Near infrared reflection spectra of ammonia frost: interpretation of the upper clouds of Saturn.
Abstract
Models of the uppermost cloud layer on Saturn indicate that the cloud is composed of solid ammonia, with the cloud particles initially formed at about 150 K and subsequently transported upward by convection to colder regions of the atmosphere. For the purpose of comparison with Saturn's near-IR reflection spectrum, laboratory reflection spectra of ammonia frost corresponding to a variety of deposition rates and deposition temperatures have been obtained. It is found that the spectral location of the strong 3-micron absorption band of solid ammonia is highly dependent upon the manner in which the frost layer is formed. For rapid deposition on a 150-K cryosurface, which closely simulates what is believed to be the cloud formation process on Saturn, the band is centered at 3.29 microns. This band location, together with the apparent absence of gaseous ammonia overlying the solid ammonia cloud, is consistent with Saturn's observed reflection spectrum in the vicinity of 3 microns. Comparison of Saturn's reflection spectrum with that of Jupiter, in the vicinity of 1.3 and 1.6 microns, also supports the hypothesis of a Saturnian ammonia ice cloud.
- Publication:
-
Journal of Quantitative Spectroscopy and Radiative Transfer
- Pub Date:
- November 1978
- DOI:
- 10.1016/0022-4073(78)90052-3
- Bibcode:
- 1978JQSRT..20..481S
- Keywords:
-
- Absorption Spectra;
- Ammonia;
- Atmospheric Models;
- Cloud Cover;
- Infrared Reflection;
- Infrared Spectra;
- Saturn Atmosphere;
- Abundance;
- Atmospheric Chemistry;
- Ice Clouds;
- Jupiter Atmosphere;
- Near Infrared Radiation;
- Solidified Gases;
- Upper Atmosphere;
- Lunar and Planetary Exploration;
- Ammonia:Infrared Spectra;
- Ammonia:Saturn Atmosphere