Moon may have had water since formation

WASHINGTON – One of the biggest lunar discoveries of the decade – proof that the moon may have had water since its formation – was announced Wednesday by a team of researchers whose background is more in Earth science than moon rocks.

In an article published in the journal Nature, the six-scientist team of geologists and geochemists showed that water from the moon’s interior gushed to the surface more than 3 billion years ago in geyser-like jets of molten magma, disproving a long-standing belief that Earth’s nearest neighbor is almost bone-dry.

The source of their discovery: two one-gram samples of moon rocks brought back to Earth more than 35 years ago by the Apollo 15 and Apollo 17 lunar missions.

“It’s a real step forward, and it shows we’re still getting things out of the Apollo samples,” said NASA’s David Lindstrom, a program officer and a lunar scientist since Apollo 11.

How did they find water?

Alberto Saal, a geochemist at Brown University and the study’s lead author, went to Erik Hauri, a college friend and geochemist at the Carnegie Institution for Science, who had helped improve a technique called secondary ion mass spectrometry. The machine blasted the moon rocks with ionized beams and measured resulting changes in the beam’s electrical charge. It can detect water at levels as low as five parts per million.

When the moon rocks yielded up to 46 parts per million, the scientists knew they had made a big discovery.

Where did it come from?

That’s not entirely clear. The researchers think that water vapor was part of volcanic eruptions from the moon’s core that quickly solidified on its icy surface.

Their discovery suggests that water may have been part of the moon since its formation about 4.5 billion years ago, when a planet-sized object smashed into Earth and the resulting space debris coalesced as the moon. Water may have been part of the material that came either from the Earth or from the object that hit it.

Another possibility is that the moon was bombarded by water-rich comets and meteorites soon after it formed.

“It really changes the rules of the game as to what we’re assuming about the moon,” said Robin Canup, a Colorado-based researcher at the Southwest Research Institute and a leading lunar history expert.

What’s next?

The team now plans to study rocks from other Apollo missions. And NASA is scheduled to launch a Lunar Reconnaissance Orbiter as early as November to, among other things, investigate surface ice first detected by NASA probes in the 1990s. But that ice is thought to have been carried to the moon by comets or meteors.