The need for light element stable isotopic ratios on Mars by INTERMARSNET

The mass available within the payload of INTERMARSNET provides scope for instruments which need not necessarily be part of the envisaged network but could exist as stand-alone entities on a single lander station. Model payloads include an evolved gas analyser which, depending upon oneʹs perception, may be considered capable of only relatively simple experiments where, for instance, a sample is heated with concomitant detection of the liberated gases. In a sense this approach realizes only a limited scientific return. In contrast, an EGA can be part of a very sophisticated instrument which would have the power to reproduce the levels of analytical performance obtained in laboratories on Earth. In this case the apparatus would include, in addition to facilities for heating samples, a gas management system whereby sample gases are separated, purified and quantified, several different gas chromatographic columns optimized for different separation purposes, and a mass spectrometer capable of detecting gases and measuring their stable isotopic compositions. The technical goals include measurement of the following isotope ratios: DH (2H1H). 13C12C, 15N14N, 17O16O, 18O16O, possibly 34S32S and certain key noble gas isotope ratios (i.e. Ne, Ar and Xe). Given that light element stable isotopes are an important route to the understanding of the martian surface and atmosphere, giving information about current and past climate, it would be highly appropriate to have such an experiment determine precise differential compositions (δ values for C, N, O and H) as part of the mission. Existing knowledge about the isotopic composition of Mars from previous space activities (Viking), telescopic observations and the SNC meteorites (assuming these to be martian) is discussed herein noting deficiencies in our coverage and making suggestions for additional work. Ideas are presented for determining precise values for key systems involving carbon, nitrogen, oxygen and hydrogen employing the “Modulus” philosophy, which was developed for the international Rosetta Cometary mission. Scientifically the ambitions of such a project would be to understand the past and present geochemistry of the light elements at the martian surface. Since the elements of interest are implicated in the development of environmental conditions, results would be placed within the context of atmospheric evolution, volatile cycling, surface weathering and martian exobiology.