Effect of the solar wind on the formation of a photoinduced dusty plasma layer near the surface of the Moon

A dusty plasma layer formed near the illuminated part of the surface of the Moon under the action of ultraviolet radiation, as well as fast and slow solar wind, has been numerically simulated. The numerical calculations including the photoemission properties of lunar regolith samples delivered to the Earth have been compared to estimates within known theoretical models. It has been shown that the flux of solar wind particles plays an important role in the formation of the surface photoelectron layer. The conditions of the charging and stable levitation of dust particles in the surface plasma layer of the Moon have been analyzed.     

Water in the Moon’s polar areas: Results of LEND neutron telescope mapping

The results of LEND neutron telescope mapping of the lunar surface are presented. The estimations obtained show that the water content in the regolith in the polar areas of the Moon reaches 0.4 % by weight and not directly determined by the illuminated surface.     

Study of primary cosmic rays on the Moon’s surface and in orbit around the Moon

A mathematical model for experiments aimed at studying the primary cosmic rays on the Moon’s surface and in orbit around the Moon is considered. The feasibility of simultaneously registering in three components (secondary neutrons, gamma rays, and radio emission) particles of primary cosmic rays via reverse current in showers developing in the lunar regolith is demonstrated.     

Investigation of primary cosmic rays at the Moon’s surface

The possibility of experimentally studying primary cosmic rays at the Moon’s surface is considered. A mathematical simulations of showers initiated in the lunar regolith by high-energy particles of primary cosmic rays is performed. It is shown that such particles can in principle be recorded by simultaneously detecting three components of backscattered radiation (secondary neutrons, gamma rays, and radio emission).     

Impacts of fast meteoroids and the separation of dust particles from the surface of the Moon

The possibility of the separation of dust particles owing to impacts of micrometeoroids on the surface of the Moon has been discussed. It has been shown that this effect is significant and should be taken into account when determining the number of particles rising over the surface of the Moon at the formation of a plasma–dust system. The average number of regolith particles leaving the surface of the Moon owing to the impacts of fast meteoroids has been determined for various altitudes over the Moon. The size distribution function of particles leaving the surface of the Moon because of impacts of meteoroids has been determined. It has been shown that impacts of meteoroids constitute an important source of dust microparticles in the plasma–dust system over the surface of the Moon.     

Particle-size sorting system of lunar regolith using electrostatic traveling wave

A particle-size sorting system of lunar regolith using an electrostatic traveling wave is developed for In-Situ Resource Utilization on the Moon to extract indispensable resources from the regolith and realize long-term exploration. The regolith is sorted by utilizing a balance between the electrostatic and gravitational forces, which are determined depending on particle size, in vacuum conditions where the particles are not subjected to air drag. In this study, the effect of particle charge on the particle motion is confirmed by conducting model experiments and numerical calculations based on the distinct element method. In addition, it was experimentally demonstrated that particles less than approximately 20 μm in diameter were efficiently separated from the bulk of a lunar regolith simulant FJS-1 in a vacuum condition (∼1.5 × 10⁻² Pa), and the performance of the size sorting system on the Moon was predicted by the numerical calculations. The system utilizes only the electrostatic force, and it does not require any gas, liquid, or mechanical moving parts.     

Vibration transport system for lunar and Martian regolith using dielectric elastomer actuator

An electrostatic transport system for lunar and Martian regolith particles was developed to realize In-Situ Resource Utilization for the successful long-term exploration of the Moon and Mars. The new system utilizes the dielectric elastomer actuator (DEA), which consists of a dielectric elastomer film sandwiched between elastic plate electrodes. When a high AC voltage is applied to the electrodes, the dielectric elastomer is driven by Maxwell stress and the resultant vibration is utilized to transport the regolith. The system has no mechanical drives and does not need complicated controls or high power consumption; thus, it is highly reliable for space application. In this study, the motions of regolith particles on a vibrating plate in the Earth and Moon environments were firstly investigated using a simple model calculation. Then, two types of vibration transport systems using DEA were developed based on the calculation results, and the basic characteristics of vibration transport for regolith were experimentally determined. The calculation result shows that the acceleration of the vibrating plate is the key factor for the success of vibration transport, and the lunar regolith simulant FJS-1 could be experimentally transported at a feed rate of approximately 1.95 g/s on the Earth using one of the developed system types when the plate acceleration exceeded 14.7 m/s². It is expected that the transport performance of the system will be improved in the Moon environment owing to the absence of air drag and the small gravitational force.     

Dusty plasma system in the surface layer of the illuminated part of the moon

The dusty plasma system in the surface layer of the illuminated part of the Moon has been considered. The maximum height of the dust rise has been determined. It has been shown that a dead zone, where dust particles cannot rise over the surface of the Moon, is absent near a lunar latitude of 80°. The size and height distributions of dust have been determined.     

Impacts of fast meteoroids and a plasma–dust cloud over the lunar surface

The possibility of the formation of a plasma–dust cloud in the exosphere of the Moon owing to impacts of meteoroids on the lunar surface is discussed. Attention is focused on dust particles at large altitudes of ~10–100 km at which measurements were performed within the NASA LADEE mission. It has been shown that a melted material ejected from the lunar surface owing to the impacts of meteoroids plays an important role in the formation of the plasma–dust cloud. Drops of the melted material acquire velocities in the range between the first and second cosmic velocities for the Moon and can undergo finite motion around it. Rising over the lunar surface, liquid drops are solidified and acquire electric charges, in particular, owing to their interaction with electrons and ions of the solar wind, as well as with solar radiation. It has been shown that the number density of dust particles in the plasma–dust cloud present in the exosphere of the Moon is ?10^?8 cm^?3, which is in agreement with the LADEE measurements.     

