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| [[Image:BlueMarble-2001-2002.jpg|thumb|300px|Water covers about 75% of the Earth's surface]]
| | Greetings! I am Myrtle Shroyer. California is our birth place. Bookkeeping is what I do. Playing baseball is the hobby he will by no means quit doing.<br><br>Feel free to surf to my website - std testing at home ([http://www.hotporn123.com/user/RPocock please click the up coming document]) |
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| The '''origin of water on Earth''', or the reason that there is clearly more [[water]] on the Earth than on the other planets of the [[Solar System]], has not been clarified. There are several acknowledged theories as to how the world's [[ocean]]s were formed over the past [[History of Earth|4.6 billion years]].
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| == Origins ==
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| {{Unreferenced section|date=August 2013}}
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| Some of the most likely contributory factors to the origin of the [[Earth]]'s oceans are as follows:
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| *The cooling down of the [[Hadean|primordial]] world to the point where the [[Outgassing|outgassed]] volatile components were held in an [[Earth's atmosphere|atmosphere]] of sufficient [[Atmospheric pressure|pressure]] for the stabilization and retention of liquid water.
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| *[[Comet]]s, [[trans-Neptunian object]]s or water-rich [[meteoroid]]s ([[protoplanet]]s) from the outer reaches of the main [[asteroid belt]] colliding with the Earth may have brought water to the world's oceans. Measurements of the ratio of the [[hydrogen]] [[isotope]]s [[deuterium]] and [[hydrogen-1|protium]] point to [[asteroid]]s, since similar percentage impurities in carbon-rich [[chondrites]] were found in oceanic water, whereas previous measurement of the isotopes' concentrations in comets and trans-Neptunian objects correspond only slightly to water on the Earth.
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| *Biochemically through [[Mineralization (geology)|mineralization]] and [[photosynthesis]].{{Citation needed|reason=It is common knowledge that photosynthesis doesn't create water, and to my knowledge, mineralization neither.|date=February 2013}}
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| *Gradual leakage of water stored in [[Hydrate|hydrous]] [[mineral]]s of the Earth's [[Rock (geology)|rocks]].
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| *[[Photodissociation|Photolysis]]: [[radiation]] can break down chemical bonds on the surface.
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| == Water in the development of the Earth ==
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| {{See also|Planetary differentiation}}
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| A sizeable quantity of water would have been in the material which formed the Earth.<ref name="source_mrk1"/><ref name="source_mrk2"/> Water molecules would have escaped Earth's gravity more easily when it was less [[mass]]ive during its formation. Hydrogen and helium are expected to continually leak from the atmosphere, but the lack of denser [[noble gas]]es in the modern atmosphere suggests that something disastrous happened to the early atmosphere.
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| Part of the young planet is theorized to have been disrupted by the [[giant impact hypothesis|impact which created the Moon]], which should have caused melting of one or two large areas. Present composition does not match complete melting and it is hard to completely melt and mix huge rock masses.<ref>{{cite web|url=http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=446 |title=Solar System Exploration: Science & Technology: Science Features: View Feature |publisher=Solarsystem.nasa.gov |date=2004-04-26 |accessdate=2009-08-20}}</ref> However, a fair fraction of material should have been vaporized by this impact, creating a rock-vapor atmosphere around the young planet. The rock-vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a heavy [[carbon dioxide]] atmosphere with hydrogen and [[water vapor]]. Liquid water oceans existed despite the surface temperature of 230°C because of the atmospheric pressure of the heavy CO<sub>2</sub> atmosphere. As cooling continued, [[subduction]] and dissolving in ocean water removed most CO<sub>2</sub> from the atmosphere but levels oscillated wildly as new surface and [[Mantle (geology)|mantle]] cycles appeared.<ref>{{cite web|author=N. H. Sleep*,†, K. Zahnle‡, and P. S. Neuhoff§ |url=http://www.pnas.org/cgi/content/full/98/7/3666 |title=Inaugural Article: Initiation of clement surface conditions on the earliest Earth - Sleep et al. 98 (7): 3666 - Proceedings of the National Academy of Sciences |publisher=Pnas.org |date= |accessdate=2009-08-20}}</ref>
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| Study of [[zircon]]s has found that liquid water must have existed as long ago as 4.4 [[Year#SI_prefix_multipliers|Ga]], very soon after the formation of the Earth.<ref>{{cite web|url=http://wwwrses.anu.edu.au/admin/index.php?p=harrison |title=ANU - Research School of Earth Sciences - ANU College of Science - Harrison |publisher=Ses.anu.edu.au |date= |accessdate=2009-08-20}}</ref><ref>{{cite web|url=http://info.anu.edu.au/mac/Media/Media_Releases/_2005/_November/_181105harrisoncontinents.asp |title=ANU - OVC - MEDIA - MEDIA RELEASES - 2005 - NOVEMBER - 181105HARRISONCONTINENTS |publisher=Info.anu.edu.au |date= |accessdate=2009-08-20}}</ref><ref>{{cite web|url=http://www.geology.wisc.edu/%7Evalley/zircons/cool_early/cool_early_home.html |title=A Cool Early Earth |publisher=Geology.wisc.edu |date= |accessdate=2009-08-20}}</ref> This requires the presence of an atmosphere. The [[Cool Early Earth]] theory covers a range from about 4.4 Ga to 4.0 Ga.
