Some scientist and science fiction writers have envisioned life on other Wanes based on silicon not carbon. Based on your understanding of the chemical nature of organic molecules why is silicon a logical substitute for carbon as basis of biomolecules? Solution although silicon based life is not well accepted theory of life, I will try to explain why silicon has been chosen as an alternative to carbon. initially, the search for carbon initiated to find life or aliens on any other planets, since carbon is the major component of biomolecules in all forms of life on Earth. However, it may not be true that life forms in other planets too would contain carbon as its major component. there might be some other component as well. then research began to find an alternative for carbon search. some scientists believe that there is a possibility of siliicon based life. on an extreme world like Titan, the atmosphere contains no oxygen, all the water had been frozen to solid. But silicon is not oxidized to form inert rock.Titan has liquid methane and ethane on its surface. methane acts a good solvent for silicon. silicon molecules mimics organisc chemistry on Earth. They are stable and may be a start of alien biochemistry..