Editing Oberon (moon) (section)

== Composition and internal structure ==
[[File:Oberon Earth Moon Comparison.png|thumb|left|250px|Size comparison of [[Earth]], the [[Moon]], and Oberon.]]

Oberon is the second-largest and second-most massive of the Uranian moons after [[Titania (moon)|Titania]], and the ninth-most massive moon in the Solar System.{{efn|The eight moons more massive than Oberon are [[Ganymede (moon)|Ganymede]], [[Titan (moon)|Titan]], [[Callisto (moon)|Callisto]], [[Io (moon)|Io]], Earth's [[Moon]], [[Europa (moon)|Europa]], [[Triton (moon)|Triton]], and [[Titania (moon)|Titania]].<ref name="NASA" /> }} It is the [[List of Solar System objects by size|tenth-largest moon by size]] however, since [[Rhea (moon)|Rhea]], the second-largest moon of [[Saturn]] and the ninth-largest moon, is nearly the same size as Oberon although it is about 0.4% larger, despite Oberon having more mass than Rhea.<ref>{{Cite web|title=By The Numbers {{!}} Oberon - NASA Solar System Exploration|url=https://solarsystem.nasa.gov/moons/uranus-moons/oberon/by-the-numbers/|website=NASA|date=11 November 2017 }}</ref> Oberon's density of 1.68&nbsp;g/cm<sup>3</sup>, which is higher than the typical density of [[Moons of Saturn |Saturn's satellites]], indicates that it consists of roughly equal proportions of [[Ice|water ice]] and a dense non-ice component.<ref name="Hussmann Sohl et al. 2006" /> The latter could be made of [[rock (geology)|rock]] and [[carbon]]aceous material including heavy [[organic compound]]s.<ref name="Smith Soderblom et al. 1986" /> The presence of water ice is supported by [[spectroscopic]] observations, which have revealed [[crystalline]] water ice on the surface of the moon.<ref name="Grundy Young et al. 2006" /> Water ice [[absorption band]]s are stronger on Oberon's trailing hemisphere than on the leading hemisphere. This is the opposite of what is observed on other Uranian moons, where the leading hemisphere exhibits stronger water ice signatures.<ref name="Grundy Young et al. 2006" /> The cause of this asymmetry is not known, but it may be related to [[impact gardening]] (the creation of soil via impacts) of the surface, which is stronger on the leading hemisphere.<ref name="Grundy Young et al. 2006" /> [[Meteorite impact]]s tend to sputter (knock out) ice from the surface, leaving dark non-ice material behind.<ref name="Grundy Young et al. 2006" /> The dark material itself may have formed as a result of radiation processing of [[methane]] [[clathrate hydrate|clathrates]] or radiation darkening of other organic compounds.<ref name="Smith Soderblom et al. 1986" /><ref name="Bell McCord 1991" />

Oberon may be differentiated into a rocky [[core (geology)|core]] surrounded by an icy [[mantle (geology)|mantle]].<ref name="Hussmann Sohl et al. 2006" /> If this is the case, the radius of the core (480&nbsp;km) is about 63% of the radius of the moon, and its mass is around 54% of the moon's mass—the proportions are dictated by the moon's composition. The pressure in the center of Oberon is about 0.5&nbsp;[[GPa]] (5&nbsp;[[kbar]]).<ref name="Hussmann Sohl et al. 2006" /> The current state of the icy mantle is unclear. If the ice contains enough [[ammonia]] or other [[antifreeze]], Oberon may possess a liquid [[ocean layer]] at the core–mantle boundary. The thickness of this ocean, if it exists, is up to 40&nbsp;km and its temperature is around 180&nbsp;K (close to the water–ammonia [[eutectic temperature]] of 176&nbsp;K).<ref name="Hussmann Sohl et al. 2006" /> However, the internal structure of Oberon depends heavily on its thermal history, which is poorly known at present. Albeit more recent  publications seem to be in favour of active subterranean oceans throughout the larger moons of Uranus.<ref>{{cite web |title=New Study of Uranus' Large Moons Shows 4 May Hold Water |website=[[NASA]] |date=4 May 2023 |archive-url=https://web.archive.org/web/20230524131930/https://www.nasa.gov/feature/jpl/new-study-of-uranus-large-moons-shows-4-may-hold-water/ |archive-date=2023-05-24 |url-status=live |url=https://www.nasa.gov/feature/jpl/new-study-of-uranus-large-moons-shows-4-may-hold-water/}}</ref><ref>{{Cite web |title=New research prompts rethink on chances of life on Uranus moons |url=https://www.bbc.com/news/articles/cgk1333k0ypo |access-date=2024-11-15 |website=www.bbc.com |date=11 November 2024 |language=en-GB}}</ref>