Water molecules and hydroxyl previously were suspected in data from a Cassini flyby of the moon in 1999, but the findings were not published until now.

'The data from Cassini's VIMS instrument and M3 closely agree,' said Roger Clark, a US Geological Survey scientist in Denver and member of both the VIMS and M3 teams.

'We see both water and hydroxyl. While the abundances are not precisely known, as much as 1,000 water molecule parts-per-million could be in the lunar soil.

To put that into perspective, if you harvested one ton of the top layer of the moon's surface, you could get as much as 32 ounces of water.'

For additional confirmation, scientists turned to the Epoxi mission while it was flying past the moon in June 2009 on its way to a November 2010 encounter with comet Hartley 2. The spacecraft not only confirmed the VIMS and M3 findings, but also expanded on them.

'With our extended spectral range and views over the north pole, we were able to explore the distribution of both water and hydroxyl as a function of temperature, latitude, composition, and time of day,' said Jessica Sunshine of the University of Maryland.

Sunshine is Epoxi's deputy principal investigator and a scientist on the M3 team. 'Our analysis unequivocally confirms the presence of these molecules on the moon's surface and reveals that the entire surface appears to be hydrated during at least some portion of the lunar day.'

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