Editing Axial tilt (section)

== Solar System bodies ==
{{see also|Poles of astronomical bodies#Poles of rotation}}[[File:Planets and dwarf planets' tilt and rotation speed.webm|thumb|upright=1.5|Axial tilt of eight [[Planet|planets]] and two dwarf planets, [[Ceres (dwarf planet)|Ceres]] and [[Pluto]]]]
All four of the innermost, rocky planets of the [[Solar System]] may have had large variations of their obliquity in the past. Since obliquity is the angle between the axis of rotation and the direction perpendicular to the orbital plane, it changes as the orbital plane changes due to the influence of other planets. But the axis of rotation can also move ([[axial precession]]), due to torque exerted by the Sun on a planet's equatorial bulge. Like Earth, all of the rocky planets show axial precession. If the precession rate were very fast the obliquity would actually remain fairly constant even as the orbital plane changes.<ref name="Ward">{{cite journal|last1=William Ward|title=Large-Scale Variations in the Obliquity of Mars|journal=Science|volume=181|issue=4096|pages=260–262|date=20 July 1973|doi=10.1126/science.181.4096.260|pmid=17730940|bibcode=1973Sci...181..260W|s2cid=41231503}}</ref> The rate varies due to [[Tidal acceleration|tidal dissipation]] and [[Planetary core|core]]-[[Mantle (geology)|mantle]] interaction, among other things. When a planet's precession rate approaches certain values, [[orbital resonance]]s may cause large changes in obliquity. The amplitude of the contribution having one of the resonant rates is divided by the difference between the resonant rate and the precession rate, so it becomes large when the two are similar.<ref name="Ward" />

[[Mercury (planet)|Mercury]] and [[Venus]] have most likely been stabilized by the tidal dissipation of the Sun. Earth was stabilized by the Moon, as mentioned above, but before its [[Moon#Formation|formation]], Earth, too, could have passed through times of instability. [[Mars]]'s obliquity is quite variable over millions of years and may be in a chaotic state; it varies as much as 0° to 60° over some millions of years, depending on [[Perturbation (astronomy)|perturbations]] of the planets.<ref name="LaskarRobutel" /><ref>
{{cite journal
 |last1=Touma |first1=J.
 |last2=Wisdom |first2=J.
 |date=1993
 |title=The Chaotic Obliquity of Mars
 |url=http://groups.csail.mit.edu/mac/users/wisdom/mars-obliquity.pdf |archive-url=https://web.archive.org/web/20100625103119/http://groups.csail.mit.edu/mac/users/wisdom/mars-obliquity.pdf |archive-date=25 June 2010 |url-status=live
 |journal=[[Science (journal)|Science]]
 |volume=259 |issue= 5099|pages=1294–1297
 |bibcode=1993Sci...259.1294T
 |doi=10.1126/science.259.5099.1294
 |pmid=17732249
 |s2cid=42933021
}}</ref> Some authors dispute that Mars's obliquity is chaotic, and show that tidal dissipation and viscous core-mantle coupling are adequate for it to have reached a fully damped state, similar to Mercury and Venus.<ref name="CorreiaVenusI" /><ref name=Correia2009>{{cite journal
 |last1=Correia |first1=Alexandre C.M
 |last2=Laskar |first2=Jacques
 |title=Mercury's capture into the 3/2 spin-orbit resonance including the effect of core-mantle friction
 |journal=Icarus |date=2009
 |doi=10.1016/j.icarus.2008.12.034
 |arxiv=0901.1843
 |volume=201
 |issue=1
 |pages=1–11
 |bibcode=2009Icar..201....1C
 |s2cid=14778204
}}</ref>

The occasional shifts in the axial tilt of Mars have been suggested as an explanation for the appearance and disappearance of rivers and lakes over the course of the existence of Mars. A shift could cause a burst of methane into the atmosphere, causing warming, but then the methane would be destroyed and the climate would become arid again.<ref>{{cite journal|last1=Rebecca Boyle|title=Methane burps on young Mars helped it keep its liquid water|journal=New Scientist|date=7 October 2017|url=https://www.newscientist.com/article/mg23631464-100}}</ref><ref>{{cite journal|last1=Edwin Kite|display-authors=et al|title=Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars|journal=Nature Geoscience|volume=10|issue=10|pages=737–740|date=2 October 2017|doi=10.1038/ngeo3033|arxiv=1611.01717|bibcode=2017NatGe..10..737K|s2cid=102484593|url=https://authors.library.caltech.edu/80639/4/ngeo3033-s1.pdf |archive-url=https://web.archive.org/web/20180723193849/https://authors.library.caltech.edu/80639/4/ngeo3033-s1.pdf |archive-date=23 July 2018 |url-status=live}}</ref>

The obliquities of the outer planets are considered relatively stable.

