Gliese 581g: Earthlike Exoplanet may Harbor Potentially Rich Alien Life!!
September 30, 2010 15 Comments
There is a Earthlike planet orbiting around a red dwarf star system Gliese 581, which may be teeming with alien life possibly intelligent alien life. The Gliese 581 system exerts an outsize fascination when compared to many of theother exoplanetary systems that have been discovered to date.The interest stems from the fact that two of its planets lie tantalizingly close to the expected threshold for stable,habitable environments, one near the cool edge, and one near the hot edge. Gliese 581, located 20 light years away from Earth in the constellation Libra, has two previously detected planets that lie at the edges of the habitable zone, one on the hot side (planetc) and one on the cold side (planet d). While some astronomers still think planet d may be habitable if it has a thick atmosphere with a strong greenhouse effect to warm it up and it seems quite possible since planet has much gravity than our own planet. The planet is orbiting at a distance of 0.146AU from its host star and by solving equation its equilibrium surface temperature can be calculated as 228K. An equally important consideration is the actual surface temperature Ts. The equilibrium temperature of the Earth is 255 K, well-below the freezing point of water, but because of its atmosphere, the greenhouse eect warms the surface to a globally-averaged mean value of Ts= 288 K. If, for simplicity, we assume a greenhouse eect for GJ 581g that is as eective as that on Earth, the surface temperatures should be a factor 288/255 times higher than the equilibrium temperature. With this assumption,in the absence oftidal heating sources, the average surface temperatures on GJ 581g would be 236-258K. Alternatively, if we assume that an Earth-like greenhouse eect would simply raise the equilibrium temperature by 33 K, similar to Earth’s greenhouse, the surface temperature would still be about the same, 242-261K. Since it is more massive than Earth, any putative atmosphere would likely be both denser and more massive. It would be denser because of the larger surface gravity, which would tend to hold more of the atmosphere closer to the surface. And the atmosphere may be significantly more massive if we simply assume that the planet went through a formation process similar to that of the Earth and that all the bodies that went into forming GJ 581g had the same relative amount of gasses as in the bodies that went into making up the Earth. Some of these gases would subsequently be outgassed to make the atmosphere.
The planet is tidally locked to the star, meaning that one side is always facing the star and basking in perpetual daylight, while the side facing away from the star is in perpetual darkness. The prominent habitable zone on the planet’s surface would be the line between shadow and light (known as the “terminator”).
Ultimately it seems fair likely that planet might be lurking with organic alien life. The planet is much similar in essence to Earth especially temperature ranges are pretty nourishing for a organic DNA conceding that it might have been put there by cometary impacts. It is conceivable that various corners of the cosmos may be populated by non-cellular or non-DNA or non-carbon derive dentities, some of which may also be highly evolved yet in ways that defy human (DNA-based) comprehension. This may be particularly true of life in distant galaxies; that is, those whose chemistry is radically different from our own. Nevertheless, because the five kingdoms of Earthly life all contain DNA and consist of cellular components, we can make certain predictions about the characteristics of at least some extraterrestrial creatures. We can predict that some alien life forms, like Earth based creatures, consist of living cells, which contain DNA. These cells would probably require water and have acquired electrical-chemical, generative powers for active transport of food, waste, and the transmission and reception of important messages. Some exobiological organisms would have evolved five or more senses and a brain that could process that information. As on Earth, it is likely that some extraterrestrials possess the the same “universal” genetic code and similar genetic memories, instructions, or potential within their DNA. Provided a variable Earth-like environment that was susceptible to genetic engineering, we could predict that on certain worlds, over time,a somewhat similar step wise sequence of increasing intelligence, complexity and diversity would take place involving numerous extinctions and recoveries. animals reminiscent of reptiles, repto-mammals, therapsids, mammals, primates, and human-like creatures might likely blossom and unfold; which does not mean to say they would look like their Earthly counterparts.We can also predict that those aliens who are related to the Animal Kingdom of Life would be intelligent,and have brains comprised of nerve cells and DNA. Since life is not evolved just from chemical randomness.
