Ref: M. Claussidon, Nature 454, 2008, 170. News and Views commentary on Saal et al p192 same volume.
The moon has 1.5 times the elements likely to condense from a gas first such as aluminium and titanium and is considered volatile poor when compared with the Earth. This chemical make up along with an oxygen isotope signature almost identical to the Earth’s supports the theory that the Moon formed from the high temperature debris ejected when a Mars sized planet hit a 30 million year old proto Earth. So Saal et al’s analysis of probably volcanic glass collected from green (Apollo 15) and orange (Apollo 17) lunar soil samples that shows high water content is a surprise.
Saal et al found significant amounts of chlorine, fluorine and sulphur as well as the water deep within the glass, and modelling for outgassing found water concentrations around 750ppm which is similar to concentrations found in such glass in basalts on the Earths mid ocean ridges which is taken as a good indicator of the Earth’s mantle composition.