Title-: Hello! Are we alone? If you're like me, you may want to know me!
Authors_:
**Professor Pranab kumar Bhattacharya- MD(cal) FIC Path(Ind), Professor and Head Department of Pathology Calcutta school of Tropical Medicine, Incharge DCP and DLT of WBUHS; Ex professor and HOD Pathology RIO calcutta and WBUHS &Ex Professor of department of Pathology, Institute of Post Graduate Medical Education & Research,244 AJC Bose Road, Kolkata-20, West Bengal, India* Miss Upasana Bhattacharya- Student, Mahamayatala, Garia, kol-84, only daughter of Prof.PK Bhattacharya** Mr. Rupak Bhattacharya-Bsc(cal), Msc(JU), 7/51 Purbapalli, Sodepur, Dist 24 Parganas(north) Kol-110,West Bengal, India ***Mr.Ritwik Bhattacharya B.com(cal), Miss Rupsa Bhattacharya Student http://www.bautforum.com/showthread.php/100276-Detecting-alien-radio-TV-signals?p=1676453#post1676453 Mr Somayak Bhattacharya MBA of residence7/51 Purbapalli, Sodepur, Dist 24 parganas(north) ,Kolkata-110,WestBengal, India******** bra, 24 Parganas(north), West Bengal, Indihttp://sciencejournals.stmjournals.in/index.php/RRJoSST/article/view/2Mrs. Dalia Mukherjee BA(hons) Cal, Swamiji Road, South Habra, 24 Parganas(north) West Bengal, India**** Miss Aindrila Mukherjee-Student , Mr Debasis Mukherjee BSc(cal) of Residence Swamiji Road, South Ha339
Alien life forms are generally regarded as the stuff of science fiction and fantasy and subject for/ from the movies by several times Oscar winner Hollywood director Steven Spielberg. But both SETI [While philosophers and biologists may debate the meaning of the term 'intelligence', for the purposes of the SETI project intelligence simply means the ability to build large radio telescopes and transmitter of high-powered radio signals or intense laser beams] and NASA's Exobiology Program, which seeks to understand the origin, evolution and distribution of life in the Universe, researchers are about to begin the SETI Microwave Observing Project. Radio telescopes around the world which will search for signals produced by other intelligences. There are of course two schools of thoughts about intelligent life out there in the Galaxy, It is argued that life on the planet Earth, and especially intelligent life, is the result of an incredibly unlikely set of circumstances; and there is no intelligent life anywhere else in our Milky Way Galaxy, perhaps none in the entire Universe. But according to the opposing school argument, there are so many stars and planets in the Galaxy that, provided there is even a small chance of intelligence developing on any one planet it must have happened many times on many different planets. Nobody seems to take the middle view, that life is restricted to just a few planets in our Galaxy; either it exists solely on Earth, or there are many inhabited planets. If the SETI project detects just one signal, the implication will be that we are not alone, and that evolutionary biology is an inherent characteristic of certain locations in the Universe - planets like Earth.[1]
Universe or our galaxy is possibly teaming with life according these authors particularly in the G & K class stars in the Galactic HZ. How many Planets may be there in that galactic habitable zone? We consider life itself is fairly common throughout this galaxy. How can we estimate the number of technological civilizations that might exist among the stars? While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake (now he is the Chairman of the Board of the SETI Institute) conceived an approach to bind the terms involved in estimating the number of technological civilizations that may exist in our galaxy. The Drake Equation[3], as it has become known, was first presented by Drake himself in 1961 and identifies specific factors thought to play a role in the development of such civilizations. Although there is no unique solution to this equation, it is a generally accepted tool used by the scientific community to examine these factors The equation is usually written:
N = R* x fp x ne x fl x fi x fc x L Where, N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable., R* =The rate of formation of stars suitable for the development of intelligent life. ,fp = The fraction of those stars with planetary systems. ne = The number of planets, per solar system, with an environment suitable for life. fl = The fraction of suitable planets on which life actually appears.fi = The fraction of life bearing planets on which intelligent life emerges. fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space. L = The length of time such civilizations release detectable signals into space. Drake himself estimates the final number of communicating civilisations in the galaxy to be about 10,000. As per Drake, we may calculate, for example- 0.333333333 7,300,613.497 planets may be containing any kind of life, intelligent or not. 0.333333333 973415.1329 "Jurassic" worlds or any other whose most intelligent species is sub-sentient. 0.333333333 12.16768916 planets whose most intelligent species is within (but not over) 5000 years of current Western World technological development i.e. ~ 12 worlds with 'planets whose most intelligent species is within [where life evolved without artificial intervention] . So planets with 'advanced technical civilizations are quite rare, if we consider civilizations not more than 5000 years old and If the average age of a civilization is a million years, that increases the number of intelligent species civilizations to 2400, In 2001, For the first time, the researchers estimated how many planets might lie in the "habitable zone" around stars, where water is liquid and photosynthesis possible. The results suggest that an inhabited Earth-like planet could be as little as a few hundred light years away. So it is obvious that within the limits of our existing technology, any practical search for distant intelligent life must necessarily be a search for some manifestation of a distant technology, The National Research Council of US has emphasized the relevance and importance of searching for evidence of the electromagnetic signature of distant civilizations.
