The presence of atmospheric methane has a role in the scientific search for extra-terrestrial life. The justification is that on an astronomical timescale, methane in the atmosphere of an Earth-like celestial body will quickly dissipate, and that its presence on such a planet or moon therefore indicates that something is replenishing it. If methane is detected (by using a spectrometer for example) this may indicate that life is, or recently was, present.
This was debated when methane was discovered in the Martian atmosphere by M.J. Mumma of NASAs Goddard Flight Center, and verified by the Mars Express Orbiter (2004) and in Titans atmosphere by the Huygens probe (2005). This debate was furthered with the discovery of transient, spikes of methane on Mars by the Curiosity Rover.
It is argued that atmospheric methane can come from volcanoes or other fissures in the planet's crust and that without an isotopic signature, the origin or source may be difficult to identify.
On 13 April 2017, NASA confirmed that the dive of the Cassini orbiter spacecraft on 28 October 2015 discovered an Enceladus plume which has all the ingredients for methanogenesis-based life forms to feed on. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea of Enceladus; the new finding supported that conclusion, and add that the rock appears to be reacting chemically. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen, and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.