 The existence of extraterrestrial life remains hypothetical though human beings continue to search Extraterrestrial life is life that may exist and originate outside our planet Earth. Its existence is currently hypothetical: there is as yet no evidence of extraterrestrial life that has been widely accepted by scientists. Life is a multi-faceted concept. ...
Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third planet outward from the Sun. ...
Speculative forms of extraterrestrial life range from humanoid and monstrous beings seen in works of science fiction to life at the much smaller scale of bacteria and viruses. The term humanoid refers to any being whose body structure resembles that of a human. ...
Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ...
Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...
Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). ...
Extraterrestrial life forms, especially intelligent ones, are often referred to in popular culture as aliens or ETs. The putative study and theorisation of ET life is known as exobiology. In popular fiction and conspiracy theories, life forms, especially intelligent life forms, that are of extraterrestrial origin, i. ...
Astrobiology (in Greek astron = star, bios = life and logos = word/science), also known as exobiology (Greek: exo = out) or xenobiology (Greek: xenos = foreign) is the term for a speculative field within biology which considers the possible variety of extraterrestrial life. ...
Possible basis and origins of extraterrestrial life
All life on earth is based on the building-block element carbon with water as the solution in which bio-chemical reactions take place. Given their relative abundance and usefulness in sustaining life it has long been assumed that life forms elsewhere in the universe will also utilize these basics components. However, other elements and solvents might be capable of providing a basis for life (See also: Non-carbon biology). Silicon is usually considered the most likely alternative to carbon, though this remains improbable. Lifeforms based in Ammonia rather than water are also considered, though less frequently. We cannot also reject the possibility that a completely new substance may be found that may react in a similar way to carbon or that wholly unique, non-chemical lifeforms may possibly flourish through exotic physics. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...
Water (from the Old English word wæter and the German word Wasser) is a colorless, tasteless, and odorless substance in its pure form that is essential to all known forms of life and is known also as the most universal solvent. ...
Life is a multi-faceted concept. ...
Non-carbon biology collectively refers to an assortment of astrobiology theories and hypotheses in which life is based on another element than carbon, which is the fundamental element of all currently known forms of life. ...
General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ...
Ammonia is a chemical compound with the formula NH3. ...
Along with a building block element and a solvent, life also requires an energy source. Energy from a parent star is the most obvious source for extraterrestrial life but this is not the only possiblity, as the example of terrestrial extremophiles shows. Geo-thermic energy from a planet's interior, for instance, may drive sub-surface life, while tidal flexing (i.e., for bodies orbiting a gas giant) provides another possible motor to sustain living things. An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions. ...
The tidal force is a secondary effect of the force of gravity and is responsible for the tides. ...
The scientific study of the possible biochemical basis for extraterrestrial life is often called xenobiology. Astrobiology (in Greek astron = star, bios = life and logos = word/science), also known as exobiology (Greek: exo = out) or xenobiology (Greek: xenos = foreign) is a speculative field within biology which considers the possible variety of extraterrestrial life. ...
Most scientists hold that if extraterrestial life exists, its evolution would have occurred independently in different places in the universe. An alternative hypothesis, held by a minority, is panspermia, which suggests that life in the universe could have stemmed from a single initial distribution of spores which provide the basis for living beings to develop. If true, this theory would suggest that life in various forms may exist throughout the universe. Panspermia is the hypothesis that the seeds of life are prevalent throughout the universe, and furthermore that life on Earth began by such seeds landing on Earth and propagating themselves. ...
Silicon-based life Silicon-based life is regarded as improbable by most scientists. Superficially, the chemistries of carbon and silicon are similar; just as carbon can form methane (CH4), silicon can form silane (SiH4), and both elements can form long chains of polymers. The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ...
Silane is a chemical compound with chemical formula SiH4. ...
A polymer is a generic term used to describe a substantially long molecule. ...
But silicon's affinity for oxygen means that it cannot easily be used for respiration. Whereas CO2 is a gas that can easily be removed from the organism, SiO2 is a solid that will instantly organize itself into lattices, making it hard to dispose of. On top of that, silicon fails to give rise to many compounds that exhibit chirality, which is a common feature of carbon-based molecules that are essential to the proper functioning of enzymes. General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...
Respiration can refer to: Cellular respiration, which is the use of oxygen in the metabolism of organic molecules. ...
