Saturn atmosphere

Data analyses of circular polarization also yielded an ambiguous solution rir= 1.44 and reff = 1.4 micrometers, and r= 1-60 and 2 < r ff < 5 micrometers, the effective variance being Veff = 0.07 for both solutions [25]. Recalculation of the size distribution for the first solution using a log normal distribution gives an average geometrical particle radius of about 1.2 micrometers. Therefore, nearly the same results were obtained independently of the Stokes parameters used in the analyses. This means that the vertical stratification of particle sizes in the Saturn atmosphere is weak. 

Alkanes have the general molecular formula C H2 +2 The srmplest one methane (CH4) rs also the most abundant Large amounts are present rn our atmosphere rn the ground and rn the oceans Methane has been found on Juprter Saturn Uranus Neptune and Pluto and even on Halley s Comet... 

Diacetylene (HC=C—C=CH) has been identified as a component of the hydrocarbon rich atmospheres of Uranus Neptune and Pluto It is also present m the atmospheres of Titan and Triton satellites of Saturn and Neptune respectively... 

Water can be found, in all three aggregate states, almost everywhere in the universe as ice in the liquid phase on the satellites of the outer solar system, including Saturn s rings and in the gaseous state in the atmospheres of Venus, Mars and Jupiter and in comets (as can be shown, for example, from the IR spectra of Halley s comet). The OH radical has been known for many years as the photodissociation product of water. 

Methane is a major component in the atmospheres of Jupiter ( KM), Saturn ( ... 

The next most likely possibility is cometary delivery of the atmosphere but again there are some problems with the isotope ratios, this time with D/H. The cometary D/H ratios measured in methane from Halley are 31 3 x 10-5 and 29 10 x 10-5 in Hayuatake and 33 8 x 10-5 in Hale-Bopp, whereas methane measurements from Earth of the Titan atmosphere suggest a methane D/H ratio of 10 5 x 10-5, which is considerably smaller than the ratio in the comets. The methane at least in Titan s atmosphere is not exclusively from cometary sources. Degassing of the rocks from which Titan was formed could be a useful source of methane, especially as the subnebula temperature around Saturn (100 K) is somewhat cooler than that around Jupiter. This would allow volatiles to be more easily trapped on Titan and contribute to the formation of a denser atmosphere. This mechanism would, however, apply to all of Saturn s moons equally and this is not the case. 

Alkanes are often found in natural systems. They are the main constituents in the atmospheres of the planets Jupiter, Saturn, Uranus, and Neptune. Methane is also thought to have been a major component of the atmosphere of the early Earth. Natural gas and oil are primarily made of alkanes. 

Aspects of the chemical composition of the atmospheres of Jupiter, Saturn, Uranus, and Neptune were measured by the Voyager and Galileo spacecraft in the 1980s and 1990s,... 

Hydrogen isotopic compositions, expressed as molar D/H ratios, of solar system bodies. The relatively low D/H values in the atmospheres of Jupiter and Saturn are similar to those in the early Sun, whereas D/H ratios for Uranus and Neptune are intermediate between the Jupiter-Saturn values and those of comets and chondrites. The Earth s oceans have D/H shown by the horizontal line. Mars values are from SNC meteorites. Modified from Righter et al. (2006) and Lunine (2004). 

Isotopic abundances for hydrogen have been measured in giant planet atmospheres, as shown in Figure 14.11. The D/H ratios in Jupiter and Saturn are similar to those in the Sun, but lower than those in the Earth s oceans or in comets. D/H ratios in Uranus and Neptune... 

Trafton has shown in 1964 that the opacity in the far infrared of the atmospheres of the outer planets is due to the rototranslational band of H2-H2 and H2-He pairs [393], It is now clear that collision-induced absorption plays a major role in the thermal balance and atmospheric structure of the major planets. The Voyager emission spectra of Jupiter and Saturn show dark fringes in the vicinity of the So(0) and So(l) lines of H2, Fig. 7.3, which are due to collision-induced absorption in the upper,... 

The Earth s atmosphere is composed primarily of non-polar molecules like N2 and O2, especially at greater altitudes where the H2O concentrations are small. One would therefore expect collision-induced contributions to the absorption of the Earth s atmosphere from N2-N2, N2-O2 and O2-O2 pairs. The induced rototranslational absorption of nitrogen has not been detected in the Earth s atmosphere, presumably because of strong interference by water absorption bands, but absorption in the various induced vibrational bands is well established (Tipping 1985). Titan (the large moon of Saturn) has a nitrogen atmosphere, somewhat like the Earth methane is also present. Collision-induced absorption by N2-N2 and N2-CH4 is important in the far infrared. 

A. R. W. McKellar. Experimental verification of hydrogen dimers in the atmospheres of Jupiter and Saturn from Voyager IRIS far-infrared spectra. Astrophys. J., 326 L75, 1988. 

Several applications of IR spectroscopy to astrophysics have been made. Small amounts of methane in the earth s atmosphere have been detected by the observation of weak IR absorption lines in solar radiation that has passed through the earth s atmosphere. Intense IR absorption bands of CH4 have been found in the spectra of the atmospheres of Jupiter, Saturn, Uranus, and Neptune. Bands of ammonia have been observed for Jupiter and Saturn bands of C02 have been observed in the Venusian spectrum and bands of H20 have been observed in the Martian spectrum. 

Jupiter and Uranus are outer planets composed mainly of gases. Jupiter s atmosphere contains reddish-brown clouds of ammonia. Uranus has an atmosphere made up mainly of hydrogen and helium with clouds of water vapor. This combination looks greenish to an outside observer. In addition, Mars has an atmosphere that is 95% carbon dioxide, and Venus has a permanent cloud cover of sulfur dioxide that appears pale yellow to an observer. Mercury has no permanent atmosphere. Saturn has 1 km thick dust and ice rings that orbit the planet. The eight planets in our solar system are diverse, each having different chemical compositions within and surrounding the planets. Out Earth is by far the friendliest planet for human existence. 

One can readily envisage a time, tens of billions of years from now, after the Sun has bloomed as a red giant and then died, after radiative cooling has permitted large fractions of Jupiter and Saturn to condense as liquid oceans, when most of the Solar System s planetary mass - or far more than now - finally has become habitable. These will be chemically active domains where peculiar forms of liquid water and no doubt some organic substances will be stable (Fig. 4.4) who can say what life may arise there, hundreds to thousands of kilometers below their cloud-capped atmospheric surfaces ... 

The most intriguing of Saturn s moons is Titan, larger than the planet Mercury. It is the only moon known to have an atmosphere. Nitrogen and methane gasses shroud Titan with dense clouds which our cameras cannot penetrate. The chemistry of this atmosphere is unlike that of any other. If we could descend to the surface of Titan, we might see ice mountains softly eroded by a persistent rain of complex chemicals, and a deep chemical ocean, a strange parody of the oceans of earth. Titan s atmosphere, like the ancient atmosphere of earth, contains prelife chemicals, but is too cold for life to evolve. 

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