The big yet unsolved question is “are we alone in this universe?” If and even multi universes are present then is there also chance of development of life in planet or phantasmal in those universe? Paul Devis of Australian center for astrobiology Macquire university retired the claim of astro-biologists that life is cosmic in pattern bound to arise under earth like conditions and likely to spread across the galaxies. He raised first question ‘are we alone in the cosmic eternity” Or life also existed in extraterrestrial planets or atmosphere or in asteroids where from it came through a rocket system. Our heavenly [in 2006] mom late Mrs Bani Bhattacharya, of 7/51 Purbapalli, sodepur, 24 Parganas(north) Kol-110,west Bengal,India, used to tell our brothers and sister in our child hood such peculiar stories. She had auditory hallucination. She had a false belief of Panspermia. People from extra terrestrial of other galaxies, other planets used to tell her various stories or used to speak with her. Really civilized life also exist in extraterrestrial planets or atmosphere or other universe? If it was so, on the countless other planets that may circle other sun, in same distances from their sun, as our earth circle our sun in a distance, life may exist. It may exist as organic molecule like carbon molecule based life, as life on our earth [then there the evolutionary pattern would be same as it happened in our earth] or they may be different. Based on other molecule (say silica based, Iron based, sulpher based) with other type of evolutionary system and adaptation to their environment. What we think about life is based on chains of Carbon atoms with a few atoms life phosphorus, sulpher and Nitrogen. One may speculate that one may have life with some other chemical basis such as silicon but carbon atoms should have most favorable case(Life in the universe sated By Prof. S.W. Hawkings FRS) Francis Crick, the Nobel Laureate for discovering the double Helix structure of DNA molecule, once wrote ostensibly to answer “ Enrico Framis”- another Nobel laureate for his famous question “ …if there are intelligent beings in the galaxy why are they only in earth?” and Crick assessed the hypothesis known as “ Directed Panspermia hypothesis”, that is to say a variant of Arrethenious 19th century theory modified, in that Crick considered “whether life was deliberately planted in earth by some God?” i.e. evolution from extraterrestrial space?. Answer that Francis Crick gave to Enrico Framis “ ….that life on earth could well have originated elsewhere in the galaxy and that there had been time enough for intelligent beings to evolve elsewhere. A suitable environment and to have dissipated prokaryotic and Eukariotic microorganisms by rocket or asteroid to this planet where life may have developed” Crick however admitted that the theory of “Directed Panspermia” although suffered from possible paucity of evidences.
In the great darkness of Space Time, between stars there are Condensed Dark Matter(composed of gas, dusts, organic matter) with dozens of different kinds of organic molecules. The abundance of these molecules further suggests that stuff of life is everywhere in the cosmos. A very pertinent question raise present author’s mind “ Is our universe is specially designed to produce Human race?” The possibility of life is on some of thousands of planets in our Milky Way galaxy even or in other galaxies of universe or may be in other universes if there are multi universes as per string theory. Life may never arose some where, on the other hand it may arose and died and or never evolved beyond the simplest form or in some planets there may be life which developed more intelligent civilization, more advanced then human civilization on the surface of earth. The biologists and physicists say that our planet “the Earth” is perfectly suitable one for evolution now. Moderate temperature, liquid water, Oxygen, Nitrogen in air, green house effect and so on were helpful for development of life here. We the earthlings are supremely well adapted to this environment, because we grew up here in three-dimensional form from three-dimensional molecule very complex organic molecule DNA/RNA in three dimensional-time on this earth.
