Nasa's experiment last month to find water on the Moon was a major success, US scientists have announced.

美国科学家宣布，美国航空航天局上个月寻找月球上的水源的实验取得重大胜利。

plume¹ about 20 seconds after impact" width="466" height="280" src="/upimg/091114/4_012456_1.jpg" />
A camera on the probe shows the ejecta plume about 20 seconds after impact

The space agency smashed a rocket and a probe into a large crater²（弹坑，火山口） at the lunar south pole, hoping to kick up（引起，激起） ice.

Scientists who have studied the data now say instruments trained on the impact plume saw copious³（丰富的） quantities of water-ice and water vapour（水蒸气）.

One researcher described this as the equivalent of（相当于） "a dozen two-gallon buckets（水桶）" of water.

"We didn't just find a little bit; we found a significant amount," said Anthony Colaprete, chief scientist for the Lunar Crater Observation and Sensing Satellite (LCROSS) mission.

No doubt

October's experiment involved driving a 2,200kg Centaur⁴ rocket stage into the 100km-wide Cabeus Crater, a permanently⁵ shadowed depression（沮丧，萧条） at the Moon's far south.

At the time, scientists were hoping for a big plume of debris⁶ some 10km high which could be seen by Earth telescopes.

The actual debris cloud was much smaller, about 1.6km high, but sufficiently⁷ large to betray the evidence researchers were seeking.

The near-infrared spectrometer（红外线分光计） on the LCROSS probe that followed the rocket into the crater detected water-ice and water vapour. The ultraviolet-visible spectrometer provided additional confirmation⁸ by identifying the hydroxyl（氢氧根） (OH) molecule⁹, which arises when water is broken apart in sunlight.

"We were able to match the spectra¹⁰（光谱，领域） from LCROSS data only when we inserted the spectra for water," Dr Colaprete said.

"No other reasonable combination of other compounds that we tried matched the observations. The possibility of contamination from the Centaur also was ruled out."

Useful resource

The total quantity of H2O spied by the instruments was more than 100kg. It came out of a 20m-30m wide hole dug up by the impacting Centaur rocket.

The LCROSS scientists stressed that the results presented on Friday were preliminary findings only, and further analysis could raise the final assessment¹¹ of the amount of water in Cabeus.

Peter Schultz, from Brown University and a co-investigator on the LCROSS mission, said: "What's really exciting is we've only hit one spot. It's kind of like when you're drilling for oil. Once you find it in one place, there's a greater chance you'll find more nearby."

The regular surface of the Moon as seen from Earth is drier than any desert on our planet. But researchers have long speculated（沉思，推测） that some permanently shadowed places might harbour considerable stores of water, perhaps delivered by impacting comets billions of years ago.

If future investigations¹² find the quantities to be particularly large, this water could become a useful resource for any astronauts who might base themselves at the lunar poles.

"It can be used for drinking water," said Mike Wargo, Nasa's chief lunar scientist for exploration systems.

"You can break it down and have breathable air for crews. But also, if you have significant quantities of this stuff, you have the constituents¹³（成分） of one of the most potent¹⁴（强有力的） rocket fuels - oxygen and hydrogen."