Moon has more water than Great Lakes, Chandrayaan data shows

WASHINGTON - Scientists have found Moon’s minerals may have at least 100 times more water than previously indicated by remote sensing data from the Indian spacecraft Chandrayaan-1 and other lunar sample analysis.

In March 2010, a US space agency NASA radar experiment aboard Chandrayaan-1, India’s first lunar spacecraft launched by the Indian Space Research Organisation in October 2008, found thick deposits of water-ice near the Moon’s north pole.

Scientists at the Carnegie Institution’s Geophysical Laboratory in Washington now estimate that the volume of water molecules locked inside minerals in the Moon’s interior could exceed the amount of water in the Great Lakes on the US-Canada border that hold 20 percent of the Earth’s surface fresh water.

New NASA-funded research determined that the water was likely present very early in the Moon’s formation history as hot magma started to cool and crystallise, the agency said Monday asserting “This finding means water is native to the Moon.”

“For over 40 years we thought the Moon was dry,” said Francis McCubbin of Carnegie and lead author of the report published in Proceedings of the National Academy of Sciences.

“In our study we looked at hydroxyl, a compound with an oxygen atom bound with hydrogen, and apatite, a water-bearing mineral in the assemblage of minerals we examined in two Apollo samples and a lunar meteorite.”

McCubbin’s team utilised tests which detect elements in the parts per billion range. Combining their measurements with models that characterize how the material crystallized as the Moon cooled during formation, they found that the minimum water content ranged from 64 parts per billion to 5 parts per million.

The result is at least two orders of magnitude greater than previous results from lunar samples that estimated water content of the Moon to be less than 1 part per billion.

“In this case, when we talk about water on the Moon, we mean water in the structural form hydroxyl,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. “This is a very minor component of the rocks that make up the lunar interior.”

The origin of the Moon is now commonly believed to be the result of a Mars-size object that impacted the Earth 4.5 billion years ago. This impact put a large amount of material into Earth’s orbit that ultimately compacted to form the Moon.

The lunar magma ocean that is thought to have formed at some point during the compacting process, began to cool. During this cooling, water either escaped or was preserved as hydroxyl molecules in the crystallising minerals.

The identification of water from multiple types of lunar rocks that display a range of incompatible trace element signatures indicates that water may be at low concentrations but ubiquitous within the Moon’s interior, potentially as early as the time of lunar formation and magma ocean crystallisation, scientists said.

(Arun Kumar can be contacted at arun.kumar@ians.in)