For given surface temperature GJ 581g, is habitable. Human like creatures could easily nurture into ‘terminator’ zone of planet where planet is neither too ‘cold’ nor too ‘hot’, just right! On the other hand, planet should be habited by extremophiles. Bacteria have a number of mechanisms by which they are able to resist and protect themselves against radiation and heat. When compared to mesophilic bacteria (that typically live between 20-40°C), thermophilic bacteria (optimum growth can exceed 100°C) have greatly enhanced protein and nucleic acid stability. These mechanisms include an increased cross-linking of proteins and altered DNA structure. When growing bacteria are subjected to temperatures approaching their upper growth range, cellular damage and death can arise from protein misfolding (denaturation), a loss of membrane integrity and DNA damage. Bacteria, including thermophiles, have a number of stress responses, including producing a variety of heat shock proteins. Early studies showed that bacteria such as Escherichia coli, expressed a number of heat shock genes when they approached their maximum growth temperature; and that bacteria defective in these geneshad reduced thermal tolerance. Several heat shock genes encode the synthesis of a number of accessory proteins called chaperones.
The search for extraterrestrial life is encouraged by a comparison between organisms living in severe environmental conditions on Earth and the physical and chemical conditions that exist on some Solar System bodies. The extremophiles that could tolerate more that one factor of harsh conditions are called poly-extremophiles. There are unicellular and even multicellular organisms that are classified as hyperthermophiles (heat lovers), psychrophiles (cold lovers), halophiles (salt lovers), barophiles (living under high pressures), acidophiles (living in media of the lower scale of pH). At the other end of the pH scale they are called alkaliphiles (namely, microbes that live at the higher range of the pH scale). Thermo-acidophilic microbes thrive in elevated thermo-environments with acidic levels that exist ubiquitously in hot acidic springs.Cyanidium caldarium, is a classical example of an acido-thermophilic red alga that thrives in places such as hot-springs (<570 and in the range 0.2-4 pH). This algal group shows a higher growth rate (expressed as number of cells and higher oxygen production when cultured with a stream of pure CO2, rather than when bubbled with a stream of air (Seckbach, 2010). It has been reported that Cyanidium cells resisted being submerged in sulfuric acid (1N H2SO4). This is a practical method for purifying cultures in the laboratory and eliminating other microbial contamination (Allen, 1959). The psychrophiles thrive in cold environments, such as within the territories found in the Siberian permafrost, around the North Pole in Arctic soils, and they may also grow in Antarctica.
Barophilic microorganisms can tolerate a pressure of 1000 atmospheres on the seafloor, while other barophilic microorganisms have been detected in the subsurface of dry land. In hypersaline areas (such as the Dead Sea, Israel) we find halophilic bacteria (Arahal et al., 1999) and algae that can balance the osmotic pressure of hypotonic external solutions (Oren, 1988).
Chroococcidiopsis is one of the most primitive cyanobacterium known so far. This microbe survives in a wide range of extreme habitats that are hostile to most other forms of life. Chroococcidiopsis grows in hot springs, in hypersaline habitats, in a number of hot, arid deserts throughout the world, as well as in the frigid Ross Desert in Antarctica (Fewer et al., 2002).
Recently, the segmented microscopic animals tardigrades, (0.1 – 1.5 mm) have been under investigations (Goldstein and Blaxter, 2002; Horikawa, 2008). These “water bears” are polyextremophilic, and are able to tolerate a temperature range from about 00C up to + 1510C (much more that other known microbial prokaryotic extremophiles, Bertolani et al., 2004). But even low Earth orbit extreme temperatures are possible: tardigrades can survive being heated for a few minutes to 151°C, or being chilled for days at -200°C, or for a few minutes at -272°C, 1° warmer than absolute zero (Jönsson et al., 2008). These extraordinary temperatures were discovered by an ESA project of research into the fundamental physiology of the tardigrade, named TARDIS. Tardigrades are also known to resist high radiation, vacuum, and anhydrous condition for a decade in a dehydrated stage and can tolerate a pressure of up to 6,000 atmospheres. These aquatic creatures are ideal candidates for extraterrestrial life and for withstanding long periods in space. They have already been used in space and have survived such stress. That’s why I find it indulging to speculate Why Extraterrestrial Contact is ‘NOT’ Blithering?
Hope there is life!
[Note: I’ll be back with full review of possibility of life on earthlike planet GJ 581g]
[Ref: Astrobiology: From Extremophiles in The Solar System to Extraterrestrial Civilization by Joseph Seckback]