Moon richer in water than once thought

There may be far more water on the Moon than previously thought, according to two studies published Monday raising the tantalising prospect that astronauts on future space missions could find refreshment -- and maybe even fuel -- on the lunar surface.  

The Moon was believed to be bone dry until around a decade ago, when a series of findings suggested that our nearest celestial neighbour had traces of water ice in permanently-shadowed craters at its polar regions.

Two new studies published in Nature Astronomy on Monday suggest water could be even more widespread, including the first confirmation that it is present even in easier-to-access sunlit areas.  

If this water could be extracted, it could give astronauts travelling to the Moon and beyond access to drinking water. They might even be able to split the molecules to make rocket fuel.

That is of particular interest to Nasa, which is planning a human mission to the Moon in 2024 and wants to build a sustainable presence there by the end of the decade to prepare for onward travel to Mars.

The new study was able to "unambiguously" distinguish the spectral fingerprint of molecular water in a sunlit area, said lead author Casey Honniball, of the Hawaii Institute of Geophysics and Planetology.

"If we find the water is abundant enough in certain locations we may be able to use it as a resource for human exploration," Honniball, who is also a postdoctoral fellow at Nasa's Goddard Space Flight Center, told AFP.

Previous research has found indications of water on the sunlit surface -- but these were unable to distinguish between water (H2O) and hydroxyl, a molecule made up of one hydrogen atom and one oxygen atom that is a common drain cleaner on Earth. 

Using data from the Stratospheric Observatory for Infrared Astronomy (SOFIA) Airborne Telescope, researchers used a more precise wavelength than had been used before -- 6 microns instead of 3.

They found a water concentration of about 100 to 400 parts per million at Clavius crater, one of the largest to be visible from Earth.

"That's roughly equivalent to a 12 ounce (350 millilitre) bottle of water within a cubic meter of volume of lunar soil," Honniball said in a NASA press conference.

These are not "puddles of water", she stressed, but scattered molecules that do not form ice or liquid water.

The authors say approximately 40,000 km2 of the lunar surface has the capacity to trap water.