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Encyclopedia > Extraterrestrial life
A 1967 Soviet Union 16 kopeks stamp, with a satellite from an imagined extraterrestrial civilization.
A 1967 Soviet Union 16 kopeks stamp, with a satellite from an imagined extraterrestrial civilization.

Extraterrestrial life is life originating outside of the Earth. It is the subject of astrobiology, and its existence remains hypothetical. There is no credible evidence of extraterrestrial life that has been widely accepted by the scientific community. There are several hypotheses regarding the origin of extraterrestrial life. One proposes that its emergence occurred independently, in different places in the universe. An alternative hypothesis is panspermia, which holds that life emerging in one location then spreads between habitable planets. These two hypotheses are not mutually exclusive. The study and theorization of extraterrestrial life is known as astrobiology, exobiology or xenobiology. Speculative forms of extraterrestrial life range from sapient beings to life at the scale of bacteria. Goblinoids (or greenskins) are a category of humanoid legendary creatures related to the goblin. ... Image File history File links Size of this preview: 429 × 599 pixel Image in higher resolution (1477 × 2061 pixel, file size: 802 KB, MIME type: image/jpeg) en: 1967 Soviet Union 16 kopeks stamp. ... Image File history File links Size of this preview: 429 × 599 pixel Image in higher resolution (1477 × 2061 pixel, file size: 802 KB, MIME type: image/jpeg) en: 1967 Soviet Union 16 kopeks stamp. ... ISO 4217 Code SUR User(s) Soviet Union Subunit 1/100 kopek (копейка) Symbol руб kopek (копейка) к Plural rublya (gen. ... This article is about life in general. ... This article is about Earth as a planet. ... The DNA structure might not be the only nucleic acid in the universe capable of supporting life[1] Astrobiology (from Greek: ἀστρο, astro, constellation; βίος, bios, life; and λόγος, logos, knowledge) is the interdisciplinary study of life in space, combining aspects of astronomy, biology and geology. ... This article does not cite any references or sources. ... Panspermia is a proven process (based on the principles of Biology, Microbiology, Physics, Chemistry, Astronomy, and assumption that life existed already in the universe) that explains how all life in the universe and/or solar system comes from a seed of life. ... A habitable planet is a world on which human beings can subsist without too much life-support equipment. ... In logic, two mutually exclusive (or mutual exclusive according to some sources) propositions are propositions that logically cannot both be true. ... Not to be confused with sentience. ... 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. ...


Suggested locations that might have once developed or continue to host life include the planets Venus[1] and Mars, natural satellites of Jupiter and Saturn (e.g. Europa,[2] Enceladus and Titan). Gliese 581 c and d, recently discovered to be near Earth-mass extrasolar planets apparently located in their star's habitable zone, and having the potential to have liquid water.[3] For other uses, see Venus (disambiguation). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Jupiter (disambiguation). ... This article is about the planet. ... Apparent magnitude: 5. ... Apparent magnitude 11. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ...

Contents

Possible basis of extraterrestrial life

Biochemistry

All life on Earth is made up of the principal elements, carbon, hydrogen, oxygen, nitrogen, and phosphorus; it also requires water as the solvent in which biochemical reactions take place. Sufficient quantities of carbon and the other major life-forming elements along with water may enable the formation of living organisms on other planets with a chemical make up and average temperature similar to Earth. Because Earth and other planets are made up of "star dust", relatively abundant chemical elements formed from stars which have ended their life as supernova, it is very probable that other planets may have been formed by elements of a similar composition as Earth. The combination of carbon and water in the chemical form of carbohydrates (e.g., sugar), can be a source of chemical energy on which life depends, and also provide structural elements for life (such as ribose, in the molecules DNA and RNA and cellulose in plants).Plants derive energy through the conversion of light energy into chemical energy via photosynthesis. Life requires carbon in both reduced (methane derivatives) and partially-oxidized (carbon oxides) states. It also requires nitrogen as a reduced ammonia derivative in all proteins, sulfur as a derivative of hydrogen sulfide in some necessary proteins, and phosphorus oxidized to phosphates in genetic material and in energy transfer. Adequate water as a solvent supplies adequate oxygen as constituents of biochemical substances. Wöhler observes the synthesis of urea. ... Alternative biochemistry is the speculative biochemistry of alien life forms that differ radically from those on Earth. ... This article is about the tv programme Life on Earth. ... For other uses, see Carbon (disambiguation). ... This article is about the chemistry of hydrogen. ... This article is about the chemical element and its most stable form, or dioxygen. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Solvent (disambiguation). ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ... For other uses, see Supernova (disambiguation). ... Lactose is a disaccharide found in milk. ... This article is about sugar as food and as an important and widely-traded commodity. ... Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For other uses, see RNA (disambiguation). ... Cellulose as polymer of β-D-glucose Cellulose in 3D Cellulose (C6H10O5)n is a polysaccharide of beta-glucose. ... For other uses, see Plant (disambiguation). ... Photosynthesis splits water to liberate O2 and fixes CO2 into sugar The leaf is the primary site of photosynthesis in plants. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... For other uses, see Ammonia (disambiguation). ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... This article is about the chemical element. ... Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... A phosphate, in inorganic chemistry, is a salt of phosphoric acid. ...


Pure water is useful because it has a neutral pH, due to its continued dissociation between hydroxide and hydronium ions. As a result, it can dissolve both positive metallic ions and negative non-metallic ions with equal ability. Furthermore, the fact that organic molecules can be either hydrophobic (repelled by water) or hydrophilic (soluble in water) creates the ability of organic compounds to orient themselves to form water-enclosing membranes. The fact that solid water (ice) is less dense than liquid water also means that ice floats, thereby preventing Earth's oceans from slowly freezing solid. Additionally, the Van der Waals forces between water molecules give it an ability to store energy with evaporation, which upon condensation is released. This helps moderate climate, cooling the tropics and warming the poles, helping to maintain a thermodynamic stability needed for life. For other uses, see PH (disambiguation). ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ... Sodium and chlorine bonding ionically to form sodium chloride. ... An ion is an atom or group of atoms with a net electric charge. ... ... 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. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... A biological membrane or biomembrane is an enclosing or separating tissue which acts as a barrier within or around a cell. ... In chemistry, the term van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ... Vaporization redirects here. ... For other uses, see Condensation (disambiguation). ...


