Chang'E-1 Research Articles

Major Elements Concentrations in Chang’E-3 Landing Site from Active Particle-Induced X-ray Spectrometer

On 14 December 2013 (UTC), China’s Chang’E-3 (CE-3) succeeded in landing on the Moon’s surface. The CE-3 landing site is in northern Mare Imbrium and several tens of meters away from the rim of a young crater with a few hundred meters in diameter. In-situ measurements of lunar soil around the roving area were conducted from Active Particle-induced X-ray Spectrometer (APXS) onboard Yutu rover. Three relatively young lunar soil samples in the CE-3 landing site were investigated. Previous studies suggested that these samples are a new type of basalt, not discovered yet in previous missions before the CE-3 in-situ measurements. It plays an essential role in promoting the understanding of lunar volcanic history. However, their results are deviated, and thus scrutinizing the data as per our optimized model to derive a more precise result is of necessity. In this paper, we present an optimized model for data analysis based on APXS measurements to derive the major elements concentrations. The optimized model has the advantages of reliability and being independent of calibration by ground standards. The particle size effect is applied in lunar X-ray fluorescence modeling for correction, improving the accuracy in determining the elemental concentrations for the actual measurement. Our results are distinct in the correlation plots by carrying out a comparison with previous lunar regolith samples from Apollo, Luna, and Chang’E-5 missions, indicating that the CE-3 landing site is a new region apart from previous in-situ or laboratory detection prior to the CE-3 measurements. It suggests a kind of young mare basalt with unusual petrological characteristics compared with previous samples and similar geochemical properties of CE-3 landing site and western Procellarum and Imbrium (WPI), with a signature of western Procellarum.

New maps of major oxides and Mg # of the lunar surface from additional geochemical data of Chang'E-5 samples and KAGUYA multiband imager data

In the past, global maps of major oxides and magnesium number (Mg #) on the lunar surface had been derived from spectral data of remote sensing images, combined with “ground truth” geochemical information from Apollo and Luna samples. These compositional maps provide insights into the chemical variations of different geologic units, revealing the regional and global geologic evolution. In this study, we produced new maps of five major oxides (i.e., Al2O3, CaO, FeO, MgO, and TiO2) and Mg # using imaging spectral data from the KAGUYA multiband imager (MI) and the one-dimensional convolutional neural network (1D-CNN) algorithm. We took advantage of recently acquired geochemical information from China's Chang'E-5 (CE-5) samples. We used the coefficients of determination (R2) and Root Mean Squared Error (RMSE) as model evaluation indicators. We compared the results with the previous machine learning algorithm models. Our study shows that the 1D-CNN algorithm model used in this study had a higher degree of fit and smaller dispersion between the “ground truth” value of geochemical information and the predicted value of spectral data. The 1D-CNN algorithm generally performs better in describing the complex nonlinear relationship between spectra and chemical components. In addition, we present regions of mare domes in Mairan Dome (43.76°N, 49.90°W) and irregular mare patches (IMPs) in Sosigenes (8.34°N, 19.07°E) to demonstrate the geologic implications of these new maps. With the highest spatial resolution (∼ 59 m/pixel), these new maps of five major oxides and Mg # will serve as an important guide in future studies of lunar geology.

Fe and Mg Isotope Compositions Indicate a Hybrid Mantle Source for Young Chang’E 5 Mare Basalts

The Chang’E 5 (CE-5) samples represent the youngest mare basalt ever known and provide an access into the late lunar evolution. Recent studies have revealed that CE-5 basalts are the most evolved lunar basalts, yet controversy remains over the nature of their mantle sources. Here we combine Fe and Mg isotope analyses with a comprehensive study of petrology and mineralogy on two CE-5 basalt clasts. These two clasts have a very low Mg# (∼29) and show similar Mg isotope compositions to Apollo low-Ti mare basalts as well as intermediate TiO2 and Fe isotope compositions between low-Ti and high-Ti mare basalts. Fractional crystallization or evaporation during impact cannot produce such geochemical signatures that otherwise indicate a hybrid mantle source that incorporates both early- and late-stage lunar magma ocean (LMO) cumulates. Such a hybrid mantle source would be also compatible with the KREEP-like Rare Earth Elements pattern of CE-5 basalts. Overall, our new Fe–Mg isotope data highlight the role of late LMO cumulate for the generation of young lunar volcanism.

