Color and the Vertical Structure in Jupiter's Belts, Zones, and Weather Systems

Abstract

Radiative transfer analysis was performed with data taken by the Galileo spacecraft Solid State Imager (SSI) during its nominal mission (December 1995 to December 1997). The objective is to use the methane band (727 and 889 nm) and color (410 and 756 nm) sensitivities to identify the vertical position of cloud absorption that leads to coloration. Earlier work (Banfield et al. 1998, Icarus 135, 230–250) with only the near-IR continuum and methane band images yielded information about the vertical distribution of cloud scatterers, but no information on the wavelength dependence of cloud absorption. The new analysis employs the same parameter retrieval algorithm, but adds the 410-nm wavelength. Under the assumption that the 410-nm absorption by cloud particles is indicative of spectrally broad blue absorption, the new channel gives color information. The primary color difference between the dark north equatorial belt (NEB) and the brighter equatorial zone (EZ) appears to be in the tropospheric haze layer's 410-nm single scattering albedo. This layer extends through the stably stratified region approximately from 200 to 800 mbars. The base of the haze layer is slightly deeper in the NEB (by about 200 mbars) than in the EZ, and a variable thickness white cloud layer at the base of the haze exists in both regions, but is about five times optically thicker in the EZ. Within the EZ, slight color variation is seen with latitude, again due to 410-nm single scattering albedo variation in the haze layer. Anomalous regions, such as the Great Red Spot and a 5-μm hot spot, are modeled, showing additional variations in the structure and color of the tropospheric haze. Deeper clouds with pressures of ≥1.7 bars are seen in occasional clearings, but their opacity and color are not well constrained by the data.