In the beginning of our universe, many says there was the Big Bang, and only physics, the mostly and yet undiscovered laws of universe. Then chemistry came along at milder temperatures; when elementary particles quarks with its color ultimately formed nucleons and then atoms; “……There were no carbon when universe began in 15 billions years ago. It was so hot that all the matters were in form of quarks and then protons and neutrons. However as the universe expanded ii became cool. After one minute of the Big Bang the temperature fell to billion degrees at which temperature neutrons started to decay to protons. If these happened then all the matter in the universe ended up into simple matter Hydrogen. Some of the neutrons probably collided with protons and stuck together to form next element Helium whose nucleus consist of two(2) neutrons and Two(2) protons. But no elements like Carbon, oxygen, nitrogen, phosphorus, sulpher in the early universe. The universe continued to expand and cooled. Some regions would have higher density then others. The gravitational attraction of extra matter in those regions slowed down their expansion and eventually stopped expansion. And they collapsed to form proto galaxies – galaxies- stars starting about two billions years from the Big Bang moment.. From the stars planets were formed . Our solar system was formed about ten billions years after the Big Bang. The earth was formed largely out of the heavier elements including, Hydrogen, carbon, oxygen….”[2]. These united to give more and more complex organic molecules ever most complex largest molecule on earth the RNA, DNA, enzymes, genes, epegenes which in turn associated into organized aggregates and cell membranes, defining the most primitive cells out of which life emerged in this planet. CHEMISTRY and BIOCHEMISTRY may be then considered is the science of matter and of its transformations, and LIFE in this planet is its highest form of expression of Bio chemistry. Chemistry and notably supra molecular chemistry thus entertained a double relationship with biology of life in this planet. The progression from elementary particles to the nucleus, the atom, the molecule, the super molecule RNA and the supra molecular assembly of bio organic represents steps up the ladder of supra intelligence complexity that happened here. Particles interacted to form atoms, atoms to form molecules, molecules to form super molecules and supra molecular assemblies, etc. At each level a novel features appeared that however did not exist at a lower one. Thus a major line of development of chemistry to form life is towards more and more complex systems and the emergence of complexity. The highest level of complexity is that expressed in that highest form of matter, living matter, life, which itself culminated in the human brain, the plasticity of the neural system, epigenesis, consciousness and thought. For this what took the active role is the Darwinian evolutions that might also be brought into parallel with the recent development, via procedures of both chemical synthesis and molecular biology, of molecular diversity methods that combined the generation of large repertoires of molecules with highly efficient various selection procedures , adaptations, conflicts, to obtain products presenting specific properties the techniques of amplification by replication used in these methods would bear relation to the spontaneous generation of the target superstructures by the operation of self processes.
An excess of L-amino acids was detected in Murchison and Murray, two meteorites of the carbonaceous chondrite class ,although some discrepancies in the reported results remain to be yet resolved. Cronin et al. (4) originally discarded the evidence for small excesses of L-enantiomers in Murchison as controversial and possibly caused by terrestrial contamination. Later, however, they themselves found an enantiomeric excess of various amino acids that have never been reported, or are of limited occurrence, on Earth (5 ;6). The detection of a significant 15N enrichment in individual amino acid enantiomers from Murchison, when was compared with their terrestrial counterparts, it confirmed that the source of these amino acids was extraterrestrial and not any terrestrial contamination. Carbonaceous chondrites formed ~4.5 billion years ago (i.e., before the origin of life on Earth). There is still some controversy regarding the actual origin of those meteoritic amino acids (i.e., on the meteorite parent body via Strecker synthesis in liquid water [3,5] or in the interstellar medium followed by incorporation into the parent body [4, 6]. Experiments with interstellar ice analogues have shown that the UV-light–induced synthesis of amino acids was possible under the types of conditions likely to be found in interstellar dust (8, 9). No matter which scenario is the correct one, the finding of an excess of L-amino acids in carbonaceous chondrites strongly suggests that the excess is of extraterrestrial origin and existed in the solar system before the origin of life on Earth.
