Titan, Solar System

Of the three extraterrestrial targets in our solar system, the Saturnian moon Titan is the least likely to provide signs of life. To quote Christopher McKay from the NASA Ames Research Center, Titan is an interesting world. For example, its organic haze layer could be an example of the prebiotic chemistry which led to life on Earth . Direct links to extraterrestrial life have not, however, yet been found, as water (one of the main preconditions for life) has not been detected on Titan, apart from traces of water vapour in the higher layers of the Titanian atmosphere (Brack, 2002). 

Concepts Titan - the test case Physical and chemical properties of the only other body in our solar system with a significant atmosphere... 

Consideration, in view of the discovery of evidence of liquid water-ammonia eutectics on Titan and active water geysers on Saturn s moon Enceladus, of whether the planned missions to the solar system should be reordered to permit returning to Titan or Enceladus earlier than is now scheduled. 

A variety of solvents have higher boiling points than that of water but do not have polar structures. The most accessible of these are the hydrocarbons, which come in a series from the smallest (methane) to higher homologs (ethane, propane, butane, and so on) and are abundant in the solar system. Methane, ethane, propane, butane, pentane, and hexane have boiling points of about 109, 184, 231, 273, 309, and 349 K, respectively, at standard terran pressure. Thus, at a mean surface temperature of 95 K, methane (which freezes at 90 K) would be liquid, implying that oceans of methane could cover the surface of Titan. 

Consideration, in view of the discovery of evidence of liquid water-ammonia eutectics on Titan and active water geysers on Saturn s moon Enceladus, of whether the planned missions to the solar system should be reordered to permit returning to Titan or Enceladus earlier than is now scheduled. The discovery of evidence of liquid water-ammonia eutectics on Titan provides a context for the potential for polar fluids outside what is normally regarded as the habitable zone. The stay of the Cassini-Huygens mission on the surface of Titan was unfortunately brief but this moon of Saturn is the locale that is arguably likely to support exotic life. 

The inquiry about life traces (past or present) outside Earth represents one of the most fascinating goals of the space exploration toward Mars, Titan, Europa, and other bodies of the solar system. 

How can a scientist remain indifferent in light of the fact that carbon chains have been detected by radio astronomers in the molecular clouds present in the interstellar medium or in the circumstellar medium of carbon-rich stars or in the atmosphere of certain bodies of the Solar System such as Titan, Saturn s giant moon The wonder increases further when it is realized that about one thousand organic molecules classified as polyynes are produced by plants, fungi, and microorganisms and play a biological role in the biosphere and may be used in the treatment of diseases as antibiotics, anticancer or, more simply, as anti-infective agents. 

Saturn is the second-largest planet in the solar system, after Jupiter. Its equatorial radius is 37,448 miles (60,268 km), about nine times that of Earth, and its mass is 568.46 x 1024 kg, about 95 times that of Earth. As of early 2007, scientists had found 56 satellites of Saturn, the largest of which is Titan, with a radius of 8,448 feet (2,575 km, about 50 percent larger than that of Earth s Moon), and a mass of 1,345.5 x IO20 kg (about twice that of the Moon). Saturn s density is 0.687 g/cm3, less than that of water. This fact means that (if one could find a body of water large enough) Saturn would float on water. It is the only planet with a density less than that of water. 

Furthermore, Titan still retains the important distinction of being the only satellite in the solar system to have an atmosphere. Its atmosphere appears to be about 50 percent denser than that Earth s, with a surface pressure of about 1.5 bar. Titan s atmosphere, like that of Earth, appears to consist primarily of molecular nitrogen with a... 

Triton is of special interest to scientists because of a number of unusual characteristics. In the first place, it is the only satellite in the solar system to revolve around its parent planet in a retrograde motion—that is, in a direction opposite to that of the planet s rotation. In addition, it is only one of three bodies in the solar system (Earth and Titan being the others) with an atmosphere consisting primarily of nitrogen gas. Triton s atmosphere is very thin, with a surface pressure of only 14 microbars, about 0.0014 percent that on Earth. Also, Triton is the coldest body ever measured in the solar system, with a surface temperature of 38 K (- 235" C). At that temperature, nitrogen is frozen, so that Triton s atmosphere consists primarily of thin clouds made of nitrogen ice and the surface is covered with a thin layer of nitrogen frost. 

Whether formed from acetylene or from some other sources, PAHs are widely distributed in the solar system. As mentioned earlier, PAHs are found in the atmospheres of Jupiter and Titan [37]. They have also been detected in meteorites, including the Martian meteorite Allan Hills 84001 [43], in interplanetary dust [44], and in circumstellar graphite grains [45]. The ubiquity of these complex organic structures and their stability under extreme conditions is a significant factor in discussions of the origin of life on earth and the possibility of its existence elsewhere. 

As stated earlier, many shock reactions would have proceeded in the solar system, and much research relevant to the processes has been published. In this section, two examples of the well-studied cases—chemical evolution of Earth and Titan—are reviewed. 

Melt solidification and late-stage evaporation in the evolution of a FUN inclusion from the Vigarano C3V chondrite. Geochim Cosmochim Acta 55 621-637 de Bergh C, Lutz BL, Owen T, Chauville J (1988) Monodeuterated methane in the outer solar system. 111. Its abundance on Titan. Astrophys J 329 951-955... 

Saturn s moon Titan is the only planetary satellite in the solar system with an atmosphere. Ethane is present in Titan s atmosphere along with the two major components nitrogen and methane. 

The four largest satellites of Jupiter - Ganymede, Callisto, lo, and Europa - are known as the Galilean satellites after their discovery by Galileo in 1610. Ganymede is the largest natural satellite in the solar system and is in tact larger than Mercury it is followed by Titan (Saturn), Callisto (Jupiter), lo (Jupiter), the moon (earth), Europa (Jupiter), and Triton (Neptune). 

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. 

The results may also have imphcations for chemical evolution in the solar system. Our results suggest that nitriles, amines, hydrazines of higher molecular weight and their derivatives, such as cyano-acetylenes and dinitriles, might have been synthesized. The presence of these important compounds, as precursors of biologically important compounds on Titan, implies that the chemical reactions postulated as the formation processes of bases and amino acids on the primitive Earth may be com-moi5)lace in the planetary system. 

But farther out, this sweepstakes has more recent entries. In particular, one other big rock in our solar system has retained a thick atmosphere and liquid oceans on its surface, despite all the physical forces conspiring to remove them. If the three sister planets are primary colors, red, yellow, and blue, this planet-ish rock is a secondary color. It is the mysterious orange moon of Saturn named Titan. 

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