© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

8.2  Alternative Biochemistries

Professor G.C. Pimentel, chairman of a NASA Study Group on Exobiology in 1966, remarked that perhaps the most interesting and important discovery that could ever be made in the entire field of xenobiology would be the detection of extraterrestrial lifeforms based on a chemistry radically different from our own. Space probe experiments designed solely to search for Earthlike organisms cannot firmly rule out the possible presence of life solely on the basis of a negative result. Cautions Pimentel, we must beware of the hazards of "down-to-earth thinking."²³⁵³

Yet all living creatures with whom we are acquainted are comprised of complex carbon compounds immersed in liquid water. Two classes of molecules always seem to be present: Nucleic acids, the blueprints of inherited instructions, and proteins, the materials and tools with which the architecture of life is constructed.

Must life always be based on carbon chemistry in aqueous solution? If we can agree that a biochemistry is the proper format for living systems, and that a liquid phase is probably essential, does it follow that carbon and water are our only choices in the matter?

Last updated on 6 December 2008