Chace chases Carbon Dioxide

       We have done it again. Almost a year ago came the news that India's maiden moon mission, Chandrayaan-1, had traced water vapour close to the moon.

      And now a year later this mission has scored another triumph. A recent report published in the British space journal, ``Planetary and Space Science,'' says that Chandrayaan-1 has discovered carbon dioxide in the moon. This was done through one of the three scientific instruments on board the indigenous Moon Impact Probe (MIP) called Chace, short for Chandra's Altitudunal Composition Explorer. MIP was one of the 11 payloads on board Chandrayaan.

     According to the report prepared by a team of Isro scientists led by R.Sridharan.Chace is a quadrupole mass analyser based instrument with its own inbuilt ion source. It states that Chace was switched on 20 minutes before the release of MIP from 40 degrees north latitude at an orbital altitude of 98 km.

     Chace was operated twice during the mission, once for a short duration of 10 minutes in a rehearsal mode and the second time for 44 minutes. The report says: ``---it is believed that the C02 detected by Chace is of lunar origin only, which is the first direct (in situ) experimental confirmation of the prediction regarding the C02 dominance of the sunlit lunar atmosphere.''

     ``The significant amount of C02 and large enhancement of H20 in addition to the significant presence of the heavier species are considered very important results. The distinct possibility of the fragile lunar atmospheric system getting altered due to the impact of the past and present exploratory missions does exist and a systematic is called for addressing the issue,'' the report states.

     But, so typical of the Americans that some US scientists have challenged this discovery of carbon dioxide by Chace saying that a crucial instrument calibration data to clinch the discovery is missing from the Indian study.

     But Sridharan has countered the criticism saying that repeated calibration while the spacecraft was in orbit would have required additional power and more complex circuitry.    

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