1.
Latin
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Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
2.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
3.
Liquid
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A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume independent of pressure. As such, it is one of the four states of matter. A liquid is made up of tiny vibrating particles of matter, such as atoms, water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container, most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, a distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in form as interstellar clouds or in plasma form within stars. Liquid is one of the four states of matter, with the others being solid, gas. Unlike a solid, the molecules in a liquid have a greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, a liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, if liquid is placed in a bag, it can be squeezed into any shape. These properties make a suitable for applications such as hydraulics. Liquid particles are bound firmly but not rigidly and they are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its point, the cohesive forces that bind the molecules closely together break. If the temperature is decreased, the distances between the molecules become smaller, only two elements are liquid at standard conditions for temperature and pressure, mercury and bromine. Four more elements have melting points slightly above room temperature, francium, caesium, gallium and rubidium, metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams
4.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
5.
Extraterrestrial life
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Extraterrestrial life, also called alien life, is life that does not originate from Earth. These hypothetical life forms may range from simple single-celled organisms to beings with civilizations far more advanced than humanity, although many scientists expect extraterrestrial life to exist in some form, there is no evidence for its existence to date. The Drake equation speculates about the existence of intelligent life elsewhere in the universe, the science of extraterrestrial life in all its forms is known as exobiology. The science of astrobiology considers life on Earth as well, in 2015, remains of biotic life were found in 4.1 billion-year-old rocks in Western Australia, when the young Earth was about 400 million years old. According to one of the researchers, If life arose relatively quickly on Earth and it has also played a major role in works of science fiction. Over the years, science fiction works have increased the publics interest in the possibility of extraterrestrial life, some encourage aggressive methods to try for contact with intelligent extraterrestrial life, whereas others argue that it might be dangerous to actively call attention to Earth. Alien life, such as microorganisms, has been hypothesized to exist in the Solar System and this hypothesis relies on the vast size and consistent physical laws of the observable universe. The chemistry of life may have begun shortly after the Big Bang,13.8 billion years ago, Life may have emerged independently at many places throughout the universe. Alternatively, life may have formed less frequently, then spread—by meteoroids, in any case, complex organic molecules may have formed in the protoplanetary disk of dust grains surrounding the Sun before the formation of Earth. According to these studies, this process may occur outside Earth on several planets and moons of the Solar System, since the 1950s, scientists have argued the idea that habitable zones around stars are the most likely places to find life. The nearest such planet may be 12 light-years away, according to the scientists, astrobiologists have also considered a follow the energy view of potential habitats. Life on Earth requires water as its solvent in which biochemical reactions take place, More generally, life based on ammonia has been suggested, though this solvent appears less suitable than water. It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbon, about 29 chemical elements play an active positive role in living organisms on Earth. About 95% of this matter is built upon only six elements, carbon, hydrogen, nitrogen, oxygen, phosphorus. These six elements form the building blocks of virtually all life on Earth. The unique characteristics of carbon make it unlikely that it could be replaced, even on another planet, the carbon atom has the unique ability to make four strong chemical bonds with other atoms, including other carbon atoms. These covalent bonds have a direction in space, so that carbon atoms can form the skeletons of complex 3-dimensional structures with definite architectures such as nucleic acids, carbon forms more compounds than all other elements combined. The great versatility of the atom makes it the element most likely to provide the bases—even exotic ones—for the chemical composition of life on other planets
6.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
7.
Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
8.
Life
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Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. The criteria can at times be ambiguous and may or may not define viruses, viroids, biology is the primary science concerned with the study of life, although many other sciences are involved. The definition of life is controversial, the current definition is that organisms maintain homeostasis, are composed of cells, undergo metabolism, can grow, adapt to their environment, respond to stimuli, and reproduce. However, many other definitions have been proposed, and there are some borderline cases. Modern definitions are more complex, with input from a diversity of scientific disciplines, biophysicists have proposed many definitions based on chemical systems, there are also some living systems theories, such as the Gaia hypothesis, the idea that the Earth itself is alive. Another theory is that life is the property of systems, and yet another is elaborated in complex systems biology. Abiogenesis describes the process of life arising from non-living matter. Properties common to all organisms include the need for certain chemical elements to sustain biochemical functions. Life on Earth first appeared as early as 4.28 billion years ago, soon after ocean formation 4.41 billion years ago, Earths current life may have descended from an RNA world, although RNA-based life may not have been the first. The mechanism by which began on Earth is unknown, though many hypotheses have been formulated and are often based on the Miller–Urey experiment. The earliest known forms are microfossils of bacteria. In July 2016, scientists reported identifying a set of 355 genes believed to be present in the last universal ancestor of all living organisms. Since its primordial beginnings, life on Earth has changed its environment on a time scale. To survive in most ecosystems, life must often adapt to a range of conditions. Some microorganisms, called extremophiles, thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth, Aristotle was the first person to classify organisms. Later, Carl Linnaeus introduced his system of nomenclature for the classification of species. Eventually new groups and categories of life were discovered, such as cells and microorganisms, cells are sometimes considered the smallest units and building blocks of life. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many such as proteins
9.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
10.
Circumstellar habitable zone
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The bounds of the CHZ are based on Earths position in the Solar System and the amount of radiant energy it receives from the Sun. Since the concept was first presented in 1953, many stars have been confirmed to possess a CHZ planet, most such planets, being super-Earths or gas giants, are more massive than Earth, because such planets are easier to detect. 11 billion of these may be orbiting Sun-like stars, proxima Centauri b, located about 4.2 light-years from Earth in the constellation of Centaurus, is the nearest known exoplanet, and is orbiting in the habitable zone of its star. The CHZ is also of particular interest to the field of habitability of natural satellites. In subsequent decades, the CHZ concept began to be challenged as a criterion for life. Since the discovery of evidence for liquid water, substantial quantities of it are now thought to occur outside the circumstellar habitable zone. Sustained by other sources, such as tidal heating or radioactive decay or pressurized by non-atmospheric means, liquid water may be found even on rogue planets. In addition, other circumstellar zones, where non-water solvents favorable to life based on alternative biochemistries could exist in liquid form at the surface, have been proposed. In the same year, Harlow Shapley wrote Liquid Water Belt, both works stressed the importance of liquid water to life. The theory of habitable zones was further developed in 1964 by Stephen H, at the same time, science-fiction author Isaac Asimov introduced the concept of a circumstellar habitable zone to the general public through his various explorations of space colonization. The term Goldilocks zone emerged in the 1970s, referencing specifically a region around a star whose temperature is just right for water to be present in the liquid phase. In 1993, astronomer James Kasting introduced the term circumstellar habitable zone to refer more precisely to the then known as the habitable zone. Whether a body is in the habitable zone of its host star is dependent on the radius of the planets orbit, the mass of the body itself. The outer edge of the HZ is the distance from the star where adding more carbon dioxide to the atmosphere fails to keep the surface of the planet above the freezing point. Estimates for the zone within the Solar System range from 0.5 to 3.0 astronomical units. Numerous planetary mass objects orbit within, or close to, this range, however their atmospheric conditions vary substantially. The entire orbits of the Moon, Mars, and numerous asteroids also lie within various estimates of the habitable zone, only at Mars lowest elevations is atmospheric pressure and temperature sufficient for water to, if present, exist in liquid form for short periods. At Hellas Basin, for example, atmospheric pressures can reach 1,115 Pa, despite indirect evidence in the form of seasonal flows on warm Martian slopes, no confirmation has been made of the presence of liquid water there
11.
