When the Cassini spacecraft (launched on October 15, 1997) flew 175 km (109 miles) from Enceladus in July 2005, everyone believed that the Saturnian moon should be dropped. With the unexpected discovery of a huge water geyser and the strong presence of water vapor in its atmosphere, the satellite, which was previously considered small and “dead” (meaning no geological activity), became the best hope for today to search for extraterrestrial life. Although everything must be in place in order to maintain the existence of life - water - an adequate source of heat, the right chemical nutrients and precise environmental conditions. [that] lead to the necessary chemical reactions ... " [1] , Dr. Robert Brown, a planetary scientist from the University of Arizona and a senior fellow at the Cassini project, said at a major conference in Vienna, Austria [that] Enceladus contains ... ingredients for life. " [2]
History and description:
Enceladus, discovered on August 28, 1789 by German British astronomer Sir William Herschel (1738-1822), best known for discovering Uranus, is the sixth largest moon of Saturn with an average diameter of 504 km (313 miles) approximately seven times smaller than Earth. It revolves around Saturn "at a distance of 238,000 km (147,886 miles) from the center of the planet and 180,000 km (111,847 miles) from its surface, between the orbits of Mimas and Tethys (the other two Saturnian moons) rotating" synchronously "... holding one person in the direction of Saturn ”and completes every revolution in 32.9 hours. [3]
Based on the findings of Cassini, Enceladus consists of a core with a higher percentage of irons (FE) and silicates (a compound consisting of silicon (Si) and oxygen (O), one or more metals, and possibly hydrogen (H)), which can subjected to more heat than radioactive decay than the interiors of other ice moons of Saturn. Enceladus has a light gravitational field, which gives a density of 1.61 grams per cubic centimeter.
It is known that for nearly two centuries Enceladus, “one of the three external bodies of the solar system (along with Jupiter’s Moon and Jupiter’s Triton Moon), where effective eruptions were observed,” remained a simple spot before the Voyager program. When Voyager I flew for 202,000 km (125,517 miles) of Enceladus on November 12, 1980, it reflected “a highly reflective surface devoid of impact craters, [indicative of] young surface. Voyager II, which flew over 87010 km (54,065 miles) of Enceladus on August 26, 1981, discovered a diverse surface - some of which were older and heavily inverted (from middle to northern latitude), others slightly crater (near the equator ), and the reminder is usually smooth and young. [4]
On February 17, March 9 and July 14, 2005, the Cassini flaquites showed Enceladus surfaces in much more detail. "Smooth plains are scattered into relatively crater-free areas, filled with numerous small ridges and ledges ... Numerous fractures (possibly caused by an increase in pressure from the temperature difference between the warm subsurface layer and the cold surface and the outer surface of the Moon environment) were found in the older terrain with tiles ... and several additional young landscapes were discovered ... such as ... near [moon's] South Pole ... [including] intriguing dark spots 125 and 750 meters wide (410 and 2461 feet), which seem to be parallel to narrow fragments [and are believed to be] destructive pits "filled with thick blue ice. Cassini also represented the flowing plains of the moon ( Sarandib Planitia and Diyar Planitia ), which leads to an assessment of the fact that this landscape ranges from 170 to 3.7 billion years, as well as the surface area of Saturn, which was found to be “covered by numerous intersecting sets of trenches and ridges” and the geologically active South Pole, in which the presence of an active geyser was discovered, which penetrates into the water, adding Saturn’s ring to it, and [estimated to be between 10 to 100 million years old that reaches] both in the north and at 60 ° south latitude ... covered with tectonic fractures and ridges[Includingfourfracturededgesboundedbyeachsideoftheridgecalled“tigerstripes”;coveredwiththeeardoftheheadandthebalancewereoscillatedfrom10to100meters(from33to328feet(whicharesmallerthan1000yearsinwidth)”[includingfoursuchfracturesboundedoneachsidebyridgescalled'tigerstripes'coverediniceandevenbouldersrangedfrom10to100meters(33to328feet(widewhichappeartobelessthan1000yearsold)"[включаячетыретакихпереломаограниченныескаждойстороныгребняминазываемыми«тигровымиполосками»;покрытыельдомидажевалуныколебалисьот10до100метров(от33до328футов(вширинукоторыекакпредставляетсяменьше1000лет)»[includingfoursuchfracturesboundedoneachsidebyridgescalled'tigerstripes'coverediniceandevenbouldersrangedfrom10to100meters(33to328feet(widewhichappeartobelessthan1000yearsold)"[5]
The discovery of cryovolcanism (“eruption of water and / or other liquid or vapor-phase volatile substances together with gas solid fragments on the surface of the planet or moon due to internal heating”) [6] on Enceladus. The South Pole, in which the geyser passes water and other volatile substances instead of silicate rock, along with the presence of a non-permanent atmosphere (the thickest around the South Pole), consisting mainly of water vapor (H2O) (91%), as well as a smaller amount of molecular nitrogen (4 %), carbon dioxide (CO2) (3.2%) and methane (CH4) (1.7%) gives the greatest hope for the existence of life somewhere on the lunar surface or benefits it, despite the average surface temperature of about - 325 ° Fahrenheit.
