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.

It is believed that dust formations above the lunar surface, manifested via sunlight scattering and detected in-situ, are of too low density to pose threats to lunar missions. However, occasionally prolonged fading/kindling of the immersing/emerging stars near the lunar limb indicates much denser low-altitude dust clouds. We performed statistical analysis of such abnormal stellar occultation events (ASOEs), found in the Lunar Occultation Archive. Specific dependence of their duration on selenographic position reveals an impact-plume like shape of dust clouds and excludes visual illusions, terrestrial cloudiness, and double stars as causes of the observed starlight extinction. The probability of the long-lasting ASOEs peaks during the Perseid meteor shower in August, confirming the impact-related nature of most of the related dust clouds. At the same time, additional semi-monthly periodicity of ASOEs points to a complementary mechanism of dust lifting due to, for example, lunar outgassing triggered by solar tides.

The thermoplastic contact and charge properties of lunar dust particles notably affect their mechanical properties, such as contact, collision, adhesion, transport, and wear properties. Contact forces and deformation of these particles are influenced by temperature differences between lunar dust particles and the surfaces of contact materials, caused by extreme temperature fluctuations on the lunar surface. Moreover, the geometric characteristics of particles affect their charge distribution and quantity. However, research on typical sharp lunar dust particles is limited. Herein, the thermoelastoplastic contact and charge characteristics of nonrotationally symmetric sharp lunar dust particles are investigated. Contact areas, thermal loads, indentation depths, and residual displacements during normal contact between lunar dust particles and an elastic-plastic half-space are determined at various temperature differences. In addition, expressions for the self-capacitance and charge quantity of lunar dust particles are proposed. Validity and accuracy of the developed model are verified via experimental data and numerical results. Furthermore, the effect of temperature differences on the contact forces, deformation, and dynamic characteristics of lunar dust particles is analyzed, and thermal load results are compared with the results obtained using other contact models. In addition, the variations in charge and charge-driven forces (e.g., Coulomb forces) with particle size are investigated. Overall, this study provides an important theoretical reference for utilizing in situ resources on the lunar surface.

In recent years, prominent spacefaring nations have redirected their attention towards the Moon as potential avenue for economic prospects and as a pivotal waypoint for extended space exploration endeavors. Nonetheless, a notable concern has emerged regarding the dispersion of lunar dust during lunar landings, a phenomenon that has been associated with documented instances of equipment damage during prior missions. To mitigate these challenges, leading research institutions are actively engaged in endeavors aimed at minimizing the adverse effects of dust dispersal during lunar and extraterrestrial landings. This review paper provides a comprehensive overview of ongoing research and development endeavors focusing on the interaction dynamics between rocket plumes and lunar surfaces, along with the resultant dispersion of lunar dust triggered by rocket plume impingement. Additionally, it presents research efforts aimed at developing lunar dust mitigation technologies.

The sharp morphological features of lunar dust particles generate significant elastic-plastic contact forces and deformations upon contact with material surfaces, which considerably affect the mechanical properties of lunar dust particles, including their contact, collision, adhesion, transport, and wear characteristics. Despite these severe effects, valid models considering the contact characteristics of typical sharp-featured lunar dust particles are currently lacking. This study proposes an elastic-plastic contact model for nonrotationally symmetric lunar dust particles showing typical sharp features. Detailed derivations of the expressions for various physical responses observed when lunar dust particles establish normal contacts with elastic and elastic-plastic half-spaces under adhesive conditions are also provided. These include derivations for elastic forces, elastic-plastic forces, contact areas, pull-off forces, residual displacements, and plastic deformation areas. Furthermore, the tangential pull-off force during the tangential loading of lunar dust particles is derived, and the tangential contact characteristics are explored. Comparisons of the results of the proposed model with those of previous experiments reveal that the proposed model shows errors of only 6.06 % and 1.03 % in the maximum indentation depth and residual displacement, respectively. These errors are substantially lower than those of conventional spherical models (60.30 % and 60.13 %, respectively), confirming the superior accuracy of the proposed model. Furthermore, the discrete element method is employed to analyze the effects of normal and tangential contacts, dynamic characteristics, and plastic deformations on the considered lunar dust particles. The results are then compared with those of existing contact models. They reveal that maximum elastic-plastic forces under normal contact conditions are positively correlated with the initial velocity but negatively correlated with the lateral angle. Furthermore, the tangential pull-off force is positively correlated with the normal force and surface energy. In addition, the contact duration of lunar dust particles is positively correlated with their initial velocities, while the residual displacement is negatively correlation. For instance, as the initial velocity increases from 10 to 50 m/s, the maximum elastic-plastic force increases from 37.64 to 321.72 mN. Comparisons of the proposed model with other contact models reveal that the maximum elastic-plastic force of the elastic-plastic triangular pyramid model is only 14.93 % that of the cylindrical model, 34.23 % that of the spherical model, and 76.27 % that of the conical model, indicating significant reductions in the maximum elastic-plastic force owing to the plastic deformations of particles with typical sharp features. Overall, the results of this study offer crucial insights into the mechanical characteristics of nonspherical lunar dust particles under various contact conditions, such as elastic-plastic and adhesive contacts, and can guide in situ resource utilization on the lunar surface and for craft landings.

