Properties of scatterers in the troposphere and lower stratosphere of Uranus based on Voyager imaging data

Kathy Rages, James B. Pollack, Martin G. Tomasko, Lyn R. Doose

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

We have used photometrically and geometrically corrected Voyager images of Uranus to define spatially resolved specific intensities over a wide range of phase angles for two latitude bands and have modeled these data with scalar and vector radiative transfer and microphysical models. Our scattering model included photo-chemically produced hydrocarbon ices in the stratosphere and upper troposphere, a methane ice cloud from 1.2-1.3 bar, and an optically thick hydrogen sulfide cloud at 3 bars. We find that the methane cloud has an optical depth of 0.7 at 22.5°S and an optical depth of 2.4 at 65°S. The mean particle size in the methane cloud is ≪10 μm for the most likely particle shapes and is probably about 1 μm. The volume absorption coefficient of the methane cloud particles is about 50% higher at 22.5°S than at 65°S, assuming the mean cloud particle size is the same at both latitudes. The mass production rate of the stratospheric hydrocarbon ice components is about 10-16 g cm-2 sec-1, and the average particle charge in the stratosphere is around 10 electrons per micrometer diameter. The imaginary part of the stratospheric haze refractive index is ∼0.01-0.001, and there are ∼10 precipitable nanometers of non-volatile absorbing haze residue per kilometer-amagat of gas between 1.3 and 3 bar.

Original languageEnglish (US)
Pages (from-to)359-376
Number of pages18
JournalIcarus
Volume89
Issue number2
DOIs
StatePublished - Feb 1991

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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