The contributions of external and internal hydration (OH and H2O) on the shape and strength of hydration related features at 3 and 6 mu m for lunar relevant nominally anhydrous minerals were investigated under vacuum conditions. Understanding the effect of hydration on the reflectance spectra of lunar analog materials in the laboratory can provide insights into remote sensing observations of the lunar surface and the potential for 3 and/or 6 mu m observations to determine the speciation of hydration on the Moon. We demonstrate changes in the shape and strength of the broad 3 mu m absorption feature in olivine and anorthite that is associated with the removal of hydration under changing environmental conditions. The overlapping nature of OH and H2O related absorption features in the similar to 3 mu m region makes it difficult to uniquely determine the speciation of hydration. Despite evidence of H2O loss in the 3 mu m region, we do not observe the fundamental bending mode of H2O at 6 mu m, posing potential challenges for the detection H2O on the lunar surface and throughout our solar system.

Lunar soil, as an in-situ resource, holds significant potential for constructing bases and habitats on the Moon. However, such constructions face challenges including limited mechanical strength and extreme temperature fluctuations ranging from -170 degrees C to +133 degrees C between lunar day and night. In this study, we developed a 3D-printed geopolymer derived from lunar regolith simulant with an optimized zig-zag structure, exhibiting exceptional mechanical performance and thermal stability. The designed structure achieved remarkable damage tolerance, with a compressive strength exceeding 12.6 MPa at similar to 80 vol% porosity and a fracture strain of 3.8 %. Finite element method (FEM) simulations revealed that the triangular frame and wavy interlayers enhanced both stiffness and toughness. Additionally, by incorporating strategically placed holes and extending the thermal diffusion path, we significantly improved the thermal insulation of the structure, achieving an ultralow thermal conductivity of 0.24 W/(m K). Furthermore, an iron-free geopolymer coating reduced overheating under sunlight by 51.5 degrees C, underscoring the material's potential for space applications.

In situ resource utilization of lunar regolith provides a cost-effective way to construct the lunar base. The melting and solidifying of lunar soil, especially under the vacuum environment on the Moon, are the fundamentals to achieve this. In this paper, lunar regolith simulant was melted and solidified at different temperatures under a vacuum, and the solidified samples' morphology, structure, and mechanical properties were studied. The results indicated that the density, compressive strength, and Vickers hardness of the solidified samples increased with increasing melting temperature. Notably, the sample solidified at 1400 degrees C showed excellent nanohardness and thermal conductivity originating from the denser atomic structure. It was also observed that the melt migrated upward along the container wall under the vacuum and formed a coating layer on the substrate caused by the Marangoni effect. The above results proved the feasibility of employing the solidified lunar regolith as a primary building material for lunar base construction.

H2O extraction from remote icy lunar regolith using concentrated irradiation was investigated under high-vacuum and low-temperature conditions. The thermal sublimation of H2O(s) from packed beds of lunar regolith simulants was quantified with and without an indirect solar receiver for average concentrated irradiations of 37.06 f 2.66 and 74.62 f 3.57 kW/m2. The indirect solar receiver increased sublimation by an average of 18.7 % f 10.4 %, despite slower heating rates due to its increased thermal mass. Different average concentrated irradiations affected the heating rates and thermal gradients within the packed bed, but the impact on overall sublimation was not statistically significant. An inverse relationship between heating rates and normalized sublimation was also observed, where rapid sublimation near the heating elements led to the formation of a desiccated layer of regolith, which behaved as a thermal insulator and further limited heat transfer, reducing the sublimation efficiency. These findings provide key insights for optimizing in-situ resource utilization technologies, contributing to the development of efficient methods for extracting H2O from lunar regolith, which is essential for sustainable space exploration.

