Venus chemical composition

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. 

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. 

One important point should be emphasized here. This is the paucity of spacecraft data on the chemical composition and thermal structure of Venus lower atmosphere below —22 km altitude (von Zahn et al., 1983). About 80% of Venus atmospheric mass is below this altitude. Furthermore, altitudes of 0-12 km span the region where the atmosphere is interacting with the surface. However, with three exceptions we have no data on the chemical composition of Venus nearsurface atmosphere. First is the older measurements of CO2 and N2 from crude chemical experiments on the Venera 4-6 landers. Second, the water-vapor profile measured by the Pioneer Venus large probe neutral mass spectrometer. Third, the measurements of water-vapor and gaseous sulfur by spectrophotometer experiments on the Venera II-I4 landers. The gas chromatograph and mass spectrometer experiments on... 

The chemical composition of Venus atmosphere is described below. This discussion is based on sources listed in Table 3, Fegley and Treiman (1992), and Warneck (1988). 

The most recent mission to Venus is the European Space Agency s Venus Express spacecraft, launched on November 5, 2005. The spacecraft reached the planet in April 2006 and settled into orbit on May 6. It has now transmitted some of the best images of and data about the planet s atmosphere ever obtained, including the first images ever of its south pole. Among the new data transmitted by Venus Express are the chemical composition of the lower atmosphere, temperature variations at different levels of the atmosphere, temperature measurements of the planet s surface, and reactions between oxygen and nitrogen oxides in the middle and upper atmosphere. 

Data about the chemical composition of Venus s surface come from a number of sources. For example, the planet s surface is so hot that it radiates energy in the infrared range with an intensity that can be detected from Earth and from spacecraft orbiting... 

Venus. Reports of the chemical composition of the surface and nearsurface regions of the planet, as measured by Earth-based instruments, were reported as early as the mid-1990s. The Galileo and Cassini spacecraft collected similar data in the 1 mm region of the EM spectrum during their flybys of the planet in 1990 and 1998, respectively. 

The most direct information about the planet s surface comes from several Soviet Venera landers that reached the surface and conducted a number of surveys before they were destroyed by the planet s inhospitable climate. Venera 8, 9, 10, 13, and 14 all successfully landed on Venus and sent hack at least some data on its chemical composition. All hut the first of these probes also transmitted images of the planet s surface. 

The most complete and reliable data about the chemical composition of the Venusian surface comes from three Soviet missions, the Venera 13, Venera 14, and Vega 2 probes. These spacecraft actually reached the planet s surface and conducted studies of elements and compounds present on the planet s surface. In atypical experiment, one of the lander s tools would drill a hole into the planet s surface about 1.2 inches (3 cm) deep and extract a sample about 1 cm3 in volume. The chart on page 110 summarizes data obtained from these three missions and gives the composition of Earth s continental crust for purposes of comparison. Notice that the major differences in crustal composition between the two planets appears to be in the relative abundance of Si02 (45.6 percent on Venus compared with 60.2 percent on Earth) and of MgO (about 11.5 percent on Venus compared with 3.1 percent on Earth). Otherwise, the two planets do indeed appear to be almost "sister planets," at least with regard to the composition of their outer crusts. 

Table II gives the chemical composition of Venus atmosphere, which is dominantly CO2 with 3.5% of N2 and smaller amounts of SO2, H2O, CO, and many reactive trace gases. The probable major sources and sinks for each gas are given in Table II. The gas abundances are taken primarily from (II), with new values for H2SO4 (12) and NO (13). Chemistry in Venus lower atmosphere is driven by high temperatures (740 K) and pressures (95 bars) generated by the...

The chemical composition of the Martian atmosphere is given in Table VI, along with plausible sources and sinks. The abundances are taken primarily from (75), with new abundances for He 20), H2 and HD (27), H2O2 22, 23), and CH4 24). The Martian atmosphere is dominantly CO2, which is continually converted to O2 and CO by solar UV light. However, as on Venus, the observed abundances of CO2, O2, and CO cannot be explained simply by the direct recombination of CO and O atoms to CO2 because this reaction is too slow to maintain the high CO2 and low CO and O2 abundances. Instead, OH radicals produced from atmospheric water vapor by UV photolysis or by reaction with electronically excited O atoms enter into catalytic cycles such as that shown in Table VII, which recombine CO and O atoms to CO2. 

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. 

At this point, it is impossible to assess the likelihood of this, or almost any other hypothesized reaction. The problem is that scientists still lack sufficient data to build models about the structure and composition of Venus s atmosphere and surface and of possible chemical interactions among the components of both. It is for this reason that Venus scholars look forward so eagerly to the results of the Venus Express mission currently under way. The results of that mission should provide much of the data needed about Venus s atmosphere... 

Any body in our solar system that has a surrounding neutral gas envelope, due either to gravitational attraction (e.g., planets) or some other processes such as sputtering (e.g., Europa) or sublimation (comets), also has an ionosphere. The very basic processes of ionization, chemical transformation, and diffusive as well as convective transport are analogous in all ionospheres the major differences are the result of the background neutral gas compositions, the nature or lack of a magnetic field, and the differences in some of the important processes (e.g., photo versus impact ionization). The remainder of this chapter describes the characteristics of the Venus ionosphere as a representative example of the so-called inner or terrestrial planets, the ionosphere of Jupiter as representative of the outer or major planets, and finally the ionosphere of Titan to represent one of the moons in our solar system. 

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