Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Neutral Atmosphere

  • Franck Selsis
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1050-2


In physics, a neutral atmosphere is an atmosphere consisting of neutral gas, in contrast with the ionosphere. In chemistry, it is an atmosphere which neither oxidizes nor reduces immersed compounds. A planetary atmosphere is rarely chemically neutral because of the photodissociation by stellar UV radiation that produces oxidizing and/or reducing radicals and atoms. An atmosphere dominated by carbon dioxide (CO2), nitrogen (N2), and water vapor (H2O), which many believe to be a good model for the prebiotic Earth’s atmosphere, is often referred to as a neutral atmosphere, as it contains neither molecular oxygen (O2) nor reduced forms of carbon gases, such as methane (CH4) or carbon monoxide (CO), nor reduced nitrogen species, such as ammonia (NH3).

See Also


Carbon Dioxide Water Vapor Carbon Monoxide Bioorganic Chemistry Molecular Oxygen 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Université de Bordeaux-CNRSBordeauxFrance