This image illustrates possible ways methane might be added to Mars’ atmosphere (sources) and removed from the atmosphere (sinks). NASA’s Curiosity Mars rover has detected fluctuations in methane concentration in the atmosphere, implying both types of activity occur on modern Mars. A longer caption discusses which are sources and which are sinks. (Image Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan)
Curiosity phones home with some interesting news on Mars that has some scientists scratching their heads: it detected methane. The substance is common in the outer solar system, but the methane detected on Mars came in "whiffs," apparently from the ground. And while that's not a smoking gun for life, it is
consistent with the kind of microbes that might theoretically eek out a living under the cold, dry surface of the red planet in spots thought to be
warmer and wetter:
The NASA scientists at AGU led by MSL project scientist Dr. John Grotzinger emphasized that they do not yet know how the methane is being generated. The process could be biological or not. There are abiotic chemical processes that could produce methane. However, the MSL SAM detections were daily spikes and represent an active real ongoing process on the red planet. This alone is a very exciting aspect of the detection.
The team presented slides to describe how methane could be generated. With the known low background levels of methane at ~ 1 part per billion, an external cosmic source, for example micro-meteoroids entering the atmosphere and releasing organics which is then reduced by sunlight to methane, could be ruled out. The methane source must be of local origin.
Speculation runs that a dozen or more meters below the surface, the overburden creates enough pressure for water to exist as a liquid. Because of the planet's eccentric orbit and/or residual heat, it's possible warmth flows through deep cracks in the crust created by impacts or that formed when the surface cooled dramatically billions of years ago. That warm water could provide a reservoir giving rise to either abiotic or biological processes that produce methane. It's not outside the realm of possibility that Mars is harboring a unique science-y gift, carefully wrapped in ancient layers of red soil and oxidized rock, just waiting for the next generation of wonder junkies to discover!