Lunar Crust Research Articles

A sample of the Moon's far side retrieved by Chang'e-6 contains 2.83-billion-year-old basalt.

Remote sensing observations have shown that the far side of the Moon (lunar farside) has different geology and rock composition to the near side, including the abundances of potassium, rare earth elements, and phosphorus (collectively known as KREEP). The Chang'e-6 (CE-6) spacecraft collected samples from the South Pole-Aitken (SPA) basin on the farside and brought them to Earth. We use lead-lead and rubidium-strontium isotope systems to date low-titanium basalt in a CE-6 sample, finding a consistent age of 2830 ± 5 million years. We interpret this as the date of volcanism in SPA and incorporate it into lunar crater chronology. Strontium, neodymium and lead isotopes indicate the volcanic magma was from a lunar mantle source depleted in incompatible elements and containing almost no KREEP component.

A reappraisal of the petrogenesis of Apollo 17 lunar dunites 72415‐72417: Relics of the deep lunar mantle?

A reappraisal of the petrogenesis of Apollo 17 lunar dunites 72415‐72417: Relics of the deep lunar mantle?

Shallow Moonquake Mechanisms Illuminated by Rheologic Characteristics of Basaltic Gouges

AbstractThe projected evolutionary history of the Moon and observed occurrence of moonquakes suggest that brittle faulting is present in the shallow lunar crust. The main component of the lunar crust, plagioclase, shows velocity‐strengthening behavior in the range of crustal temperatures. Chang'e 5 samples of lunar regolith show a mineral composition almost identical to basaltic bedrock. We measured the friction‐stability characteristics of dry synthetic gouges representative of basaltic faults assumed to be present in the lunar crust. Frictional strengths are ∼0.7 and exhibit an overall velocity‐strengthening response but transition to velocity‐weakening at intermediate temperatures (∼200–300°C) and stresses (∼25–100 MPa). Bounding temperature profiles representative of the lunar crust suggest that moonquakes are feasible in the lunar crust. The rheological heterogeneity of mineral fragments in basalt is a potential cause of unstable sliding on faults with the related steady‐state stress drop close to the minimum of the estimated dynamic stress drop. This suggests that some events with small stress drops are associated with the instability of mature basalt faults. However, observations of shallow moonquakes with high stress drop but merely moderate magnitude suggest that high degrees of healing on immature faults, small seismic nucleation lengths, or the failure of intact crust are present. We emphasize that moonquakes may arise from stress transfer and accumulation due to processes such as cooling contraction.

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

Mare Volcanism in Apollo Basin Evaluating the Mare Basalt Genesis Models on the Moon

The Apollo basin is a well-preserved double-ringed impact basin located on the northeastern edge of the South Pole–Aitken (SPA) basin. The Apollo basin has been flooded and filled with large volumes of mare lavas, indicating an active volcanism history. Based on orbital data, we reveal that the Apollo basin exhibits an overall asymmetric configuration in the distribution of mare basalts as well as its topography, chemical compositions, and crustal thickness. The Apollo basin is an excellent example for assessing the influences of the above factors on mare basalts petrogenesis and evaluating mare basalt genesis models. It was found that the generation of mare basalt magmas and their emplacement in the Apollo basin seems to be strongly related to local thin crust (<30 km), but the formation of basaltic magmas should be independent of the decompression melting because the mare units (3.34–1.79 Ga) are much younger than the pre-Nectarian Apollo basin. The mare basalts filled in the Apollo basin exhibits a large variation of TiO2 abundances, indicating the heterogeneity of mantle sources, which is possible due to the lunar mantle overturn after the LMO solidification or the impact-induced mantle convection and migration. However, the prolonged mare volcanic history of the Apollo basin is not well explained, especially considering the low Th abundance (<2 ppm) of this region. In addition, the central mare erupted earlier than other mare units within the Apollo basin, which seems to contradict the predictions of the postbasin loading-induced stresses model. Laboratory investigations of the Chang’E-6 mare basalt samples could possibly answer the above questions and provide new insight into the mare volcanic history of the lunar farside and the connections between mare volcanism and impact basin formation/evolution.

