The source of Titan's methane remains a mystery because methane in the atmosphere is broken down over relatively short time scales by sunlight
Hang on a minute: wasn't free methane being used as an indicator of life on Mars? So where does this methane come from?
Kind of. Methane could be generated on Mars either by biological means, or by geological means.
If its geological, then the sub-surface of Mars is more active than we thought.
If its biological in origin, well there's the biggest discovery in human history right there.
For the record, im guessing geological.