The experiments further indicated that at least some amino acids do not undergo complete racemization during their residence in space, transit to Earth, atmospheric entry, and surface impact. The -methyl amino acids found to exhibit considerable excess of the L-enantiomer in the Murchison meteorite are reportedly quite resistant to racemization (5). Racemization half-lives of meteoritic -amino acids, the ones used for protein synthesis in contemporary terrestrial organisms, were calculated from models, taking into account the various environments that such an amino acid was exposed to in space (10). In the temperature range between 150 and 300K, the racemization half-lives varied between amino acids by approximately 5 orders of magnitude, with glutamic acid and iso-leucine predicted to retain an enantiomeric excess much longer than phenylalanine, aspartic acid, and alanine. These calculations suggested that the reported D/L value for glutamic acid in Murchison of 0.3 (8) was close to the original value, whereas that of alanine (D/L = 0.5) could correspond to original values in the range of 0.5 to 0.35 (10 ). Note, however, that others did not observe any enantiomeric excess in alanine (11 ). Other experiments suggested that amino acid racemization at high temperatures, as may be encountered during atmospheric entry and surface impacts of space bodies, would be very rapid (12 ). Incorporation into rocks of a size to prevent their being heating all the way through should, however, overcome this problem. The presence of a variety of amino acids in meteorites raises the further question of whether not only the source of enantiomeric excess in terrestrial amino acids but also possibly the provenance of pre-biotic amino acids themselves was extraterrestrial. Meteorites are actually considered unlikely to have made a significant contribution to the total amount of pre-biotic organics (13, ). In contrast, impacts of carbonaceous asteroids and comets during the period of heavy bombardment 4.5–3.8 billion years ago are thought to have been important sources not just of amino acids but also a variety of prebiotic organic molecules (14, 15). Even greater amounts of organic material are likely to have been accreted from interplanetary dust particles, which are currently contributing ~3.2 x 105 kg year-1 of intact organics. How large a portion of the total inventory of organics on early Earth came from extraterrestrial sources depends on a variety of factors, foremost among them the actual composition of Earth’s early atmosphere and hence the extent of endogenous production. Whereas Miller and Urey assumed a fully reducing early terrestrial atmosphere for their famous experiments, it is now thought that it was non reducing or slightly reducing (15–17). The efficiency of organic synthesis decreases rapidly as a function of the H2/CO2 ratio. It has been calculated that with UV light as the energy source, a yearly production of 2 x 1011 kg organics would have occurred in a reducing atmosphere, whereas only 3 x 108 kg year-1 would be produced in a neutral atmosphere (H2/CO2 = 0.1) (15). Recent experiments suggested that high-energy particles, but not UV light, were able to generate amino acid precursors under mildly reducing conditions (13). The delivery to Earth of large amounts of extraterrestrial carbonaceous compounds, including many of the building blocks of life, might actually fall under a new expanded definition of panspermia (18). Originally, however, the term panspermia was referred to the transfer of some form of viable extraterrestrial organism. Theoretically, the transfer of such organisms between planets within our solar system is possible on rocks ejected by large impacts (19). A majority of these ejecta were heated to temperatures that would kill all microbes; however, some remain almost un shocked (20). Further heating during the ascent through the atmosphere of the home planet requires that the ejecta be of a size that prevents heating to 100°C all through, with a diameter of >0.2 m estimated as necessary. Similar heating occurs during the entry into and passage through the atmosphere of the target planet and the landing there. In between, microbes would have to survive thousands of years of travel through space. Space is a very hostile environment in which UV and ionizing radiation, extreme vacuum, and very cold temperatures individually, and even more so in combination, are potentially lethal (13). Theoretical and experimental results indicate, however, that protection from these sterilizing factors however may be possible (13). The ability of some bacteria to form spores makes them attractive candidates for extraterrestrial organisms that might have introduced life to Earth (21). Spores represent a dormant state. This offers the advantage of the absence of (detectable) metabolism and high resistance to a variety of physical insults, including those imposed by prolonged space travel. Only a small proportion of spores were found to survive space travel of up to 6 years (i.e., a minute fraction of the actual time they may have to spend in space during transfer between planets [ 21]). A single living organism may be enough to seed life on another planet, however. Pan spermia theories offer the advantage of overcoming the difficulties arising from the shortness of the time interval during which life on Earth must have become