Current Lunar dust mitigation techniques and future directions

Performance of chemically modified reduced graphene oxide (CMrGO) in lunar electrodynamic dust shield (EDS) applications

Under the dynamic influence of near-surface plasma, intricate dynamics of lunar dust have been observed during the Surveyors and Apollo missions in the form of Lunar horizontal glow. These dynamics are primarily driven by electrostatic forces generated by the continual bombardment of solar wind and highly energetic UV photons on the lunar surface and dust particles. This paper revisits the phenomenon of dust charging within the lunar photoelectron sheath and subsequent dynamics. The investigation has been carried out using a comprehensive model of the lunar photoelectron sheath characterized by observed solar spectra, latitude-dependent Fermionic photoelectrons, non-Maxwellian solar wind electrons, and cold ions. A test dust particle is introduced into the sheath, and equilibrium charge and static levitation conditions are derived. The result of dynamical evolution suggests the existence of a narrow parametric regime corresponding to the periodic hopping trajectory of the dust particle over the lunar surface. In other cases, the dust particles are found to re-impact the surface after a single ballistic hop. We further identify that the discrete charging of the dust could be crucial in determining the dust dynamics, particularly in the tenuous plasmas. The analysis of the discrete dust charging model reveals significant discrepancies with the continuous dust charging model and suggests a lower likelihood of static dust levitation in the lunar environment. The present study is important for unraveling the fundamental processes governing surface evolution on the Moon and other airless bodies throughout the Solar System.

Solar PV soiling mitigation by electrodynamic dust shield in field conditions

Unlike the Earth, the Moon lacks is not protected from the atmosphere and global magnetic field, and will be directly exposed to complex radiation environments such as high-energy cosmic rays, solar wind, and the Earth’s magnetotail plasma. The surface of the Moon is covered with a thick layer of lunar soil, and the particles in the soil with a diameter between 30 nm–20 μm are called lunar dust. In the complex environments such as solar wind or magnetotail plasma, lunar dust carries an electric charge and becomes charged lunar dust. Charged lunar dust is prone to migration under the action of the electric field on the lunar surface. Charged migrated lunar dust is easy to adhere to the surface of instruments and equipment, resulting in visual impairment, astronauts’ movement disorders, equipment mechanical blockage, sealing failure, and material wear, which affects the lunar exploration mission. As an important lunar exploration landing site, the lunar south pole receives special solar radiation and produces a special dust plasma environment due to its special location. In order to provide an environmental reference for lunar south pole exploration, it is necessary to explore the characteristics of the dust plasma environment in the lunar south pole and its impact. In view of the lunar south pole environment, The Spacecraft Plasma Interactions Software (SPIS) software developed by the European Space Agency is used to carry out modelling and simulation in this work. Through the simulation, the logarithmic distribution of the lunar dust space density in a range of 0–200 m at the lunar south pole, the potential distribution near the lunar surface, and the spatial distribution characteristics of plasma electrons and ions are obtained. The obtained lunar dust space density and lunar surface potential are similar to the previous theoretical derivation and field detection data, so the simulation results have high reliability. The spatial potential distribution and the spatial density distribution of electrons and ions in the lunar environment with and without lunar dust are compared. Finally, the conclusions can be drawn as follows. The space potential increases with altitude increasing. The potential at 0–10 m near the lunar south pole is about –40 V, and the space potential at 100 m is about –20 V. The density of lunar dust in an altitude range below 10 m is 10<sup>7.22</sup> m<sup>–3</sup>–10<sup>4.66</sup> m<sup>–3</sup>. The electron density in the dust plasma near the lunar surface is 10<sup>5.47</sup> m<sup>–3</sup>, and the ion density is 10<sup>6.07</sup> m<sup>–3</sup>, and both increase with altitude increasing. Charged lunar dust affects the spatial distribution of lunar dust, mainly through affecting the distribution of the space electric field, which leads to difference in electron distribution, but has little effect on ions.

