Work

JWST Reveals the Kuiper Belt–like Compositions of the Uranian Rings and Small Moons

Year: 2026

Type: article

Abstract: We present the JWST NIRSpec 1–5 μ m spectra of the Uranian rings and four ring moons: Puck, Perdita, Portia, and Juliet. We find that the compositions of the rings and moons strongly resemble water-type Kuiper Belt objects, showing deep 3.0 μ m O–H and water-ice features as well as the CO 2 band at 4.27 μ m. The volatiles show a radial trend of decreasing volatile abundance at closer radial distance to the planet, consistent with recent estimates of the densities of the innermost moons. Given the observed compositional signatures, we suggest two ways to reconcile the history of the small inner moons with that of the regular ones. The first is that the Uranus-tilting collision produced a disk from an impactor formed out of material similar to that which comprises water-rich Kuiper Belt objects, and the ring moons are small undifferentiated remnants of that process. Alternatively, the rings and ring moons postdate the formation of the regular moons, and formed from the later tidal disruption of a several-hundred-kilometer-sized, undifferentiated, water-type Kuiper Belt object.

Source: The Astrophysical Journal Letters

DOI: 10.3847/2041-8213/aeacc0

Authors: Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby, Ian Wong, Michael E. Brown

Institutions: California Institute of Technology, Space Telescope Science Institute

Language: English

Topic: Astro and Planetary Science

Subfield: Space and Planetary Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,400

Funders: National Aeronautics and Space Administration, Space Telescope Science Institute