Why are we asking this now?
The American space agency Nasa announced yesterday that three separate missions examining the Moon have found clear evidence of water there. The discovery has huge implications not only for science, but geopolitics as well.
Water, as on Earth? Water you could float a boat in?
No. We are not talking oceans here, or rivers, or lakes or even puddles. What researchers claim to have found are molecules of water and hydroxyl (hydrogen and oxygen) that interact with molecules of rock and dust in the top millimetres of the Moon's surface – in essence, water-bearing minerals, rather than water that is in any way free flowing. But water is water. And water is the essential element for life on earth.
Might it have more than just scientific interest?
Forty years after Neil Armstrong and Buzz Aldrin became the first men to walk on the lunar surface, we seem to be reaching a new turning point in space and, specifically, lunar exploration. The pace is being set in Asia, mainly by the Chinese, who since 2003 have been putting their own astronauts into orbit and are now actively developing a lunar lander.
But they are being followed by their rivals, the Indians, and it is a cause of immense national pride in India that one of the instruments which picked up the water traces, Nasa's Moon Mineralogy Mapper, was being carried on board an Indian lunar orbiter, the Chandrayaan-1; this will be seen as a significant boost to India in its space competition with the Chinese. Yet these two nations are not alone; the Japanese successfully sent up their own lunar orbiter two years ago.
We may scarcely have noticed it, but these Asian economic giants are now determinedly set on lunar exploration, whether the West is interested in it or not, and sooner or later, one of them is going to send astronauts back once more to our nearest neighbour in space.
Where does that leave the Americans?
In something of a quandary. America's dispatch of humans to the Moon was history's most stunning technological success, sparking endless dreams of deep-space exploration, yet only three years after Armstrong and Aldrin's initial voyage in Apollo 11, the Apollo programme was brought to an end. There were six lunar landings and twelve men walked on the Moon's surface and were brought successfully home, but after Apollo 17 returned in December 1972 there were no more missions. Instead, the US developed the Space Shuttle and restricted its space programme to Earth orbits.
Why was Apollo cancelled?
The cost was enormous and increasingly questioned within the USA; it was thought that the billions of dollars involved might be better spent on domestic problems. Furthermore, the original impetus to go to the Moon had disappeared.
It had been a product of the military rivalry of the Cold War with Russia, and of the initial space race. The Russians seemed to have establish a clear lead, and potentially a political advantage, when they sent up the first artificial satellite, Sputnik-1, in 1957, and the first man into earth orbit, Yuri Gagarin, in 1961.
As a result of this President John F Kennedy vowed to put an American on the Moon by 1970. But once this had been done, it was clear that the Russians were not going to follow suit, and so the space race was over; the Cold War began to thaw.
It might also be said that in the 1970s America's national self-confidence had began to crumble, with the nation bitterly divided over the Vietnam War; the space programme also divided opinion.
What's the US position regarding the Moon now?
In 2004, George W Bush decided America would return to the Moon by 2020. As a presidential candidate, Barack Obama endorsed that decision in principle, but he has delayed taking a formal decision to go ahead with the plan.
Instead, he set up a commission under Norman Augustine, the former head of the giant aerospace company Lockheed Martin, to study America's space options and report back to him. The Augustine commission's preliminary report appeared on September 9 and in some quarters this was seen as the death-knell for the idea of returning to the Moon, not least because the first sentence announced: "The US human spaceflight programme appears to be on an unsustainable trajectory."
But, as you might expect with issues surrounding space travel, the position was more complicated than that. The commission was saying that Nasa could not put a man on the Moon again within the Bush timescale and with the budget it had; that does not mean that the timescale, or the budget, could not be changed, and these are essentially political decisions for President Obama. He will make them after the commission's full report is presented to him shortly.
But it seems reasonable to assume that yesterday's announcement about lunar water will have relevance. Do we really think the timing is a coincidence – of a Nasa announcement about lunar water which implies that establishing a Moon base might be more feasible than we thought in the past?
Does it really imply that?
It would seem to. According to Britain's leading spaceflight expert, Professor Colin Pillinger of the Open University – the scientist who led Europe's ultimately unsuccessful mission to Mars, the Beagle 2 project in 2003 – a significant supply of water on the Moon, in whatever form it is found in, opens up enormous possibilities for a lunar base and for further exploration starting from the Moon itself.
Water can be converted into spacecraft fuel, Professor Pillinger says, either as hydrogen or oxygen, which would eliminate the need to transport vast amounts of fuel from earth; it might even be used for growing vegetables.
However, the difficulty, he points out, is that converting water found chemically bound up in minerals – as it seems to exist – into water as we know it, would require a great deal of energy on the Moon (it would be done by heating). "You would need to heat up a lot of lunar soil to 200C to get yourself a glass of water," he said. But even if the conversion is technically difficult, the presence of water on the Moon will have another effect.
India's involvement in the discovery will spur on the Asian version of the space race; it will make the Chinese intensify their efforts to get to the Moon first.
And this is the point. At the moment the US in general, and Barack Obama in particular, may feel that the costs of returning to the Moon are simply excessive. But what if the Chinese – or the Indians, or anyone else – goes ahead with an attempt to establish the first true lunar base? Will the US, the nation which planted its flag there, really stand by and let that happen without becoming involved itself? We shall see.
Does the discovery of Moon water make a new space race more likely?
* It means there is certainly a potential source of fuel in-situ on the surface of the Moon
* The fact that India played a part in the discovery will most likely intensify the Asian space race
* The US won't just idly stand by and let other countries go back to the Moon first
* Extracting water from minerals on the moon itself would be technically hard to do
* The presence of water doesn't lessen the difficulty of getting to the Moon in the first place
* For the US at least, the expense of a new manned lunar programme may be too great