Editing Planet (section)

==== Internal differentiation ====
{{Main|Planetary differentiation}}
[[File:Jupiter interior.png|upright|thumb|Illustration of the interior of Jupiter, with a rocky core overlaid by a deep layer of metallic hydrogen]]

Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a [[Planetary differentiation|differentiated]] interior consisting of a dense [[planetary core]] surrounded by a [[Mantle (geology)|mantle]] that either is or was a [[fluid]]. The terrestrial planets' mantles are sealed within hard [[Crust (geology)|crusts]],<ref name="terrestrial">{{cite web |title=Planetary Interiors |work=Department of Physics, University of Oregon |url=http://abyss.uoregon.edu/~js/ast121/lectures/lec16.html |access-date=23 August 2008 |archive-date=8 August 2012 |archive-url=https://web.archive.org/web/20120808155809/http://abyss.uoregon.edu/~js/ast121/lectures/lec16.html |url-status=dead }}</ref> but in the giant planets the mantle simply blends into the upper cloud layers. The terrestrial planets have cores of elements such as [[iron]] and [[nickel]] and mantles of [[silicate]]s. Jupiter and Saturn are believed to have cores of rock and metal surrounded by mantles of [[metallic hydrogen]].<ref>{{cite book | first=Linda T. |last=Elkins-Tanton |date=2006 |title=Jupiter and Saturn |publisher=Chelsea House |location=New York |isbn=978-0-8160-5196-0}}</ref> Uranus and Neptune, which are smaller, have rocky cores surrounded by mantles of water, [[ammonia]], [[methane]], and other [[Volatile (astrogeology)|ices]].<ref>{{cite journal| doi = 10.1016/0032-0633(95)00061-5| last1 = Podolak| first1 = M.| last2 = Weizman| first2 = A.| last3 = Marley| first3 = M.| date=December 1995 | title = Comparative models of Uranus and Neptune| journal = Planetary and Space Science| volume = 43| issue = 12| pages = 1517–1522| bibcode = 1995P&SS...43.1517P| ref = {{sfnRef|Podolak Weizman et al.|1995}}}}</ref> The fluid action within these planets' cores creates a [[geodynamo]] that generates a [[magnetic field]].<ref name="terrestrial" /> Similar differentiation processes are believed to have occurred on some of the large moons and dwarf planets,<ref name=Grundy2019/> though the process may not always have been completed: Ceres, Callisto, and Titan appear to be incompletely differentiated.<ref name="Neumann2015">{{Cite journal |last1=Neumann |first1=W. |last2=Breuer |first2=D. |last3=Spohn |first3=T. |date=2 December 2015 |title=Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation |url=http://www.aanda.org/articles/aa/pdf/2015/12/aa27083-15.pdf |url-status=live |journal=Astronomy & Astrophysics |volume=584 |page=A117 |bibcode=2015A&A...584A.117N |doi=10.1051/0004-6361/201527083 |archive-url=https://web.archive.org/web/20160822053141/http://www.aanda.org/articles/aa/pdf/2015/12/aa27083-15.pdf |archive-date=22 August 2016 |access-date=10 July 2016 |doi-access=free}}</ref><ref name=Monteux2014>{{cite journal |last1=Monteux |first1=J. |last2=Tobie |first2=G. |last3=Choblet |first3=G. |last4=Le Feuvre |first4=M. |title=Can large icy moons accrete undifferentiated? |journal=Icarus |year=2014 |volume=237 |pages=377–387 |doi=10.1016/j.icarus.2014.04.041 |bibcode=2014Icar..237..377M |s2cid=46172826 |url=https://hal.uca.fr/hal-01636068/file/Monteux-Icarus-V3-1-Final-2014.pdf |access-date=6 August 2022 |archive-date=9 October 2022 |archive-url=https://ghostarchive.org/archive/20221009/https://hal.uca.fr/hal-01636068/file/Monteux-Icarus-V3-1-Final-2014.pdf |url-status=live }}</ref> The asteroid Vesta, though not a dwarf planet because it was battered by impacts out of roundness, has a differentiated interior<ref name=Vestainterior>{{cite web|title=A look into Vesta's interior|url=https://www.mpg.de/877913/Vesta_asteroid|work=Max-Planck-Gesellschaft|date=6 January 2011|access-date=7 May 2023|archive-date=5 March 2023|archive-url=https://web.archive.org/web/20230305200352/https://www.mpg.de/877913/Vesta_asteroid|url-status=live}}</ref> similar to that of Venus, Earth, and Mars.<ref name=Asphaug-Reufer-2014/>