Methane On Mars May Indicate Living Planet
Riding with Robots writes "NASA is announcing today that the definitive detection of methane in the Martian atmosphere means the planet is still alive, at least geologically, and perhaps even biologically. 'Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars indicates some ongoing process is releasing the gas,' said one agency scientist. The gas was detected with observations made over over several Martian years with NASA telescopes at Mauna Kea, Hawaii. Both biological and geological processes could explain the methane."
This was reported by Mars Express in 2004.
In particular, mercaptans, hydrogen sulfide, and other sulfur compounds are responsible for most the disagreeable oder of flatus.