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Lunar regolith is the most abundant resource on the lunar surface, which can be used for in-situ fabrication and repair technologies. Vat photopolymerization-based additive manufacturing is among the most promising techniques, capable of producing precise ceramic parts of complex shapes from the lunar regolith feedstock for the needs of future crewed exploration missions to the Moon. One of the under-studied aspects of additive manufacturing with lunar regolith is the pre-and post-treatment procedures, which would ensure optimal energy and material consumption and the best printing performance. The goal of the present article was to define the influence of the mineral composition of lunar regolith simulants and the parameters of their pre-processing on the properties of sintered regolith ceramics. It was found that the highland regolith could be sintered to higher relative density compared to the mare regolith. The optimal sintering temperature was determined to be 1150 °C for both types of lunar regolith. An optimal mineral and fractional composition for the regolith feedstock was determined based on the trade-off analysis between lunar regolith sinterability and its printability via vat photopolymerization-based additive manufacturing. Vat-polymerization was performed to produce complex-shaped ceramic parts, yielding 95 % of relative density and a mean ultimate flexural strength of 106 ± 5 MPa, confirming the proposed trade-off point. [ABSTRACT FROM AUTHOR]

Subducting oceanic plates carry large amounts of carbon into the Earth's interior. The subducted carbon is mobilized by fluid and encounters ultramafic rocks in the mantle wedge, resulting in changes to the mineral assemblage and mechanical properties of the mantle. Here, we use thermodynamic modeling of interactions between carbon-bearing multi-component fluids and mantle rocks to investigate the down-dip variation in mineral assemblage in the forearc mantle along subduction megathrusts. We found that fluids rich in aqueous carbon are preferentially generated in a warm subduction zone (e.g., Nankai, SW Japan), causing a change in mineral assemblage from serpentine-rich at the mantle wedge corner to talc + carbonate-rich at greater depths. The transition caused by the infiltration of aqueous carbon may influence the depth of the boundary between the seismogenic and aseismic zones, and the down-dip limit of episodic tremor and slip. Infiltration of carbon-rich fluids promotes the formation of carbonate minerals and weak minerals in the forearc mantle and influences the down-dip limit of seismic zones, according to thermodynamic calculations between fluid and mantle rocks. [ABSTRACT FROM AUTHOR]

Constructing habitable load-bearing structures on lunar and martian surfaces presents unique challenges, such as the ability to sustain extreme thermal fluctuations and frequent dust storms. A promising paradigm for effecting construction is via in situ resource utilization (ISRU), combined with sintering, wherein locally available regolith is consolidated at high temperatures to make load-bearing structures. This work investigates one route for effecting sintering via intermediate melting of a constituent mineral, termed liquid state sintering, to enhance consolidation in lunar regolith simulants. We work primarily with lunar highland simulant (LHS-1), with supporting comparative investigations of lunar mare dust simulant (LMS-1) and martian global simulant (MGS-1). We first establish a liquid-state sintering protocol above the melting point of the constituent basalt using a combination of differential scanning calorimetry (DSC) and post-consolidation Scanning electron microscopy (SEM). A numerical lattice-based model is used to explain several of the experimental observations, including complex pore-crack interactions in the consolidated bricks, potential strength anisotropy due to shrinkage, resulting crack patterns, and derive an exponential relation between strength and porosity. [ABSTRACT FROM AUTHOR]

Lunar regolith on the surface of the Moon has gained great attention as a resource for many proposed lunar exploration projects. Not only is it serving as the ground support for construction projects on the Moon, but it is also the most accessible construction material for building the human habitat and a key component in in-situ resource utilization efforts. Therefore, gaining a fundamental understanding of the characteristics of lunar regolith is a critical step in the success of lunar exploration projects. However, it is challenging and expensive to obtain samples of lunar regolith directly, or conduct physical experiments on lunar regolith samples in situ. Hence, investigative alternatives, such as laboratory experiments and numerical simulation tools are very important means of investigating the properties of lunar regolith. This paper presents a comprehensive study on lunar highlands simulant (LHS-1), using both laboratory experimentation and discrete element method (DEM) simulations. In the laboratory experiment, triaxial tests were conducted on samples of LHS-1 to explore the stress–strain behaviors of the lunar regolith simulant. Correspondingly, 3D DEM simulations of the triaxial tests were conducted to generate the initial model parameters and the Taguchi method was performed to obtain the optimal calibrated input parameters of the DEM model. With the calibrated parameters, 3D DEM model of the cone penetration into LHS-1 was then built to study the responses of the regolith simulant during the penetration process. The effects of porosity and vertical stress on the tip resistance and sleeve friction profiles were investigated for both terrestrial and lunar environments to study the correlation between the in-situ state of the regolith simulants with the force reactions during the penetration. • Geotechnical properties of LHS-1 simulants were characterized using a set of laboratory tests. • Triaxial tests were used to calibrate contact parameters of DEM models using Taguchi method. • Cone penetration simulations were performed using discrete element modeling. • Correlation between penetration responses and in-situ state of regolith simulants was evaluated. [ABSTRACT FROM AUTHOR]

In recent decades, the interest of the scientific community in plant space biology increased based on the certainty that cultivating higher plants in space is imperative for prolonged human missions. The cultivation of plants in space assumes great relevance moved by the consideration that there is a pivotal need to improve resource regeneration and onboard production of plant-based food, thus reducing the supply of resources from Earth. Therefore, the hereby paper provides an overview on the evolution of the interest in plant space biology from 2000 to 2023, basing the search on specific keyword combinations. The study encompasses (i) a proper quantitative search on the Scopus database; (ii) keyword frequencies and clustering analysis, (iii) a keyword network and time-gradient analysis and (iv) an elaboration of knowledge gaps comparing our results and recent reviews. Results highlighted an increase in publications in the last 10 years and a specific time-gradient related shifting on subtopics such as in situ resource utilization (ISRU) application and food production in a space mission context. Currently, knowledge gaps were identified in four research areas related to water dynamics in extra-terrestrial environments, plant physiology and biochemistry in response to growth on regolith, interactions with fertilizers, and plant/soil microbiome. Identifying these gaps will allow to canalize future efforts of space research where needed, facing the unsolved questions. Our analysis pointed out that space plant biology turned out to be oriented towards short and long-term space mission applications for improving resource regeneration and onboard/extraterrestrial-grounded production of plant-based food, thereby diminishing reliance on Earth for resupply. • The scientific community's interest in plant space biology increased in the perspective of prolonged human missions. • The bibliometric analysis highlighted a general increase in publications in the last ten years. • Publications shifted their focus on subtopics such as ISRU application and food production in a space mission context. • Main identified knowledge gaps are water dynamics in space, plant growth on mars-like soils, and plant/soil microbiome. [ABSTRACT FROM AUTHOR]

The development of devices for the in situ resource utilization (ISRU) of lunar surface powder (regolith) by means of microwaves needs regolith simulants with electromagnetic properties similar to the lunar regolith. This document deals with the measurement of complex permittivity and dielectric loss tangent of the aforementioned simulants at ambient temperature from 400 MHz to 20 GHz, performing measurements using two lunar dust simulants, EAC-1A and JSC-2A, resulting, on the one hand, in permittivity values of ε ′ = − 0.0432 f + 4.0397 for the EAC-1A lunar dust simulant and ε ′ = − 0.0432 f + 4.0397 for the JSC-2A simulant, and on the other hand, in loss tangent values of t a n δ e = − 0.0015 f + 0.0659 for the EAC-1A powder and t a n δ e = − 0.0039 f + 0.1429 for the JSC-2A powder. In addition, further studies are carried out taking into account the humidity of the samples and their densities at room temperature. The obtained results are applicable for comparing the measured values of EAC-1A and JSC-2A between them and with other previously measured simulants and real samples. The measurements are carried out by applying two different nonresonant techniques: Open-Ended Coaxial Probe (OECP) and transmission line. For this purpose, the DAK and EpsiMu commercial kits are used, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a general strategy for tracking the scale-span movement process of asteroid regolith materials. It achieves the tracking of the mass movement on the asteroid at a realistic scale, under conditions of high-resolution asteroid surface topography (submeter level) and actual regolith particle sizes. To overcome the memory exponential expansion caused by the enlarged computational domain, we improved the conventional cell-linked list method so that it can be applied to arbitrarily large computational domains around asteroids. An efficient contact detection algorithm for particles and polyhedral shape models of asteroids is presented, which avoids traversing all surface triangles and thus allows us to model high-resolution surface topography. A parallel algorithm based on Compute Unified Device Architecture for the gravitational field of the asteroid is presented. Leveraging heterogeneous computing features, further architectural optimization overlaps computations of the long-range and short-range interactions, resulting in an approaching doubling of computational efficiency compared to the code lacking architectural optimizations. Using the above strategy, a specific high-fidelity discrete element method code that integrates key mechanical models, including the irregular gravitational field, the interparticle and particle-surface interactions, and the coupled dynamics between the particles and the asteroid, is developed to track the asteroid regolith mass movement. As tests, we simulated the landslide of a sand pile on the asteroid's surface during spin-up. The simulation results demonstrate that the code can track the mass movement of the regolith particles on the surface of the asteroid from local landslides to mass leakage with good accuracy. [ABSTRACT FROM AUTHOR]

A number of regolith-hosted REE occurrences have recently been discovered in the Esperance region in southern Western Australia. This paper summarizes major characteristics of REE mineralization and discusses contributing factors and potential controls. The main aim is to explain why there is a lack of highly sought-after ion-adsorption-clay-type REE deposits across the region despite the presence of the regolith-hosted REE mineralization on a regional scale. Local mineralization mostly occurs as continuous flat-lying enrichment "blankets" within the residual regolith developed over Archaean–Proterozoic granite gneisses and granitoids with elevated REE content. The enriched horizon is commonly located in the lower saprolite and saprock and is accompanied by an overlying REE-depleted zone. This distribution pattern, together with the data on HREE fractionation and the presence of the supergene REE minerals, indicates chemogenic type enrichment formed by supergene REE mobilization into groundwater, downward transport, and accumulation in the lower part of the weathering profile. Residual REE accumulation processes due to bulk rock volume and mass reduction during weathering also contribute to mineralization. It is proposed that climate and groundwater chemistry are the critical regional controls on the distribution of REEs in the weathering profile and on their speciation in the enrichment zone. Cenozoic aridification of climate in southwest Australia heavily overprinted pre-existing REE distributions in the weathering profile. Acidic (pH < 4), highly saline groundwaters intensely leached away any relatively weakly bound, adsorbed or colloidal REE forms, moving them downward. Dissolved REEs precipitated as secondary phosphates in neutral to alkaline environment at lower Eh near the base of the weathering profile forming the supergene enrichment zone. Low denudation rates, characteristic of areas of low relief under the arid climate, are favourable for the preservation of the existing weathering profiles with REE mineralization. [ABSTRACT FROM AUTHOR]

Ashes from various Polish coal-fired power plants were analysed in this investigation as the source material for preparing simulants of lunar regolith. The chemical and phase constituents were the most important parameters used to describe these ashes. The second parameter was particle size and morphology, specifically characterising technological properties such as flowability or density. The final element of the investigation was related to the characterisation of thermal properties. Differential thermal analysis yields information on phase transitions, melting temperatures and other characteristic temperatures of stimulants. Thermogravimetry with Fourier transform infrared analysis provides information on evolved gas species and their evolution temperature profiles. [ABSTRACT FROM AUTHOR]

The Chinese small body exploration mission Tianwen-2 is aimed at sampling the near-Earth, fast-rotating asteroid (469219) Kamo'oalewa and returning the samples to Earth. Characterisation of the currently unknown physical properties of Kamo'oalewa in the pre-mission phase would support mission implementation. In this study, we preliminarily estimate the surface thermal inertia of Kamo'oalewa using a statistical method, based on the Yarkovsky-related orbital drift of (–6.155 ± 1.758) × 10-3 au/Myr for Kamo'oalewa obtained in our previous work. A reasonable estimate of the surface thermal inertia obtained is J K–1 m–2 s–1/2. This low value suggests the presence of coarse regolith on the surface of Kamo'oalewa or its nature as a porous rock. The regolith potentially present on the surface of Kamo'oalewa may have millimetre- to decimetre-sized grains with cohesive strengths varying from ~0.76 to ~0.045 Pa. If Kamo'oalewa is a porous rock, its porosity is expected to range from ~20 to 50%, corresponding to tensile strengths of ~1.3 to 11.5 MPa. This study provides preliminary insights into the surface thermal inertia of Kamo'oalewa from a statistical viewpoint, which may facilitate the Tianwen-2 mission. [ABSTRACT FROM AUTHOR]

Based on the measurements of regolith thicknesses on the lunar maria (basalts), the lunar regolith was determined to have accumulated at a rate of about 1 m/Gyr since the era of the late heavy bombardment. However, regolith production on porous targets (e.g., crater ejecta deposits) is less studied, especially for Copernican units, and how target properties affect regolith production is not well understood. Here, we measured regolith thicknesses on the ejecta blanket of the Copernicus crater, showing that the regolith production rate sensitively depends on the initial target properties. The regolith production rate of the Copernicus ejecta blanket (3.0 ± 0.1 m/Gyr) is significantly larger than that of the Copernicus impact melt, which was previously estimated to be 1.2 ± 0.2 m/Gyr. Although crater production varies with different targets, our observed crater density of the Copernicus impact melt is indistinguishable from that of the Copernicus ejecta because impacts fracture the melt, causing it to resemble the ejecta. However, due to the fact that the formation of crater ejecta had already caused them to undergo fragmentation, ejecta require fewer fragmentation times to become regolith compared to impact melt; thus, the growth of regolith on the ejecta is faster than the melt. This indicates that similar observed size–frequency distributions do not indicate similar regolith production, especially for the targets with significant differences in initial physical properties. [ABSTRACT FROM AUTHOR]

The lunar surface exhibits noticeable variations in photometric properties across different regions, influenced by their specific compositional and physical characteristics. These variations are particularly pronounced at the millimeter to centimeter scale. In this study, we propose a feature subspace-based sample selection method to identify Chang'E-4 Visible Near-infrared Imaging Spectrometer (CE-4 VNIS) in situ observations that share similar photometric properties at the centimeter scale. By constructing a feature subspace through principal component transformation, the CE-4 VNIS observation sites with comparable surface photometric properties are able to be selected from a series of observations. The selection results demonstrate that the majority of observation sites are covered by the lunar regolith, with a few exceptions consisting of rocks, soil bulk, shadows, and rough surfaces. These observations should be excluded from the photometric correction process during phase function fitting. Analyzing the photometric performance of the VNIS data with lunar regolith reveals that reflectance decreases as the phase angle increases below 80°, while above 80°, reflectance increases with increasing phase angle. This phenomenon is likely attributed to stronger forward scattering. Thus, a second-order polynomial is employed to fit the phase function for VNIS data. Consequently, a photometric model is developed for lunar regolith observed by CE-4 VNIS, incorporating the fitted phase function. Experimental results demonstrate reduced differences among observations with varying phase angles, and the corrected VNIS spectra exhibit a phase-reddening effect. These findings validate the effectiveness of the proposed model. A comparison between the corrected data with and without sample selection reveals a 33 % decrease in mean standard deviation for VIS/NIR bands and a 19 % decrease for SWIR bands in the corrected spectra after sample selection. These results indicate the potential applicability of our method for future VNIS observations, enabling the acquisition of photometrically consistent data. [ABSTRACT FROM AUTHOR]

The Don terrane, which is extensively reworked by metamorphism and granitoid intrusions, is part of the Volga–Don orogen stretching along the eastern margin of the Sarmatian segment of the East European Craton. The terrane consists of gneiss-granites of the Pavlovsk complex, metavolcanic rocks, ranging from basaltic andesites to dacites (amphibolites and gneisses), and metasedimentary rocks (marbles and calc-silicate rocks) of the Don Group. The volcanic rocks are typically enriched in LILE and LREE and show negative HFSE anomalies, indicating fluid-assisted melting of the mantle wedge in a subduction zone. The Nd isotopic composition (εNd2200 = –1.2 to +3.4, model age 2180–2550 Ma) and Hf isotopic composition (εHf = –4.3 to +3.3, model age 2290–2640 Ma) indicate an enriched mantle or a mixed crustal–mantle source of the parental melts of the volcanics and a juvenile source for sediments of the Don Group. The U–Pb zircon metamorphic age of the gneisses and amphibolites is 2047 ± 7 Ma, and that of the thermal effect of the granitoid batholith on the host rocks is 2060 ± 4 Ma. According to isotope geochemical and geochronological data, the Don Group is underlain by Archean rocks, contains Archean detrital zircons, but the age of this group is no older than 2300 Ma. A facies and age analogue of the Don Group is the Temryuk Formation of the Central Azov Group of the Ukrainian shield. In the Paleoproterozoic, the eastern margin of Sarmatia was likely a continental arc, which was nearly coeval with the island arc–backarc basin system of the Losevo Group. [ABSTRACT FROM AUTHOR]

