NASA scientists reported results from the Mars Curiosity roving science lab at the American Geophysical Union to a packed room of press chomping at the bit for a big story. It turns out Mars has gas. It burps methane "sporadically, and episodically," according to Curiosity co-investigator, Sushil Atreya.
Atreya went on to say that the rover measured a sudden spike in methane in the air that was 10x stronger than background methane levels. The spike was followed by a sudden decrease back to the background. Analysis of this occurrence suggested to the team that methane was from a source that is very localized and small.
Unfortunately, the burps are not big enough to allow the lab to test for the ratios of various carbon isotopes, which would be helpful in getting to the source of the methane. But, if they encounter large enough releases in the future (tens of parts per billion, ppbv, instead of the <ten ppbv that they have seen), they will attempt an isotopic analysis.
The rover used its Sample Analysis at Mars (SAM) to "sniff" Martian air with an infrared laser multiple times over 20 months. They are reporting that the background methane in the atmosphere sits at 0.7 ppbv, whereas the burps average at 7 ppbv.
Additionally, the NASA rover detected organic molecules in rock samples, specifically chlorobenzene, at a site known as Cumberland. The significance of this finding is that organic molecules form the basis for life on Earth. However, this does not mean that this is evidence for life as organic molecules can be formed by abiotic, or non-biological, processes.
There is still no evidence whether or not Mars is currently or has ever harbored life. What we do have, though, is evidence that Mars is not a dead planet. It is currently active with various planetary processes yet to be understood.
For now, the NASA group are going to focus on refining their methods, drilling more holes, sniffing more air, pulverizing more rocks, and using deductive reasoning to address the various hypotheses about methane and organics on Mars.