Surficial water ice has been detected in the permanently shaded regions (PSRs) near the lunar poles. Water ice can be detected by its diagnostic absorption features of ice at 1.0, 1.25, 1.5, and 2.0 mu m, as well as high reflectance in the VIS region. However, the effects of particle size and shape, ice abundance, and phase angle on the VNIR spectra of ice mixtures remain poorly understood, posing a challenge for detections of water ice on the lunar surface. In this study, we measured the VNIR spectra of pure water ice and mixtures of water ice and a lunar highland regolith simulant (HRS). We investigated the effects of particle size of ice (0-250 mu m), particle shape of ice (angular vs. spherical), phase angle (0-105 degrees), and ice abundance (0-50 wt%) on the VNIR spectra of water ice and HRS mixtures from 350 to 2500 nm. Our results show that coarser ice particles exhibit stronger NIR absorptions and lower VIS reflectance, attributable to increased photon absorptions due to longer optical pathlengths. Similarly, the longer optical pathlengths of spherical particles relative to angular ones result in lower VIS reflectance. The forward scattering nature of water ice leads to increased VIS reflectance at high phase angles (>90 degrees), suggesting that high phase angles are optimal for lunar water ice detection. Phase angles have a negligible effect on the strength of the NIR absorptions of ice, especially when ice is present at low ice abundances (<20 wt%) in intimate mixtures with the HRS. Lastly, our findings suggest that the NIR absorptions near 1.25, 1.5, and 2.0 mu m rapidly deepen at very low ice concentrations (0-5 wt%). We also find a linear relationship between VIS reflectance and ice content in intimate mixtures with a HRS containing 0-50 wt% ice. The findings of this study offer a detailed framework for detecting and analyzing water ice on the lunar surface via VNIR spectroscopy.

The lunar base establishing is crucial for the long-term deep space exploration. Given the high costs associated with Earth-Moon transportation, in-situ resource utilization (ISRU) has become the most viable approach for lunar construction. This study investigates the sintering behavior of BH-1 lunar regolith simulant (LRS) in a vacuum environment across various temperatures. The sintered samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), along with nanoindentation, uniaxial compression, and thermal property tests to evaluate the microstructural, mechanical, and thermal properties. The results show that the sintering temperature significantly affects both the microstructure and mechanical strength of the samples. At a sintering temperature of 1100 degrees C, the compressive strength reached a maximum of 90 MPa. The mineral composition of the sintered samples remains largely unchanged at different sintering temperatures, with the primary differences observed in the XRD peak intensities of the phases. The plagioclase melting first and filling the intergranular pores as a molten liquid phase. The BH-1 LRS exhibited a low coefficient of thermal expansion (CTE) within the temperature range of - 150 degrees C to 150 degrees C, indicating its potential for resisting fatigue damage caused by temperature fluctuations. These findings provide technical support for the in-situ consolidation of lunar regolith and the construction of lunar bases using local resources.

The solidification and molding of lunar regolith are essential for constructing lunar habitats. This study introduces an innovative lunar regolith molding technique that synergistically combines solar concentration, flexible optical fiber bundle energy transfer, and powder bed fusion. A functional prototype is developed to validate the proposed scheme. Systematic experiments including fixed beam spot melting, line melting, surface melting, and body melting are conducted using simulated basalt lunar regolith. Through in-situ observation of the melt pool's formation, evolution, and expansion dynamics, we identify a sequential transformation mechanism on the powder bed's surface: initial curling evolves into detachment from the bed, subsequent incorporation into a molten droplet, and ultimate solidification. A comprehensive evaluation of density and mechanical properties across multiple parameter combinations reveals that energy flux density of 3.33 MW/m2 with a scan speed of 30 mm/min, inter-track spacing of 3 mm, and layer thickness of 2 mm enables the production of structurally integral samples with continuous morphology. The resulting specimens demonstrate a maximum compressive strength of 4.25 MPa and a density of 2.31 g/cm3. This solar-powered additive manufacturing approach establishes a viable reference framework for large-scale on-site construction of lunar research stations.

