Venus densities

Venus Flytrap Module Very Long-chain Acyl-CoA Synthetase Very Low-density Lipoprotein Vesicle... 

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. 

Venus atmosphere consists mainly of CO2 of high density. It is perhaps the least well understood atmosphere, because the existing laboratory studies of collision-induced absorption in carbon dioxide and the theoretical analyses attempted have revealed some unexpected complexity. Some of the problems mentioned have to do with the strong ternary components observed furthermore, the pair interaction is strongly anisotropic and the anisotropy has never been accounted for. More work is required for a better understanding (Tipping 1985). 

The properties of supercritical fluids are generally different from those of regular fluids. For example, supercritical water is relatively nonpolar and acidic. Further, the properties of a supercritical fluid, such as its density and viscosity, change with changing pressure and temperature, dramatically as the critical point is approached. Thus, carbon dioxide is not listed in Table 6.1 because it has no liquid phase at terran atmospheric pressure. Carbon dioxide has a critical temperature of 304.2 K and pressure of 73.8 atm, however. It is therefore a supercritical fluid above that pressure, and may even exist as a potential biosolvent for rocky planets having the approximate mass of Earth (or Venus). 

The terrestrial planets and the Moon are differentiated, with dense iron-rich cores and rocky mantles. The uncompressed densities of Earth and Venus are similar. Mercury has a high density which suggests it has relatively large core. Conversely, the Moon has a low density, indicating a very small core. There is little observational evidence that asteroids are differentiated except for Vesta and Ceres (Thomas et al. 2005). However, iron meteorites from the cores of differentiated asteroids are quite common, and the irons found to date come from several dozen different parent bodies (Meibom Clark 1999). Most meteorites come from asteroids that never differentiated. These chondritic meteorites consist of intimate mixtures of heterogeneous material millimeter-sized rounded particles that were once molten, called chondrules, similarly sized calcium-aluminum-rich inclusions (CAIs), and micrometer-sized matrix grains. 

All of the clouds are low density, because the visibility inside the densest region of the clouds is a few kilometers. The average and maximum optical depths (t) in visible light of all cloud layers are 29 and 40, respectively, versus average and maximum t values of 6 and 350 for terrestrial clouds. Average mass densities for Venus clouds are 0.01-0.02 g m versus an average mass density of 0.1-0.5 g m for fog clouds on Earth. Venus cloud layers are typically divided into the subcloud haze (32-48 km), the lower cloud (48-51 km), middle cloud (51-57 km), upper cloud (57-70 km), and upper haze (70-90 km). 

Nephelometers, which use scattered light to measure particle size and number density, on Venera 9-11 and Pioneer Venus showed that the cloud layers are composed of three different types of particles. The first type are aerosols of 0.3 p.m diameter (mode-1 particles), which occur in the... 

Table 5 lists the seven Venera and Vega space probes that made elemental analyses of the surface of Venus. In addition to elemental analyses, several of the Venera and Vega landers measured density, bearing capacity, electrical resistivity, and atmospheric redox state (via the reaction of chemically impregnated asbestos with atmospheric CO). The Venera 8-10, and Vega 1-2 probes analyzed... 

Further support for solar nebular fractionation comes from the compilation of Brown and Mussett (1993) who showed that the terrestrial planets have densities, which when corrected for their different internal pressure, vary significantly from that of chondritic meteorites. In fact Mars with an uncompressed density of ca. 3.7 Mg.m-3 is the only planet which lies in the chondritic range of 3.4—3.9 Mg.m-3. Earth, Venus, and Mercury are denser than chondrites and the Earth s Moon is less dense. These compositional differences are thought to reflect differences in the Fe/Si ratio between the different planets, which in turn reflects the fractionation of Fe from Si in relation to proximity to the Sun, during the condensation of the solar nebula, further supporting the view that the silica-depletion relative to chondrite took place in the solar nebula. 

Venus s atmosphere is predominantly a combination of clouds and haze that extends from an altitude of about 18 miles (30 km) above the planet s surface to an altitude of more than 50 miles (80 km). Its structure appears to consist of three parts. Closest to the surface is a haze of roughly constant density, extending from the bottom of the cloud to an altitude of about 18 miles (30 km). Next is the most obvious layer, a fairly dense, sharply defined cloud at an altitude of about 30 miles (50 km). This cloud consists primarily of droplets of sulfuric acid. Finally, a haze that gradually becomes thinner with altitude is located above the middle cloud to an altitude of about 50 miles (80 km). The density of the Venusian cloud structure at various altitudes is shown in the graph on page 102. 