Lunar soil simulants play a crucial role in scientific research, payload tests and in-situ resource utilization (ISRU) experiments. However, the currently available lunar soil simulants are either low in TiO2 content (≤3 wt%) or high in TiO2 content (≥6.7 wt%), despite orbital observations indicating lunar soils with moderate TiO2 content being widely distributed on the lunar surface. In December 2020, China's Chang'e−5 (CE-5) mission successfully returned a new mare soil sample characterized by high FeO content (22.5 wt%) and moderate TiO2 content (5.5 wt%), providing an opportunity to develop moderate-TiO2 lunar soil simulants. This study presents a newly developed simulant of the CE-5 lunar soil named IGG-01, which closely replicates the major physical and chemical properties of the CE-5 lunar soil. The median particle size of IGG-01 is 68.69 ± 4.44 μm, and its estimated specific surface area is 0.34 m2/g. It contains 17.6 wt% FeO and 4.8 wt% TiO2. It consists of pyroxene (49.3 wt%), plagioclase (40.9 wt%), ilmenite (6.1 wt%), and olivine (3.7 wt%), with specific gravity and bulk density are 3.33 g/cm³ and 1.86 g/cm³, respectively. The friction angle is 41.8°, and the cohesion is 19.2 kPa. It exhibits strong and weak reflectance absorption features in the 1 and 2 μm band centers. The physical properties of IGG-01 are also comparable to those of Apollo samples and typical lunar mare soil simulants. The unique chemical composition of IGG-01 makes it suitable for various scientific and engineering experiments, including but not limited to the study of dusty plasma migration, water formation via solar wind injection, oxygen preparation via hydrogen reduction, and tests involving the movement of rovers and excavation equipment.

Geology dominated the science of the six successful Apollo lunar sampling expeditions. About 380 kg of rocks and soils were collected in 2400 samples, along with many thousands of documenting photos. Lunar dust shrouding Moonscapes, obscuring and coating rock samples, was a nuisance for geologist-advisers and plagued each astronaut with its inescapable presence, sticking to every surface. Lunar dust was judged by Apollo 17 geologist-astronaut Harrison Schmitt as ‘No. 1 environmental problem on the Moon.’ As fine as talcum powder but more abrasive than sandpaper, dust jeopardised vacuum sealing of sample containers to preserve rocks free from terrestrial contamination, just as later at Houston it jeopardised long-term archives of lunar samples. Yet the only one type of Apollo experiment to measure dust and its movements in situ was a matchbox-sized Dust Detector Experiment (DDE) weighing 270 g deployed on Apollo 11, 12, 14 and 15 Apollo Lunar Surface Experiment Packages (ALSEPs), which transmitted DDE data to Earth every 54 s between 21 July 1969 and 30 September 1977. This report by the Australian inventor and Principal Investigator of the minimalist DDE, designed to hitch-hike, outlines its discoveries of basic characteristics of movements and stickiness of lunar dust. Unexpected realities include effects of (1) an out-gassing aura metres in extent surrounding an astronaut and (2) contamination and heating effects of ‘collateral dust,’ lunar surface dust kicked up and splashed by astronauts on experiments and rock samples. Some interpretations of DDE data presented in Apollo-era literature are challenged and alternative interpretations are presented, with two Apollo-era dust discoveries not referenced for 40 years. Little-known potential contamination of Apollo experiments, Moon rock samples and photographic validity is discussed, together with ongoing discoveries of the basics of dust such as dynamic behaviour and long-term accretion.