Thermal environment of the Chang’E-5 landing site and its effect on the external temperature of the lander

<p indent="0mm">The thermal environment of the lunar surface is extremely important to the thermal design of the lander, the placement of the detection instruments, and the interpretation of scientific exploration data. Clarifying the source and intensity of radiation on the outer surface of the lander is the key to its thermal management. In this paper, we first reported continuous temperature records over a 47.2 h period from five thermal couple sensors mounted on the auxiliary pillars of the landing gear of Chang’E-5 (CE-5). The recorded temperatures varied from a relatively small range of <sc>245.68–272.52 K</sc> at the beginning to a considerably wider range of <sc>284.86–369.76 K</sc> at the end of the recording period. To analyze the obtained CE-5 temperature records, we first developed a lunar surface thermal environment model with a layered regolith and temperature-dependent thermal physical properties. The model calculated that the ambient temperature of the CE-5 landing site over the sensor recording period increased from 341.40 to <sc>356.15 K.</sc> The calculated temperature was comparable to the estimates based on the <italic>in</italic>-<italic>situ</italic> spectral measurement, whereas it was systematically <sc>6–12 K</sc> higher than Diviner thermal infrared brightness temperature. We further developed a heat conduction model of the sensor-mounted auxiliary pillar and considered the surface temperature and the pillar geometry with respect to the Sun’s and the Earth’s orbital parameters. By introducing an impact factor<italic> F</italic> and via trial and error, we fitted the five CE-5 lunar temperature records with the RMESs of 0.72, 2.14, 0.53, 1.35, and <sc>3.36 K,</sc> respectively. Our analysis showed that the lunar surface thermal environment has a significant effect on the temperatures of both the shaded and sunny sides of the lunar lander. The environmental impact on the shaded side even exceeds that on the sunny side during the CE-5 recording period. The results of this paper are of great significance to both the theoretical research on the mechanism of the lunar thermal environment and the engineering applications in the thermal management design of a lunar lander, site selection of a lunar exploration mission, and temperature-related data interpretations, such as <italic>in</italic>-<italic>situ</italic> spectral data analysis.

Chang&amp;rsquo;E-5 samples&amp;mdash;New &amp;ldquo;ground truth&amp;rdquo; for the quantitative inversion of lunar remote sensing

<p indent="0mm">The Chang’E-5 (CE-5) mission successfully returned <sc>1731 g</sc> of lunar soil samples from the northeast of the Oceanus Procellarum. The newly returned lunar soil can provide a new ground truth for the quantitative inversion of lunar remote sensing data. In this study, the mineral and chemical compositions (FeO, TiO₂, Th) of the landing region were obtained from the remote sensing data and compared with the laboratory analysis results of the CE-5 lunar soil samples. The differences between them (especially the olivine content) indicate that there is still room for improvement in the methods for retrieving the elemental and mineral abundances using remote sensing data. Through a systematic comparative analysis, we discovered that: (1) the geochemical characteristics of high FeO, medium TiO₂, and abundant Th in the CE-5 lunar soil are significantly different from the existing Apollo lunar soil, which can provide unique ground truth for remote sensing research; (2) The CE-5 lunar soil represents mature lunar soil developed on the young basalt unit on the moon, with a small proportion of distantly sourced ejecta, representing the mare basalt composition characteristics of the landing region; (3) The CE-5 lunar soil is very fine, which meets the sample standard <sc>(&lt;45 μm)</sc> of the Lunar Soil Characterization Consortium for providing ground truth. Notably, the CE-5 landing region also exhibits unique characteristics: (1) it is located in the mid-latitude region on the western hemisphere of the moon, different from the low-latitude region where the United States and the Soviet Union sample return missions landed; (2) it is located on the late-stage lunar basalt unit; it is different from the existing spectral calibration area. Therefore, the construction of the CE-5 landing area as a new remote sensing calibration site based on the measured data of its lunar soil can significantly expand the geographical scope and global representation of the lunar calibration sites. Based on the results of the remote sensing and sample studies, we delineate the calibration area in the unit where the CE-5 landing site is located (Em4), thus providing a reference for establishing a remote sensing calibration area in the future.