The composition of the outer planets is also very different from that of the inner planets. Mercury, Venus, Earth, and Mars are all made of rocky-like material with a density of about 5.5 g/cm3. By contrast, the outer planets seem to consist largely of gases (which accounts for their sometimes being called the gas giants) with densities of about 0.69 g/cm3 for Saturn to 1.54 g/cm3 for Neptune. These... 

Fig.31. DlustntionoftheC-rprofilingtechiiiqueforobtaiiiiiig p)inuiidopedfiIm. (a) 100 Hz capacitance venus temperatuie data for reverse bias voltages 2 V (O) and 4 V ( ) in a tyjrical higb-resistivity undoped a-Si H film, (b) Replot of the above data in the form C [dC/

The ionosphere of Venus is the most explored and best understood one in our solar system besides that of the earth. The atmosphere at the surface of Venus consists of approximately 96.5% CO2 and 3.5% N2. Photodissociation of CO2 results in atomic oxygen becoming the major atmospheric constituent above about 150 km. The behavior of the ionosphere of Venus is controlled by chemical processes below an altitude of about 180 km. This region of the ionosphere is analogous to the terrestrial E-region fi om the point of view that the main ion is molecular and is under chemical control. However, unlike the earth the maximum plasma density peaks near an altitude of 140 km (see Fig. 14), and is the result of a peak in the photoionization rate. Venus is an excellent example of the importance of chemical processes in establishing the nature of some of the important aspects of an ionosphere. The ion with the largest density is Oj, and yet there is practically no neutral O2 in the upper atmosphere. As mentioned earlier, the major neutral gas constituents in the upper atmosphere are CO2 and O. The photoionization of these neutral gas species is followed by the reactions indicated below, which very effectively turn these initial ions into 02" ... 

FIGURE 14 Ion densities measured by the ion mass spectrometer during one orbit of the Pioneer Venus orbiter spacecraft. [Bauer, S. J., Donahue, T. M., Hartle, R. E., and Taylor, H. A. (1979). Science 205,109.]... 

At altitudes above about 200 km, transport processes control the distribution of the electron and ion densities. Venus does not have an intrinsic magnetic field therefore, horizontal transport at mid- and high latitudes is not impeded as is the case on the earth. The lack of an intrinsic field also means that processes associated with transport between magnetically conjugate ionospheres do not take place. The density of 0+ ions has a peak near 200 km, which is an F2 type of peak, and is the major ion above this altitude, as shown in Fig. 14. 

The periodic table set iron s density, abundance, and solidity, which created this shield. Mars, Venus, and Titan currently have no magnetic field, which lets the solar wind destroy gas molecules like water. (Mars had one but lost it.) The gas giant planets have magnetic fields from the flow of gas, but only Earth has enough flow inside itself to be both rocky and magnetic for billions of years. 

Agreement with the limited data for Mars is readily achieved (Fox and Dalgarno 1979). For Venus the agreement between the model ion densities and the measurements is broadly satisfactory when reactions of metastable ions are included (Fox 1982b) though there is a tendency for the models to underestimate the C+ densities (Paxton 1985). The charge transfer reaction... 

Recent discoveries by ground based observations, as well as the Corot and Kepler space-missions, found planets with masses below 10 MEarth and densities akin to Neptune as well as Earth, suggesting that there is not one cut-off mass above which a planet is like Neptune and below which it is rocky like Earth or Venus. Note that the term Mini-Neptune is used for small extrasolar giant planets, not mini-Uranus, even though Uranus is the less massive planet (17.1 and 14.5 Earth masses. 

Space probes into Venus have shown that its atmosphere consists mostly of carbon dioxide. At the surface of Venus the temperature is 460°C and the pressure is 75 atm. Compare the density of CO2 on Venus surface to that on earth s surface at 25°C and one atmosphere. 

Terrestrial planets have a solid surface, are differentiated (lighter elements near the surface, heavier elements in the core) and have relatively high densities. The main spectral signatures between 8 and 20 pm in the atmosphere of Venus Earth and Mars are shown in Fig. 3.1. 

Vertical distributions of the molecular density and mixing ratios of H2O and HDO in the Venus mesosphere were measured by Fedorova et al., 2008 [129]. The experiment was carried out on board of Venus express mission (SOIR instrument, 2.32-4.35 pm). The atmosphere was sounded during solar occultation in the range of altitudes from 65 to 130 km. An enrichment of D to hydrogen indicates the escape of water from Venus. Bertaux et al., 2007 [25] report on the detection of a warm layer at 90-120 km. ... 

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