This study reviews major sensing technologies for the Lunar environment and its resources, as they have been developed since the times of Apollo missions. Selected technologies of sensors and instruments for the chemical, isotopic, and structural analysis of Lunar rocks and regoliths, as well as of the Lunar exosphere environment, are presented in a critical review towards an optimised and information-rich framework. Special focus is given on the activated Lunar regolith, and especially the Lunar dust, describing the development of Lunar simulants as the only accessible materials for experimentation and testing of the above technologies. New technologies are also highlighted, such as the development of the OxR microfluidic and spectroscopy integrated device, which, in its small scale aims to detect reactive oxygen species in the Lunar regolith, while in its larger format it is used to release oxygen gas from the Lunar dust and regolith, enabling astronaut respiration and fuel production on the Moon. It is finally suggested that miniaturisation of instruments and sensors, together with the standardisation of output information and characterisation protocols through holistic informational frameworks, will enhance the dynamic expansion and further integration and interoperation of sensors and devices, aiming to an efficient, safer, and resilient utilisation on the Moon and the establishment of sustainable settlements in the near future. (c) 2024 Published by Elsevier B.V. on behalf of COSPAR.

We review studies of physical processes associated with the impact of external factors in outer space flows of micrometeoroids and solar radiation on the lunar regolith. Under the influence of these factors, regolith microparticles can detach from the surface and levitate. Near-surface plasma and levitating dust particles form a plasma-dust exosphere of the Moon. Under anthropogenic effects on the lunar environment, charged levitating microparticles can have an extremely negative impact on the engineering systems of lunar landers and on the activity and health of astronauts on the Moon. Based on information gained by automated and manned lunar missions and in laboratory experiments, we discuss modern ideas about physical processes occurring near the Moon's surface. Unsolved problems associated with the plasma-dust exosphere of the Moon are considered, and the principal strategies for their solution are outlined.

To reduce transportation costs for building a lunar base station, it is important to utilise in-situ resources like lunar regolith. Lunar regolith can be used to create a concrete-like material by means of geopolymerization. For application of geopolymerizing mixtures, the rheology of the slurry must be known in advance. This article investigates the rheology of mixtures of lunar dust simulants with water, NaOH (as alkaline agent) and urea (as superplasticizer). The rheology of all the mixtures can be approximated with the Bingham Model. Aging has a dramatic effect on the rheology of the water + simulant mixture and, after 2 days, the yield stress decreases by six times. The presence of NaOH, on the contrary, increases both the apparent viscosity and the yield stress as it promotes geopolymerization. The addition of urea reduces the viscosity by 25%, but it has a limited effect on the yield stress. These findings can enable the design of construction 3D printers on the moon. (C) 2021 COSPAR. Published by Elsevier B.V. All rights reserved.

The surface of the Moon, like that of any airless body in the Solar System, constantly experiences micrometeorite bombardment as well as the influence of solar radiation, solar wind, and other factors of outer space. As a result of the impacts of high-velocity micrometeorites over billions of years, the lunar surface silicate basis crumbles, turning into particles with a wide size distribution. Considering the explosive nature of their origin, these particles are characterized by an extremely irregular shape with sharp edges or conglomerates sintered at high temperatures or almost spherical droplets. On the illuminated side of the Moon, solar radiation, especially the ultraviolet part of its spectrum, and solar wind streams interact with the upper regolith layer, charging the regolith surface. The photoelectrons generated above the surface create, together with the charged regolith surface, a near-surface double layer. The electric field generated in this layer, as well as the particle charge fluctuations on the surface, create conditions under which electric forces may exceed the gravitational force and the van der Waals force of adhesion. As a result, micron- and submicron-sized regolith particles become capable of detaching from the surface and levitating above it. These dynamic processes cause the transport of dust particles above the lunar surface and the scattering of sunlight on these particles. Glows of this kind were observed over the lunar surface by television systems of American and Soviet landing vehicles in the early stages of lunar exploration. American astronauts who landed on the lunar surface during the Apollo program also discovered manifestations of lunar dust. It turns out that dust particles levitating over the regolith surface due to natural processes and those took off the surface due to anthropogenic factors cause many technological problems that compromise the performance of landing vehicles and their systems, hamper astronaut activity on the lunar surface, and are detrimental to their health. Based on the results of these missions, it is concluded that micron- and submicron-sized dust particles, levitating above the surface, pose a major, barely surmountable obstacle in further research and exploration of the Moon. Since then, studies of physical processes associated with the behavior of lunar dust, manifestations of its aggressive properties (toxicity), and ways to reduce the harmful effects of dust on engineering systems and on humans have become topical in theoretical and experimental research. In this review, the results of the past half century of studies on the behavior of dust particles serve as a basis to discuss the formation of the lunar regolith and the Moon's near-surface plasma-dust exosphere under the influence of outer space factors. The causes and conditions underling the behavior of dust particles are examined as well as implications of these processes, the influence of anthropogenic factors, and possible hazards to spacecraft and engineering systems during the implementation of the currently planned programs of lunar research and exploration. The main unsolved problems are listed in studying the behavior of the dust component of the lunar regolith; ways to address the problematic issues are discussed.

Lunar dust presents a serious challenge to all operations on the Moon, whether human or robotic. It can be especially problematic in applications where it is necessary to make high integrity, gas-tight seals, such as within payloads designed for in situ analysis of lunar ices and volatiles. The challenge has been addressed within the context of the ProSPA instrument being developed for the Luna-27 mission. Soft sealing materials are preferred in order to minimise the required sealing force to enable use of lightweight actuators. JSC-1A simulant was used to test and compare the sealing performance of the elastomer Kalrez (R) 7075 and of Indium. It was found that both materials were able to seal at dust levels of up to 0.90 mg/cm(2) with an applied force of up to 400 N. Indium offers the best sealing performance (better than 10(-7) mbar.l.s(-1)) but Kalrez (R) is capable of operation at higher temperature, which may be beneficial in applications in which samples are heated to release gases for analysis.