Oberon

Identity and classification

Oberon is identified in this profile by the supplied official code MOON-ATLAS-URANUS-OBERON. The evidence places it among Uranus’s five major moons, together with Miranda, Ariel, Umbriel, and Titania. NASA pages specifically describe it as the outermost member of that set of five principal satellites. It can therefore be identified as a moon of Uranus and as the outer member of that major-moon group. The available material, however, provides no numerical orbital parameters: it does not specify orbital distance, orbital period, eccentricity, or inclination.

A meaningful inconsistency concerns its relative size. A JPL image caption calls Oberon Uranus’s outermost and largest moon. Two NASA texts instead call it Uranus’s second-largest moon. Because the supplied evidence neither explains this difference nor gives comparative diameter values, this profile does not resolve the conflict or treat either wording as uniquely established.

Composition, structure, and internal activity

The compositional property explicitly supported by two NASA pages is that Oberon, like Uranus’s other large moons, consists of roughly half ice and half rock. This is an approximate bulk proportion, not an identification of particular minerals, compounds, internal layers, or volatile inventories. The sources do not state what form of ice is present, how ice and rock are distributed, whether the body is internally differentiated, or its mass, density, surface gravity, and thermal properties.

NASA describes Oberon as old, heavily cratered, and showing little evidence of internal activity. This wording connects its visible appearance with an apparently low level of recent geological renewal, but it does not demonstrate that the interior is wholly inactive or without energy. In the supplied evidence, internal activity is known only through that limited surface-based assessment, not through direct measurements of the interior.

Surface and observed geology

The documented surface is dominated by craters. The descriptions old and heavily cratered make impact features central to the visible geological record. NASA also reports unidentified dark material on the floors of many craters. The uncertainty in that statement must be retained: the material is expressly unidentified, so the evidence does not establish its composition, source, emplacement mechanism, connection to impacts, or role in surface evolution.

The images also show distinct highly reflective, high-albedo patches with low-albedo centers. This observation comes from a Voyager 2 narrow-angle-camera image. It is a photometric description of brightness contrast, not a compositional determination. No spectra, topographic data, crater ages, comprehensive geological maps, or explanation of the patches are supplied. A NASA image article identifies Hamlet as a large, dark crater, located to the right of center in the cited image, but provides neither its dimensions nor coordinates, age, or additional geological interpretation.

Observation and exploration

The documented spacecraft exploration comes from Voyager 2, which NASA describes as the only spacecraft to have explored Uranus. The spacecraft made its close approach to the planet in January 1986 and returned images of Uranus and some of its moons. For Oberon, JPL specifies an image acquired on January 22, 1986, from 2.77 million kilometres away, through a clear filter with the narrow-angle camera. The supplied material also refers to a mosaic using Voyager imagery and to generated planetary-map products from JPL; a NASA article attributes a depiction of known surface features to USGS, based on Voyager data.

These facts define both the value and the limitation of the available record: the mapping and interpretation described here depend on observations from one spacecraft mission. The sources provide no evidence for a lander, an Oberon-dedicated orbiter, in-situ sampling, or later spacecraft measurements.

Environment, evolution, and open questions

Oberon belongs to the Uranian system and is the outermost among the five major moons, but the evidence does not describe rings associated with Oberon or any satellites of its own. Information about Cordelia and Ophelia shepherding Uranus’s epsilon ring concerns those bodies, and should not be assigned to Oberon. The supplied sources likewise offer no direct evidence concerning an atmosphere, exosphere, magnetosphere, rotation, seasons, formation, or a dated evolutionary sequence.

The open questions arising directly from the evidence are specific: the nature of the dark crater-floor material; the cause of bright patches with dark centers; the internal structure corresponding to the approximate ice-rock mixture; and the reason for the disagreement over whether it is the largest or second-largest Uranian moon. The reported number of Uranian moons also requires care: one source gives 28 known moons, while another gives 29 known moons as of August 2026. The evidence supports a useful but observationally limited profile of Oberon and does not support filling in the absent physical and dynamical parameters.