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| In fact, recent studies of zircons (in the fall of 2008) found in Australian Hadean rock hold minerals that point to the existence of [[plate tectonics]] as early as 4 billion years ago. If this holds true, the previous beliefs about the [[Hadean|Hadean period]] are far from correct. That is, rather than a hot, molten surface and atmosphere full of carbon dioxide, the Earth's surface would be very much like it is today. The action of plate tectonics traps vast amounts of carbon dioxide, thereby eliminating the greenhouse effects and leading to a much cooler surface temperature and the formation of solid rock, and possibly even life.<ref>{{cite news| url=http://www.nytimes.com/2008/12/02/science/02eart.html?8dpc | work=The New York Times | title=A New Picture of the Early Earth | first=Kenneth | last=Chang | date=2008-12-02 | accessdate=2010-05-20}}</ref>
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| == Extraterrestrial sources ==
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| That the Earth's water originated purely from comets is implausible, as a result of measurements of the isotope ratios of hydrogen in the three comets [[Halley's Comet|Halley]], [[Hyakutake]] and [[Hale-Bopp]] by researchers like [[David Jewitt]], as according to this research the ratio of [[deuterium]] to [[hydrogen-1|protium]] (D/H ratio) of the comets is approximately double that of oceanic water. What is however unclear is whether these comets are representative of those from the [[Kuiper Belt]]. According to A. Morbidelli <ref>A. Morbidelli et al. [[Meteoritics & Planetary Science]] 35, 2000, S. 1309–1329</ref> the largest part of today's water comes from protoplanets formed in the outer asteroid belt that plunged towards the Earth, as indicated by the D/H proportions in carbon-rich chondrites. The water in carbon-rich chondrites point to a similar D/H ratio as oceanic water. Nevertheless, mechanisms have been proposed<ref>H. Genda, M. Ikoma, Origin of the Ocean on the Earth: Early Evolution of Water D/H in a Hydrogen-rich Atmosphere. Accessible at http://arxiv.org/abs/0709.2025</ref> to suggest that the D/H-ratio of oceanic water may have increased significantly throughout Earth's history. Such a proposal is consistent with the possibility that a significant amount of the water on Earth was already present during the planet's early evolution.
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| == Role of organisms ==
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| In the early 1930s [[Cornelis Van Niel]] discovered that sulfide-dependent chemoautotrophic bacteria ([[purple sulfur bacteria]]) fix carbon and synthesize water as a byproduct of a photosynthetic pathway using [[hydrogen sulfide]] and carbon dioxide:<ref>{{cite journal|last=van Niel|first=C.B.|title=Photosynthesis of bacteria|journal=Arch. Mikrobiol.|year=1931|volume=3|issue=1}}</ref>
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| <math> \mathrm{ CO_2 + 2\ H_2S \rightarrow CH_2O + H_2O + 2\ S }</math>
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| Few organisms utilize this method of photosynthesis today, making their water contribution negligible. But on the [[hydrogen sulfide]]-rich and oxygen-poor early planet, a small but significant portion of the earth's water may have been synthesized biochemically through this pathway.{{Citation needed|date=June 2011}}
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| == Seeds of Life in Asteroids ==
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| Researchers have proposed a new and improved theory to explain how biomolecules were once able to form inside of asteroids. These researchers at Renesselaer Polytechnic Institute theory aim to explain the ancient heating of the asteroid belt. The asteroid belt is located between Mars and Jupiter. Although it is now cold and dry in the past years scientists have concluded that at one point it had wet and warm conditions that would cater to the formation of biomolecules. Biomolecules were found inside of the meteorites which were originated in the asteroid belt. To figure this out two researchers Wayne Roberge and Ray Menzel examined two theories about how asteroids could have been heated in the young solar system. The first theory involved the same radioactive process that is used to describe how the Earth is heated. The second theory involved the interaction between plasma and the magnetic field. Some of today’s models of radioactive heating do help with making predictions that temperatures in the asteroid belt are inconsistent with observations. This piece of information motivated Roberge and Mendel to take further look into the second theory. This theory discusses the early assessment of the sun and the suggestion that an object moving through the magnetic field of the solar system will experience an electric