Reconciling Methane Variations on Mars

Since the discovery of its presence in the Martian atmosphere, methane has remained an intriguing atmospheric component which source (either of biotic or abiotic origin) is not yet fully understood. The recently reported variations in the concentration of atmospheric methane have proven difficult to explain with 3-D numerical models of the atmosphere that include the known chemical and physical processes.

In a paper published this week in Nature, Franck Lefèvre and François Forget present their study to derive the implications of the observed methane concentrations on Mars and their variability. They conclude that there needs to be both an intense localised source of methane and a destruction mechanism that is much more efficient than the known atmospheric processes that break down methane.

Further, if this efficient destruction of methane occurs only close to the surface, these findings imply a very harsh environment for organic molecules to survive on the surface of Mars.

The Martian atmosphere is composed mainly of CO2 (95%), with nitrogen and argon forming the largest contributions to the remainder. Methane (CH4) was discovered to be among the other trace components as reported in 2004 from observations by both the PFS instrument on board Mars Express (Formisano et al.) and ground based telescopes (Krasnopolsky et al.). These observations also indicated that the distribution of methane was not uniform across the planet.

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