Just saw a segment on BBC News America about methane gas being "belched" out from under the surface of Mars which may mean, according to a senior planetary scientist at NASA Goddard Spaceflight Center, ". . . there could be biology that's going on either very near the surface or deep below the permafrost layer (of Mars)"
Life, if it does now exist on Mars, may be microbial. So, I would not expect blasts of flatulence from little green men. However, if there is something now living on Mars, it lends more credence to the possibility of life in another solar system and/or life existing in environments which do not match any environment on Earth.