Saturn's upper troposphere 1986-1989

Erich Karkoschka, Martin G Tomasko

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

This work describes observations of Saturn's atmosphere in the visible and near-infrared (460-940 nm) including 4 hydrogen quadrupole lines, 17 methane absorption bands ranging over 3 orders of magnitude in absorption strength, an ammonia absorption band, and the absolute calibrated continuum spectrum. All observations have complete coverage of Saturn's disk, in latitude as well as in center-to-limb position. A new method describing center-to-limb information is presented. The accuracy of the data is comparable to or better than that of previous data. This data set gives a quite complete description of Saturn's atmosphere in the visible and near infrared at the spatial resolution of ground-based observations. While the main data were acquired in 1988, small changes between 1986 and 1989 were determined also. Weak absorption features of hydrogen, methane, and ammonia show a significant enhancement in the North Polar Region compared to the rest of the planet. An atmospheric model is given which fits all observations within estimated errors. It has clear gas at the top of the atmosphere, an extended haze layer, and a reflective cloud at the bottom. Pressure levels and the haze optical depth were determined as a function of latitude. The single-scattering albedo spectrum of the particles (most likely ammonia ice crystals) is also given for each latitude. The methane mixing ratio is (3.0 ± 0.6) × 10-3, the ammonia mixing ratio is (1.2 + 0.8/-0.6) × 10-3 below the ammonia condensation level. A cold temperature methane absorption spectrum is determined under the assumption that methane band strengths are temperature invariant. It indicates that the absorption coefficients in band centers are typically 20-30% stronger than at room temperature. This spectrum should be useful in the interpretation of methane observations of all the giant planets and Titan.

Original languageEnglish (US)
Pages (from-to)161-181
Number of pages21
JournalIcarus
Volume97
Issue number2
DOIs
StatePublished - 1992

Fingerprint

Saturn
troposphere
methane
ammonia
Saturn atmosphere
haze
mixing ratios
limbs
absorption spectra
mixing ratio
limb
atmosphere
planets
near infrared
planet
hydrogen
atmospheric models
Titan
temperature
ice crystal

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Saturn's upper troposphere 1986-1989. / Karkoschka, Erich; Tomasko, Martin G.

In: Icarus, Vol. 97, No. 2, 1992, p. 161-181.

Research output: Contribution to journalArticle

Karkoschka, Erich ; Tomasko, Martin G. / Saturn's upper troposphere 1986-1989. In: Icarus. 1992 ; Vol. 97, No. 2. pp. 161-181.
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