Water extraterrestrial

Rather different circumstances are encountered when considering THz remote sensing of extraterrestrial sources. The major source of THz opacity in the Earth s atmosphere is water vapour, and from either high, dry mountain sites or from space there are windows in which the background becomes very small. Incoherent instruments which detect the faint emission from astronomical sources can therefore be considerably more sensitive than their laboratory... 

When considering how the evolution of life could have come about, the seeding of terrestrial life by extraterrestrial bacterial spores traveling through space (panspermia) deserves mention. Much is said about the possibility of some form of life on other planets, including Mars or more distant celestial bodies. Is it possible for some remnants of bacterial life, enclosed in a protective coat of rock dust, to have traveled enormous distances, staying dormant at the extremely low temperature of space and even surviving deadly radiation The spore may be neither alive nor completely dead, and even after billions of years it could have an infinitesimal chance to reach a planet where liquid water could restart its life. Is this science fiction or a real possibility We don t know. Around the turn of the twentieth century Svante Arrhenius (Nobel Prize in chemistry 1903) developed this theory in more detail. There was much recent excitement about claimed fossil bacterial remains in a Martian meteorite recovered from Antarctica (not since... 

Alexander von Humboldt (1769-1859) recognised meteorites as being a source of extraterrestrial material. Several well-known chemists carried out analyses of material from meteorites, starting at the beginning of the nineteenth century. Thus Louis-Jacques Thenard (1777-1857) found carbon in Alais meteorites these results were confirmed in 1834 by Jons Jacob Berzelius, who by dint of very careful work was also able to detect water of crystallisation in meteoritic material. 

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). 

Maser transitions have been observed in many important molecules and have been used to carry out surveys of the entire sky. The 22.235 GHz water maser transition is the strongest transition in the radio universe and represents an interesting candidate for an interstellar broadcast frequency. If extraterrestrial intelligence is trying to communicate with us, the choice of the broadcast frequency is an important one and would be known to all intelligent life. Of course it would have a different label, 22.235 GHz being a distinctly Earthly label, but it is a fundamental transition frequency and is observed everywhere. Other maser transitions include the 6.7 and 12.2 GHz methanol maser, the SiO maser v = 1, J = 7-6, 301.8 GHz, which occurs between levels in the first vibration state of the SiO molecule, and finally the OH maser first discovered in 1963 and buried deep in the 2n3/2 electronic state of the hydroxyl radical near 18 cm. This is actually four transitions at 1612, 1665, 1667 and 1720 MHz, all of which must be seen as a group but not necessarily of the same intensity. 

The high precision with which Mg isotope ratios can be measured using MC-ICPMS opens up new opportunities for using Mg as a tracer in both terrestrial and extraterrestrial materials. A key advance is the ability to resolve kinetic from equilibrium mass-dependent fractionation processes. From these new data it appears that Mg in waters is related to mantle and crustal reservoirs of Mg by kinetic fractionation while Mg in carbonates is related in turn to the waters by equilibrium processes. Resolution of different fractionation laws is only possible for measurements of Mg in solution at present laser ablation combined with MC-ICPMS (LA-MC-ICPMS) is not yet sufficiently precise to measure different fractionation laws. 

The presence of organic molecules in samples of extraterrestrial matter has been known for more than a century. Some of the greatest chemists of the nineteenth century were involved in the analysis of samples of meteoritic material. They were able to show that carbonaceous chondrites (as they are now named) contain organic molecules. The first to detect carbon in a meteoritic sample was Thenard, in 1806, by analysis of a sample of the Alais meteorite. This result was confirmed in 1834 by Berzelius, who was also the first to detect the presence of water of crystallisation. Working on a sample of the Kaba meteorite, Wohler (1858) confirmed the presence of organic matter, and in a paper dated 1859 said, I am still convinced that besides free carbon this meteorite contains a low-melting point, carbon containing substance which seems to be similar to certain fossil hydrocarbon-like substances... . 