Enceladus & # 39; Water geysers:
When Cassini flew over Enceladus in November 2005, he confirmed the discovery on January 16, 2005 of numerous geyser-like jets of water and ice particles (the composition was determined during the flight in July 2005, when Cassini flew right through the train), rising from a few number of fractures or holes ("tiger stripes") in the lunar moon. One of the plumes has risen to 500 km (311 miles), driven by subsurface chambers under pressure, temperature drops, weak gravity of the moon — about 12 times less than the weak gravitational force of the Earth, and to some extent the gravitational pull of Saturn.
Based on “combined image analysis, mass spectrometry and magnetospheric data,” it is likely that Enceladus plumes of water and ice particles emanate from “sub-surface chambers under pressure” [located less than 100 meters (328 feet) below the moon's icy surface that consist of near pure water heated to about 26 ° -32 ° Fahrenheit prior to ejection]like geysers on earth. " [7] Further confirmation that the water is liquid benefits from an analysis conducted by Cassini on the ice surrounding the tiger strip fractures. "This ice was amorphous and, essentially, without a crater, which indicates that it was relatively recent." [8]
In addition, due to the absence of ammonia (NH3), which can serve as antifreeze for water, it is also likely that the subsurface water of the Moon is heated by tidal (frictional force due to bending or displacement caused by the gravitational pull of Saturn, 2: 1 "Average orbital resonance of motion with Dion", [9] the near moon, which means that Enceladus completes the two orbits of Saturn for each Dion and, to a lesser extent, the gravitational pull of Tethys, another nearby moon) or radiogenic (caused by radioactivity or radioactive transformation) sources, as Enceladus; The temperature of the South Pole is about -177 ° Fahrenheit compared to cold -298 ° to -325 ° Fahrenheit over most of the rest of the moon and because water and ice particles must "have a certain density ... which causes unexpectedly warm temperatures "that must be carried in the air. [10] The difference is too big to be explained by solar heating, as the Enceladus ice surface reflects more than 90% of solar energy back into space. Accordingly, the moon "has the highest albedo (the ratio of reflected to incident light) of any body in the solar system" with a measurement of 0.9. [11]
According to research presented at the European Geoscience Science Conference (EGU) in April 2006, the Enceladus & molten rock core can be as hot as 2060 ° Fahrenheit, which further reinforces the theory that the geological activity of the Moon is fed by tidal tidal and radiogenic sources.
Probably life is formed on Enceladus
If life is found on Enceladus, it is likely to be in the form of extremely simple microbes that can exist in harsh, seemingly unfit for life environments, as long as chemical nutrients, biomolecules such as amino acids, energy source and liquid water exist, which seems to be the case when it comes to pressure cells that provide geothermal warming to the moon.
The case of possible extraterrestrial life:
Ingredients for life:
Two important ingredients for life are water (H2O) and a source of energy (although for some chemosynthetic cryophiles, it was found not to be needed) to fuel and maintain the body's metabolism. Both are present at Eceladus. The relief of liquid water benefits the surface of the moon, and about 99.9% of its relief is ice-covered water (H2O), which is constantly updated by small geysers, which descend like ice particles and snow. At the same time, hydrothermal nozzles that feed Enceladus geysers provide optimal habitat for microorganisms in the same way as on Earth, and on the hydrothermal extracts of the deepwater and Yellowstone National Park.
The third ingredient is nitrogen, which is present on Enceladus and in its atmosphere. "Nitrogen is the main ingredient of amino acids (" organic compounds containing amino group (NH2), carboxylic acid group (COOH) and any of the various side groups, especially any of the 20 compounds that have the basic formula NH2CHRCOOH and bind together with peptide bonds to form proteins or which act as chemical messengers and as intermediates in metabolism ”), commonly referred to as the building blocks of life) and nuclear compounds (“ complex compounds found in all living cells and viruses, consisting of purines, pyrimidines, carbohydrates and phosphoric acid (the nucleic acid as a cellular function and heredity DNA and RNA). [12]
The fourth component is the presence of organic compounds, substances consisting of carbon (C), the element of the signature of life. On the basis of the flavins of Cassini, the existence of simple organic compounds along the tiger strip fractures and in the plumes of water and ice crystals that were pulled out of lunar geysers was discovered. Small amounts of methane (CH4), carbon dioxide (CO2) and propane (C3H8) were found in the plumes, while small amounts of carbon dioxide (CO2) and methane (CH4) were found in Enceladus. atmosphere. In addition, Cassini also detected the presence of ethane (C2H6) and ethylene (C2H4) of two additional organic compounds.