Origin of water on Earth
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The origin of water on Earth, or the reason that there is clearly more liquid water on Earth than on the other rocky planets of the Solar System, is not completely understood. There exist numerous more or less mutually compatible hypotheses as to how water may have accumulated on Earths surface over the past 4.5 billion years in sufficient quantity to form oceans. Comets, trans-Neptunian objects or water-rich meteoroids from the reaches of the asteroid belt colliding with Earth may have brought water to the worlds oceans. Large enough Planetesimals were heated by the decay of aluminium isotope and this could cause water to rise to the surface. What is however unclear is whether these comets are representative of those from the Kuiper Belt, the water in carbon-rich chondrites point to a similar D/H ratio as oceanic water. Nevertheless, mechanisms have been proposed to suggest that the D/H-ratio of oceanic water may have increased significantly throughout Earths history, such a proposal is consistent with the possibility that a significant amount of the water on Earth was already present during the planets early evolution. Recent measurements of the composition of Moon rocks suggest that Earth was born with its water already present. Investigating lunar samples carried to Earth by the Apollo 15 and 17 missions found a ratio that matched the isotopic ratio in carbonaceous chondrites. The ratio is similar to that found in water on Earth. The findings suggest a common source of water for both objects and this supports a theory that Jupiter temporarily migrated into the inner Solar System, destabilizing the orbits of water-rich carbonaceous chondrites. As a result, some of the bodies could have fallen inwards and become part of the raw material for making Earth, the discovery of water vapor out-gassing from Ceres provides related information on water-ice content of the asteroid belt. Gradual leakage of stored in hydrate minerals of Earths rocks could have formed a portion of its water. Water may also have come from volcanism, water vapor in the atmosphere that originated in volcanic eruptions may have condensed to form rain, a sizeable quantity of water would have been in the material that formed Earth. Water molecules would have escaped Earths gravity more easily when it was less massive during its formation, part of the young planet is theorized to have been disrupted by the impact which created the Moon, which should have caused melting of one or two large areas. Present composition does not match complete melting and it is hard to melt, however, a fair fraction of material should have been vaporized by this impact, creating a rock-vapor atmosphere around the young planet. The rock-vapor would have condensed within two years, leaving behind hot volatiles which probably resulted in a heavy carbon dioxide atmosphere with hydrogen. Liquid water oceans existed despite the temperature of 230°C because of the atmospheric pressure of the heavy CO2 atmosphere. As cooling continued, subduction and dissolving in ocean water removed most CO2 from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared
12.
Absorption spectroscopy
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Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i. e. photons, from the radiating field, the intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum, Infrared and ultraviolet-visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is employed in studies of molecular and atomic physics, astronomical spectroscopy. There are a range of experimental approaches for measuring absorption spectra. The most common arrangement is to direct a beam of radiation at a sample. The transmitted energy can be used to calculate the absorption, the source, sample arrangement and detection technique vary significantly depending on the frequency range and the purpose of the experiment. A materials absorption spectrum is the fraction of incident radiation absorbed by the material over a range of frequencies, the absorption spectrum is primarily determined by the atomic and molecular composition of the material. Radiation is more likely to be absorbed at frequencies that match the difference between two quantum mechanical states of the molecules. The absorption that occurs due to a transition between two states is referred to as a line and a spectrum is typically composed of many lines. The frequencies where absorption lines occur, as well as their relative intensities, primarily depend on the electronic, the frequencies will also depend on the interactions between molecules in the sample, the crystal structure in solids, and on several environmental factors. The lines will also have a width and shape that are determined by the spectral density or the density of states of the system. Absorption lines are classified by the nature of the quantum mechanical change induced in the molecule or atom. Rotational lines, for instance, occur when the state of a molecule is changed. Rotational lines are found in the microwave spectral region. Vibrational lines correspond to changes in the state of the molecule and are typically found in the infrared region. Electronic lines correspond to a change in the state of an atom or molecule and are typically found in the visible. X-ray absorptions are associated with the excitation of inner shell electrons in atoms and these changes can also be combined, leading to new absorption lines at the combined energy of the two changes
13.
Water vapor
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Water vapor, water vapour or aqueous vapor, is the gaseous phase of water. It is one state of water within the hydrosphere, water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible, under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds, use of water vapor, as steam, has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution. Likewise the detection of water vapor would indicate a similar distribution in other planetary systems. Water vapor is significant in that it can be evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Whenever a water molecule leaves a surface and diffuses into a surrounding gas, each individual water molecule which transitions between a more associated and a less associated state does so through the absorption or release of kinetic energy. The aggregate measurement of kinetic energy transfer is defined as thermal energy. Liquid water that becomes water vapor takes a parcel of heat with it, the amount of water vapor in the air determines how fast each molecule will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water, in the US, the National Weather Service measures the actual rate of evaporation from a standardized pan open water surface outdoors, at various locations nationwide. Others do likewise around the world, the US data is collected and compiled into an annual evaporation map. The measurements range from under 30 to over 120 inches per year, formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. In some countries, the evaporation rate far exceeds the precipitation rate, evaporative cooling is restricted by atmospheric conditions. Humidity is the amount of vapor in the air. The vapor content of air is measured with devices known as hygrometers, the measurements are usually expressed as specific humidity or percent relative humidity. This condition is referred to as complete saturation. Humidity ranges from 0 gram per cubic metre in dry air to 30 grams per cubic metre when the vapor is saturated at 30 °C, another form of evaporation is sublimation, by which water molecules become gaseous directly, leaving the surface of ice without first becoming liquid water. Sublimation accounts for the slow disappearance of ice and snow at temperatures too low to cause melting
14.
Astronomical spectroscopy
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Astronomical spectroscopy is used to measure three major bands of radiation, visible spectrum, radio, and X-ray. While all spectroscopy looks at areas of the spectrum, different methods are required to acquire the signal depending on the frequency. Ozone and molecular oxygen absorb light with wavelengths under 300 nm, meaning that X-ray, radio signals have much longer wavelengths than optical signals, and require the use of antennas or radio dishes. Physicists have been looking at the solar spectrum since Isaac Newton first used a prism to observe the refractive properties of light. In the early 1800s Joseph von Fraunhofer used his skills as a maker to create very pure prisms. The resolution of a prism is limited by its size, a prism will provide a more detailed spectrum. This issue was resolved in the early 1900s with the development of high-quality reflection gratings by J. S, plaskett at the Dominion Observatory in Ottawa, Canada. By creating a blazed grating which utilizes a number of parallel mirrors. These new spectroscopes were more detailed than a prism, required less light, the limitation to a blazed grating is the width of the mirrors, which can only be ground a finite amount before focus is lost, the maximum is around 1000 lines/mm. In order to overcome this limitation holographic gratings were developed, volume phase holographic gratings use a thin film of dichromated gelatin on a glass surface, which is subsequently exposed to a wave pattern created by an interferometer. The holographic gratings can have up to 6000 lines/mm and can be up to twice as efficient in collecting light as blazed gratings, because they are sealed between two sheets of glass, the holographic gratings are very versatile, potentially lasting decades before needing replacement. Light dispersed by the grating or prism in a spectrograph can be recorded by a detector, historically, photographic plates were widely used to record spectra until electronic detectors were developed, and today optical spectrographs most often employ charge-coupled devices. The wavelength scale of a spectrum can be calibrated by observing the spectrum of emission lines of known wavelength from a gas-discharge lamp, radio astronomy was founded with the work of Karl Jansky in the early 1930s, while working for Bell Labs. He built an antenna to look at potential sources of interference for transatlantic radio transmissions. One of the sources of noise discovered came not from Earth, in 1942, JS Hey captured the suns radio frequency using military radar receivers. Radio spectroscopy started with the discovery of the 21-centimeter H I line in 1951, radio interferometry was pioneered in 1946, when Joseph Lade Pawsey, Ruby Payne-Scott and Lindsay McCready used a single antenna atop a sea cliff to observe 200 MHz solar radiation. Two incident beams, one directly from the sun and the other reflected from the sea surface, the first multi-receiver interferometer was built in the same year by Martin Ryle and Vonberg. In 1960, Ryle and Antony Hewish published the technique of aperture synthesis to analyze interferometer data, the aperture synthesis process, which involves autocorrelating and discrete Fourier transforming the incoming signal, recovers both the spatial and frequency variation in flux
15.