established. Life could not have arisen, or would have been destroyed if it did, during the heavy bombardment period that ended about 3.8 Gyr ago. Microfossils and stromatolites indicate that complex life must have originated more than 3.5 Gyr ago, and evidence of biologically mediated carbon isotope fraction puts the existence of life back even farther, to ~3.8 Gyr ago. Some biologists say that life must have arisen around 10 billion years ago .This leaves a very narrow window of time for the emergence of terrestrial life and adds some plausibility to scenarios in which a preformed extraterrestrial life form started life on Earth. Ultimately, however, postulating an extraterrestrial origin not just for organic bio molecules but for entire organisms simply shifts the location of the origin of life, without addressing the underlying questions of how life arose and at what point during this process homo chirality became established. Clearly the questions of life’s origin and the relationship of its emergence to the phenomenon of homo chirality are the subject of active investigation. To conclude this review, we are struck by the ‘‘symmetry’’ of some of the possible mechanisms linking these questions and the expressions of these in aspects of biology. Homo chirality, a prerequisite of life’s emergence in some scientists’ view, might arise as a consequence of the roles played by cosmology (e.g., by cold dark matter and cold dark energy) and occur at the far edge of galaxies. The conjunction of these (the dark) with our increasing understanding of the processes that control nuclear fusion and supernovas in providing both the building blocks and the energy (the light) to drive life’s processes leads us to conclude with a quote alluding to the symmetry of light and dark. Thus the darkness bear its fruit, and prove itself
Now a days, the multi- universe concept is a hot topic for discussion at real-world scientific conferences. The question arises as to whether all these other universes are going to be like ours “or whether they will have different laws and the laws in our universe are in some sense special. String theory, a favorite candidate (although unsubstantiated by experiment) for explaining all of physical laws of universe; suggest that the multi universe encompasses bubbles hosting various sorts of physics. String theory predicts the existence of an enormous number of different “vacuum states,” or space time bubbles with different properties, such as physical constants or particle masses. Of an infinite number of bubbles, there could be 10500 different varieties. And though any underlying basic law of physics would remain the same, the bubbles could nonetheless exhibit vast physical diversity. Some of those bubbles would not have lasted long enough for life, inflating but then shrinking before any interesting chemistry commenced. Others would expand forever, as seems the case with the bubble that humans occupy. In some, the local laws of physics would have welcomed living things; others would have permitted none of the particles and forces that conspire to build atoms, molecules and metabolic mechanisms. It seems that universes come in all sizes and flavors, with the bubble being the Goldilocks version, just right for life. In other words, if the multiverse offers multiple bubbles that permit life to evolve, humans would most likely live in an average bubble. If, for instance, you throw out all the bubbles that wouldn’t allow life anyway, and then calculate the average temperature of space in those that remain, humans should measure a cosmic temperature that is not very far off from that average. Somewhere in the cosmos, such a random mix of molecules has produced a brain identical to yours in every respect, neurons in identical configurations, with all your memories and perceptions
Stars in our Galaxy Milky way- estimates: 500 Billion ( Royal Greenwich Observatory. And these stars include everything from M-Class (Red Dwarfs) to Enormous O- Class Stars (very hot, very fast burning, Blue stars). Our own star sun is Class G. Stars. K class stars are - The cooler and “redder” the star, the longer it remains on the main sequence (barring the obvious exception of red giants). The previously-mentioned O-Class (very hot blue) stars will likely last only a few dozen million years, barely enough time for star dust to coalesce into planets. Furthermore, hotter stars emit enormous quantities of ionizing radiation (UV or higher). In fact, large stars tend to emit the bulk of their radiation in the UV band. Stars in classes B (a lower level blue-white) and A (white) suffer similarly, though to not to the extreme extent as O-class ones. Nevertheless, these stars will last only a few billion years at most. This may be long enough for simple life and perhaps even the simplest animal life to form, but not likely enough to allow technologically advanced life to arise (unless its evolution is incredibly quick). F-class (white) is likely to last from 4 to 6 billion years, certainly enough to give rise to complex life (perhaps even intelligent life). Unfortunately, in the Earth-term timeline at least, a white sun will start to leave the main sequence just when intelligence does arise. Timing truly is everything. So while it’s certainly possible and even plausible for a white sun to have a technically advanced civilization, I don’t find it particularly likely.
