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== Rotational characteristics ==

== Rotational characteristics ==

Hyperion's rotation is chaotic and nearly unpredictable.<ref name=Wisdom>J. Wisdom, S.J. Peale, F. Mignard. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-47313KS-YY&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d42f224c66e0051b451986d67951aca5 The chaotic rotation of Hyperion]". (IAU, COSPAR, NASA, et al., Colloquium on Natural Satellites, 77th, Cornell University, Ithaca, NY, July 5-9, 1983) ''Icarus'' (ISSN 0019-1035) 58: 137-152. {{doi|0.1016/0019-1035(84)90032-0}} Accessed June 9, 2008.</ref> Astronomers cite a number of factors, including the 4:3 orbital resonance with Titan, to account for this.<ref name=Britannica/><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/hyperion.html Entry for Hyperion]." ''The <s>Nine</s> 8 Planets'', July 12, 2007. Accessed June 9, 2008.</ref><ref name=Piazza>Piazza, Eric. "[http://saturn.jpl.nasa.gov/science/moons/moonDetails.cfm?pageID=6 Cassini-Huygens: Moons: Hyperion]." November 3, 2006. Accessed June 9, 2008.</ref>

Hyperion's rotation is chaotic and nearly unpredictable.<ref name=Wisdom>J. Wisdom, S.J. Peale, F. Mignard. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-47313KS-YY&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d42f224c66e0051b451986d67951aca5 The chaotic rotation of Hyperion]". (IAU, COSPAR, NASA, et al., Colloquium on Natural Satellites, 77th, Cornell University, Ithaca, NY, July 5–9, 1983) ''Icarus'' (ISSN 0019-1035) 58: 137-152. {{doi|0.1016/0019-1035(84)90032-0}} Accessed June 9, 2008.</ref> Astronomers cite a number of factors, including the 4:3 orbital resonance with Titan, to account for this.<ref name=Britannica/><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/hyperion.html Entry for Hyperion]." ''The <s>Nine</s> 8 Planets'', July 12, 2007. Accessed June 9, 2008.</ref><ref name=Piazza>Piazza, Eric. "[http://saturn.jpl.nasa.gov/science/moons/moonDetails.cfm?pageID=6 Cassini-Huygens: Moons: Hyperion]." November 3, 2006. Accessed June 9, 2008.</ref>

== Physical characteristics ==

== Physical characteristics ==

Hyperion has an irregular shape, with dimensions 185 x 140 x 113 km.<ref name=saturnsatfact/> In fact it is the largest irregularly shaped body in the solar system. Proteus, moon of [[Neptune]], is often cited as a larger irregular body, but in fact Proteus is not irregular and is almost spherical.<ref name=Arnett/> Hyperion is also highly porous, with a density only 57% of that of [[water]].<ref name=saturnsatfact/>

Hyperion has an irregular shape, with dimensions 185 x 140 x 113&nbsp;km.<ref name=saturnsatfact/> In fact it is the largest irregularly shaped body in the solar system. Proteus, moon of [[Neptune]], is often cited as a larger irregular body, but in fact Proteus is not irregular and is almost spherical.<ref name=Arnett/> Hyperion is also highly porous, with a density only 57% of that of [[water]].<ref name=saturnsatfact/>

=== Surface ===

=== Surface ===

[[Image:Hyperion Meri green.jpg|thumb|150px|left|Hyperion in color enhancement]]Hyperion has craters that cover its surface completely, making it spongiform in appearance.<ref name=Thomas>Thomas, P. C.; et al. (2007). "[http://www.nature.com/nature/journal/v448/n7149/abs/nature05779.html;jsessionid=8884731760421E844AF551ABA6E2527F Hyperion's sponge-like appearance]". Nature 448: 50-56. {{doi|10.1038/nature05779}}. Accessed June 9, 2008.</ref> Those craters are remarkably well preserved, primarily on account of Hyperion's low density. The largest crater on Hyperion has a diameter of 120 km and a depth of 10 km.<ref name=Piazza/>

[[Image:Hyperion Meri green.jpg|thumb|150px|left|Hyperion in color enhancement]]Hyperion has craters that cover its surface completely, making it spongiform in appearance.<ref name=Thomas>Thomas, P. C.; et al. (2007). "[http://www.nature.com/nature/journal/v448/n7149/abs/nature05779.html;jsessionid=8884731760421E844AF551ABA6E2527F Hyperion's sponge-like appearance]". Nature 448: 50-56. {{doi|10.1038/nature05779}}. Accessed June 9, 2008.</ref> Those craters are remarkably well preserved, primarily on account of Hyperion's low density. The largest crater on Hyperion has a diameter of 120&nbsp;km and a depth of 10&nbsp;km.<ref name=Piazza/>

Hyperion is one of the least reflective of Saturn's moons, with an albedo of 30%. Many astronomers believe that Hyperion is covered with dark material that comes from [[Phoebe]], an outer moon.<ref name=Hamilton/> Recent data from the [[Cassini-Huygens Mission|Cassini]] probe indicates that this material consists of hydrocarbons.<ref name=scidaily>NASA/Ames Research Center. "[http://www.sciencedaily.com/releases/2007/07/070705125818.htm Hydrocarbons, Necessary For Life, Found On Saturn's Moon Hyperion]." ''ScienceDaily'' 6 July 2007. Accessed 9 June 2008.</ref>

Hyperion is one of the least reflective of Saturn's moons, with an albedo of 30%. Many astronomers believe that Hyperion is covered with dark material that comes from [[Phoebe]], an outer moon.<ref name=Hamilton/> Recent data from the [[Cassini-Huygens Mission|Cassini]] probe indicates that this material consists of hydrocarbons.<ref name=scidaily>NASA/Ames Research Center. "[http://www.sciencedaily.com/releases/2007/07/070705125818.htm Hydrocarbons, Necessary For Life, Found On Saturn's Moon Hyperion]." ''ScienceDaily'' 6 July 2007. Accessed 9 June 2008.</ref>

The favorite theory of the origin of Hyperion is that it is a fragment of a larger body that suffered a collision.<ref name=Piazza/><ref name=Arnett/> At least one astronomer speculated that debris from this collision contributed to the dark material that covers the Cassini Region of [[Iapetus]].<ref name=Matthews>Matthews, Robert A. J. "[http://adsabs.harvard.edu/abs/1992QJRAS..33..253M The Darkening of Iapetus and the Origin of Hyperion]." ''Quarterly Journal of the Royal Astronomical Society'', 33:253–258, September 1992. Accessed June 9, 2008.</ref>

The favorite theory of the origin of Hyperion is that it is a fragment of a larger body that suffered a collision.<ref name=Arnett/><ref name=Piazza/> At least one astronomer speculated that debris from this collision contributed to the dark material that covers the Cassini Region of [[Iapetus]].<ref name=Matthews>Matthews, Robert A. J. "[http://adsabs.harvard.edu/abs/1992QJRAS..33..253M The Darkening of Iapetus and the Origin of Hyperion]." ''Quarterly Journal of the Royal Astronomical Society'', 33:253–258, September 1992. Accessed June 9, 2008.</ref>

== Observation and Exploration ==

== Observation and Exploration ==