The first definitive detection of methane in the atmosphere of Mars indicates the planet is alive in the sense that it still has geologic activity powered by heat from its interior, according to a team of NASA and university scientists.
The team used spectrometer instruments attached to several telescopes to detect plumes of methane that were emitted from specific sites during the warmer seasons - spring and summer.
Though nothing conclusive can yet be determined, it is possible that the detected methane was either produced by geologic processes such as the oxidation of iron (serpentinization) or by microscopic Martian life below the planet's surface. The methane released today could be produced currently, or it could be ancient methane trapped in ice 'cages' called clathrates or as gas below a sub-surface ice layer.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0