Destruction of Methane on Mars: Bad News for Life

(Image: NASA/ESA/Hubble Heritage Team/STScI/AURA/J. Bell/Cornell University/M. Wolff/Space Science Institute)

Methane gas on Mars may be destroyed 600 times faster than it is on Earth – and possibly in as little as one hour, new calculations suggest. If so, whatever process is responsible for the destruction may be wiping out other organic molecules, which are necessary for life as we know it.

In 2003, researchers detected methane on Mars. Since sunlight destroys methane on Earth in about 330 years, the discovery suggested that the gas was being replenished by geological processes or possibly even methane-producing bacteria.

The mystery deepened when researchers reported that the methane is not spread evenly through the atmosphere, but is concentrated in certain areas. That is a puzzle because atmospheric currents are expected to spread the gas evenly around the planet in a matter of weeks or months.

To see if these methane pockets could be explained by atmospheric chemistry, Franck Lefevre and Francois Forget of the Pierre and Marie Curie University in Paris tried to recreate the observations with a global climate model that accounted for the winds, turbulence and chemistry of all the known compounds in the Martian atmosphere.

But the model, which was based on methane's behaviour on Earth, failed to generate the pockets of methane gas observed, even though it perfectly reproduced the observed distribution of other atmospheric gases.

By introducing idealised methane molecules, or 'tracers', with lifetimes ranging from a few days to thousands of years into the model, the team found that the only way to reproduce the observations was to have an intense source of methane that is destroyed within 200 terrestrial days – 600 times faster than on Earth.