Mars methane ‘not from meteors’ BBC

The methane found on Mars is not brought to the planet by meteor strikes, scientists say.
Meteoritic material subjected to high temperatures did not release enough methane to account for the amount believed to be released on Mars.
The researchers argue that the methane must therefore be created by geologic or chemical processes, or it is a by-product of microbial life.
The work appears in Earth and Planetary Science Letters.
The origin of the methane on Mars has remained a mystery since it was first detected in 2004.
Because methane has a limited lifetime in the Martian atmosphere before degrading, some process must be pumping hundreds of tonnes of it into the Martian atmosphere annually to keep it at the levels that have been detected.