Investigating Subsurface Properties of the Shallow Lunar Crust Using Seismic Interferometry on Synthetic and Recorded Data

AbstractIn the past few years, the remarkable progress of commercially operated spacecrafts, the success with reusable rocket engines, as well as the international competition to explore space, has led to a substantial acceleration of activities in the design and preparation of ambitious future lunar missions. In the search for ice and/or cavities imaging the shallow subsurface structure is of vital importance. Hereby, previous studies have shown that seismic interferometry is a promising method to investigate the subsurface properties from passive lunar data. In this study, we want to evaluate the potential of this method further by examining the required duration of seismic measurements and the influence of scattering on the Green's function retrieval. Therefore, we applied seismic interferometry to both measured Apollo 17 data and synthetic data. Our findings indicate that, under optimal conditions, a few hours of data are sufficient when using the method of time‐scaled phase‐weighted stack (ts‐PWS). However, this strongly depends on the inter‐station distance, the orientation toward the principal noise sources, and the timing of the measurement during the lunar cycle. Additionally, we were able to reproduce the measured data using numerical simulations in 2D. The synthetic results show that scattering effects clearly influence the Green's function extraction, especially for larger station distances.

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.

A Low‐Viscosity Lower Lunar Mantle Implied by Measured Monthly and Yearly Tides

AbstractThe Moon's frequency‐dependent tidal response, expressed as temporal variations in its gravity field through the Love number and as dissipation through the quality factor , provides information about its interior structure. Lunar laser ranging has provided measurements for , but so far no frequency‐dependent values for have been determined. We provide the first spacecraft measurements of and at two frequencies, monthly and yearly, from an analysis of Gravity Recovery and Interior Laboratory and Lunar Reconnaissance Orbiter radio tracking data. Interior modeling indicates that these values can be matched only with a low‐viscosity zone at the base of the lunar mantle, even when using complex rheological laws to model the mantle's response. The existence of this zone has profound implications for the Moon's thermal state and evolution.

Geological investigation of the lunar Apollo basin: From surface composition to interior structure

The Apollo basin, located in the northeastern part of the South Pole-Aitken (SPA) basin, represents one of the Moon's most significant geological features, offering profound insights into the lunar interior structure, the effects of the SPA impact, and the history of lunar crust evolution. This study presents an in-depth geological analysis of the Apollo basin region, revealing the distribution of rock types and compiling a comprehensive geologic map that correlates with the lithologic and geochemical properties of the area. Utilizing the characteristics and compositional provenance of the geologic units, we have constructed schematic cross-sections that elucidate the interior structure and stratigraphic evolution of the Apollo basin region. Despite excavations of the SPA and Apollo impacts, the anorthositic crust of this area was not entirely removed and has been uplifted to shallow depths, making it more susceptible to exposure by subsequent impacts. Additionally, upper mantle material, characterized by ultramafic, low-Ca pyroxene, was excavated by the SPA impact and is present in the impact melt/breccias of the Apollo basin. After the formation of the Apollo basin, multiple mare units were emplaced over a period potentially spanning ∼1.5 billion years, with the oldest of these maria being superposed by substantial postdating basin ejecta. The results of this study strengthen our understanding of the geology and evolution of the Apollo and SPA basins and offer valuable insights for interpreting the exploration and sample analysis results of the Chang'e-6 mission.