Theory of tides
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In 1609 Johannes Kepler correctly suggested that the gravitation of the Moon causes the tides, basing his argument upon ancient observations and correlations. The influence of the Moon on tides was mentioned in Ptolemys Tetrabiblos as having derived from ancient observation, in 1616, Galileo Galilei wrote Discourse on the Tides, in a letter to Cardinal Orsini. In this discourse, he tried to explain the occurrence of the tides as the result of the Earths rotation and revolution around the Sun, Galileo believed that the oceans moved like water in a large basin, as the basin moves, so does the water. Therefore, as the Earth revolves, the force of the Earths rotation causes the oceans to alternately accelerate and retardate, in subsequent centuries, further analysis led to the current tidal physics. Galileo rejected Keplers explanation of the tides, the dynamic theory of tides describes and predicts the actual real behavior of ocean tides. Laplaces theory of ocean tides took into account friction, resonance and it predicted the large amphidromic systems in the worlds ocean basins and explains the oceanic tides that are actually observed. The equilibrium tide theory calculates the height of the wave of less than half a meter. Satellite observations confirm the accuracy of the theory, and the tides worldwide are now measured to within a few centimeters. Measurements from the CHAMP satellite closely match the models based on the TOPEX data, accurate models of tides worldwide are essential for research since the variations due to tides must be removed from measurements when calculating gravity and changes in sea levels. In 1776, Pierre-Simon Laplace formulated a set of linear partial differential equations. Coriolis effects are introduced as well as lateral forcing by gravity, Laplace obtained these equations by simplifying the fluid dynamic equations. But they can also be derived from energy integrals via Lagranges equation, william Thomson rewrote Laplaces momentum terms using the curl to find an equation for vorticity. Under certain conditions this can be rewritten as a conservation of vorticity. Laplaces improvements in theory were substantial, but they still left prediction in an approximate state, thomsons work in this field was then further developed and extended by George Darwin, applying the lunar theory current in his time. Darwins symbols for the tidal harmonic constituents are still used, Doodsons work was carried out and published in 1921. Doodson devised a system for specifying the different harmonic components of the tide-generating potential, the Doodson numbers. Since the mid-twentieth century further analysis has generated many more terms than Doodsons 388, about 62 constituents are of sufficient size to be considered for possible use in marine tide prediction, but sometimes many fewer can predict tides to useful accuracy. Amplitudes of tidal constituents are given below for six example locations, Eastport, Maine, Biloxi, Mississippi, San Juan, Puerto Rico, Kodiak, Alaska, San Francisco, California, and Hilo, Hawaii
16.
Planetary differentiation
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Such a process tends to create a core and mantle. Sometimes a chemically distinct crust forms on top of the mantle, the process of planetary differentiation has occurred on planets, dwarf planets, the asteroid 4 Vesta, and natural satellites. When the Sun ignited in the nebula, hydrogen, helium. The solar wind and radiation pressure forced these low-density materials away from the Sun, rocks, and the elements comprising them, were stripped of their early atmospheres, but themselves remained, to accumulate into protoplanets. Protoplanets had higher concentrations of radioactive elements early in their history, heating due to radioactivity, impacts, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones, it was possible for denser materials to sink towards the center, the compositions of some meteorites show that differentiation also took place in some asteroids, that are parental bodies for meteoroids. The short-lived radioactive isotope 26Al was probably the source of heat. When protoplanets accrete more material, the energy of impact causes local heating, in addition to this temporary heating, the gravitational force in a sufficiently large body creates pressures and temperatures which are sufficient to melt some of the materials. This allows chemical reactions and density differences to mix and separate materials, on Earth, a large piece of molten iron is sufficiently denser than continental crust material to force its way down through the crust to the mantle. In the outer Solar System a similar process may take place but with lighter materials, they may be such as methane, water as liquid or ice. High-density materials tend to sink through lighter materials and this tendency is affected by the relative structural strengths, but such strength is reduced at temperatures where both materials are plastic or molten. Iron, the most common element that is likely to form a dense molten metal phase. With it, many siderophile elements also travel downward, however, not all heavy elements make this transition as some chalcophilic heavy elements bind into low-density silicate and oxide compounds, which differentiate in the opposite direction. Even lighter still are the watery liquid hydrosphere and the gaseous, lighter materials tend to rise through material with a higher density. They may take on dome-shaped forms called diapirs when doing so, on Earth, salt domes are salt diapirs in the crust which rise through surrounding rock. Diapirs of molten low-density silicate rocks such as granite are abundant in the Earths upper crust, the hydrated, low-density serpentinite formed by alteration of mantle material at subduction zones can also rise to the surface as diapirs. Other materials do likewise, a low-temperature, near-surface example is provided by mud volcanos and it is also high in uranium and thorium. Magma in the Earth is produced by melting of a source rock
17.
Volcano
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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, therefore, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
18.
Fluvial
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Fluvial is a term used in geography and geology to refer to the processes associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, fluvial processes include the motion of sediment and erosion or deposition on the river bed. Erosion by moving water can happen in two ways, firstly, the movement of water across the bed exerts a shear stress directly onto the bed. However, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed, at the same time the fragments themselves are ground down, becoming smaller and more rounded. Sediment in rivers is transported as either bedload or suspended load, there is also a component carried as dissolved material. For each grain size there is a velocity at which the grains start to move. However the grains will continue to be transported even if the velocity falls below the entrainment velocity due to the friction between the grains and the river bed. Eventually the velocity will fall low enough for the grains to be deposited and this is shown by the Hjulstrøm curve. A river is continually picking up and dropping solid particles of rock, where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up, areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium. Even small streams make alluvial deposits, but it is in the plains and deltas of large rivers that large. The amount of matter carried by a river is enormous. The names of rivers derive from the color that the transported matter gives the water. For example, the Huang He in China is literally translated Yellow River, and it has been estimated that the Mississippi River annually carries 406 million tons of sediment to the sea, the Yellow River 796 million tons, and the Po River in Italy 67 million tons. Lacustrine - of or relating to a lake maritime - of or relating the sea oceanic - of or relating to an ocean palustrine - of or relating to a marsh
19.
Antifreeze
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An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments, freezing and boiling points are colligative properties of a solution, which depend on the concentration of the dissolved substance. Because water has good properties as a coolant, water plus antifreeze is used in combustion engines and other heat transfer applications, such as HVAC chillers. The purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes, commercially, both the additive and the mixture are called antifreeze, depending on the context. Salts are frequently used for de-icing, but salt solutions are not used for cooling systems because they can cause corrosion to metals. Instead, non-corrosive antifreezes are commonly used for critical de-icing, such as for aircraft wings, most automotive engines are water-cooled to remove waste heat, although the water is actually antifreeze/water mixture and not plain water. The term engine coolant is used in the automotive industry. When used in a context, corrosion inhibitors are added to help protect vehicles radiators. Water pump seal lubricant is also added, antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid. These should not be confused with core plugs, whose purpose is to allow removal of used in the casting process of engine blocks. On the other hand, if the engine coolant gets too hot, it might boil while inside the engine, causing voids, leading to localized hot spots, if plain water were to be used as an engine coolant, it would promote galvanic corrosion. Proper engine coolant and a pressurized coolant system can help obviate the problems which make plain water incompatible with automotive engines. With proper antifreeze, a temperature range can be tolerated by the engine coolant, such as −34 °F to +265 °F for 50% propylene glycol diluted with water. Early engine coolant antifreeze was methanol, as radiator caps were vented, not sealed, the methanol was lost to evaporation, requiring frequent replenishment to avoid freezing of the coolant. Methanol also accelerates corrosion of the metals, especially aluminum, used in the engine, ethylene glycol was developed, and soon replaced methanol as an engine cooling system antifreeze. It has a low volatility compared to methanol and to water. Before the 1950s, coolant systems were unpressurized and the engine was often cooler than modern automotive engines, by pressurizing the coolant system with a radiator cap, the boiling point of the fluid is increased, permitting higher engine temperatures and better fuel efficiency. Pressurized systems do not appreciably change the freezing point, the most common water-based antifreeze solutions used in electronics cooling are mixtures of water and either ethylene glycol or propylene glycol
20.
