NASA believes that methane during these events erupt from an underground source every now and then, which means some process or reaction might be going on underneath the Martian surface. On Earth, methane is largely produced by human activities, the trash we dump in landfills, as well as animal and human waste. While it's possible that microbes that release methane waste are living on the planet, that doesn't automatically mean there's life on Mars, or even that it supported life long ago. "There are many possible sources, biological or non-biological," says Curiosity science team member Sushil Atreya, "such as interaction of water and rock."

As the Sarcastic Rover account posted on Twitter:

Martian Methane is NOT a canary in the coal mine of life. But like any dead bird, it's a good sign something might be worth a closer look. - SarcasticRover (@SarcasticRover) December 16, 2014

There's evidence suggesting that the Gale crater was a lake for millions of years before it dried up, and the rover has recently discovered that each cubic foot of soil in the crater contain two pints of water. So, as Atreya says, the source could be non-biological. Methane, as you might know, can also be used as fuel. If we can find a way to harness the gas on Mars, future manned explorations might be able to use it to power their equipment, allowing them to stay longer on the red planet.

In addition to sniffing out methane, Curiosity has also found chlorine-containing organic molecules in the soil samples it drilled from the Gale crater. NASA says this is Curiosity's "first definitive detection of organic molecules at Mars," because while it has detected similar molecules in the past, this is the first time the ground crew made sure they came from the planet and weren't created by SAM's instruments during testing. In fact, the rover drilled the sample back in May 2013, but NASA's only announcing this now, as the scientists spent over a year replicating SAM's tests and analyzing the results.

[Image credit: NASA/JPL-Caltech/MSSS]