Lunar exploration has captivated significant attention in recent times through programs such as Artemis. To establish long-term sustenance on the moon, astronauts have to grow their food on-site. While a key substrate for plant production – lunar regolith can induce baneful effects, supplementation with organic amendments could alleviate this inherent toxicity and significantly improve plant growth. In the present study, we examined the suitability of cocopeat (CP) as an amendment to ISRO's lunar soil simulant (LSS), LSS-ISAC-1. We assessed the germination and seedling growth response of four crops—wheat, tomato, groundnut, and cotton to LSS and Cocopeat supplementation. As anticipated, all four crops grew very well on earth soil (ES) and CP per se compared to the LSS. However, due to acidic pH, low electric conductivity (EC), and severe nutrient deficiency in LSS, we observed significantly low germination, stunted seedling growth, and altered associated oxidative stress indicators. To mitigate these pernicious effects, LSS supplemented with varied CP proportions – 3.125, 6.25, 12.50, 25, 50, and 100 %. The resultant data revealed that LSS supplemented with 6.25 % CP in wheat and tomato; 3.125 % CP in groundnut, and 25 % CP in cotton significantly improved phenotypic and biochemical traits in seedlings. Collectively, this study suggests the utility of CP as a novel augmenting agent to boost ISRU strategy for crop growth in moon regolith. • ISRO's Lunar soil simulant , LSS-ISAC-1, significantly reduced germination and seedling growth. • Cocopeat alleviated the LSS-induced baneful effects on wheat, tomato, groundnut, and cotton crop seedlings. • Cocopeat can be a novel augmenting agent to boost ISRU strategy for crop growth in moon regolith. [ABSTRACT FROM AUTHOR]

Water and other volatiles are present in the permanently shadowed region of the moon. Quantitative analysis of the content is of great significance for lunar resource assessment and geological evolution. However, no detector has yet carried out in situ analysis on the moon, and quantitative sampling and low-power thermal extraction of lunar regolith are also difficult. Thus, a systematic method is proposed to realize quantitative sampling & low power thermal extraction of lunar regolith that detects the abundances of volatiles more accurately. Considering the requirements of the amount and particle size of the regolith, a sampler with a specific structure and motions is designed to quantitatively collect some lunar regolith. After that, induction heating is applied to heat the sampler and indirectly increase the temperature of the internal lunar regolith for volatile thermal extraction. The results demonstrate that this sampling method can achieve high-quality quantitative sampling. Moreover, the sampler and sampled regolith can be heated to the desired temperature with low power consumption. This work offers a feasible solution for the lunar volatile exploration of Chang'E-7. • A method to quantitative sampling and heating lunar regolith is proposed. • Sampling method can realize a quantitative collection of lunar regolith. • Sampled lunar regolith can be heated to 900℃ with low power. [ABSTRACT FROM AUTHOR]

Lunar water ice resources are important space assets for human survival and sustainable living on the Moon. Detection data indicates that the permanently shadowed regions at the lunar poles contain water ice resources. The efficiency of in-situ extraction of lunar water ice resources depends on its volatile characteristics. In the context of extraction and utilization of water ice resources in the permanently shadowed regions, the sublimation and diffusion processes of lunar water ice are investigated by combining the theory of pure ice sublimation with the fractal theory of porous media. On this basis, a volatilization model for lunar water ice is established to examine the effect of temperature, relative density, and water content on the volatile behaviors of lunar water ice. The findings of this study can provide technical and theoretical support for the in-situ exploration, extraction, and utilization of lunar water ice resources and offer insights into the existence and distribution of lunar water ice resources. • Apply the fractal theory of porous media on the research of icy lunar regolith volatilization. • Establish a volatilization model of water ice within icy lunar regolith. • Investigate the effect of temperature, relative density, and water content on volatilization. • Provide technical support for the exploration and extraction of lunar water ice resources. [ABSTRACT FROM AUTHOR]

Solar irradiance received at the lunar surface is crucial for interpreting brightness temperatures detected by orbiters and for understanding the thermal, physical, and dielectric properties of the lunar regolith. We developed a real‐time effect solar irradiance (ESI) model that accounts for the influence of surface relief and terrain shading. This model was integrated with a standard thermal model to examine ESI fluctuations and their impacts on the diurnal physical temperature variations. To assess the effects of spatial resolution, we selected four locations with significant ESI disparities for simulation, then compared lunar surface temperatures at various spatial scales, ranging from 20 m to 25 km. Utilizing brightness temperature data obtained from the Chang'E‐2 (CE‐2) microwave radiometer (MRM), we integrated the shallow physical temperature profiles with the radiative transfer equation to simulate brightness temperatures and determine dielectric loss at different frequencies. In the Von Kármán crater, the received ESI exhibits a cyclical pattern of approximately 18 years and areas with rugged topography may exhibit larger ESI variations (∼7%). We found that the spatial resolution of ESI has a minimal effect on the physical and brightness temperatures at resolutions of 10 km or coarser. At the shallow layer, the average dielectric loss values are 0.0128–0.0170, 0.0083–0.0110, 0.0055–0.0073, and 0.0061–0.0081 for the CE‐2 frequencies of 3, 7.8, 19.35, and 37 GHz, respectively. The integration of real‐time ESI modeling, thermal dynamics, radiative transfer equations, and observational data enhances our comprehension of the physical temperature profile and thermal characteristics of shallow regolith. Plain Language Summary: The combination of solar irradiance and temperature data sets detected by orbiters can help to explain the temperature variation and thermophysical properties of shallow lunar surface. This study develops a real‐time effect solar irradiance (ESI) model that takes into account the influence of lunar topography and integrates it with a thermal model to simulate physical temperature variations within the Von Kármán crater. We compared lunar surface physical temperature profiles at spatial resolutions of 20, 240, 500 m, 1, 5, 10, 15, and 25 km, each exhibiting distinct ESI characteristics, to assess the impact of spatial resolution. We then simulated the temperature data in the four frequencies consistent with Chang'E‐2 (CE‐2) microwave radiometer and obtained the average ranges of dielectric loss. At 3, 7.8, 19.35, and 37 GHz, the average dielectric loss ranges were determined to be 0.0128–0.0170, 0.0083–0.0110, 0.0055–0.0073, and 0.0061–0.0081, respectively. These findings provide valuable insights for analyzing lunar surface temperature and observed brightness temperature, as well as for inverting physical and dielectric properties of the shallow regolith (e.g., dielectric loss). Key Points: Analyzing lunar shallow temperature variation with real‐time effect solar irradiance (ESI) model considering terrain influenceAssessing the real‐time ESI impact on physical and brightness temperature curves at diverse spatial resolutionsEstimating the dielectric loss of shallow regolith by coupling simulated brightness temperature data with observations [ABSTRACT FROM AUTHOR]

Drilling is a widely used method for exploring extra-terrestrial bodies and seeking information on astrobiology, material composition, and evolution of the universe. The bit cutter of the drill tool is the main component that is in intense contact with the regolith and is of great importance for guaranteeing the cutting performance during drilling. The tine is a special type of cutter, and currently, there is no theoretical model describing its interaction with a lunar regolith simulant during cutting. To address this gap, semi-tine and full-tine cutting tests were performed at different cutting speeds, cutting depths, regolith densities, and tip angles. The experimental results showed that the regolith failure zone has an elliptical shape in the top view and a logarithmic spiral shape in the side view. Based on the failure pattern, a tine cutting mechanics model was built, and its results were compared with those of the experiments. The model exhibited good prediction accuracy for the cutting force, with a maximum error not exceeding 30.96 % and an average error of 13.81 %. To apply the model to extra-terrestrial drilling, a conical drill bit with multi-row serrated tines was designed. By analyzing the error between the theoretical and experimental values of the rotational torque, the model was further refined to provide a better match with the actual cutting results. The proposed cutting mechanics model describing the tine-regolith interaction mechanism can provide a reference for predicting drilling loads during planetary exploration. [ABSTRACT FROM AUTHOR]

