Atmósfera reductora
Una atmósfera reductora es una atmósfera, sin cantidades significativas de oxígeno libre (O2) y otros gases o vapores oxidantes evitando de este modo la oxidación.[1] Los químicos se refieren a una atmósfera con abundancia de átomos de hidrógeno, u otras sustancias que proporcionan fácilmente electrones, y una escasez de átomos de oxígeno y nitrógeno como "reductora".[2] Una atmósfera reductora contiene reductores, o moléculas saturadas con átomos de hidrógeno, tales como amonio (NH3) y metano (CH4), que son capaces de reducir otras moléculas. Así el carbono, por ejemplo, aparece en su forma más reducida (CH4) pero no en una forma oxidada (CO) o una forma completamente oxidada (CO2). El debate sobre el grado de oxidación de la atmósfera primitiva de la Tierra es uno de los temas fundamentales de los modelos de la origen de la vida.
La atmósfera primitiva
Las teorías sobre el origen de la vida inicialmente asumieron que la atmósfera primitiva debería ser una reductora con el fin de prevenir la destrucción oxidativa de los componentes de la "sopa primordial".[3] So the evolutionists theorize an early atmosphere without oxygen. Oparin believed that the Earth's early atmosphere was composed of hydrogen (H2), methane (CH4), ammonia (NH3) and water vapor (H2O), containing no oxygen.[1] Haldane postulated the same theory and his most important conclusions were presented in a short article for the Rationalist Annual.[4] Other scientists who corroborated this model of atmosphere were Miller and Urey. They reasoned that a small but significant amount of H2 remained in the primordial atmosphere and reacted with atoms of carbon, nitrogen or oxigen forming this kind of atmosphere.[5] By sparking together hydrogen, methane, ammonia, and water vapor, they produced several amino acids, the building blocks of organic life.[6]
Nowadays there is almost universal agreement among specialists that the primitive atmosphere contained no reducing gases like methane, ammonia or hydrogen.[7] Instead, it is that the atmosphere contained carbon dioxide and nitrogen.[7] According Hubert Yockey, the modern view regarding the atmosphere of the early Earth is that it was neutral and composed of nitrogen (N2), carbon dioxide (CO2), water (H2O) and maybe some ammonia (NH3).[8]
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.[9] 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.[10]
Referencias
- ↑ 1,0 1,1 Dembski, William A.; Wells, Jonathan (2008). How to Be an Intellectually Fulfilled Atheist (or not). Wilmington, Delaware: ISI Books. p. 18. ISBN 978-1-933859-84-2.
- ↑ Shapiro, Robert (1987). Origins: A Skeptic's Guide to the Creation of Life on Earth. Toronto: Bantam Books. p. 65. ISBN 0-553-34355-6.
- ↑ Aw, S. E (1982). Chemical Evolution. San Diego, California: Master Books. ISBN 0-89051-082-2.
- ↑ Plantilla:Cite book
- ↑ Plantilla:Cite book
- ↑ Plantilla:Cite book
- ↑ 7,0 7,1 Plantilla:Cite book
- ↑ Plantilla:Cite book
- ↑ Plantilla:Cite book
- ↑ Plantilla:Cite book
See also
- Spontaneous generation
- Abiogenesis and ozone
- Earth's early atmosphere had abundant oxygen Response to Talk.Origins
- Earth's early atmosphere had no reducing gases Response to Talk.Origins
Enlaces externos
- Did the Early Earth Have a Reducing Atmosphere? by Steven A. Austin, Ph.D.
- Origin of Life: the Early Atmosphere
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