Solar wind implantation-diffusion at middle latitudes on the lunar surface: evidence from D+ implantation experiments

ABSTRACT Studies of Chang’e-5 samples have indicated a high content of solar wind-derived water at middle latitudes on the lunar surface. However, the implantation-diffusion and retainment of solar wind-derived water at lunar daytime temperatures remains unclear, leaving the formation and preservation of solar wind-derived water in minerals poorly understood. Here, we conducted experiments on 1.5 keV deuterium (D) ions implanted into silicate minerals at 356 K to simulate the solar wind proton implantation at noon in the middle latitudes of the Moon. The results showed that OD formed and partial D reached several micrometers depth in the minerals after implantation, which was a result of radiation-enhanced diffusion. The diffusion coefficient was estimated to be 10$^{-11}$–10$^{-12}$ cm$^{2}$ s−1 and was affected by the implantation fluence, temperature, and mineral crystal structure. This study provides insights into the distribution of water on the lunar surface by investigating the formation and diffusion of solar wind-derived water preserved in different minerals at elevated temperatures.