Untold riches

The Apollo astronauts landed on the moon in 1969, and left a message saying that they had come in peace for all mankind. In 1998, a US robot spaceprobe called Lunar Prospector cruised over the moon's south pole and signalled what could become the first off-planet land grab. The probe had discovered, deep in a shaded crater, something worth more than gold. It had detected hundreds of millions of tons of water, splashed there aeons ago by a comet.

Water splits into hydrogen and oxygen: it can become both rocket fuel and the breath of life. With water onstream in what was once considered a dead and hopeless place, a moonbase suddenly became possible. With a gravitational tug just one sixth of the Earth's, the moon could serve as a springboard and a kind of petrol station for much greater journeys into space. With a lunar day that lasts 14 Earth days, there could be uninterrupted sunlight as an energy source to power mining operations.

Japanese engineers dream of mining the moon for yet more power. The moon has supplies of an element almost unknown on Earth called helium-3, which could serve as fuel for fusion reactors. The He-3 is locked up with vast reserves of titanium, another mineral costly on earth. Robots could dig the titanium, and solar mirrors could heat the ore to 700C, to boil off the precious helium - along with vital supplies of oxygen, hydrogen, nitrogen and carbon dioxide.

There are dreams of a telescope on the dark side of the moon, to observe the universe as never before. There are plans to collect sunlight in orbiting power stations and beam either direct light or microwave energy down to Earth-based collecting points. There are dreams of capturing passing asteroids and dismantling them for ores. One Nasa engineer has calculated that one cubic kilometre of nickel-iron asteroid would yield seven billion tons of iron, a billion tons of nickel and enough cobalt to supply the entire world for 3,000 years.

But all of these plans depend on a solid base, a sure supply of water and a low-gravity environment to enable low-cost traffic into space and back - in a word, the moon.

Four years ago, a Nasa chief predicted: "If we see water, I suspect a land rush is on." The Chinese have designs for moon buggies rather than covered wagons, but the message is clear.

In 1979, the UN Outer Space Committee negotiated a treaty to make the moon a common resource for all mankind. Very few nations have signed it: some have conspicuously not signed it. The non-signatories include the United States, Russia, Japan and China.