Planet outer

The outer planets also tend to have a number of satellites with (at last count) 56 orbiting Saturn, 63 around Jupiter, 27 around Uranus, and 13 around Neptune, compared to the virtual absence of satellites in the inner planets Mercury with 0 Venus, 0 Earth, 1 and Mars 2. 

As with the inner planets, most of what scientists first learned about the outer planets came from observation using Earth-based telescopes. The data collected from these observations was of limited value because the outer planets are so much farther away than are the inner planets. For example, Jupiter is about 430 million miles (720 million km) from Earth. By comparison, the minimum distance from Earth to Mars is only about 33 million miles (56 million km). The availability of spacecraft beginning in the 1960s provided a critical new tool for the exploration of the outer planets. Today scientists have an extensive collection of data about the chemical and physical properties of the outer planets as a result of a number of space missions to one or more of the planets. 

The first such mission was Pioneer 10, launched on March 2, 1972. Pioneer 10 s mission was to fly through the asteroid belt and around Jupiter, collecting data on the planet s magnetic field, radiation belts, atmosphere, and interior. After completing this mission on March 31, 1997, the spacecraft continued in its path toward the outer limits of the solar system. It continued to send hack data on the edges of the solar system and interstellar space until April 27, 2002. At that point, its power source died out and the probe was unable to send further transmissions to Earth stations. 

Pioneer 10 was followed by its partner, Pioneer 11, launched on April 5, 1973. Like Pioneer 10, its primary objective was a study of the planet Jupiter, although it added other items to its list of accomplishments. After reaching the giant planet on December 2, 1974, it took pictures of the planet s Great Red Spot and collected data 

Both Pioneer 10 and Pioneer 11 carried plaques showing what life on Earth is like, in the hope and expectation that any other life-form in the universe with which it might come into contact would know where the probe had come from and what its inventors were like. 

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There may, of course, be types of life with a wholly different chemical basis to our own, for example, a low temperature life on the outer planets which is based on reactions in liquid ammonia. 

Effects of condensation are also seen in the bulk compositions of the planets and their satellites. The outer planets, Uranus and Neptune, have overall densities consistent with their formation from icy and stony solids. The satellites of Uranus have typical densities of 1.3g/cm which would tend to indicate a large ice com-... 

Water and carbon play critical roles in many of the Earth s chemical and physical cycles and yet their origin on the Earth is somewhat mysterious. Carbon and water could easily form solid compounds in the outer regions of the solar nebula, and accordingly the outer planets and many of their satellites contain abundant water and carbon. The type I carbonaceous chondrites, meteorites that presumably formed in the asteroid belt between the terrestrial and outer planets, contain up to 5% (m/m) carbon and up to 20% (m/m) water of hydration. Comets may contain up to 50% water ice and 25% carbon. The terrestrial planets are comparatively depleted in carbon and water by orders of magnitude. The concentration of water for the whole Earth is less that 0.1 wt% and carbon is less than 500 ppm. Actually, it is remarkable that the Earth contains any of these compounds at all. As an example of how depleted in carbon and water the Earth could have been, consider the moon, where indigenous carbon and water are undetectable. Looking at Fig. 2-4 it can be seen that no water- or carbon-bearing solids should have condensed by equilibrium processes at the temperatures and pressures that probably were typical in the zone of fhe solar... 

After planetary accretion was complete there remained two groups of surviving planetesimals, the comets and asteroids. These populations still exist and play an important role in the Earth s history. Asteroids from the belt between Mars and Jupiter and comets from reservoirs beyond the outer planets are stochastically perturbed into Earth-crossing orbits and they have collided with Earth throughout its entire history. The impact rate for 1 km diameter bodies is approximately three per million years and impacts of 10 km size bodies occur on a... 

And before all that, Tokyo its outer-planet atmosphere, the pretension of fitting into the work cycle. How inhuman does one become in an inhuman situation for a little while The nights on the trains. The airless rooms of the Akihabara English language schools. Tokyo demanded the spending of money, the saving of which was the only way out. 

