Life finds a way to adapt. So I don't subcribe to the theory that you need certain conditions for life to survive.
There are creatures on earth that can survive in conditions that science would concider impossible.
Recently there has also been primitive life discovered on earth that does not need oxygen to survive.
Of course you cannot be certain that other life exists out there in the universe. The odds are increasing all the time as we learn about the mystery of the universe.
There is enough knowlegde available to make a resonable guess that we are unlikely to be alone, and possibly we could have a universe teeming with life.
It's only a matter of time before we find simple forms of life like bacteria.
Intelligent life though is another matter. We may be alone in our own galaxy as any intelligent not many light years from ours would know we are here! This planet is so noisy.
Intelligent life just seems to far away.