Carbon is fundamental to terrestrial life for its immense flexibility in creating covalent chemical bonds with a variety of non-metallic elements, principally nitrogen, oxygen and hydrogen. Carbon dioxide and water together enable the storage of solar energy in sugars, such as glucose. The oxidation of glucose releases biochemical energy needed to fuel all other biochemical reactions. Covalent redirects here. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemical element and its most stable form, or dioxygen. ... This article is about the chemistry of hydrogen. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... This article deals with sugar as food and as an important, widely traded commodity; the word also has other uses; see Sugar (disambiguation) A sugar is a form of carbohydrate; the most commonly used sugar is a white crystalline solid, sucrose; used to alter the flavor and properties (mouthfeel, perservation... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... The most fundamental reactions in chemistry are the redox processes. ...


The ability to form organic acids (–COOH) and amine bases (–NH2) gives it the possibility of neutralisation dehydrating reactions to build long polymer peptides and catalytic proteins from monomer amino acids, and with phosphates to build not only DNA, the information storing molecule of inheritance, but also adenosine triphosphate (ATP) the principal energy "currency" of cellular life. An organic acid is an organic compound that is an acid. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... The best STM agency in the world ... Neutralization is a chemical reaction in which an acid and a base react and produce salt and water. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... It has been suggested that this article or section be merged into Catalysis. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer [1]. // Examples of monomers are hydrocarbons such as the alkene and arene homologous series. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... A phosphate, in inorganic chemistry, is a salt of phosphoric acid. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...


Due to their relative abundance and usefulness in sustaining life, many have hypothesized that life forms elsewhere in the universe would also utilize these basic materials. However, other elements and solvents could also provide a basis for life. Silicon is most often deemed to be the probable alternative to carbon. Silicon lifeforms are proposed to have a crystalline morphology, and are theorized to be able to exist in high temperatures, such as on planets which are very close to their star. Life forms based in ammonia rather than water have also been suggested, though this solution appears less optimal than water.[4] This article is about life in general. ... Not to be confused with Silicone. ... For other uses, see Ammonia (disambiguation). ...


Indeed, technically life is little more than any self-replicating reaction, which could arise in a great many conditions and with various ingredients, though carbon-oxygen within the liquid temperature range of water seems most conducive. Suggestions have even been made that self-replicating reactions of some sort could occur within the plasma of a star, though it would be highly unconventional. For other uses, see Plasma. ...


Several pre-conceived ideas about the characteristics of life outside of Earth have been questioned. For example, NASA scientists believe that the color of photosynthesizing pigments on extrasolar planets could be non-green.[5] For other uses, see NASA (disambiguation). ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ...


Evolution and morphology

In addition to the biochemical basis of extraterrestrial life, many have also considered evolution and morphology. Science fiction has often depicted extraterrestrial life with humanoid and/or reptilian forms. Aliens have often been depicted as having light green or grey skin, with a large head, as well as four limbs—i.e., this depiction is fundamentally humanoid. Other subjects such as felines and insects have also occurred in fictional representations of aliens. This article is about evolution in biology. ... Comparative anatomy is the study of similarities and differences in the anatomy of organisms. ... The term humanoid refers to any being whose body structure resembles that of a human. ... Orders  Crocodilia - Crocodilians scary crocodiles. ... Binomial name Felis catus Linnaeus, 1758 Synonyms Felis lybica invalid junior synonym The cat (or domestic cat, house cat) is a small carnivorous mammal. ... Orders Subclass Apterygota Symphypleona - globular springtails Subclass Archaeognatha (jumping bristletails) Subclass Dicondylia Monura - extinct Thysanura (common bristletails) Subclass Pterygota Diaphanopteroidea - extinct Palaeodictyoptera - extinct Megasecoptera - extinct Archodonata - extinct Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Blattodea (cockroaches) Mantodea (mantids) Isoptera (termites) Zoraptera Grylloblattodea Dermaptera (earwigs) Plecoptera (stoneflies) Orthoptera (grasshoppers, crickets...


A division has been suggested between universal and parochial (narrowly restricted) characteristics. Universals are features which have evolved independently more than once on Earth (and thus presumably are not difficult to develop) and are so intrinsically useful that species will inevitably tend towards them. These include flight, sight, photosynthesis and limbs, all of which have evolved several times here on Earth. There is a huge variety of eyes, for example, and many of these have radically different working schematics and different visual foci: the visual spectrum, infrared, polarity and echolocation. Parochials, however, are essentially arbitrary evolutionary forms. These often have little inherent utility (or at least have a function which can be equally served by dissimilar morphology) and probably will not be replicated. A classic example of a parochial is the curious and often fatal conjunction of the feeding and breathing passages found within many animals, although it is possible this conjunction allowed for the evolution of human speech.[citation needed] Evolving the Alien: The Science of Extraterrestrial Life (2002, second edition published as What Does a Martian Look Like? The Science of Extraterrestrial Life) is a book about xenobiology by biologist Jack Cohen and mathematician Ian Stewart. ... For other uses, see Flight (disambiguation). ... Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it as the perception known as sight or naked eye vision. ... Photosynthesis splits water to liberate O2 and fixes CO2 into sugar The leaf is the primary site of photosynthesis in plants. ... A limb (from the Old English lim) is a jointed, or prehensile (as octopus tentacles or new world monkey tails), appendage of the human or animal body; a large or main branch of a tree; a representative, branch or member of a group or organization. ... For other uses, see Eye (disambiguation). ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... For other uses, see Infrared (disambiguation). ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... Acoustic location is the art and science of using sound to determine the distance and direction of something. ... This article is about evolution in biology. ... Bold text This article does not cite any references or sources. ...


Attempting to define parochial features challenges many taken-for-granted notions about morphological necessity. Skeletons, which are essential to large terrestrial organisms according to the experts of the field of Gravitational biology, are almost assuredly to be replicated elsewhere in one form or another. Many also conjecture as to some type of egg laying amongst extraterrestrial creatures but mammalian mammary glands might be a singular case. Skeleton is also a winter sport: see skeleton (sport). ... Gravitational Biology is the study of the effects gravity has on living organisms. ... Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. ...


The assumption of radical diversity amongst putative extraterrestrials is by no means settled. While many exobiologists do stress that the enormously heterogeneous nature of Earth life foregrounds even greater variety in space, others point out that convergent evolution may dictate substantial similarities between Earth and off-Earth life. These two schools of thought are called "divergionism" and "convergionism", respectively.[6] In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ...