By contrast, the red dwarf (M-class) stars will be around for billions of years, much more than enough time for life to form. Furthermore, they do not emit as much ionizing radiation as even our own sun (G-Class), another factor favoring a life-friendly environment. Unfortunately, the cooler the star, the narrower its life zone. I personally interpret this fact to mean that a red star’s HZ will be less likely to contain a planet of any sort, let alone one with other preconditions necessary for life to have a chance on it. Even if the red sun’s HZ does have a planet with the appropriate gravity, atmospheric and other characteristics, odds are fairly high that the planet will suffer from “rotation lock” (one face always facing the star). This means one side will be in eternal day or close to it (thus rendering it too hot) and one side will be in eternal night (rendering it too cold). However, there is still at least some chance other mitigating factors will come to play on such a planet (the hot spot over the planet may create atmospheric convection that creates winds, thus spreading heat more evenly over the planet). Obviously, a rotationally-locked planet’s twilight zone could offer a happy medium in which life, and even intelligence can flourish in theory. However, as I will discuss later, such a planet will have a much more difficult time developing a sustainable high technology civilization, and even a high-end pre-industrial civilization. G (yellow), K (orange), and low-level white stars as places favorable for advanced civilization to arise. If we include all G and K stars, plus about 1/3 of all F stars, these stars are about 22% of all stars in the galaxy ( Wikipedia). If M-class (red) stars - 78% of all stars - permit HZ planets without a rotation lock, then perhaps another 10 % of all stars (the hotter M-class ones) can be added to (though I admit this number is rather arbitrary). So we can say that as many as 33% of all stars could support a technical civilization, given other necessary planetary conditions listed above. Such stars that are the appropriate age - If you are content with finding significant life in any form, you will likely find it around planets between two and five billion years old. This is certainly long enough for life to form an Oxygen atmosphere (strong evidence of life), though not necessarily sentient life. Hopefully, by 2016-2020 the Terrestrial Planet Finder (TPF) project will finally give the answers we all want--where there are rocky crust planets orbiting around G to K class stars within 200-300 light years of Earth. The TPF mission will survey number of Earth-sized planets in habitable zone orbits in the galaxy
Any special Signal received yet by SETI? In August 1977, an Ohio State University radio telescope detected an unusual pulse of radiation from somewhere near the constellation Sagittarius. The nearest star in that direction is 220 million light years away. The 37-second-long signal was so startling that an astronomer monitoring the data scrawled "Wow!" on the telescope's printout. The signal was within the band of radio frequencies where transmissions are internationally banned on Earth[3] In February 2003, astronomers with the search for extraterrestrial intelligence (SETI) project, used a massive telescope in Puerto Rico to re-examine 200 sections of the sky which had all previously yielded unexplained radio signals. These signals had all disappeared, except for one which had become stronger. came from a spot between the constellations Pisces and Aries. SETI has many signal detectors type. Recently in 2008 SETI signal detector called SonATA (SETI on the ATA). Son ATA does everything that Prelude does, but it is a software-only detector, capable of operating on commodity servers, without the special-purpose hardware accelerators that had to be built into Prelude to make it run in near-real time .On October 9, 2008 the X-band signal from the Rosetta spacecraft was detected by the SonATA as a demo system! Figure 1 shows that detection. The Rosetta X-band signal is much stronger than the signals from [4]Voyager fig1- Figure-. After a half-century of scanning the skies,SETI astronomers today have little to report. Why?. The problem could be that SETI had been so long looking in the wrong place, at the wrong time, and in the wrong way. "Why to waste time looking for old-style radio signals? The advanced and intelligent aliens may use entangled particles like neutrinos or some form of gravity waves to signal us Figure-1
The origin of all life was at first RNA and then DNA and the first cell and all life has the same depth of evolution; there is no reason to expect anything meaningful to come from the figure shown bellow. Taking two of the points shown on the figure, those for fish and mammals which shared a common ancestor around 500 million years ago; of what relevance to the origin of life has been the faster development of non-redundant genes in the lineage leading to mammals? Use of the hypothesized time of ‘origin’ of Eukaryotes , occurred around 2 bya is particularly unfortunate. Firstly we don’t have any certainty about the timing of the origin of eukaryotes. Comparative genomic analyses led Hedges (2002) and Feng et al., (1997) to conclude that the first Earthly multicellular eukaryote, had evolved by 2.7 bya, but the first proto-eukaryotes may have evolved around 4 bya (Hedges et al., 2001). There are also microfossils dated to 3.8 bya which have been interpreted as simplified eukaryotes (Plfug 1984). Others have cited this evidence to argue that eukaryotics did not evolve on Earth, but also have an ancestry which predates the origins of this planet (Joseph 2009; Joseph and Schild 2010).
