Does Methane Shows Life In Mars?
Atmospheric methane on earth is mostly genarated by biological processes. So, if there is methane on the atmosphere of a planet, possibly some signs of life can be found there.
The above assumption is applied to Mars now. Because, according to Curiosity team, methane concentrations on the air at Gale Crater increased by a factor of 10 in only two months between late 2013 and early 2014. So, there might be some microbiological activities on Mars.
However there are some more possible answers too. For example some geological processes can also produce methane.
For the details of some possible sceanarios, you must read the artical on www.space.com
In any circumstances, we should investïgate Mars better for the possibility of life.