Formation of Dusty Plasma Clouds at Meteoroid Impact on the Surface of the Moon

The nature of two dusty plasma clouds appearing because of the impact of a meteoroid on the surface of the Moon has been discussed. It has been shown that one of the clouds is formed by particles (or fragments) of regolith ejected into free space by a shock wave induced by the meteoroid impact on the surface of the Moon and the second cloud is formed by solidified melt droplets. The main characteristics of these clouds, including the cloud expansion rates, the characteristic sizes of particles in both clouds, and the concentrations and charges of particles, have been calculated. The calculated cloud expansion rates are in qualitative agreement with the observational data.     

Mössbauer mineralogy on the Moon: The lunar regolith

A first-order requirement for spacecraft missions that land on solid planetary objects is instrumentation for mineralogical analyses. For purposes of providing diagnostic information about naturally-occurring materials, the element iron is particularly important because it is abundant and multivalent. Knowledge of the oxidation state of iron and its distribution among iron-bearing mineralogies tightly constrains the types of materials present and provides information about formation and modification (weathering) processes. Because Mössbauer spectroscopy is sensitive to both the valence of iron and its local chemical environment, the technique is unique in providing information about both the relative abundance of iron-bearing phases and oxidation state of the iron. The Mössbauer mineralogy of lunar regolith samples (primarily soils from the Apollo 16 and 17 missions to the Moon) were measured in the laboratory to demonstrate the strength of the technique for in-situ mineralogical exploration of the Moon. The regolith samples were modeled as mixtures of five iron-bearing phases: olivine, pyroxene, glass, ilmenite, and metal. Based on differences in relative proportions of iron associated with these phases, volcanic-ash regolith can be distinguished from impact-derived regolith, impact-derived soils of different geologic affinity (e.g., highlands and maria) can be distinguished on the basis of their constituent minerals, and soil maturity can be estimated. The total resonant absorption area of the Mössbauer spectrum can be used to estimate total FeO concentrations.     

月球表面热辐射计算模型研究

为深入了解月球表面的热环境,根据月表红外发射率随温度变化以及太阳光反射率随入射方向变化的特点,建立了月表的多温段变反射率辐射计算模型.将该模型与月壤非稳态导热微分方程结合,并考虑日、月相对运动关系,形成了月表温度计算方法.在计算程序验证的基础上,分析了月表温度的变化规律与控制因素,比较了月海与月陆两种月表单元的温度差异...     

Inverse problem in the LORD experiment and the possibility of diagnosing the radiation length of lunar regolith

The inverse problem of reconstructing events in the LORD experiment is considered taking into account fuzzy information on the radiation length of lunar regolith over the lunar surface. It is shown that the solution of the inverse problem allows rather accurate diagnostics of the radiation length at various lunar surface points for a significant number of detected individual events.     

Mitigation of lunar dust adhered to mechanical parts of equipment used for lunar exploration

A unique cleaning system has been developed utilizing electrostatic force to remove lunar dust adhered to the mechanical parts of equipment used for lunar exploration. A single-phase voltage is applied to parallel electrodes printed on a flexible substrate to remove the dust. More than 90% of adhered dust was repelled from the surface of the slightly inclined device in a vacuum, and the cleaning performance of the system would be further improved in the low-gravity environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.     

Lower-hybrid turbulence in the near-surface lunar dusty plasmas

The results are presented of the first investigation of linear and nonlinear processes associated with waves which are related to the presence of magnetic fields in dusty plasmas at the Moon. Excitation of lower-hybrid turbulence in dusty plasmas near the lunar surface is studied. It is shown that the lower-hybrid turbulence can be generated wherever the Earth's magnetotail interacts with the near-surface dusty plasmas at the Moon. The electric fields appearing as a consequence of the presence of lower-hybrid turbulence are estimated. They can make a significant contribution to the total electric field above the lunar surface which should be taken into account in the future experimental investigation of electric fields at the Moon.     

Influence of the vacuum-lunar regolith interface on the generation of radio emission by a cascade shower from an ultrahigh-energy particle

We present the results of our calculation of the radio emission field produced by an electron-photon shower from an ultrahigh-energy particle under the surface of the Moon. We consider two cases of cascade propagation: the first in the lunar regolith-vacuum direction at small angles to the interface; and the second in the opposite direction when the particle generates a cascade almost immediately after it has crossed the vacuum-regolith interface. To calculate the relative energy density of the emission emerged at the surface, we have used the method of decomposing spherical waves into plane ones. The intensity of the refracted waves for high frequencies has been found to depend strongly on the shower inclination angle.     

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ~10^10.4 m^-3 and ~10^11.5 m^-3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.     

Violation of the coherence of radio waves induced by a cascade shower in the lunar regolith

It has been shown that small fluctuations of the refractive index of the lunar regolith owing to, e.g., a nonuniform density distribution, give rise to the loss of the coherence of a Cherenkov radio pulse induced by a cascade shower from an ultrahigh-energy particle and to a strong decrease in the spectral density of the radio signal. This can be one of the causes of why no events from ultrahigh-energy cosmic particles on the surface of the moon have been detected.     

Simulation of an experiment on detecting ultra-high-energy particles with regard to the structure of the lunar soil surface layer

The feasibility of using the lunar orbital radio detector to detect radio signals from cascades initiated by ultra-high-energy cosmic rays interacting with the lunar regolith is studied. Simulation by the Monte Carlo method demonstrates that, with the regolith thickness randomly distributed in the range 2–12 m, the detection of radio signals reflected from the lower boundary of the regolith (for particle energies W ≥ 10²⁰ eV) increases the number of valid events severalfold. The additional contribution due to the reflected radio-frequency radiation greatly enhances the scientific potential of experiments with the lunar orbital radio detector.