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Paloma : an instrument to measure the molecular, elemental and isotopic composition of the mars atmosphere from a landed platform (MSL 09, EXOMARS).


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EGS-AGU-EUG Joint Assembly, 6-11/04 2003, Nice (France).

Type de document > *Congrès/colloque

Mots clés > études environnementales radon, radon

Unité de recherche > IRSN/DSU/SERAC

Auteurs > SABROUX Jean-Christophe

Date de publication > 06/04/2003

Résumé

An instrument to analyze the molecular, elemental and isotopic composition of Mars atmosphere from a landed platform is being developed under CNES funding. This instrument, called PALOMA (PAyload for Local Observation of Mars Atmosphere), will be proposed in response to the AO for the instrumentation of the NASA Mars Smart Lander mission, planned to be launched in 2009. It might be part as well of the EXOMARS mission presently studied at ESA in the frame of the Aurora program. Noble gases (He, Ne, Ar, Xr, Xe) and stable isotopes (C, H, O, N) will be analyzed by using a system of gas purification and separation, coupled with a mass spectrometer. The heaviest, radioactive, noble gas (Rn) and its short-lived daughters will be measured using a small additional device (alpha particle detector). Detailed search for trace constituents of astrobiological interest, like CH4, H2CO, N2O, H2S (abundances, isotopic ratios, time variability) will be done on a regular temporal basis during one Martian year. Isotopic ratios will be measured with an accuracy of about 1‰, or better, in order to provide a clear diagnosis of possible life signatures, to allow a detailed comparison of Earth and Mars atmospheric fractionation patterns and, finally, to accurately disentangle escape, climatic, geochemical and hypothesized biological effects. High sensitivity is required for elemental and isotopic compositions of trace gases of interest (a small fraction of ppbv). Such an accurate monitoring of Mars atmosphere volatile composition is expected to provide the necessary reference for future composition studies of minerals, soils, bio markers, polar cap material, either by in-situ measurement, or from laboratory analyses of returned samples. The PALOMA instrument consists of: a gas purification and separation line, using techniques of chemical and cryogenic trapping, and possibly membrane permeation, a mass spectrometer working in static mode, a turbo-molecular pump that provides the required level of vacuum in the separation line and the spectrometer, a small additional stand-alone sensor for radon and its short-lived daughters measurement. It is designed to work during one full Martian year, in order to perform accurate measurements of molecular, elemental and isotopic composition of Mars atmosphere, and its seasonal, and more generally temporal, variations. The gas is sampled directly from the ambient atmosphere, without need for an external sample distribution system.