The Chandrayaan-1 probe had found traces of water across the surface of large parts of the moon, challenging the long-held view that the earth’s natural satellite is bone dry.
The spacecraft also found indications that water is being produced in the lunar soil through interactions with charged particles streaming out from the sun.
This major discovery is a vindication of the Chandryaan-1 mission, which encountered many problems and finally ended abruptly last month.
The Moon Mineralogy Mapper (M3), a U.S.-supplied instrument that flew on the Chandrayaan-1, examined the intensity of different colours of sunlight bouncing off the lunar surface.
In a paper being published online this week by Science, American and Indian scientists report that the instrument found a distinctive signature of water and hydroxyl emanating from the moon. (A water molecule is made up of one oxygen atom linked to two hydrogen atoms, while hydroxyl has the oxygen atom attached to just one hydrogen atom.)
The M3 discovered the signature of water and hydroxyl on the surface soil and rocks at many diverse places in sunlit regions of the moon. The signature was stronger at the higher latitudes. Two U.S. space missions, Cassini and the Deep Impact spacecraft, have provided supporting evidence.
“We’ve made a very important step with this discovery,” said Carle Pieters of Brown University in the U.S., principal investigator for the M3. But “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,” she cautioned in a press release issued by the university.
What was detected was water molecules present in extremely minute quantities on the surface soil and rocks, noted J.N. Goswami, director of the Physical Research Laboratory in Ahmedabad and principal scientist for the Chandrayaan-1. He estimated that less than a teaspoon of water could be squeezed out from several kg of lunar soil.
The widespread distribution of water seen by M3 was “a complete surprise,” said Lawrence Taylor of the University of Tennessee in the U.S., one of the authors of the paper. Scientists have begun finding signs of water in some lunar minerals, he told this correspondent.