Mars
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Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is referred to as the Red Planet because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet, Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan, there are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers, liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is about 6⁄1000 that of the Earths, except at the lowest elevations for short periods. The two polar ice caps appear to be largely of water. The volume of ice in the south polar ice cap, if melted. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, optical ground-based telescopes are typically limited to resolving features about 300 kilometers across when Earth and Mars are closest because of Earths atmosphere. Mars is approximately half the diameter of Earth with an area only slightly less than the total area of Earths dry land. Mars is less dense than Earth, having about 15% of Earths volume and 11% of Earths mass, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. It can look like butterscotch, other common colors include golden, brown, tan. Like Earth, Mars has differentiated into a metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ±65 kilometers, consisting primarily of iron and this iron sulfide core is thought to be twice as rich in lighter elements than Earths. The core is surrounded by a mantle that formed many of the tectonic and volcanic features on the planet
21.
Venus
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Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period of any planet in the Solar System and it is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the sky after the Moon, reaching an apparent magnitude of −4.6. Because Venus orbits within Earths orbit it is a planet and never appears to venture far from the Sun. Venus is a planet and is sometimes called Earths sister planet because of their similar size, mass, proximity to the Sun. It is radically different from Earth in other respects and it has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the surface is 92 times that of Earth. Venus is by far the hottest planet in the Solar System, with a surface temperature of 735 K. Venus is shrouded by an layer of highly reflective clouds of sulfuric acid. It may have had water oceans in the past, but these would have vaporized as the temperature rose due to a greenhouse effect. The water has probably photodissociated, and the hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venuss surface is a dry desertscape interspersed with rocks and is periodically resurfaced by volcanism. As one of the brightest objects in the sky, Venus has been a fixture in human culture for as long as records have existed. It has been sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the morning star. Venus was the first planet to have its motions plotted across the sky, as the closest planet to Earth, Venus has been a prime target for early interplanetary exploration. It was the first planet beyond Earth visited by a spacecraft, Venuss thick clouds render observation of its surface impossible in visible light, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more missions. Venus is one of the four planets in the Solar System
22.
Groundwater
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Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is also withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is also evidence that water may also exist in the subsurface of Jupiters moon Europa. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
23.
Natural satellite
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A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet. In the Solar System there are six planetary satellite systems containing 178 known natural satellites, four IAU-listed dwarf planets are also known to have natural satellites, Pluto, Haumea, Makemake, and Eris. As of January 2012, over 200 minor-planet moons have been discovered, the Earth–Moon system is unique in that the ratio of the mass of the Moon to the mass of Earth is much greater than that of any other natural-satellite–planet ratio in the Solar System. At 3,474 km across, Earths Moon is 0.27 times the diameter of Earth, the first known natural satellite was the Moon, but it was considered a planet until Copernicus introduction of heliocentrism in 1543. Until the discovery of the Galilean satellites in 1610, however, galileo chose to refer to his discoveries as Planetæ, but later discoverers chose other terms to distinguish them from the objects they orbited. The first to use of the satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus in 1610. He derived the term from the Latin word satelles, meaning guard, attendant, or companion, the term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of moon. In 1957, however, the launching of the artificial object Sputnik created a need for new terminology, to further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earths natural satellite, but not when referring to other natural satellites. A few recent authors define moon as a satellite of a planet or minor planet, there is no established lower limit on what is considered a moon. Small asteroid moons, such as Dactyl, have also been called moonlets, the upper limit is also vague. Two orbiting bodies are described as a double body rather than primary. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition of what constitutes a moon, some authors consider the Pluto–Charon system to be a double planet. In contrast, irregular satellites are thought to be captured asteroids possibly further fragmented by collisions, most of the major natural satellites of the Solar System have regular orbits, while most of the small natural satellites have irregular orbits. The Moon and possibly Charon are exceptions among large bodies in that they are thought to have originated by the collision of two large proto-planetary objects. The material that would have placed in orbit around the central body is predicted to have reaccreted to form one or more orbiting natural satellites. As opposed to planetary-sized bodies, asteroid moons are thought to form by this process. Triton is another exception, although large and in a close, circular orbit, its motion is retrograde, most regular moons in the Solar System are tidally locked to their respective primaries, meaning that the same side of the natural satellite always faces its planet. The only known exception is Saturns natural satellite Hyperion, which rotates chaotically because of the influence of Titan
24.
Dwarf planet
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A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite. The International Astronomical Union currently recognizes five dwarf planets, Ceres, Pluto, Haumea, Makemake, another hundred or so known objects in the Solar System are suspected to be dwarf planets. Individual astronomers recognize several of these, and in August 2011 Mike Brown published a list of 390 candidate objects, Stern states that there are more than a dozen known dwarf planets. Only two of these bodies, Ceres and Pluto, have observed in enough detail to demonstrate that they actually fit the IAUs definition. The IAU accepted Eris as a dwarf planet because it is more massive than Pluto and they subsequently decided that unnamed trans-Neptunian objects with an absolute magnitude brighter than +1 are to be named under the assumption that they are dwarf planets. The classification of bodies in other systems with the characteristics of dwarf planets has not been addressed. Starting in 1801, astronomers discovered Ceres and other bodies between Mars and Jupiter which were for some decades considered to be planets. Between then and around 1851, when the number of planets had reached 23, astronomers started using the asteroid for the smaller bodies. With the discovery of Pluto in 1930, most astronomers considered the Solar System to have nine planets and it was roughly one-twentieth the mass of Mercury, which made Pluto by far the smallest planet. Although it was more than ten times as massive as the largest object in the asteroid belt, Ceres. In the 1990s, astronomers began to find objects in the region of space as Pluto. Many of these shared several of Plutos key orbital characteristics, and Pluto started being seen as the largest member of a new class of objects and this led some astronomers to stop referring to Pluto as a planet. Several terms, including subplanet and planetoid, started to be used for the now known as dwarf planets. By 2005, three trans-Neptunian objects comparable in size to Pluto had been reported and it became clear that either they would also have to be classified as planets, or Pluto would have to be reclassified. Astronomers were also confident that more objects as large as Pluto would be discovered, Eris was discovered in January 2005, it was thought to be slightly larger than Pluto, and some reports informally referred to it as the tenth planet. As a consequence, the became a matter of intense debate during the IAU General Assembly in August 2006. The IAUs initial draft proposal included Charon, Eris, and Ceres in the list of planets, dropping Charon from the list, the new proposal also removed Pluto, Ceres, and Eris, because they have not cleared their orbits. The IAUs final Resolution 5A preserved this three-category system for the bodies orbiting the Sun
25.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
26.
Planetary system
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A planetary system is a set of gravitationally bound non-stellar objects in orbit around a star or star system. The Sun together with its system, which includes Earth, is known as the Solar System. The term exoplanetary system is used in reference to other planetary systems. There are at least 2,701 known planetary systems, including 610 systems consisting of planets as of 1 April 2017. These systems contain more than 3,607 known exoplanets, debris disks are also known to be common, though other objects are more difficult to observe. Of particular interest to astrobiology is the zone of planetary systems where planets could have surface liquid water. Historically, heliocentrism was opposed to geocentrism, the notion of a heliocentric Solar System, with the Sun at the center, is possibly first suggested in the Vedic literature of ancient India, which often refer to the Sun as the centre of spheres. Some interpret Aryabhattas writings in Āryabhaṭīya as implicitly heliocentric, the idea was first proposed in western philosophy and Greek astronomy as early as the 3rd century BC by Aristarchus of Samos, but had received no support from most other ancient astronomers. De revolutionibus orbium coelestium by Nicolaus Copernicus, published in 1543, was the first mathematically predictive heliocentric model of a planetary system and he was burned at the stake for his ideas by the Roman Inquisition. In the 18th century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia and his theories gained traction through the 19th and 20th centuries despite a lack of supporting evidence. The first confirmed detection of an exoplanet was in 1992, with the discovery of several planets orbiting the pulsar PSR B1257+12. The first confirmed detection of exoplanets of a star was made in 1995. The frequency of detections has increased since then, particularly through advancements in methods of detecting extrasolar planets, planetary systems come from protoplanetary disks that form around stars as part of the process of star formation. During formation of a system much material is gravitationally scattered into far-flung orbits, Planets orbiting pulsars have been discovered, and pulsars are the remnants of the supernova explosions of high-mass stars. Planets found around pulsars may have formed as a result of pre-existing stellar companions that were almost entirely evaporated by the supernova blast, alternatively, planets may form in an accretion disk of fallback matter surrounding a pulsar. Fallback disks of matter that failed to orbit during a supernova may also form planets around black holes. As the star mass, planets that are not engulfed move further out from the star. Planets in evolved binary systems, Hagai B, perets,13 Jan 2011 Can Planets survive Stellar Evolution
27.
