Washington: New calculations suggest that methane gas on Mars may be destroyed 600 times faster than it is on Earth, and possibly in as little as one hour, which is bad news for scientists hoping to find life on the Red Planet.
If so, whatever process is responsible for the destruction of methane, 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.
Methane is the simplest organic molecule, so if something is destroying it, then other, more complex organic molecules could suffer the same fate.
The nature of this destructive mechanism is still a mystery.
Theories range from electrochemical processes caused by dust storms in the atmosphere to a reaction with oxidants, such as hydrogen peroxide or perchlorates, in the soil.
In the latter case, the team estimated that methane would only be destroyed in the 10 metres directly above the surface.
That limitation means the destruction process would have to be even more extreme – occurring in as little as one hour – to explain the observations.
“This would leave little hope that life as we know it can exist at present or that evidence of past life can be preserved in the shallow surface layer,” according to the researchers.
First Published: Thursday, August 06, 2009, 18:18