Washington: A new study has revealed that the inside of the moon isn`t as watery as previously reported.
For decades, astronomers had thought the moon is bone dry inside and out. However, recent moon-impact missions found water ice on the lunar surface, and reanalysis of rocks brought back by Apollo astronauts found evidence for significant amounts of water inside the moon in the form of hydroxyl (-OH), a hydrogen compound formed by the breakdown of water (H2O).
In a new study of Apollo moon rocks, geochemist Zachary Sharp of the University of New Mexico and colleagues measured the moon rocks`` chlorine isotopes, or different forms of the chlorine atom.
Chlorine is strongly attracted to hydrogen. As magma cools and solidifies, hydrogen and chlorine present in the molten rock tend to bond to form hydrogen chloride gas.
On Earth, volcanic magma contains more hydrogen than chlorine, so most of the chlorine bonds with hydrogen. Due to the nature of the bond, the ratio of chlorine isotopes left behind in the cooling rock is about the same as the ratio that gets released as gas.
"We analyzed the moon, and we found that the chlorine isotope values vary by 25 times more than the Earth`s," National Geographic News quoted Sharp as saying.
The best way to explain this result is that the rocks, formed as the moon cooled 4.5 billion years ago, are low in hydrogen.
Instead of becoming mostly hydrogen chloride gas, the chlorine in lunar magma was free to bond with other elements and form salts such as iron chloride and zinc chloride, leading to a wider range of chlorine isotopes in the rock.
And if moon rocks lack hydrogen, they must lack water, the study concluded.
The findings have been published online by the journal Science.