Moon’s Water
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.