The discovery of water on moon was till recently attributed to NASA’s Moon Mineralogy Mapper, M3 on board India’s Chandrayan space craft. It was claimed that the  instrument detected water on moon’s polar region on 14 November 2008 while the space craft was rotating the earth’s natural satellite in a 100 kilo meter circular orbit. In an important development that wrong was set right on February 12, 2011 when the American Astronomical Society announced that the NASA’s Hubble Space Telescope (HST) had confirmed the discovery of water on moon by the Indian built Moon Impact Probe (MIP) on board Chandrayan. The MIP, a 34 kg box shaped object carried the Chandra Altitudinal Composition Explorer, CHANCE which had three devices,  a video imaging instrument, a radar altimeter and a mass spectrometer. While the video imaging instrument was for taking pictures of the moon’s surface as MIP approached it, the radar altimeter was for measuring the rate of descent of the probe to the lunar surface. The mass spectrometer was for studying the extremely thin lunar atmosphere. It took the MIP 25 minutes after it was detached from the orbiting space craft to reach the moon’s surface. During that time before hard landing on moon’s surface, the MIP radioed all the information to Chandrayan which it instantly recorded in its onboard memory for reading out later. With the MIP’s sending of information to Chandrayan, India’s very first attempt to send a lunar probe was successfully concluded.

            When the news that the NASA had confirmed the MIP’s discovery of water on moon broke out, there was jubilation in ISRO’s Vikram Sarabhai Space Centre where CHANCE was developed. The manager of CHACE project, Syed Maqbool Ahmed reacted to the development saying "This is the first time scientists from the west have acknowledged the published work of direct evidence of water on the moon by India." Tirtha Pratim Das, a scientist who worked for CHACE project wrote in Vikram Sarabhai Space Centre’s internal journal 'Voyage', "The experiment on board the Moon Impact Probe made the first successful measurement on the lunar day-side atmosphere on 14th November, 2008." According to him the analysis of the data revealed the presence of water in a significant amount on the moon. The credit of discovery of water on moon, however, does not go to Chndrayan’s MIP alone. Two other probes of the NASA also found water on moon. Visual & Infrared Mapping Spectrometer on board Cassini spacecraft launched in 1999 found water molecules at different places on the sunlit portion of moon’s surface. High Resolution Infrared Imaging Spectrometer on Epoxi space craft while flying past moon in June last year also found water and Hydroxyl molecules on the moon’s polar region. The results of these explorations, however, remained unpublished till recently.

Finding water on the surface of moon and particularly, in more quantities than predicted before is certainly a great thing.  But, exactly how abundant is the water on moon? Dr  Roger Clark of US Geological Survey in Denver gave a precise idea about it. He said, “If you harvested one ton of moon’s top layer soil, you could get as much as 32 ounces of water.” Talking in general terms, the principal investigator of NASA’s Moon Minerology Mapper, M3 project, Dr Carle Pieters says, “When we say water on moon we are not talking about lakes, oceans or puddles. Water on moon means molecules of water and Hydroxyl that interact with rock and dust on moon’s surface.” Another NASA scientist Paul Spudis has, however, said that the Chandrayaan’s radar data has revealed the presence of bulk water ice frozen in the shadowed craters near the Moon's north pole, in the amount of at least 600 million metric tonnes. He said, data from the Moon Minerology Mapper instrument aboard Chandrayaan had detected a thin but widespread presence of surface-adsorbed water in the lunar regolith, in the form of a hydroxyl-bond signature.

One may recall that Chandrayaan was successfully launched by ISRO’s PSLV-C11 rocket on October 22, 2008 from Satish Dhawan Space Centre at Sriharikota into its intended elliptical orbit around Earth. From the Earth’s elliptical orbit, the space craft entered into its planned lunar orbit on November 8, 2008. Then its orbital height was reduced in steps to its intended operational altitude of 100 km from the lunar surface. Since its launch, the health of Chandrayaan was being continuously monitored from the Spacecraft Control Centre of ISRO’s Telemetry, Tracking and Command Network (ISTRAC) at Bangalore. The space craft had a planned life time of two years. However, about ten months from its launch date, it suddenly lost radio contact on August 29, 2009. This was a set back for ISRO, but, the loss should not be exaggerated. In fact, compared to the space agencies of other space faring nations, the ISRO’s record is much better It needs to be mentioned here that during its ten month long existence Chandrayan completed 95 % of its objectives. It completed nearly 3400 revolutions during which it sent more than 70,000 images of moon.