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Glossary term: Extraterrestrial Life

Description: Extraterrestrial life or alien life refers to forms of life that may occur outside Earth and which did not originate on Earth. Astronomers estimate that, on average, each star in our galaxy has more than one planet. A number of these planets are expected to offer conditions similar to those that allowed life to arise here on Earth, in particular liquid water. Just as on Earth, the presence of certain kinds of life is expected to significantly alter the chemical composition of such a planet's atmosphere, and a major goal of astronomy for the coming decades is to detect the presence of life by studying distant planetary atmospheres. The SETI project, on the other hand, has long been searching for possible radio signals from intelligent life on other worlds. In our own Solar System, conditions in the ice-covered oceans of Jupiter's moon Europa, and Saturn's moon Enceladus, might allow for life.

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The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".