Beliefs in extraterrestrial life

Ancient and early modern ideas

See also: Cosmic pluralism

Belief in extraterrestrial life may have been present in ancient India, Egypt, Arabia, China, Babylon, Assyria and Sumer, although in these societies, cosmology was fundamentally supernatural and the notion of alien life is difficult to distinguish from that of gods, demons, and such. The first important Western thinkers to argue systematically for a universe full of other planets and, therefore, possible extraterrestrial life were the ancient Greek writer Thales and his student Anaximander in the 7th and 6th centuries B.C. 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, it favored the Earth and Earth-life (Aristotle denied there could be a plurality of worlds) and seemingly rendered extraterrestrial life philosophically untenable. Lucian in his novels described inhabitants of the Moon and other celestial bodies as humanoids, but with significant differences from humans. Cosmic pluralism or the plurality of worlds describes the belief in numerous other worlds beyond the Earth which harbour extraterrestrial life. ... The Arabian Peninsula The Arabian Peninsula is a mainly desert peninsula in Southwest Asia at the junction of Africa and Asia and an important part of the greater Middle East. ... For other uses, see Babylon (disambiguation). ... For other uses, see Assyria (disambiguation). ... Sumer (or Šumer; Sumerian: KI-EN-GIR [1]) was the earliest known civilization of the ancient Near East, located in lower Mesopotamia (modern Iraq), from the time of the earliest records in the mid 4th millennium BC until the rise of Babylonia in the late 3rd millennium BC. The term... Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) order + λογια (logia) discourse) is the study of the Universe in its totality, and by extension, humanitys place in it. ... For other uses, see Supernatural (disambiguation). ... For the Defense and Security Company, see Thales Group. ... This article is about the Pre-Socratic philosopher. ... 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. ... For other uses, see Aristotle (disambiguation). ... This article is about the geographer, mathematician and astronomer Ptolemy. ... For other uses, see Lucian (disambiguation). ...

Giordano Bruno, De l'Infinito, Universo e Mondi, 1584 Photo courtesy of P.C.
Giordano Bruno, De l'Infinito, Universo e Mondi, 1584 Photo courtesy of P.C.

Authors of Jewish sources also considered extraterrestrial life. The Talmud states that there are at least 18,000 other worlds, but provides little elaboration on the nature of the worlds and on whether they are physical or spiritual. Based on this, however, the 18th century exposition "Sefer HaB'rit" posits that extraterrestrial creatures exist but that they have no free will (and are thus equivalent to animal life). It adds that human beings should not expect creatures from another world to resemble earthly life, any more than sea creatures resemble land animals.[7][8] Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Giordano Bruno Giordano Bruno (1548, Nola – February 17, 1600, Rome) was an Italian philosopher, priest, cosmologist, and occultist. ... The word Jew ( Hebrew: יהודי) is used in a wide number of ways, but generally refers to a follower of the Jewish faith, a child of a Jewish mother, or someone of Jewish descent with a connection to Jewish culture or ethnicity and often a combination of these attributes. ... The Talmud (Hebrew: ) is a record of rabbinic discussions pertaining to Jewish law, ethics, customs, and history. ... Free-Will is a Japanese independent record label founded in 1986. ...


Hindu beliefs of endlessly repeated cycles of life have led to descriptions of multiple worlds in existence and their mutual contacts ( Sanskrit word Sampark (समपर्क) means 'contact' as in Mahasamparka (मह‌समपर्क) = the great contact). According to Hindu scriptures there are innumerable universes created by the Supreme Personality of Godhead to facilitate the fulfillment of the separated desires of innumerable living entities. However, the purpose of such creations is to bring back the deluded souls to correct understanding about the purpose of life. Apart from the innumerable universes which are material, there is also the existence of unlimited spiritual world, where the purified living entities live with perfect conception about life and ultimate reality. The life of these purified beings is centered around loving devotional services to Supreme Personality of Godhead. The spiritually aspiring saints and devotees as well as thoughtful men of material world have been getting guidance and help from these purified living entities of spiritual world from time immemorial. However, the relevance of such descriptions has to be evaluated in the context of a correct understanding of geography and science at those times. This article discusses the adherents of Hinduism. ... Sanskrit ( , for short ) is a classical language of India, a liturgical language of Hinduism, Buddhism, Sikhism, and Jainism, and one of the 23 official languages of India. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...


Within Islam, the statement of the Qur'an "All praise belongs to God, Lord of all the worlds" indicates multiple universal bodies and maybe even multiple universes that may indicate extraterrestrial and even extradimensional life. Surat Al-Jinn also mentioned a statement from a Jinn regarding the current status and ability of his group in the heavens. A more direct reference from Quran is presented by Mirza Tahir Ahmad as a proof that life on other planets may exist according to Quran. In his book, Revelation, Rationality, Knowledge & Truth, he quotes verse 42:29 "And among His Signs is the creation of the heavens and the earth, and of whatever living creatures (da'bbah) He has spread forth in both..."; according to this verse there is life in heavens. According to the same verse "And He has the power to gather them together (jam-'i-him) when He will so please"; indicates the bringing together the life on Earth and the life elsewhere in the universe. The verse does not specify the time or the place of this meeting but rather states that this event will most certainly come to pass whenever God so desires. It should be pointed out that the Arabic term Jam-i-him used to express the gathering event can imply either a physical encounter or a contact through communication.[9] For people named Islam, see Islam (name). ... The Qur’ān [1] (Arabic: , literally the recitation; also sometimes transliterated as Quran, Koran, or Al-Quran) is the central religious text of Islam. ... This article is about the term God in the context of monotheism and henotheism. ... Surat Al-Jinn (Arabic: سورة الجن ) (The Jinn or The Sprites) is the 72nd sura of the Quran with 28 ayat. ... For other uses, see Genie (disambiguation). ... Mirza Tahir Ahmad (* 18 December 1928 in Qadian, † 19 April 2003 in London) was Khalifatul Masih IV. Head of the Ahmadiyya Muslim Community. ... Revelation, Rationality, Knowledge & Truth is a book written by Mirza Tahir Ahmad, the head of the Ahmadiyya Muslim Community from 1982 to 2003. ...


