Editing Hyperion (moon) (section)

=== Shape ===
Hyperion is one of the largest bodies known to be highly irregularly shaped (non-ellipsoidal, i.e. not in [[hydrostatic equilibrium]]) in the [[Solar System]].<ref name="nb larger objects" group="lower-alpha"/> The only larger moon known to be irregular in shape is Neptune's moon [[Proteus (moon)|Proteus]]. Hyperion has about 15% of the mass of [[Mimas (moon)|Mimas]], the least massive known ellipsoidal body. The largest [[Impact crater|crater]] on Hyperion is approximately {{convert|121.57|km|mi|abbr=on}} in diameter and {{convert|10.2|km|mi|abbr=on}} deep. A possible explanation for the irregular shape is that Hyperion is a fragment of a larger body that was broken up by a large impact in the distant past.<ref name="Matthews1992">
{{cite journal
 |author=R.A.J. Matthews
 |date=1992
 |title=The Darkening of Iapetus and the Origin of Hyperion
 |journal=[[Quarterly Journal of the Royal Astronomical Society]]
 |volume=33 |pages=253–258
 |bibcode=1992QJRAS..33..253M
}}</ref> A proto-Hyperion could have been {{convert|350|–|1000|km|mi|abbr=on}} in diameter (which ranges from a little below the size of Mimas to a little below the size of [[Tethys (moon)|Tethys]]).<ref name=Farinella1997>{{cite journal
  |last=Farinella |first=P.
  |author2=Marzari, F. |author3=Matteoli, S.
   |title=The Disruption of Hyperion and the Origin of Titan's Atmosphere
  |journal=Astronomical Journal
  |volume=113 |issue=2 |pages=2312–2316 |date=1997
  |doi=10.1086/118441
  |bibcode=1997AJ....113.2312F
  |doi-access=free}}</ref> Over about 1,000&nbsp;years, ejecta from a presumed Hyperion breakup would have impacted [[Titan (moon)|Titan]] at low speeds, building up [[Volatile (astrogeology)|volatiles]] in the [[atmosphere of Titan]].<ref name="Farinella1997" />