The prospect of establishing extra-terrestrial habitats using in situ resource utilization (ISRU) constitutes a long-term goal of multiple space agencies around the world. In this work, we investigate furnace sintering as a potential route for making building blocks—termed synthetic space bricks—using in situ regolith material. By systematically evaluating sintering parameters using a numerical lattice model, coupled with experimental observations and post-sintering characterization, we propose a process protocol for two lunar simulants (lunar highland simulant (LHS-1) and lunar mare dust simulant (LMS-1)) and one Martian simulant (mars global simulant, MGS-1). The resulting bricks demonstrate compressive strengths of up to 45 MPa under uniaxial loading, depending on the simulant used. These strengths are much greater than those typically mandated for structural applications under reduced gravity. Taking recourse to classical ceramic sintering studies, we infer particle-level sintering mechanisms indirectly by measuring temporal evolution exponents of sample dimensions. For all three simulants, volume diffusion appears to be the primary mechanism for particle coalescence. Our results clearly make a strong case for the use of sintering as a potentially scalable method for consolidating regolith into brick-like structures for construction and load-bearing applications in extra-terrestrial settings. [ABSTRACT FROM AUTHOR]

• Advances in extraterrestrial resource utilization is reviewed from the aspect of in-situ construction. • Three construction-related in-situ resources are comprehensively reviewed. • Five in-situ construction technologies are sorted and elucidated. • Advice is given for deep, comprehensive and systemic utilization of in-situ resources. To establish foundational support for forthcoming deep space exploration and settlement endeavors, the significance of extraterrestrial construction has become paramount. Recent developments underscore a growing acknowledgment of the imperative role played by in situ resource utilization, attributed to its potential for cost efficiency and facilitation of sustainable progress. This paper compiles and categorizes the advancements in this domain, focusing on three distinctive categories of in situ resources: regolith, water–ice, and energy resources. A review of their distribution, acquisition, and utilization procedures is presented. Subsequently, an intricate examination ensues, elucidating the applicability of each resource within the context of extraterrestrial construction, in conjunction with five prevalent technologies and the latest architectural constructs. Drawing insights from the research, the existing limitations are identified, particularly pertaining to the comprehensive, deep processing, and sustainable utilization of resources. Consequently, a proposition is put forth to address these challenges. Prospective investigations are recommended, focusing on the mining of water–ice, the metallurgy and production of regolith and slag, and the integrated construction in the pursuit of extraterrestrial construction and operational endeavors. [ABSTRACT FROM AUTHOR]

The stratiform and vein-hosted Kapunda Cu deposit in South Australia contains a saprolitized hydrothermal vein with 12.37 wt.% total rare earth oxide (TREO). The vein was analyzed by X-ray diffraction, scanning electron microscopy, synchrotron-based X-ray fluorescence microscopy and electron backscatter diffraction to understand the controls that govern high-grade REE accumulation during periods of intense weathering. Petrological assessments indicate the transformation of an apatite-calcite-aluminosilicate-bearing protolith to a supergene assemblage of Fe-oxides, kaolinite and REE-phosphate minerals that include rhabdophane-(Ce), monazite-(Ce) and florencite-(Ce). This transformation was facilitated by progressive acidification of the weathering fluid, which is indicated by: 1) the increasing crystallinity of authigenic Fe-oxides and kaolinite, which led to REE desorption; 2) the textural evolution and increase in grain size of authigenic REE-phosphates from nanoscopic crystallites, to acicular needles, to micro-scale hexagonal prisms; 3) the late dissolution of REE-phosphates; and 4) the replacement of goethite by jarosite, whose sulfate component originated from the oxidation and weathering of proximal sulfide minerals. Alongside the depletion of pH-buffering carbonate minerals that are indicated by the preservation of calcite menisci, this sulfide dissolution also facilitated acid generation. Results illustrate how highly acidic weathering fluids might facilitate either REE mobilization or REE accumulation in regolith. High-grade REE accumulation under acidic supergene conditions is prioritized when the host-rock contains a significant source of depositional ligands (i.e., phosphate in the form of apatite) that can be readily leached during intense weathering. Exploration companies should therefore assay routinely for REEs in any heavily weathered phosphatic rock, due to the observed efficiency of phosphate minerals as geochemical traps for REE accumulation. [ABSTRACT FROM AUTHOR]

Nowadays, the trend in lunar exploration missions is shifting from prospecting lunar surface to utilizing in-situ resources and establishing sustainable bridgehead. In the past, experiments were mainly focused on rover maneuvers and equipment operations. But the current shift in trend requires more complex experiments that includes preparations for resource extraction, space construction and even space agriculture. To achieve that, the experiment requires a sophisticated simulation of the lunar environment, but we are not yet prepared for this. Particularly, in the case of lunar regolith simulants, precise physical and chemical composition with a rapid development speed rate that allows different terrains to be simulated is required. However, existing lunar regolith simulants, designed for 20th-century exploration paradigms, are not sufficient to meet the requirements of modern space exploration. In order to prepare for the latest trends in space exploration, it is necessary to innovate the methodology for producing simulants. In this study, the basic framework for lunar regolith simulant development was established to realize this goal. The framework not only has a sample database and a database of potential simulation target compositions, but also has a built-in function to automatically calculate the optimal material mixing ratio through the particle swarm optimization algorithm to reproduce the target simulation, enabling fast and accurate simulant development. Using this framework, we anticipate a more agile response to the evolving needs toward simulants for space exploration.

We find strong path dependence in the evolution of the Plio--Pleistocene glaciations using CLIMBER-2 Earth System Model simulations from the mid-Pliocene to modern preindustrial (3 My-0 My BP) driven by a gradual decrease in volcanic carbon dioxide outgassing and regolith removal from basal ice interaction. Path dependence and hysteresis are investigated by alternatively driving the model forward and backward in time. Initiating the model with preindustrial conditions and driving the model backward using time-reversed forcings, the increase in volcanic outgassing back-in-time (BIT) does not generate the high CO2 levels and relatively ice-free conditions of the late Pliocene seen in forward-in-time (FIT) simulations of the same model. This behavior appears to originate from nonlinearities and initial state dependence in the carbon cycle. A transition from low-amplitude sinusoidal obliquity (~41 ky) and precession (~23 ky) driven glacial/ interglacial cycles to high-amplitude ~100 ky likely eccentricity-related sawtooth cycles seen between -1.25 My and -0.75 My BP (the Mid-Pleistocene transition or "MPT") in FIT simulations disappears in BIT integrations depending on the details of how the regolith removal process is treated. A transition toward depleted regolith and lowered atmospheric CO2 levels are both required to reproduce the MPT. [ABSTRACT FROM AUTHOR]

We present a framework to study regolith segregation on rubble-pile asteroids—self-gravitating granular aggregates—due to seismic shaking induced by impacts sustained during their lifetimes. We first relate the amplitude and frequency of surface vibrations to the location and severity of an impact, and the rubble body's geometry and bulk properties. For illustration, the body is taken to be an ellipsoid with size and spin close to that of Itokawa, although more complex asteroid shapes may be incorporated. We then model the body's collisional history stochastically given the variability in the impact activity on an asteroid. Finally, we use discrete element simulations to investigate the regolith's response to impacts. In these simulations, in any sample collisional history, every time an impact occurs, a bin filled with a grain mixture and located at the region of interest on the asteroid is vibrated at that impact's associated amplitude and frequency. Using this framework, we find that impact-driven seismicity is sufficient to drive size segregation on small rubble-piles, but the segregation quality depends on several aspects, e.g. total impact energy supplied, placement of the region of interest, bulk wave speed and seismic diffusivity. [ABSTRACT FROM AUTHOR]

