A recent paper shows that methane was found in Mars' atmosphere. They also found that the amount of it varies with the seasons. This is a significant advance in the search for microbial life on Mars. Methane normally disappears from Mar's atmosphere over the course of only a few years.
These findings show that something is replenishing methane in Mars' atmosphere. The process that is replenishing Methane could either be biological or geological. Since methane is such a simple molecule to make there are many possible sources, but there is always that chance it could be biological.
Phil Plait, the Bad Astronomer, has a great blog post explaining the "Mars methane media mess". I have to disagree with Phil about NASA's headline for the finding: "Methane Discovery Reveals Mars is Not a Dead Planet." NASA uses the term "dead", meaning that there is no change occurring. It has for quite awhile and will continue to use it because it attracts readers to look further into the subject.