In chemistry, a molecule is chiral if is not superimposable on its mirror image regardless of how it is contorted. ...
Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ...
There is also astronomical evidence to suggest that silicon-based life is unlikely. Wherever astronomers have looked, they have failed to find the simplest precursors to silicon-based biochemistry. Complex carbon-based compounds are abundant in space, but in the case of silicon, most of what we have observed in space are simple oxides of silicon, with no record of more complex molecules such as silanes and silicones. Silicones, or polysiloxanes, are inorganic polymers consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. ...
Ammonia-based life All life on Earth is based on water and its numerous chemical properties, and indeed a large portion of modern chemistry is devoted to the study of aqueous solutions. However, numerous chemical reactions are possible in an ammonia solution, and liquid ammonia has some chemical similarities with water. Ammonia can dissolve most organic molecules at least as well as water does, and in addition it is capable of dissolving many elemental metals. Given this set of chemical properties it has been theorized that ammonia-based life forms might be possible. Water (from the Old English word wæter and the German word Wasser) is a colorless, tasteless, and odorless substance in its pure form that is essential to all known forms of life and is known also as the most universal solvent. ...
Ammonia is a chemical compound with the formula NH3. ...
However, ammonia does have some problems as a basis for life. The heat of vaporization of ammonia is half that of water and its surface tension three times smaller. This means that hydrogen bonds between ammonia molecules will always be much weaker than those in water, so ammonia is less able to concentrate non-polar molecules through a hydrophobic effect. For this reason, mainstream science questions how well ammonia could hold prebiotic molecules together in order to allow the emergence of a self-reproducing system. The heat of vaporization is a physical property of substances. ...
In physics, surface tension is an effect within the surface layer of a liquid that causes the layer to behave as an elastic sheet. ...
In chemistry, a hydrogen bond is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity. ...
In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ...
A biosphere based on ammonia would likely exist at temperatures or air pressures that are extremely unusual for terrestrial life. Terrestial life usually exists within the melting point and boiling point of water at normal pressure, between 0°C (273 K) and 100°C (373 K); at normal pressure ammonia's melting and boiling points are between −78°C (195 K) and −33°C (240 K). Problems with biospheres at extremely cooled temperatures are that biochemical reactions are slowed down tremendously as well as some biochemicals may precipitate out of solution due to high melting points. Ammonia could be a liquid at normal temperatures but at much higher pressures, for example at 60atm ammonia boils at 98°C and melts at −77°C. The biosphere is that part of a planets outer shell—including air, land, and water—within which life occurs, and which biotic processes in turn alter or transform. ...
Atmospheric pressure is the pressure caused by the weight of air above any area in the Earths atmosphere. ...
The degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. ...
The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ...
The melting point of a solid is the temperature at which it changes state from solid to liquid. ...
When expressed as a measurement, an atmosphere or standard atmosphere is a unit of pressure roughly equal to the average atmospheric pressure at sea level on the earth. ...
Ammonia-water mixed solution could provide conditions for a water like biochemistry at lower temperatures then water normally supports. And such conditions could exist under the surface of the Saturn's largest moon Titan [1]. Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ...
Titan (tye-tun, Greek Τιτάνας) is the largest moon of Saturn and the second largest moon in the solar system[1], after Jupiters moon Ganymede. ...
Beliefs in extraterrestrial life
Ancient and Early Modern Ideas Belief in extraterrestrial life may have been present in ancient Egypt, Babylon and Sumer although in these societies cosmology was fundamentally supernatural and the notion of aliens is difficult to distinguish from that of gods, demons etc.. The first important Western thinkers to argue systematically for a universe full of other planets and, vicariously, possible extraterrestrial life were the ancient Greek writers Thales and his student Anaximander in the 7th and 6th century BCE. The atomists of Greece took up the idea, arguing that an infinite universe ought to have an infinity of populated worlds. Ancient Greek cosmology worked against the idea of extraterrestrial life in one critical respect, however: the geocentric universe, championed by Aristotle and codified by Ptolemy, priviliged the Earth and Earth-life (Aristotle denied there could be a plurality of worlds) and seemingly rendered extraterrestrial life impossible. Babylon (Confusion) is a later name given to the city of Babel. ...
Sumer (or Shumer, Sumeria, Shinar, native ki-en-gir) formed the southern part of Mesopotamia from the time of settlement by the Sumerians until the time of Babylonia. ...