Transient creep in olivine aggregates has been studied by stress‐relaxation experiments at pressures of 1.7–3.6 GPa and at temperatures of ≤1020 K in a DIA apparatus. Time‐dependent deformation of olivine at small strains (<0.07) was monitored with an ∼1 s of time resolution using a combination of a high‐flux synchrotron X‐ray and a cadmium telluride imaging detector. The observed deformation was found to follow the Burgers creep function with the transient relaxation time ranging from 50 (±20) to 1,880 (±750) s. We show that the Burgers creep for olivine cannot account for the low viscosities in early post‐seismic deformation reported by geodetic observations (<7 × 1017 Pa·s). In contrast, the time‐dependent increase in viscosity observed in late post‐seismic deformation (1018−1020 Pa·s) is explained by the Burgers rheology, suggesting that the combination of the Burgers model and another model is needed for the interpretation of post‐seismic deformation. Plain Language Summary: Geodetic observations reveal that the deformation of the crust and upper mantle after a great earthquake continues for decades. Viscosities of the upper mantle estimated from early post‐seismic deformation are often significantly low (1017−1018 Pa·s) and continuously increase to a typical value (∼1020 Pa·s). This characteristic of post‐seismic mantle flow cannot be explained by partial melting (nor water weakening) of upper mantle rocks. Here we performed small‐strain deformation experiments on natural olivine, which is the major mineral in the upper mantle, via a state‐of‐the‐art technology large‐volume deformation apparatus combined with high‐flux synchrotron X‐ray observations. We have successfully shown that the reported time‐dependent crustal deformation, which continues for decades after a great earthquake, is explained by the transient creep of olivine. Key Points: In situ deformation experiments on olivine were performed using a high‐flux synchrotron X‐ray and a cadmium telluride imaging detectorTransient creep of olivine aggregates follows the Burgers creep function at upper mantle pressures and temperaturesTime‐dependent rheology of the shallow mantle observed in the late post‐seismic deformation is explained by the Burgers model [ABSTRACT FROM AUTHOR]

The regolith evolution of airless bodies, like the Moon, is primarily controlled by impact cratering. Since the Apollo Era, measurements of cosmic ray exposure (CRE)-induced Sm and Gd isotopes in lunar drill cores have provided insights into the secondary neutron spectra in the lunar regolith. Since the production and transport of secondary neutrons vary with the regolith's chemical composition and depth, the neutron fluence profile can be employed to track the evolution of lunar and asteroidal regolith. We developed a stochastic model that incorporates state-of-the-art cosmogenic production rate calculations for Sm and Gd isotopes in an effort to understand regolith evolution in the presence of meteoroid bombardments. By comparing the simulated depth profiles to those observed in the lunar drill cores from the Apollo 15, 16, and 17 missions, we find that the deviations from a static profile are due to continuous surface meteoroid bombardments. These bombardments result in the formation of nuclear-reworked zones near the lunar surface. Based on the surface neutron fluence of lunar rocks and regolith, our modeling shows that the regolith surface is reset by large impact-induced excavation and deposition of blanket ejecta every few hundred million years. [ABSTRACT FROM AUTHOR]

In the development of lunar and planetary exploration rovers, risk assessment in on-site environments comprising fine regoliths and unevenly distributed rocks is essential. To prevent a rover from being stuck during its operation, one must understand the behavior of its wheel when it climbs over rigid obstacles in off-road environments. In this study, we apply an extended terramechanics model, which can reasonably describe the interaction between soft ground and vehicles, to analyze the obstacle-climbing behavior of rigid wheels. To describe the interaction between the wheel and a hard obstacle, we combine the penalty method with the extended terramechanics model. Subsequently, we verify the effectiveness of the proposed method by comparing its results with those of a traversing single wheel obtained from a laboratory experiment. Furthermore, we use the model to perform a multibody dynamics analysis on a simple rover, where its applicability to the examination of the overall performance of obstacle climbing is demonstrated. [ABSTRACT FROM AUTHOR]

The identification of trace element anomalies in soils has been proven to assist semi-mechanized small-scale gold operations. This study employs soil geochemistry combined with the microchemical signature of particulate gold from the Batouri goldfield to (1) vector possible gold-endowed lithologies introducing particulate gold into the overlying regolith, and (2) assess anthropogenic Hg used in purification of both primary and alluvial/eluvial gold by artisans. The soil geochemistry shows irregularly distributed anomalies of elevated Cu especially in the saprolite soil layer. Whereas in the lateritic soil layer, a Au-Ag-Hg metal association is reported for the first time in this gold district and could be linked to anthropogenic Hg used in gold recovery. Particulate gold recovered from the soil varies in shape from euhedral and irregular to sub-rounded, indicating a proximal lode source. The gold grains range in size from nano-particles to >300 µm and are Au-Ag alloys. The gold particles reveal inclusions such as quartz, silicate, zircon and ilmenite suggesting that the grains were dislodged from quartz veins within the granitic basement. Systematic variation in the microchemical signature of the gold grains is suggestive of spatial and temporal evolution of the mineralizing fluid. These results are consistent with investigations from similar geologic settings worldwide and validate the combined utility of gold fingerprinting and pathfinder elements in soil to examine deposit genesis in other gold districts globally. [ABSTRACT FROM AUTHOR]

The construction of lunar bases represents a fundamental challenge for deep space exploration, lunar research, and the exploitation of lunar resources. In-situ resource utilization (ISRU) technology constitutes a pivotal tool for constructing lunar bases. Using lunar regolith to create geopolymers as construction materials offers multiple advantages as an ISRU technique. This paper discusses the principle of geopolymer for lunar regolith, focusing on the reaction principle of geopolymer. It also analyzes the applicability of geopolymer under the effects of the lunar surface environment and the differences between the highland and mare lunar regolith. This paper summarizes the characteristics of existing lunar regolith simulants and the research on the mechanical properties of lunar regolith geopolymers using lunar regolith simulants. Highland lunar regolith samples contain approximately 36% amorphous substances, the content of silicon is approximately 28%, and the ratios of Si/Al and Si/Ca are approximately 1.5 and 2.6, respectively. They are more suitable as precursor materials for geopolymers than mare samples. The compressive strength of lunar regolith geopolymer is mainly in the range of 18~30 MPa. Sodium silicate is the most commonly utilized activator for lunar regolith geopolymers; alkalinity in the range of 7% to 10% and modulus in the range of 0.8 to 2.0 are suitable. A vacuum environment and multiple temperature cycles reduce the mechanical properties of geopolymers by 8% to 70%. Future research should be concentrated on the precision control of the lunar regolith's chemical properties and the alkali activation efficacy of geopolymers in the lunar environment. [ABSTRACT FROM AUTHOR]

Extracting volatiles from lunar regolith for analysis or utilization is one of the most important aspects of future lunar exploration. However, the low thermal conductivity of lunar regolith poses a challenge. Here, we conduct simulations to analyze the heat and mass transfer processes within the sample inside the oven. We identify three main factors affecting oven heat‐up rate: water ice content (WIC) in the regolith, oven diameter, and power supply. Taking these factors into account, we devise an oven design and apply it to three case studies: (a) assessing water ice and isotopic composition in Permanently Shadowed Regions, akin to Chang'e‐7 mini‐fly probe missions; (b) measuring noble gases, as Chang'e‐7 and Luna‐27 landers; and (c) large‐scale in‐situ resources utilization (ISRU). The simulation results indicate that water ice can be extracted using sufficiently high heating power without issues. However, the complete extraction of noble gases is challenging and may require alternative heating methods. For ISRU purposes, large ovens can be subdivided into smaller ones by adding internal structures, for example, honeycomb, to improve the heat‐up rate by at least 1.5 times. Additionally, we find that the oven can serve as a scientific payload for WIC measurement using the heating curve. A flowchart of this new WIC measurement method is provided, offering an alternative method to mass spectrometry or spectroscopy measurements. Key Points: The paper presents a realistic heating oven design for in‐situ extraction of volatiles from lunar regolithThree factors controlling the oven's heat‐up rate are water ice content (WIC) in regolith, oven diameter, and power supplyThe oven can serve as a scientific payload for measuring the WIC in regolith based on the heating curve [ABSTRACT FROM AUTHOR]

