Lots of people that don't know what their talking about posting a lot of stuff in this thread. We live in a figurative vacuum. We have no idea what the rest of the solar system is like, much less the universe. To assume we have any idea what allows and disallows life to exist is just plain stupid. As far as we know, life is simply an extension of complex chemical reactions over time. Take any planet, asteroid, whatever... with continuous chemical reactions going on for long enough, eventually those reactions could end up turning into biological reactions. It may be that nearly every planet has some sort of life on it, it's just not something we expected to find. In any event, my point is, we have no idea. My guess is intelligence will be the same way, we'll start finding stuff that "might be" intelligent and we'll argue about that for 100 years as well.