Venus, composition

In the region of the terrestrial planets, there may have been several thousand planetesimals of up to several hundred kilometres in diameter. During about ten million years, these united to form the four planets—Mercury, Venus, Earth and Mars—which are close to the sun. Far outside the orbit of the planet Mars, the heavier planets were formed, in particular Jupiter and Saturn, the huge masses of which attracted all the hydrogen and helium around them. Apart from their cores, these planets have a similar composition to that of the sun. Between the planets Mars and Jupiter, there is a large zone which should really contain another planet. It... 

The special position of the Earth among the terrestrial planets is also shown by the availability of free water. On Venus and Mars, it has not until now been possible to detect any free water there is, however, geological and atmospheric evidence that both planets were either partially or completely covered with water during their formation phase. This can be deduced from certain characteristics of their surfaces and from the composition of their atmospheres. The ratio of deuterium to hydrogen (D/H) is particularly important here both Mars and Venus have a higher D/H ratio than that of the Earth. For Mars, the enrichment factor is around 5, and in the case of Venus, 100 (deBergh, 1993). 

Now, apart from the planets, many meteorites were formed, moving in quite different orbits and of quite different chemical composition. In particular, the so-called C-l meteorites composed of carbonaceous chondrites have a composition of elements much closer to that of the Sun. It is proposed (see for example Harder and also Robert in Further Reading) that many of these meteorites collided with very early Earth and became incorporated in it, so that eventually some 15% of Earth came from this material (see Section 1.11). Other planets such as Mars and the Moon could have had similar histories, but the remote planets and Venus are very different. 

The density estimates in Table 7.1 show a distinction between the structures of the planets, with Mercury, Venus, Earth and Mars all having mean densities consistent with a rocky internal structure. The Earth-like nature of their composition, orbital periods and distance from the Sun enable these to be classified as the terrestrial planets. Jupiter, Saturn and Uranus have very low densities and are simple gas giants, perhaps with a very small rocky core. Neptune and Pluto clearly contain more dense materials, perhaps a mixture of gas, rock and ice. 

Hoffman JH, Hodges RR, McElroy MB, Donahue TM, Kolpin M (1979) Composition and structure of the Venus atmosphere results from Pioneer Venus. Science 205 49-52 Hoffman PE, Kaufman AJ, Halverson GP, Schrag DP (1998) Neoproterozoic snowball earth. Science 281 1342-1346... 

Venus is completely covered with dense clouds. The composition of the clouds has been the subject of much speculation for many years. It includes ice, carbon suboxide, sulfuric acid, hydrocarbons, mercuric chloride, ammonium chloride, and hydrated ferrous chloride. Recently, Young (1066a) has proposed, based on refractive index measurement, that the clouds are composed most probably of droplets of 75% H2S04. 

The atmospheric composition of Venus is similar to that of Mars (see Table VIII—3). Carbon dioxide is the main constituent. The CO mixing ratio is about 5 x 10"5, but the Oz mixing ratio is less than 10 6. Minor constituents that are present in the Venus atmosphere but not in the Martian atmosphere are HC1 and HF in mixing ratios of 6 x 10 7 and 1.5 x 10 9, respectively. 

The atmospheric composition of Jupiter is much different from tlx --< of Mars and Venus. It is similar to the primitive stellar atmospheres. I In... 

The necessary starting point for any study of the chemistry of a planetary atmosphere is the dissociation of molecules, which results from the absorption of solar ultraviolet radiation. This atmospheric chemistry must take into account not only the general characteristics of the atmosphere (constitution), but also its particular chemical constituents (composition). The absorption of solar radiation can be attributed to carbon dioxide (C02) for Mars and Venus, to molecular oxygen (02) for the Earth, and to methane (CH4) and ammonia (NH3) for Jupiter and the outer planets. 

Nishikawa, O., Okrugin, V., Belkova, N. et al. (2006) Crystal symmetry and chemical composition of yukonite TEM study of specimens collected from Nalychevskie hot springs, Kamchatka, Russia and from Venus mine, Yukon Territory, Canada. Mineralogical Magazine, 70(1), 73-81. 

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. 

Morgan J. W. and Anders E. (1980) Chemical composition of Earth, Venus, and Mercury. Proc. Natl. Acad. Sci. 77, 6973-6977. 

Surkov Yu. A., Barsukov V. L., Moskalyeva L. P., Kharyukova V. P., and Kemurdzhian A. L. (1984) New data on the composition, structure, and properties of Venus rock obtained by Venera 13 and Venera 14. Proc. 15th Lunar Planet. Sci. Conf J. Geophys. Res. 89, 393-402. 

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