{| class="wikitable" style="margin: 0.5em auto; text-align:right;"
|+ Axis and rotation of selected Solar System bodies
|-
! rowspan=3 | Body
! colspan=4 style="background:#F2FEEC;" | [[NASA]], [[J2000]].0<ref name="NASA">[http://nssdc.gsfc.nasa.gov/planetary/planetfact.html Planetary Fact Sheets], at http://nssdc.gsfc.nasa.gov</ref> epoch
! colspan=4 style="background:#edf3fe;" | [[IAU]], 0h 0 January 2010 [[terrestrial time|TT]]<ref>''Astronomical Almanac 2010'', pp. B52, C3, D2, E3, E55</ref> epoch
|-
! rowspan=2 style="background: #F2FEEC;" | Axial tilt <br>(degrees)
! colspan=2 style="background: #F2FEEC;" | North Pole
! rowspan=2 style="background: #F2FEEC;" | Rotational <br>period <br>(hours)
! rowspan=2 style="background: #edf3fe;" | Axial tilt <br>(degrees)
! colspan=2 style="background: #edf3fe;" | North Pole
! rowspan=2 style="background: #edf3fe;" | Rotation <br>(deg./day)
|-
! style="background: #F2FEEC;" | [[Right ascension|R.A.]] (degrees)
! style="background: #F2FEEC;" | [[Declination|Dec.]] (degrees)
! style="background: #edf3fe;" | [[Right ascension|R.A.]] (degrees)
! style="background: #edf3fe;" | [[Declination|Dec.]] (degrees)
|-
| style="text-align:left;" | [[Sun]]
| 7.25 || 286.13 || 63.87 || 609.12{{efn|group=upper-alpha|At 16° latitude; the Sun's rotation varies with latitude.}} || 7.25{{efn|group=upper-alpha|With respect to the [[ecliptic]] of 1850.}} || 286.15 ||63.89 || 14.18
|-
| style="text-align:left;" |  [[Mercury (planet)|Mercury]]
| 0.03 || 281.01 || 61.41 || 1407.6 || 0.01 || 281.01 || 61.45 || 6.14
|-
| style="text-align:left;" |  [[Venus]]
| 2.64 || 272.76 || 67.16 || −5832.6 || 2.64 || 272.76 || 67.16 || −1.48
|-
| style="text-align:left;" |  [[Earth]]
| 23.44 || 0.00 || 90.00 || 23.93 || 23.44 || {{n/a|Undefined}} || 90.00 || 360.99
|-
| style="text-align:left;" |  [[Moon]]
| 6.68 || – || – || 655.73 || 1.54{{efn|group=upper-alpha|With respect to the ecliptic; the Moon's orbit is inclined 5.16° to the ecliptic.}} || 270.00 || 66.54 || 13.18
|-
| style="text-align:left;" |  [[Mars]]
| 25.19 || 317.68 || 52.89 || 24.62 || 25.19 || 317.67 || 52.88 || 350.89
|-
| style="text-align:left;" | [[Jupiter]]
| 3.13 || 268.06 || 64.50 || 9.93{{efn|group=upper-alpha|name=clouds|From the origin of the radio emissions; the visible clouds generally rotate at different rate.}} || 3.12 || 268.06 || 64.50 || 870.54{{efn|group=upper-alpha|name=clouds}}
|-
| style="text-align:left;" | [[Saturn]]
| 26.73 || 40.59 || 83.54 || 10.66{{efn|group=upper-alpha|name=clouds}} || 26.73 || 40.59 || 83.54 || 810.79{{efn|group=upper-alpha|name=clouds}}
|-
| style="text-align:left;" | [[Uranus]]
| 82.23 || 257.31 || −15.18 || −17.24{{efn|group=upper-alpha|name=clouds}} || 82.23 || 257.31 || −15.18 || −501.16{{efn|group=upper-alpha|name=clouds}}
|-
| style="text-align:left;" | [[Neptune]]
| 28.32 || 299.33 || 42.95 || 16.11{{efn|group=upper-alpha|name=clouds}} || 28.33 || 299.40 || 42.95 || 536.31{{efn|group=upper-alpha|name=clouds}}
|-
| style="text-align:left;" | [[Pluto]]{{efn|group=upper-alpha|name=plutopole|NASA lists the coordinates of Pluto's positive pole; noted values have been reinterpreted to correspond to the north/negative pole.}}
| 57.47 || 312.99{{efn|group=upper-alpha|name=plutopole}}
| 6.16{{efn|group=upper-alpha|name=plutopole}} || −153.29 || 60.41 || 312.99 || 6.16 || −56.36
|-
| colspan=9 style="padding:8px 16px; font-size:0.85em;" | {{noteslist|group=upper-alpha}}
|}