A lunar core dynamo limited to the Moon’s first ~140 million years

Single crystal paleointensity (SCP) reveals that the Moon lacked a long-lived core dynamo, though mysteries remain. An episodic dynamo, seemingly recorded by some Apollo basalts, is temporally and energetically problematic. We evaluate this enigma through study of ~3.7 billion-year-old (Ga) Apollo basalts 70035 and 75035. Whole rock analyses show unrealistically high nominal magnetizations, whereas SCP indicate null fields, illustrating that the former do not record an episodic dynamo. However, deep crustal magnetic anomalies might record an early lunar dynamo. SCP studies of 3.97 Ga Apollo breccia 61016 and 4.36 Ga ferroan anorthosite 60025 also yield null values, constraining any core dynamo to the Moon’s first 140 million years. These findings suggest that traces of Earth’s Hadean atmosphere, transferred to the Moon lacking a magnetosphere, could be trapped in the buried lunar regolith, presenting an exceptional target for future exploration.

Anatomy of a Lunar Silicic Construct—The Wolf Crater Complex, Mare Nubium and Implications for Early Silicic Magmatism on the Moon

AbstractSilicic lithologies on planetary surfaces indicate magmatic evolutionary processes in their interiors. The Wolf crater complex within Mare Nubium on the Moon is one such silicic construct associated with a high thorium anomaly. This study integrates morphological, compositional, chronological and gravity anomaly analyses of high‐resolution data from various lunar missions to establish this construct as a silicic volcanic caldera. Lobate flows with steeply sloping fronts indicate that the crater rims comprise high‐viscosity silicic lavas, while the structurally controlled inner crater walls suggest caldera collapse triggered by magma depletion. In the crater rims, low Christiansen Feature position values reaffirm the presence of silicic lithologies, consistent with the low gravity anomaly signature beneath the complex, while spectroscopic data reveal low mafic mineral abundances and negligible hydration features. Chronological analyses yield silicic volcanism ages coeval with surrounding mare basalts (3.8–3.6 Ga), while intra‐caldera basalts have 2.36–2.02 Ga ages, indicating prolonged magmatism in this region. Melting of suitable crustal protoliths like alkali gabbronorite/monzogabbro/troctolite by basaltic underplating is inferred to have generated silicic magmas that formed the Wolf volcanic complex, instead of basaltic magma fractionation or silicate‐liquid immiscibility processes. Large impacts during the Late Heavy Bombardment may have enhanced partial melting of the mantle and created crustal fractures that facilitated the ascent of viscous silicic melts through the lunar crust. Contemporaneous existence of suitable protoliths and adequate crustal pathways for magma ascent may have controlled silicic volcanism on the Moon, and can explain the sporadic occurrence and overlapping ages of the lunar silicic constructs.

Correction to: Pb Isotope Signature of a Low-μ (238U/204Pb) Lunar Mantle Component

Correction to: Pb Isotope Signature of a Low-μ (238U/204Pb) Lunar Mantle Component

Lunar mantle composition and timing of overturn indicated by Mg# and mineralogy distributions across the South Pole-Aitken basin

The South Pole-Aitken (SPA) basin, excavating more than 100 km depth, must have exposed extensive lunar mantle materials, making it a promising location for sampling mantle material. To investigate the distribution of potential mantle materials across the SPA basin, we mapped the distribution of Mg# and major minerals contents using Moon Mineralogy Mapping data and radiative transfer modeling. We found that the potential mantle material exposed by SPA is Mg-rich orthopyroxenite, and we identified the locations of seven mantle candidate sites. The Chang'E-6 sample return site is located near mantle candidate sites within the Apollo basin, making it promising to return the first unambiguous mantle sample. Our Mg# and mineral mapping results show that the SPA ejecta is enriched in low-Ca pyroxene (LCP) with Mg#≥85, consistent with a post-overturn upper mantle composition. The enrichment of LCP in the SPA upper mantle may result from a low content of dunite or incomplete overturn.

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.

