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{{#invoke:sidebar|sidebar |bodyclass = plainlist |bodystyle = width:auto; |topimagestyle = background:#ddeffa;padding:0.5em 1.0em; |topimage = View of the Earth where all five oceans visible |title = Earth's oceans |content1 =

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World Ocean

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An ocean (from grc Ὠκεανός, transc. Okeanós, the sea of classical antiquity<ref name="tufts.pers">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>) is a body of saline water that composes much of a planet's hydrosphere.<ref name="pri.ocean">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> On Earth, an ocean is one of the major conventional divisions of the World Ocean, which covers almost 71% of its surface. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.<ref name="oed.130201">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="mw.ocean">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The word sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land.<ref name="pri.sea">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Saline water covers approximately 72% of the planet's surface (~3.6×10{{#invoke:Gapnum|main|8}} km2) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface.<ref name="noaa.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The ocean contains 97% of Earth's water, and oceanographers have stated that only 5% of the World Ocean has been explored.<ref name="noaa.gov" /> The total volume is approximately 1.35 billion cubic kilometers (320 million cu mi)<ref name="hypertextbook2003">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> with an average depth of nearly {{safesubst:#invoke:convert|convert}}.<ref name="Charette_Smith_Ocean-depth">{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref><ref name="NOAA" />

As it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. It is the habitat of 230,000 known species, although much of the oceans depths remain unexplored, and over two million marine species are estimated to exist.<ref name="la.2009">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> The origin of Earth's oceans remains unknown; oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life.

Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.<ref name="mindblowingscience">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="sciencedaily">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>


Ocean sections
Intro   Earth's global ocean    Extraterrestrial oceans    See also    References    Further reading    External links   

PREVIOUS: IntroNEXT: Earth's global ocean
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First::ocean    Title::water    Ocean::oceans    Journal::surface    Volume::planet    Their::align

{{#invoke:Pp-move-indef|main}} {{#invoke:Hatnote|hatnote}}

{{#invoke:sidebar|sidebar |bodyclass = plainlist |bodystyle = width:auto; |topimagestyle = background:#ddeffa;padding:0.5em 1.0em; |topimage = View of the Earth where all five oceans visible |title = Earth's oceans |content1 =

|belowstyle = font-weight:normal;

|below =
World Ocean

}}

An ocean (from grc Ὠκεανός, transc. Okeanós, the sea of classical antiquity<ref name="tufts.pers">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>) is a body of saline water that composes much of a planet's hydrosphere.<ref name="pri.ocean">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> On Earth, an ocean is one of the major conventional divisions of the World Ocean, which covers almost 71% of its surface. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.<ref name="oed.130201">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="mw.ocean">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The word sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land.<ref name="pri.sea">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Saline water covers approximately 72% of the planet's surface (~3.6×10{{#invoke:Gapnum|main|8}} km2) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface.<ref name="noaa.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The ocean contains 97% of Earth's water, and oceanographers have stated that only 5% of the World Ocean has been explored.<ref name="noaa.gov" /> The total volume is approximately 1.35 billion cubic kilometers (320 million cu mi)<ref name="hypertextbook2003">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> with an average depth of nearly {{safesubst:#invoke:convert|convert}}.<ref name="Charette_Smith_Ocean-depth">{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref><ref name="NOAA" />

As it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. It is the habitat of 230,000 known species, although much of the oceans depths remain unexplored, and over two million marine species are estimated to exist.<ref name="la.2009">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> The origin of Earth's oceans remains unknown; oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life.

Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.<ref name="mindblowingscience">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="sciencedaily">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>


Ocean sections
Intro   Earth's global ocean    Extraterrestrial oceans    See also    References    Further reading    External links   

PREVIOUS: IntroNEXT: Earth's global ocean
<<>>