16 / 2026-03-03 10:03:21

Radiation-Induced Formation and Retention of Molecular Water in Chang’e-6 Anorthite: Insights from Ion Implantation Effects

Radiation-induced defects，,Space weathering，,Hydrogen speciation，,Solar-wind implantation，,Chang’e-6 farside samples

极端条件下的基础物理 > 辐射与高能粒子产生

Solar-wind ion implantation is traditionally viewed as the primary driver of lunar surface hydration, yet the underlying mechanisms for generating and preserving stable molecular H₂O in silicate lattices remain elusive. In this study, we investigate the radiation-induced evolution of volatiles in anorthite grains returned by the Chang’e-5, Apollo 11, and the recent farside Chang’e-6 missions.

Using microscale nuclear magnetic resonance (μQ-NMR)^[1-2], we performed high-precision quantification of hydrogen (H) and helium (He) inventories and resolved H-speciation at the single-grain level. Our results reveal a striking divergence: while nearside anorthites predominantly host H as structurally bound hydroxyl (OH^-), grains from the farside (Chang’e-6) preferentially stabilize molecular H₂O, despite possessing lower total volatile inventories. This speciation shift is accompanied by a systematic H-He decoupling, signaling a transition from simple implantation-controlled retention to energy-driven defect evolution.

First-principles simulations (AIMD) and ion-implantation modeling (SRIM) suggest that energetic space weathering generates high-density lattice distortions and unsaturated Aluminum (Al) sites. These radiation-induced defects act as high-energy traps that facilitate the in-situ synthesis of H₂O and provide the necessary kinetic barriers for its long-term stabilization under extreme vacuum and thermal conditions. These findings demonstrate that energetic radiation processing provides an independent, defect-mediated pathway for volatile evolution on airless bodies, offering new perspectives on material responses to complex radiation environments in space.