The interiors of planets, moons, and many asteroids either are, or have been in the past, molten. The behavior of molten silicates and metal is important in understanding how a planet or moon evolved from an undifferentiated collection of presolar materials into the differentiated object we see today. Basaltic volcanism is ubiquitous on the terrestrial planets and many asteroids. A knowledge of atomic structure and chemical bonding is necessary to understand how basaltic melts are generated and how they crystallize. Melting and crystallization are also important processes in the formation of chondrules, tiny millimeter-sized spherical obj ects that give chondritic meteorites their name. The melting, crystallization, and sublimation of ices are dominant processes in the histories of the moons of the outer planets, comets, asteroids, and probably of the Earth. 

Laboratory experiments on the lifetime of paramagnetic species in irradiated ice, dry ice (solid C02), solid SO and CH4 have been made during the consideration of the ambient temperature of outer planets. Materials used for ESR dating, dosimetry, microscopy and assessment of the environment in earth and planetary science are summarized at the end of the chapter. 

Impurity-related defects (S03 and Cff3) Irradiation of solid C02 doped with water vapour, gaseous S02 and CH4 produces signals of impurity-related defects.124 Contamination of water gave OH radicals with similar g factors but different linewidths. Methyl radicals (CH3 ) and S02 were observed in addition to C02 and C03. H02 radicals generated by electric discharges in C02 atmosphere with moisture were observed in the dry ice frost condensed on the cold tip from the C02 atmosphere. The lifetimes of defects at ambient temperatures of outer planet were obtained by extrapolating the decay time as a function of the absolute reciprocal temperature, 1 /T.m... 

Table 1 Several ices expected in outer planet world with some impurities.

D. A. Rothery, Satellites of the Outer Planets , 1992, Clarendon Press, Oxford. 

Of a special astronomical interest is the absorption due to pairs of H2 molecules which is an important opacity source in the atmospheres of various types of cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, population III stars, etc., and in the atmospheres of the outer planets. In short absorption of infrared or visible radiation by molecular complexes is important in dense, essentially neutral atmospheres composed of non-polar gases such as hydrogen. For a treatment of such atmospheres, the absorption of pairs like H-He, H2-He, H2-H2, etc., must be known. Furthermore, it has been pointed out that for technical applications, for example in gas-core nuclear rockets, a knowledge of induced spectra is required for estimates of heat transfer [307, 308]. The transport properties of gases at high temperatures depend on collisional induction. Collision-induced absorption may be an important loss mechanism in gas lasers. Non-linear interactions of a supermolecular nature become important at high laser powers, especially at high gas densities. 

It is, therefore, noteworthy that almost immediately upon Welsh and associates discovery of collision-induced absorption in hydrogen [128, 129, 420], Herzberg found the first direct evidence of the H2 molecule in the atmospheres of the outer planets [181, 182], He was able to reproduce in the laboratory the unidentified diffuse feature at 827.0 nm observed by Kuiper in the spectra of Uranus and Neptune, using an 80 m path of hydrogen at 100 atmospheres pressure and a temperature of 78 K. The feature is the S3(0) line of the 3 — 0 collision-induced rotovibrational band of the H2 molecule [182]. 

We know today that hydrogen and helium are overwhelmingly the most abundant species in the atmospheres of the outer planets, but direct evidence for their presence was virtually absent prior to the work mentioned [145]. Supermolecular spectroscopy had to be discovered before such evidence could be understood and it comes as no surprise that soon after Welsh s discovery many other uses of collision-induced absorption were pointed out in various astrophysical studies. Supermolecular absorption and emission have become the spectroscopy of the neutral, dense regions, especially where non-polar gases prevail. 

Trafton has shown in 1964 that the opacity in the far infrared of the atmospheres of the outer planets is due to the rototranslational band of H2-H2 and H2-He pairs [393], It is now clear that collision-induced absorption plays a major role in the thermal balance and atmospheric structure of the major planets. The Voyager emission spectra of Jupiter and Saturn show dark fringes in the vicinity of the So(0) and So(l) lines of H2, Fig. 7.3, which are due to collision-induced absorption in the upper,... 

