Major planets giants

Table 14.3 Abundances of major elements and molecules in the atmospheres of the giant planets, relative to solar abundances (Lunine, )...

The giant-impact theory has been confirmed by a number of important observations. Perhaps most importantly, we know now that the Moon must have formed tens of millions of years after the start of the solar system (Lee et al, 1997 Halliday, 2000). This is consistent with a collision between already formed planets. The masses of the Earth and the impactor at the time of the giant impact have been the subject of major uncertainty. Two main classes of models are usually considered. In the first, the Earth was largely (90%) formed at the time of the impact and the impacting planet Theia was roughly Mars-sized (Cameron and Benz, 1991). A recent class of models considers the Earth to be only half-formed at the... 

Major Satellites of the Giant Planets Table 1 Satellite properties. 

Comet-like materials are presumed to be the budding blocks of Uranus and Neptune (the ice giants) they may have played a role in the formation of Jupiter and Saturn (the gas giants) and they also played some role in transporting outer solar system volatile materials to inner planets (Delsemme, 2000). The inner solar system flux of comets may have been much higher in the past and comets may have played a role in producing the late heavy bombardment on terrestrial planets (Levison et al., 2001). Comets also exist outside the solar system and there is good evidence that they orbit a major fraction of... 

Figure 18 D/H ratios of several comets compared to the oceans (SMOW), planets, the solar nehula (PSN), and the interstellar medium. Low-temperature fractionation processes increase D/H. Jupiter and Saturn have compositions close to the original nehular composition, hut low-temperature formation of ice caused the enhancements seen in Uranus and Neptune (the ice giants) and comets. The discrepancy between the plotted LP comets and SMOW argues against these comets providing Earth with a major fraction of its water. Other comets, formed in warmer environments, near Jupiter, could he more similar to SMOW (source Huehner, 2002).

It includes chapters on the origin of the elements and solar system abundances, the solar nebula and planet fomiution. meteorite classitlcation. the major types of meteorites, important processes in early solar system history, geochemistry of the terrestrial planets, the giant planets and their satellites, comets, and the formation and early differentiation of the Earth. This volume is intended to be the first reference work one would consult to learn about the chemistry of the solar system. 

The very stable molecules CO (observed) and N2 (not observable) are the major C-, 0-, and N-bearing gases throughout the entire CSE, as expected from thermochemical equilibrium. Under the low total pressures in the CSE, conversions of CO to CH4 or N2 to NH3 as the major C- or N-bearing gases does not occur. Even if pressure conditions were favorable, these reactions would not reach equilibrium because they are kinetically inhibited (these conversions are quenched even in the much denser giant planet atmospheres (e.g., 54). This does not mean that CH4 or NH3 should be absent from the CSE it only means that their abundances are likely less than that expected from thermochemical equilibrium. In 0-rich CSE, most oxygen is evenly distributed between CO and H2O, but CO2, produced by the rapid water gas reaction (CO + H2O = H2 + CO2) is also an abundant gas (54) and has been observed. 

The next major breakthrough came in the 1950 s with the development of rocket technology and spacecraft design. For the first time, scientists were able to extend their observations beyond Earth s atmosphere and send instruments to the Moon and to various planets. By 1989, all the gas giant planets had been visited by spacecraft, leaving only Pluto as an unexplored world. In addition to gathering an enormous amount of data on each of these planets, the... 

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