Space.com takes a look at what defines life in this nifty little article. Trying to understand what we are looking for will be immensely helpful in understanding "it" when we find "it". So they define life and what we should be looking for as we see probes to distant planets.
What is Life.
Now with that out of the way, perhaps we can start looking for life that is not necessarily carbon based and get out thinkers out of their present mind set of a planet has to be at such and such distance form the star, have water, etc etc.
Those are mineral footprints of microbes.