Mars Reconnaissance Orbiter
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Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory. The mission is managed by the California Institute of Technology, at the JPL, in La Cañada Flintridge, California, for the NASA Science Mission Directorate, Washington and it was launched August 12,2005, and attained Martian orbit on March 10,2006. In November 2006, after five months of aerobraking, it entered its science orbit. It paves the way for future spacecraft by monitoring Mars daily weather and surface conditions, studying potential landing sites, MROs telecommunications system will transfer more data back to Earth than all previous interplanetary missions combined, and MRO will serve as a highly capable relay satellite for future missions. One of two missions considered for the 2003 Mars launch window, the MRO proposal lost against what became known as the Mars Exploration Rovers. The orbiter mission was rescheduled for launch in 2005, and NASA announced its name, Mars Reconnaissance Orbiter. MRO is modeled after NASAs highly successful Mars Global Surveyor to conduct surveillance of Mars from orbit, early specifications of the satellite included a large camera to take high resolution pictures of Mars. Garvin, the Mars exploration program scientist for NASA, proclaimed that MRO would be a microscope in orbit, the satellite was also to include a visible-near-infrared spectrograph. On October 3,2001, NASA chose Lockheed Martin as the contractor for the spacecrafts fabrication. By the end of 2001 all of the instruments were selected. There were no major setbacks during MROs construction, and the spacecraft was moved to John F. Kennedy Space Center on May 1,2005 to prepare it for launch, MRO science operations were initially scheduled to last two Earth years, from November 2006 to November 2008. One of the main goals is to map the Martian landscape with its high-resolution cameras in order to choose landing sites for future surface missions. The MRO played an important role in choosing the site of the Phoenix Lander. The initial site chosen by scientists was imaged with the HiRISE camera, after analysis with HiRISE and the Mars Odysseys THEMIS instrument a new site was chosen. Mars Science Laboratory, a highly maneuverable rover, also had its landing site inspected, the MRO provided critical navigation data during their landings and acts as a telecommunications relay. MRO is using its onboard scientific equipment to study the Martian climate, weather, atmosphere, and geology, in addition, MRO was tasked with looking for the remains of the previously lost Mars Polar Lander and Beagle 2 spacecraft. Beagle 2 was found by the orbiter at the beginning of 2015, after its main science operations are completed, the probes extended mission is to be the communication and navigation system for landers and rover probes
28.
Vapor
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A vapor is different from an aerosol. An aerosol is a suspension of particles of liquid, solid. For example, water has a temperature of 647 K. In the atmosphere at ordinary temperatures, therefore, gaseous water will condense into a liquid if its pressure is increased sufficiently. A vapor may co-exist with a liquid, when this is true, the two phases will be in equilibrium, and the gas-partial pressure will be equal to the equilibrium vapor pressure of the liquid. Vapor refers to a gas phase at a temperature where the substance can also exist in the liquid or solid state. If the vapor is in contact with a liquid or solid phase, the term gas refers to a compressible fluid phase. Fixed gases are gases for which no liquid or solid can form at the temperature of the gas, a liquid or solid does not have to boil to release a vapor. Vapor is responsible for the processes of cloud formation and condensation. It is commonly employed to carry out the processes of distillation. The constituent molecules of a vapor possess vibrational, rotational, and these motions are considered in the kinetic theory of gases. The vapor pressure is the pressure from a liquid or a solid at a specific temperature. The equilibrium vapor pressure of a liquid or solid is not affected by the amount of contact with the liquid or solid interface, the normal boiling point of a liquid is the temperature at which the vapor pressure is equal to normal atmospheric pressure. For two-phase systems, the pressure of the individual phases are equal. The total vapor pressure is the sum of the component partial pressures, perfumes contain chemicals that vaporize at different temperatures and at different rate in scent accords known as notes. Atmospheric water vapor is found near the surface, and may condense into small liquid droplets and form meteorological phenomena such as fog, mist. Mercury-vapor lamps and sodium vapor lamps produce light from atoms in excited states, flammable liquids do not burn when ignited. It is the cloud above the liquid that will burn if the vapors concentration is between the lower flammable limit and upper flammable limit of the flammable liquid
29.
Pascal (unit)
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The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
30.
Seasonal flows on warm Martian slopes
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Seasonal flows on warm Martian slopes are thought to be salty water flows occurring during the warmest months on Mars. The flows are narrow and exhibit relatively dark markings on steep slopes, appear and incrementally grow during warm seasons, liquid brines near the surface almost certainly explain this activity, but the exact source of the water and the mechanism behind its motion are not understood. On October 5,2015, possible RSLs were reported on Mount Sharp near the Curiosity rover, research indicates that in the past there was liquid water flowing on the surface of Mars, creating large areas similar to Earths oceans. However, the remains as to where the water has gone. The Mars Reconnaissance Orbiter is a spacecraft launched in 2005 designed to conduct reconnaissance. The spacecraft is managed by the Jet Propulsion Laboratory, the HiRISE instrument is at the forefront of the ongoing RSL studies as it helps chart the features with images of closely monitored sites typically taken every few weeks. RSL advance rates are highest at the beginning of each season, active RSL also occur in equatorial regions, most commonly in the Valles Marineris troughs. This may indicate the water quickly evaporates upon reaching the surface, a number of different hypotheses for RSL formation have been proposed. The seasonality, latitude distribution, and brightness changes strongly indicate a volatile material —such as water or liquid CO2 — is involved, one hypothesis is that RSL could form by rapid heating of nocturnal frost. Another one proposes flows of carbon dioxide, but the settings in which the flows occur are too warm for carbon-dioxide frost, other hypotheses include dry granular flows, but no entirely dry process can explain seasonal flows that progressively grow over weeks and months. Seasonal melting of ice would explain the RSL observations. However, recent direct observations of seasonal deposition of soluble salts strongly suggest that RSL are created by a water brine, the leading hypothesis involves the flow of brines —very salty water. Salt deposits over much of Mars indicate that brine was abundant in Marss past, salinity lowers the freezing point of water to sustain a liquid flow. Less saline water would freeze at the observed temperatures, Thermal infrared data from the Thermal Emission Imaging System on board the 2001 Mars Odyssey orbiter, have allowed the temperature conditions under which RSL form to be constrained. While a small number of RSL are visible at temperatures above the point of water, most are not. Some scientists think that under these conditions, a brine of iron sulphate or calcium chloride is the most likely mode of RSL formation. Experiments and calculations demonstrated that recurring slope lineae could be produced by the deliquescence and rehydration of hydrous chlorides, however, under present Martian atmospheric conditions there is not enough water to complete this process. But, the believe that there is enough water still stored from the last time the climate was wetter
31.
