However, the odds (mathematical probability) if life existing elsewhere are so astronomical as to be impossible even with the billions of galaxies. Check out www.reasons.org and learn more. There are many factors that must be in place very precisely in order for life to exist. Here are some examples: Thickness of the earth's crust - any thinner or thicker, life would be impossible; ozone layer - any thicker or thinner, life would be impossible; distance of earth from sun; size and intensity of sun; presencea and location of Jupiter which keeps solar system stable; location of sun in between two spiral arms in milky way galaxy - if sun were on a spiral arm, life would be impossible; strong nuclear force; weak nuclear force; magnetic field, tilt of earth's axis which causes 4 seasons and allows life, size, distance of our moon - without it there would be no tides and no life; type of planet earth is - we have found no others like it or resembling it - all planets found so far are gas giants like jupiter; and there are many more such factors. All of these factors must be precise in order for life to exist. The odds of another planet having ALL of these factors is beyond the realm of possibility.
If this is so, then every rocky planet could easily have such microbial life, and it wouldn't require any conditions at all on the surface, or even the presence of a sun.
If the question is higher lifeforms with consciousness and a brainstem to house it, then the conditions appear rare. If the question is life in any form, then the galaxy and the universe could easily be filled with it.