Look up Cosmology in Wiktionary, the free dictionary For the jazz band, see: Cosmology (band) Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) world + λογια (logia) discourse) is the study of the universe in its totality and by extension mans place in it. ...
Thales (in Greek: Θαλης) of Miletus (circa 635 BC - 543 BC), also known as Thales the Milesian, was a pre-Socratic Greek philosopher and one of the Seven Sages of Greece. ...
Anaximander (609/610 BC - c. ...
Atomism is the theory that all the objects in the universe are composed of very small particles that were not created and that will have no end. ...
The geocentric model (in Greek: geo = earth and centron = centre) of the universe is a paradigm which places the Earth at its center. ...
Aristotle (sculpture) Aristotle (Greek: ΑÏιστοτÎλης AristotelÄ“s) (384 BC – March 7, 322 BC) was an ancient Greek philosopher. ...
Claudius Ptolemaeus, given contemporary German styling, in a 16th century engraved book frontispiece Claudius Ptolemaeus (Greek: ΚλαÏδιος Πτολεμαῖος; c. ...
When Christianity spread through the West the Ptolemaic system became dogma and although the Church never issued any formal pronouncement on the question of alien life [2], at least tacitly the idea was heretical and dangerous to publicly support. The best known early-modern proponent of extra-solar planets and widespread life off Earth was Giordano Bruno, who was burned at the stake for this and other unorthodox ideas in 1600. The Church, however, could not contain the storm that accompanied the invention of the telescope and the Copernican assault on geocentric cosmology. Once it became clear that the Earth was merely one planet amongst countless bodies in the universe the extraterrestrial idea moved toward the scientific mainstream. William Herschel, the discoverer of Uranus, was one of many 18th-19th astronomers convinced our Solar System, and perhaps others, would be well populated by alien life. Other luminaries of the period who championed "cosmic pluralism" included Voltaire and Benjamin Franklin. At the height of the Enlightenment even the Sun and Moon were considered candidates for hosting aliens. The Christian attitude toward extraterrestrials turned from denial to ambivalence. Theological criticisms had been partially stalemated by a critical counter-argument: to deny that God could and did create off-Earth lifeforms was, on some level, a denial of His omnipotence. Wikipedia does not have an article with this exact name. ...
Wikipedia does not have an article with this exact name. ...
Christianity is a monotheistic religion based on the life and teachings of Jesus of Nazareth as presented in the New Testament writings of his early followers. ...
Giordano Bruno Giordano Bruno (1548 – February 17, 1600), a. ...
50 cm refracting telescope at Nice Observatory. ...
In astronomy, heliocentrism is the theory that the Sun is at the center of the Universe and/or the Solar System. ...
Sir Wilhelm Friedrich Herschel (Hanover, November 15, 1738 – August 25, 1822 Slough, then in Buckinghamshire now in Berkshire) was a German-born British astronomer and composer who became famous for discovering the planet Uranus, and made many other astronomical discoveries. ...
Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ...
Voltaire François-Marie Arouet (November 21, 1694 – May 30, 1778), better known by the pen name Voltaire, was a French Enlightenment writer, deist and philosopher. ...
Benjamin Franklin by Jean-Baptiste Greuze 1777 For the former mayor of Nepean, see Ben Franklin (politician) Dr. Benjamin Franklin (January 17, 1706 – April 17, 1790) was an American printer, journalist, publisher, author, philanthropist, abolitionist, public servant, scientist, librarian, diplomat, and inventor. ...
For the period in European history, The Age of Enlightenment For the corresponding movement in the European Jewish community, see Haskalah. ...
A sun is the star at the center of a planetary system. ...
Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ...
Extraterrestrials and the Modern Era This enthusiasm toward the possibility of alien life continued well into the 20th century. Indeed, the roughly three centuries from the Scientific Revolution through the beginning of the modern era of solar system probes were essentially the highpoint for belief in extraterrestrials in the West: many secular thinkers, at least some religious thinkers, astronomers of all stripes, and much of the general public were largely satisfied that aliens were a reality. This trend was finally tempered as actual probes visited potential alien abodes in the solar system. The moon was decisively ruled out as a possibility, while Venus and Mars—long the two main candidates for extraterrestrials—showed no obvious evidence of current or past life. The other large moons of our system which have been visited appear similarly lifeless, though interesting geothermic forces observed (Io's volcanism, Europa's ocean, Titan's thick atmosphere) has underscored how broad the range of potentially habitable environments may be. Finally, the failure of NASA's SETI program to detect anything resembling an intelligent radio signal after four decades of effort has partially dimmed the optimism that prevailed at the beginning of the space age. (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the...
