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5 Possibilities of How Alien Life Could Appear On Other Habitable Planets
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| Pompeii Worm |
Many scientists have speculated that certain environmental conditions, that exist on other habitable planets, must be similar to our own planet's overall climate in order to support life and therefore be considered habitable. Yet, theoretically if various combinations of environmental arrangements can occur on other planets, then many of these planets most likely exhibit climate features and elemental compositions that closely match a number of extreme environments found right here on earth. All of these extreme earthly environments are known to provide a large range habitats to many diverse and hardy organisms, therefore one could surmise that several variations of these organisms may also exist on many other planets with similar environments. In fact, researchers are looking to the extremes of the Earth for clues about what kind of organisms could exist in corresponding conditions elsewhere.
There has been more than 700 planets discovered outside our solar system yet none of them match or come even close to a Earth-like planet astronomers and hunters fantasize about. Although there are some scientists thinking outside of the box and broadening the criteria of their search. Some with the help of the Planetary Habitability Index, a scoring system that measures the suitability for all known life forms, it also accounts for the possibility of organisms that may not currently fit the parameters of life as we know it. The Planetary Habitability Index was created by a team led by Washington State University astrobiologist Dirk-Shulze-Makuch who stated, "We can't go after only the Earth model of life. You really want to be open-minded." Under Shulze-Makuch's rating system solid surfaces with an atmosphere and any liquids score much higher than a dry world or a gaseous planet like Jupiter or Saturn.
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| Artist rendering provided by NASA that shows the Earth-sized planet dubbed Kepler-186f orbiting a star 500 light-years from Earth. Astronomers say the planet may hold water on its surface and is the best candidate yet of a habitable planet in the ongoing search for an Earth twin. |
Surprisingly, the presence of water offers no more points in this system than any other known liquid that occurs in the universe. Shulze-Makuch explained his team's reasoning by saying, "If you didn't know that water worked on Earth, you might think methanol would work much better for life." His hypothesis is that most Earth-like places are not necessarily the friendliest for life, despite Earth's almost perfect score in the index. Scoring at 0.96 on the 0 to 1 scale. Saturn's moon, Titan, came in at second totaling 0.64 due to the speculated habitability of the moon's many lakes of hydrocarbons. A high score despite it's surface temperatures of it's -300 degrees Fahrenheit. Recently, we have discovered that there are organisms here on Earth that can handle the extreme temperature of -300. The psychrophilic bacterium, Colwellia psychrerythraeastrain 34H, has shown in studies that the it can withstand -320 degrees Fahrenheit, the temperature of liquid nitrogen. |
Colwellia psychrerythraea Photo: Richard A. Finkelstein |
If one subscribes to the theory of Panspermia, the idea that life is transferred from planet to planet, and galaxy to galaxy throughout the universe, as the means by which life began on Earth. As opposed to Abiogenesis, the theory that life originated and developed spontaneously on Earth through the gradual chemical evolution of molecules that contain carbon in the primordial soup. However, these two theories are not necessarily mutually exclusive. But if the theory of Panspermia is closer to the truth of how life began on Earth, or possibly true for only some of the organisms on Earth rather than all. Then it would mean that some of these life forms, which have traveled between habitable planets, are probably quite similar and genetically comparable to organisms found here on earth. Possibly even indistinguishable.
The organisms that will be featured on this list can also be applied as possibilities in relation to the theory of Abiogenesis. If organisms do exist on alien planets, and some of them dwell in habitats that are comparable to environments here on Earth, then these alien organisms may be analogous. In other words, they would need to function in in relative ways to their Earthly counterparts and therefore may be somewhat similar appearance or display almost identical features and limbs which would enable them to travel through their similar environments. For example, the wings of pterosaurs, bats, and birds are analogous as wings used for flight, but homologous as forelimbs. Analogous describes the relation between characteristics in organisms that are apparently similar yet phylogenetically independent. Meaning that the wings are similar to enable these organisms to fly, but the wings in these organisms did not developed from the same structure or a recent common ancestor. Homology in contrast, is the existence of shared ancestry between a pair of structures, or genes, in different species that can adapt to different purposes as the result of descent with modification from a common ancestor.
