Lunar Samples Research Articles

Lunar Farside Samples Returned by Chang’E-6 Mission: Significance for Understanding the South Pole-Aitken Basin Stratigraphic History

The Chang’E-6 (CE-6) mission, launched by China on 2024 May 3, marks the first successful retrieval of samples from the farside of the Moon, specifically from the southern mare plain of the Apollo basin within the South Pole-Aitken (SPA) Basin. This study aims to provide a comprehensive geological analysis of the Apollo basin, focusing on the Apollo basin materials that CE-6 may have collected. By examining the regional geology, surface mineralogy, thorium (Th) abundance, and crustal thickness, we seek to understand the implications of these materials for the SPA basin’s structure and stratigraphic history. We find that the Apollo basin exhibits significant lateral compositional variations, with Mg-rich noritic materials predominantly in the southwestern portion and more feldspathic materials in the northeast, probably due to the fact that the Apollo basin is situated on different structures of the underlying SPA basin. Those Mg-rich materials, likely representing deep lithologies from local lower crust, are associated with low Th abundance, suggesting a KREEP-poor origin. The inclusion of foreign materials in the CE-6 samples increases the complexity while also enhancing their research potential. In addition to the local mare basalts, Mg-rich noritic materials associated with the Apollo basin and Th-rich materials originating from the SPA basin may also have been collected by CE-6. Laboratory research of these diverse lithologies will contribute to unraveling the characteristics of the farside mantle, the geological history of the giant SPA basin, as well as the cause of the substantial asymmetry between the lunar nearside and farside.

Infrared Spectroscopy of Lunar Core 73001: Upper Limit on Hydration in a Lunar Sample With No History of Exposure to Terrestrial Water Vapor

Infrared Spectroscopy of Lunar Core 73001: Upper Limit on Hydration in a Lunar Sample With No History of Exposure to Terrestrial Water Vapor

The Lunar Regolith Thickness and Stratigraphy of the Chang’E-6 Landing Site

The Chang’E-6 (CE-6) mission successfully returned 1935.3 g of lunar soil samples from the Apollo basin within the South Pole–Aitken basin. One of its scientific objectives is to investigate the subsurface structure and regolith thickness at the landing site. Using remote sensing datasets, we estimated the regolith and basalt thicknesses at the landing site by employing the crater morphology method and crater excavation technique. A total of 53 concentric craters and 108 fresh craters with varying excavation depths were identified. Our results indicate that the regolith thickness at the CE-6 landing site ranges from 1.1 to 7.0 m, with an average thickness of 3.5 m. Beneath the regolith, the basalt layer consists of high-Ti basalt overlaying low-Ti basalt, with a total thickness of approximately 64 to 82 m, of which the high-Ti basalt layer accounts for about 22 to 30 m. Based on the local geological history, we proposed a stratigraphy at the CE-6 landing site. These findings provide valuable geological context for interpreting the Lunar Penetrating Radar data and analyzing the returned samples.

Space exploration in China

Abstract In the past 20 years, China has implemented Manned Space Engineering, Lunar and Mars exploration missions, becoming an active participant in human space travel and exploration. So far China has established its Space Station in 2022, continuing to carry out large-scale space science research for the next 10-15 years. China has successfully achieved the soft landing on the lunar, far side of the Moon and on the Mars surface, obtained 1.73 kg of lunar sample, and will also implement the lunar Antarctic sample return and Mars sample return mission later. The exploration missions for the asteroid and Jupiter system are being prepared. Overall the future science exportations and collaborations between human and robot, as well as the utilisation of extraterrestrial resources will become the new development focus. Chinese scientists eagerly look forward to close international collaboration.

Long-term reduced lunar mantle revealed by Chang’e-5 basalt

The redox state of a planetary mantle affects its thermal evolution. The redox evolution of lunar mantle, however, remains unclear due to limited oxygen fugacity (fO2) constraints from young lunar samples. Here, we report vanadium (V) oxybarometers on olivine and spinel conducted on 27 Chang’e-5 basalt fragments from 2.0 billion years ago. These fragments yield an average fO2 of ΔIW -0.84 ± 0.65 (2σ), which closely aligns with the Apollo samples from 3.6–3.0 billion years ago. This temporal uniformity indicates the lunar mantle remained reduced. This observation reveals that the processes responsible for oxidizing mantles of Earth and Mars either did not occur or had negligible oxidizing effects on the Moon. The long-term reduced mantle may lead to a distinctive volatile degassing pathway for the Moon. It could also make the lunar mantle more difficult to melt, preventing internal heat dissipation and consequently resulting in a slow cooling rate.

