Discovery of co2 ice and leading–trailing spectral asymmetry on the uranian satellite ariel

New 0.8- to 2.4- micro m spectral observations of the leading and trailing hemispheres of the uranian satellite Ariel were obtained at IRTF /SpeX during 2002 July 16 and 17 UT. The new spectra reveal contrasts between Ariel's leading and trailing hemispheres, with the leading hemisphere presenting deeper H sub 2O ice absorption bands. The observed dichotomy is comparable to leading-trailing spectral asymmetries observed among jovian and saturnian icy satellites. More remarkably, the trailing hemisphere spectrum exhibits three narrow CO sub 2 ice absorption bands near 2 micro m. This discovery of CO sub 2 ice on one hemisphere of Ariel is its first reported detection in the uranian system.