What’s big, covered in water, yet 100 times drier than the Sahara Desert? It’s not a riddle, it’s the Moon! For centuries, astronomers debated whether water exists on Earth’s closest neighbor. In 2020, data from NASA’s SOFIA mission confirmed water exists in the sunlit area of the lunar surface as molecules of H2O embedded within, or perhaps sticking to the surface of, grains of lunar dust. Here is a brief history of the discoveries leading up to the confirmation of water on the Moon.