Following the renewed interest in the volatile inventory of the Moon witnessed in the last decade, from both sample studies and data from orbital missions, it is timely to reassess the distribution and likely source(s) of light element volatiles (C, N, He, Ne, and Ar) in a diverse suite of lunar mare basalts and soils, providing new insights about volatiles indigenous to the lunar interior, volatiles produced <i>in situ</i> at the lunar surface, and volatiles delivered to and implanted into the lunar surface. Simultaneous static-mode mass spectrometric measurements of these key volatiles, extracted from the same aliquot of sample by high-resolution stepped combustion, enable a more detailed identification of the different volatile components present by comparing their varying release patterns across a range of temperature steps. Taken in context with other studies of different volatile elements, this new data contributes towards a greater understanding of the Earth-Moon system, with additional implications for future <i>in situ</i> resource utilisation at the lunar surface. <br><br> With an average δ¹⁵N value of +0.93 ± 9.39 ‰, the indigenous N component measured in mare basalts is most compatible with a CO carbonaceous chondrite source for nitrogen in the lunar interior, although some caveats exist. Variations in abundance and isotopic composition of indigenous nitrogen imply a heterogeneous lunar mantle. Assuming up to ~50 % loss of solar wind ³⁶Ar from lunar soils, nitrogen trapped in soils can be reconciled with up to 87 % being contributed from a non-solar source with an isotopic composition of between +87 ‰ and +160 ‰. <br><br> Noble gases in soils are dominated by solar wind components, with only minor amounts of cosmogenic neon being released at the highest temperature steps. In mare basalts, noble gases are a mixture of trapped, radiogenic, and cosmogenic components (from which cosmogenic production rates can be calculated and exposure ages for previously undated samples suggested

Remote Determination of Exposure Degree and Iron Concentration of Lunar Soils Using VIS-NIR Spectroscopic Methods

Simulating lunar highlands regolith profiles on Earth to inform infrastructure development and ISRU activities on the Moon

Heat rejection from power systems will be necessary for human and robotic activity on the lunar surface. Functional operation of such heat rejection systems is at risk of degradation as a consequence of dust accumulation. The Apollo astronauts encountered marked degradation of performance in heat rejection systems for the lunar roving vehicle, science packages, and other components. Although ground testing of dust mitigation concepts in support of the Apollo mission identified mitigation tools, the brush concept adopted by the Apollo astronauts proved essentially ineffective. A better understanding of the issues associated with the impact of lunar dust on the functional performance of heat rejection systems and its removal is needed as planning gets underway for human and robotic missions to the Moon. Renewed emphasis must also be placed on ground testing of pristine and dust-covered heat rejection system surfaces to quantify degradation and address mitigation concepts. This paper presents a review of the degradation in performance of heat rejection systems encountered on the lunar surface to-date, and will discuss current activities underway to evaluate the durability of candidate heat rejection system surfaces and current dust mitigation concepts.

Upper limits for a lunar dust exosphere from far-ultraviolet spectroscopy by LRO/LAMP

Since the moon has an extremely rarefied atmosphere, the full spectrum of the electromagnetic radiation of the sun reaches the surface, charging the surface dust and affecting its current charge state. Lunar surface dust thus remains electrostatically charged at all times. Charged lunar dust will adversely affect the operations of most mechanical systems required by manned and unmanned exploration missions. Charged dust will also stubbornly adhere to solar panels and thermal radiators, thus reducing their efficiencies. Researches on the charged lunar dust can help to investigate lunar dusty environment as well as to solve those particle-induced problems by both simulation and experiment in laboratory. In this work, two different charging processes of charged lunar dust in the environment of electron beam and the radiation of ultraviolet source are considered. The computer numerical simulation method is used to analyze these two different charging processes of lunar dust, to explore the charging mechanisms of lunar dusts, and to choose an appropriate way of charging for the lunar environment simulation device in laboratory. On the basis of the classic dust charging equation, the charging equation of a dust in pure electron environment is given for the first time in this work. Meanwhile, the charging process under ultraviolet radiation is discussed and combined with the specific application of charging dusts. A solver of fourth-order Runge-Kutta algorithm is made to solve differential equations under two different irradiation sources. The main simulation results show that:1) in electron environment, the surface dust charge number increases as the particle size and the current intensity of electron guns increase, while the charge number increases as the beam spot radius of electron guns decreases; 2) under ultraviolet radiation, the dust charge number increases with the particle size and irradiance increasing, but charging efficiency is slow. A great dust charge number needs a long time radiation from sun (equivalent to 74 deuterium lamps), which means that more ultraviolet radiation sources are essential to speeding up the experiment in laboratory. Although the calculated efficiency of ultraviolet radiation is lower than electron irradiation, the secondary-electron emission, the scattering and the transmission process of electron irradiation are ignored, which can greatly reduce the efficiency of charging by energetic electron guns in the actual experiment. Therefore, comparing these two charging mechanisms and considering the actual design requirements for the space environment simulation device, charging by lots of ultraviolet radiation is an appropriate scheme for electrification of lunar dusts.