Pitted impact deposits on Vesta show higher reflectance and pyroxene absorption band strengths compared to their immediate surroundings and other typical Vestan materials. We investigated whether heating to different temperatures for different durations of Vestan regolith analog materials can reproduce these spectral characteristics using mixtures of HEDs, the carbonaceous chondrite Murchison, and terrestrial analogs. We find no consistent spectral trend due merely to temperature increases, but observed that the interiors of many heated samples show both higher reflectance and pyroxene band I strength than their heated surfaces. With electron probe microanalysis, we additionally observe the formation of hematite, which could account for the higher reflectance. The presence of hematite indicates oxidation occurring in the sample interiors. In combination with heat, this might cause the increase of pyroxene band strengths through migration of iron cations. The effect grows larger with increasing temperature and duration, although temperature appears to play the more dominant role. A higher proportion of Murchison or the terrestrial carbonaceous chondrite analog within our mixtures also appears to facilitate the onset of oxidation. Our observations suggest that both the introduction of exogenic material on Vesta as well as the heating from impacts were necessary to enable the process (possibly oxidation) causing the observed spectral changes. [ABSTRACT FROM AUTHOR]

Spacecraft missions to asteroids have revealed surfaces that have variations in albedo and spectral properties. Such variations are also detected across the asteroid population with ground‐based observations, and are controlled by the physical characteristics of the regolith and by processes such as space weathering. Here, we investigate how space weathering and regolith grain size influence the spectra of ordinary chondrite‐like asteroids observed from ground‐based spectroscopy. The estimation of diagnostic band parameters from asteroid visible and near‐infrared reflectance spectra allow us to estimate the degree of space weathering and their compositions, using results from an accompanying study (MacLennan et al., 2024). We use grain size estimations gleaned from the thermal inertia to show that regolith particle size differences have similar effect as space weathering on asteroid spectra. Finally, we quantify changes in spectral slope and band depth among asteroids using the space weathering index developed by MacLennan et al (2024), and reassess the importance of previously‐proposed surface freshening mechanisms. [ABSTRACT FROM AUTHOR]

In the experiment, plasma–dust clouds were obtained from the substance of the Tsarev meteorite, a simulant of lunar regolith LMS-1D and ilmenite concentrate using a microwave discharge in powder media. For each of the samples, the dynamics of the development of the discharge and the formation of a plasma–dust cloud with subsequent relaxation after the end of the microwave pulse were recorded. From the emission spectra of the plasma and the surface of a solid body, the temperatures of the gas, electrons and surface were determined. A comparison of the phase and elemental composition of the initial samples and samples after exposure to plasma showed that there is no significant change in the composition. However, scanning electron microscopy results clearly indicate spheroidization of the original angular and irregularly shaped particles. The appearance of spherical particles is also observed, the dimensions of which are larger than the linear dimensions of the particles in the original sample. The results obtained indicate the possibility of using such experiments to study chemical and plasma-chemical processes of synthesis and modification of substances under conditions of plasma–dust clouds encountered in space phenomena. [ABSTRACT FROM AUTHOR]

Perchlorates have been found in the regolith of Mars and the Moon, in the ice of Europa, and in meteorites. Studying the processes of formation and destruction of these compounds is important both for understanding the geological and climatic evolution of a number of planets and bodies of the Solar System, and for assessing their habitability. To date, a number of processes for the synthesis of perchlorates under Martian conditions have been proposed, but these do not explain the perchlorate concentrations observed in the regolith and are not applicable to atmosphereless bodies, in particular Europa. We have studied the processes of synthesis and destruction of perchlorates during irradiation of ice and regolith models with high-energy electrons under conditions of low temperature (–50°C) and in the absence of an atmosphere (at a pressure of 0.01 mbar). The data obtained indicate that perchlorates can be efficiently synthesized in the regolith of Mars and the surface layer of Europa ice under the influence of irradiation in the absence of a liquid phase or an atmosphere. [ABSTRACT FROM AUTHOR]

The article describes simulation experiments of interaction of lunar dust with the surface of solar panels. The experiments are based on the creation of a dusty plasma cloud, when the radiation of a powerful pulsed gyrotron is exposed to a substance that simulates lunar dust. This approach was tested using a lunar regolith simulator. The analysis of the results of deposition of charged regolith particles on solar panels of different types and changes in their efficiency is presented. [ABSTRACT FROM AUTHOR]

The purpose of the work is to build a three-dimensional P-velocity model of the Earth's crust and upper mantle of the territory of Ukraine. The mantle part of the model was created by the thermal model. The methodology includes the use of correlations between velocity and temperature and the presence of melt under different pressure conditions for typical mantle rocks. Such a model was created for the first time. It is based on a previously constructed scheme of deep processes of various ages in the tectonosphere of Ukraine, which primarily takes into account the results of heat and mass transfer during recent activation (RA). Results are superimposed on the models of the platform (the territory of the East European Platform, and the Donbass), the Alpine geosyncline of the Carpathians, and the Hercynian-Cimmerian geosyncline of the Scythian plate. The incomplete process of recent activation cannot be accurately described by the geological theory used by the authors. To select an adequate heat and mass transfer scheme, gravity modelling was previously carried out on a system of profiles around the northern hemisphere with a total length of more than 50,000 km, crossing Eurasia, North America, the Atlantic and Pacific oceans. A process scheme that best corresponds to reality (observed gravitational field) has been identified. The scheme is used for Ukraine, where the activated area is determined with great accuracy. In the south, the model is limited by the Black Sea depression, at a depth of 400 km. Velocities in the transition zone to the lower mantle were not taken into account. The values of P-velocity at each depth in the mantle were determined by the difference in temperature from the background (platform) one. The melt concentration at temperatures above the solidus was considered minimal (about 1.5%). It corresponded to a decrease in velocity by 0.1 km/s. Test velocity models were compared with specially selected independent ones. The error (0.035 km/s) of the calculation and the isoline section (0.1 km/s) for depths from 50 to 150 km are determined. At a depth of 25 km, the model was constructed using DSS data. Error – 0.13 km/s. The cross-section of the isolines is 0.4 km/s. The differences in velocity under the non-activated platform from the centers of recent activation zones reach 0.6 km/s at depths of 50-100 km, 0.1 km/s at depths of 150- 300 km, and 0.2 km/s at depth of 400 km. The results of modelling will make it possible to build schemes of tectonic processes at a more detailed and reasonable level, which will allow us to reliably predict the level and features of the seismic situation for the entire territory of Ukraine. [ABSTRACT FROM AUTHOR]

Recent discoveries of potential ice particles and ice-cemented regolith on extraterrestrial bodies like the Moon and Mars have opened new opportunities for developing technologies to extract water, facilitating future space missions and activities on these extraterrestrial body surfaces. This study explores the potential for water extraction from regolith through an experiment designed to test water recuperation from regolith simulant under varying gravitational conditions. The resultant water vapor extracted from the regolith is re-condensed on a substrate surface and collected in liquid form. Three types of substrates, hydrophobic, hydrophilic, and grooved, are explored. The system's functionality was assessed during a parabolic flight campaign simulating three distinct gravity levels: microgravity, lunar gravity, and Martian gravity. Our findings reveal that the hydrophobic surface demonstrates the highest efficiency due to drop-wise condensation, and lower gravity levels result in increased water condensation on the substrates. The experiments aimed to understand the performance of specific substrates under lunar, Martian, and microgravity conditions, providing an approach for in-situ water recovery, which is crucial for establishing economically sustainable water supplies for future missions. To enhance clarity and readability, in this paper, "H2O" will be referred to as "water". [ABSTRACT FROM AUTHOR]

Safe landings are imperative to accomplish NASA's Artemis goal to enable human exploration on the Moon, including sample collection missions. However, a process known as plume surface interaction (PSI) presents a significant hazard to lunar landings. PSI occurs when the engine exhaust of a lander interacts with the surface ejecting large amounts of regolith particles at high velocities that can interfere with the landing, disturb the surface, and damage hardware. To better understand PSI, the particle impact event (PIE) sensor is being developed to measure the kinetic energy and the flux of ejecta during landings, to quantify the potential damage, and to quantify the ejecta displaced. Multiple parameters were estimated to define the PIE instrument requirements. These estimates demonstrate that ejecta can travel at velocities of up to 800 m/s and impact the surrounding area with energies of up to 400 µJ. A significant amount of ejecta can be deposited several 10 s of meters away from the landing site, modifying the surface and causing dust-related challenges. The PIE sensor will be launched for the first time in an upcoming lunar lander. Then, PIE measurements will be used to improve PSI prediction capabilities and develop mitigation strategies to ensure safe landings. [ABSTRACT FROM AUTHOR]

