Organic Molecules and the Coloration of Jupiter

Abstract

BOTH naked eye and photographic observations of the visible surface of the planet Jupiter reveal the presence of regions of contrasting and variegated colours. The bands, belts and spots—particularly the Great Red Spot—exhibit characteristic coloration which must indicate differences in molecular composition from place to place at the level of the Jovian clouds. All spectroscopic searches for characteristic spectral features unique to a band, belt or spot have been negative. For example, the Great Red Spot appears spectroscopically as enhanced continuous absorption at short wavelengths with no other identifying spectral features at the resolving powers used. The variable appearance of the Jovian cloud coloration suggests that the molecules responsible are synthesized in certain locales, transported, and dissociated in other locales. Were the coloured compounds produced by a planet-wide thermodynamic equilibrium, the planet should show a generally uniform coloration. Micro-meteoritic infall should provide a small steady-state abundance of certain minerals; however, it seems highly implausible that such minerals would be differentially distributed over the clouds of Jupiter in such a way as to explain the coloration. A more plausible source of chromophores would appear to be the chief atmospheric constituents themselves, thus implying that the coloration is caused by the presence of organic matter at the cloud level of Jupiter^1,2.