Journées SF2A (Société Française d'Astronomie et d'Astrophysique)

Recent observations have evidenced traces of methane heterogeneously distributed in the Martian atmosphere (Krasnopolsky et al. 2004). However, because the lifetime of CH_4 in the atmosphere of Mars is estimated to be around 250-430 years on the basis of gas-phase chemistry (Krasnopolsky et al. 2004), its actual sources on Mars remain controversial. Among other assumptions, it has been proposed (Chastain & Chevrier 2007) that clathrate hydrates located in the subsurface of Mars could be at the origin of the small quantities of CH_4 detected. In the present work, we have calculated the relative abundance of CH_4 in clathrate hydrates on Mars, using a statistical model based on the theory of van der Waals and Platteeuw (1959). The results show that methane enriched clathrate hydrates could be stable in the subsurface of Mars only if a primitive methane-rich atmosphere has existed or if a subsurface source of CH_4 has been (or is still) present