Secondly, the development of eukaryotes was arguably the greatest leap in evolution since the origin of the first self-replicating cell; certainly not within the gradualism camp since it resulted from a series of rare cell-fusions of prokaryotic cells. Once again, we might ask of what relevance to the timing of the origin of life was this serendipitous event? It is wrong to place the origin of the prokaryotic cell at 3.5 Gigayears ago. Although we have evidence of the existence of prokaryotes at that time we also have evidence that their phylogeny, on Earth, runs much deeper from 3.8 bya (Mojzsis, et al., 1996; Pflug, 1978; Rosing, 1999, Rosing and Frei, 2004) to 4.2 bya (Nemchin et al. 2008; O'Neil et al. 2008). Prokaryotic life appeared on Earth shortly after life became possible on this planet (Joseph and Schild 2010). It we accept the Sharov's (2010) contentions, they may well have existed 10 billion years ago.
In Our view all life-forms we might find in the outer solar system will share the genetic codes may be familiar to us. Any experimentation with alternative genetic systems in primordial cells would have been snuffed out by the development of the RNA world (Gilbert, 1986), which in turn was snuffed out (with the possible exception of some RNA viruses) by the DNA world. The important question remaining is whether both Prokaryotes and Eukaryotes are represented among these life-forms.
We authors think that many alien intelligent species (perhaps 2 or 3 percent of them) would look like humanoid as they look, act, think and feel amazingly like ourselves with probable some kind of appendages evolved for manipulation, locomotion. These appendages can have evolved from any movable body parts, including parts of the locomotors apparatus (limbs), feeding apparatus (mouth parts like lips or mandibles), respiratory apparatus (gills), or sensory apparatus (antennae).s Earthlike worlds with slightly more gravity would tend to produce centauroids. The nearest centauroid might look like the upper part of a gorilla transplanted on the body of a donkey, for example. And its two eyes might be above each other, rather than side by side. Earthlike worlds with slightly less gravity would tend to produce flying aliens. Some might look like bats, others like octopoi with a balloon-like body, yet others like living monoplanes, with their manipulative extremities tucked away inside their mouths. In a dense atmosphere a life form might look like a living umbrella, which keeps a loft by opening and closing itself. Earthlike worlds with vast tracts of level ground might have inhabitants which look like giant wheels. The outside of the wheel might be covered with tiny mouths used for grazing. Ant like creatures and some reptile like, some are giant larger than elephant also, may be possible, and some like octopus also, aliens are aliens even we are aliens for them
20] Mileikowsky C, Cucinotta FA, Wilson JW, Gladman B, Horneck G, Lindegren L, Melosh J, Rickman H, Valtonen M, Zheng JQ. Natural transfer of viable microbes inspace. Icarus 145:391–427, 2000
21] Horneck G, Rettberg P, Reitz G, Wehner J, Eschweiler U, Strauch K, Panitz C, Starke V, Baumstark-Khan C. Protection of bacterial spores in space, a contribution to the discussion on panspermia. Orig Life Evol Biosph 31:527–547, 2001.
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