Astrobiology is the study of the origin, evolution, distribution, and future of extraterrestrial life. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry, laboratory and field research into the origins and early evolution of life on Earth, and studies of the potential for life to adapt to challenges on Earth and in outer space. Astrobiology addresses the question of whether life exists beyond Earth, and how humans can detect it if it does. (The term exobiology is similar but more specific — it covers the search for life beyond Earth, and the effects of extraterrestrial environments on living things.)
Astrobiology makes use of physics, chemistry, astronomy, biology, molecular biology, ecology, planetary science, geography, andgeology to investigate the possibility of life on other worlds and help recognize biospheres that might be different from the biosphere on Earth. Astrobiology concerns itself with interpretation of existing scientific data; given more detailed and reliable data from other parts of the universe, the roots of astrobiology itself—physics, chemistry and biology—may have their theoretical bases challenged. Although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories.
Earth is the only place in the universe known to harbor life. However, recent advances in planetary science have changed fundamental assumptions about the possibility of life in the universe, raising the estimates of habitable zones around other stars and the search for extraterrestrial microbial life. The possibility of life on Mars, either currently or in the past, is an active area of research.