It has been known for a while that water has existed on the surface of the moon. Some frozen water deposits are in large quantities in the bottom of craters that receive very little sunlight and there are smaller deposits throughout the surface of the moon. Over the years the thought has been that water was brought to the moon from impacts with asteroids and comets that carried the water. With the Apollo missions NASA brought back multiple rock and regolith samples that we have analyzed. Recent analysis of the rock and regolith samples have made a new discovery.
Recent research from Astrochemists Alice Stephant and François Robert from Muséum National d’Histoire Naturelle in Paris have discovered that most of the water on the lunar surface actually comes from the solar winds. The solar wind itself does not carry water molecules but instead causes chemical reactions inside the lunar rock and regolith lying on the surface. The high energy solar wind impacts the highly silicate rocks and regolith on the lunar surface which separates some of the Oxygen molecules from the silicate which then can combine with the hydrogen molecules found throughout the lunar surface to eventually create water. It has been estimated that up to 85 percent of the water on the lunar surface could be created by this process.
This new research does not state that all water on the moon is created by the solar wind reactions but only 85 percent of the water on the surface. That leaves the other 15 percent on the surface and water under the surface created from other sources like asteroids, comets, and other possible unknown sources.
The results can be found in the Proceedings of the National Academy of Sciences