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Water discovered in Apollo-era moon rocks |
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Written by Derek Kessler on
Sunday, 20 July 2008
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 (From July 9, 2008) For the first time ever, water has been conclusively uncovered in samples Apollo astronauts brought back from the moon. Found inside volcanic glass beads, formed from magma in the interior o of the early moon, the discovery of water was a surprise even to the researchers who came across it. The assumption has always been that the moon is and was always dry, a consequence of it’s violent birth.
4.5 billion years ago, a planetoid named Theia - about the size of Mars - smacked into the proto-Earth. Theory holds that all planets are formed by the collision and accretion of smaller rocky bodies into larger ones. The leading theory behind the origin of the moon, however, states that Earth and Theia hit so hard that massive amounts of debris were thrown into the space around the Earth. The debris eventually congregated into the moon. Because the impact that created the moon would have released massive amounts of energy and melted both Earth and Theia, any water present would have been vaporized. And once the moon solidified without an atmosphere, any water would have simply evaporated into space.
But, the presence of water in ancient volcanic glass seems contrary to such thoughts. The researchers studying the beads made sure that their elemental chemical composition showed that they were from now-extinct lunar volcanoes and not from the violent formation of the moon. Using a technique called secondary ion mass spectrometry, the team was able to increase the sensitivity of their search from 50 parts per million (ppm) to just 5 ppm of water to other material. When they started to analyze the beads, they found water concentrations of up to 46 ppm. Calculations indicate that upon formation, the beads could have contained at least 260 ppm of water, or all the way up to 645 ppm – as much of the water vapor would have escaped as gas as the glass beads solidified.
Computer models indicate that the proto-Earth would have held on to most of its water through the impact, so it’s a mystery where the water on the moon may have come from. So either Theia came with its own supply of water that in some part survived the impact, or it managed to strip and retain some water from Earth. Even then, the question remains about the beads: are they representative of the entire moon, or some rare water-rich pocket within the moon’s interior?
Knowing more about the presence of water could have implications for future moon missions, especially the permanent manned outpost planned by NASA.
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