A. Borysow and L. Frommhold. Theoretical collision induced rototranslational absorption spectra for the outer planets H2-CH4 pairs. Astrophys. J., 304 849, 1986. 

L. Trafton. Observational studies of collision induced absorption in the atmospheres of the outer planets. In J. Szudy, ed., Spectral Line Shapes 5, p. 755, Ossolineum, Warsaw, 1989. 

A (gas) clathrate hydrate is a crystalline compound which can be obtained by the formation of a hydrogen-bonded host lattice around one or more species of guest molecules. It s a pleasing thought to a crystallographer that when it snows on the outer planets it might snow gas hydrates. (Jeffrey and McMullan, 1967.)... 

Oxygen is the most abundant element in the Earth s crust and accounts for 23 % of the mass of the atmosphere. In fact, Earth is the only planet in the solar system with an oxidizing atmosphere. On Mars, oxygen provides only 0.15% of the atmospheric mass and in the atmospheres of the outer planets, oxygen is essentially nonexistent. In the hot atmosphere of Venus, the oxygen has reacted and is present mainly as carbon dioxide. In that form, and as certain other gaseous oxides, it contributes to the warming of the planet (Box 15.1). 

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. 

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. 

Among places where condensates accreted into significant solid bodies, such as planets, habitable realms have always been rarer than places that were either too cold or too hot for life to exist. Much of our Solar System s mass is still far too hot for life. Most of the deep interiors of the gas giants and rocky planets are too hot, as is, of course, the Sun itself. Most of the surface area of solid bodies in the Solar System are too cold - the icy satellites of the outer planets and the myriad comets and Kuiper Belt Objects on the far outer fringes of the Solar System. In this sense, places like the surfaces of Earth and Mars and Europa s subsurface ocean are indeed very rare places. 

According to the foregoing analysis, conformers such as gauche- and anri-butane or chair and twist-boat cyclohexane would be considered to be diastereomers of each other. However, under most conditions these conformers interconvert so rapidly that butane and cyclohexane are considered to be single species and not mixtures of stereoisomers. When we have to write chemistry books for people living on the outer planets of the solar system, we might have to modify these concepts. 

But what was there, in addition to water, on the primitive Earth The four outer planets of the solar system (Jupiter, Saturn, Uranus and Neptune) are still made up mainly of hydrogen, helium, methane, ammonia and water, and it is likely that those same chemicals were abundant everywhere else in the solar system, and therefore even in its four inner planets (Mercury, Venus, Earth and Mars). These were too small to trap light chemicals, such as hydrogen and helium, but the Earth had a large enough mass to keep all the others. It is likely therefore that the Earth s first atmosphere had great amounts of methane (CH4), ammonia (NHJ and water, and was, as a result, heavy and reducing, like Jupiter s. 

Figure 2-54 shows Kepler and his planetary model based on the regular solids [84], According to this model the greatest distance of one planet from the sun stands in a fixed ratio to the least distance of the next outer planet from the sun. There are five ratios describing the distances of the six planets which were known to Kepler. A regular solid can be interposed between two adjacent planets so that the inner planet, when at its greatest distance from the sun, lays on the inscribed sphere of the solid, while the outer planet, when at its least distance, lays on the circumscribed sphere. 

Clathrate hydrates have been found to occur naturally in large quantities. Around 120 X 10 m (at STP) of methane is estimated to be trapped in deposits of the deep ocean floor [10]. Clathrate hydrates are also suspected to occur in large quantities on some outer planets, moons, and trans-Neptunian objects [11]. In the petroleum industry, hydrocarbon clathrate hydrates are a cause of problems because they can form inside gas pipelines, often resulting in plugging. Deep sea deposition of carbon dioxide clathrate hydrate has been proposed as a method to remove this greenhouse gas from the atmosphere and control climate change [12]. 

Reactions of C with H, H2 are of fundamental importance to the carbon chemistry in interstellar clouds, and some of the reaction paths prevalent in dense interstellar clouds may also be of significance in the reducing atmospheres of the outer planets. These reactions initiate a complex sequence which produce CH, CH and lead eventually to molecules such as CH, These molecules are important pre-... 

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