Cosmic Biology

Book excerpt: In Cosmic Biology, Louis Irwin and Dirk Schulze-Makuch guide readers through the range of planetary habitats found in our Solar System and those likely to be found throughout the universe. Based on our current knowledge of chemistry, energy, and evolutionary tendencies, the authors envision a variety of possible life forms. These range from the familiar species found on Earth to increasingly exotic examples possible under the different conditions of other planets and their satellites. Discussions of the great variety of life forms that could evolve in these diverse environments have become particularly relevant in recent years with the discovery of around 300 exoplanets in orbit around other stars and the possibilities for the existence of life in these planetary systems. The book also posits a taxonomic classification of the various forms of life that might be found, including speculation on the relative abundance of different forms and the generic fate of living systems. The fate and future of life on Earth will also be considered. The closing passages address the Fermi Paradox, and conclude with philosophical reflections on the possible place of Homo sapiens in the potentially vast stream of life across the galaxies.