First Ground-Based Look at Compositional Differences in the Uranian Satellites

Observations of four of the five inner Uranian satellites, Ariel, Umbriel, Titania, and Oberon, have been obtained in the U, B, V, and R filters. The construction of rotational lightcurves has begun for each satellite in order to determine surface components and to gain an understanding of the exogenous alteration processes that caused them. The lightcurves will also be used to compare the colors and albedos of the leading and trailing sides of each moon. Images collected previously by Voyager were analyzed by Buratti and Mosher in 1991 and revealed the leading sides of the outer four satellites to be redder than the trailing sides. The magnitude of the color dichotomy increased with distance from Uranus. A false aperture technique was used to create the lightcurve for each satellite by accounting for the scattered light from Uranus. These observations are the first of their kind because of the moons' previous poleward orientation with Earth. The results for the satellite Oberon agree with the data collected by Voyager and thus reveal the hemispherical color differences.