Astrobiology

The subject of astrobiology is of great interest to a wide variety of public audiences, and this interest is likely to grow as astrobiology investigations are launched on a growing number of space exploration missions. Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. It is a multidisciplinary field of research, drawing on knowledge and expertise in astronomy, biology (particularly microbiology and evolutionary biology), chemistry, earth and planetary sciences, physics, and many hybrid or subdisciplines. Astrobiology also involves, to a lesser extent, studies in the humanities (primarily philosophy and theology) and social sciences. The idea that life on other planets might actually exist (or have existed in the past) obviously captures public attention.

Astrobiology encompasses the search for evidence of prebiotic chemistry (chemical steps leading to the origin of life), signs of past or present life on Mars and other bodies in our solar system, habitable environments in our solar system, and habitable planets outside our solar system. It also encompasses laboratory and field research focused on understanding the origins and early evolution of life on Earth and on Earth itself, as well as studies of the potential for life to adapt to challenges on Earth (for example, climate change) and in space (for example, cosmic radiation and reduced [Page 68]gravity). Today, astrobiology investigations on planetary exploration missions are focusing first on determining whether other planetary environments are now or have ever been habitable.

The search for evidence of existing or past extraterrestrial life should be distinguished from the search for evidence of extraterrestrial prebiotic chemistry or habitability, and the search for evidence of extraterrestrial life should be distinguished from the search for evidence of extraterrestrial intelligent life. The search for evidence of extraterrestrial intelligent life is a very different enterprise than the search for evidence of extraterrestrial life. Search for extraterrestrial intelligence projects look for evidence of extraterrestrial technology—for example, radio signals that are not of natural or other known origins—as markers of intelligent life.

The study of the origins and evolution of life on Earth, the origin and evolution of Earth itself and its sister planets, the origins and evolution of life in the universe, and the origins and evolution of the universe itself are intricately intertwined. In their research on these topics, astrobiologists have learned that life as we know it—that is, carbon-based cellular life—can survive in virtually all terrestrial environmental extremes, from areas subject to nuclear radiation to permafrost and the Earth's deep subsurface. At the same time that studies of the origin, evolution, and distribution of life on Earth are revealing that life is highly resilient, these same lines of research are helping to reveal how life and its environment are deeply interdependent, improving understanding of life on Earth and prospects for life elsewhere, contributing to the understanding of global climate history and evolution.

The U.S. National Aeronautics and Space Administration (NASA) funds an astrobiology research program that is focused on three basic questions: How does life begin and evolve? Is there life beyond Earth, and if so, how can we detect it? What is the future of life on Earth and in the universe? Astrobiology research around the world tends to focus on these three questions as well. Australia, Canada, France, Germany, Russia, Spain, and the United Kingdom are among a growing number of nations that are funding astro-biology research. International collaborations in astrobiology are common.

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