The distribution of water in the Moon’s interior carries implications for the origin of the Moon¹, the crystallization of the lunar magma ocean² and the duration of lunar volcanism². The Chang’e-5 mission returned some of the youngest mare basalt samples reported so far, dated at 2.0 billion years ago (Ga)³, from the northwestern Procellarum KREEP Terrane, providing a probe into the spatiotemporal evolution of lunar water. Here we report the water abundances and hydrogen isotope compositions of apatite and ilmenite-hosted melt inclusions from the Chang’e-5 basalts. We derive a maximum water abundance of 283 ± 22 μg g⁻¹ and a deuterium/hydrogen ratio of (1.06 ± 0.25) × 10^–4 for the parent magma. Accounting for low-degree partial melting of the depleted mantle followed by extensive magma fractional crystallization⁴, we estimate a maximum mantle water abundance of 1–5 μg g⁻¹, suggesting that the Moon’s youngest volcanism was not driven by abundant water in its mantle source. Such a modest water content for the Chang’e-5 basalt mantle source region is at the low end of the range estimated from mare basalts that erupted from around 4.0 Ga to 2.8 Ga (refs. ^5,6), suggesting that the mantle source of the Chang’e-5 basalts had become dehydrated by 2.0 Ga through previous melt extraction from the Procellarum KREEP Terrane mantle during prolonged volcanic activity.

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 × 10¹⁴ 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.

Remote sensing data revealed that the presence of water (OH/H ₂ O) on the Moon is latitude-dependent and probably time-of-day variation, suggesting a solar wind (SW)-originated water with a high degassing loss rate on the lunar surface. However, it is unknown whether or not the SW-derived water in lunar soil grains can be preserved beneath the surface. We report ion microprobe analyses of hydrogen abundances, and deuterium/hydrogen ratios of the lunar soil grains returned by the Chang’e-5 mission from a higher latitude than previous missions. Most of the grain rims (topmost ~100 nm) show high abundances of hydrogen (1,116 to 2,516 ppm) with extremely low δD values (−908 to −992‰), implying nearly exclusively a SW origin. The hydrogen-content depth distribution in the grain rims is phase-dependent, either bell-shaped for glass or monotonic decrease for mineral grains. This reveals the dynamic equilibrium between implantation and outgassing of SW-hydrogen in soil grains on the lunar surface. Heating experiments on a subset of the grains further demonstrate that the SW-implanted hydrogen could be preserved after burial. By comparing with the Apollo data, both observations and simulations provide constraints on the governing role of temperature (latitude) on hydrogen implantation/migration in lunar soils. We predict an even higher abundance of hydrogen in the grain rims in the lunar polar regions (average ~9,500 ppm), which corresponds to an estimation of the bulk water content of ~560 ppm in the polar soils assuming the same grain size distribution as Apollo soils, consistent with the orbit remote sensing result.

An exceedingly small number of high‐pressure polymorphs have been discovered in lunar samples. This situation does not seem to reconcile with the prolonged, intense bombardment of the lunar surface, which should produce suitable conditions for the formation of such polymorphs. Here we report the discovery of reidite, a high‐pressure polymorph of ZrSiO₄ with scheelite structure in lunar meteorite Sayh al Uhaymir (SaU) 169. The reidite occurs mainly as lamellae hosted within zircon, likely corresponding to a deviatoric‐dominated transformation. The presence of reidite in the regolith portion of SaU 169 indicates a narrow temperature and pressure path constrained by the phase stability under low pressure and suggests heterogeneous shock features in the porous lunar regolith where the ambient temperature increases much higher than that in compact rocks. The inventory of high‐pressure polymorphs might be restricted by such unusual cooling processes lunar samples experienced.

Lunar mare basalts illuminate the nature of the Moon’s mantle, the lunar compositional asymmetry and the early lunar magma ocean (LMO)^1,2,3. However, the characteristics of the mantle beneath the vast South Pole–Aitken (SPA) basin on the lunar farside remain a mystery. Here we present the petrology and geochemistry of basalt fragments from Chang’e-6 (CE6), the first returned lunar farside samples from the SPA basin^4,5,6,7. These 2.8-billion-year-old CE6 basalts⁸ share similar major element compositions with the most evolved Apollo 12 ilmenite basalts. They exhibit extreme Sr–Nd depletion, with initial ⁸⁷Sr/⁸⁶Sr ratios of 0.699237 to 0.699329 and ε_Nd(t) values (a measure of the neodymium isotopic composition) of 15.80 to 16.13. These characteristics indicate an ultra-depleted mantle, resulting from LMO crystallization and/or later depletion by melt extraction. The former scenario implies that the nearside and farside may possess an isotopically analogous depleted mantle endmember. The latter is probably related to the SPA impact, indicating that post-accretion massive impacts could have potentially triggered large-scale melt extraction of the underlying mantle. Either way, originating during the LMO or later melt extraction, the ultra-depleted mantle beneath the SPA basin offers a deep observational window into early lunar crust–mantle differentiation.