Encyclopedia of Astrobiology

2011 Edition
| Editors: Muriel Gargaud, Ricardo Amils, José Cernicharo Quintanilla, Henderson James (Jim) CleavesII, William M. Irvine, Daniele L. Pinti, Michel Viso

Neutral Atmosphere

Reference work entry
DOI: https://doi.org/10.1007/978-3-642-11274-4_1050


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 photo-dissociation 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).

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© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  1. 1.Université de Bordeaux-CNRSBordeauxFrance