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| The wings of pterosaurs (1), bats (2) and birds (3) are analogous as wings, but homologous as forelimbs. |
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| A common example of homologous structures in evolutionary biology are the wings of bats and the arms of primates. Evolutionary theory explains the existence of homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The biological derivation relationship (shown by colors) of the various bones in the forelimbs of four vertebrates is known as homology, and was one of Charles Darwin’s arguments in favor of evolution. |
Both the terrestrial and alien organisms would be faced with almost identical obstacles, via their similar environments, that must be solved through the facilitation of movement to obtain nutritional energy, or possibly obtain mates for the process of reproduction and because of this they might develop similar features. This would be an example of true convergent evolution, or the the independent evolution of similar features in species of different lineages resulting in symmetrical physical structures and limbs. It might result in proportional limbs with similar features to grasp objects with, similar eye-placement, or even whether or not eyes are present at all. Although if the theory of panspermia were to prove correct, then this would be better defined as parallel evolution. Parallel evolution is the development of similar traits in related, but distinct, species descending from the same ancestor, but from different clades.
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| Vertebrates (left) and octopuses (right) developed the camera eye independently and would be one example of convergent evolution. |
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| Two succulent plant genera, Euphorbia and Astrophytum, are only distantly related with distinct ancestors, but have independently converged on a similar body form. |
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| The Wooly mammoth and the modern elephant would be considered examples of parallel evolution because of a more recent common ancestor. However the cutoff point for what is considered convergent and what is considered parallel evolution is assigned somewhat arbitrarily. When two species are similar in a particular character, evolution is defined as parallel if the ancestors were also similar and convergent if they were not. However, this definition is somewhat murky. All organisms share a common ancestor more or less recently, so the question of how far back to look in evolutionary time and how similar the ancestors need to be for one to consider parallel evolution to have taken place is not entirely resolved within evolutionary biology. |
The various forms, functions, and physiques of organisms located on other habitable planets in the universe are probably endless and we are limited to capabilities of the human imagination and have only the environments that exist here on Earth, and the organisms that populate those environments, to draw comparisons. Yet, we also have technology that allows researchers, which include astronauts and scientists with NASA and the International Space Station (ISS), to expose organisms to simulated physically and geochemically extreme conditions that are detrimental to most forms of life. This enables the researchers to see how these Earthly organisms might cope with an alien environment or conditions experienced in the vacuum of space.
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| Expose-R is a suite of ESA experiments, some of which could help understand how life originated on Earth, that was installed on the outside of the Russian segment of the International Space Station. Expose-R was equipped with three trays. Each tray was loaded with a variety of biological samples including plant seeds and spores of bacteria, fungi and ferns that was exposed to the harsh space environment for about one and a half years. |
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| These are electron micrographs of Bacillus pumilus SAFR-032 spores on aluminum before and after exposure to space conditions. |
If these organisms were to embark on interstellar travel and survive, as well as manage to withstand poisonous cosmic radiation and reach a habitable planet where the environmental conditions are more favorable. Then logically, some of the surviving offspring could eventually expand into many diverse forms of life via evolution. They would do this in response to the various environments they are exposed to on each new planet. Yet, a percentage of the surviving offspring might continue with much of their original genetic features. If this is so, then the that percentage would retain their ability to survive extreme conditions and start the process of populating a new planet all over again if needed. A contingency plan of sorts.
One example of such an animal is the Tardigrade, an aquatic micro-animal that can survive travel in space. In May 2011, Italian scientists sent tardigrades on board the International Space Station along with other extremophiles on STS-134, the final flight of Space Shuttle Endeavour. Their conclusion was that microgravity and cosmic radiation "did not significantly affect survival of tardigrades in flight, confirming that tardigrades represent a useful animal for space research." Tardigrades can also withstand temperatures from just above absolute zero to well above the boiling point of water, pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human. They can go without food or water for more than 10 years, needing only 3% or less of their normal water intake to rehydrate, forage, and reproduce.