Crustal-mantle layering deposits in the Von Kármán crater, South Pole-Aitken basin

Comprehending the properties of the Moon's crust and mantle materials is essential for decoding its interior. Whether the South Pole-Aitken (SPA) basin potentially excavated the upper mantle materials remains mysterious. The Chang'E Four Lunar Penetrating Radar (LPR) has provided an unprecedented opportunity to investigate the SPA basin in the Von Kármán (VK) crater. Utilizing a data-driven generative deep learning inversion algorithm, the subsurface physical properties along the Yutu-2 path were determined. 4 distinct deposit zones were discovered beneath the surface. All zones feature an upper low-permittivity (paleo-)regolith layer overlaying on a lower high-permittivity layer of rockier ejecta or basal basalt. Zone 1, an ejecta layer from the Finsen crater within the SPA Compositional Anomaly, has a bulk density (2.81±0.22g/cm3) denser than that of highland crust represented by materials originating from VKL and VKL' craters in the Mg-Pyroxene Annulus, which are present in Zones 2 and 3. This suggests the possible presence of mantle materials in Zone 1, providing the first diagnostic evidence that the SPA impact may have penetrated the upper lunar mantle.

Crustal origin for olivine in the lunar Shioli crater ejecta boulders: Insights from the geological setting of Theophilus crater and Nectaris basin

On the Moon, impact craters and basins expose a wide range of crustal and mantle rocks that provide excellent opportunity for sampling them, understanding their origins and reconstructing spatial and temporal evolution of lunar interior. The previous studies detected olivine-bearing mantle rocks in and around large impact craters and basins. The Japanese SLIM mission landed on the ejecta of a ∼ 280-m-diameter Shioli crater that was emplaced on the ejecta blanket of ∼ 103-km-diameter Theophilus crater, for characterizing potential mantle-derived olivine in the Shioli crater ejecta boulders. To test this hypothesis, we studied the geological setting of Shioli crater, host Theophilus crater and Nectaris multi-ring basin using the orbiter data from Chandrayaan-1 and 2, Lunar Reconnaissance Orbiter, and Kaguya missions and the earth-based Arecibo radar observation. The asymmetrically distributed secondary craters and impact melt ponds around Theophilus crater suggests that a northeast-directed oblique impact produced this crater. Composition of Theophilus crater and surrounding region indicates that the crater excavated a heterogeneous target composed of a thin layer of high-Al olivine basalt (Mare Nectaris) underlain by anorthositic highland rocks possibly intruded by Mg-suite plutons; layers of Cyrillus crater ejecta blanket and Nectaris basin materials (both ejecta and impact melt sheets) were also present beneath the mare basalt flows. Hence, the Theophilus ejecta blanket is a mixture of all these materials. Our dating of Theophilus crater suggests that it is a ∼ 2 Ga Eratosthenian crater. Shioli is a fresh simple crater that was formed at ∼ 1 Ma on the uprange ejecta blanket of Theophilus, where the Arecibo radar data indicated the presence of abundant buried Theophilus ejecta boulders. An ESE-directed hypervelocity oblique impact event produced the elongated Shioli crater and its asymmetrically distributed bright ejecta. Shioli is a primary impact crater indicating the role of impact spallation processes associated with this hyper-velocity impact in producing thousands of ejecta (or spall) boulders around Shioli crater, displaying their asymmetric dispersal pattern and spatial variation of boulder sizes and shapes. The larger and elongated boulders are concentrated near the crater rim, while their size and axial ratio gradually decreases outward from the crater rim. The SLIM mission landed on a thin downrange ejecta of Shioli crater, where fewer large-size boulders are present. Our compositional study suggests that the Shioli ejecta boulders are composed of olivine basalt (Mare Nectaris) mixed with highland anorthositic fragments, including the reworked Cyrillus ejecta and Nectaris basin materials. The Shioli ejecta boulders were produced by complex impact fragmentation of already existing, buried Theophilus ejecta boulders. The regional crustal structure of Nectaris basin and its petrological composition suggest that both Nectaris basin and Theophilus crater did not excavate the lunar mantle. Therefore, the Shioli ejecta boulders are of crustal origin, including the olivine minerals present in them. Our results have important implications for the origin of olivine in the Shioli crater boulders being investigated by the SLIM mission.

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.