Paris, France - The presence of methane on Mars - once hailed as a possible sign of life - in fact provides evidence that life may be unsustainable on the planet, according to University of Paris researchers.
Methane was first discovered on the planet in 2003. In January this year, plumes of the gas were detected, indicating that it was distributed unevenly and implying that it had a much shorter lifetime than previously thought.
The researchers examined variations in methane levels using computer modelling, and confirmed this conclusion.
They found that methane is disappearing from the planet's atmosphere far faster than expected, indicating that the red planet is in fact an "extraordinarily harsh environment" for the survival of organic molecules - including those needed for life. The methane is disappearing from the surface within an hour, rather than over several centuries, as contional chemistry would suggest.
The discrepancy may be caused, suggest the researchers, by the presence of very reactive chemicals, such as hydrogen peroxide, in the soil. An alternative theory - that the variations in methane concentrations were caused by carbon dioxide vaporizing and then recondensing - was eliminated, as it dod not match NASA observations.
The findings are reported in Nature.