In the history of science, the scientific revolution was the period that roughly began with the discoveries of Kepler, Galileo, and others at the dawn of the 17th century, and ended with the publication of the Philosophiae Naturalis Principia Mathematica in 1687 by Isaac Newton. ...
(*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ...
Mars, with polar ice caps visible. ...
Io or io may stand for: In Greek mythology, Io (IPA or ) was the daughter of Inachus, a river god. ...
In Greek mythology, Europa was a beautiful Phoenician princess. ...
This page is about the moon of Saturn. ...
The National Aeronautics and Space Administration (NASA), which was established in 1958, is the agency responsible for the public space program of the United States of America. ...
The SETI Institute has received limited telescope time at the Arecibo Observatory in Puerto Rico. ...
Thus, the three decades preceding the turn of the second millenium saw a crossroads reached in beliefs in alien life. The prospect of ubiquitous intelligent, space-faring civilizations appears increasingly dubious to many scientists ("All we know for sure is that the sky is not littered with powerful microwave transmitters" in the words of SETI's Frank Drake). At the same time, the data returned by space probes and giant strides in detection methods have allowed science to begin delineating habitability criteria on other worlds and to confirm that, at least, other planets are plentiful though aliens remain a question mark. Professor Frank Drake Frank Drake (born May 28, 1930, Chicago, Illinois) is an American astronomer and astrophysicist. ...
Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ...
Amongst the general public belief and interest in extraterrestrials remains high and scepticism toward galaxy-exploring alien civilizations is not shared by many devotees. At present, some enthusiasts in the topic believe that extraterrestrial beings regularly visit or have visited the Earth. Some think that unidentified flying objects observed in the skies are in fact sightings of the spacecraft of intelligent extraterrestrials, and even claim to have met such beings. Crop circle patterns have also been attributed to the actions of extraterrestrials. While at least one recent scientific paper published in a respected, peer-reviewed journal has urged a reevaluation of the UFO phenomenon (Deardorff et al., 2005) [3], as of this time mainstream scientific opinion holds that such claims are unsupportable by the evidence currently available and unlikely to be true. UFO redirects here. ...
A crop circle pattern Crop circles are areas of cereal or similar crops that have been systematically flattened to form various geometric patterns. ...
The possible existence of primitive (microbial) life outside of Earth is much less controversial to mainstream scientists although at present no direct evidence of such life has been found. Indirect evidence has been offered for the current existence of primitive life on the planet Mars; however, the conclusions that should be drawn from such evidence remains in debate.
Scientific search for extraterrestrial life The scientific search for extraterrestrial life is being carried out in two very different ways, directly and indirectly.
Direct search Scientists are directly searching for evidence of unicellular life within the solar system, carrying out studies on the surface of Mars and examining meteors which have fallen to Earth. A mission is also proposed to Europa, one of Jupiter's moons with a liquid water layer under its surface, which might contain life. Mosaic of Solar System planets except Pluto, including Earths Moon (not to scale). ...
Worlds second largest Meteorite in Culiacan, Mexico A meteorite is a relatively small extra-terrestrial body that reaches the Earths surface. ...
Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pa, /juro:pa/ listen?, Greek Ευρώπη) is a moon of the planet Jupiter, smallest of the four Galilean moons. ...
Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...
There is some limited evidence that microbial life might possibly exist or have existed on Mars. An experiment on the Viking Mars lander reported gas emissions from heated Martian soil that some argue are consistent with the presence of microbes. However, the lack of corroborating evidence from other experiments on the Viking indicates that a non-biological reaction is a more likely hypothesis. And independently, in 1996, structures resembling bacteria were reportedly discovered in a meteorite, ALH84001, known to be formed of rock ejected from Mars. Again, this report is vigorously disputed. NASAs Viking program consisted of two unmanned space missions to Mars, Viking 1 and Viking 2. ...
1996 is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ...
Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...
meteorite fragment ALH84001 ALH84001 (representing Allen Hills 1984 #001) is a meteorite found in Allen Hills, Antarctica in December 1984 by a team of US meteorite hunters from the ANSMET project, among 7,000 others. ...
In February 2005, two NASA scientists reported that they had found strong evidence of present life on Mars (Berger, 2005). The two scientists, Carol Stoker and Larry Lemke of NASA’s Ames Research Center, based their claims on methane signatures found in Mars’ atmosphere that resemble the methane production of some forms of primitive life on Earth, as well as their own study of primitive life near the Rio Tinto river in Spain. NASA officials soon denied the scientists’ claims, and Stoker herself backed off from her initial assertions (spacetoday.net, 2005). However, only a few days after Stoker and Lemke made their claims, scientists from the European Space Agency reported that their own measurements of methane on Mars suggested an organic origin (Michelson, 2005). The National Aeronautics and Space Administration (NASA), which was established in 1958, is the agency responsible for the public space program of the United States of America. ...
Mars, with polar ice caps visible. ...
Southern Europe photographed from space over North Africa The European Space Agency (ESA), established in 1975, is an inter-governmental organisation dedicated to exploration of space with currently 16 member states. ...
Though such findings are still very much in debate, support among scientists for the belief in the existence of life on Mars seems to be growing. In an informal survey of scientists attending the conference at which the European Space Agency presented its findings, 75 percent of the scientists at the conference reported to believe that life once existed on Mars; 25 percent reported a belief that life currently exists there (Michelson, 2005).
Indirect search It is theorised that any technological society in space will be transmitting information. Projects such as SETI are conducting an astronomical search for radio activity that would confirm the presence of intelligent life. The SETI Institute has received limited telescope time at the Arecibo Observatory in Puerto Rico. ...
Astronomers also search for extrasolar planets that would be conducive to life. Current radiodetection methods have been inadequate for such a search, as the resolution afforded by recent technology is inadequate for detailed study of extrasolar planetary objects. Future telescopes should be able to image planets around nearby stars, which may reveal the presence of life (either directly or through spectrography which would reveal key information such as the presence of free oxygen in a planet's atmosphere). It has been argued that one of the best candidates for the discovery of life-supporting planets may be Alpha Centauri, the closest star system to Earth. Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ...
Atomic absorption spectroscopy in analytical chemistry is a technique for determining the concentration of a particular metal element within a sample. ...
General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...
The position of Alpha Centauri Alpha Centauri (α Cen / α Centauri) is the brightest star system (a triple star system) in the southern constellation of Centaurus, and contains the fourth brightest star in the sky, with a total visual magnitude of −0. ...
Extraterrestrial life in the Solar System Many bodies in the Solar System have been suggested as being likely to contain life. The most commonly suggested ones are listed below; of these, four of the five are moons thought to have large bodies of underground liquid, and life may have evolved there in a similar fashion to deep sea vents. - Mars - The best known and most earthlike of the other planets and moons in the Solar system. There was liquid water on Mars in past and possibly there is liquid water beneath the surface. Recently, methane was found the athmosphere of Mars.
- Titan - Only known moon with an atmosphere. Recently visited by the Huygens probe. May have ocean.
- Europa - probably has ocean.
- Ganymede
- Enceladus - May have liquid water beneath surface. [4]
Numerous other bodies have been suggested as potentially life-bearing. For example, atmospheric life has been hypothesised on Venus and the gas giants. Fred Hoyle also proposed that microbial life may exist on comets. Some Earth microbes also managed to survive on a lunar probe for some years. It is considered highly unlikely that complex multicellular organisms exist in any of these places. Mars, with polar ice caps visible. ...
The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ...
Titan (tye-tun, Greek Τιτάνας) is the largest moon of Saturn and the second largest moon in the solar system[1], after Jupiters moon Ganymede. ...
A scale replica of the probe An artists impression of the Huygens probe as it descends through Titans murky, brownish-orange atmosphere of nitrogen and carbon-based molecules, beaming its findings to the distant Cassini orbiter. ...
Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pa, /juro:pa/ listen?, Greek Ευρώπη) is a moon of the planet Jupiter, smallest of the four Galilean moons. ...
Atmospheric characteristics Atmospheric pressure trace Oxygen 100% Ganymede (gan-i-meed, Greek Γανυμήδης) is Jupiters largest moon, and indeed the largest moon in the entire solar system; it is larger in diameter than Mercury but only about half its mass. ...
