Overview
Most scientists assume that the Moon contains only small amounts of free water. Besides possible ice in permanently shadowed polar craters, the bulk of lunar water is likely chemically bound in deep interior layers.
Evidence and Measurements
Analyses of Apollo rock samples and data from instruments such as the Lunar Reconnaissance Orbiter show elevated concentrations of hydroxyl and other water‑bearing minerals in the subsurface. These signals are best explained by water trapped in silicate crystal lattices or within glass.
Implications for Future Missions
If the water is indeed locked inside the Moon, it must first be released by heating or chemical processes before it can be used for life support or propellant production. This raises the technical effort compared with simply extracting ice from surface deposits.
Outlook
Future work, including drilling missions and seismic studies, aims to quantify the exact amount and binding state of interior water. Only then can the true resource potential of the Moon be assessed.