Analyzing grains of soil collected from three Apollo lunar missions, geochemists have figured out that the hydrogen in trace amounts of water on the moon’s surface probably came from solar wind, the outflow of positively-charged hydrogen from the sun.
For decades, scientists didn't find much hydrogen in the lunar samples that had been returned to Earth, said Yan Liu, a research professor at the University of Tennessee and lead author of the lunar water study, which was published Sunday in Nature Geoscience.
Source: LA Times. Read full article. (link)