Is this a plausible premise In order to approach this question, we can assume that the mixture of organic compounds in carbonaceous meteorites such as the Murchison meteorite resembles components available on the early Earth through extraterrestrial infall. A series of organic acids represents the most abundant water-soluble fraction in carbonaceous meteorites [ 15,67,68]. Samples of the Murchison meteorite were extracted in an organic solvent commonly used to extract membrane lipids from biological sources [69,70]. When this material was allowed to interact with aqueous phases, one class of compounds with acidic properties was clearly capable of forming membrane-bounded vesicles (Fig. 7). 

Earth may be just one of many models of planets that can evolve complex life. We do not know whether it is even practical or logical to assume that planets that exist outside our perception of a habitable zone could harbor life, particularly life that we know nothing about. Our practical search for extraterrestrial life is focused on water-rich planets and moons because of the possibility that they can support Earth-like life. That does not preclude... 

The Cl chondrites have long been cited as the classic example of asteroidal aqueous alteration, because of the presence of ubiquitous sulfate veins (DuFresne and Anders, 1962 Richardson, 1978 Fredriksson and Kerridge, 1988). These veins crosscut the dark, fine-grained matrix and can extend across the entire meteorite sample or stone. These veins have commonly been attributed to the widespread movement of water within the Cl parent body. However, Gounelle and Zolensky (2001) have reappraised the origin of these veins and concluded that they are terrestrial, not asteroidal, in origin. Their preferred interpretation is that the veins formed as a result of the dissolution, local transport, and precipitation of extraterrestrial sulfates by absorbed terrestrial water. Thus, one of the widely accepted lines of evidence to support parent-body alteration should now be treated with caution. 

Fig. 5.48 shows the extraterrestrial spectrum Ex°n and the associated pattern of EXn. The upper edge of this curve represents the irradiance reduced purely by Rayleigh scattering. The deteriorations marked in black are caused by the absorption by the gases 03, 02, H20 and C02. Further diagrams of this type, which show the variation in the influencing quantities (water vapour and ozone content, turbidness due to aerosols, different optical masses), are available in M. Iqbal [5.34]. 

A few informative properties of life come from easy category distinctions, such as the fact that all known life makes essential use of carbon and carbon-oxygen-nitrogen molecules in liquid water solution. The seemingly trivial observation that such carbaquist chemistry is ruled out if astrophysical carbon abundance lies below a certain threshold enabled Hoyle [1] to predict the 7.6 MeV carbon-12 ( C) nuclear resonance with remarkable precision because the discovery of the triple-alpha reaction synthesis of in stars happens to be a bottleneck for stellar nucleosynthesis of all the heavy elements. The pragmatic information in this prediction is easy to measure because it guided experimental characterization of nuclear structure where the existing computational capabilities could not. Similar sensitive dependence of the physical state of water has been used to define a habitable zone in planetary physics [10], which is not predictive in the same sense as carbon abundance (we already knew where the earth s orbit lies), but which creates a useful filter in the search for extraterrestrial life. 

These lines of evidence demonstrate that the early Earth could have accumulated abiotic molecules in its oceans and smaller bodies of water from both extraterrestrial and terrestrial sources. 

At the present time the balance of evidence is against a cometary origin for prebiotic carbon on Earth, for the same comets would also have delivered water to the Earth and yet the D/H ratio of the terrestrial oceans is different from that in comets. The more likely extraterrestrial input is from asteroids and meteorites, for there is evidence from both lunar and terrestrial samples that the late heavy bombardment event at 3.9 Ga (Section 6.4.1) contributed meteoritic material to the Earth at this time. 

Hydrogen, as an indicator of the presence of water, plays a role in the search for extraterrestrial life. In an October 1992 story about NASA s then newly computerized search for intelligent life in space, Newsweek noted that the ongoing search by the planetary researcher Paul Horowitz was focused on hydrogen s frequency of 1420 megahertz. This simplest and most abundant atom in the universe, Newsweek explained, vibrates at a frequency of 1,420,405,751 cycles a second, a frequency that Horowitz says would make sense as a meeting place in the vast radio spectrum. 8... 

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