Methane either can arise from microbial activity in shallow deposits of organic material, or it can come from more deep-seated processes involving oil formation.

MSN: Expedition finds 40 unknown gas seeps off US East Coast

Moreover, the Curiosity rover, which is equipped with 11 scientific instruments to probe for conditions suitable for life, isn't designed to detect the signs of microbial activity or any traces of fossilized bacteria.

WSJ: Scientists Say Microbial Life Was Possible on Mars