Editing Pluto (section)

== Rotation ==
[[file:Pluto rotation movie2.gif|thumb|Rotation movie of Pluto based on images from NASA's ''New Horizons'']]
Pluto's [[rotation period]], its day, is equal to 6.387 [[Earth]] days.<ref name="Pluto Fact Sheet" /><ref name="axis" /> Like [[Uranus]] and [[2 Pallas]], Pluto rotates on its "side" in its orbital plane, with an axial tilt of 120°, and so its seasonal variation is extreme; at its [[solstice]]s, one-fourth of its surface is in continuous daylight, whereas another fourth is in continuous darkness.<ref name="Oregon" /> The reason for this unusual orientation has been debated. Research from the [[University of Arizona]] has suggested that it may be due to the way that a body's spin will always adjust to minimize energy. This could mean a body reorienting itself to put extraneous mass near the equator and regions lacking mass tend towards the poles. This is called ''[[polar wander]]''.<ref>{{Cite journal|last1=Kirschvink|first1=Joseph L.|last2=Ripperdan|first2=Robert L.|last3=Evans|first3=David A.|date=July 25, 1997|title=Evidence for a Large-Scale Reorganization of Early Cambrian Continental Masses by Inertial Interchange True Polar Wander|journal=Science|language=en|volume=277|issue=5325|pages=541–545|doi=10.1126/science.277.5325.541|s2cid=177135895|issn=0036-8075}}</ref> According to a paper released from the University of Arizona, this could be caused by masses of frozen nitrogen building up in shadowed areas of the dwarf planet. These masses would cause the body to reorient itself, leading to its unusual axial tilt of 120°. The buildup of nitrogen is due to Pluto's vast distance from the Sun. At the equator, temperatures can drop to {{convert|-240|C|F K}}, causing nitrogen to freeze as water would freeze on Earth. The same polar wandering effect seen on Pluto would be observed on Earth were the [[Antarctic ice sheet]] several times larger.<ref>{{Cite journal|last1=Keane|first1=James T.|last2=Matsuyama|first2=Isamu|last3=Kamata|first3=Shunichi|last4=Steckloff|first4=Jordan K.|title=Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia|journal=Nature|volume=540|issue=7631|pages=90–93|doi=10.1038/nature20120|pmid=27851731|bibcode = 2016Natur.540...90K |year=2016|s2cid=4468636}}</ref>