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| Tardigrade |
It may be that some of the organisms that reach new planets are preprogrammed not to evolve, to evolve slowly, or even to hold dormant the ability to devolve when under stress in order to retain their ability to survive harsh environments and therefore their ability to survive a planet's destruction. Although this trade off would land them at the bottom of the food chain, the long-term benefits would be worth the sacrifice. One example of such a creature may be the 40+ million year old water flea, a type of sea plankton and crustacean that can live on the surface of the International Space Station for years amid factors such as space flight, zero gravity, extreme temperatures, and hard cosmic radiation. The female water flea can also reproduce through parthenogenesis, the process of reproduction without the fertilization of eggs or any contribution from the male sex which produces both male and non-clone female offspring.
Most species of water flea display cyclical parthenogenesis, reproducing both sexually and asexually. Although when exposed to environmental stress, the water flea can biologically choose to reproduce through parthenogenesis. It has been hypothesized that this reproductive adaptation allows a single female to enter an isolated ecological niche (such as an unpopulated planet) and by parthenogenesis produce male offspring. Thereby establishing a sexually reproducing population via reproduction with her own offspring. Towards the end of the growing season the females produce tough "resting eggs" or "winter eggs." Most offspring are typically female, but a small number of males are also produced in most species. The males that are produced then fertilize the females' eggs. The resulting eggs are called resting eggs and are protected by a hardened coat called the ephippium, which can withstand periods of extreme cold, drought, or lack of food and still hatch. When conditions improve the resting eggs always hatch into viable females, ensuring their survival for another generation despite any harsh or extreme conditions.
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| Daphnia pulex (Water Flea) |
If the theory of Panspermia is correct then it would mean that some of these life forms, once they reached a viable planet, would evolve through mutations in their DNA triggered by environmental cues. These mutations could result in different combinations of useful genetic functions like growing larger, developing sharper sight, or developing certain limbs to facilitate faster movement. This evolutionary flexibility might enable them to prey more easily on those who have not evolved and therefore evolution enables these organisms to reap the nutritional benefits. Yet, while the evolved gain in the short-term perspective they also lose their ability to survive outside the environment they have adapted to, and therefore give up the ability to reproduce and maintain their genetic lineage in the event of complete habitat destruction and possible species annihilation.
One supporting example for the theory of Panspermia is the fact that many organisms can travel and survive in the vacuum of space. (See Link: 6 Organisms That Can Survive Travel In The Vacuum Of Space) like the Tardigrade mentioned before. Or we could go a step further and look at those organisms that could persevere despite a worldwide nuclear fallout. Which could, in some aspects, simulate the extreme conditions experienced in the early years of our planet. Or simulate conditions on other planets with harsher environments than our own, like those with high radiation levels. One example of such an organism would be the extremophilic bacterium, Deinococcus radiodurans, one of the most radioresistant organisms known to man that can survive cold, dehydration, vacuum, acid, and is therefore known as a polyextremophile. It was also listed as the world's toughest bacterium in The Guinness Book Of World Records and nicknamed Conan the Bacterium. (See Link: 6 Organisms That Can Survive The Fallout From A Nuclear Explosion)
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| Deinococcus radiodurans |
Several diverse organisms have been proven to possess the ability to survive cosmic radiation and travel in the vacuum of space. In theory, these organisms would do this by hitching rides on and in meteors, asteroids, or comets. Many organisms have the ability to lie dormant for a considerable number of years, until re-hydration occurs and more favorable conditions are located. The question now is: Can some resurrect after thousands of years or even millions? Researchers from the British Antarctic Survey and University of Reading report in Current Biology that Antarctic mosses can come back to life after 1,500 completely inactive years under the ice. "These mosses were basically in a very long-term deep freeze," says Peter Convey of the British Antarctic Survey. "This timescale of survival and recovery is much, much longer than anything reported for them before."
