-5 LRPR with optimized cable delay calibration method

The Lunar Regolith Penetrating Radar (LRPR) onboard the Chang’E 5 lander is the first antenna-array radar deployed for the exploration of an extraterrestrial object. It is able to measure the subsurface structure of the moon at a resolution of ∼10 cm. This work presents a method for calibrating the variable cable delay of the LRPR and an imaging method based on synthesis imaging from Radio Astronomy. The cable delay calibration method effectively calibrates the cable delay shift of the LRPR with a nanosecond-level precision. To validate the accuracy of the cable delay method, we use the data obtained from both the ground experiment and the moon-exploration mission of the LRPR. The imaging method is used to visualize the subsurface structure of the Chang’E-5 (CE-5) landing site. Moreover, Finite-Difference Time-Domain (FDTD) simulation is carried out to help interpret the imaging results. The radar images derived from the LRPR observations show consistency with each other and match the bit force record during the drilling process. The results suggest that the rocks interacted with the CE-5 drill feature a size of 15 to 20 cm.

Experimental and petrological investigations into the origin of the lunar Chang'e 5 basalts

The origin of young Chang'e 5 (CE5) lunar basalts is highly debated. We present results from high-pressure, high-temperature (P-T) phase equilibria experiments, and from petrological modeling, to constrain the depth and temperature of the source of these unique mare basalts. The experimental results indicate that the CE5 basalts could have formed either by melting clinopyroxene and FeTi oxide-rich cumulates in the shallow lunar mantle, or by extreme fractional crystallization of a hot Mg-rich parental melt. Our findings corroborate the local preservation of significant heat (of at least 1200 °C) in the lunar mantle that is needed to generate basaltic melts of CE5 compositions at 2 Ga. We argue that the CE5 basalts are most likely formed by melting of Fe and Ti-rich cumulates in the shallow lunar mantle as extreme fractional crystallization of olivine and plagioclase from picritic parental melts requires too high temperatures in the lunar mantle (> 1500 °C) at ∼2 Ga.

Improvement of Lunar Surface Dating Accuracy Utilizing Crater Degradation Model: A Case Study of the Chang’e-5 Sampling Area

Taking the Chang’e-5 (CE-5) sampling area as an example, this study carried out an investigation on improving the crater size-frequency distribution (CSFD) dating accuracy of lunar surface geologic units based on the crater degradation model. We constructed a three-parted crater degradation model, which consists of the diffusion equation describing crater degradation and equations describing the original crater profile for small craters (D < 1 km) and larger craters (D ≥ 1 km). A method that can improve the accuracy of CSFD dating was also proposed in this study, which utilizes the newly constructed degradation model to simulate the degradation process of the craters to help determine the crater degradation process and screen out the craters suitable for CSFD analysis. This method shows a good performance in regional dating. The age determined for the CE-5 sampling area is 2.0 ± 0.2 Ga, very close to the 2.03 ± 0.004 Ga of isotopic dating result of the returned sample. We found that the degradation state of the craters simulated by our constructed degradation model is highly consistent with the real existing state of the craters in terms of their topographic, geomorphological, and compositional (e.g., FeO) features. It fully demonstrates that the degradation model proposed in this study is effective and reliable for describing and distinguishing the degradation state of craters over time due to the cumulative effects of small craters. The proposed method can effectively distinguish between diffusively degraded (which conform to the degradation model) and non-diffusively degraded (which do not conform to the degradation model) craters and improve the CSFD accuracy through the selection of the craters. This not only provides an effective solution to the problem of obtaining a more “exact” frequency distribution of craters, which has long plagued the practical application of the CSFD method in dating the lunar surface but also advances our understanding of the evolutionary history of the geologic units of the study area. The results of this work are important for the in-depth study of the formation and evolution of the moon, especially for lunar chronology.

