[Procyon]

Surely the science is settled and the debate is over! /SARC

There is a process whereby a types of bacteria called methanogens can synthesize methane using C0₂ and H₂ underground.

[PUGACHEV]

I recall reading that bacteria and extremeophiles have been discovered living far underground where no one had thought they could be found. It may be, in fact, that there is more life beneath the Earth's surface than above it. This might explain the organic “markers” that are often cited to support the argument that oil is of biotic origin.