field. This electric field will then push electric currents through the asteroid. The asteroid will then be heated, similar to electric current heating the wires in a toaster. To go deeper in their research Mendel and Roberge had to calculate the electric field everywhere. They calculated the electric field in the interior of the asteroid. By doing this research with the electric field they concluded that the asteroids would have experienced the solar wind, plasma conditions and multi-fluid magneto-hydrodynamics. In multi-fluid magneto-hydrodynamics plasma is very weakly ionized and neutral particles behave distinctly from the charged particles. The neutral particles will interact with charged particles by friction. This creates a problem of treating the dynamics of the neutral gas and allowing for the presence of the small number of charged particles interacting with the magnetic field. Although this theory is promising it raises many questions that will have to be further examined. Roberge and Mendel feel as though they have discovered new information and look forward to more exploration of this theory.
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| <ref>Rensselaer Polytechnic Institute (2013, October 1). Researchers propose new theory to explain seeds of life in asteroids. ScienceDaily. Retrieved October 31, 2013, from http://www.sciencedaily.com /releases/2013/10/131001151132.htm</ref>
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| == See also ==
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| {{Portal|Astronomy}}
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| * [[Water on terrestrial planets]]
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| == Notes ==
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| {{Refbegin}}
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| * Jörn Müller, Harald Lesch (2003): Woher kommt das Wasser der Erde? - Urgaswolke oder Meteoriten. Chemie in unserer Zeit 37(4), pg. 242 – 246, ISSN 0009-2851
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| * Parts of this article were translated from the [[:de:Herkunft des irdischen Wassers|original article]] from the [[German Wikipedia]], on 4/3/06
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| {{Refend}}
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| ==References==
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| {{reflist|30em|refs=
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| <ref name="source_mrk1">{{cite journal | title= Origin of water in the terrestrial planets | last1= Drake | first1= Michael J. | journal=Meteoritics & Planetary Science |date=April 2005 | publisher= John Wiley & Sons | volume=40 |issue= 4 |pages= 519–527 |doi= 10.1111/j.1945-5100.2005.tb00960.x | bibcode= 2005M&PS...40..519D}}</ref>
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| <ref name="source_mrk2">{{cite conference | url= http://journals.cambridge.org/action/displayFulltext?type=6&fid=415222&jid=IAU&volumeId=1&issueId=S229&aid=414784&bodyId=&membershipNumber=&societyETOCSession=&fulltextType=RA&fileId=S1743921305006861 | title= Origin of water in the terrestrial planets | display-authors=1 | last1= Drake | first1= Michael J. | authorlink1= | last2= Humberto | first2= Campins | authorlink2= | conference = 229th Symposium of the International Astronomical Union |date=August 2005 | location = Búzios, Rio de Janeiro, Brazil | publisher= Cambridge University Press | volume=1 |issue= 4 |pages= 381–394 |doi= 10.1017/S1743921305006861 | bibcode= 2006IAUS..229..381D | booktitle= Asteroids, Comets, and Meteors (IAU S229) | isbn= 978-0521852005}}</ref>
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| }}
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| ==External links==
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| * [http://www.oceansonline.com/ocean_form.htm Dr. C's Oceans Online website] ([http://web.archive.org/web/20050311220523/http://www.oceansonline.com/ocean_form.htm archived copy])
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| * [http://www.universetoday.com/am/publish/comets_create_earth_oceans.html?1662004 UniverseToday.com]
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| {{Water}}
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| {{DEFAULTSORT:Origin Of Water On Earth}}
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| [[Category:Earth]]
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| [[Category:Hadean]]
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| [[Category:Water]]
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| [[Category:Scientific problems]]
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Greetings! I am Myrtle Shroyer. California is our birth place. Bookkeeping is what I do. Playing baseball is the hobby he will by no means quit doing.
Feel free to surf to my website - std testing at home (please click the up coming document)