Chinese scientists said most of the molecules reached the Moon through a procedure called solar wind implantation. The sun’s charged debris carried the hydrogen atoms to the lunar surface, where they then bound to oxygen to form water and hydroxyl. The study builds on findings published through NASA in 2018 when it discovered evidence of water on the Moon’s sunlit surfaces using an airborne infrared telescope. For decades, scientists on the Moon were completely dry due to its almost non-existent atmosphere. there was nothing to protect the water molecules from the sun’s rays.

Editor’s note: This article was originally published on Engadget.