In recent years science has found bacteria and other simple life forms in all sort of places that only a few decades ago (or less) was thought impossible, undersea volcanic vent's, inside rocks in the dried out mud flats of death vally and so on.
It's only mans current technical limits and level of knowledge and understanding of the life and the universe that we only know what we do today. To me it will come as no great surprise what current and future research may find and reveal about the existence of life however small it may be or in which environments it may live.
The only one thing I find odd about current science and the search for life (ie:SETI) is the presumption that other forms of life out their would use radio waves to communicate, just because we haven't broken past this barrier yet doesn't mean that other life forms haven't either. They may use some other currently unknown to us form of communication that we have yet to even dream of... Just a thought...