Coordinated microanalysis of volatiles in apatite and silicate minerals in ancient lunar basalts

Despite being essentially water-free, nominally anhydrous minerals such as plagioclase and pyroxene represent the biggest reservoir of water in most lunar rocks due to their sheer abundance. Apatite, which incorporates F, Cl, and OH into its mineral structure as essential crystal components, on the other hand, is the only other volatile-bearing phase common in lunar samples. Here, we present the first coordinated study of volatiles (e.g., H2O, Cl, F, and S) in nominally anhydrous minerals combined with isotopic measurements in apatite from the ancient lunar basalt fragments from meteorite Miller Range (MIL) 13317. Apatite in MIL 13317 basalt contains ∼ 2000 ppm H2O and has an elevated δD values (+ 523–737 ‰), similar to Apollo mare basalts, but has high δ37Cl values (+ 29–36 ‰), similar to apatite found in several KREEP-rich samples. MIL 13317 is unique compared with other lunar basalts; it has both elevated δD and δ37Cl values currently only observed in highlands sample 79215 (a granulitic impactite). Based on measurements of H2O in nominally anhydrous minerals and in apatite, the source magma of MIL 13317 basalt is estimated to contain ∼ 130–330 ppm H2O. Assuming reasonable levels of partial melting of the lunar mantle and magmatic degassing during eruption of the basalt, the Moon contained at least one reservoir with < 100 ppm H2O, a δD value of < 0 ‰ similar to carbonaceous chondrites, and extensively fractionated Cl isotopes prior to 4.332 Gyr, the crystallization age of the MIL 13317 basalt.

Nature of the lunar far-side samples returned by the Chang'E-6 mission.

The Chang'E-6 (CE-6) mission successfully achieved return of the first samples from the far side of the Moon. The sampling site of CE-6 is located in the South Pole-Aitken (SPA) basin-the largest, deepest and oldest impact basin on the Moon. The 1935.3g of CE-6 lunar samples exhibit distinct characteristics compared with previous lunar samples. This study analyses the physical, mineralogical, petrographic and geochemical properties of CE-6 lunar scooped samples. The CE-6 soil has a significantly lower bulk density (0.983g/cm3) and true density (3.035g/cm3) than the Chang'E-5 (CE-5) samples. The grain size of the CE-6 soil exhibits a bimodal distribution, indicating a mixture of different compositions. Mineralogically, the CE-6 soil consists of 32.6% plagioclase (anorthite and bytownite), 19.7% augite, 10% pigeonite and 3.6% orthopyroxene, and with low content of olivine (0.5%) but high content of amorphous glass (29.4%). Geochemically, the bulk composition of CE-6 soil is rich in Al2O3 (14%) and CaO (12%) but low in FeO (17%), and trace elements of CE-6 soil such as K (∼630ppm), U (0.26ppm), Th (0.92ppm) and rare-earth elements are significantly lower than those of the lunar soils within the Procellarum KREEP Terrane. The local basalts are characterized by low-Ti (TiO2, 5.08%), low-Al (Al2O3 9.85%) and low-K (∼830ppm), features suggesting that the CE-6 soil is a mixture of local basalts and non-basaltic ejecta. The returned CE-6 sample contains diverse lithic fragments, including local mare basalt, breccia, agglutinate, glasses and leucocrate. These local mare basalts document the volcanic history of the lunar far side, while the non-basaltic fragments may offer critical insights into the lunar highland crust, SPA impact melts and potentially the deep lunar mantle, making these samples highly significant for scientific research.

Raman characterization of lunar highlands simulants for in-situ resource utilization in a lunar setting

Lunar regolith simulants from the NU-LHT series were characterized using different configurations for performing Raman spectroscopy measurements, including with different excitation wavelengths and spot sizes. This testing was performed to explore various Raman measurement configurations for analyzing lunar regolith, especially in terms of capturing distinctive fluorescence features that can provide more information about the composition of the regolith. Results obtained utilizing configurations having a 785 nm laser for excitation showed relatively narrow, intense fluorescence signals between 870 and 890 nm, which, to the best of our knowledge, has not been observed before in lunar regolith or lunar simulant samples. These distinctive fluorescence features, attributed to a specific rare earth element (REE) impurity, adds further support that these types of features can be utilized for identification and potentially quantification of the amount of REE or transition metal impurities in lunar regolith. Further, other aspects of these Raman instrument configurations and their advantages were explored, especially those applicable for use in a lunar environment in support of in-situ resource utilization (ISRU).

