Washington - Water is present on the surface of the moon, scientists said Thursday in a series of articles to be published in the journal Science. Separate analyses by scientists using data from India's Chandrayaan-1 satellite and two US spacecraft, Cassini and the Deep Impact probe, found evidence of water in the moon's soil and showed it was widespread across its entire surface.
"Widespread water has been detected on the surface of the moon," said Carle Pieters, lead scientist for the instrument used on the Indian spacecraft to make the finding. "This is not what any of us expected a decade ago."
The finding blows away accepted beliefs that water could not exist on the moon's surface, especially in very hot areas near the equator. In fact, trace amounts of water found in rocks brought back by the Apollo astronauts were dismissed as contamination once back on Earth.
A NASA instrument called the Moon Mineralogy Mapper on Chandrayaan used the data from light reflecting off the lunar surface to determine the make-up of the soil and found the water as well as hydroxyl. Hydroxyl is composed of one hydrogen and one oxygen atom, while the well-known composition of water is two hydrogen atoms to one oxygen atom.
When the initial data showed evidence of water, the scientists tried to dismiss it as water residue on the spacecraft that had been picked up on Earth, Pieters said.
"It's not possible, the moon doesn't do this," she said, but the Chandrayaan data were then compared with decade-old data from Cassini's 1999 fly-by and recent data from Deep Impact. "It's completely conclusive, there's no question what so ever," she said.
The Cassini data had never been examined to check for water on the moon, in part because it took years to calibrate its instruments to counteract the effects of Earth water on the spacecraft.
The moon's water is located within 2 millimetres of the surface, but the moon is still quite dry, amounting to about a litre of water for every ton of soil.
"Even the driest deserts in the Earth have more water than are at the poles and surfaces of the moon," NASA scientist Jim Green said.
Water is more widespread across the moon's surface than scientists had expected but appears to be concentrated nearer the poles.
The instrument's data will also give scientists a more complete image about what kinds of minerals make up the moon's soil.
The US space agency NASA is in the midst of another year-long look at the lunar surface to prepare the way for a planned return of humans to the moon. Last week, in their first findings, they said the element hydrogen - a key component of water - is more widespread than expected at the moon's south pole.
Thursday's announcement is seen as complementing the ongoing mission, which next month will crash a satellite into the moon to look for water further beneath the surface. Astronomers had hoped to determine whether water could be hidden in the shadowy craters of the moon near its poles, where a lack of sunlight would prevent ice from evaporating.
An earlier lunar satellite found high levels of hydrogen in the atmosphere near the poles, a hint that water could be present.
Also Thursday, another analysis found that water is also more widespread on Mars than previously thought.
Photos by NASA's Mars Reconnaissance Orbiter found ice closer to the planet's equator than previously thought, about halfway between the equator and the north pole. The ice was also much purer than expected, about 99 per cent water.
Water was first confirmed on Mars by the Phoenix lander last year.