From Schrödinger to Von Kármán: An Intriguing New Geological Structure Revealed by the Chang'e‐4 Lunar Penetrating Radar

AbstractSince early 2019, the Lunar Penetrating Radar (LPR) onboard Chang'e‐4 (CE‐4)’s Yutu‐2 rover has been gathering data relating to the subsurface structure of the Von Kármán crater within the South Pole‐Aitken Basin (SPA) on the lunar farside. Low‐frequency radar data have the potential of carrying geological information of about 300 m worth of strata below the traversed path. Forty‐two days’ data have revealed a bifurcated structure within the layered structure beneath the CE‐4 surveying area for the first time, affecting the overlying reflectors between 90 and 310 m. This study suggests that, based on the morphological characteristics, thickness, depth (timing sequence) and direction of the newly found structure, its origin might be linked to the deposition of ejecta from the Schrödinger impact. The local stratigraphy is interpreted as consisting of distinct geological layers, corresponding to the superposition of ejecta from different impact craters, paleo‐regolith, and basaltic lava flows.

Moon-Based Ground-Penetrating Radar Observation of the Latest Volcanic Activity at the Chang’E-4 Landing Site

The Moon-based ground penetrating radar (GPR) onboard the Chang’E-4 (CE-4) Yutu-2 rover has deployed on the far side of the Moon, which provides the Moon’s far side, providing an unprecedented opportunity to study the shallow surface geological process and the history of the volcanic eruption of the Moon. The high-frequency radar observed a buried lens structure ~27 m below the lunar surface, which was interpreted as paleo-regolith by previous studies. In this study, we conducted a quantitative analysis of the dielectric properties of the buried lens structure observed during the CE-4 mission. Our results reveal that the relative permittivity and loss tangent are of the structure is ~10.5 and ~0.037, respectively. Comparing our estimated dielectric properties with those of Apollo samples and radar-observed lava flows shows that the buried lens is neither regolith nor ejecta material but possibly basalt flow. Additionally, we speculate that the buried basalt flow may represent the latest volcanic eruption on the Moon, possibly from the Eratosthenian-aged volcano that occurred approximately 2.5-2.2 billion years ago. Finally, we update the interpretation of the regolith stratigraphic structure observed by the Yutu-2 high-frequency radar at the CE-4 landing site.

Simulation of Lunar Comprehensive Substructure With Fracture and Imaging of Later LPR Data From Chang’e-4 Mission

As one of the most important geophysical methods for detecting the lunar underground structure of the Moon, the lunar penetrating radar (LPR) is applied to the Chang’e-4 (CE-4) mission to explore the Von Kármán crater on the far side of the Moon. With the Yutu-2 rover continues to move towards the Zhinyu crater at the west, radar will likely detect the fractures created by the impact that formed the Zhinyu Crater. Therefore, the establishment of a comprehensive lunar subsurface structure model with fracture, random media and fractal terrain is crucial for the LPR data processing and the understanding of the lunar geological impact process. In addition, the method that can image the radar data with fractures well has great significance to the interpretation of the LPR data. In this paper, we establish a comprehensive lunar subsurface structure model firstly, the considering factors including fractures, random media, fractal terrain, and the radar response are calculated through forward modeling. Secondly, according to the high resolution and the sensitive to inhomogeneities of LPR data, we design a set of processing flow including plane-wave destruction, velocity analysis based on the focusing analysis method and migration imaging based on the velocity continuation. Finally, the results including simulation data and Antarctic fracture data are used to verify the effectiveness of imaging method.

