It might not be quite as exciting as life on Mars, but water on the moon is surely the next best thing. Nasa scientists yesterday announced that a probe that was deliberately crashed into the moon's southern polar region last month discovered at least 25 gallons of water.
"Yes, we found water," said Anthony Colaprete, a principal project investigator at Nasa's Ames research centre in California. "We didn't find just a little bit, we found a significant amount."
Scientists hailed the discovery as a success and finding water is a huge boost for future missions. Most believe the likeliest places for water are at the poles of the moon, where there are craters in permanent shadow.
Scientists hope future study of the probe's findings could shed light on the evolution of the solar system, in the same way as an ice core sample taken from deep beneath the earth's surface reveals data on ancient geological events.
The discovery of water is a result of preliminary analysis of data from the lunar crater observation and sensing satellite (Lcross). The probe and an accompanying rocket, Centaur, were deliberately crashed into the Cabeus crater near the moon's south pole and scientists have been studying the resulting plume of lunar dust for the past few weeks.
"We're unlocking the mysteries of our nearest neighbour and by extension the solar system. It turns out the moon harbours many secrets, and Lcross has added a new layer to our understanding," said Michael Wargo, chief lunar scientist at Nasa's headquarters in Washington.
Lcross's spectrometer instrument examined light absorbed by the dust particles to determine their composition and discovered a chemical compound emitted when sunlight breaks up water molecules. The probe discovered an estimated 25 gallons of water, Colaprete said.
"We are ecstatic," said Colaprete. "Multiple lines of evidence show water was present in both the high-angle vapour plume and the ejecta curtain created by the Lcross Centaur impact. The concentration and distribution of water and other substances requires further analysis, but it is safe to say Cabeus holds water."
But Robert Park, a physicist at the University of Maryland and prominent sceptic of manned space flight, said the discovery means "practically nothing" to future hopes of a base or colony on the lunar surface.
"They've haven't found a big reservoir of it," he said. "I suspect this is just water clinging to the soil particles. It's of almost no value at all. The amount of machinery you'd have to move up there to try to recover it – you'd have to do a lot before you could pay for the cost of that."
The Lcross and Centaur spacecraft launched in June and travelled nearly 5.6m miles before separating on the final approach to the moon. Nasa heavily promoted the mission, which occurred during celebrations of the 40th anniversary of the Apollo moon landing.
On 9 October as the craft neared the moon, Americans gathered on lawns and in parks overnight, awaiting a fireworks display. They were disappointed when the impact was invisible to the naked eye about 250,000 miles away.
The Nasa mission confirmed a previous discovery announced in September by an Indian space mission, Chandrayaan-1, which found small amounts of water in the lunar soil.
An artist's rendering of the probe approaching the Moon
"The argument that the moon is a dry, desolate place no longer holds water," says a press release from NASA. A Moon mission launched by the agency has confirmed the presence of water on the moon. The discovery comes a year after a NASA instrument on an Indian lander indicated there were water molecules on the surface of our satellite.

On September 24, 2008 the Indian Space Research Organisation had stated Chandrayaan-1 had discovered water based on readings from NASA's Moon Mineralogy Mapper, one of eleven instruments carried by the probe. Those results indicated water was widespread in low quantities. That probe, launched in October 2008, had to be abandoned on August 30 when contact was lost with it on the Moon's surface.

The new mission, called LCROSS, consisted of two separate spacecraft which travelled the 250,000 miles together in June before separating. An empty rocket slammed into the Cabeus crater, near the southern pole, while a small spacecraft stayed behind to take measurements from the plume of debris thrown up, although it too ultimately crashed into Cabeus. Across the United States people spent the night on lawns and in parks hoping to see the impact, on the 40th anniversary of the first Apollo Moon landing, but it was invisible to the naked eye. NASA had predicted a visible six-mile plume; the reality was only a mile high.

The twin impacts on October 9 are now known to have sent 25 gallons of water ice and vapour into the air amongst the debris kicked up from the 60 to 100 foot wide hole produced by the rocket. This amount only accounts for the debris scientists could actually see over the rim, and the remaining debris could contain more water. It is unclear how much water may be distributed accross the Moon, although hydrogen at the poles suggests water ice there. 

LCROSS stands for lunar crater observation and sensing satellite, which was the satellite's name, while its rocket companion was called Centaur. It took a month to analyse the spectrometer data from the mission, and efforts are ongoing to determine the composition of the remaining material kicked up out the crater. The whole project cost $75 million.

"We got more than just whiff. We practically tasted it with the impact," said project co-investigator Peter H Schultz. The material thrown up split into a curtain travelling sideways and a plume that passed the crater's rim, bringing it into the sunlight for the first time in billions of years. Both contained water. "We are ecstatic," said project leader Anthony Colaprete.
"We didn't find just a little bit, we found a significant amount."

Michael Wargo, who heads up lunar research for NASA, said "We're unlocking the mysteries of our nearest neighbour and by extension the solar system. It turns out the moon harbours many secrets, and LCROSS has added a new layer to our understanding." It is thought that by analysing the water we can learn of the moon's history, in a fashion similar to investigating Earth history with ice cores.

University of Maryland physicist Robert Park cautioned that people should not assume that water on the lunar surface would support a colony. "They've haven't found a big reservoir of it," he said. "I suspect this is just water clinging to the soil particles."

Buzz Aldrin, one of the first to walk on the Moon when he followed pioneer Neil Armstrong out of Apollo 11, said he was pleased by the news but added that "People will overreact to this news and say, 'Let's have a water rush to the moon.' It doesn't justify that." Aldrin wants the US to aim to colonise Mars, but NASA is looking at more lunar trips. Last month a new rocket was tested, and Barack Obama has set up a panel to look at possible Moon missions. George W. Bush had previously proposed a $100 billion programme to put more astronauts onto the Moon. NASA wants to return by 2020 and build a lunar base, allowing astronauts to remain for months at a time.