Lunar regolith dust is an unavoidable hazard that will accumulate in suits, cabins, and equipment over trips to the lunar surface. This is important in systems like Gateway, as too much lunar dust brought in from missions could pose a hazard to the crew onboard. However, we currently know very little about exactly how much dust could end up on Gateway, from where, and the properties of the dust itself. To aid in this understanding of what lunar dust could look like on Gateway, a computational fluid dynamics (CFD) model of the Gateway HALO module was developed in ANSYS Fluent. Discrete phase modeling was used to track the movement and fates of lunar dust particles in the cabin, accounting for ventilation flow and monitoring which outlet vents and ports experienced the highest dust loads. Because there are so many unknowns related to lunar dust, this model investigated the effects of several variables, including dust drop location, particle size, particle density, and total mass injected. This analysis can be used to inform dust loading on dust-sensitive visiting vehicles and filter design.

Without atmosphere, the lunar surface is gradually evolved into lunar soil by the space weathering. The space weathering generates lunar soil and matures it. This progress changes the morphological structure and the spectral characteristics. Thus the spectral characteristics of lunar soil contains information about the space weathering of the moon's surface. Lunar soil maturity is an important indicator to describe the degree of the space weathering. Using hyperspectral data to produce the submicroscopic metallic iron (SMFe) and to obtain lunar maturity is an important method for studying the space weathering. Since the in situ detection data is not disturbed, the results obtained are relatively more accurate and reliable. Therefore, the Chang'e-4 (CE-4) Yutu-2 rover was equipped with a detection instrument that directly obtained the in situ hyperspectral data (450-2395 nm) of the lunar surface, which provided a good opportunity for studying the lunar weathering. Two spectral data near the landing site of the CE-4 lander were selected, using the Hapke model and the spectral angle matching method, SMFe content was produced. The maturity of the lunar soil near the landing site of the CE-4 was further inferred based on the Morris model and FeO content. The results show that the lunar soil's maturity is 11.5, indicating that it may be immature lunar soil.

Mitigation of lunar dust regolith remains one of the most pressing issues in space suit development when it comes to surface exploration. Fabrics treated with shear thickening fluid (STF) and super hydrophobic coating have been shown in previous studies to significantly reduce dust adhesion to the Orthofabric surface. The Orthofabric weave construction is such that there is significant void space that can allow dust penetration, even after treatments. Here, we will present the ongoing development of a hybrid textile material that leverages the dust mitigation properties of the STF and superhydrophobic treated fabrics with dust penetration resistant properties of nonwoven. Nonwoven fabrics made of materials capable of surviving the harsh temperatures of the lunar surface are commonly used in filtration settings and could be beneficial to dust mitigation on the Lunar and Martian surface. A hybrid structure where a high strength, temperature stable fiber was needle punched onto the back side of a woven fabric was investigated. The materials were evaluated on their mechanical properties, including puncture and abrasion resistance, and their dust mitigation properties. The final structure had a P84® polyimide fiber needle punched onto the back face of a modified version of Orthofabric, which produced a material that was able to stop dust penetration. Treating this material with STF and adding a superhydrophobic coating reduced the dust adhesion by over half. The material remained flexible enough to easily drape and can be easily sewn for manufacturing a final part. This hybrid nonwoven fabric showed both the ability to both stop penetrating dust while decreasing the dust adhered to the surface and being easily cleanable.