The fifth component is the existence of some kind of "basis for complex chemistry." [13] When considering scientific theories about the beginning of life on Earth, such chemistry is not unattainable for bodies in other places. In the "original soup" (in which biological substances, such as amino acids, left the "organic broth") and "metabolism in the first place" (in which life evolved from small molecules, even smaller than RNA, recently reinforced by the discovery of Methanosarcina acetivorans, underwater microbe that eats carbon monoxide (CO) and displaces methane (CH4) and acetate (CH3COO) " [14] using only “two very simple proteins” for chemosynthesis to maintain their metabolism), the prerequisites for the start of life on Earth were not insurmountably large, especially since this life was originally created in harsh conditions, when the Earth’s atmosphere was mainly represented by toxic substances, such as ammonia (NH3), carbon dioxide (CO2), methane (CH4) and steam.
Prospects for life can also be enhanced, because Enceladus does not have an intense radiation field due to reduced activity of solar ultraviolet (UV) rays due to time (longer), distance (1.427 billion Km) or 886 million miles from the Sun) and shielding (parts of the surface of the moon are shielded by Saturn due to its synchronous rotation).
cryophile
Living and fossil cryophilic (cold-loving) microbes were found in cold arctic environments where temperatures can drop to -90 ° Fahrenheit (Greenland and northern Siberia) to below -125 ° Fahrenheit (Antarctica). They were even found on the Sverrefjell volcano located on the island of Svalbard, northern Norway, where no living organizations were expected. [to exist, having] adapted to extremely cold conditions. " [15]
Examples include moss ", which remained alive but inactive, while frozen for 40,000 years in the permafrost of the Kolyma lowland in northeastern Siberia." [16] orange mosses, covered with black films of cyanobacteria, "grow" on the Matanuska Glaciar ice in Alaska, as well as actinomycetes ("filamentous or rod-shaped ... microorganisms [that] similar bacteria and fungi ”) and other metabolically diverse microbes found in ancient ice samples obtained from the Beacon Valley, Antarctica, and other arctic locales. [17]
The recent discovery of a “new species of polychaete worm (also known as“ pink ”ice worms” about 1-2 cm long) living on the exposed surface of methane gas hydrate (CH4) [s]“In the cold waters deep beneath the ocean there is another positive sign. [18] However, the greatest encouragement comes from the discovery of chemosynthetic cryophiles, which do not need a source of energy for metabolism. Instead of such a source, these organizations derive energy exclusively from “chemical reactions between rock and water (H2O)”. [19]
thermophiles
Living and fossil microbes have been found in geothermal or geologically active environments. One example is the existence of chemosynthetic, thermophilic (heat-loving) microbes that exist in the Yellowstone Basin of Norris Geyser, where the temperature constantly exceeds 158 ° Fahrenheit and photosynthesis cannot occur. Accordingly, they use hydrogen (H2) for their metabolism. This is particularly encouraging because hydrogen (H) is the main component of water (H2O) found in Enceladus genes, and because sunlight reaching Enceladus & the surface is relatively inadequate for photosynthesis.
In addition, chemosynthetic, thermophilic, or hyperthermophilic (extremely thermophilic) microbes using hydrogen sulfide (H2S) for metabolic functions (for example, bacterium Aquifex aeolicus ) and prokaryotic bacteria and cyanobacteria, as well as larger organisms, such as giant tubular worms ( Pacifilita Rifita ) huge shellfish ( Caliptogena ) and mussels) were also detected by geothermal sources of the deep-water waters of the Earth, where temperatures can reach 716 degrees Fahrenheit and sunlight cannot penetrate.
When it comes to bacterium Aquifex aeolicus his requirements are very simple. These thermophilic microorganisms "need much more quantity than hydrogen (H), oxygen (O), carbon dioxide (CO2) and mineral salts for growth" [20] improving the likelihood that similar or similar chemosynthetic organisms can exist on Enceladus, especially in its geothermal pressure cells below the surface.
