The evolution of water and molecular hydrogen from Apollo lunar sample 15221, a mature mare soil, was examined by temperature program desorption (TPD) experiments conducted under ultra-high vacuum conditions. Desorption at the grain/vacuum interface with re-adsorption as water transports though the void space of the grains and activated sub-surface diffusion were found to reproduce the experimental TPD signal. Signal from the grain/vacuum interface yielded the second order desorption activation energies and site probability distributions. Water from sample 15221 exhibited a broad distribution of activation energies peaking at 130 kJ mol⁻¹ extending up to 350 kJ mol⁻¹ at zero coverage limit with an onset of 110 kJ mol⁻¹ at full coverage. Our results suggest that water and hydrogen originating from lunar regolith contributes a minor amount to the observed mass in the LCROSS impact event. The abnormal amount of molecular hydrogen observed in the ejecta plume of the LCROSS impact may indicate that the radiolytic production of H₂ from electron and galatic cosmic rays of physisorbed water is a contributor to the vast quantity of molecular hydrogen detected.

阿波罗月球样品 15221 是一种成熟的母马土壤，水和分子氢的演化通过在超高真空条件下进行的温度程序解吸 (TPD) 实验进行了检查。发现在颗粒/真空界面处的解吸以及随着水通过颗粒的空隙空间和激活的亚表面扩散而重新吸附，再现了实验 TPD 信号。来自颗粒/真空界面的信号产生了二阶解吸活化能和位点概率分布。来自样品 15221 的水表现出广泛的活化能分布，峰值为 130 kJ  mol ^-1，在零覆盖极限下扩展至 350 kJ  mol ^-1，起始值为 110 kJ  mol ^-1全覆盖。我们的结果表明，来自月球风化层的水和氢对 LCROSS 撞击事件中观测到的质量贡献很小。在 LCROSS 撞击的喷射羽流中观察到的异常数量的分子氢可能表明，物理吸附水的电子和银河宇宙射线辐射分解产生的 H ₂是检测到的大量分子氢的一个贡献者。