Traces of Methane have been seen on Mars in the past. While it is possible that this Methane and the other organic molecules are indications of the presence of bacteria on or near the surface of Mars, there are non-biological explanations as well. Scientists are continually analyzing data in an attempt to determine the source of this Methane. For the full NASA post go to....Dec. 16, 2014: NASA's Mars Curiosity rover has measured a tenfold spike in methane, an organic chemical, in the atmosphere around it and detected other organic molecules in a rock-powder sample collected by the robotic laboratory’s drill."This temporary increase in methane -- sharply up and then back down -- tells us there must be some relatively localized source," said Sushil Atreya of the University of Michigan, Ann Arbor, and Curiosity rover science team. "There are many possible sources, biological or non-biological, such as interaction of water and rock."
Also see this post from the University of Michigan....