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Ivuna CI1 meteorite filament (left) and the giant bacterium Titano spirillum velox (Right)
Fossil like structures found in meteorite and proposed to be similar in appearance to several species of cynobacteria by Richard Hoover, an astrobiologist with NASA’s Marshall Space Flight Center, and published in the highly controversial Journal of Cosmology. |
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| Sri Lankan (Polonnaruwa) meteorite studied by researchers and Astrobiologists at Cardiff University who confirmed the rock found is a meteorite and the structures found inside it are not terrestrial, and are definitely “fossilized biological structures.” |
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| Images of the earliest microorganisms found on Earth 3.5 billion years old. (Left) They resemble filaments of modern blue-green algae (cyanobacteria) The oldest known rocks found on Earth are 3.8 billion years old, only slightly older than the oldest fossilized organisms found on Earth. |
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| Electron microscopic image of lichen following post-flight analysis. The cells are complete and not broken. |
The universe is an estimated 13.8 billion years old, so with such ample opportunity it is likely that if these organisms can spread throughout the universe, they have. Whatever can happen will happen, or so Murphy's law states. So if the theory is proven correct, then the transfer of organisms would most likely occur as a result of large meteors, asteroids, or comets hitting a planet that contains life and subsequently launching debris laden with local flora and fauna out into space with a tiny percentage of organisms eventually landing somewhere they can thrive.
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| Formation on a meteorite believed to be a form of non-terrestrial cyanobacteria by Dr. Richard Hoover of NASA. (published in the Journal of Cosmology) |
If either theory is at all true, as either or both could be way off base, but if one or the other is proven correct then in the future we may be able to deduce what life might look like on a specific planet, that falls within the habitable range, by looking at how life evolved under similar circumstances and comparable habitats here on Earth. Eventually we may develop telescopes that are powerful enough to probe these worlds, such as NASA's proposed Terrestrial Planet Finder, or even travel to these distant worlds ourselves.
If we observe organisms that are classified as extremophiles, or creatures that can survive the harshest conditions that exist on Earth, then we may be able to accurately hypothesize what types of creatures might exist on a planet with homologous surroundings to a place or specific environment located on Earth. For example, there are some organisms that live in highly acidic environments, consume poisonous heavy metals like arsenic, survive extreme temperatures, or even prevail in the complete absence of oxygen. These creatures could thrive on a planet that would normally be toxic and deadly to most life currently located on Earth.Here is a list of 5 possibilities of how alien life could appear on other habitable planets:
5 Pompeii Worm
Described as the most heat tolerant animal known to science, the Pompeii Worm lives in deep hydro-thermal sea vents. They grow to about 5 inches and have red tentacles on their head's that work like gills. These creatures are particularly interesting due to the widely varying temperatures they occupy at one time. While their heads rest in a cool 72 degrees Fahrenheit, their tails seep in a extremely high 176 degrees Fahrenheit, a difference of over 100 degrees. Their trick is to feed tiny bacteria with mucus like secretions to encourage the bacteria to form a protective shell.
4 Watermelon Snow
Snow Algae is also called Watermelon Snow because of the red tint it leaves behind on clothing when coming in contact. It is a psychrophilic species of green algae, despite it's reddish tint, that lives in freezing water and ice like the snow and permafrost that doesn't melt after winter months. It has been described as looking like streams of blood pouring down the white and snowy mountain cliffs.
3 Acidithiobacillus
Acidithiobacillus is an acidophile, meaning that it thrives under highly acidic conditions. It metabolizes sulfur which it very useful to humans. It is used in a mining technique where metals are extracted from ore through oxidation as the catalysts in the bio-mining process. It just may have genetic cousins on some highly acidic planet.
2 Pyrococcus Furiosus
Pyrococcus Furiosis is classified as a Hyperthermophile because it thrives in extremely high temperatures, much higher that Thermophiles like the Pompeii Worm. It lives in temperatures of up to 217 degrees Fahrenheit, a temperature that would destroy most living organisms. It is also one of the few organisms that possesses enzymes containing tungsten which is rarely found in biological molecules. It lives in thermal marine sediments and is mostly noted for its exponential growth curve, doubling the number of individual organisms every 37 minutes.
1 Acitnomyces
Acitnomyces is an anerobic organism, meaning it does not require oxygen for growth. It thrives in oxygen free environments but can also use oxygen if needed. This would enable it to thrive on an oxygen free planet. Acitnomyces is a class of bacteria that was originally mistaken for a fungus because of the way it grows in fungi like branches. It produces a number of enzymes that help degrade organic matter and is important in the composting procedure.
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