In streams, short‐term element‐specific solute fluxes are often not balanced with long‐term chemical weathering fluxes determined in the residual solids from fractional element loss and denudation rate. The ratio of both estimates—the "Dissolved Export Efficiency" (DEE)—is frequently <1, indicating deficits in the stream dissolved load. To explore the cause of the stream deficits, we performed a daily water sampling campaign for one year in a forested headwater watershed in Southern Germany. We sampled surface runoff, above‐canopy and below‐canopy precipitation, subsurface flow from the organic soil layer, upper, and deep mineral soil, and groundwater. Regolith samples were obtained from a drill core and revealed the weathering front to lie between 7 and 15 m depth. We found a DEE < 1 for K, Si, Al, Fe. These elements are characterized by shallow slopes in C‐Q relationships, and the imbalances were found to originate in the deep saprolite. Their export pathway potentially includes "hidden" Critical Zone compartments or fluxes, presumably unsampled colloids that are exported preferentially during rare flushing events with stochastic temporal distribution. The DEE of nutritive elements like Ca, Mg, and P is also <1. These elements are characterized by steeper C‐Q slopes, and their imbalance can be explained by deep nutrient uptake followed by nutrient retainment in re‐growing forest biomass or export in plant debris. The collective evidence for these imbalances, including previous evidence from metal stable isotopes, suggests that the deep Critical Zone represents the location for chemical or biogenic retention and release of solutes. Plain Language Summary: Mineral dissolution by chemical weathering produces solutes in the weathering zone that are eventually exported by streams. Yet, often an imbalance between element‐specific solute export fluxes in stream water and element‐specific chemical weathering fluxes determined from residual solids in the weathering zone is apparent. This imbalance is expressed as a deficit in the stream dissolved load. To explore the origin of this deficit, we performed a daily water sampling campaign for one year in a forested watershed in Southern Germany. We studied concentration‐discharge relationships and quantified solute fluxes in stream‐ and groundwater. A comparison of solute fluxes in stream water with chemical weathering fluxes integrating mineral dissolution over the whole weathering zone revealed indeed deficits in the stream dissolved load. These deficits originate in deep isovolumetrically weathered bedrock (saprolite). The elements K, Si, Al, and Fe, which show invariant concentration changes with increasing discharge, may follow a "hidden" export pathway involving colloids that are only mobilized and exported during rare flushing events that were missed during this study's sampling period. Deficits of nutrients (Ca, Mg, P), which show dilution behavior with increasing discharge, can be explained by deep nutrient uptake and retention in growing forest biomass or plant litter erosion. Key Points: Imbalances between short‐term and long‐term estimates of element‐specific chemical weathering fluxes (DEE < 1) emerge in deep saproliteElements with shallow C‐Q slopes showing chemostatic or enrichment behavior are likely exported in colloidal form during flushing eventsElements with steeper C‐Q slopes showing weak dilution behavior remain in re‐growing biomass or are exported in particulate biogenic form [ABSTRACT FROM AUTHOR]

Constructing lunar pavements is of great significance for improving the transportation efficiency of materials and personnel transfer at lunar bases. Utilizing lunar regolith for the in-situ preparation of geopolymer is an effective means of supplying raw materials for lunar pavement construction. This present study prepared geopolymers for pavement material with lunar regolith simulant. The influence of NaOH on the compressive strength of geopolymers was understood by using different percentages of NaOH as alkaline activator. The effect of urine on the compressive strength of geopolymers by using artificial urine of different pH values as liquid phases. The results indicated that the addition of artificial urine slightly reduces the compressive strength of geopolymers, and the effects of pH and NaOH percentage are different. Microstructural analysis performed by Mercury Intrusion Porosimetry and Scanning Electron Microscope, indicated that choosing fine-particle lunar regolith simulant as precursor is more conducive to the preparation of highstrength geopolymers using human urine. [ABSTRACT FROM AUTHOR]

The Martian surface and shallow subsurface lacks stable liquid water, yet hygroscopic salts in the regolith may enable the transient formation of liquid brines. This study investigated the combined impact of water scarcity, UV exposure, and regolith depth on microbial survival under Mars-like environmental conditions. Both vegetative cells of Debaryomyces hansenii and Planococcus halocryophilus, alongside with spores of Aspergillus niger, were exposed to an experimental chamber simulating Martian environmental conditions (constant temperatures of about − 11 °C, low pressure of approximately 6 mbar, a CO2 atmosphere, and 2 h of daily UV irradiation). We evaluated colony-forming units (CFU) and water content at three different regolith depths before and after exposure periods of 3 and 7 days, respectively. Each organism was tested under three conditions: one without the addition of salts to the regolith, one containing sodium chlorate, and one with sodium perchlorate. Our results reveal that the residual water content after the exposure experiments increased with regolith depth, along with the organism survival rates in chlorate-containing and salt-free samples. The survival rates of the three organisms in perchlorate-containing regolith were consistently lower for all organisms and depths compared to chlorate, with the most significant difference being observed at a depth of 10–12 cm, which corresponds to the depth with the highest residual water content. The postulated reason for this is an increase in the salt concentration at this depth due to the freezing of water, showing that for these organisms, perchlorate brines are more toxic than chlorate brines under the experimental conditions. This underscores the significance of chlorate salts when considering the habitability of Martian environments. [ABSTRACT FROM AUTHOR]

The 2012 satellite ASTER geoscience maps of Australia were designed to provide public, web-accessible, and spatially comprehensive surface mineralogy for improved mapping and solutions to geoscience challenges. However, a number of the 2012 products were clearly compromised by variable green and/or dry vegetation cover. Here, we show a strategy to first estimate and then unmix the contributions of both these vegetation components to leave, as residual, the target surface mineralogy. The success of this unmixing process is validated by (i) visual suppression/removal of the regional climate and/or local fire-scar vegetation patterns; and (ii) pixel values more closely matching field sample data. In this process, we also found that the 2012 spectral indices used to gauge the AlOH content, AlOH composition, and water content can be improved. The updated (new indices and vegetation unmixed) maps reveal new geoscience information, including: (i) regional "wet" and "dry" zones that appear to express "deep" geological characters often expressed through thick regolith cover, with one zone over the Yilgarn Craton spatially anti-correlated with Archaean gold deposits; (ii) a ~1000 km wide circular feature over the Lake Eyre region defined by a rim of abundant "muscovite" that appears to coincide with opal deposits; (iii) a N–S zonation across the western half of the continent defined by abundant muscovite in the south and kaolinite in the north, which appears to reflect opposing E ↔ W aeolian sediment transport directions across the high-pressure belt; (iv) various paleo-drainage networks, including those over aeolian sand covered the "lowlands" of the Canning Basin, which are characterized by low AlOH content, as well as those over eroding "uplands", such as the Yilgarn Craton, which have complicated compositional patterns; and (v) a chronological history of Miocene barrier shorelines, back-beach lagoons, and alluvial fans across the Eucla Basin, which, to date, had proved elusive to map using other techniques, with potential implications for heavy mineral sand exploration. Here, we explore the latter three issues. [ABSTRACT FROM AUTHOR]

Knowledge regarding the abundance and distribution of solar wind (SW)‐sourced water (OH/H2O) on the Moon in the shallow subsurface remains limited. Here, we report the NanoSIMS measurements of H abundances and D/H ratios on soil grains from three deepest sections of the Chang'E‐5 drill core sampled at depths of 0.45–0.8 m. High water contents of 0.13–1.3 wt.% are present on approximately half of the grain surfaces (topmost ∼100 nm), comparable to the values of Chang'E‐5 scooped soils. The extremely low δD values (as low as −995‰) and negative correlations between δD and water contents indicate that SW implantation is an important source of water beneath the lunar surface. The results are indicative of homogeneous distribution of SW‐derived water in the vertical direction, providing compelling evidence for the well‐mixed nature of the lunar regolith. Moreover, the findings demonstrate that the shallow subsurface regolith of the Moon contains a considerable amount of water. Plain Language Summary: Recently, China's Chang'E‐5 mission targeted a higher latitude on the Moon than previous Apollo and Luna missions, and brought back scooped and drilled samples to the Earth. These new soil samples provide an opportunity to investigate the distribution, abundance, and origin(s) of water in Moon's middle latitude. Here, we focus on using the NanoSIMS technique to analyze water content on soil near‐surface regions to understand whether the solar wind (SW)‐derived water could be preserved after burial at depth. Our results show that more than half of the core soils have high water contents on the rims of grains, similar to those of the Chang'E‐5 scooped soils. This finding suggests that the SW remains an important source of water in the Moon's subsurface. Our work provides direct evidence that the lunar regolith below the surface contains considerable water from SW implantation. This type of water could be a promising water resource in future exploration. Key Points: More than half of the soils from the single drill core have high water contents and low D/H ratios below the surfaceThe solar wind (SW)‐derived water could be preserved for hundreds of millions of years if buried at depthLunar regolith from the drill core contains considerable water from SW implantation, which is much more accessible [ABSTRACT FROM AUTHOR]

