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.

Previous lunar missions, such as Surveyor, Apollo, and the Lunar Atmosphere and Dust Environment Explorer (LADEE), have played a pivotal role in advancing our understanding of the lunar exosphere's dynamics and its relationship with solar wind flux. The insights gained from these missions have laid a strong foundation for our current knowledge. However, due to insufficient near-surface observations, the scientific community has faced challenges in interpreting the phenomena of lunar dust lofting and levitation. This paper introduces the concept of signals of opportunity (SoOP), which utilizes radio occultation (RO) to retrieve the near-surface dust density profile on the Moon. Gravity Recovery and Interior Laboratory (GRAIL) radio science beacon (RSB) signals are used to demonstrate this method. By mapping the concentration of lunar near-surface dust using RO, we aim to enhance our understanding of how charged lunar dust interacts with surrounding plasma, thereby contributing to future research in this field and supporting human exploration of the Moon. Additionally, the introduced SoOP will be able to provide observational constraints to physical model development related to lunar surface particle sputtering and the reactions of near-surface dust in the presence of solar wind and electrostatically charged dust grains.

Mechanical adhesion among lunar regolith particles significantly influences the shear characteristics of lunar regolith. However, experimental limitations on Earth and challenges in capturing particle-scale information obscure the microscopic mechanisms of adhesion and its interaction with other particle properties, such as shape. This study employs the Discrete Element Method to bridge this gap by incorporating mechanical adhesion and simplifying the particle shape effect. Numerical triaxial shear tests were performed on representative volume elements under densities representative of lunar surface. The study introduced a simplified shape parameter, the rolling friction coefficient mu r, r , representing particle 3D sphericity, which ranged from 0.025 to 1.6. Additionally, the particle surface energy density gamma was adjusted from 0 to 1.28 x 10-- 2 J/m2 2 to model the effects of mechanical adhesion. Stress-strain relationships, friction angles, and microscale mechanics parameters were thoroughly analyzed. Simulation results reveal that under low stress, the e c-ln p relationship remains linear, consistent with critical state sand theory. Significant variability in macro properties is influenced by micro-Newton adhesive forces and rolling friction coefficients (0.1-0.8), particularly in particles with notable irregularities, where adhesion profoundly affects mechanical properties, requiring precise calibration. This research advances the understanding of the shear behavior of lunar regolith, providing critical insights for future simulations and experimental designs.

Lunar exploration is of significant importance in the development and utilization of in situ lunar resources, water ice exploration, and astronomical science. In recent years, ground-based radar (GBR) has gained increasing attention in the field of lunar exploration due to its flexibility, low cost, and penetrating capabilities. This paper reviews the scientific research on lunar exploration using GBR, outlining the basic principles of GBR and the progress made in lunar exploration studies. Our paper introduces the fundamental principles of lunar imaging using GBR and systematically reviews studies on lunar surface/subsurface detection, the dielectric properties inversion of the lunar regolith, and polar water ice detection using GBR. In particular, the paper summarizes the current development status of the Chinese GBR and forecasts future development trends in China. This review will enhance the understanding of lunar exploration results using GBR radar, systematically demonstrate the main applications and scientific achievements of GBR in lunar exploration, and provide a reference for GBR radar in future lunar exploration missions.

Astrophysical processes can involve sublimation rates too low to be measured in the laboratory. Here, measured vapor pressures of solid H 2 O, Ar, CO 2 , H 2 S, NH 3 , SO 2 , CH 4 , HCN, CH 3 OH, and C 2 H 4 are reviewed, fitted, and robustly extrapolated to lower temperatures. Knowledge gaps regarding vapor pressures are identified for several chemical species. Maps of lunar cold traps for supervolatiles are presented based on sublimation rates time -averaged over diurnal and seasonal cycles of measured surface temperatures for the north and south polar region. The cold trap areas for these supervolatiles are all much smaller than for H 2 O.

Volatile organic molecules and a complex organic refractory material were detected on the Moon and on lunar samples. The Moon's surface is exposed to a continuous flux of solar UV photons and fast ions, e.g. galactic cosmic rays (GCRs), solar wind (SW), and solar energetic particles (SEPs), that modify the physical and chemical properties of surface materials, thus challenging the survival of organic compounds. With this in mind, the aim of this work is to estimate the lifetime of organic compounds on the Moon's surface under processing by energetic particles. We performed laboratory experiments to measure the destruction cross of selected organic compounds, namely methane (CH4), 4 ), formamide (NH2CHO), 2 CHO), and an organic refractory residue, under simulated Moon conditions. Volatile species were deposited at low temperature (17- 18 K) and irradiated with energetic ions (200 keV) in an ultra-high vacuum chamber. The organic refractory residue was produced after warming up of a CO:CH4 4 ice mixture irradiated with 200 keV H+ + at 18 K. All the samples were analyzed in situ by infrared transmission spectroscopy. We found that destruction cross sections are strongly affected (up to one order of magnitude) by the dilution of a given organic in an inert matrix. Among the selected samples, organic refractory residues are the most resistant to radiation. We estimated the lifetime of organic compounds on the surface of the Moon by calculating the dose rate due to GCRs and SEPs at the Moon's orbit and by using the experimental cross values. Taking into account impact gardening, we also estimated the fraction of surviving organic material as a function of depth. Our results are compatible with the detection of CH4 4 in the LCROSS eject plume originating from layers deeper than about 0.7 m at the Moon's South Pole and with the identification of complex organic material in lunar samples collected by Apollo 17 mission.

