The Curiosity rover has confirmed the presence of methane in the atmosphere of Mars. It appears to come from localized sources on the Red Planet. Its level was observed to rise ten-fold during the Martian Summer, in that location.

This appears more like a biological phenomenon than very low-level volcanic activity. Higher seasonal temperatures could cause dormant life to flourish, just as is often the case on our planet. Such temperature rises do not appear to connected to an increase in geothermal activity, which is the other likely source of methane on Mars.
At most, Mars apparently has about 260 times less methane than Earth. This appears consonant with a remnant of life, left over from what is believed to have been a more hospitable period, very early in the history of the Red Planet. Link to article on this:
http://phys.org/news/2015-02-curiosity-robot-methane-mars-atmosphere.html

I tend to believe there is a substantial amount of microbial life below the surface of Mars. It only makes sense now that biologists have found living microbes deep below the surface of our planet living in the rocks.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.