Microwave Thermal Radiation Analysis of King Crater on the Lunar Farside Using CE-2 MRM Data

King crater is a Copernican crater located near the equator in the western highlands of the lunar farside. The study of the microwave brightness temperature (TB) in this region is of great significance for exploring the interior structure of the lunar farside. The Chang’e-2 (CE-2) microwave radiometer (MRM) is mainly used to obtain TB data on the lunar surface under four channels. This study uses the ordinary Kriging algorithm to interpolate the midday and midnight MRM data of this region and generates the TB maps and TB difference (dTB) maps for each channel in two moments. Combined with UVVIS data from Clementine satellite and Diviner data from LRO satellite, the characteristics of microwave thermal radiation are discussed. The results show that (FeO+TiO2) abundance (FTA) and rock abundance (RA) are important factors affecting thermal radiation anomalies in the King crater. It also provides evidence for the formation of the King-Bruno anomalous belt, which is believed to be significantly related to the formation of the King crater.

Elemental Abundances of Moon Samples Based on Statistical Distributions of Analytical Data

The successful return of Chang’E-5 (CE5) samples urges the hot topic of the study of the Moon in geochemistry. The elemental data of the analyzed moon samples reported in the literature were collected to determine the elemental abundances in moon samples. Based on 2365 analytical records of moon samples from ten missions of Apollo, Luna, and CE5, elemental abundances of 11 major oxides including Cr2O3, 50 trace elements including Ti, P, Mn, Cr, and 15 rare earth elements (REEs) including Y are derived based on statistical distributions of normal, log-normal, and additive log-ratio transformation, respectively. According to the value of 13.5% CaO content, moon samples are classified into two types, as low-Ca and high-Ca samples, whose elemental abundances are also calculated respectively based on the methods used in the total moon samples. With respect to the mid-ocean ridge basalt (MORB) of the Earth, moon samples (including the Moon, low-Ca, and high-Ca samples) are rich in Cr, REEs, Th, U, Pb, Zr, Hf, Cs, Ba, W, and Be and poor in Na, V, Cu, and Zn in terms of their concentrations, and are enriched in Cr and depleted in Na, K, Rb, P, V, Cu, Zn in spider diagrams. The CE5 sample is a low-Ca type of moon sample and is clearly rich in Ti, Fe, Mn, P, Sc, REEs, Th, U, Nb, Ta, Zr, Hf, Sr, Ba, W, and Be and poor in Mg, Al, Cr, and Ni in terms of their concentrations relative to the moon or the low-Ca samples. If compared with the moon sample, the CE5 sample is also clearly rich in K, REE, and P.

Fusible mantle cumulates trigger young mare volcanism on the cooling Moon.

The Chang’E-5 (CE5) mission has demonstrated that lunar volcanism was still active until two billion years ago, much younger than the previous isotopically dated lunar basalts. How the small Moon retained enough heat to drive such late volcanism is unknown, particularly as the CE5 mantle source was anhydrous and depleted in heat-producing elements. We conduct fractional crystallization and mantle melting simulations that show that mantle melting point depression by the presence of fusible, easily melted components could trigger young volcanism. Enriched in calcium oxide and titanium dioxide compared to older Apollo magmas, the young CE5 magma was, thus, sourced from the overturn of the late-stage fusible cumulates of the lunar magma ocean. Mantle melting point depression is the first mechanism to account for young volcanism on the Moon that is consistent with the newly returned CE5 basalts.

