Evidence of moon water found
2008-07-10 09:12
Paris - The ancient astronomers once deemed the Moon, like Mother Earth, to be awash with water and gave fanciful names to its "seas".
The space age, of course, revealed these oceans, or Mare, to be desolate, bone-dry basalt plains - and ever since, the Moon has been saddled with the reputation as a hostile place forever lacking a key ingredient for life.
But this image may need a makeover, if some of the hopes sketched in a new scientific study turn out to be true.
Published on Thursday in the British weekly journal Nature, the paper puts forward evidence that water has been a part of the Moon since its early existence.
And it strengthens speculation that the precious stuff may be found at the lunar poles.
A leading theory is that the Moon was created when a Mars-sized object whacked into the infant Earth, some 4.5 billion years ago, sending molten debris into orbit that coalesced and cooled to form our planet's satellite.
The violence of this collision would have vaporised the proto-Moon's light elements, including those for water, in a flash.
But a close examination of glassy, pebble-like beads brought back by the Apollo missions has revealed a surprise.
Previous examination of these rocks - the result of a volcanic outpouring some 3.5 billion years ago - had found no signs of water, a finding consistent with the "waterless Moon" scenario.
Geologists led by Alberto Saal at Brown University, Rhode Island, have taken a new look, this time using a souped-up version of a method called secondary mass ion spectrometry 10 times more sensitive than previous versions.
Trace of far larger concentrations
They found minute but intriguing concentrations of water in the pebbles, "up to 46 parts per million [ppm]," said Erik Hauri of the Carnegie Institution for Science.
The team say that this water is a trace of far larger concentrations that must have existed in the Moon's interior before the fire fountains swept into action.
According to their calculation, the Moon's pre-eruption magna may have contained up to 750 ppm, similar to the water content of primitive magma that once erupted on the mid-ocean ridges on Earth's sea floor.
Lacking an atmosphere, the Moon lost almost all of this water when the molten rock spewed onto the surface and cooled.
As much as 95% of the vapour drifted out to space and was lost forever.
But - so goes the theory - the rest may have drifted towards the cold poles of the Moon, where it may remain as ice in deep, permanently shadowed craters.
The notion of ice at the lunar poles was once dismissed as fanciful, but it has gained credibility in recent years, backed by data sent back in 1994 by a US orbiter, Clementine.
Seeking to find out more, Nasa is to send a scout, the Lunar Reconnaissance Orbiter, with a launch date of no earlier than November 24 this year, followed by another craft, the Lunar Crater Observation and Sensing Satellite, in 2009.
Finding water would be a boon, and not just for the tantalising perspective that it would open into Moon's past.
It could conceivably be tapped for a manned outpost, thus drastically cutting the cost of a permanent return to the Moon.