月表主要硅酸盐矿物中太阳风成因水的实验对比研究

Recently infrared spectroscopic measurements of lunar surface provide evidence for the presence of hydroxyl and water produced by solar-wind proton implantation. The OH/H2O absorption characteristics show obvious differences in lunar mare and highland associated with the main silicate-mineral compositions. However, the formation conditions, abundance, form, chemistry position and stability of solar wind-produced water among lunar main silicates minerals are still not known clearly. In order to solve this problem, this project intends to simulate the process of solar wind implantation by hydrogen bombardment into olivine, orthopyroxene, clinopyroxene and anorthite. We also simulate the temperature and solar radiation condition by heating stage and vacuum ultraviolet. Infrared Spectrometer, Raman Spectrometer, Secondary Iron Microprobe and Transmission Electron Microscope would be used to analyze the content, form, chemistry position and hydrogen isotope of water in the samples. The differences involved formation conditions, abundance, form, chemistry position and stability of solar wind-produced water among lunar main silicates minerals would be determined, which is the basis for the interpretation of remote sensing. This study will provide the foundation to evaluation for the source of lunar polar water ice, and help us to further understanding of solar wind-produced water on the surfaces of airless bodies in solar system.

针对太阳风成因水在形成条件、含量、形态、化学位置和稳定性特征及其在矿物间的差异的认识不足这一现状，本项目拟以橄榄石、斜方辉石、单斜辉石和钙长石四种月表主要硅酸盐矿物为研究对象，采用离子注入技术模拟太阳风质子的注入作用，分析注入氢离子在矿物中形成水的条件，探讨水在矿物中的含量、形态和化学位置特征，进一步通过加热和UV辐射模拟月球表面温度和辐射环境，探讨离子注入形成水的稳定性，分析其逃逸速率以及逃逸过程中氢同位素分馏特征，确定四种硅酸盐矿物在太阳风注入过程中形成水的条件、含量、状态和化学位置以及稳定性的差异，为正确解释红外光谱探测数据中OH/H2O的吸收特征在月海和高地地区的变化差异提供依据，也为评估月球极区水冰来源和理解太阳系无大气天体表面太阳风成因水特征提供重要基础。

近年来，Cassini、Deep Impact 和Chandrayaan-1的红外光谱探测获得了月表水的重大发现，即月球全球表面普遍存在2.8μm 附近OH 和3μm 附近H2O 的吸收信号，并认为这些OH /H2O 形成于太阳风质子与月表含氧物质之间的相互作用，但是缺乏对不同物质成分中太阳风成因水形成条件、含量、形态和化学位置以及稳定性的系统研究。本项目针对这一问题开展了相关研究，结合理论计算和模拟实验以及相关的红外光谱、拉曼光谱、纳米离子探针、扫描电镜和透射电镜等一系列测试分析，获得了月表主要矿物和玻璃中太阳风成因水的含量、状态和剖面分布特征以及矿物表面结构的变化，探讨了了太阳风质子与硅酸盐矿物相互作用过程和形成水的作用机制，分析了月表温度对太阳风成因水逃逸和保存的影响以及该作用过程中的氢同位素分馏特征。这些研究成果对于深入认识月表太阳风成因水的状态、含量、分布和稳定性提供了重要的基础，同时也为研究月表水的成因过程和迁移运动等研究提供了重要依据，同时为月表水的红外光谱探测和数据的正确解译提供了参考。