Moon has much more water than previously thought

The moon has much more water than was believed in the past. Most of the water is underground, in molecular form and actually came from the earth more than 4 billion years ago.

Earth’s only natural satellite was believed to be bone-dry before India's Chandrayaan-1 stunned the world when one of its on-board instruments found the “elixir of life” on an otherwise barren and craggy land 3.8 lakh km from the earth. The water was not like what is seen on earth, but a thin film of molecules known as hydroxyl.

Analysing data collected by the same instrument, the Moon Minerology Mapper (M3), a team of US scientists have now found large quantities of underground water in the same hydroxyl form. “It came from earth about 4.6 billion years ago, when the moon was formed,” team leader Rachel Klima from Johns Hopkins University told Deccan Herald.

The most accepted theory about the moon's formation says it was formed due to a giant impact between a Mars-sized object with the earth. The collision released a large quantity of materials into orbit, which then accreted to form the moon. Water was among those materials. “Many assumed that volatile elements and water would be vaporised and lost into space during the formation.

However, our data, as well as that obtained by researchers studying the samples returned by the Apollo missions, suggest that a lot of this original water was not lost, and that it instead was incorporated into the early moon,” said Klima. The findings were published in a recent issue of Nature Geoscience.

The discovery represents a new contribution to the rapidly-changing understanding of lunar water. The molecular water or hydroxyl is bonded to the rocks and is likely to be as old as the moon.

About five years ago, new laboratory techniques revealed that the interior of the moon was not as dry as was previously thought. Around the same time, data from orbital spacecraft like Chandrayaan detected hydroxyl films on the lunar surface, which is thought to be a thin layer formed from solar winds hitting the lunar surface.

“This surficial water unfortunately did not give us any information about the underground water that exists deeper within the lunar crust and mantle,” said co-author Justin Hagerty of the US Geological Survey. Lunar water has a volcanic past, because of which it may have evaporated from most of the sites.

“But at the Bullialdus crater and other places on the moon, some of the magmas that rose towards the surface got stuck in the lower crust, trapping the water within them as they cooled,” said Klima.