EXOBIOLOGY

also called Xenobiology, or Astrobiology, a branch of biology that deals with the search for extraterrestrial life (q.v.), especially intelligent life, outside the solar system. The word exobiology was coined by the American geneticist Joshua Lederberg; the word commonly used in Russia translates into English as astrobiology. Remote astronomical observations of a planet or other body provide information about its physical environment, but the determination of the presence of life is much more difficult. Techniques are designed to detect life-forms, artifacts produced by intelligent life, waste products of metabolic reactions, remnants of former life, prebiological molecules that may represent early evolutionary stages, or substances such as carbon that are necessary for life as it is experienced on Earth. If these conditions are present, microorganisms would be the most likely life-forms present beyond Earth; however, the possibility of life unlike that on Earth should not be ruled out. Theoretical silicon-based life or unknown forms of life may exist in places where conditions do not warrant the search for life. Earth-based communication efforts to locate extraterrestrial life have ranged from sending coded radio transmissions and pictorial diagrams by satellite to monitoring radio emissions from stars and starlike objects.