Lunar water formation by solar wind: nuclear reaction analysis of deuterium ion interactions with lunar-like glass

Introduction The interaction of solar wind with lunar regolith plays a pivotal role in shaping the Moon's volatile inventory, yet the mechanisms governing water formation and retention remain incompletely understood. This study investigates the implantation and thermal behavior of solar wind–derived hydrogen species in lunar analog materials to better understand processes contributing to lunar surface hydration. Methods Controlled laboratory experiments were conducted using synthetic lunar‐like glass and olivine samples. The materials were irradiated with deuterium ions at energies representative of solar wind protons, allowing discrimination between irradiation‐induced and pre‐existing hydrogen species. Post‐irradiation characterization was performed using Nuclear Reaction Analysis (NRA), Rutherford Backscattering Spectroscopy (RBS), and Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) to obtain depth‐resolved profiles of deuterium distribution. Thermal desorption experiments were subsequently carried out to evaluate the stability and mobility of implanted species during heating. Results The implanted deuterium was found to be confined to the upper few hundred nanometers of both materials. Peak deuterium concentrations reached approximately 10–12 at% in both lunar‐like glass and olivine, despite differences in irradiation fluence. Thermal desorption experiments revealed substantial depletion of near‐surface deuterium upon heating. No evidence of significant deep diffusion was observed within the detection limits of Nuclear Reaction Analysis. Discussion and Conclusions The results support the hypothesis that lunar impact glass beads can serve as transient reservoirs for solar wind–derived water, contributing to the dynamic hydration cycle observed on the Moon. The confinement of implanted hydrogen to near‐surface regions and its subsequent release during heating provide important constraints on volatile retention mechanisms in lunar materials. Methodological challenges identified during the study and proposed improvements offer a foundation for refining experimental approaches and advancing models of volatile evolution on airless planetary bodies.