When Christianity spread throughout the West, the Ptolemaic system became very widely accepted, and although the Church never issued any formal pronouncement on the question of alien life[10] at least tacitly the idea was aberrant. In 1277 the Bishop of Paris, Étienne Tempier, did overturn Aristotle on one point: God could have created more than one world (given His omnipotence) yet we know by revelation He only made one. Taking a further step and arguing that aliens actually existed remained rare. Notably, Cardinal Nicholas of Cusa speculated about aliens on the moon and sun. Topics in Christianity Movements · Denominations Ecumenism · Relation to other religions Preaching · Prayer Music · Liturgy · Calendar Symbols · Art · Criticism Christianity Portal This box:      Christianity is a monotheistic[1] religion centered on the life and teachings of Jesus of Nazareth as presented in the New Testament. ... The archbishop of Paris is one of twenty-three archbishops in France. ... Étienne (Stephen) Tempier (also known as Stephanus of Orleans) (d. ... Nicholas of Cusa Nicholas of Cusa (1401– August 11, 1464) was a German cardinal of the Roman Catholic Church, a philosopher, jurist, mathematician, and an astronomer. ... This article is about Earths moon. ... Sol redirects here. ...


There was a dramatic shift in thinking initiated by 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 towards the scientific mainstream. God's omnipotence, it could be argued, not only allowed for other worlds and other life, on some level it necessitated them. The best known early-modern proponent of such ideas was Giordano Bruno, who argued in the 16th century for an infinite universe in which every star is surrounded by its own solar system; he was eventually burned at the stake by the Catholic church for his heretical ideas. The Catholic church under John Paul II apologized for this. In the early 17th century the Czech astronomer Anton Maria Schyrleus of Rheita mused that "if Jupiter has…inhabitants…they must be larger and more beautiful than the inhabitants of the Earth, in proportion to the [characteristics] of the two spheres."[11] Dominican monk Tommaso Campanella wrote about a Solarian alien race in his Civitas Solis. This article does not cite any references or sources. ... In astronomy, heliocentrism is the theory that the Sun is at the center of the Universe and/or the Solar System. ... Giordano Bruno Giordano Bruno (1548, Nola – February 17, 1600, Rome) was an Italian philosopher, priest, cosmologist, and occultist. ... The name Catholic Church can mean a visible organization that refers to itself as Catholic, or the invisible Christian Church, viz. ... Schyrleus of Rheitas lunar map (1645) Anton (or Antonius) Maria Schyrleus (or Schyrle) of Rheita (1597-1660) (in Czech, Antonín Maria Sírek z Reity) was a Czech astronomer and optician. ... Tommaso Campanella (September 5, 1568–May 21, 1639), baptized Giovanni Domenico Campanella, was an Italian philosopher, theologian and poet. ... The City of the Sun (Italian: La città del Sole; Latin: Civitas Solis) by the Dominican philosopher Tommaso Campanella is one of the most important utopias. ...


Such comparisons also appeared in poetry of the era. In "The Creation: a Philosophical Poem in Seven Books" (1712) Sir Richard Blackmore observed: "We may pronounce each orb sustains a race / Of living things adapted to the place". The didactic poet Henry More took up the classical theme of the Greek Democritus in "Democritus Platonissans, or an Essay Upon the Infinity of Worlds" (1647). With the new relative viewpoint that the Copernican revolution had wrought, he suggested "our world's sunne / Becomes a starre elsewhere." Fontanelle's "Conversations on the Plurality of Worlds" (translated into English in 1686) offered similar excursions on the possibility of extraterrestrial life, expanding rather than denying the creative sphere of a Maker. Sir Richard Blackmore (c. ... Henry More. ... ‎ Democritus (Greek: ) was a pre-Socratic Greek materialist philosopher (born at Abdera in Thrace ca. ... For other uses of Fontenelle, see Fontenelle (disambiguation). ...


The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel, the discoverer of Uranus, was one of many 18th-19th century astronomers convinced that our Solar System, and perhaps others, would be well populated by alien life. Other luminaries of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment even the Sun and Moon were considered candidates for extraterrestrial inhabitants. For other persons named William Herschel, see William Herschel (disambiguation). ... For other uses, see Uranus (disambiguation). ... Kant redirects here. ... Benjamin Franklin (January 17 [O.S. January 6] 1706 – April 17, 1790) was one of the most well known Founding Fathers of the United States. ... The Age of Enlightenment (French: ; Italian: ; German: ; Spanish: ; Swedish: ; Polish: ; Portuguese: ) was an eighteenth-century movement in Western philosophy. ... Sol redirects here. ... This article is about Earths moon. ...


Extraterrestrials and the modern era

The Arecibo message is a digital message sent to globular star cluster M13, and is a well-known symbol of human attempts to contact extraterrestrials.
The Arecibo message is a digital message sent to globular star cluster M13, and is a well-known symbol of human attempts to contact extraterrestrials.

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 zenith for belief in extraterrestrials in the West. Many astronomers and other secular thinkers, at least some religious thinkers, 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 life. The other large moons of our system which have been visited appear similarly lifeless, though the interesting geothermic forces observed (Io's volcanism, Europa's ocean, Titan's thick atmosphere) have underscored how broad the range of potentially habitable environments may be. Although the hypothesis of a deliberate cosmic silence of advanced extraterrestrials is also a possibility,[12] the failure of the 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. Emboldened critics view the search for extraterrestrials as unscientific, despite the fact the SETI program is not the result of a continuous, dedicated search but instead utilizes what resources and manpower it can, when it can.[13] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Arecibo Observatory This is the message with color added to highlight its separate parts. ... Messier Object 13, the Great Globular Cluster in Hercules; one of the most prominent and best known globular clusters of the Northern celestial hemisphere. ... This article is about the period or event in history. ... For other uses, see Venus (disambiguation). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Atmosphere Surface pressure: trace Composition: 90% sulfur dioxide Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3,642 kilometers, is the fourth largest moon in the Solar System. ... Apparent magnitude: 5. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ... This article is about the search for extra-terrestrial intelligence. ... This article is about the search for extra-terrestrial intelligence. ...


Thus, the three decades preceding the turn of the second millennium saw a crossroads reached in beliefs in alien life. The prospect of ubiquitous, intelligent, space-faring civilizations in our solar system appears increasingly dubious to many scientists. Still, in the words of SETI's Frank Drake, "All we know for sure is that the sky is not littered with powerful microwave transmitters."[14] Drake has also noted that it is entirely possible advanced technology results in communication being carried out in some way other than conventional radio transmission. 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. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ...


