The Moon’s surface holds as much as a litre of water in every tonne of lunar soil, according to new research.

Observations taken independently by three different spacecraft, including India’s first lunar mission, have detected the chemical signature of both water and a closely related molecule called hydroxyl all over the Moon’s surface.

The Chandrayaan-1, Deep Impact and Cassini probes all found that infrared light was absorbed on the Moon at wavelengths consistent with the presence of water or hydroxyl — a similar molecule that has one hydrogen atom where water has two. Variations in the infrared signal suggest that both are present, scientists behind the discovery said.

The results, which are published in three papers in the journal Science, overturn a long-standing consensus that the Moon is completely dry. The data do not suggest, however, that there is much water there — or that any of it is liquid or even ice.

The water and hydroxyl molecules are instead bound up in minerals at the surface, which would still appear exceptionally dry by terrestrial standards.

“It is drier than any desert we have here,” said Jessica Sunshine, of the University of Maryland, who worked on both the Chandrayaan-1 and Deep Impact measurements. “It’s sort of just sticking on the surface.”

Carle Pieters, of Brown University, who led the Chandrayaan-1 observation team, said: “When we say ‘water on the moon’, we are not talking about lakes, oceans or even puddles. Water on the moon means molecules of water and hydroxyl that interact with molecules of rock and dust specifically in the top millimetres of the moon’s surface.”

It would take about 730 square metres of dirt to produce a single drink of water, she said.

Larry Taylor, of the University of Tennessee, who also worked on the Chandrayaan-1 data, said the trace quantities of water amounted to about a quart (about a litre) for every tonne of lunar soil.

Some of this lunar water may have reached the Moon on comets, but much of it may actually have been generated on the Moon itself by interactions between its silicate rocks and the solar wind — a stream of particles generated from the Sun that includes positively-charged hydrogen atoms.

As the Moon lacks an atmosphere and magnetic field like the Earth’s to protect it from the solar wind, its rocks are under constant bombardment. When these hydrogen atoms strike lunar rocks, they may be breaking chemical bonds and freeing oxygen atoms to combine with hydrogen to make water and hydroxyl.

The discovery has fanned dreams of establishing a manned Moon base.

Scientists have long hoped that astronauts could be based on the Moon and use water found there to drink, extract oxygen to breathe and use hydrogen as fuel.

Several studies have suggested that there could be ice in the craters around the Moon’s poles, but scientists have been unable to confirm the suspicions.

Big bang

• The Moon is 4.6 billion years old, about the same age as the Earth

• It is thought to have formed from a giant dust cloud caused when a rogue planet collided with the Earth

• It is 238,000 miles from the Earth

• Gravity on the Moon is a sixth of that on Earth

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