Compositional Variability of 2.0‐Ga Lunar Basalts at the Chang'e‐5 Landing Site

AbstractChina's Chang'e‐5 (CE‐5) mission successfully returned a total of 1.731 kg of lunar material from the north‐eastern Oceanus Procellarum region. Young (∼2.0 Ga) ages were reported from the CE‐5 basalts. However, there are controversies on whether they are low‐Ti or high‐Ti mare basalt type. Here, we report the results of a comprehensive petrographic, elemental, and Pb isotopic investigation on a 17.6 mg CE‐5 basalt clast (CE5C0000YJYX048). By combining high‐resolution X‐ray tomography of the clast and microbeam (scanning electron microscope SEM, electron probe microanalyzer EPMA) analyses of mineral grains peeled off the clast surface, we derived the bulk clast chemical composition with a very small sample consumption (i.e., <3 mg). The poikilitic clast has a bulk TiO2 content of 3.78 ± 1.01 wt%, which is representative of a low‐Ti basalt end‐member in the lunar mare basalts samples. Furthermore, the pyroxene in the studied clast is dominantly pigeonite, in contrast to other reported CE‐5 samples where augite is the dominant pyroxene mineralogy. Despite these compositional peculiarities, in situ secondary ion mass spectrometer dating yielded a Pb‐Pb age of 2,040 ± 22 Ma for the fragment, which is consistent with ages reported from other CE‐5. Based on the chemical and age data analyzed in this study, it can be concluded that the lunar basalts obtained from the CE‐5 mission originated from a low‐Ti mare basalt‐type source. The mineral composition of the mare basalt clast studied, which is dominated by pigeonite, fayalite, and anorthite, likely resulted from late‐stage magmatic crystallization when the magma was enriched in Fe.

Unveiling the mechanics of lunar regolith erosion through analysis of CE-4 and CE-5 landing images and fluid simulation

During landing, the plume from the lander erodes the regolith on the lunar surface, thus destroying the nature of this surface. Landing also provides an opportunity to extract the mechanical properties of the lunar regolith in situ and to study wind erosion on airless bodies such as the Moon. Our goal in this study is to quantify the interparticle force of the lunar regolith, the erosion depth, and other parameters and to test the reliability of the plume erosion model. The erosion depth provides the necessary reference information for the precise interpretation of scientific results obtained from returned samples. We measure the total mass of the lunar regolith mobilized by the plume during the Moon landing. This information is also helpful for future lunar missions. With high-quality data from the Chang’E-5 (CE-5) and Chang’E-4 (CE-4) missions, we measure the erosion depth and the total mass and combine the results with computational fluid dynamics (CFD) to extract the interparticle force. We then test the plume erosion model according to the results from image measurement and CFD and propose a new formula with which to calculate the threshold friction velocity at which plume erosion is initiated. This calculation shows that the interparticle force for a 4-μm-diameter particle is 3.38–16.1 nN. The results also show that the CE-5 landing plume stripped away a 1.2-cm-deep layer of regolith, creating a ≈10-m-diameter crater on the lunar surface, and dispersed ≈441 kg of lunar regolith. Any analysis of a CE-5 drilling sample that is sensitive to the regolith depth must consider this 1.2-cm-thick eroded layer. When a plume erodes the lunar surface, the minimum shear stress required is much less than that predicted by the erosion model, which can no longer be used to predict whether erosion will occur.

Diverse glasses revealed from Chang’E-5 lunar regolith

ABSTRACT Lunar glasses with different origins act as snapshots of their formation processes, providing a rich archive of the Moon's formation and evolution. Here, we reveal diverse glasses from Chang’E-5 (CE-5) lunar regolith, and clarify their physical origins of liquid quenching, vapor deposition and irradiation damage respectively. The series of quenched glasses, including rotation-featured particles, vesicular agglutinates and adhered melts, record multiple-scale impact events. Abundant micro-impact products, like micron- to nano-scale glass droplets or craters, highlight that the regolith is heavily reworked by frequent micrometeorite bombardment. Distinct from Apollo samples, the indigenous ultra-elongated glass fibers drawn from viscous melts and the widespread ultra-thin deposited amorphous rims without nanophase iron particles both indicate a relatively gentle impact environment at the CE-5 landing site. The clarification of multitype CE-5 glasses also provides a catalogue of diverse lunar glasses, meaning that more of the Moon's mysteries, recorded in glasses, could be deciphered in future.