Pronunciation key

( ĕk′sō-bī-ŏlə-jē )



  1. The branch of space biology in science which focuses on the study of life on planets other than Earth and the search for living organisms, especially intelligent life outside our own solar system.
  2. A branch of biology that focuses on the effects of extraterrestrial space on living organisms.

Also known as Xenobiology, Astrobiology and Extraterrestrial Life.

The word exobiology was coined by the U.S. geneticist Joshua Lederberg. The word commonly used in the Soviet Union, translates to English as Astrobiology.

Exobiology: Matter, Energy, and Information in the Origin and Evolution of Life in the Universe: Proceedings of the Fifth Trieste Conference on Chemical Evolution: An Abdus Salam Memorial Trieste, Italy, 22 26 September 1997

The Living Universe: NASA and the Development of Astrobiology

Remote observations of planets and other bodies in outer space provide information about their unique physical environment. However determining the presence of life is much more difficult. Techniques have been designed and implemented to detect life-forms, artifacts produced by intelligent life, waste products of metabolic reactions, remnants of past life, pre-biological molecules that may represent early stages of evolution, or substances such as carbon which are crucial in the development of life as it is experienced on Earth. Communication efforts range from broadcasting radio transmissions and pictorial diagrams by satellite, as well as monitoring for radio signals from stars and other objects for long periods of time.

Though extraterrestrial life may never be found, some experiments have been conducted in space under environmental conditions difficult to establish on Earth are valuable. One example is testing in a zero gravity environment. By doing so allows testing not only accepted theories about life processes, but also of the relationships between physical and biological factors.

ex′o•bi′o•log′i•cal (-ə-lŏj′ǐ-kəl) adj.
ex′o•bi•ol′o•gist n.

Also see Life, Extraterrestrial


  • Encyclopedia and Dictionary of Medicine, Nursing and Allied Health ©1978
  • Encyclopedia Britannica Micropedia ©1984
  • The American Heritage Dictionary, Second College Edition ©1985
  • Grolier Encyclopedia of Knowledge ©1991
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