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[[Image:Gas_giants.jpg|right|thumb|200px|The gas giants outer planets (Jupiter, Saturn, Uranus, Neptune) have reducing atmospheres]]
A '''reducing atmosphere''', also known as a '''reduction atmosphere''', is an [[atmosphere]] without significant amounts of free [[oxygen]] (O<sub>2</sub>) and other oxidising gases or vapours thus preventing [[oxidation]].<ref name=how>{{cite book|author=Dembski, William A.; Wells, Jonathan|title=How to Be an Intellectually Fulfilled Atheist (or not)|publisher=ISI Books|location=Wilmington, Delaware|year=2008|page=18|isbn=978-1-933859-84-2}}</ref> [[chemistry|Chemists]] refer to an atmosphere with abundance of [[hydrogen]] atoms, or other substances that readily provides [[electrons]], and a scarcity of oxygen and [[nitrogen]] atoms as "reduced".<ref name=shapiro>{{cite book|author=Shapiro, Robert|title=Origins: A Skeptic's Guide to the Creation of Life on Earth|publisher=Bantam Books|location=Toronto|year=1987|page=65|isbn=0-553-34355-6}}</ref> A reducing atmosphere contains reductants, or molecules saturated with hydrogen atoms, such as [[ammonia]] (NH<sub>3</sub>) and [[methane]] (CH<sub>4</sub>), which are able to reduce other molecules. So [[carbon]], for example, appears in its most reduced form (CH<sub>4</sub>) but not in an oxidized form (CO) or a fully oxidized form (CO<sub>2</sub>). The discussion of the degree of oxidation of [[Earth]]'s early atmosphere is one of the fundamental topics of the [[origin of life]] models.
==The primitive atmosphere==
[[File:Miller-Urey.png|thumb|200px|Picture of [[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>
Nowadays there is almost universal agreement among specialists that the primitive atmosphere contained no reducing gases like methane, ammonia or hydrogen.<ref name=bydesign>{{cite book|author=Sarfati, Jonathan|authorlink=Jonathan Sarfati|title=[[By Design]]:Evidence for Nature's Intelligent Designer - the God of the Bible|publisher=Creation Book Publishers|location=Powder Springs, GA|year=2008|isbn=978-0-94990672-4}}</ref> Instead, it is that the atmosphere contained [[carbon dioxide]] and nitrogen.<ref name=bydesign /> According [[Hubert Yockey]], the modern view regarding the atmosphere of the early Earth is that it was neutral and composed of nitrogen (N<sub>2</sub>), carbon dioxide (CO<sub>2</sub>), water (H<sub>2</sub>O) and maybe some ammonia (NH<sub>3</sub>).<ref>{{cite book|author=Yockey, Hubert P|authorlink=Hubert Yockey|title=Information Theory, Evolution, and the Origin of Life|publisher=Cambridge University Press|location=Cambridge|year=2005|page=146|isbn=978-0-521-80293-2}}</ref>
An atmosphere without oxygen carries some difficulties regarding the problem of the origin of life. [[Michael Denton]] points out that with an atmosphere without oxygen there would be no ozone layer in the upper atmosphere and the ultraviolet flux reaching the Earth would be sufficient to break down organic compounds as rapidly as they were produced.<ref>{{cite book|author=Denton, Michael|authorlink=Michael Denton|title=[[Evolution: A Theory in Crisis]]|page=261|publisher=Adler & Adler|location=Chevy Chase, MD|year=1985|isbn=0-917561-52-X}}</ref> Some scientists latterly, (e.g. R. T. Brickmann and J. H. Carver) believe that the earth´s primordial atmosphere was not so strongly reducing and probably contained some amount of oxygen produced by photodissociation of water.<ref name=overman>{{cite book |author=Overman, Dean L|authorlink=Dean L. Overman |editor-last= |title=[[A Case Against Accident and Self-Organization]]|publisher=Rowman & Littlefield Publishers|location=Lanham|year=1997|page=41-42|isbn=0-8476-8966-2}}</ref>
==References==
{{reflist}}
==See also==
* [[Spontaneous generation]]
* [[Abiogenesis and ozone]]
* [[Earth's early atmosphere had abundant oxygen (Talk.Origins)|Earth's early atmosphere had abundant oxygen]] Response to Talk.Origins
* [[Earth's early atmosphere had no reducing gases (Talk.Origins)|Earth's early atmosphere had no reducing gases]] Response to Talk.Origins
==External links==
* [http://www.icr.org/article/203/ Did the Early Earth Have a Reducing Atmosphere?] by [[Steven A. Austin]], Ph.D.
* [http://www.bestbiblescience.org/ol1.htm Origin of Life: the Early Atmosphere]
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[[Category:Geochronology]]
[[Category:chemistry]]
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