In 2000, geologist and paleontologist Peter Ward and astrobiologist Donald Brownlee published a book entitled Rare Earth: Why Complex Life is Uncommon in the Universe.[15] In it, they discussed the Rare Earth hypothesis, in which they claim that Earth-like life is rare in the universe, while microbial life is common in the universe. The Geologist by Carl Spitzweg A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system (see planetary geology). ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Peter D. Ward is a paleontologist and professor of Biology and of Earth and Space Sciences at the University of Washington. ... The DNA structure might not be the only nucleic acid in the universe capable of supporting life[1] Astrobiology (from Greek: ἀστρο, astro, constellation; βίος, bios, life; and λόγος, logos, knowledge) is the interdisciplinary study of life in space, combining aspects of astronomy, biology and geology. ... The Rare Earth hypothesis is a hypothesis in planetary astronomy and astrobiology which argues that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. ... This article is about Earth as a planet. ... For other uses, see Universe (disambiguation). ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...


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 remain in debate.


Scientific search for extraterrestrial life

The scientific search for extraterrestrial life is being carried out in two different ways, directly and indirectly.


Direct search

The planned NASA Kepler mission for the search of extrasolar planets.

Scientists are directly searching for evidence of unicellular life within the solar system, carrying out studies on the surface of Mars and examining meteors that have fallen to Earth. A mission is also proposed to Europa, one of Jupiter's moons with a possible liquid water layer under its surface, which might contain life. Image source: http://www. ... Image source: http://www. ... For other uses, see NASA (disambiguation). ... The Kepler Mission is a space observatory being developed by NASA that will search for extrasolar planets and will only be the second space-based telescope particularly constructed for that task, the first one being COROT. For this purpose, it will observe the brightness of about 100,000 stars over... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ... This article is about the Solar System. ... Worlds second largest Meteorite in Culiacan, Mexico A meteorite is a relatively small extra-terrestrial body that reaches the Earths surface. ... Apparent magnitude: 5. ... 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.[16] 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. Recently, Circadian rhythms have been allegedly discovered in Viking data. The interpretation is controversial. Independently in 1996 structures resembling bacteria were reportedly discovered in a meteorite, ALH84001, thought to be formed of rock ejected from Mars. This report is also controversial and scientific debate continues (See Viking biological experiments). Viking mission profile. ... The Circadian rhythm is a name given to the internal body clock that regulates the (roughly) 24 hour cycle of biological processes in animals and plants. ... 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 ALH 84001 (Allan Hills 84001) is a meteorite found in Allan Hills, Antarctica in December 1984 by a team of US meteorite hunters from the ANSMET project. ... A Martian meteorite is a meteorite that has landed on Earth but is believed to have originated from Mars. ... The two Viking spacecraft each carried four biological experiments to the surface of Mars in the late 1970s. ...


In February 2005, NASA scientists reported that they had found strong evidence of present life on Mars.[17] 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.[18] For other uses, see NASA (disambiguation). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Aerial View of Moffett Field and NASA Ames Research Center. ... NASA photograph of Rio Tinto River. ...


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 conducted at the conference in which the European Space Agency presented its findings, 75 percent of the scientists in attendance reported to believe that life once existed on Mars; 25 percent reported a belief that life currently exists there.[19]


The Gaia hypothesis stipulates that any planet with a robust population of life will have an atmosphere that is not in chemical equilibrium, which is relatively easy to determine from a distance by spectroscopy. However, significant advances in the ability to find and resolve light from smaller rocky worlds near to their star are necessary before this can be used to analyze extrasolar planets For other uses, see Gaia. ... Animation of the dispersion of light as it travels through a triangular prism. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ...


Indirect search

Terrestrial Planet Finder - A planned Infrared interferometer for finding Earth-like extrasolar planets (as of 2007 , it has not received the funding from NASA it needs — that funding is going towards the Kepler mission).
Terrestrial Planet Finder - A planned Infrared interferometer for finding Earth-like extrasolar planets (as of 2007 , it has not received the funding from NASA it needs — that funding is going towards the Kepler mission).

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. A related suggestion is that aliens might broadcast pulsed and continuous laser signals in the optical as well as infrared spectrum;[20] laser signals have the advantage of not "smearing" in the interstellar medium and may prove more conducive to communication between the stars. And while other communication techniques including laser transmission and interstellar spaceflight have been discussed seriously and may not be infeasible, the measure of effectiveness is the amount of information communicated per unit cost, resulting with the radio as method of choice. Image File history File links Download high resolution version (1900x1425, 138 KB) Terrestrial Planet Finder - Infrared interferometer concept source: http://photojournal. ... Image File history File links Download high resolution version (1900x1425, 138 KB) Terrestrial Planet Finder - Infrared interferometer concept source: http://photojournal. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ... The Kepler Mission is a space observatory being developed by NASA that will search for extrasolar planets and will only be the second space-based telescope particularly constructed for that task, the first one being COROT. For this purpose, it will observe the brightness of about 100,000 stars over... This article is about the search for extra-terrestrial intelligence. ... For other uses, see Laser (disambiguation). ...


Extrasolar planets

Astronomers also search for extrasolar planets that they believe would be conducive to life, such as Gliese 581 c and OGLE-2005-BLG-390Lb, which have been found to have Earth-like qualities.[21][22] 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): An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... OGLE-2005-BLG-390Lb is a super-Earth extrasolar planet orbiting the star OGLE-2005-BLG-390L, which is situated 21,500 ± 3,300 light years away from Earth, near the center of the Milky Way galaxy. ... Atomic absorption spectroscopy In analytical chemistry, Atomic absorption spectroscopy is a technique for determining the concentration of a particular metal element in a sample. ... This article is about the chemical element and its most stable form, or dioxygen. ...

Artist's Impression of Gliese 581 c, the first extrasolar planet discovered within its star's habitable zone.
Artist's Impression of Gliese 581 c, the first extrasolar planet discovered within its star's habitable zone.
  • Darwin is an ESA mission designed to find Earth-like planets, and analyse their atmosphere.
  • The COROT mission, initiated by the French Space Agency, was launched in 2006 and is currently looking for extrasolar planets -- it is the first of its kind
  • The Terrestrial Planet Finder was supposed to be launched by NASA, but as of 2007 , budget cuts have caused it to be delayed indefinitely
  • The Kepler Mission, largely replacing the Terrestrial Planet Finder, to be launched in November 2008

It has been argued that Alpha Centauri, the closest star system to Earth, may contain planets which could be capable of sustaining life.[23] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. ... For a French painter, see Jean-Baptiste-Camille Corot. ... The Centre National dÉtudes Spatiales is the French government space agency (administratively, a public establishment of industrial and commercial character). Its headquarters are located in central Paris. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ... For other uses, see NASA (disambiguation). ... The Kepler Mission is a space observatory being developed by NASA that will search for extrasolar planets and will only be the second space-based telescope particularly constructed for that task, the first one being COROT. For this purpose, it will observe the brightness of about 100,000 stars over... Alpha Centauri (α Cen / α Centauri, also known as Rigil Kentaurus), is the brightest star system in the southern constellation of Centaurus. ...