Constitutive model analysis of Chang'e-5 simulated lunar regolith solidified bodies under compression

China’s Chang'e-5 spacecraft successfully collected 1731 g of Lunar regolith and returned it to Earth on December 17, 2020. In this paper, Chang'e-5 simulated Lunar regolith is used as the main material to form stable and dense solid Lunar soil structures by adding different amounts of an inorganic curing agent and water. The internal morphology, failure morphology under uniaxial compression, and stress–strain relationship of the Lunar regolith solidified samples (L-R-S-Ss) are then investigated. The damage constitutive model of the Lunar regolith cured body is analyzed according to the stress–strain curves, with the following results found. (1) Scanning electron microscopy indicates that the L-R-S-Ss contain more microvoids and microfractures, which are the main factors that lead to destruction. (2) The uniaxial failure mode of the L-R-S-Ss is primarily split failure, with both vertical and oblique cracks, with the angle between the main crack and the vertical axis being less than 30°. (3) The content of the curing agent and the amount of water are important factors affecting the L-R-S-S strength. As the water content increases, the L-R-S-S compressive strength tends to decrease. The L-R-S-S strength increases with increasing amount of cementitious material. (4) A cubic polynomial and a rational fraction are used to fit the ascending and descending sections of the L-R-S-S stress–strain curves, respectively, and a piecewise constitutive model of the L-R-S-S specimens is proposed. The calculated results of the model are in good agreement with the experimental curves.

The role of imagination in making water from moon rocks: How scientists use imagination to break constraints on imagination

Abstract Scientists recognize the necessity of imagination for solving tough problems. But how does the cognitive faculty responsible for daydreaming also help in solving scientific problems? Philosophers claim that imagination is informative only when it is constrained to be maximally realistic. However, using a case study from space science, we show that scientists use imagination intentionally to break reality-oriented constraints. To do this well, they first target low-confidence constraints, and then progressively higher-confidence constraints until a plausible solution is found. This paper exemplifies a new approach to epistemology of imagination that focuses on sets of imaginings (rather than individual imaginings), and responsible (rather than reliable) imaginings.

Outer spiral drill rod lunar soil sampling resistance moment simulation study

Abstract The task of unmanned automated sampling of China’s lunar exploration is to bring back lunar soil samples with a certain depth, and sampling of external auger drill pipe is the best way. The power and moment size of the lunar surface is limited, so a special design is required. In this paper, a unique structural model of a double-auger drilling tool is designed. It is a movement analysis of lunar soil and drill pipe. We use simulated lunar soil simulations and experiments. The Hertz-Mindlin slip-free model in the discrete element software EDEM was used for numerical simulation. Given the disadvantage of the large amount of computation of discrete elements, the “embedding simulation method” proposed in this paper reduces the amount of computation. When drilling 0.4m and 1m under lunar and earth gravity, the magnitude and influence of drill pipe rotation and vertical velocity on the drag moment were analyzed. We provide the relevant technical parameters of the real unmanned drilling activities on the lunar surface. Through simulation, the rationality parameters of several groups of drill pipe drilling are obtained to ensure the smooth progress of drilling.

Revisiting the formation of lunar anorthosites via the Rb[sbnd]Sr isotope systematics

The incorporation of KREEP (potassium, rare-earth element, and phosphorus), mantle-derived mafic melts and trapped liquid into the lunar ferroan anorthosite (FAN) suite plays a pivotal role in generating their geochemical and isotopic variations. Nonetheless, the specific involvement and distinct roles of these different components remain controversial. This study presents in-situ Sr isotopic data for 28 anorthositic clasts found within lunar feldspathic meteorites to trace their sources and post-modification processes. We find that these plagioclases exhibit substantial variations in their measured 87Sr/86Sr values (0.69978–0.70357), in contrast to the relatively narrow range observed in Apollo 16 FANs, thereby likely reflecting a diverse chemical composition of lunar crustal rocks. In contrast, the analyzed plagioclases have consistently low 87Rb/86Sr ratios (0.00185–0.03962), similar to those of Apollo samples, reflecting impact-induced loss of Rb. Detailed investigations indicate that certain elevated 87Sr/86Sr ratios are probably not caused by terrestrial contamination or instrumental analysis, but most likely result from the decay of 87Rb from sources with initial 87Rb/86Sr higher than 0.0119–0.1380. However, such elevated 87Rb/86Sr values cannot solely result from crystallization of the lunar magma ocean (LMO) and likely involve KREEP components. Combined with trace element data, we estimate the maximum proportion of KREEP melt in the formation of lunar anorthosites. Future analyses of lunar anorthosites collected by China's Chang'e-5 and Chang'e-6 missions will be crucial for validating the observed Sr isotopic heterogeneity.

