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.

Automated summary

The study demonstrated an increase in water content and formation of hydrous species in irradiated plagioclase, as well as the escape of OH/H2O at high temperature, providing insights into the thermal stability of water on the lunar surface and aiding in the interpretation of remote sensing observations.