Composition of saturn's atmosphere at northern temperate latitudes from Voyager iris spectra: NH/sub 3/, PH/sub 3/, C/sub 2/H/sub 2/, C/sub 2/H/sub 6/, CH/sub 3/D, CH/sub 4/, and the saturnian D/H isotopic ratio
The abundances of minor atmospheric constituents at northern Saturnian latitudes have been inferred from infrared emission spectra recorded by Voyager. The NH/sub 3/, PH/sub 3/, C/sub 2/H/sub 2/, and C/sub 2/H/sub 6/ vertical distributions have been determined from spectra selected in a cloud-free region centered approximately at the latitude of the Voyager 2 radio-occultation point (36.5 N). The NH/sub 3/ mixing ratio in the upper troposphere is found to be compatible with the saturated partial pressure. The inferred PH/sub 3//H/sub 2/ ratio of 1.4 +- 0.8 x 10/sup -6/ is higher than the value derived from the solar P/H ratio, and the PH/sub 3/ vertical profile may extend somewhat into the stratosphere, up to a few millibars. The stratospheric C/sub 2/H/sub 2//H/sub 2/ and C/sub 2/H/sub 6//H/sub 2/ ratios are, respectively, 2.1 +- 1.4 x 10/sup -7/ and 3.0 x 1.1 x 10/sup -6/; the latter decreases sharply below the 20-50 mbar level. A larger selection of spectra yields CH/sub 3/D/H/sub 2/ = 3.9 +- 2.5 x 10/sup -7/ and CH/sub 4//H/sub 2/ = 4.5/sup +2.4//sub -1.9/ x 10/sup -3/. This result implies an enrichment of Saturn's upper atmosphere is carbon by at least a factor of 3 over the solar abundance. The D/H value resulting from our CH/sub 3/D/CH/sub 4/ ratio is 1.6/sup +1.3//sub -1.2/ x 10/sup -5/, significantly lower than previous determinations obtained from HD lines; it is also less than half of the IRIS-inferred Jovian value. Finally, the interpretation of two NH/sub 3/ lines in the 5 ..mu..m window suggests a NH/sub 3/H/sub 2/ ratio at the 2 bar level below the solar value.
- Research Organization:
- Laboratoire d'Astronomie Infra-Rouge (CNRS), Observatoire de Paris-Meudon, France
- OSTI ID:
- 6025833
- Journal Information:
- Astrophys. J.; (United States), Vol. 287:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
SATURN PLANET
PLANETARY ATMOSPHERES
ABUNDANCE
AMMONIA
CHEMICAL COMPOSITION
DEUTERIUM
HYDROCARBONS
INFRARED SPECTRA
ISOTOPE RATIO
PHOSPHINES
ATMOSPHERES
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHORUS COMPOUNDS
PLANETS
SPECTRA
STABLE ISOTOPES
640107* - Astrophysics & Cosmology- Planetary Phenomena