"This methane cannot be coming from living organisms," Jean-Pierre Lebreton, mission manager for the Huygens probe that landed on the surface of Titan Jan. 14, told The Associated Press on Wednesday.

Images snapped by the 340-kilogram (750-pound) probe as it parachuted through Titan's atmosphere from the Cassini orbiter show the moon's surface was cut by a weather system leaving deep river beds and large reservoirs, implying activity by liquid methane.

But unlike water in the Earth's atmosphere that continually renews itself, methane is destroyed by ultraviolet light, so Titan must have a source deep inside, scientists said.

Based on data collected by Huygens' instruments, Sushil Atreya, a professor of planetary science at the University of Michigan in the United States, believes a hydro-geological process between water and rocks deep inside the moon could be producing the methane.

"I think the process is quite likely in the interior of Titan," Atreya said in a telephone interview.

The process is called serpentinisation and is basically the reaction between water and rocks at 100 to 400 degrees Celsius (212 to 752 degrees Fahrenheit), he said.

from http://www.space.com/scienceastronomy/ap_huygens_update_050127.html
If it works on Titan why not Mars? i.e. biology need not be the source.