Petrographic and geochemical analysis of lunar meteorite NWA 11788: Parallels with Luna 20 and the Apollo magnesian granulites

AbstractThe first in‐depth geochemical and petrological analyses of new lunar meteorite Northwest Africa (NWA) 11788 were conducted with the aim of better understanding the diversity of lunar rock types. Petrography, microcomputed tomography, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry were employed to analyze mineralogic/elemental makeup, petrologic profile, melt history, and inferred composition of the lunar mantle from which the crystals in this sample originated from. Geochemical maps of the lunar surface were generated to constrain potential lunar launch locations for NWA 11788. Potential launch locations are concentrated in the outer rims of impact basins on the lunar Eastern nearside limb (e.g., Crisium, Fecunditatis, Marginis, Smythii) and around the South Pole–Aitken Basin. Similarities in the major, minor, and trace element chemistry of NWA 11788 along with its potential launch locations suggest a petrogenetic relationship with regolith samples returned from the Luna 20 mission and the Apollo 16 and 17 magnesian granulites. Additionally, the results of this study add to the growing body of evidence that KREEP (potassium, rare earth elements, phosphorous)‐poor, Mg‐suite‐“like” lithologies are common in non‐Apollo‐type locales, that KREEP may not be required to generate lithologies like the Mg‐suite, and that KREEP is not globally distributed at present.

Charging Properties and Particle Dynamics of Chang’e-5 Lunar Sample in an External Electric Field

Facing the challenges of in-situ utilization of lunar regolith resources, applying an external electric field to manipulate lunar particles has become a promising method for space particle control, which mainly depends on the particle charging properties in the applied electric field. Using the surficial lunar regolith samples brought back from the Moon by the Chang’e-5 mission (CE5 LS), this work successively studied their charging properties, particle dynamics, and their collision damages to aerospace materials under the action of an external electric field in high-vacuum conditions. The results indicated that the charging process and electrostatic projection of lunar regolith particles under high-vacuum conditions were different from those under atmosphere conditions. The particle diameter range of CE5 LS used in the experiment is 27.7–139.0 μm. For electric field strength of 3–12 kV·cm−1, the charge obtained by CE5 LS is 4.8 × 10−15–4.7 × 10−13 C and the charge-to-mass ratio is 1.2 × 10−5–6.8 × 10−4 C·kg−1. The CE5 LS is easier to be negatively charged in an external electric field. Furthermore, significant damages were observed on the target impact surfaces, indicating severe influences of lunar regolith particles on aerospace materials. Our work contributes to a more comprehensive understanding of physical mechanisms controlling the lunar regolith shielding and utilization, and will inspire broad efforts to develop the lunar in-situ engineering solutions.

Late-stage microstructures in Chang’E-5 basalt and implications for the evolution of lunar ferrobasalt

Abstract This study investigates silicate liquid immiscibility (SLI) microstructures in the Chang’E-5 (CE-5) lunar ferrobasalt sample, the youngest recovered mare basalt (ca. ~2.0 Ga). Employing advanced high-resolution imaging techniques and chemical analysis, we examined a subophitic fragment, revealing two distinct types of microstructures indicative of multi-stage SLI events. The first type is observed in the mesostasis pockets and exhibits both “sieve” and “maze” textures, where the Si-K rich glassy phases are interconnected with Fe-rich minerals, e.g., fayalite. This type of microstructure, similar to previous observations in Apollo and Luna samples, is the product of a stable SLI event. The second type is characterized by K-free but high-Si melt inclusions occurring as emulsions in the rims of plagioclase. The entrapment of these emulsions followed a metastable SLI event, with the Fe-rich liquids serving as precursors to subsequent stable SLI processes. Additionally, the Fe-rich droplets within the emulsions underwent coarsening via Ostwald ripening, a phenomenon in which smaller particles in solution dissolve and deposit on larger particles. Our simulation of this coarsening process suggests a duration of at least 15-32 days for the SLI processes, alongside a slow cooling rate (&amp;lt; 0.3 °C/hour) of the late-stage CE-5 lava. We propose that metastable SLI may have influenced the effusive signature of the CE-5 lava flow during its late-stage evolution. The metastable SLI process can potentially lead to the formation of various phases during the late-stage evolution of lunar ferrobasaltic magmas, thereby contributing to the diversity of lunar rock types.

