I just re-read part of the god delusion and found that i slightly misquoted. There are a billion billion planets in the universe not that can support life, but because we exist that means there is at least a 1 in a billion chance. which means that there life should exist on a billion planets
part of the full quote
-----------
Suppose life's origin on a planet took place through a hugely improbable stroke of luck, so improbable that it happens on only one in a billion planets. The National Science Foundation would laugh at any chemist whose proposed research had only a one in a hundred chance of succeeding, let alone one in a billion. Yet, given that there are at least a billion billion planets in the universe, even such absurdly low odds as these will yield life on a billion planets. And - this is where the famous anthropic principle comes in - Earth has to be one of them, because here we are.