There's a lot more water in the moon's interior than previously believed, say scientists at the Carnegie Institution’s Geophysical Laboratory.
Their research suggests that the water, which is locked up in lunar rocks, came from the hot magma that was present when the Moon began to form some 4.5 billion years ago.
"For over 40 years we thought the Moon was dry. The bulk water content of the Moon was estimated to be less than 1 ppb, which would make the Moon at least six orders of magnitude drier than the interiors of Earth and Mars," says lead author Francis McCubbin.
The researchers looked at hydroxyl in the mineral apatite — the only hydrous mineral found in two Apollo samples and a lunar meteorite.
Using secondary ion mass spectrometry (SIMS), the team found that the minimum water content ranged from 64 parts per billion to five parts per million — vastly more than had been expected.
The prevailing belief is that the Moon came into existence when a Mars-sized object hit the Earth and ejected material which coalesced into the moon.
From two of the samples, the Carnegie scientists determined that water was probably present very early on as the hot magma started to cool and crystallize. This means that water is native to the Moon.
"It is gratifying to see this proof of the OH contents in lunar apatite," says lunar scientist Bradley Jolliff of Washington University in St. Louis. "We can now finally begin to consider the implications — and the origin — of water in the interior of the Moon."