Brine
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Brine is a solution of salt in water. In different contexts, brine may refer to salt solutions ranging from about 3. 5% up to about 26%, fahrenheit could reliably reproduce by freezing brine. By reference, seawater usually freezes at −2 °C, at 100 °C, saturated sodium chloride brine is about 28% salt by weight. At 0 °C, brine can only hold about 26% salt, the thermal conductivity of seawater is 0.6 W/mK at 25 °C. The majority of hydrogen produced through electrolysis is a side product in the production of chlorine. 2 NaCl +2 H2O →2 NaOH + H2 + Cl2 Brine is a fluid used in large refrigeration installations for the transport of thermal energy from place to place. The lowest freezing point obtainable for NaCl brine is −21.1 °C at 23. 3wt% NaCl and this is called the eutectic point. In lower temperatures, a solution can be used to de-ice or reduce freezing temperatures on roads. In cooking, brine is used for food brining and salting, in hydrology, brine is a form of salt water, namely, water with relatively high concentration of salt. Brine mining Saline water Brackish water
32.
European Space Agency
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The European Space Agency is an intergovernmental organisation of 22 member states, dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a staff of about 2,000. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching, after World War II, many European scientists left Western Europe in order to work with the United States. The meeting was attended by representatives from eight countries, including Harrie Massey. The Western European nations decided to have two different agencies, one concerned with developing a system, ELDO, and the precursor of the European Space Agency. The latter was established on 20 March 1964 by an agreement signed on 14 June 1962, from 1968 to 1972, ESRO launched seven research satellites. ESA in its current form was founded with the ESA Convention in 1975, ESA has 10 founding member states, Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland and the United Kingdom. These signed the ESA Convention in 1975 and deposited the instruments of ratification by 1980, during this interval the agency functioned in a de facto fashion. ESA launched its first major scientific mission in 1975, Cos-B, ESA joined NASA in the IUE, the worlds first high-orbit telescope, which was launched in 1978 and operated very successfully for 18 years. A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and Grigg–Skjellerup. Hipparcos, a mission, was launched in 1989 and in the 1990s SOHO, Ulysses. Recent scientific missions in co-operation with NASA include the Cassini–Huygens space probe, as the successor of ELDO, ESA has also constructed rockets for scientific and commercial payloads. Ariane 1, launched in 1979, brought mostly commercial payloads into orbit from 1984 onward, the successor launch vehicle of Ariane 5, the Ariane 6 is already in the definition stage and is envisioned to enter service in the 2020s. The beginning of the new millennium saw ESA become, along with agencies like NASA, JAXA, ISRO, CSA and Roscosmos, one of the major participants in scientific space research. Although ESA had relied on co-operation with NASA in previous decades, especially the 1990s, changed circumstances led to decisions to rely more on itself, a 2011 press issue thus stated, Russia is ESAs first partner in its efforts to ensure long-term access to space. ESA maintains its scientific and research projects mainly for astronomy-space missions such as Corot, launched on 27 December 2006 and this is the reason space exploration is an integral part of overall space activities. It has always been so, and it will be more important in the future. ESA describes its work in two overlapping ways, For the general public the various fields of work are described as Activities, Member states participate to varying degrees in the mandatory and optional space programmes
33.
Mars Express
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Mars Express is a space exploration mission being conducted by the European Space Agency. The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency, Express originally referred to the speed and efficiency with which the spacecraft was designed and built. Mars Express consists of two parts, the Mars Express Orbiter and the Beagle 2, a designed to perform exobiology. Due to the science return and the highly flexible mission profile, Mars Express has been granted six mission extensions. Some of the instruments on the orbiter, including the systems and some spectrometers. The design of Mars Express is based on ESAs Rosetta mission, on which a sum was spent on development. The same design was used for the Venus Express mission in order to increase reliability and reduce development cost. Because of these redesigns and repurposings, the total cost of the project was about $345 million- less than half of comparable U. S. missions. The Mars Express mission is dedicated to the study of the interior, subsurface, surface and atmosphere. Mars exploration is crucial for an understanding of the Earth from the perspective of comparative planetology. The spacecraft originally carried seven instruments, a small lander, a lander relay. All of the instruments take measurements of the surface, atmosphere and interplanetary media, from the spacecraft in polar orbit. The total initial Mars Express budget excluding the lander was €150 million, the prime contractor for the construction of Mars Express Orbiter was EADS Astrium Satellites. In the years preceding the launch of a spacecraft numerous teams of experts distributed over the companies and organisations prepared the space. Each of these teams focussed on the area of its responsibility, the spacecraft was launched on June 2,2003 at 23,45 local time from Baikonur Cosmodrome in Kazakhstan, using a Soyuz-FG/Fregat rocket. The Mars Express and Fregat booster were initially put into a 200 km Earth parking orbit, the Fregat and Mars Express separated at approximately 19,17 UT. The solar panels were deployed and a trajectory correction manoeuvre was performed on June 4 to aim Mars Express towards Mars. The Mars Express was the first Russian-launched probe to make it out of LEO since the Soviet Union fell
34.
Europa (moon)
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Europa /jʊˈroʊpə/, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet. It is also the sixth-largest moon in the Solar System, Europa was discovered in 1610 by Galileo Galilei and was named after Europa, the legendary mother of King Minos of Crete and lover of Zeus. Slightly smaller than Earths Moon, Europa is primarily made of rock and has a water-ice crust. It has an atmosphere composed primarily of oxygen. Its surface is striated by cracks and streaks, whereas craters are relatively rare, in addition to Earth-bound telescope observations, Europa has been examined by a succession of space probe flybys, the first occurring in the early 1970s. Europa has the smoothest surface of any solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the seafloor. This may be important in determining if Europa could be habitable, in addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturns moon Enceladus, which are thought to be caused by erupting cryogeysers. The Galileo mission, launched in 1989, provides the bulk of current data on Europa, no spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agencys Jupiter Icy Moon Explorer is a mission to Ganymede that is due to launch in 2022, NASAs planned Europa Multiple-Flyby Mission will be launched in the mid-2020s. Europa, along with Jupiters three other large moons, Io, Ganymede, and Callisto, was discovered by Galileo Galilei on 8 January 1610, and possibly independently by Simon Marius. The first reported observation of Io and Europa was made by Galileo Galilei on 7 January 1610 using a 20×-magnification refracting telescope at the University of Padua. However, in observation, Galileo could not separate Io and Europa due to the low magnification of his telescope. The following day,8 January 1610, Io and Europa were seen for the first time as separate bodies during Galileos observations of the Jupiter system, Europa is named after Europa, daughter of the king of Tyre, a Phoenician noblewoman in Greek mythology. Like all the Galilean satellites, Europa is named after a lover of Zeus, Europa was courted by Zeus and became the queen of Crete. The naming scheme was suggested by Simon Marius, who discovered the four satellites independently, Marius attributed the proposal to Johannes Kepler. The names fell out of favor for a time and were not revived in general use until the mid-20th century. In much of the astronomical literature, Europa is simply referred to by its Roman numeral designation as Jupiter II or as the second satellite of Jupiter
35.
Tidal flexing
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Tidal heating occurs through the tidal friction processes, orbital and rotational energy are dissipated as heat in either the surface ocean or interior of a planet or satellite. Io, a moon of Jupiter, is the most volcanically active body in the system, evidenced by active volcanos. Ios heating is a result of the tug between Jupiter and the other Galilean moons, the eccentricity of Ios orbit causes the height of Ios tidal bulge to vary significantly over the course of an orbit, the friction from this tidal flexing then heats up its interior. A similar but weaker process is theorised to have melted the lower layers of the ice surrounding the mantle of Jupiters next large moon. Saturns moon Enceladus is similarly thought to have a water ocean beneath its icy crust. The water vapor geysers which eject material from Enceladus are thought to be powered by friction generated within this moons shifting ice crust, im is the imaginary portion of the second order Love number which measures the efficiency of body dissipation within the satellite. This imaginary portion is a function of the satellites bulk shear modulus and these in turn are dependent upon temperature and melting of the satellites interior. Cryovolcano Tidal acceleration Tidal locking Tidal heating of Io
36.
