Hi guys

Solar wind chemistry on the surface is another possible source - hot hydrogen can react with the oxides in the regolith to make water and the H2O will then ballistically hop along until it gets stuck in a cold trap or is dissociated and blown away. On Mercury the same process is perhaps dominant and helped by being concentrated around the poles where the magnetic field channels all the captured ions.

Another source that has recently surfaced is from volatile emissions from the Moon's guts. Astronomers have finally confirmed transient lunar emissions and the recent find of water in lunar glass hints at some water deep down. Thus there's a real chance it'll get cold-trapped before it's blown away.