Traces of water on moon

A new analysis of volcanic glass recovered from the moon decades ago found the rocks contain traces of the constituents of water, challenging a long-held notion that the moon is dry.

Using a technique not available when Apollo astronauts collected the rocks in the early 1970s, scientists detected telltale signs of water trapped inside the pebblelike glass. Their discovery suggests water was present deep within the moon between 3.3 billion and 3.6 billion years ago, when the pebbles were formed during lunar eruptions.

The report, in the new issue of the journal Nature, may cause scientists to rethink theories on how the moon was formed.

"The water that these guys have discovered is a scientific gold mine for us to figure out the history of ... the moon," said Jim Garvin, chief scientist at NASA's Goddard Space Flight Center, who was not involved in the research.

The pebbles, about the size of a period on this page, are made of magnesium-rich green volcanic glass and iron-rich orange glass that solidified moments after eruption. They were recovered from the moon's equatorial region during the Apollo 15 and Apollo 17 space missions.

Earlier studies of the rocks detected sulfur and carbon within the pebbles, indicating the glass was formed in a fiery eruption.

For the latest study, scientists measured the composition of the rocks molecule by molecule, using a technique 10 times more sensitive than that used in previous work.

They didn't search for water directly because when water is incorporated into the rocks, it naturally separates into smaller components. So researchers looked for one of those components, hydrogen, which would signal the presence of water.

Testing the interior of the rocks to avoid any surface contamination, scientists found trace amounts of hydrogen along with chlorine and fluorine, which, like carbon and sulfur, are found in rocks from explosive eruptions. The discovery of hydrogen alongside the other compounds suggested to scientists that the water came from inside the moon and not from an external source, such as a comet.

Based on the amount of hydrogen found in the pebbles, scientists estimate the lunar magma contained 260 to 745 parts per million of water, similar to what is found in the Earth's upper mantle.

"Up until our study, there was really no evidence for [indigenous] water on the moon," said Erik Hauri, a scientist at the Carnegie Institution for Science and author on the paper.

What's next?

The researchers plan to study rocks from other Apollo missions, and NASA is scheduled to launch a Lunar Reconnaissance Orbiter this year 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.

Material from The Orlando Sentinel is included in this report.