With unique geographical characteristics and potential water ice resources,the lunar polar regions become the preferred areas for future lunar scientific exploration and base construction.However,at the lunar polar regions, differences in solar illumination conditions,limits for the direct earth communication,large variation range of lunar surface temperature and steep terrains,pose great challenges to the site selection research.It is of great significance to quantitatively study the temperature and topography distribution of the lunar polar regions.A method for evaluating the relative habitable zone on the moon was developed by using the observations of the laser altimeter(LOLA)and radiometer(Diviner)on the Lunar Reconnaissance Orbiter(LRO).Typical relative habitable zones were selected,taking the lunar south pole as the target.And the characteristics of the diurnal and seasonal variations of the surface temperature of these zones were analyzed.Moreover,the distributions of terrain slope,surface roughness and terrain height in these regions were compared.Region A(around Scott M)is located on the relative highlands of the lunar south pole(about 3 to 7km)with moderate slope(median value of 8 degrees)and surface roughness(less than 2m).Region B(near de Gerlache)is the closest to the center of the south pole,with sun visibility up to 0.8,relative steep slope(median value of 12.4 degrees)and moderate surface roughness(less than 2 m).Region C(around Amundsen)has the lowest terrain(about - 1.8 to - 0.5km),the minimum sun visibility(less than 0.6)and earth visibility(less than 0.5),and the gentlest topographic slope(median value of 5.4 degrees),whereas approximate 26% areas possessed a surface roughness greater than 3 m.In summer night,the temperatures of partial areas in region B and region A can be higher than 0degree celsius and - 20degree celsius, respectively,indicating relatively ideal environment for outpost sites in future lunar missions.

This is an exercise to explore the concentration of lithium, lithium-7 isotope and the possible presence of black dirty ice on the lunar surface using spectral data obtained from the Clementine mission. The main interest in tracing the lithium and presence of dark ice on the lunar surface is closely related to future human settlement missions on the moon. We investigate the distribution of lithium and 7 Li isotope on the lunar surface by employing spectral data from the Clementine images. We utilized visible (VIS-NIR) imagery at wavelengths of 450, 750, 900, 950 and 1000 nm, along with near-infrared (NIR-SWIR) at 1100, 1250, 1500, 2000, 2600 and 2780 nm, encompassing 11 bands in total. This dataset offers a comprehensive coverage of about 80% of the lunar surface, with resolutions ranging from 100 to 500 m, spanning latitudes from 80 degrees S to 80 degrees N. In order to extract quantitative abundance of lithium, ground-truth sites were used to calibrate the Clementine images. Samples (specifically, 12045, 15058, 15475, 15555, 62255, 70035, 74220 and 75075) returned from Apollo missions 12, 15, 16 and 17 have been correlated to the Clementine VIS-NIR bands and five spectral ratios. The five spectral ratios calculated synthesize the main spectral features of sample spectra that were grouped by their lithium and 7 Li content using Principal Component Analysis. The ratios spectrally characterize substrates of anorthosite, silica-rich basalts, olivine-rich basalts, high-Ti mare basalts and Orange and Glasses soils. Our findings reveal a strong linear correlation between the spectral parameters and the lithium content in the eight Apollo samples. With the values of the 11 Clementine bands and the 5 spectral ratios, we performed linear regression models to estimate the concentration of lithium and 7 Li. Also, we calculated Digital Terrain Models (Altitude, Slope, Aspect, DirectInsolation and WindExposition) from LOLA-DTM to discover relations between relief and spatial distribution of the extended models of lithium and 7 Li. The analysis was conducted in a mask polygon around the Apollo 15 landing site. This analysis seeks to uncover potential 7 Li enrichment through spallation processes, influenced by varying exposure to solar wind. To explore the possibility of finding ice mixed with regolith (often referred to as `black ice'), we extended results to the entire Clementine coverage spectral indices, calculated with a library (350-2500 nm) of ice samples contaminated with various concentrations of volcanic particles.

The paper presents an acousto-optic lunar infrared spectrometer (LIS) intended for mineralogical analysis and assessment of the hydration of the lunar surface regolith near the lander. Its optical layout, characteristics, results of calibrations and laboratory measurements are given. The LIS is designed to measure the spectrum of solar radiation reflected by the lunar surface; it will function as part of the load complex of the Luna-25 lander. The instrument is mounted on the manipulator of the lander in such a way that its field of view is within the field of view of the television support stereo cameras of the robotic arm working zone (TV RPM). The instrument operates in the spectral range of 1.15-3.4 mu m, including the OH/H2O absorption bands, with a spectral resolution of approximately 25 cm(-1). The principle of operation of the device is based on acousto-optic spectral filtering of optical radiation.

Understanding the sources of lunar water is crucial for studying the history of lunar evolution, as well as the interaction of solar wind with the Moon and other airless bodies. Recent orbital spectral observations revealed that the solar wind is a significant exogenous driver of lunar surficial hydration. However, the solar wind is shielded over a period of 3-5 days per month as the Moon passes through the Earth's magnetosphere, during which a significant loss of hydration is expected. Here we report the temporal and spatial distribution of polar surficial OH/H2O abundance, using Chandrayaan-1 Moon Mineralogy Mapper (M-3) data, which covers the regions inside/outside the Earth's magnetosphere. The data shows that polar surficial OH/H2O abundance increases with latitude, and that the probability of polar surficial OH/H2O abundance remains at the same level when in the solar wind and in the magnetosphere by controlling latitude, composition, and lunar local time. This indicates that the OH/H2O abundance in the polar regions may be saturated, or supplemented from other possible sources, such as Earth wind (particles from the magnetosphere, distinct from the solar wind), which may compensate for thermal diffusion losses while the Moon lies within the Earth's magnetosphere. This work provides some clues for studies of planet-moon systems, whereby the planetary wind serves as a bridge connecting the planet with its moons.