Non-carbon life form - VIDEO PDF Print E-mail
Sunday, 29 March 2015 09:00

All living things on our planet is composed of carbon, oxygen, phosphorus and sulfur. But this does not mean that on other planets can not be a life based on completely different compounds. For example, silicon-based life could exist on planets is much hotter than the Earth.

 Silicon Oxygen +

The main contender for the role of structure-atom in an alternative biochemistry considered silicon. It is located in the same group of the periodic system and carbon that therefore their properties are similar. However, the silicon atoms have a greater mass and a greater radius it difficult to form a covalent bond, and it can prevent the formation of biopolymers (class of polymers which is found in nature in their natural form and is part of living organisms, proteins, nucleic acids, polysaccharides, lignin - NS ). In addition, silicon compounds are not as diverse as the carbon compound.
At the same time, for example, silicon compounds and hydrogen - silanes - are more heat resistant than a carbon-hydrogen compound. Therefore, scientists believe that the silicon life can exist on the planet, the average temperature is significantly higher than the earth. In this case, a natural solvent must be water earthmen for animating and compounds with a higher boiling point and melting point.
In December 2010, a researcher at the NASA Astrobiology Research Felisa Wolfe-Simon announced the opening of the bacterium GFAJ-1 of the genus Halomonadaceae, capable, under certain conditions, to replace phosphorus with arsenic.
Silicon compounds are believed also to be more resistant to sulfuric acid. But in relation to other media silicon compounds are considered less stable compared with carbon.
Nitrogen + phosphorus

Like carbon, phosphorus may be a chain of atoms which, in principle, could form a complex macromolecule, if it has not been so active. However, together with the nitrogen can form a more complicated version of covalent bonds, and which makes possible the occurrence of a large variety of molecules, including the ring structure.
In the atmosphere of our planet, about 78% nitrogen, but due to the inertia of a diatomic nitrogen energy "cost" of education trivalent connection is too high. At the same time, some plants can fix nitrogen from the soil in symbiosis with the anaerobic bacteria that live in their root system. If present in the atmosphere will be a significant amount of nitrogen dioxide or ammonia, nitrogen availability is higher. Furthermore, the atmosphere can be saturated ekzoplanet and other nitrogen oxides.
In the atmosphere of ammonia plants whose molecules consist of phosphorus and nitrogen to give an atmosphere of nitrogen and phosphorus - from the soil. Cells were blocked for ammonia would be oxidized to form a monosaccharide analogues and hydrogen would be allocated as a byproduct. Therefore, in this case the animals will inhale hydrogen, cleaving polysaccharides analogs to ammonia and phosphorus. Thus, energy would be formed by the chain in reverse order as compared with what we observe in the world (on the planet, in this case would be circulated methane).

 Nitrogen + hydrogen

Recently, according to theorist crystallography, chemists, physicists and materials scientists, science popularizer Artem Oganov, their team found an interesting feature of nitrogen and hydrogen. It was found that the compressed azotovodorody can give much more diverse chemistry than hydrocarbons (these compounds exist in a thermodynamically stable state). And it is a variety of hydrocarbons, as mentioned above, gives us such biodiversity.
Meanwhile azotovodorodov in the Universe very much. Thus, the planets Uranus and Neptune 8% consist of ammonia (attributable to common azotovodorodam), there is a lot more than on Earth. Among other things hydrogen and nitrogen compounds have low melting points, which increases with the pressure (and temperature in the interior of planets).
"For covalent nitrogen compounds with very strong directional communications will also be characterized by metastability - in other words, not only that pressure has an unusually large number of stable compounds, there still will be a virtually unlimited number of metastable compounds - Artem Oganov writes. - If there start adding other atoms of oxygen, sulfur, - the chemical diversity that exceeds variety of organic chemistry. This is an area of ​​chemistry that we have so far hardly know, and that came out of our calculations. "
Possible life on planets such as Uranus and Neptune? Unknown. "The potential problem is that the lifetime of metastable compounds in planetary conditions (high temperature and pressure) may be long enough" - concludes chemist.



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