The search for extraterrestrial intelligence has been narrowed down to planets that are similar to earth. If a planet is hazardous to earth life, then it is said to be inhabitable. Is that right? If so, WHY? After all, we can only define life according to what we have here on Earth. Something EXTRAterrestrial is not of our world, therefore it doesn't neccesarily have to be able to live in earthly conditions...for that matter, it could live in what seems to us to be the most harshest conditions we can think of. so, I don't understand why certain planets have the potential to support life and others don't.