Methane on Mars

Four research groups have independently reported the possible detection of methane in the Martian atmosphere using spacecraft and ground-based observations. Although each observation uses different instruments and has specific uncertainties, these observations produce similar results in terms of seasonal variations and global mean amounts of methane, implying that methane may be present in the current atmosphere of Mars. If methane is present on Mars, it is likely to be of geochemical and/or biological origin. A release of methane from the subsurface to the atmosphere may be associated with the formation of specific landforms, such as mud volcanoes, as observed on Earth. Although the presence of such landforms has been suggested on Mars, a causal link between these landforms and atmospheric methane has not been confirmed. We report that the observed lifetime of methane on Mars is shorter than that estimated from conventional photochemical models, with this short lifetime requiring rapid consumption of methane by a currently unknown process. This article summarizes observational results and our current understanding of physicochemical processes involved in the production, release, and consumption of Martian methane, and outlines future observation plans for documenting the abundance of methane on Mars.