London, July 29 : The discovery that a prime real estate on the Moon is much older than previously thought, has led scientists to believe that the crater may be a very attractive site for a lunar colony, as it might offer a large supply of ice.
According to a report in Nature News, the conclusion is based on analysis of data from the SMART-1 mission.
The lunar site in question is the Shackleton crater, which is 20 kilometres across and sits near the Moon's south pole.
It is being eyed as a site for a lunar base because its bottom is permanently shadowed - a prerequisite for storing ice, if it exists there. Conversely, the crater's rim seems to benefit from almost year-round sunshine, essential for any solar-powered base.
Scientists led by Paul Spudis of the Lunar and Planetary Institute in Houston, Texas, have now used images from the European Space Agency's SMART-1 probe to work out the crater's age from a careful count of the smaller impact craters around it.
"We found it to be much older than previously thought," said team member Ben Bussey of the Applied Physics Laboratory in Laurel, Maryland.
The Solar System is full of debris that bombards all the bodies within it at roughly the same rate, so counting the craters and noting how they overlap can give an indication of age.
Previous estimates of the crater's age had ranged from less than 1 billion to 3.3 billion years old. But the more detailed images from SMART-1's Advanced Moon micro-Imager Experiment (AMIE) allowed the team to age Shackelton as roughly 3.6 billion years old.
This is good news for humans thinking about staying on the Moon for a while.
"There's been a lot more time for possible ice to accumulate, and over billions of years it is feasible that you could build up a significant reserve," said Bussey.
According to Manuel Grande of the University of Wales, Aberystwyth, UK, who worked on the SMART-1 mission, Bussey's theory that an older crater will have allowed more ice to accumulate will stand up only if the ice came to the Moon on comets.
"Future data will come from the Japanese space agency and its Kaguya mission, launched in September 2007," said Bussey.
Other future Moon fact-finding missions include NASA's Lunar Reconnaissance Orbiter, now expected to launch in early 2009 after a recent delay.