On April 24, 2007, scientists at the European Southern Observatory in La Silla, Chile said they had found the first Earth-like planet. The planet, known as Gliese 581 c, orbits within the habitable zone of its star Gliese 581, a red dwarf star which is a scant 20.5 light years (194 trillion km) from Earth. It was initially thought that this planet could contain liquid water. However, recent computer simulations of the climate on Gliese 581c by Werner Von Bloh and his team at Germany's Institute for Climate Impact Research suggest carbon dioxide and methane in the atmosphere would create a runaway greenhouse effect. This would warm the planet well above the boiling point of water (100 degrees Celsius/212 degrees Fahrenheit), thus dimming the hopes of finding life. As a result of greenhouse models, scientists are now turning their attention to Gliese 581 d, which lies just outside of the star's traditional habitable zone.[24] is the 114th day of the year (115th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Gliese 581 (IPA: ) is an M2. ... This article is about the British sitcom. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...


On May 29, 2007, the Associated Press released a report stating that scientists have identified twenty-eight exo-solar planetary bodies. One of these newly discovered planets is said to have many similarities with Neptune.[25] is the 149th day of the year (150th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...


Drake equation

Main article: Drake equation

In 1961, University of California, Santa Cruz astronomer and astrophysicist Dr. Frank Drake devised the Drake equation, which mathematically simplifies the rate of formation of suitable stars, the fraction of those stars which contain planets, the number of Earth-like worlds per planetary system, the fraction of planets where intelligent life develops, and the fraction of possible communicative planets, and the "lifetime" of possible communicative civilizations which scientifically stated there are an estimated 10,000 planets containing intelligent life with the possible capability of communicating with Earth in the Milky Way galaxy.[26] The Drake equation (also sometimes called The Green Bank equation, The Green Bank Formula or often erroneously labeled The Sagan equation) is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence (SETI). ... “UCSC” redirects here. ... Galileo is often referred to as the Father of Modern Astronomy. ... Professor Frank Drake Frank Drake (born May 28, 1930, Chicago, Illinois) is an American astronomer and astrophysicist. ... The Drake equation (also sometimes called The Green Bank equation, The Green Bank Formula or often erroneously labeled The Sagan equation) is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence (SETI). ... This article is about Earth as a planet. ... This article is about Earth as a planet. ... For other uses, see Milky Way (disambiguation). ...


Extraterrestrial life in the Solar System

This planetary habitability chart shows where life might exist on extrasolar planets based on our own Solar System and life on Earth.
This planetary habitability chart shows where life might exist on extrasolar planets based on our own Solar System and life on Earth.
Europa, due to the ocean under its icy crust, might host some form of microbial life.
Europa, due to the ocean under its icy crust, might host some form of microbial life.[27][2]

Many bodies in the Solar System have been suggested as being capable of containing conventional organic life. The most commonly suggested ones are listed below; of these, five of the nine are moons, and are thought to have large bodies of underground liquid (streams), where life may have evolved in a similar fashion to deep sea vents. Image File history File links Habitable_zone-en. ... Image File history File links Habitable_zone-en. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ... This article is about the Solar System. ... This article is about Earth as a planet. ... Image File history File links Download high resolution version (2666x2000, 528 KB) Interior of Europa original description: Cutaway view of the possible internal structure of Europa The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft. ... Image File history File links Download high resolution version (2666x2000, 528 KB) Interior of Europa original description: Cutaway view of the possible internal structure of Europa The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft. ... Apparent magnitude: 5. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...

  • Mars - Life on Mars has been long speculated. Liquid water is widely thought to have existed on Mars in the past and there may still be liquid water beneath the surface. Methane was found in the atmosphere of Mars. Recent photographs from Mars Global Surveyor show evidence of recent (within 10 years) flows of a liquid on the Red Planet's frigid surface.[28]
  • Europa - Europa may contain liquid water beneath its 100-mile (160 km) thick ice layer. Vents on the bottom of the ocean warm the ice so that 60 miles (97 km) of liquid could exist beneath the ice layer, perhaps capable of supporting microbes and simple plants.[2]
  • Jupiter - Possible supporter of floating animals, as hypothesized by Carl Sagan for gas giants in general. This point of view is somewhat controversial because these creatures would not be water-based, but ammonia-based.[29]
  • Ganymede - Possible underground ocean (see Europa).
  • Callisto - Possible underground ocean (see Europa).
  • Saturn - Possible floating creatures (see Jupiter).
  • Enceladus - Geothermal activity, watervapour. Possible underice oceans heated by tidal effects.
  • Titan (Saturn's largest moon) - The only known moon with a significant atmosphere was recently visited by the Huygens probe. Latest discoveries indicate that there is no global or widespread ocean, but small and/or seasonal liquid hydrocarbon lakes are present on the surface (the first liquid lakes discovered outside of Earth).[30][31][32]
  • Venus - Recently, scientists have speculated the existence of microbes in the stable cloud layers 50 km above the surface, evidenced by hospitable climates and chemical disequilibrium.[33]

Numerous other bodies have been suggested as potential hosts for microbial life. Fred Hoyle has proposed that life might exist on comets, as some Earth microbes managed to survive on a lunar probe for many years. However, it is considered highly unlikely that complex multicellular organisms of the conventional chemistry of terrestrial life (animals, plants) could exist under these living conditions. Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Life on Mars (disambiguation). ... Methane is a chemical compound with the molecular formula . ... The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... Apparent magnitude: 5. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... u fuck in ua ... For other uses, see Jupiter (disambiguation). ... Atmospheric beasts (also sky beasts or sky critters) are organisms which could hypothetically exist off of the surface of Earth or other planets with an atmosphere. ... Insert non-formatted text here Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer and astrobiologist and a highly successful popularizer of astronomy, astrophysics, and other natural sciences. ... For other uses, see Ammonia (disambiguation). ... This article is about the natural satellite of Jupiter. ... Apparent magnitude: 5. ... There is also an asteroid named 204 Kallisto. ... Apparent magnitude: 5. ... This article is about the planet. ... For other uses, see Jupiter (disambiguation). ... Apparent magnitude 11. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ... This article is about the planet. ... The Huygens probe, supplied by the European Space Agency (ESA) and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry probe carried to Saturns moon Titan as part of the Cassini-Huygens mission. ... Look up Hydrocarbon in Wiktionary, the free dictionary. ... For other uses, see Lake (disambiguation). ... For other uses, see Venus (disambiguation). ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Sir Frederick Hoyle, FRS, (born on June 24, 1915 in Gilstead, Yorkshire, England – August 20, 2001 in Bournemouth, England)[1] was a British astronomer, he was educated at Bingley Grammar School and notable for a number of his theories that run counter to current astronomical opinion, and a writer of...


