Editing Orcus (dwarf planet) (section)

=== Cryovolcanism ===
Crystalline water ice on the surfaces of trans-Neptunian objects should be completely [[Amorphous solid|amorphized]] by the galactic and Solar radiation in about 10 million years.<ref name="Barucci2008" /> Thus the presence of [[crystal]]line water [[ice]], and possibly [[ammonia]] ice, may indicate that a renewal mechanism was active in the past on the surface of Orcus.<ref name="Barucci2008" /> Ammonia so far has not been detected on any trans-Neptunian object or icy satellite of the outer planets other than [[Miranda (moon)|Miranda]].<ref name="Barucci2008" /> The 1.65&nbsp;[[micrometre|μm]] band on Orcus is broad and deep (12%), as on Charon, {{dp|Quaoar}}, {{dp|Haumea}}, and icy satellites of the [[giant planets]].<ref name="Barucci2008" /> Some calculations indicate that [[cryovolcano|cryovolcanism]], which is considered one of the possible renewal mechanisms, may indeed be possible for trans-Neptunian objects larger than about {{convert|1000|km|mi|abbr=on}}.<ref name="Delsanti2010" /> Orcus may have experienced at least one such episode in the past, which turned the amorphous water ice on its surface into crystalline. The preferred type of volcanism may have been explosive aqueous volcanism driven by an explosive dissolution of methane from water–ammonia melts.<ref name="Delsanti2010" />