KRI

My intiution is that 3 things are necessary for life to evolve: building block atom, solvent molecule and oxidizing agent. In Earth these are carbon, water and oxygen (or sulphur in some extreme cases). Carbon is more or less irreplaceable. Silicon atoms cannot form long chains like carbon. You cannot build any flexible and durable structure with silicon. Ammonia-nitrogen might be an alternative solvent-oxidizer pair for low temperature environments. Though ammonia is far less common than water in the universe. Have you watched Europa Report? It shows what happens when humans behave like kerbals in space. ) Spoiler: They die! It has a happy and corny ending. I wished they had put more thought in the second half of the scenario, but well, they do not make sci-fi like they used to.