Humankind has long been fascinated by the moon. With the dawn of the space age, scientists were in a position to try and wrest secrets that our celestial neighbour might hold. Although the space race between the United States and the Soviet Union was primarily about demonstrating their strategic superiority, the samples of lunar rock and soil brought back by American astronauts and subsequently by the Soviet unmanned spacecraft were invaluable. Scientists had conjectured that the moon might hold water. But the lunar samples, when analysed on earth, suggested otherwise. However, two U.S. spacecraft that travelled to the moon in the 1990s found indications that water in the form of ice lay trapped in the icy cold depths of permanently shadowed lunar craters. These findings were contested and it was India's Chandrayaan-1, the country's first space probe launched two years ago, that finally provided a persuasive case for water on the moon. The matter has now been decisively settled by the U.S. Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite. The latter mission sent a spent rocket upper stage crashing into a crater on the moon's South Pole a year ago, while a spacecraft that came right behind made observations of the debris that was thrown up. In papers that have just been published in the journal Science, scientists involved in the mission say that the plume of debris contained as much as five per cent of its weight, possibly more, in the form of water-ice. A number of other molecules and elements were also detected in the dust kicked up by the crash.

Water is a valuable resource that can help sustain any future lunar base. The hope is that water extracted from the moon can be used for human consumption and possibly as a source of rocket fuel. The last humans who walked on the moon returned home almost 40 years ago and many more years could pass before humans go back again. The current U.S. Administration has cancelled much of the Constellation programme, which aimed to send humans again by 2020. China, on the other hand, is embarking on an ambitious programme of lunar exploration. Its second lunar probe, the Chang'e-2, has begun orbiting the moon. This spacecraft will set the stage for a mission to land a robotic rover in 2013. The country also plans to send an automated sample-return mission four years later. China, which has successfully sent six astronauts into space, could attempt a manned moon landing in 2025, according to one of its senior space scientists. India, for its part, intends to launch the Chandrayaan-2 mission in 2013; it will have an orbiter studying the moon from space while a Russian-built lander puts a rover on the ground below. Thus humanity's quest to understand the moon goes on.