THE ULTRAVIOLET CONTINUUM ALBEDO OF URANUS

The geometric albedo of Uranus between 2000 and 5000 Å is analyzed using a radiative transfer code which explicitly treats Raman scattering of solar photons by H2. We analyze the combination of ground-based spectrophotometry by J.S. Neff et al. (Icarus 60, 221-235, 1984) from 3500 to 5000 Å and IUE data by R. Wagener et al. Icarus 60, 281-288, 1986) from 2088 to 3350 Å. We have used the model of K.H. Baines and J.T. Bergstralh (Icarus 65, 406-441, 1986) as a baseline model. This model fits the ground-based data as well as the IUE data at λ>2500 A ̊ quite well. The peaks in geometric albedo produced by Raman scattering filling in the cores of solar absorption lines are reproduced in detail by the model. The baseline model, however, is too bright for λ < 2400 A ̊. Since there is no likely source of molecular absorption in this spectral region, this discrepancy is most easily resolved by inclusion of an absorbing stratospheric haze layer. A small amount of absorbing haze particles in the stratosphere is required to match the IUE data. These results are consistent with the model of J. B. Pollack et al. (J. Geophys. Res. 92, 15037-15065, 1987) in which aerosols are produced in the stratosphere by photochemical processing of hydrocarbons. © 1990.