Methane on Mars

800px-Gusev_Spirit_01

18th December 2014.

Is there life on Mars?  New data from NASA’s Curiosity rover, published in Science, has energised the debate.  Methane is so interesting to those seeking evidence of life on Mars because on Earth the overwhelming majority of the gas is produced by living things. The measurements were taken by the Tunable Laser Spectrometer over a period of twenty months, and record a mean background level of atmospheric methane of 0.69 ppbv.  However, at the end of 2013 and start of 2014, four consecutive measurements reached values of 7.2 ppbv.  This spike showed no correlation with relative humidity, atmospheric pressure, ground temperature, air temperature, or radiation levels.  The authors suggest that there may be a negative correlation with column measurements of water vapour and oxygen abundance, but point to a lack of data to fully accept or refute this hypothesis.

The observed high concentrations appeared to be spatially restricted; all the high measurements were taken within 200-300 m of each other, yet were not found after the rover moved 1 km away.  Due to the fact that the spike was sustained for two months before suddenly dropping, the authors conclude that the origin of the methane is likely to be local production or release, with concentrations quickly dipping as the production mechanism ceases.

A MethaneNet article from 2013 discussed some of the possible mechanisms that could lead to atmospheric methane on Mars, which include both biological and physical processes.  Lead author of the paper, Christopher Webster from the Jet Propulsion Laboratory said: “It’s equally likely to be geophysical or biogenic… The fact that we’ve seen it, in a sense, argues that the stock in a possible biogenic source went up.”

MethaneNet spoke to Dr Manish Patel at the Open University, for his thoughts on the latest news.  Dr Patel’s research interests include astrobiology and the modelling of sudden releases of methane from subsurface clathrates.  He said: “This result is a nice confirmation that the methane is there.  There has been a lot of scepticism about martian methane over the last few years, so it is great to get confirmation that what we are seeking to measure is indeed there.”  Dr Patel is also involved as a Co-PI in constructing NOMAD (Nadir and Occultation for MArs Discovery) for the ExoMars Trace Gas Orbiter project in 2016.  Dr Patel said: “NOMAD is led by the Belgian Institute for Space Aeronomy, and is going to map in even more detail the trace gases such as methane in the martian atmosphere using a suite of spectrometers.”

Whether or not the observed martian methane turns out to be of biotic or abiotic origin, it certainly seems an exciting time for research into the atmosphere of Mars.

Reference: Mars methane detection and variability at Gale crater. 2014. Webster, C.R., Mahaffy, P.R., Atreya, S.K., et el. Science, DOI 10.1126/science.1261713

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