Enceladus
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Enceladus N-cell-AH-dus, is the sixth-largest moon of Saturn. It is about 500 kilometers in diameter, about a tenth of that of Saturns largest moon, Enceladus is mostly covered by fresh, clean ice, making it one of the most reflective bodies of the solar system. Consequently, its temperature at noon only reaches −198 °C. Enceladus was discovered on August 28,1789, by William Herschel, in 2005, the Cassini spacecraft started multiple close flybys of Enceladus, revealing its surface and environment in greater detail. In particular, Cassini discovered water-rich plumes venting from the polar region. Over 100 geysers have been identified, some of the water vapor falls back as snow, the rest escapes, and supplies most of the material making up Saturns E ring. According to NASA scientists, the plumes are similar in composition to comets, in 2014, NASA reported that Cassini found evidence for a large south polar subsurface ocean of liquid water with a thickness of around 10 km. These geyser observations, along with the finding of escaping internal heat and very few craters in the south polar region. Like many other satellites in the systems of the giant planets. Its resonance with Dione excites its orbital eccentricity, which is damped by tidal forces, tidally heating its interior, and possibly driving the geological activity. Enceladus was discovered by Fredrick William Herschel on August 28,1789, during the first use of his new 1.2 m telescope and its faint apparent magnitude and its proximity to the much brighter Saturn and Saturns rings make Enceladus difficult to observe from Earth with smaller telescopes. Like many satellites of Saturn discovered prior to the Space Age, Enceladus was first observed during a Saturnian equinox, at such times, the reduction in glare from the rings makes the moons easier to observe. Prior to the Voyager missions the view of Enceladus improved little from the dot first observed by Herschel, only its orbital characteristics were known, with estimations of its mass, density and albedo. Enceladus is named after the giant Enceladus of Greek mythology and he chose these names because Saturn, known in Greek mythology as Cronus, was the leader of the Titans. Features on Enceladus are named by the International Astronomical Union after characters and places from Burtons translation of The Book of One Thousand, impact craters are named after characters, whereas other feature types, such as fossae, dorsa, planitia, and sulci, are named after places. The IAU has officially named 85 features on Enceladus, most recently Samaria Rupes, Enceladus is one of the major inner satellites of Saturn along with Dione, Tethys, and Mimas. It orbits at 238,000 km from Saturns center and 180,000 km from its cloud tops and it orbits Saturn every 32.9 hours, fast enough for its motion to be observed over a single night of observation. Enceladus is currently in a 2,1 mean-motion orbital resonance with Dione and this resonance maintains Enceladuss orbital eccentricity, which is known as a forced eccentricity
37.
Cassini spacecraft
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Cassini–Huygens is an unmanned spacecraft sent to the planet Saturn. It is a Flagship-class NASA–ESA–ASI robotic spacecraft, Cassini is the fourth space probe to visit Saturn and the first to enter orbit, and its mission is ongoing as of April 2017. It has studied the planet and its natural satellites since arriving there in 2004. Its design includes a Saturn orbiter and a lander for the moon Titan, the two spacecraft are named after astronomers Giovanni Cassini and Christiaan Huygens. On December 25,2004, Huygens separated from the orbiter and it successfully returned data to Earth, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System, on November 30,2016, Cassini entered the final phase of the project. Cassini will dive through the ring of Saturn 20 times. The spacecraft will enter areas that have been untouched up until this point, the first pass of the rings took place on December 4,2016. Cassini continued to study the Saturn system in the following years, however, due to the spacecrafts dwindling fuel resources for further orbital corrections, it is currently planned to be destroyed by diving into the planets atmosphere in September 2017. This method of disposal was chosen to avoid potential biological contamination of Saturns moons, Cassinis death spiral is set to officially begin on April 22,2017 and will take its final plunge on September 15,2017 before it beams its last batch of images. Sixteen European countries and the United States make up the team responsible for designing, building, flying and collecting data from the Cassini orbiter, the mission is managed by NASAs Jet Propulsion Laboratory in the United States, where the orbiter was assembled. Huygens was developed by the European Space Research and Technology Centre, the Centres prime contractor, Aérospatiale of France, assembled the probe with equipment and instruments supplied by many European countries. The VIMS infrared counterpart was provided by NASA, as well as Main Electronic Assembly, on April 16,2008, NASA announced a two-year extension of the funding for ground operations of this mission, at which point it was renamed the Cassini Equinox Mission. This was again extended in February 2010 with the Cassini Solstice Mission, the mission was commonly called Saturn Orbiter Titan Probe during gestation, both as a Mariner Mark II mission and generically. Cassini-Huygens is a mission to the outer planets. The other planetary flagships include Galileo, Voyager, and Viking, Cassini has several objectives, including, Determine the three-dimensional structure and dynamic behavior of the rings of Saturn. Determine the composition of the surfaces and the geological history of each object. Determine the nature and origin of the material on Iapetuss leading hemisphere
38.
Tidal force
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The tidal force is a force that is the secondary effect of the force of gravity, it is responsible for the phenomenon of tides. It arises because the force exerted by one body on another is not constant across it. Thus, the force is differential. Consider the gravitational attraction of the Moon on the oceans nearest to the Moon, the solid Earth, there is a mutual attraction between the Moon and the solid Earth, which can be considered to act on its centre of mass. However, the oceans are more strongly attracted and, especially since they are fluid, they approach the Moon slightly. The far oceans are attracted less, viewing the Earth as a whole, we see that all its mass experiences a mutual attraction with that of the Moon, but the near oceans more so than the far oceans, leading to a separation of the two. When a body is acted on by the gravity of another body, Figure 2 shows the differential force of gravity on a spherical body exerted by another body. These so-called tidal forces cause strains on both bodies and may distort them or even, in cases, break one or the other apart. These strains would not occur if the field were uniform, because a uniform field only causes the entire body to accelerate together in the same direction. In the case of a small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid with two bulges, pointing towards and away from the other body, larger objects distort into an ovoid, and are slightly compressed, which is what happens to the Earths oceans under the action of the Moon. The Earth and Moon rotate about their center of mass or barycenter. To an observer on the Earth, very close to this barycenter, all parts of the Earth are subject to the Moons gravitational forces, causing the water in the oceans to redistribute, forming bulges on the sides near the Moon and far from the Moon. When a body rotates while subject to forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. In the case for the Earth, and Earths Moon, the loss of kinetic energy results in a gain of about 2 milliseconds per century. If the body is enough to its primary, this can result in a rotation which is tidally locked to the orbital motion. Tidal heating produces dramatic volcanic effects on Jupiters moon Io, stresses caused by tidal forces also cause a regular monthly pattern of moonquakes on Earths Moon. Tidal forces contribute to ocean currents, which moderate global temperatures by transporting heat energy toward the poles and it has been suggested that in addition to other factors, harmonic beat variations in tidal forcing may contribute to climate changes
39.
Jupiter
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Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, Jupiter and Saturn are gas giants, the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity, the Romans named it after their god Jupiter. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium and it may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rotation, the planets shape is that of an oblate spheroid. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence, a prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere, Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, the latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4,2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa, Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. Astronomers have discovered nearly 500 planetary systems with multiple planets, Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. Jupiter is composed primarily of gaseous and liquid matter and it is the largest of the four giant planets in the Solar System and hence its largest planet. It has a diameter of 142,984 km at its equator, the average density of Jupiter,1.326 g/cm3, is the second highest of the giant planets, but lower than those of the four terrestrial planets. Jupiters upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, a helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiters atmosphere is approximately 75% hydrogen and 24% helium by mass, the atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, the outermost layer of the atmosphere contains crystals of frozen ammonia. The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found
40.
