Editing Plate tectonics (section)

=== 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}}