Untangling the formation and liberation of water in the lunar regolith.

The source of water (HO) and hydroxyl radicals (OH), identified on the lunar surface, represents a fundamental, unsolved puzzle. The interaction of solar-wind protons with silicates and oxides has been proposed as a key mechanism, but laboratory experiments yield conflicting results that suggest that proton implantation alone is insufficient to generate and liberate water. Here, we demonstrate in laboratory simulation experiments combined with imaging studies that water can be efficiently generated and released through rapid energetic heating like micrometeorite impacts into anhydrous silicates implanted with solar-wind protons.