Trace gases are known to exert a tremendous influence on planetary atmospheres. By understanding spatial and temporal trace gas behavioral patterns vast amounts of information about the celestial body can be deduced, from current conditions to past history to future evolution. The discovery of episodic methane plumes on Mars argues the presence of ethane, regardless of origin, biogenic or abiogenic, even though it has yet to be detected there.

The Earth's methane is produced both by serpentinization as well as by Archaean methanogens. Methane is a potent greenhouse gas and large methane excursions on Earth have been linked with dramatic shifts in its climate, as with the Permian-Triassic extinction event. Atmospheric ethane while present on Earth at about 0.5 ppbv, results primarily from the photochemical action on methane gas. Ultraviolet photons of wavelengths shorter than 160 nm dissociate methane to a methyl radical and one hydrogen atom. When two methyl radicals recombine, the result is ethane: CH4+hn→CH3 •+•H CH3•+ •CH3+M→C2H6+M

A small fraction of terrestrial ethane is also produced by methanogens and ethanogens. Ethane is a constituent of the atmospheres of all four outer solar system planetary bodies as well as of some moons and comets but has not yet been explored or studied in Mars. Possible mechanisms that control the synthesis, occurrence and lifetime of ethane in the atmosphere of Mars are examined in this study along with the Martian trace gas profile using a 1-D photochemical model of its atmosphere. Upper limits of the flux of ethane used are based on our understanding of the Earth's atmospheric component of ethane and vertical patterns of lifetime, mixing ratio and kinetic reaction rates probed from the regolith to 240km. Ethane molecules are heavier and exhibit "creep" and pooling on the ground, allowing it to linger at the regolith. Ethane also benefits from shielding by methane molecules, allowing some ethane to persist at higher altitudes. The major loss mechanism of ethane is attack by OH radical, other species have reaction rates orders of magnitude less than the reaction with OH. Our model predictions of ethane on Mars bring us one step closer to unraveling the mystery of life on other planets.