Measuring methane and its isotopes 12CH4, 13CH4, and CH3D on the surface of Mars with in situ laser spectroscopy

In light of the recent discovery of methane on Mars and its possible biological origin, a strategy is described for making in situ measurements of methane and its isotopes on the surface of Mars by laser spectroscopy in the 3.3-mum wavelength region. An instrument of reasonable mass (similar to1 lb) and power (few watts) is capable of measuring mixing ratios down to 0.1 part per 109 by volume, a hundred times lower than recently reported observations. Making accurate measurements of (CH4)-C-13 and CH3D will be more difficult. For measuring delta(13)C to 10parts per thousand and deltaD to 50parts per thousand, sample preconcentration will be required to similar to3 parts per 10(6) by volume for delta(13)C and to similar to40 parts per 10(6) by volume for deltaD. This need would be mitigated by the discovery of larger local abundances of methane near the source regions. (C) 2005 Optical Society of America.