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

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 (An(50)(-5)(3)) was used as a lunar analogue and was irradiated with 5 keV H+ at a fluence of similar to 1 x10(17 )H(+)/cm(2). 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 similar to 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 pm) and Type II H2O (similar to 2.90 mu m); 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. (C) 2021 Elsevier B.V. All rights reserved.