Jovian chromophore characteristics from multispectral HST images

Abstract

The chromophores responsible for coloring the jovian atmosphere are embedded within Jupiter’s vertical aerosol structure. Sunlight propagates through this vertical distribution of aerosol particles, whose colors are defined by ϖ 0( λ), and we remotely observe the culmination of the radiative transfer as I/ F( λ). In this study, we employed a radiative transfer code to retrieve ϖ 0( λ) for particles in Jupiter’s tropospheric haze at seven wavelengths in the near-UV and visible regimes. The data consisted of images of the 2008 passage of Oval BA to the south of the Great Red Spot obtained by the Wide Field Planetary Camera 2 on-board the Hubble Space Telescope. We present derived particle colors for locations that were selected from 14 weather regions, which spanned a large range of observed colors. All ϖ 0( λ) curves were absorbing in the blue, and ϖ 0( λ) increased monotonically to approximately unity as wavelength increased. We found accurate fits to all ϖ 0( λ) curves using an empirically derived functional form: ϖ 0( λ) = 1 − A exp(− Bλ). The best-fit parameters for the mean ϖ 0( λ) curve were A = 25.4 and B = 0.0149 for λ in units of nm. We performed a principal component analysis (PCA) on our ϖ 0( λ) results and found that one or two independent chromophores were sufficient to produce the variations in ϖ 0( λ). A PCA of I/ F( λ) for the same jovian locations resulted in principal components (PCs) with roughly the same variances as the ϖ 0( λ) PCA, but they did not result in a one-to-one mapping of PC amplitudes between the ϖ 0( λ) PCA and I/ F( λ) PCA. We suggest that statistical analyses performed on I/ F( λ) image cubes have limited applicability to the characterization of chromophores in the jovian atmosphere due to the sensitivity of I/ F( λ) to horizontal variations in the vertical aerosol distribution.