The H 2 O concentration and H 2 O/Ce ratio in olivine-hosted melt inclusions are high in lunar pyroclastic sample 74220 (H 2 O up to 1410 ppmw; H 2 O/Ce up to 77) but lower (H 2 O 10 to 430 ppmw; H 2 O/Ce 0.3 to 9.4) in all other lunar samples studied before this work. The difference in H 2 O concentration and in H 2 O/Ce ratio is absent for other volatile elements (F, S, and Cl) in melt inclusions in 74220 and other lunar samples. Because H 2 O (or H) is a critical volatile component with significant ramifications on the origin and evolution of the Moon, it is important to understand what causes such a large gap in H 2 O/Ce ratio between 74220 and other lunar samples. Two explanations have been advanced. One is that volcanic product in sample 74220 has the highest cooling rate and thus best preserved H 2 O in melt inclusions compared to melt inclusions in other samples. The other explanation is that sample 74220 comes from a localized heterogeneity enriched in some volatiles. To distinguish these two possibilities, here we present new data from two rapidly cooled lunar samples with glassy melt inclusions: olivine-hosted melt inclusions (OHMIs) in 79135 regolith breccia (unknown cooling rate but with glassy MIs similar in texture with those in 74220), and pyroxene-hosted melt inclusions (PHMIs) in 15597 pigeonite basalts (known high cooling rate, second only to 74220 and 15421). In addition, we also investigated new OHMIs in sample 74220. If the gap is due to the difference in cooling rates, samples with cooling rates between those of 74220 and other studied lunar samples should have preserved intermediate H 2 O concentrations and H 2 O/Ce ratios. Our results show that melt inclusions in 79135 and 15597 contain high H 2 O concentrations (up to 969 ppmw in 79135 and up to 793 ppmw in 15597) and high H 2 O/Ce ratios (up to 21 in 79135 and up to 13 in 15997), bridging the big gap in H 2 O/Ce ratio among 74220 and other lunar samples. Combined with literature data, we confirm that H 2 O/Ce ratios of different lunar samples are positively correlated to the cooling rates and independent of the type of mare basalts. We hence reinforce the interpretation that the lunar sample with the highest cooling rate best represents pre-eruptive volatiles in lunar basalts due to the least degassing. Based on Ce concentration in the primitive lunar mantle, we estimate that H 2 O concentration in the primitive lunar mantle (meaning bulk silicate Moon) is 121 ± 15 ppmw. Our new data also further constrain F/P, S/Dy and Cl/Ba ratios in lunar basalts and the lunar mantle. Estimated F, P, and S concentrations in the lunar primitive mantle are 4.4 ± 1.1 ppmw, 22 ± 8 ppmw, and 67 - 33 + 67 ppmw, respectively. [ABSTRACT FROM AUTHOR]

The pioneering objective of a permanent outpost on the lunar surface requires the development of technologies for in situ resource utilisation. Consolidation of lunar soil into products is imperative to avoid unaffordable transportation burdens. The paper addresses the feasibility of the Local Microwave Heating effect as a promising technology for sintering lunar regolith based on microwave radiation, with a simple solid-state generator requiring a relatively modest amount of energy. Experiments were conducted using terrestrial simulants with physical and chemical properties similar to those of lunar regolith. Laboratory equipment with a purpose-built microwave actuator was designed and manufactured with "Design for Embarking" in mind. Experiments have demonstrated the feasibility of the proposed technology with a reasonable degree of confidence. Solid artefacts were obtained with proper setting of microwave parameters and appropriate scanning strategy, proving the feasibility of regolith sintering with a localised microwave source A roadmap for future development of the technology has been established. • Preliminary study on Localized Microwave Sintering of Lunar Regolith: Highlights. • Localized Microwave Heating is effective to consolidate lunar regolith simulants. • A solid-state generator with an open-end antenna is a promising lightweight low-energy system for ISRU. • Microwave heating of regolith is feasible regardless of the simulant's ilmenite content. • The technique can be used to produce 3D parts using an additive approach. [ABSTRACT FROM AUTHOR]

Dust removal from Martian spacesuits whilst on exploration activities is critically important for long-term Martian exploration missions. Martian dust is known to contain harmful particles which must be removed from Martian spacesuits to prevent entry into habitation zones on Mars, and prevent spacesuit wear. In this work, an Electrostatic Removal System was developed which utilised the phenomenon of dielectrophoresis to remove Martian dust from the outer layer of spacesuits. Dielectrophoretic forces were exerted on dust particles by an alternating electrostatic field which acted to remove the particles from a surface. The field was generated by applying high voltage square waves, produced by a MOSFET H-Bridge, across an array of parallel copper electrodes contained within an Electrostatic Removal Device. A theoretical model was derived to predict the effect of variables on the system performance, which was validated through experimental testing. This system demonstrated a high dust clearing performance of over 95% when the dust is in direct contact with the Electrostatic Removal Device's surface. However, the system was not able to achieve dust removal from samples of Nomex, Teflon, and Kevlar, the three constituent materials of the outer layer of spacesuits. Further development is required for the system to become a viable option for the removal of Martian dust from spacesuits. Nonetheless, this system may prove effective in other applications such as dust removal from solar panels or optical devices, where the electrodes may be able to be integrated directly beneath the dust layer. • Dielectrophoretic forces are capable of displacing Martian dust particles of < 63 μ m. • This electrostatic removal system repeatably achieves 95% dust clearing performance. • Poor clearing performance was achieved when removing dust from spacesuit fabric. • A MOSFET H-Bridge was used to generate 0–1000 V two-phase square waves. • Electrostatic removal system parameters investigated theoretically and experimentally. [ABSTRACT FROM AUTHOR]

As a lunar lander attempts to make a soft landing on the moon, the supersonic exhaust plumes from the descent engine can liberate a large quantity of regolith grains off the ground surface. In this work, we investigate the particle–particle collision phenomenon inside this regolith spray with the soft sphere method — an alternate to the generally used hard sphere approach. Individual collisions are resolved by generating spring and damping forces at the contact point of particles that are already moving under fluid drag and buoyancy. To reduce the computational burden, a 1:100 scale model of the real flow domain is used. We insert 60,000 numerically representative regolith particles through random locations on the ground to yield an initial solid grain density of ∼ 1 0 8 particles/m3. Three different particle diameters, ranging from small to moderately large, are considered to account for the wide size variation of lunar regolith, and observe the relationship between inter-particle collisions and particle size. The coefficient of restitution is varied to model completely inelastic collisions to highly elastic collisions. Results indicate that collisions between larger regolith grains with high elasticity cause a significant portion of particles to reach high elevations inside the domain and leave at large angles. However, the majority of the ejecta spray is bound within a shallow region (< 3°) above ground where they move slowly due to weak plume-generated forces. On the other hand, inelastic collisions tend to significantly decrease the maximum particle height within the domain, but the main particle stream is more uniformly distributed in the flow domain and average particle speed increases. Maximum particle speed shows an inverse relation with energy depletion in collisions, but this relation becomes less remarkable for larger (100 and 150 μ m) grains. Overall, particle trajectory results in this work align with the 1–3° angles measured for the visible regolith sheet in Apollo landing videos. However, the possibility of many grains ejecting at much higher angles due to collisions is also revealed. These high-angle particles can be problematic for relying on berms on the lunar surface to block the regolith spray. • Collisions inside plume-driven lunar regolith are studied with the soft sphere method. • Highly elastic collisions between large grains decrease their average speed. • The same collisions increase maximum particle height and speed in the flow domain. • Trajectories of small particles are not significantly affected by collisions. [ABSTRACT FROM AUTHOR]