The moon is not, after all, as dry as dust. An American instrument on India’s first lunar satellite has detected surprisingly large amounts of water locked up in the moon’s rocks and soils.
The discovery, announced in three research papers in the online edition of the journal Science, will encourage those who want to establish human colonies on the moon.
The US Moon Mineralogy Mapper on the Indian Chandrayyan-1 satellite detected the presence of water from the way light is reflected from the lunar surface. This was confirmed by observations from two other space probes, Deep Impact and Cassini.
“This is a major discovery that will have a significant impact on international plans for exploration of the Moon,” said Marc Norman, a lunar researcher at the Australian National University. “One caveat – it is important to realise that this is not liquid water like our oceans, nor ice like on the Mars polar caps. Rather this water on the moon appears to be bound up with minerals,” he said.
But scientists speculated that it would be possible to extract the water from the lunar soil, both for use directly and as a source of fuel by splitting into its component hydrogen and oxygen with solar energy.
Although traces of water were found in moon rocks brought back by the Apollo missions 40 years ago, these were dismissed then as contamination from moisture in the air after the samples returned to Earth.
“To some extent we were fooled,” said Larry Taylor of the University of Tennessee, who studied the original Apollo materials and is part of the current Moon Mineralogy Mapper team. Scientists assumed wrongly that the lunar surface was completely dry, with the possible exception of some ice buried beneath the poles and in soil shaded by crater walls, which never receives sunlight.
The scientific question now is where the lunar water came from. Some may have been delivered in the icy comets and meteorites that have bombarded the moon for billions of years, but researchers believe that most of the water originated in chemical reactions on the moon itself.
Lunar rock contains a lot of oxygen, chemically bound in minerals, and scientists think the hydrogen may have come in the “solar wind” from the sun. Traces of water would have been formed when the oxygen and hydrogen combined on the moon’s surface.
More information should emerge next month when a US probe is due to hit a crater near the moon’s south pole. Scientists will analyse the resulting plume of dust for more signs of water.