Editing Plate tectonics (section)

== Other celestial bodies ==
The appearance of plate tectonics on [[terrestrial planet]]s is related to planetary mass, with [[super-Earth|more massive planets than Earth]] expected to exhibit plate tectonics. Earth may be a borderline case, owing its tectonic activity to abundant water (silica and water form a deep [[eutectic]]).{{sfn|Valencia|O'Connell|Sasselov|2007}}

=== Venus ===
{{See also|Geology of Venus}}
Venus shows no evidence of active plate tectonics. There is debatable evidence of active tectonics in the planet's distant past; however, events taking place since then (such as the plausible and generally accepted hypothesis that the Venusian [[lithosphere]] has thickened greatly over the course of several hundred million years) has made constraining the course of its geologic record difficult. However, the numerous well-preserved [[impact crater]]s have been used as a [[dating methods|dating method]] to approximately date the Venusian surface (since there are thus far no known samples of Venusian rock to be dated by more reliable methods). Dates derived are dominantly in the range {{Ma|500|750}}, although ages of up to {{Ma|1200}} have been calculated. This research has led to the fairly well accepted hypothesis that Venus has undergone an essentially complete volcanic resurfacing at least once in its distant past, with the last event taking place approximately within the range of estimated surface ages. While the mechanism of such an impressive thermal event remains a debated issue in Venusian geosciences, some scientists are advocates of processes involving plate motion to some extent.

One explanation for Venus's lack of plate tectonics is that on Venus temperatures are too high for significant water to be present.{{sfn|Kasting|1988}}<ref>{{Cite web |last=Bortman |first=Henry |date=2004-08-26 |title=Was Venus alive? 'The Signs are Probably There' |url=http://www.space.com/scienceastronomy/venus_life_040826.html |url-status=live |archive-url=https://web.archive.org/web/20101224055407/http://www.space.com/scienceastronomy/venus_life_040826.html |archive-date=2010-12-24 |access-date=2008-01-08 |website=Space.com}}</ref> Earth's crust is soaked with water, and water plays an important role in the development of [[shear zone]]s. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers<ref>{{cite journal|author1=Weller, M.B.|author2= Evans, A.J.|author3= Ibarra, D.E.|title= Venus's atmospheric nitrogen explained by ancient plate tectonics|journal= Nat Astron|volume= 7|pages=1436–1444|year=2023|issue= 12|doi= 10.1038/s41550-023-02102-w|bibcode= 2023NatAs...7.1436W|url= https://doi.org/10.1038/s41550-023-02102-w}}</ref> remain convinced that plate tectonics is or was once active on this planet.

=== Mars ===
{{See also|Geology of Mars}}
Mars is considerably smaller than Earth and Venus, and there is evidence for ice on its surface and in its crust.

In the 1990s, it was proposed that [[Martian dichotomy|Martian Crustal Dichotomy]] was created by plate tectonic processes.{{sfn|Sleep|1994}} Scientists have since determined that it was created either by upwelling within the Martian [[mantle (geology)|mantle]] that thickened the crust of the Southern Highlands and formed [[Tharsis]]{{sfn|Zhong|Zuber|2001}} or by a giant impact that excavated the [[Vastitas Borealis|Northern Lowlands]].{{sfn|Andrews-Hanna|Zuber|Banerdt|2008}}

[[Valles Marineris]] may be a tectonic boundary.<ref name="tectonic">{{Cite web |last=Wolpert, Stuart |date=August 9, 2012 |title=UCLA scientist discovers plate tectonics on Mars |url=http://newsroom.ucla.edu/portal/ucla/ucla-scientist-discovers-plate-237303.aspx?link_page_rss=237303 |url-status=dead |archive-url=https://web.archive.org/web/20120814232327/http://newsroom.ucla.edu/portal/ucla/ucla-scientist-discovers-plate-237303.aspx?link_page_rss=237303 |archive-date=August 14, 2012 |access-date=August 13, 2012 |website=Yin, An |publisher=[[UCLA]]}}</ref>

Observations made of the magnetic field of Mars by the ''[[Mars Global Surveyor]]'' spacecraft in 1999 showed patterns of magnetic striping discovered on this planet. Some scientists interpreted these as requiring plate tectonic processes, such as seafloor spreading.<ref>{{Harvnb|Connerney|Acuña|Wasilewski|Ness|1999}}, {{Harvnb|Connerney|Acuña|Ness|Kletetschka|2005}}</ref> However, their data failed a "magnetic reversal test", which is used to see if they were formed by flipping polarities of a global magnetic field.{{sfn|Harrison|2000}}

=== Icy moons ===
{{excerpt|Tectonics on icy moons|Plate tectonics}}

=== Exoplanets ===
On Earth-sized planets, plate tectonics is more likely if there are oceans of water. However, in 2007, two independent teams of researchers came to opposing conclusions about the likelihood of plate tectonics on larger [[super-Earth]]s<ref>{{Cite journal |last1=Valencia |first1=Diana |last2=O'Connell |first2=Richard J. |year=2009 |title=Convection scaling and subduction on Earth and super-Earths |journal=[[Earth and Planetary Science Letters]] |volume=286 |issue=3–4 |pages=492–502 |bibcode=2009E&PSL.286..492V |doi=10.1016/j.epsl.2009.07.015}}</ref><ref>{{Cite journal |last1=van Heck |first1=H.J. |last2=Tackley |first2=P.J. |year=2011 |title=Plate tectonics on super-Earths: Equally or more likely than on Earth |journal=[[Earth and Planetary Science Letters]] |volume=310 |issue=3–4 |pages=252–61 |bibcode=2011E&PSL.310..252V |doi=10.1016/j.epsl.2011.07.029}}</ref> with one team saying that plate tectonics would be episodic or stagnant<ref>{{Cite journal |last1=O'Neill |first1=C. |last2=Lenardic |first2=A. |year=2007 |title=Geological consequences of super-sized Earths |journal=[[Geophysical Research Letters]] |volume=34 |issue=19 |page=L19204 |bibcode=2007GeoRL..3419204O |doi=10.1029/2007GL030598 |doi-access=free}}</ref> and the other team saying that plate tectonics is very likely on super-earths even if the planet is dry.{{sfn|Valencia|O'Connell|Sasselov|2007}}

Consideration of plate tectonics is a part of the [[search for extraterrestrial intelligence]] and [[extraterrestrial life]].<ref>{{Cite journal |last=Stern |first=Robert J. |date=July 2016 |title=Is plate tectonics needed to evolve technological species on exoplanets? |journal=[[Geoscience Frontiers]] |volume=7 |issue=4 |pages=573–580 |bibcode=2016GeoFr...7..573S |doi=10.1016/j.gsf.2015.12.002 |doi-access=free}}</ref>