Or there isn’t any life on those places and this is abiogenic methane.
An interesting supposed fact about methane is that it is basically unstable and breaks down from sunlight. And so its presence means it is somehow being replenished, possibly by lifeforms.
From Universe Today...
“As methane is broken down by light-induced chemical reactions over a timescale of tens of millions of years, it can’t just be a remnant of the atmosphere present when Titan itself was formed, and it must be replenished quite regularly,” said Tobie.
http://www.universetoday.com/8003/the-source-of-titans-methane/
Abstract:
Recently, methane (CH4) of possible abiogenic origin has been reported from many localities within Earth’s crust. However, little is known about the mechanisms of abiogenic methane formation, or about isotopic fractionation during such processes.
Here, a hydrothermally formed nickel-iron alloy was shown to catalyze the otherwise prohibitively slow formation of abiogenic CH4from dissolved bicarbonate ...”
Abiogenic petroleum
Abiogenic petroleum origin is a term used to describe a number of different hypotheses which propose that petroleum and natural gas are formed by inorganic means rather than by the decomposition of organisms. The two principal abiogenic petroleum hypotheses, the deep gas hypothesis of Thomas Gold and the deep abiotic petroleum hypothesis, have been scientifically reviewed without confirmation.[1] Scientific opinion on the origin of oil and gas is that all natural oil and gas deposits on Earth are fossil fuels and are, therefore, biogenic. Abiogenesis of small quantities of oil and gas remains a minor area of ongoing research.
Some abiogenic hypotheses have proposed that oil and gas did not originate from fossil deposits, but have instead originated from deep carbon deposits, present since the formation of the Earth.[2] Additionally, it has been suggested that hydrocarbons may have arrived on Earth from solid bodies such as comets and asteroids from the late formation of the Solar System, carrying hydrocarbons with them.[3][4]
Some abiogenic hypotheses gained limited popularity among geologists over the past several centuries. Scientists in the former Soviet Union widely held that significant petroleum deposits could be attributed to abiogenic origin, though this view fell out of favor toward the end of the 20th century because they did not make useful predictions for the discovery of oil deposits.[1] Previous to today, it was generally accepted that abiogenic formation of petroleum has insufficient scientific support and that oil and gas fuels on Earth are formed almost exclusively from organic material.[5]
The abiogenic hypothesis regained support in 2009 when researchers at the Royal Institute of Technology (KTH) in Stockholm reported they believed they had proven that fossils from animals and plants are not necessary for crude oil and natural gas to be generated.[6][7] ...”