On the Potential of Silicon as a Building Block for Life

Despite more than one hundred years of work on organosilicon chemistry, the basis for the plausibility of silicon-based life has never been systematically addressed nor objectively reviewed. We present a comprehensive assessment of the possibility of silicon-based biochemistry. We assess whether or not silicon chemistry meets the requirements for chemical diversity and reactivity as compared to carbon. To expand the possibility of plausible silicon biochemistry, we explore silicon’s chemical complexity in diverse solvents found in planetary environments, including water, cryosolvents, and sulfuric acid. In no environment is a life based primarily around silicon chemistry a plausible option. We find that in a water-rich environment silicon’s chemical capacity is highly limited due to ubiquitous silica formation. Any sort of biochemistry is implausible in cryogenic solvents, because of solubility limits. Sulfuric acid, surprisingly, appears to be able to support a much larger diversity of organosilicon chemistry than water. We should therefore think about silicon as a contributor to biochemistry (as a common heteroatom in hypothetical sulfuric acid biochemistry and a rare specialized heteroatom in water solvent) rather than a main building block of life.