Moon May Have 100 Times More Water Than We Thought. How’d We Miss It?

1969: "We landed on the moon. It's dry." 2008: "Excellent, we were wrong: It's not totally dry." 2010: "Actually, we may have been very wrong about that: There could be even hundreds of times more water there than we thought." That last statement is the latest in a rising tide of announcements of water on the moon; DISCOVER covered when the news broke in March, and now the study is out in the Proceedings of the National Academy of Sciences. To sum up: After reanalyzing moon samples from the Apollo landings and meteorites of lunar origin, a team led by Francis McCubbin calculated a water content of 64 parts per billion to 5 parts per million. That's paltry compared to even the driest places on Earth. But, they write, "This lower limit range of water contents is at least two orders of magnitude [100X] greater than the previously reported value for the bulk Moon, and the actual source region water contents could be significantly higher." As exciting as that is, it raises the question: How did we miss this for 41 years? First, this water is not sloshing around in some subsurface ocean; it's locked up in lunar minerals: