View of the Moon seen Apollo 17

"If space is an ocean," says ESA's Franco Ongaro, "then the Moon is our nearest island." It is an island that last saw human visitors in December 1972, when the final Apollo mission came home from the Taurus-Littrow highlands. ESA's Aurora Programme might well see people back on lunar soil.

New data from 1990s space missions have made the Moon more attractive than in the Apollo days; there have been strong hints that water might exist in the permanent shadow of deep polar craters. As a resource, lunar water could cut the cost of living dramatically for lunar explorers, since otherwise supplies would have to come all the way from Earth - at a price of anything up to 20 000 Euros per litre. It would also make a lunar 'fuel factory' a real possibility. There is plenty of oxygen bound up in the Moon's rocks, but little or no hydrogen. Even a modest water supply could guarantee an in situ source of cheap rocket propellant.

False-colour composite photograph of the Moon

Lunar water has a strong scientific interest, too. Where does it come from? Cometary impacts are the most likely source. Since comets consist of material left over from the formation of the solar system 4.7 billion years ago, scientists are keen to get their hands on some samples. It would be far easier to pick them up from the lunar surface than to send a spacecraft hundreds of millions of kilometres to a comet rendezvous.

Not that a return to the Moon could really be described as 'easy'. For a start, Europe will have to develop its own soft-landing technologies for the preliminary robot missions. A polar lander would require remote units capable of exploring the sunless depths of likely water-bearing craters, so the project will need very advanced communications. Finally, we will have to test and develop the systems and spacecraft that will carry men and women to the Moon - and support them there.