NASA has discovered fresh evidence that a crater near the Moon’s south pole is packed with frozen water. Results from their spaceprobe Lunar Reconnaissance Orbiter suggest that as much as 22 per cent of Shackleton crater’s surface is made up of ice. 

The Moon’s south polar region pictured from Japan’s Kaguya prob. Credit: JAXA

The presence of the water would give a major boost for future plans to set up a colony on the Moon, a world once thought completely dry, because it would reduce the need to ferry water from Earth.

However, experts agree that it will be a challenge to get at the ice because the crater, named after Antarctic explorer Ernest Shackleton, has an unfriendly shape and much of it has been in permanent darkness for billions of years.

Much of the crater, which is 12 miles wide and two miles deep, lies in constant shadow where sunlight never penetrates. This has prevented the ice from evaporating into space when the rest of that region of the Moon is enjoying daylight.

Maria Zuber, of the Massachusetts Institute of Technology, the lead investigator of a team to investigate the LRO findings, said: “The crater’s interior is extremely rugged. It would not be easy to crawl around in there.” Their results are published today in Nature.

In October 2009, NASA crashed another probe, LCROSS, and its two-ton Centaur rocket stage into a nearby 60-mile wide crater called Cabeus and detected clear signs of water in the cloud of debris produced by the impacts.

False colour image reveals different heights in Shackleton crater, with blue lowest and red highest. Credit: NASA/Zuber, M.T. et al., Nature, 2012

The European Space Agency is planning a robotic Lunar Lander mission to visit the region and find water in preparation for later visits by astronauts.

Water is actually widespread across the Moon. The existence of water molecules was revealed by a sensitive NASA spectrometer aboard India’s Chandrayaan-1 probe which produced a colour map of the surface indicating the chemical make-up. The result showed the presence of both water and a closely related molecule called hydroxyl, which contains just one atom of hydrogen to an atom of oxygen, all over the Moon’s surface. The water is believed to be produced when a radiation from the Sun, called the solar wind, batters the Moon. This contains hydrogen which reacts with oxygen in the lunar rocks.

A special form of water called hydroxyls has also been discovered locked away in lunar lava by American geologists who studied basalt rocks brought back by Apollo 14 astronauts in 1971.