Research on the Encapsulation Device for Lunar Samples

The encapsulation of lunar samples is a core research area in the third phase of the Chinese Lunar Exploration Program. The seal assembly, opening and closing mechanism (OCM), and locking mechanism are the core components of the encapsulation device of the lunar samples, and the requirements of a tight seal, lightweight, and low power make the design of these core components difficult. In this study, a combined sealing assembly, OCM, and locking mechanism were investigated for the device. The sealing architecture consists of rubber and an Ag-In alloy, and a theory was built to analyze the seal. Experiments of the electroplate Au coating on the knife-edge revealed that the hermetic seal can be significantly improved. The driving principle for coaxial double-helical pairs was investigated and used to design the OCM. Moreover, a locking mechanism was created using an electric initiating explosive device with orifice damping. By optimizing the design, the output parameters were adjusted to meet the requirements of the lunar explorer. The experimental results showed that the helium leak rate of the test pieces were not more than 5 × 10−11 Pa·m3·s−1, the minimum power of the OCM was 0.3 W, and the total weight of the principle prototype was 2.9 kg. The explosive driven locking mechanism has low impact. This investigation solved the difficulties in achieving tight seal, light weight, and low power for the lunar explorer, and the results can also be used to explore other extraterrestrial objects in the future.

Experimental Constraints on the Origin of the Lunar High‐Ti Basalts

AbstractHigh‐pressure and high‐temperature experiments were conducted to simulate melting of a hybrid cumulate lunar mantle. The experimental results show that intermediate to high‐Ti lunar pyroclastic glasses (&gt;6 wt% TiO2) can be produced by partial melting of lunar cumulates. High‐Ti basalts are generated when the ilmenite/clinopyroxene ratios in the lunar mantle cumulates are between 1/1 and 4/1, depending on the degree of melting. The presence of an urKREEP component in the mantle cumulate strongly influences Al2O3/CaO of the melts. The experiments provide strong evidence for the model that the compositional diversity of lunar basalts is a consequence of a gravitational overturn of the lunar interior after the lunar magma ocean had solidified. Ilmenite/clinopyroxene in the cumulate mantle, which generates high‐Ti melts at partial melting, do not comprise the ratios in ilmenite‐bearing cumulates (IBC), which crystallized after ∼90% solidification of the lunar magma ocean and indicate local accumulation of ilmenite in the overturned lunar mantle. However, to fully match the natural composition of the most primitive lunar samples, secondary processes such as assimilation are still required.

Orthopyroxene-dominated upper mantle melting built the early crust of the Moon

The paradigm of lunar crust formation has been widely applied to other terrestrial bodies, but the nature of early crust building on the Moon remains enigmatic. Here we report non-Apollo-like highland clasts from the Chang’e-5 mission and find high-alumina melts enclosed in a noritic anorthosite. Geochemistry and phase equilibria modeling suggest that the melt is compositionally parental to lunar magnesian-suite rocks, and was sourced from a plagioclase-bearing, orthopyroxene-dominated upper mantle ( ~ 4.5 kbar and 1225°C). It was formed as a direct consequence of upper mantle melting at the onset of gravitational instability. We propose a continuous early crust formation on the Moon, started from multiple anorthositic cumulate flotations, to upper mantle melting caused by small-scale, in-situ overturn, and eventually ended up by decompression melting of lower mantle cumulates following large-scale, global overturn.

Dataset of replicate Apollo sample magnetizations bearing on impacts and absence of a long-lived lunar dynamo

The absence or presence of a lunar paleomagnetosphere is important because it bears directly on the volatile content of the regolith and exploration targets for Artemis and other missions to the Moon. Recent paleointensity study of samples from the Apollo missions has readdressed this question. Multiple specimens from a young 2-million-year-old glass shows a strong magnetization compatible with that induced by charge-separation in an impact plasma, whereas paleointensities of single crystals yield evidence for null magnetizations spanning 3.9 to 3.2 Ga. Together, these data are consistent with an impact mechanism for the magnetization of some lunar samples, and absence of a long-lived lunar core dynamo and paleomagnetosphere recorded in other samples. Here, we present a dataset that allows researchers to examine replicates of these measurements. For the glass, we present data from specimens that fail standard paleointensity selection criteria but nevertheless imply a complex, changing magnetic field environment. For the single crystals, the replicate measurements further illustrate the initial zero magnetization state of these materials.

Evidence of a hydrated mineral enriched in water and ammonium molecules in the Chang’e-5 lunar sample

Evidence of a hydrated mineral enriched in water and ammonium molecules in the Chang’e-5 lunar sample