A solar wind-derived water reservoir on the Moon hosted by impact glass beads

Analysis of lunar soils sampled by the Chang'e-5 mission suggests that impact glass beads may host a substantial inventory of solar wind-derived water on the Moon's surface. The past two decades of lunar exploration have seen the detection of substantial quantities of water on the Moon's surface. It has been proposed that a hydrated layer exists at depth in lunar soils, buffering a water cycle on the Moon globally. However, a reservoir has yet to be identified for this hydrated layer. Here we report the abundance, hydrogen isotope composition and core-to-rim variations of water measured in impact glass beads extracted from lunar soils returned by the Chang'e-5 mission. The impact glass beads preserve hydration signatures and display water abundance profiles consistent with the inward diffusion of solar wind-derived water. Diffusion modelling estimates diffusion timescales of less than 15 years at a temperature of 360 K. Such short diffusion timescales suggest an efficient water recharge mechanism that could sustain the lunar surface water cycle. We estimate that the amount of water hosted by impact glass beads in lunar soils may reach up to 2.7 x 10(14) kg. Our direct measurements of this surface reservoir of lunar water show that impact glass beads can store substantial quantities of solar wind-derived water on the Moon and suggest that impact glass may be water reservoirs on other airless bodies.

Automated summary

Analysis of lunar soils returned by the Chang'e-5 mission suggests that impact glass beads on the Moon's surface may contain a significant amount of solar wind-derived water. This finding supports the existence of a hydrated layer in lunar soils that plays a role in the global water cycle on the Moon. The study also reveals that impact glass beads can serve as reservoirs for water on other airless bodies.