Thermophysical Properties Of Lunar Regolith And Simulation Of Its Vertical Temperature Distribution

Reconstruction of long-term Total Solar Irradiance (TSI) series is a significant foundation of studying the mechanism of how solar activities drive global climate change. Since there are no barriers of Atmosphere, adjustment of Hydrosphere, and influence of Biosphere, the solar radiation heats the lunar regolith directly. Therefore, the lunar borehole temperatures can be used as direct evidence of TSI records to reconstruct the TSI series, and moon-based reconstruction of TSI requiresthe changing rule of the lunar borehole temperatures.Vertical temperature distribution of lunar regolith profile is mainly related to the thermophysical properties of lunar regolith’s materials. This study used TPS2500S, the thermal conductivity analyzer, to run the test of thermophysical properties of material of lunar regolith, including powder samples of minerals on earth in six different particle fractions which were major minerals of the moon, such as Pyroxene, Olivine and Plagioclase, as well as lunar soil stimulantmade by China, United States and Japan, and gained reliable practical test data of thermophysical properties of material of lunar regolith, analyzed the effects of particle feature, temperature and composition of the mineralson it. This study, on one hand, stimulated basic data for relevant fields of moon exploration; on the other hand, it was an important parameter for the section model of lunar borehole temperature. This study shows thatthermal conductivity and heat capacity of the major mineral of the moon in general performance out a rising change-character with the increase of mineral dadius, while the thermal diffusivity acts out an opposite tendency; and changing laws of distinct minerals are some kind of different. The thermophysical properties of different lunar soil stimulants are close to each other, for they are low heat conductivity materials, whose thermal conductivity has a positive correlation with particle size; and temperature increasing, capacity of heat transfer will enhance, while ampulitude of thermophysical properties caused by temperature decreases.The lunar borehole temperature is a function of depth and time. The basic theory of thermal conduction is introduced. The study wrotea computer program and did the numerical calculation by using the Lunar Borehole Temperature Model, got the simulated results of lunar borehole temperatures at different periods and in different lunar latitudes, and simulated its vertical distributed character taking Sinus Iridum as the study area. Meanwhile, this study also analyzed the factors that influenced the vertical temperature distribution of lunar regolith, including composition of the mineral, particle feature, lunar soil stimulant and the character of thermophysical propertie scased by them, as well as the inner heat flow of the moon. As studies indicate, lunar borehole temperature in daylight appears as heat conductivity from surface towards inner, whereas it presents the opposite at night. The range of profile temperature around cloackdimishs from surface to deep, and it reaches a constant when down to the depth of0.5m to0.6m. The vertical temperature range decreases from low latitude to high latitude. Vertical temperature gradient of a specular lunar borehole temperature is higher, whose thermal conductivity is larger.Based on the above results, this study finally analyzed the problems existing in the research process, and proposed the research prospects. For example, we will explore the regularity of vertical temperature distribution of lunar regolith profile in terms of mechanism, eliminating the noise which is not caused by solar radiation, and will take it as direct evidence of TSI records to reconstruct the TSI series; besides, we will form both lunar surface temperature model and lunar borehole temperature model within m-scale accuracy.