Its quite believable, I believe that there is definitely life in other worlds, why wouldn't there be, its just completely stupid if you believe that we are the only living oranisms around, there must be others... I believe that we must have people trying to warn us etc.
Why isn't it possible to have life on other planets, you are aware that one of Saturns moons has got pools of liquid on it and they aren't sure what it is, but its habitable...