Spectral interpretation of late-stage mare basalt mineralogy unveiled by Chang’E-5 samples

The western maria of lunar near-side are widely covered with late-stage mare basalts. Due to the lack of returned samples, the mineralogy of the late-stage basalts was previously speculated as having high abundance of olivine based on remote sensing observation. However, here we show that Chang’E-5 (CE-5) lunar soil samples, the ground truth from past unsampled lunar late-stage mare region, give a different interpretation. Our laboratory spectroscopic and X-ray diffraction (XRD) analyses of the CE-5 soil samples demonstrate that their special spectral signatures are representative of iron-rich high-Ca pyroxene rather than olivine. Considering the spectral and compositional similarities between CE-5 soil samples and lunar late-stage basalts, the mineralogy and petrology of CE-5 samples may be able to be generalized to entire lunar late-stage basalts. Our study would provide a constraint on the thermal evolution of the Moon, especially the young lunar volcanism.

The Lunar Regolith Structure and Electromagnetic Properties of Chang’E-5 Landing Site

On 1 December 2020, China’s Chang’E-5 (CE-5) probe successfully landed in the northeastern Oceanus Procellarum. This work mainly presents the results of Lunar Regolith Penetrating Radar (LRPR) equipped on the CE-5 Lander. The lunar regolith structure of the landing site from the surface to 3-m depth is unveiled by LRPR, which found that abundant rock fragments are distributed in uniform lunar regolith. The imaging result proved that the drilling and sampling process was prevented by big rocks at about 100 cm depth. On the basis of the response of lunar soil to electromagnetic (EM) wave, the EM properties of the landing site estimate that the relative dielectric constant and the loss tangent are 2.520 ± 0.186 and 0.0133 ± 0.0020, respectively.

Understanding the mineralogy and geochemistry of Chang'E-5 soil and implications for its geological significances

Chang'E-5 (CE-5) mission returned 1731 g of lunar soil from northeastern Oceanus Procellarum. This study begins by comparing the mineralogy and geochemistry of CE-5 soil with Apollo and Luna soils. CE-5 soil shares similar mineral components with Apollo mare soils. Geochemically, CE-5 soil is characterized by high-FeO, intermediate-TiO2, and elevated incompatible elements. The new returned CE-5 soil represents a unique type of mare soil that expands the diversity of returned lunar samples. Its bulk chemical compositions suggest that CE-5 soil consists of pulverized local mare basalt. Nonmare materials are thought to be negligible while meteoroid contamination is <1%. CE-5 soil provides an additional iron-rich basaltic end-member composition and extends the chemical ranges of the existing calibration soils for lunar remote sensing. CE-5 soil, together with the landing site, can serve as new ground truth both in mineralogy and geochemistry. Based on bulk chemical data of CE-5 soils and pyroxene compositions of CE-5 mare basalt clasts, we infer that CE-5 mare basalt has a fractional crystallization history similar to the Apollo high-Ti basalts. These CE-5 mare basalt clasts analyzed in recent studies, possibly derive from a single lava flow that experienced strong fractional crystallization.

On the provenance of the Chang'E-5 lunar samples

China's Chang'E-5 (CE-5) mission has collected 1.731 kg samples from a young mare basalt unit (named P58/EM4) in the northeastern Oceanus Procellarum region of the Moon. Accurate tracing of the provenance of returned samples is essential for understanding their laboratory measurements, which can provide critical information about the Moon and the inner Solar System. In this article, the provenance, chemical composition, formation, and evolution processes of the regolith at the CE-5 landing site are analyzed by using remote sensing observations and crater ejecta deposition models. A comprehensive search based on crater ejecta thickness model shows that 1892 impact craters in P58 likely deposited ∼0.56 m of primary ejecta at the landing site, whereas 4 impact craters outside P58 deposited 0.05 m of distal ejecta that further excavated and reworked ∼0.5 m thick local mare basalt. Twelve craters within 1 km from the CE-5 landing site are estimated to contribute ∼0.49 m (~88%) of the ejecta materials, and their ejecta source regions are investigated using the Maxwell Z model. Among these 12 craters, Xu Guangqi and a smaller crater near the landing site are the two most volumetrically significant contributors (~0.3 m and ∼0.12 m). Craters more than 1 km distant from the landing site deposited fewer exotic materials, but some of them could have delivered low-Ti materials to the sampling site. Finally, the regolith stratigraphy at the landing site is investigated based on the identified and assumed impact sequence by using a Monte Carlo-based ejecta ballistic sedimentation model. The results reveal a depth-varying FeO/TiO2 abundance profile at the landing site, suggesting that the sedimentation of distant ejecta can reduce FeO/TiO2 abundance of the underlying layer by ∼1 wt.% at ∼0.5 m depth. Our results provide key information on sample provenance and regolith stratigraphy of the landing site, which is crucial to deciphering the returned CE-5 samples.

