Uranus atmosphere

Uranus The temperature in the Uranus atmosphere, which consists of molecular hydrogen containing around 12% helium, is close to 60 K. A methane cloud layer has been detected in the lower layers of this atmosphere. The planet is surrounded by a magnetosphere which extends into space for about ten times the diameter of Uranus. The planet has 27 moons of various sizes and is surrounded by a ring system which consists of thin dark rings. The planet is unusual in two respects its tilted axis and retrograde rotation. 

There has been no detection of the methyl radical in Uranus atmosphere, but an upper limit of. 05 ppbv has been set (40). 

The radio emissions from Uranus arise from sufficient depths that collision-induced absorption by hydrogen is an important source of opacity at millimeter wavelengths. Ammonia is severely depleted in Uranus atmosphere, at least at pressure levels less than 25 bar. Since, based upon planet formation theories, nitrogen must be present in at least solar proportions, it is believed that ammonia gas is abundant at deeper levels, but reacts with H2S to form a cloud of NH4SH. If indeed this process accounts for the observed depletion in NH3, hydrogen sulfide should be enriched in Uranus atmosphere by about an order of magnitude over solar S. Such an abundance of H2S itself will contribute to the radio opacity in Uranus atmosphere and actually help reconcile observed spectra with models. 

Flasar, F. M., Conrath, B. J., Gierasch, P. J., Pirraglia, J. A. (1987). Voyager infrared observations of Uranus atmosphere thermal structure and dynamics. Journal of... 

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... 

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... 

It is, therefore, noteworthy that almost immediately upon Welsh and associates discovery of collision-induced absorption in hydrogen [128, 129, 420], Herzberg found the first direct evidence of the H2 molecule in the atmospheres of the outer planets [181, 182], He was able to reproduce in the laboratory the unidentified diffuse feature at 827.0 nm observed by Kuiper in the spectra of Uranus and Neptune, using an 80 m path of hydrogen at 100 atmospheres pressure and a temperature of 78 K. The feature is the S3(0) line of the 3 — 0 collision-induced rotovibrational band of the H2 molecule [182]. 

Herzberg was able to point out another line at 816.6 nm which he identified as a double transition, partially overlapped by an adjacent CH4 band in the Uranus spectra. In the laboratory spectra recorded with unmixed hydrogen, this double transition was relatively strong, but in the photographic plates of Uranus the feature was much weaker relative to the S3(0) line. This observation led Herzberg to conclude that sizeable He concentrations exist in these atmospheres (albeit the estimates of [He] [H2] abundance ratio seem high), because the S3(0) feature is enhanced by the presence of He, but H2-He pairs cannot undergo double transitions these features thus appear weak in Kuiper s plates relative to the S3(0) feature. 

G. Herzberg. Spectroscopic evidence of molecular hydrogen in the atmospheres of uranus and neptune. Astrophys. J., 115 337, 1952. 

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. 

A child on the planet Uranus would ask the question, Why is the sky green A child on Jupiter would ask the question, Why is the sky reddish brown How would you answer these questions Relate your answer to the chemical composition of the atmospheres of these planets. 

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. 

But what was there, in addition to water, on the primitive Earth The four outer planets of the solar system (Jupiter, Saturn, Uranus and Neptune) are still made up mainly of hydrogen, helium, methane, ammonia and water, and it is likely that those same chemicals were abundant everywhere else in the solar system, and therefore even in its four inner planets (Mercury, Venus, Earth and Mars). These were too small to trap light chemicals, such as hydrogen and helium, but the Earth had a large enough mass to keep all the others. It is likely therefore that the Earth s first atmosphere had great amounts of methane (CH4), ammonia (NHJ and water, and was, as a result, heavy and reducing, like Jupiter s. 

The chemical dynamics, reactivity, and stability of carbon-centered radicals play an important role in understanding the formation of polycyclic aromatic hydrocarbons (PAHs), their hydrogen-dehcient precursor molecules, and carbonaceous nanostructures from the bottom up in extreme environments. These range from high-temperature combustion flames (up to a few 1000 K) and chemical vapor deposition of diamonds to more exotic, extraterrestrial settings such as low-temperature (30-200 K), hydrocarbon-rich atmospheres of planets and their moons such as Jupiter, Saturn, Uranus, Neptune, Pluto, and Titan, as well as cold molecular clouds holding temperatures as low as 10... 

Hydrogen gas has been found occluded in meteorites, and also is present in nebulae, fixed stars, and in the Sun. Anders and Grevesse calculated mass fractions of H, He, and heavier elements (Li-U) in the solar system, and derived values of 70.683, 27.431, and 1.886%, respectively. The major planets (Jupiter, Neptune, Saturn, and Uranus) contain large amounts of hydrogen in their atmospheres, along with He, CH4, and NH3. 

A more likely scenario is that Uranus and Neptune, along with the cores of Jupiter and Saturn, formed in the region 5-10 AU from the Sun. Such a system would have remained dynamically stable until one object (Jupiter) accreted a large H/He-rich atmosphere. At this point at least two of the other bodies would have been permrbed into the region beyond 15 AU. Gravitational interactions with planetesimals in the outer solar system would then have circularized the orbits of Uranus and Neptune by dynamical friction, while at the same time scattering most of these planetesimals onto... 

The temperature profiles within Jupiter and Saturn are thought to be essentially adiabatic, reflecting the high central temperatures and the dominant role of convection below the observable atmosphere where radiative processes become important. There may be deeper layers restricted in radial extent where the temperature profile becomes subadiabatic, due to a decrease in the total opacity, or by virtue of the behavior of the equation of state of hydrogen and helium. The same may hold for Uranus and Neptune, although with less certainty, because of the possibility that stable compositional gradients could exist and dominate the heat flow regime. In particular, Uranus small heat flow, if primordial and not a function of seasonal insolation, could be the result of a stable compositional stratification and hence subadiabatic temperature profile in the interior (Podolak et al., 1991). 

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