Near-IR Spectrophotometry of Jovian Aerosols - Meridional and Vertical Distributions

Abstract

Photometrically calibrated grism spectra of Jupiter in the H (1.45-1.8 μm) and K (1.95-2.5 μm) bands with a resolution of about 100 were taken with the 5-m Hale telescope at Palomar in August of 1995. The spectra were obtained as meridional cuts at six different longitudes on the planet, with one cut crossing the Great Red Spot. The technique outlined in D. Banfieldet al.(1996,Icarus121, 389-410) for the retrieval of scatterer density with altitude from near-infrared spectra is used and refined. It is expected that this retrieval technique will find use in the interpretation of many atmospheric near-infrared reflection spectra, especially those from Galileo NIMS and Cassini VIMS. For the wavelengths and spectral resolution used in this study, the sensitivity of the inversions extends from pressure levels near 400 mbar up to about 20 mbar. Employing this inversion technique on the spectra yields well-resolved jovian cloud densities for τ ≲ 0.1, as a function of latitude and altitude. The density of scatterers is minimum at a height where the pressure is about 100 mbar and increases both upward and downward from this level. The minimum near 100 mbar can be explained by coagulation of settling particles, leading to an increase in fall speed. The results indicate that stratospheric haze particles are generated at heights wherep≲ 20 mbar. © 1998 Academic Press.