National Aeronautics and Space Administration plans to deploy astronauts to the Moon and construct sustainable habitat modules in collaboration with private companies and national space agencies worldwide. In situ resource utilization (ISRU) is indispensable for large-scale, long-term human lunar exploration. Water ice, which is one of the most precious resources, is believed to exist in the Moon's polar regions. Future plans include using it to maintain life support for astronauts and provide raw materials (H2 and O2) for rocket engines and fuel cells. Because the capture and delivery of ice are required to utilize water on the Moon, the following potentially reliable and efficient capture and delivery technologies for water ice, which are based on electrodynamic, electromagnetic, and mechanical vibration forces, are being developed. (1) The first is a capture and delivery system based on electrodynamic standing waves. When a high alternating voltage is applied to parallel screen electrodes, the alternating electrodynamic force is exerted on ice and regolith particles in contact with the lower electrode, and some agitated particles are captured after they pass through the openings of the upper screen electrode. The captured particles are transported between an array of zigzag electrodes activated by the application of high alternating voltage. (2) The second is a delivery system that utilizes an electrodynamic traveling wave. Three- or four-phase high voltage is applied to parallel line or ring electrodes to form an electrodynamic traveling wave. Meanwhile, regolith and ice particles are conveyed by traveling waves. Horizontal, curved, inclined, and vertical deliveries are realizable using this system. (3) The third is an electromagnetic delivery system based on the coil-gun principle, which considers the fact that lunar regolith particles are magnetic. A multistage coil-gun mechanism powered by a charged inductor-capacitor-resistor (LCR) circuit is used to deliver the regolith particles over long distances. (4) The fourth is a vibration delivery system. The vibration-conveyance mechanism, which is widely applied in terrestrial industries, is used to deliver regolith and ice particles. When the particles are on a plate or in a tube vibrated diagonally by actuators, the vibrating plate or tube is repeatedly propelled and conveys the particles diagonally in the forward direction. When the lower end of an inclined or vertically supported vibrating tube is immersed in a layer of regolith or ice particles, particles are introduced into the tube, and the friction force between the particles and the inner wall of the tube is used to convey the particles upward. This paper provides an overview of the recent progress of these unique technologies for efficient and reliable ISRU on the Moon.

Space weathering has long been known to alter the chemical and physical properties of the surfaces of airless bodies such as the Moon. The isotopic compositions of moderately volatile elements in lunar regolith samples could serve as sensitive tracers for assessing the intensity and duration of space weathering. In this study, we develop a new quantitative tool to study space weathering and constrain surface exposure ages based on potassium isotopic compositions of lunar soils. We first report the K isotopic compositions of 13 bulk lunar soils and 20 interval soil samples from the Apollo 15 deep drill core (15004-15006). We observe significant K isotope fractionation in these lunar soil samples, ranging from 0.00 %o to + 11.77 %o, compared to the bulk silicate Moon (-0.07 +/- 0.09 %o). Additionally, a strong correlation between soil maturity (Is/FeO) and K isotope fractionation is identified for the first time, consistent with other isotope systems of moderately volatile elements such as S, Cu, Zn, Se, Rb, and Cd. Subsequently, we conduct numerical modeling to better constrain the processes of volatile element depletion and isotope fractionation on the Moon and calculate a new K Isotope Model Exposure Age (KIMEA) through this model. We demonstrate that this KIMEA is most sensitive to samples with an exposure age lower than 1,000 Ma and becomes less effective for older samples. This novel K isotope tool can be utilized to evaluate the surface exposure ages of regolith samples on the Moon and potentially on other airless bodies if calibrated using other methods (e.g., cosmogenic noble gases) or experimental data.

Utilizing water ice from the lunar permanently shadowed regions (PSRs) is essential for sustainable space exploration. This study explored the optimization of thermal mining methods for in-situ water ice extraction, focusing on how to adjust the configuration of heating rods to meet the flexible operational needs on the Moon, alongside the effects of water ice particle size and heating temperature. Our findings suggest that optimizing the heating temperature according to the water ice particle size and arrangement of heating rods significantly improves extraction performance. Specifically, by maintaining the water ice particle size greater than 20 mu m, we increase the thermal conductivity of the regolith-ice mixture by approximately 135 % compared to dry regolith, greatly shortening the extraction time. Notably, precise control of extremely low heating temperatures allows for significant expansion of the extraction range of a single heating rod. In scenarios where time constraints are minimal, the extraction range can be significantly expanded. Our innovative approach, grounded in fundamental heat transfer principles, demonstrates broad applicability and potential extension to water ice extraction on other celestial bodies. These findings provide a crucial foundation for efficient lunar resource utilization, satisfying the critical needs of future lunar missions and advancing human presence on the Moon.