What Does Literature.....

For my literature review I will be researching the unknown of space. What possible life could be out there? This could be good and/or bad. For example if we find a planet that is livable for us it could help us in the in the future if Earth gets overpopulated. But also, there could be something that is a threat to Earth. But it could be good in some sense for us to know and get prepared for it. So my statement is what does literature say about the unknown of space.