It boils down to this: If you were observing the movement and composition of gases on Earth, you'd probably notice that oxygen has a tendency to "disappear" near our planet's surface. It's a tip-off that something is down here, breathing. Researchers have noticed a similar pattern on Titan, involving the disappearance of hydrogen at the moon's surface. At the same time, other researchers have also found a distinct lack of acetylene among the moon's natural hydrocarbons. Both these discoveries are important, because they fit with theoretical predictions made in 2005 about the kind of clues you'd find on a planet that was home to life forms that breathed hydrogen, ate acetylene and produced methane as a product of respiration the way we produce carbon dioxide.

via: Boing Boing