T276 Big Science from Small Worlds

Wednesday, 25 September 2024
1:30 PM - 5:30 PM
213A

IMPACT-DRIVEN INSIGHTS INTO THE URANIAN MOONS: COULD THE FORMATION OF WUNDA ON UMBRIEL HAVE MOBILIZED A SUBSURFACE OCEAN?

Paper number: T276-8
Program: Technical Sessions
Time: 3:20 PM – 3:40 PM

Authors

Abstract

Umbriel, one of Uranus’ five major satellites, provides a unique opportunity to probe the system’s geologic evolution, including whether any satellites may be ocean worlds. Umbriel’s ~130-km Wunda crater [1] is filled with bright deposits, previously proposed to be either surficially condensed CO2 ice [2], or the remnants of impact-driven cryovolcanism [3]. Occator on Ceres may provide an analog: its bright deposits may originate from a subsurface melt chamber, as well as a potential ocean [4-7]. If Wunda’s bright deposits are indeed endogenic, they present a unique probe of Umbriel’s interior, through a direct connection with an ocean or melting of the overlying ice shell.

Here, we use impact simulations to explore how the Wunda-forming impact reflects Umbriel’s geologic evolution, and find that a wide range of ice shell thicknesses and thermal structures concentrate a potential melt chamber or uplift an ocean. However, our results favor a thin or partially convective ice shell. Colder ice shells, as predicted by thermal models [8], produce deep craters that lack central peaks, which may not be consistent with the inferred morphology. These results suggest Umbriel’s geologic history may be complex – if Umbriel did indeed possess a thick ocean and/or weaker ice shell at the time of Wunda’s formation, the satellite may have experienced higher heat flows than expected, or its ice shell may possess variations in composition (i.e., volatiles) and/or internal structure. As NASA prepares to return to Uranus with its next flagship mission, improved imaging and geodetic measurements of Umbriel will assist in determining Wunda’s relationship to the satellite’s interior.

References: [1] Schenk, P. & Moore, J.M. (2020). Phil. Trans. R. Soc. A 378. [2] Sori, M.M. et al. (2017) Icarus 290. [3] Plescia, J.B. (1987) JGR SP 92. [4] Hesse, M.A. & Castillo-Rogez J.C. (2019) GRL 46. [5] Quick, L.C. et al. (2019) Icarus 320. [6] Bowling, T.J. et al. (2019) Icarus 320. [7] Scully, J.C. et al. (2020) Nat. Comm 11. [8] Castillo-Rogez, J.C. et al. (2023) JGR: Planets 128.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402925

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