Geochemistry of impact glasses in the Chang’e-5 regolith: Constraints on impact melting and the petrogenesis of local basalt

Lunar impact glasses can provide important information on the bulk compositions of their sources and the impact history of the Moon. Here, we report the chemical composition of fifty-four clean glass spherules containing neither relict clasts nor crystals from the Chang’e-5 (CE5) regolith. They can be subdivided into three compositional groups: (1) mid-Ti basaltic (TiO2 = 4.1 ∼ 6.5 wt%), (2) low-Ti basaltic (TiO2 = 1.3 ∼ 3.9 wt%), and (3) high-Al (Al2O3 > 15 wt%). Fifty-one glasses (∼94 %) are mid-Ti basaltic, which form a loose compositional cluster for most major and trace elements. These glasses exhibit considerable variations in SiO2 (35.3 ∼ 45.3 wt%). Their TiO2, Al2O3, MgO and CaO show negative correlations with SiO2, while the Na2O, K2O and P2O5 positively correlate with SiO2, also yielding a positive correlation between the CIPW normative plagioclase and olivine. These variations likely result from differential vaporization of SiO2, strongly suggesting an impact origin of these glasses. Their major and trace element compositions are averagely similar to the bulk-rock, in turn indicating that they were formed from the local regolith. The remaining three glasses, including two low-Ti basaltic and one high-Al variety, exhibit distinct major and trace elements from the regolith, indicating an exotic source. In addition, the mid-Ti basaltic glasses provide another approach for estimating the average composition of the CE5 basalt other than directly measuring the small basalt fragments assuming that the exotic materials in the CE5 regolith were limited. This estimation reveals critical trace element characteristics of the CE5 basalt, e.g., it has higher La/Yb (3.71), Sm/Yb (1.76), Sr/Yb (31.6), and (Eu/Eu*)N (0.45) than KREEP, indicating that CE5 basalt must derive from a non-KREEP source. Chemical modeling indicates that the contribution of KREEP-rich materials in the mantle source should be less than 0.3 %. The trace element characteristics of the CE5 basalt can be reproduced by extensive (80 %) fractional crystallization after low-degree (2 %) melting. We propose that this fractional crystallization process might occur at depth, implying vast igneous underplating (7,250 ∼ 11,750 km3) beneath the CE5 landing area. This study also suggests that the high Th concentration (5.43 ppm) is an inherent property of the CE5 basalt resulting from extensive fractional crystallization. Thus, high Th detected by remote sensing may not be associated directly with a KREEP component but rather with highly fractionated basalts.

Thermophysical properties of the regolith on the lunar far side revealed by the in situ temperature probing of the Chang'E-4 mission.

Temperature probes onboard the Chang'E-4 (CE-4) spacecraft provide the first in situ regolith temperature measurements from the far side of the Moon. We present these temperature measurements with a customized thermal model and reveal the particle size of the lunar regolith at the CE-4 landing site to be ∼15μm on average over depth, which indicates an immature regolith below the surface. In addition, the conductive component of thermal conductivity is measured as ∼1.53×10-3W m-1 K-1 on the surface and ∼8.48×10-3W m-1 K-1 at a depth of 1 m. The average bulk density is ∼471kg m-3 on the surface and ∼824kg m-3 in the upper 30cm of the lunar regolith. These thermophysical properties provide important additional 'ground truth' at the lunar far side, which is critical for the future analysis and interpretation of global temperature observations.

