Jupiter, atmosphere

Figure 15. Jupiter atmospheric Xe composition measured by the Galileo Probe mass spectrometer (Mahaffy et al. 2000), calculated as the abundance of each isotope M divided by the total abundance for all M and plotted relative to the NEA-Xe composition (Table 1) represented in the same way. The five most abundant Jovian Xe isotopes are indicated by the shaded symbols. U-Xe, SW2-Xe, and AVCC-Xe compositions in Table 1 are shown for comparison in the same representation. The data indicate deficits at the two heaviest isotopes relative to NEA-Xe and AVCC-Xe, but uncertainties are too large to rule between SW-Xe and U-Xe as the Jovian composition.

Jupiter is the largest planet within the solar system (Fig. 3.14). Its mass is 2.5 times the mass of all other planets in the solar system. Jupiter s atmosphere is composed of about 88-92% of hydrogen and 8-12% of helium. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, methane, water vapor, ammonia, silicon-based compound and also phosphine and sulfur. Helium in the Jupiter atmosphere is depleted (compared with the composition of the primordial solar nebula). This can be explained by a precipitation of the helium into the interior of the planet. The composition of Saturn is similar to that of Jupiter, Uranus and Neptune have much less hydrogen and helium. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Alkanes have the general molecular- formula C H2 +2- The simplest one, methane (CH4), is also the most abundant. Large fflnounts are present in our atmosphere, in the ground, and in the oceans. Methane has been found on Jupiter, Saturn, Uranus, Neptune, and Pluto, and even on Halley s Comet. 

Nitrogen is considered to be a likely constituent of the atmosphere of Jupiter, though it is undetected as yet. As a chemist, would you expect oxygen also to be an important constituent of Jupiter s CH -NH3 atmosphere ... 

The giant planets possess low surface temperatures and have atmospheres that extend several thousand miles. The markings on Jupiter, the largest planet, consist of cloud formations composed of methane containing a small amount of ammonia. The atmosphere of Jupiter absorbs the extreme red and infrared portions of the spectrum. These absorptions correspond to the absorption spectra of ammonia and methane, suggesting the presence of these gases in Jupiter s... 

S2O and the polysulfuroxide formed from it are also suspected to be components of the surface and the atmosphere of Jupiter s moon lo [22], and S2O has been detected in the atmosphere of the planet Venus [23]. 

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. 

The planet Jupiter occupies a special position in the solar system. It is the largest and heaviest planet, with a mass of 1/1,047 that of the sun. Jupiter consists almost solely of hydrogen and helium with a ratio similar to that found in the sun itself He H 1 10. Small amounts of some heavier elements are present, such as B, N, P, S, C and Ge. The density of Jupiter has been calculated as 1,300 kg/m3. Its atmosphere can be divided into three zones (starting from the outermost) ... 

In 1994, a unique incident occurred the impact of the Shoemaker-Levy comet on the Jovian atmosphere. Die strong gravitational field of Jupiter caused the comet to break up before it could enter the atmosphere, and the parts of the comet crashed separately into the atmosphere one after the other. This unique spectacle was observed by many observatories and also by the Galileo spacecraft and the Hubble telescope. It led to the discovery of yet another phenomenon the most intensive aurora effects in the solar system, observed at Jupiter s poles. Astronomers assume that the energy for these comes from the planet s rotation, possibly with a contribution from the solar wind. This process differs from that of the origin of the aurora on Earth, where the phenomenon is caused by interactions between the solar wind and the Earth s magnetic field. 

Using the Hubble telescope, the extrasolar planet HD 209458b (a gas planet with 0.7 times the mass of Jupiter) has been shown to have an extensive external atmosphere consisting of atomic hydrogen it is possible that the hydrogen is escaping from the planet (Vidal-Madjar et al., 2003). 

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

For many years, meteorites have provided the only means to determine the abundance of 3He in protosolar material. The values obtained by mass spectroscopy techniques in the so-called planetary component of gas-rich meteorites have been critically examined by Geiss (1993) and Galli et al. (1995). The latter recommend the value 3He/4He= (1.5 0.1) x 10-4. The meteoritic value has been confirmed by in situ measurement of the He isotopic ratio in the atmosphere of Jupiter by the Galileo Probe Mass Spectrometer. The isotopic ratio obtained in this way, 3He/4He= (1.66 0.04) x 10 4 (Mahaffy et al. 1998), is slightly larger than, but consistent with, the ratio measured in meteorites, reflecting possible fractionation in the protosolar gas in favor of the the heavier isotope, or differential depletion in Jupiter s atmosphere. 

Fig. 1. Evolution of 3He/H in the solar neighborhood, computed without extra-mixing (upper curve) and with extra-mixing in 90% or 100% of stars M < 2.5 M (lower curves). The two arrows indicate the present epoch (assuming a Galactic age of 13.7 Gyr) and the time of formation of the solar system 4.55 Gyr ago. Symbols and errorbars show the 3He/H value measured in meteorites (empty squares) Jupiter s atmosphere (errorbar) the local ionized ISM (filled triangle) the local neutral ISM (filled circle) the sample of simple Hll regions (empty circles). Data points have been slightly displaced for clarity. The He isotopic ratios has been converted into abundances relative to hydrogen assuming a universal ratio He/H= 0.1. See text for references.

The period of emergence of life on Earth is constrained to be between the period 4.0-3.7 Gyr ago, for which there is no fossil record. Urey postulated that all of the planets formed from the same solar nebula and so the early Earth should have an atmosphere with a composition the same as that of Jupiter (known at the time),... 

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. 

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