Changes

#The first atmosphere consisted of gases in the [[solar nebula]], mainly [[hydrogen]]. There might also have been simple [[hydride]]s such as those now found in the [[gas giant]]s ([[Jupiter]] and [[Saturn]]): [[water vapor]], [[methane]] and [[ammonia]].<ref name=Zahnle>{{Cite journal |last1=Zahnle |first1=K. |last2=Schaefer |first2=L. |last3=Fegley |first3=B. |doi=10.1101/cshperspect.a004895 |title=Earth's Earliest Atmospheres |journal=Cold Spring Harbor Perspectives in Biology |volume=2 |issue=10 |pages=a004895 |year=2010 |pmid=20573713 |pmc=2944365}}</ref>  

#The first atmosphere consisted of gases in the [[solar nebula]], mainly [[hydrogen]]. There might also have been simple [[hydride]]s such as those now found in the [[gas giant]]s ([[Jupiter]] and [[Saturn]]): [[water vapor]], [[methane]] and [[ammonia]].<ref name=Zahnle>{{Cite journal |last1=Zahnle |first1=K. |last2=Schaefer |first2=L. |last3=Fegley |first3=B. |doi=10.1101/cshperspect.a004895 |title=Earth's Earliest Atmospheres |journal=Cold Spring Harbor Perspectives in Biology |volume=2 |issue=10 |pages=a004895 |year=2010 |pmid=20573713 |pmc=2944365}}</ref>  

#The atmosphere gradually changed to mostly [[carbon dioxide]] and [[nitrogen]]. The lighter gases, like hydrogen and [[helium]], cannot be held by the Earth's [[gravity]], and would escape. For a long time (say two billion years or more), the atmosphere was dominated by carbon dioxide.

#The atmosphere gradually changed to mostly [[carbon dioxide]] and [[nitrogen]]. The lighter gases, like hydrogen and [[helium]], cannot be held by the Earth's [[gravity]], and would escape. For a long time (say two billion years or more), the atmosphere was dominated by carbon dioxide.

#In the [[Great Oxygenation Event]] the atmosphere changed to the kind we have now, with oxygen replacing the carbon dioxide. Our atmosphere is still mostly nitrogen, but most living organisms interact more with oxygen than with nitrogen. Oxygenation began with [[cyanobacteria]] making free oxygen by [[photosynthesis]]. Most organisms today need oxygen for their [[respiration]]: only a few [[anaerobic organism]]<nowiki/>s can grow without oxygen.<ref>Heinrich D. Holland: ''The oxygenation of the atmosphere and oceans.'' In: ''Phil. Trans. R. Soc.'' B, vol. 361, 2006, p. 903–915 http://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf</ref><ref>Knoll, Andrew H. 2004. ''Life on a young planet: the first three billion years of evolution on Earth''. Princeton, N.J. {{ISBN|0-691-12029-3}}</ref>

#In the [[Great Oxygenation Event]] the atmosphere changed to the kind we have now, with oxygen replacing the carbon dioxide. Our atmosphere is still mostly nitrogen, but most living organisms interact more with oxygen than with nitrogen. Oxygenation began with [[cyanobacteria]] making free oxygen by [[photosynthesis]]. Most organisms today need oxygen for their [[respiration]]: only a few [[anaerobic organism]]<nowiki/>s can grow without oxygen.<ref>Heinrich D. Holland: ''The oxygenation of the atmosphere and oceans.'' In: ''Phil. Trans. R. Soc.'' B, vol. 361, 2006, p. 903–915 http://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf {{Webarchive|url=https://web.archive.org/web/20140625153836/http://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf |date=2014-06-25 }}</ref><ref>Knoll, Andrew H. 2004. ''Life on a young planet: the first three billion years of evolution on Earth''. Princeton, N.J. {{ISBN|0-691-12029-3}}</ref>

== Composition ==

== Composition ==

[[File:Atmosphere gas proportions.svg|thumb|Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere.<ref name=Allens-2002>Unless other wise noted, values from {{Cite book |url=https://link.springer.com/10.1007/978-1-4612-1186-0 |title=Allen's Astrophysical Quantities |date=2002 |publisher=Springer New York |isbn=978-1-4612-7037-9 |editor-last=Cox |editor-first=Arthur N. |location=New York, NY |language=en |doi=10.1007/978-1-4612-1186-0}}</ref><ref name=CO2>{{citation |title=Trends in Atmospheric Carbon Dioxide |url=https://www.esrl.noaa.gov/gmd/ccgg/trends/ |website=Global Greenhouse Gas Reference Network, NOAA |year=2019 |access-date=2019-05-31}}</ref><ref name=methane>{{citation |title=Trends in Atmospheric Methane |website=Global Greenhouse Gas Reference Network, NOAA |url=https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/ |year=2019 |access-date=2019-05-31}}</ref>]]

[[File:Atmosphere gas proportions.svg|thumb|Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere.<ref name=Allens-2002>Unless other wise noted, values from {{Cite book |url=https://link.springer.com/10.1007/978-1-4612-1186-0 |title=Allen's Astrophysical Quantities |date=2002 |publisher=Springer New York |isbn=978-1-4612-7037-9 |editor-last=Cox |editor-first=Arthur N. |location=New York, NY |language=en |doi=10.1007/978-1-4612-1186-0}}</ref><ref name=CO2>{{citation |title=Trends in Atmospheric Carbon Dioxide |url=https://www.esrl.noaa.gov/gmd/ccgg/trends/ |website=Global Greenhouse Gas Reference Network, NOAA |year=2019 |access-date=2019-05-31}}</ref><ref name=methane>{{citation |title=Trends in Atmospheric Methane |website=Global Greenhouse Gas Reference Network, NOAA |url=https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/ |year=2019 |access-date=2019-05-31}}</ref>]]

== Atmosphere Of Earth Media ==

== Atmosphere Of Earth Media ==

<gallery widths='160px' heights='100%' mode='traditional' caption=''>

<gallery widths='160px' heights='100%' mode='traditional' caption=''>

File:Earth's atmosphere.svg|A prism cross-section of the Earth's atmosphere. The strata are drawn to scale, but individual features are not.{{rp|322}}

File:Earth's atmosphere.svg|A prism cross-section of the Earth's atmosphere. The strata are drawn to scale, but individual features are not.{{rp|322}}

File:Earth energy budget.svg|The relative absorption, emission and reflection of solar radiation by the atmosphere, clouds and surface

File:Earth energy budget.svg|The relative absorption, emission and reflection of solar radiation by the atmosphere, clouds and surface

File:Watching the Earth Breathe.ogv|Animation shows the buildup of tropospheric {{CO2}} in the Northern Hemisphere with a maximum around May. The maximum in the vegetation cycle follows in the late summer. Following the peak in vegetation, the drawdown of atmospheric {{CO2}} due to photosynthesis is apparent, particularly over the [[boreal forests]].

File:Watching the Earth Breathe.webm|Animation shows the buildup of tropospheric {{CO2}} in the Northern Hemisphere with a maximum around May. The maximum in the vegetation cycle follows in the late summer. Following the peak in vegetation, the drawdown of atmospheric {{CO2}} due to photosynthesis is apparent, particularly over the [[boreal forests]].

</gallery>

</gallery>

== Related pages ==

== Related pages ==