Hubble Space Telescope
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The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, with a 2. 4-meter mirror, Hubbles four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubbles orbit outside the distortion of Earths atmosphere allows it to take extremely high-resolution images, Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe. The HST was built by the United States space agency NASA, the Space Telescope Science Institute selects Hubbles targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923, Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, Hubbles main mirror was found to have been ground incorrectly, the optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the telescope designed to be serviced in space by astronauts. After launch by Space Shuttle Discovery in 1990, five subsequent Space Shuttle missions repaired, upgraded, the fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved the fifth servicing mission, the telescope is operating as of 2017, and could last until 2030–2040. Its scientific successor, the James Webb Space Telescope, is scheduled for launch in 2018, the history of the Hubble Space Telescope can be traced back as far as 1946, to the astronomer Lyman Spitzers paper Astronomical advantages of an extraterrestrial observatory. In it, he discussed the two advantages that a space-based observatory would have over ground-based telescopes. First, the resolution would be limited only by diffraction, rather than by the turbulence in the atmosphere. Second, a telescope could observe infrared and ultraviolet light. Spitzer devoted much of his career to pushing for the development of a space telescope, space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, oAO-1s battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out observations of stars and galaxies from its launch in 1968 until 1972. The continuing success of the OAO program encouraged increasingly strong consensus within the community that the LST should be a major goal
41.
Ceres (dwarf planet)
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Ceres is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter. Its diameter is approximately 945 kilometers, making it the largest of the planets within the orbit of Neptune. The 33rd-largest known body in the Solar System, it is the dwarf planet within the orbit of Neptune. Composed of rock and ice, Ceres is estimated to approximately one third of the mass of the entire asteroid belt. Ceres is the object in the asteroid belt known to be rounded by its own gravity. From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, Ceres was the first asteroid discovered, by Giuseppe Piazzi at Palermo on 1 January 1801. It was originally considered a planet, but was reclassified as an asteroid in the 1850s after many other objects in similar orbits were discovered. Ceres appears to be differentiated into a core and icy mantle. The surface is probably a mixture of ice and various hydrated minerals such as carbonates. In January 2014, emissions of water vapor were detected from several regions of Ceres and this was unexpected, because large bodies in the asteroid belt typically do not emit vapor, a hallmark of comets. The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015, pictures with a resolution previously unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres, showing a cratered surface. Two distinct bright spots inside a crater were seen in a 19 February 2015 image, on 11 May 2015, NASA released a higher-resolution image showing that, instead of one or two spots, there are actually several. In October 2015, NASA released a true portrait of Ceres made by Dawn. In February 2017, organics were reported to have been detected on Ceres in Ernutet crater, Johann Elert Bode, in 1772, first suggested that an undiscovered planet could exist between the orbits of Mars and Jupiter. Kepler had already noticed the gap between Mars and Jupiter in 1596, the pattern predicted that the missing planet ought to have an orbit with a semi-major axis near 2.8 astronomical units. Although they did not discover Ceres, they found several large asteroids. One of the selected for the search was Giuseppe Piazzi. Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801 and he was searching for the 87th of the Catalogue of the Zodiacal stars of Mr la Caille, but found that it was preceded by another
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Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
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Planetary core
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The planetary core consists of the innermost layer of a planet, which may be composed of solid and liquid layers. Cores of specific planets may be solid or entirely liquid. In the Solar System, core size can range from about 20% to 85% of a planets radius. Gas giants also have cores, though the composition of these are still a matter of debate and range in composition from traditional stony/iron. In 1798, Henry Cavendish calculated the density of the earth to be 5.48 times the density of water. The first detection of Earths core occurred in 1906 by Richard Dixon Oldham upon discovery of the P-wave shadow zone, by 1936 seismologists had determined the size of the overall core as well as the boundary between the fluid outer core and the solid inner core. Planetary systems form from a disk of dust and gas that accrete rapidly into planetesimals around 10 km in diameter. From here gravity takes over to produce Moon to Mars sized planetary embryos, Jupiter and Saturn most likely formed around previously existing rocky and/or icy bodies, rendering these previous primordial planets into gas-giant cores. This is the core accretion model of planet formation. Planetary differentiation is broadly defined as the development from one thing to many things, the hafnium-182/tungsten-182 isotopic system has a half-life of 9 million years, and is approximated as an extinct system after 45 million years. Hafnium is an element and tungsten is siderophile element. The observed Hf/W ratios in iron meteorites constrain metal segregation to under 5 million years, several factors control segregation of a metal core including the crystallization of perovskite. Crystallization of perovskite in a magma ocean is an oxidation process. Impacts between planet-sized bodies in the early Solar System are important aspects in the formation and growth of planets, the giant impact hypothesis states that an impact between a theoretical Mars-sized planet Theia and the early Earth formed the modern Earth and moon. During this impact the majority of the iron from Theia and the Earth became incorporated into the Earths core, core merging between the proto-mars and another differentiated planetoid could have been as fast as 1000 years or as slow as 300,000 years. Earths core contains half the Earths vanadium and chromium, and may contain considerable niobium and tantalum, Earths core is depleted in germanium and gallium. Sulfur is strongly siderophile and only moderately volatile and depleted in the silicate earth, by similar argument, phosphorus may be present up to 0.2 weight %. Hydrogen and carbon, however, are volatile and thus would have been lost during early accretion
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Mantle (geology)
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The mantle is a layer inside a terrestrial planet and some other rocky planetary bodies. For a mantle to form, the body must be large enough to have undergone the process of planetary differentiation by density. The mantle surrounds the planetary core, the mantle is surrounded by the crust. The terrestrial planets, the Moon, two of Jupiters moons and the asteroid Vesta each have a made of silicate rock. Interpretation of spacecraft data suggests that at least two moons of Jupiter, as well as Titan and Triton each have a mantle made of ice or other solid volatile substances. The interior of Earth, similar to the terrestrial planets, is divided into layers of different composition. The mantle is a layer between the crust and the outer core, Earths mantle is a silicate rocky shell with an average thickness of 2,886 kilometres. The mantle makes up about 84% of Earths volume and it is predominantly solid but in geological time it behaves as a very viscous fluid. The mantle encloses the hot core rich in iron and nickel, past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface. A thin crust, the part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick. In some places under the ocean the mantle is exposed on the surface of Earth. The mantle is divided into sections which are based upon results from seismology and these layers are the following, the upper mantle, the transition zone, the lower mantle, and anomalous core–mantle boundary with a variable thickness. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, below the lithosphere the upper mantle becomes notably more plastic. In some regions below the lithosphere, the shear velocity is reduced. Inge Lehmann discovered a seismic discontinuity at about 220 km depth, although this discontinuity has been found in other studies, the transition zone is an area of great complexity, it physically separates the upper and lower mantle. Very little is known about the lower mantle apart from that it appears to be relatively seismically homogeneous, the D layer at the core–mantle boundary separates the mantle from the core. A principal source of the heat that drives plate tectonics is the decay of uranium, thorium. The mantle differs substantially from the crust in its properties as the direct consequence of the difference in composition
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Ice
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Ice is water frozen into a solid state. Depending on the presence of such as particles of soil or bubbles of air. In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far as away the Oort cloud objects, beyond the Solar System, it occurs as interstellar ice. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes, Ice molecules can exhibit up to sixteen different phases that depend on temperature and pressure. When water is cooled rapidly, up to three different types of ice can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below 20 K giving rise to macroscopic quantum phenomena, virtually all the ice on Earths surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic. The most common phase transition to ice Ih occurs when water is cooled below 0°C at standard atmospheric pressure. It may also be deposited directly by water vapor, as happens in the formation of frost, the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety of ways, including cooling, winter sports, as a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral. It possesses a regular crystalline structure based on the molecule of water, an unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8. 3% less dense than liquid water. The density of ice is 0.9167 g/cm3 at 0 °C, liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid, density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C. When water freezes, it increases in volume and it is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. The result of this process is that ice floats on liquid water, sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates an environment for bacterial and algal colonies. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C, during the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water, the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion
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. Bibcode:2016GeoRL..4310088B. doi:10.1002/2016GL070650. ISSN 0094-8276.
