Experimental investigation of OH/H2O in H+-irradiated plagioclase: Implications for the thermal stability of water on the lunar surface

1,3Xiandi Zeng,1,2,4Hong Tang,1,2,4Xiong Yao Li,1Xiaoji Zeng,1,2,4Wen Yu,1,2,4Jianzhong Liu,5Yongliao Zou
Earth and Planetary Science Letters Link to Article [https://doi.org/10.1016/j.epsl.2021.116806]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
2CAS Center for Excellence in Comparative Planetology, Hefei, China
3University of Chinese Academy of Sciences, Beijing 100049, China
4Key Laboratory of Space Manufacturing Technology, Chinese Academy of Sciences, Beijing 100094, China
5National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Copyright Elsevier

Determining the characteristics and thermal stability of solar wind-produced OH/H2O is critical to understanding the formation and migration of water on the lunar surface. In this study, terrestrial plagioclase (An50−53) was used as a lunar analogue and was irradiated with 5 keV H+ at a fluence of ∼1×1017 H+/cm2. The irradiated plagioclase was characterized via Fourier transform infrared spectroscopy, nanoscale secondary ion mass spectrometry, Raman spectroscopy, and transmission electron microscopy. The thermal stability of OH/H2O in the irradiated plagioclase was investigated via heating experiments. Our results reveal (1) a ∼100–200 ppm increase in the water content of the irradiated plagioclase; (2) structural hydrous species formation in the plagioclase through H+ implantation, including Type I H2O (∼2.75 μm) and Type II H2O (∼2.90 μm); and (3) the escape of much of the OH/H2O formed by H+ implantation at a temperature equivalent to the highest temperature on the lunar surface. The results of this study can improve our understanding of OH/H2O thermal stability on the lunar surface and provide a baseline for the interpretation of remote sensing observations.

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