Sulfur Isotopic Fractionation of the Youngest Chang'e‐5 Basalts: Constraints on the Magma Degassing and Geochemical Features of the Mantle Source

AbstractThe unusually prolonged volcanism at the Chang'e‐5 (CE‐5) landing site remains a mystery. To constrain the geochemical features of the CE‐5 mantle source, we performed in situ sulfur isotope analysis on sulfides of the CE‐5 basalts. The modal abundance of sulfides is ∼0.1 wt%, dominated by troilite with trace cubanite, chalcopyrite and pentlandite, yielding a S‐abundance of ∼360 ± 180 ppm for the bulk CE‐5 basalts. Our analysis shows a decreasing trend of δ34S in the magma with crystallization and degassing, suggesting ∼40% degassing loss of S, and accordingly the maximum S‐abundance in CE‐5 primitive magma was calibrated to approximately 600 ± 300 ppm. Considering an extensive fractional crystallization following a low‐degree partial melting of the CE‐5 basalts, the estimated sulfur abundance in the mantle source is ∼1–10 ppm. This result suggests a strong depletion of volatiles in the CE‐5 mantle source, which may be caused by prolonged magmatic activity.

Mineralogy and regolith maturity at the Chang'E-5 landing site inferred from the Lunar Mineralogical Spectrometer

Chang'E-5 (CE-5) landed in the northeast of the Oceanus Procellarum and successfully returned ∼1.73 kg lunar samples from a distinctively young mare basalt unit. The reflectance spectra between 0.45 μm to 3.20 μm at the landing site were acquired by the onboard Lunar Mineralogical Spectrometer before and after the sampling. The results from the spectral parameter analysis show the regolith is dominated by clinopyroxene, consistent with both orbital observations and laboratory analyses of the returned CE-5 samples. Optical maturity (OMAT) of regolith in the landing region of CE-5, Chang'E-4 (CE-4), and Chang'E-3 (CE-3) was analyzed, and the results show that the regoliths at CE-5 and CE-3 sites sitting on the ejecta blanket of the relatively young impact craters are both less mature than that at the CE-4 landing site. The OMAT and estimated content of submicroscopic metallic iron (SMFe) in the regolith show no obvious variations between the rock-shielded and unshielded regolith during the CE-5 descent, indicating the disturbance from rocket exhaust did not affect regolith maturity. Similar results on the effects of rocket exhaust were obtained from analyzing the regolith maturity along the CE-4 rover's traverse. Additionally, the surficial regolith and the scooped underlying layer in the centimeter-depth at CE-5 landing area exhibit similar maturities, suggestive of rapid gardening despite the geologically young age of the region. The results presented in this work shed light on the regolith evolution on the Moon and provide vital geological context for the analysis of the returned CE-5 samples.

A Micro Mid‐Infrared Spectroscopic Study of Chang’e‐5 Sample

AbstractThe Chang’e‐5 (CE‐5) mission has successfully returned samples from a site that is much younger than the sites of all previous lunar sampling missions. Sample analysis results reported so far have revealed a more complex sampling area than previously thought, casting uncertainties over the interpretation of remote sensing spectral data and the U and Th abundance derived from the orbital data. Laboratory spectral measurement of the returned samples can serve as validation of remote sensing observations and thus help refine our understanding of the geological evolution of the landing region. In this study we report detailed micro mid‐infrared (MIR) spectral characteristics of individual soil grains of CE‐5 samples. The spectral analysis results show that the CE‐5 olivine grains have low Fo (molar Mg/[Mg + Fe] × 100) consistent with previous studies, indicating a Fe‐rich source region of the mantle or a highly evolved magma. These olivine grains show high level of crystallinity, implying low degree of space weathering. Most of the CE‐5 glasses analyzed are spectrally consistent with mare impact glasses, despite that a few of them may have a volcanic origin. These laboratory spectral analysis of CE‐5 samples in the MIR wavelengths at a micro scale, together with the derived MIR optical constants of the olivine, pyroxene, plagioclase, and glass grains, provide important input for the modeling and interpretation of thermal remote sensing data of the Moon.