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In astronomy, a thalassogen denotes a substance capable of forming a planetary ocean.〔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〕 Thalassogens are not necessarily life sustaining, although most interest has been in the context of extraterrestrial life.〔Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council. The Limits of Organic Life in Planetary Systems. National Academies Press (2007)〕 The term was coined by Isaac Asimov in his essay "The Thalassogens", later published in his 1972 collection ''The Left Hand of the Electron''.〔Isaac Asimov, The Thalassogens, The Magazine of Fantasy and Science Fiction, December 1970, ed. Edward L. Ferman, publ. Mercury Press, Inc., $0.60,〕〔Isaac Asimov, The Left Hand of the Electron, Doubleday, 0-385-04345-7, 225pp, 1972〕 Elements making up thalassogens have to be relatively abundant, the substance must be chemically stable in its environment, and must remain liquid under the conditions found on some planets. Freitas gives the following table,〔 noting that the liquid range typically increases with increasing pressure: The critical temperature and pressure represents the point where the distinction between gas and liquid vanishes, a possible upper limit for life (although life in supercritical fluids has been discussed both in science 〔 and fiction, such as in Close to Critical by Hal Clement). Later authors have also suggested sulfuric acid, ethane, and water/ammonia mixtures as possible thalassogens. The discovery of possible subsurface oceans on moons such as Europa also extends the range of possible environments. ==See also== * Extraterrestrial liquid water * Hypothetical types of biochemistry 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thalassogen」の詳細全文を読む スポンサード リンク
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