The science case for spacecraft exploration of the Uranian satellites: Candidate ocean worlds in an ice giant system

TL;DR

This paper argues that Uranus' moons are promising candidates for ocean worlds with potential subsurface liquids, emphasizing the need for future orbiter missions to explore their surface compositions and potential habitability.

Contribution

It highlights the scientific importance of studying Uranus' moons as potential ocean worlds and advocates for dedicated orbiter missions to obtain detailed surface and subsurface data.

Findings

Voyager 2 images suggest classical moons are candidate ocean worlds.

Surface compositions are largely unknown due to limited data.

Future missions are needed for detailed exploration and understanding.

Abstract

The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus' five largest 'classical' moons Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon Puck, but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved datasets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons' surface compositions, and the processes that modify them, is limited to disk-integrated datasets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and investigate Uranus' ring moons and irregular satellites, close-up observations and measurements made by instruments onboard a Uranus orbiter are needed.