|Above: An image representing methane abundance on Mars|
Methane gas is a potential tracer for life - it's also a potential tracer for non living organic matter. Even so, the detection of plumes of methane in the martian atmosphere caused excitment a while back. But the Rovers on the ground couldn't confirm the methane - until just today when a paper has popped up, seemingly saying that Curiosity rover has found Methane. I'll quote the abstract below, and here's the link.
Mars methane detection and variability at Gale crater
Reports of plumes or patches of methane in the Martian atmosphere that vary over monthly timescales have defied explanation to date. From in situ measurements made over a 20-month period by the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars (SAM) instrument suite on Curiosity at Gale Crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 ppbv at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet (UV) degradation of accreted interplanetary dust particles (IDP’s) or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period, we observed elevated levels of methane of 7.2 ± 2.1 (95% CI) ppbv implying that Mars is episodically producing methane from an additional unknown source.
I'll be clear: This is not the moment to break out the 'we discovered alien life' champagne. But if this is what it seems, and it's confirmed, then it might be a little bit of evidence - not conclusive by any stretch - towards the 'something survives on Mars' point of view.
I can add to this the NASA press release, and this video: