Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluviolacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds’ little-weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, although inconsistent with many previously proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake-forming climates, if methane clathrate initially occupies more than 4% of the total volume in which it is thermodynamically stable. Such occupancy fractions are consistent with methane production by water–rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars

Role of mineral surfaces in prebiotic processes and space-like conditions

The study of the interactions between organic molecules and minerals is fundamental to unravel the prebiotic processes that led to the emergence of life on Earth or possibly on other planets. Mineral surfaces may act as adsorbents, templates and catalysts driving the abiotic evolution of chemical systems on early Earth and in space towards increasing molecular complexity. Investigations about molecule-mineral interactions provide also important scientific support to space missions devoted to the search of past or present signs of life in the form of molecular biomarkers that can be included inside rock samples. Such studies are essential for establishing habitability of other planets, selection of sampling sites, identification of potential biomarkers, correct interpretation of data collected during mission operative periods, development of suitable life detection methods and technologies for in situ analysis. In this chapter, the possible roles of minerals have been examined both from the standpoint of prebiotic chemistry and life detection investigations focusing mainly on Mars exploration