[3] Atmosphere trace Enceladus (en-sel-a-dus, Greek ΕγκÎλαδος) is a moon of Saturn discovered in 1789 by William Herschel. ...
Sir Fred Hoyle (June 24, 1915 – August 20, 2001) was a British astronomer, notable for a number of his theories that run counter to current astronomical opinion, and a writer of science fiction, including a number of books co-authored by his son Geoffrey Hoyle. ...
Dealing with extraterrestrial life If intelligent extraterrestrial life is found and it is possible to communicate with it, the people of the world and their governments will need to determine how to manage those interactions. The development of policy guidelines for dealing with extraterrestrial beings and territory has been considered by authors such as Michael Salla and Alfred Webre and termed exopolitics. Dr. Michael E. Salla is a pioneer in the development of exopolitics, the scholarly study of the political implications of the extraterrestrial presence that is not acknowledged to the general public, elected officials or the mass media. ...
Alfred Lambremont Webre (born May 24, 1942) is an author, lawyer, environmentalist and a space activist who promotes the ban of space weapons. ...
Extraterrestrial life refers to forms of life that may exist and originate outside of the planet Earth. ...
See also An anomalous phenomenon is an observed phenomenon for which there is no suitable explanation in the context of a specific body of scientific knowledge, e. ...
Astrobiology (in Greek astron = star, bios = life and logos = word/science), also known as exobiology (Greek: exo = out) or xenobiology (Greek: xenos = foreign) is a speculative field within biology which considers the possible variety of extraterrestrial life. ...
Astrosociobiology (also referred to as exosociobiology and xenosociology) is the speculative scientific study of extraterrestrial civilizations and their possible social characteristics and developmental tendencies. ...
The Drake equation (also known as the Green Bank equation) is a famous result in the speculative fields of xenobiology, astrosociobiology and the search for extraterrestrial intelligence. ...
Radio telescope observations play a role in researching the Fermi paradox The Fermi paradox is a paradox proposed by physicist Enrico Fermi that questions the probability of finding intelligent extraterrestrial life. ...
First contact is a term used to describe a first meeting of two previously unknown cultures. ...
Panspermia is the hypothesis that the seeds of life are prevalent throughout the universe, and furthermore that life on Earth began by such seeds landing on Earth and propagating themselves. ...
The rare Earth hypothesis is a response to the Fermi paradox which explains why we might expect a planet such as Earth to be very rare. ...
Scientific skepticism or rational skepticism (UK spelling, scepticism) sometimes referred to as skeptical inquiry, is a scientific, or practical, epistemological position (or paradigm) in which one does not accept the veracity of claims unless they can be scientifically verified. ...
The SETI Institute has received limited telescope time at the Arecibo Observatory in Puerto Rico. ...
The Greys have landed! Alien mannequin at International UFO Museum & Research Center; Roswell, NM, USA Greys (also known as Zetas or Reticulians after the ζ Reticuli star system) are the type of intelligent extraterrestrial life that appears most commonly in modern conspiracy theories, particularly UFO conspiracy theories and other UFO-related...
External links
References - J. Deardorff, B. Haisch, B. Maccabee, H.E. Puthoff (2005). Inflation-Theory Implications for Extraterrestrial Visitation. Journal of the British Interplanetary Society 58: 43–50. (pdf file)
- Berger, Brian (2005). Exclusive: NASA Researchers Claim Evidence of Present Life on Mars. Posted Feb. 16, 2005.
- spacetoday.net (2005). NASA denies Mars life reports. Posted Feb 19, 2005.
- Michelson, Marcel (2005). European Scientists Believe in Life on Mars. Posted Feb 25, 2005.
- John C. Baird. 1987. The Inner Limits of Outer Space: A Psychologist Critiques Our Efforts to Communicate With Extraterrestrial Beings. Hanover: University Press of New England. ISBN 0-87451-406-1
- Donald Goldsmith. 1997. The Hunt for Life on Mars. New York: A Dutton Book. ISBN 0525943366
- Michael T. Lemnick. 1998. Other Worlds: The Search for Life in the Universe. New York: A Touchstone Book.
- Cliff Pickover. 2003 The Science of Aliens New York: Basic Books. ISBN 0-465-07315-8
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