Other extremimophiles
Along with thermophilic and cryophilic extremophiles (organisms that thrive in the harsh "non-viable" environments), there is a third form - anaerobic life, which thrives in non-oxygen environments under the crust. Their existence further enhances the possibilities of extraterrestrial life on Enceladus, especially since the most likely habitat for such a life may be below the surface of the Saturn Moon.
"Moon" microbes
Perhaps the most fascinating example of what indicates the possibility of life on Enceladus is the proven fact that naked microbes can survive in a harsh space. When the Surveyor 3 probe landed on the moon (earth-moon) on April 20, 1967, it was randomly populated from 50 to 100 microbes ( Streptococcus mitis ) that “sustained launch, space vacuum, 3 years of radiation exposure, deep freezing at an average temperature of only 20º above absolute zero (-453º Fahrenheit) and non-nutrients, water or energy source”. [21] These organisms were still alive when the contaminated Surveyor 3 camera was restored and returned to Earth by Apollo 12 crew on November 12, 1969.
Conclusion:
The prospect of finding extraterrestrial life on Enceladus is extremely encouraging. “Enceladus ... has a chemical chemical recipe for life. Add a pinch of phosphorus, and you have everything you need to make a DNA, and sometimes another DNA-like molecule, ”said Robert Brown. [22]
Based on the existence of critical components of life, adaptability to diversity and the growing number of extremophiles found, thriving in places that seem unfit for life and hostile to life, along with the amazing survival of microbes Surveyor 3, Enceladus seems to be the best hope of finding extraterrestrial life . However, additional research, analysis and research are needed to confirm the existence of this life, the age-old quest for vegetation, because, according to Karl Sagan (1934-1996), the legendary scientist, astronomer and author, "extraordinary requirements require extraordinary evidence." [23]
В то время как Кассини будет вести flybys Enceladus в 2006 и 2007 годах, самая большая перспектива подтвердить существование внеземной жизни или приблизиться в этом направлении лежит на рандеву 12 марта 2008 года. В этот день Кассини пролетит через лунный поток воды и частиц льда, проходящий в пределах 23 км (15 миль) от Энцелада. (если управление полетами считается достаточно безопасным). Тем не менее, вероятное двухлетнее продление миссии Кассини, запланированное на конец 2008 года, потребует дополнительных миссий, включая посадочные зонды (особенно на Энцеладском южном полюсе), поскольку, по словам Каролины Порко, Кассини лидера группы изображений в Институте космических исследований: «Не ясно, что у Кассини есть средства для определения того, содержат ли сами кристаллы льда микробы. Для этого может потребоваться устройство с гораздо большей композиционной точностью, чем у нас, так что это может иметь быть отправленным на будущую миссию [since] мы хотим сделать более эффективную работу по определению состава льдов, содержащих переломы, которые содержат простейшие органические соединения, которые нигде не найдены. " [24]
_____________________________________________________________________________
[1] Джеффри Цвейринк, доктор философии. Энцелад: жидкая вода, но нет жизни.
[2] Ричард Блэк. Лучшая ставка для жизни Сатурна.
[3] Энцелад (луна). Wikipedia.com.
[4] Энцелад (луна). Wikipedia.com.
[5] Энцелад (луна). Wikipedia.com.
[6] Дэвид Дарлинг. криовулканизм.
[7] Энцелад (луна). Wikipedia.com.
[8] Алан Бойл. Жидкая вода на луне Сатурна могла поддерживать жизнь.
[9] Энцелад (луна). Wikipedia.com.
[10] Enceladus Erupting. Журнал «Астробиология».
[11] Билл Арнетт. Энцелад. Сатурн II.
[12] Гидротермальная среда на дне океана. and Dictionary.com.
[13] Питер Н. Споттс. Жизнь за пределами Земли? Потенциальные среды обитания в солнечной системе продолжают появляться.
[14] Майкл Ширбер. Как началась жизнь: новое исследование предлагает простой подход.
[15] Дэвид Л. Чандлер. Инструменты, привязанные к Марсу, обнаруживают арктические микробы.
[16] Поиск жизни на Марсе начнется в Сибири.
[17] Астробиологи охотятся за маленькой игрой в Сибири. and Dictionary.com.
[18] Холодная среда метана на дне океана.
[19] Жизнь в экстремальных условиях.
[20] Гидротермальная среда на дне океана.
[21] На Земле: экстремальные условия.
[22] Питер Н. Споттс. Жизнь за пределами Земли? Потенциальные среды обитания в солнечной системе продолжают появляться.
[23] Алан Бойл. Жидкая вода на луне Сатурна могла поддерживать жизнь.
[24] Леонард Давид. Сатурнская луна вдохновляет вопросы.
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