See also

Events and objects
Searches for extraterrestrial life
Subjects
Theories

Meteorite fragment ALH84001 ALH 84001 (Allan Hills 84001) is a meteorite found in Allan Hills, Antarctica in December 1984 by a team of US meteorite hunters from the ANSMET project. ... A Martian meteorite is a meteorite, that has landed on Earth but is believed to have originated from Mars. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ... Red rain collected in buckets From 25 July to 23 September 2001, red rain sporadically descended upon the southern Indian state of Kerala. ... The WOW! Signal Credit: The Ohio State University Radio Observatory and the North American AstroPhysical Observatory (NAAPO). ... CETI (Communication with Extraterrestrial Intelligence, or METI, Messaging to Extraterrestrial Intelligence) is a branch of SETI research that focuses on composing and deciphering messages that could theoretically be understood by another technological civilization. ... Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. ... This article is about the European Space Agency. ... This article is about the search for extra-terrestrial intelligence. ... The Allen Telescope Array (ATA), formerly known as the One Hectare Telescope (1hT), is a joint effort by the SETI Institute and the Radio Astronomy Laboratory at the University of California, Berkeley to construct a radio interferometer that is dedicated to astronomical and simultaneous search for extra-terrestrial intelligence observations. ... The DNA structure might not be the only nucleic acid in the universe capable of supporting life[1] Astrobiology (from Greek: ἀστρο, astro, constellation; βίος, bios, life; and λόγος, logos, knowledge) is the interdisciplinary study of life in space, combining aspects of astronomy, biology and geology. ... Cryptozoology is the study of rumored or mythological animals that are presumed to exist, but for which conclusive proof does not yet exist; or are generally considered extinct, but occasionally reported. ... 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. ... This article does not cite any references or sources. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ... The Rare Earth hypothesis is a hypothesis in planetary astronomy and astrobiology which argues that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Extraterrestrial liquid water, the presence of water in its liquid state, is a subject of wide interest because it is a commonly suggested prerequisite for the emergence of extraterrestrial life. ... Zecharia Sitchins photograph from The 12th Planet Zecharia Sitchin (born 1922)[1] is a best-selling author of books promoting the ancient astronaut theory for human origins. ... Aurelia and Blue Moon are two fictional/hypothetical satellites on which extraterrestrial life could evolve. ... Back-contamination is the informal but widely-employed name for the introduction of microbial extraterrestrial organisms into Earths biosphere. ... The Drake equation (also sometimes called The Green Bank equation, The Green Bank Formula or often erroneously labeled The Sagan equation) is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence (SETI). ... For the song by Muse, see Black Holes and Revelations. ... A graphical representation of the Arecibo message - Humanitys first attempt to use radio waves to communicate its existence to alien civilizations The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for or contact with... Panspermia is a proven process (based on the principles of Biology, Microbiology, Physics, Chemistry, Astronomy, and assumption that life existed already in the universe) that explains how all life in the universe and/or solar system comes from a seed of life. ... The Sentience Quotient concept was invented by Robert A. Freitas Jr. ... Kardashev scale projections ranging from 1900 to 2100. ...

References

  1. ^ Venus clouds 'might harbour life'. BBC News (2004-05-25). Retrieved on 2007-12-05.
  2. ^ a b c http://www.planetary.org/programs/projects/explore_europa/update_12142005.html"
  3. ^ The Habitability of Super-Earths in Gliese 581. Retrieved on 2007-12-01.
  4. ^ Ammonia based life. daviddarling.info.
  5. ^ NASA - NASA Predicts Non-Green Plants on Other Planets
  6. ^ Variety of extraterrestrial life. daviddarling.info.
  7. ^ Star Struck, a letter to a Rabbi. ohr.edu.
  8. ^ Kaplan, Rabbi Aryeh. Extraterrestrial life. torah.org.
  9. ^ [1]Revelation, Rationality, Knowledge & Truth, by Mirza Tahir Ahmad. Chapter; The Quran and Extraterrestrial Life
  10. ^ Wiker, Benjamin D.. Christianity and the Search for Extraterrestrial Life. crisismagazine.com.
  11. ^ Rheita.htm. cosmovisions.com.
  12. ^ An intelligent design : Controlled hominization in cosmic apartheid
  13. ^ Crichton, Michael (January 17, 2003). Aliens Cause Global Warming. crichton-official.com.
  14. ^ SETI: Search For Extra-Terrestial Intelligence
  15. ^ Amazon.com: Rare Earth: Why Complex Life is Uncommon in the Universe: Books: Peter Ward,Donald Brownlee
  16. ^ Spherix: Makers of Naturlose (tagatose), a natural, low-calorie sugar made from whey that may be useful as a treatment for Type 2 diabetes
  17. ^ Berger, Brian. "Exclusive: NASA Researchers Claim Evidence of Present Life on Mars", 2005. 
  18. ^ "NASA denies Mars life reports", spacetoday.net, 2005. 
  19. ^ Spotts, Peter N.. "Sea boosts hope of finding signs of life on Mars", The Christian Science Monitor, 2005-02-28. Retrieved on 2006-12-18. 
  20. ^ The Search for Extraterrestrial Intelligence (SETI) in the Optical Spectrum. The Columbus Optical SETI Observatory.
  21. ^ "http://planet.iap.fr/OB05390.news.html" . 
  22. ^ SPACE.com - Major Discovery: New Planet Could Harbor Water and Life
  23. ^ 1997AJ 113.1445W Page 1445
  24. ^ Hopes dim for life on distant planet - USATODAY.com
  25. ^ BBC NEWS | Science/Nature | Planet hunters spy distant haul
  26. ^ Boyd, Padi. The Drake Equation. Imagine the Universe. NASA. Retrieved on 2008-02-05. “Frank Drake's own current estimate puts the number of communicating civilizations in the galaxy at 10,000”
  27. ^ Possibility of Life on Europa
  28. ^ BBC NEWS | Science/Nature | Water 'flowed recently' on Mars
  29. ^ Jupiter, life on
  30. ^ SPACE.com - Scientists Reconsider Habitability of Saturn's Moon
  31. ^ SPACE.com - Lakes Found on Saturn's Moon Titan
  32. ^ Lakes on Titan, Full-Res: PIA08630 (July 24, 2006).
  33. ^ Venusian Cloud Colonies :: Astrobiology Magazine - earth science - evolution distribution Origin of life universe - life beyond :: Astrobiology is study of earth science evolution distribution Origin of life in universe terrestrial

Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 145th day of the year (146th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 339th day of the year (340th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 335th day of the year (336th in leap years) in the Gregorian calendar. ... is the 17th day of the year in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 59th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 352nd day of the year (353rd in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 36th day of the year in the Gregorian calendar. ...

