Sun may make most of the water on moon’s surface

Bombardement by particles from the sun — not comets and meteorites — may be the main source of water locked with the moon’s rocks.

Lunar soil may hold, on average, only 15 percent of the hydrogen that comets and meteorites delivered billions of years ago, researchers report October 6 in the Proceedings of the National Academy of Sciences. Protons from the solar wind that combine with oxygen on the lunar surface may generate the rest of the water, the scientists suggest.