Amino acids and nucleotides must have formed before life. Must have started earlier, but step from chemical to biological evolution has left no record. It does not seem likely that life can be based on significantly different chemistry. Silicon is in some ways similar to carbon in its chemistry, but the chemical bonds are weaker, and silicon cannot make molecules as complex as carbon.
Water is the universal solvent.
Mars too cold and lacks liquid water, but formerly had more atmosphere, higher temperatures and running water. No organic compounds detected. This document was last updated August 22, 1999.