To reveal the effect of secondary electron emission on the charging properties of a surface covered by micron-sized insulating dust particles and the migration characteristics of these particles, for the first time we used a laser Doppler method to measure the diameters and velocities of micron-sized anorthite particles under electron beam irradiation with an incident energy of 350 eV. Here, anorthite particles are being treated as a proxy for lunar regolith. We experimentally confirm that the vertical transport of anorthite particles is always dominant, although horizontal transport occurs. In our experiments, some anorthite particles were observed to have large vertical velocities up to 9.74 m s⁻¹ at the measurement point. The upper boundary of the vertical velocities V _z of these high-speed anorthite particles are well constrained by its diameter D, that is, V z 2 linearly depends on D ⁻². These velocity–diameter data provide strong constraints on the dust charging and transportation mechanisms. The shared charge model could not explain the observed velocity–diameter data. Both the isolated charge model and patched charge model appear to require a large dust charging potential of −350 to −78 V to reproduce the observed data. The microstructures of the dusty surface may play an important role in producing this charging potential and in understanding the pulse migration phenomenon observed in our experiment. The presented results and analysis in this paper are helpful for understanding the dust charging and electrostatic transport mechanisms in airless celestial bodies such as the Moon and asteroids in various plasma conditions.

The lunar polar regions are key areas for future exploration due to the long-term continuous illumination and persistently shadowed regions that can cold trap abundant water and other volatiles. However, the complex terrain, dynamic lighting, and solar wind-induced electric-field environment present multiple challenges for polar investigation and sampling missions. China’s Chang’E-7 (CE-7) will explore the Moon’s south polar region in 2026. One of the scientific goals is to drill samples in a wide area with a rover for in situ analysis. This study analyzes the engineering constraints of the polar illumination condition, slopes, and electric field for landing and sampling-site selection. Then, we create a 3D model of CE-7’s lunar rover in three operating environments by employing the Spacecraft Plasma Interaction Software, with the rover sampling (i) on a flat surface, (ii) in a shadow, and (iii) near a meter-scale crater under different solar altitude angles. The results show that the rover can be charged to different potentials under the combined effects of solar wind incident angles and surrounding terrains. We find that a favorable traversing and/or sampling site of the rover for future polar exploration is in the upwind direction of a bulge (positively elevated terrains, such as the lander or boulders) or crater, which will cause a minimum charging effect on the rover. Our results have important implications for minimizing the risk of charging effects and guiding the lunar polar region exploration.

The internal heat flow related to the Moon’s composition, interior structure, and evolution history is not well-constrained and understood on a global scale. Up to now, only two in situ heat flow experiments, Apollo 15 and 17 were deployed nearly 50 years ago. The measured high values of heat flow might be influenced by lateral heat at highland/mare boundaries and enhanced by heat production from radioactive elements enriched unit, and may also be disturbed by astronauts’ activities. In this study, we proposed a new method to retrieve heat flows at two permanently shadowed craters, Haworth and Shoemaker of the Moon’s south pole, from Chang’E-2 microwave radiometer data and Diviner observations. Our results show that the average heat flow is 4.9 ± 0.2 mW/m². This provides a constraint for the bulk concentration of Thorium within the lunar south polar crust 656 ± 54 ppb, which helps us understand the Moon’s thermal evolution and differentiation.

Dust electrostatic migration is one of the primary causes of dust events on the surface of airless celestial bodies, which can result in multiple dust phenomena, including lunar horizon glow and dust pools, and also offer crucial insights into the evolution of the surface materials of airless celestial bodies. To date, the characteristics and laws of dust electrostatic migration are still not well understood. Here, we report the electrostatic migration characteristics of pyroxene, olivine, and ilmenite particles measured by the laser Doppler method and compare them with the findings of anorthite particles in previous experiments to recognize the differential migration characteristics of different mineral components in the lunar dust. The results demonstrate that the particle sizes of most moving pyroxene and olivine particles are in the range of 0–10 μm, and their vertical velocities are typically less than 2 m s⁻¹, which are consistent with the previous studies. The cohesive force between the dust particles is probably what causes the difference in the migration rates of various insulating minerals. Note that no moving ilmenite particles were detected probably due to the material’s good conductivity. It can be speculated that the concentration of fugitive dust in the lunar mare is affected by the ilmenite content, but further research is needed to determine how low ilmenite content can cause dust migration.

Solar radiation plays an important part in lunar surface thermal environment. The topographic effect was usually ignored in previous work, which might cause great uncertainties in surface temperature simulation. To better understand the surface temperatures of the craters at any time and on any location of the Moon, we simulated the effective solar irradiance and temperatures of the Banting crater as an example. In this work, we firstly constructed a three-dimensional Banting crater (16.4$^\circ$E, 26.6$^\circ$N) model based on the elevation data obtained from the Lunar Orbiter Laser Altimeter onboard Lunar Reconnaissance Orbiter (LRO), and then calculated the distribution of the effective solar irradiance at different local times. In addition, we calculated the distribution of percentage of illuminated area of the Banting-like craters at any day time and on all locations of the Moon. These results show that the craters located within 48.2$^\circ$N/S and at the time of 08:48–15:12 are illuminated without any self-shading, while that located at high latitudes or near to dawn/dusk endure different degrees of the self-shading effect. Finally, we simulated the temperatures of the Banting crater at different local times based on the surface radiation balance. Compared to the temperatures measured by Diviner aboard LRO, the results show that the simulated temperatures are well consistent with the Diviner observations, which verified our models and simulation results.

以月球Aristarchus地区为例, 基于覆盖全月的高精度数字高程模型(SLDEM2015)得到的月表坡度和方位角数据, 计算2025至2045年之间研究区处于近日点夏至/冬至、远日点夏至/冬至四个时间点时, 正午时刻的有效太阳辐照度. 其次, 基于充电电流平衡理论, 计算四个时间点对应的平衡表面电势和垂向电场强度. 研究发现地形、纬度、日月距离、季节对有效太阳辐照度和表面电场的分布特征具有重要的影响. 此外, 对比发现日月距离对研究区的有效太阳辐照和电场环境的影响比季节效应的影响更大. 这可为将来无人和载人月球探测任务的时间选择、着陆点环境特征模拟、太阳能利用、月表尘埃环境预警预报等提供一定的支撑和依据.