Optical Spectroscopy of the Uranian Moons from Equinox to Northern Summer
March 2026 • 2026PSJ.....7...67D
Abstract • We present an analysis of ground-based visible and near-infrared wavelength (VIS, ∼0.4─0.9 μm) reflectance spectra of the four largest Uranian satellites, utilizing observations with multiple telescopes, collected near Uranian equinox and in northern summer (2002─2024). These data have much higher spectral resolution and signal-to-noise ratios compared to previously published optical spectra of the Uranian moons, collected primarily in the 1980s and 1990s. The higher signal-to-noise ratios and longitudinal coverage of these new data allowed us to determine that the Uranian satellites exhibit distinct spectral slope variations across the VIS, supporting previous findings that the leading hemispheres of Titania and Oberon are redder than their respective trailing hemispheres. We find that the northern leading hemisphere of Titania appears to be redder than Oberon, and that Titania may have a larger leading/trailing asymmetry in reddening on its northern hemisphere compared to the other three large moons. We also conducted a sensitive search for subtle absorption features, but found no reliable evidence of broad mineral absorption bands, condensed O2, or other possible products of radiolytic processing; aside from the spectral slope, the spectra of the Uranian moons appear to be featureless in the visible wavelength range.
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