Further reading

  • Baird, John C. (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. 
  • Cohen, Jack and Ian Stewart (2002). Evolving the Alien: The Science of Extraterrestrial Life. Ebury Press. ISBN 0-09-187927-2. 
  • Crowe, Michael J. (1986). The Extraterrestrial Life Debate, 1750--1900. Cambridge. 
  • Dick, Steven J. (1984). Plurality of Worlds: The Extraterrestrial Life Debate from Democratis to Kant. Cambridge. 
  • Dick, Steven J. (1996). The Biological Universe: The Twentieth Century Extraterrestrial Life Debate and the Limits of Science. Cambridge. 
  • Dick, Steven J. (2001). Life on Other Worlds: The 20th Century Extraterrestrial Life Debate. Cambridge. 
  • Dick, Steven J. and James E. Strick (2004). The Living Universe: Nasa And the Development of Astrobiology. Rutgers. 
  • Goldsmith, Donald (1997). The Hunt for Life on Mars. New York: A Dutton Book. ISBN 0-525-94336-6. 
  • Grinspoon, David (2003). Lonely Planets: The Natural Philosophy of Alien Life. HarperCollins. ISBN 0-06-018540-6. 
  • Lemnick, Michael T. (1998). Other Worlds: The Search for Life in the Universe. New York: A Touchstone Book. 
  • Pickover, Cliff (2003). The Science of Aliens. New York: Basic Books. ISBN 0-465-07315-8. 
  • Roth, Christopher F. (2005) "Ufology as Anthropology: Race, Extraterrestrials, and the Occult." In E.T. Culture: Anthropology in Outerspaces, ed. by Debbora Battaglia. Durham, N.C.: Duke University Press.
  • Sagan, Carl and I.S. Shklovskii (1966). Intelligent Life in the Universe. Random House. 
  • Sagan, Carl (1973). Communication with Extraterrestrial Intelligence. MIT Press. 

Jack Cohen is a reproductive biologist at the University of Warwick, England. ... Ian Stewart, FRS (b. ... Evolving the Alien: The Science of Extraterrestrial Life (2002, second edition published as What Does a Martian Look Like? The Science of Extraterrestrial Life) is a book about xenobiology by biologist Jack Cohen and mathematician Ian Stewart. ... Clifford A. Pickover is a writer in the fields of science, mathematics, and science fiction. ... // The Science of Aliens is a touring exhibition that launched at the Science Museum (London) in October 2005. ... Insert non-formatted text here Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer and astrobiologist and a highly successful popularizer of astronomy, astrophysics, and other natural sciences. ... Iosif Samuilovich Shklovsky (Ио́сиф Самуи́лович Шкло́вский) (July 1, 1916 – March 3, 1985) was a Russian astronomer and astrophysicist. ... CETI (Communication with Extraterrestrial Intelligence, or METI, Messaging to Extraterrestrial Intelligence) is a branch of SETI research that focuses on composing and deciphering messages that could theoretically be understood by another technological civilization. ...

External links

  • 'The UFO Disclosure Project'A Demand for Congressional hearings on UFOs and related technology "Video"
  • 'The truth is out there'UFOs Filmed 26 July 2007.
  • 'Is There Anybody Out There?' Freeview video by the Vega Science Trust and the BBC/OU.
  • PBS: Life Beyond Earth a film by Timothy Ferris
  • PBS: Exploring Space - The Quest for Life by Scott Pearson
  • ufoskeptic.org by Bernard Haisch
  • Xenopsychology by Robert A. Freitas Jr.
  • "What Aliens Might Look Like" from National Geographic
  • Sylvia Engdahl, "Early Space Poetry" Part I: Didactic and other poetry concerning other inhabited worlds, well-known and obscure poets, 17th-18th centuries. "Part II": 19th century
  • Top stars picked in alien search
  • "Snaiad", a realistic world-design exercise by Nemo Ramjet
is the 207th day of the year (208th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... The National Geographic Society was founded in the USA on January 27, 1888, by 33 men interested in organizing a society for the increase and diffusion of geographical knowledge. ... This article is about the physical universe. ... This article is about Earth as a planet. ... Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... Earth cutaway from core to exosphere. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... Geological time scale. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... For the geological process, see Weathering or Erosion. ... Air redirects here. ... This article is about life in general. ... For other uses, see Biosphere (disambiguation). ... For the definition, see Life. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... For other uses, see Plant (disambiguation). ... For the fictional character, see Fungus the Bogeyman. ... Fauna is a collective term for animal life of any particular region or time. ... For other uses, see Animal (disambiguation). ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: Βιολογία - βίος, bio, life; and λόγος, logos, speech lit. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... For other uses, see Wilderness (disambiguation). ... For the journal, see Ecology (journal). ... For other uses, see Ecological Systems Theory. ... For other uses, see Universe (disambiguation). ... This article is about matter in physics and chemistry. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ...

  Results from FactBites:
 
Extraterrestrial life & UFOs (0 words)
The existence of life on Earth does not imply anything for the probability of life existing elsewhere, because if life did not exist on Earth, we would not exist to observe it (this observer effect is known as the anthropic principle).
But if life arose independently on another body in our solar system, and planetary systems are the rule, not the exception, then life must be abundant in the universe.
But there was another good reason to keep the evidence for extraterrestrial life a secret: the chance for the American military to gain a technological edge over other nations by reverse-engineering and duplicating the alien technology.
KryssTal : Extraterrestrial Life (3156 words)
extraterrestrial life is because there is strong evidence that all life on this planet has a common origin.
Life may exist on Mars in some primitive or suspended form in areas where there is evidence of past water.
Life would then be a normal part of the evolution of the Universe rather than a special event confined to Earth.
  More results at FactBites »

 
 

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