82 Friends of Hoth, Episode IX: The Rise of Icy Ocean Worlds

We invite abstracts relating to surface, structural, and tectonic processes; interior, and thermal evolution; geochemistry and astrobiology; and planetary analogs as they pertain to outer planet icy satellites. This includes experimental, observational, and theoretical approaches.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 214B

Leveraging Ceres to Gain Insights into the Candidate Ocean Worlds of Umbriel and Oberon that Orbit Uranus

Paper number: 82-13
Program: Technical Sessions
Time: 11:15 AM – 11:30 AM

Authors

Abstract

There are intriguing parallels between Ceres (inner Solar System dwarf planet) and two of the large Uranian satellites: Umbriel and Oberon. Thus, we leverage data acquired by the Dawn mission to gain insights into specific surface features on Umbriel and Oberon. The bright deposit in Umbriel’s Wunda crater, previously suggested to be cold-trapped CO2 ice (Sori+2017) or cryovolcanic (Plescia1987), is reminiscent of the bright salt deposits in Ceres’ Occator crater, called faculae. Occator’s faculae are salt deposits (De Sanctis+2016, Raponi+2019) from brines derived from a subsurface impact-induced melt reservoir and remnant subsurface ocean (Scully+2020). Thus, we hypothesize a similar potential formation mechanism for Wunda’s bright deposit. We also find comparable overall morphometries of Ceres’ Ahuna Mons and an unnamed mountain on Oberon, previously suggested to be an impact crater central peak (Smith+1986, Blanco-Rojas+in review), tectonic feature, equatorial ridge, or volcanic construct (Schenk&Moore2020). On Ceres, Ahuna Mons is an extrusive cryovolcanic dome (Ruesch+2016) formed by a slurry of brine and solids from the remnant subsurface ocean (Ruesch+2019). We hypothesize the mountain on Oberon may have formed similarly.

We suggest that the dark central area in Wunda is a central peak, contributing to the annulus shape of Wunda’s bright deposit. We found that stretching the Umbriel data does not enhance areas within Wunda’s bright deposit as it does with the Ceres data, likely due to instrument and observational limitations. Given the change in size of Occator’s faculae in images after stretching, we assume that the diameter of the Wunda bright material (~80 km) as measured by Smith+1986 is overestimated. Ruesch+2016 found that the aspect ratio of  Ahuna Mons is 0.24, consistent with extrusive volcanic domes (~0.2) and with our measured aspect ratio of Oberon’s mountain: 0.25+0.25-0.13. The aspect ratio of central peaks on some icy satellites is 0.05 or 0.06 (Bray+2012, Moore+2004, Schenk1991), significantly lower than the (cryo)volcanic domes. However, the aspect ratio of the central peak of Mimas’ Herschel crater is 0.24 (Moore+2004, Schenk1989). Therefore, further data is needed to discern between the cryovolcanic dome and central peak hypotheses. We also derive types of observations a potential future Uranus Orbiter and Probe mission could make to further test our hypotheses.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413856

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