First, as posted a few days ago, there was the mystery of seemingly missing methane on an exoplanet. Now there’s another methane-related riddle, on Mars. First detected in 2003, the gas is being continually produced, but the origin is still unknown. It could be either geological or biological, and is concentrated in three areas in the northern hemisphere, regions of previous volcanic activity and underground water ice. The amount also varies with the seasons, increasing in the spring, more so in the summer, peaking in autumn and then rapidly decreasing in winter. That pattern could fit with either still-occurring hydrothermal activity or biology, ie. microbes, or both.
The new puzzle though is why the methane has now been observed to remain in the atmosphere for less than a Martian year. It was expected to last longer, so something is destroying it relatively quickly, faster than expected for a photochemical process (destruction by sunlight). As stated in the article, perhaps chemicals from the soil, being alofted into the atmosphere by winds.
So both the origin and demise of the Martian methane are currently unknown. Hopefully more answers can come from the upcoming Mars Science Laboratory rover (Curiosity) and the ExoMars missions, both of which are equipped to analyse the methane in more detail…