[[Image:Gas_giants.jpg|right|thumb|200px|The gas giants outer planets (Jupiter, Saturn, Uranus, Neptune) have reducing atmospheres]]
Una '''atmósfera reductora''' es una [[atmósfera]], sin cantidades significativas de [[oxígeno]] libre (O<sub>2</sub>)
y otros gases o vapores oxidantes evitando de este modo la [[oxidación]].<ref name=how>{{cita libro|autor=Dembski, William A.; Wells, Jonathan|título=How to Be an Intellectually Fulfilled Atheist (or not)|editorial=ISI Books|ubicación=Wilmington, Delaware|año=2008|página=18|isbn=978-1-933859-84-2}}</ref> Los [[química|químicos]] refer to an atmosphere with abundance of se refieren a una atmósfera con abundancia de átomos de [[hydrogenhidrógeno]] atoms, or other substances that readily provides u otras sustancias que proporcionan fácilmente [[electronselectrones]], and a scarcity of oxygen and y una escasez de átomos de oxígeno y [[nitrogennitrógeno]] atoms as como "reducedreductora".<ref name=shapiro>{{cite bookcita libro|authorautor=Shapiro, Robert|titletítulo=Origins: A Skeptic's Guide to the Creation of Life on Earth|publishereditorial=Bantam Books|locationubicación=Toronto|yearaño=1987|pagepágina=65|isbn=0-553-34355-6}}</ref> A reducing atmosphere contains reductantsUna atmósfera reductora contiene reductores, or molecules saturated with hydrogen atomso moléculas saturadas con átomos de hidrógeno, such as tales como [[ammoniaamonio]] (NH<sub>3</sub>) and y [[methanemetano]] (CH<sub>4</sub>), which are able to reduce other moleculesque son capaces de reducir otras moléculas. So Así el [[carboncarbono]], for examplepor ejemplo, appears in its most reduced form aparece en su forma más reducida (CH<sub>4</sub>) but not in an oxidized form pero no en una forma oxidada (CO) or a fully oxidized form o una forma completamente oxidada (CO<sub>2</sub>). The discussion of the degree of oxidation of El debate sobre el grado de oxidación de la atmósfera primitiva de la [[EarthTierra]]'s early atmosphere is one of the fundamental topics of the es uno de los temas fundamentales de los modelos de la [[origin of lifeorigen de la vida]] models.
==The primitive atmosphereLa atmósfera primitiva==[[File:Miller-Urey.png|thumb|200px|Picture of Imagen de [[Stanley Miller|Miller]]-Urey experiment layout, showing the primitive atmosphere assumed by them]]
Theories of the origin of life initially assumed that the primitive atmosphere should be a reducing one in order to prevent oxidative destruction of the components of the "primordial soup".<ref>{{cite book|author=Aw, S. E|title=Chemical Evolution|publisher=Master Books|location=San Diego, California|year=1982|isbn=0-89051-082-2}}</ref> So the evolutionists theorize an early atmosphere without oxygen. [[Oparin]] believed that the Earth's early atmosphere was composed of hydrogen (H<sub>2</sub>), methane (CH<sub>4</sub>), ammonia (NH<sub>3</sub>) and [[water]] vapor (H<sub>2</sub>O), containing no oxygen.<ref name=how /> [[J. B. S. Haldane|Haldane]] postulated the same theory and his most important conclusions were presented in a short article for the ''Rationalist Annual''.<ref name=clark>{{cite book|author=Clark, Ronald W|title=J B S: The Life and Work of J. B. S. Haldane|publisher=Coward-McCann, Inc.|location=New York|year=1969|page=93-94|id=Library of Congress Catalog Card Number:68-11875}}</ref> Other scientists who corroborated this model of atmosphere were Miller and Urey. They reasoned that a small but significant amount of H<sub>2</sub> remained in the primordial atmosphere and reacted with atoms of carbon, nitrogen or oxigen forming this kind of atmosphere.<ref>{{cite book|author=[[Charles Thaxton|Thaxton, Charles B.]]; Bradley, Walter L.; Olsen, Roger L|title=The Mistery of Life's Origin: Reassessing Current Theories|publisher=Philosophical Library|location=New York|year=1984|page=74|isbn=0-8022-2447-4}}</ref> By sparking together hydrogen, methane, ammonia, and water vapor, they produced several amino acids, the building blocks of organic life.<ref>{{cite book|author=Smith, A. E. Wilder|authorlink=A. E. Wilder-Smith|title=The Creation of Life: A Cybernetic Approach to Evolution|publisher=Harold Shaw Publishers|location=Wheaton, Illinois|year=1970|page=49|isbn=0-87788-144-8}}</ref>