View of Jupiter's active atmosphere, including the Great Red Spot.

An atmosphere (from Greek ατμός - atmos, "vapor" + σφαίρα - sphaira, "sphere") is a layer of gases that may surround a material body of sufficient mass. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A vapor or vapour (see Spelling differences) is a substance in the Gas phase at a Temperature lower than its Critical temperature "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe This page is about the physical properties of gas as a state of matter Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object ^[1] The gases are attracted by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low. Gravitation is a natural Phenomenon by which objects with Mass attract one another Some planets consist mainly of various gases, and therefore have very deep atmospheres (see gas giants). A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily

The term stellar atmosphere is used for the outer region of a star, and typically includes the portion starting from the opaque photosphere outwards. The stellar atmosphere is the outer region of the volume of a Star, lying above the Stellar core, Radiation zone and Convection zone. Relatively low temperature stars may form compound molecules in their outer atmosphere. Earth's atmosphere protects living organisms from ultraviolet rays. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays

Pressure

Main article: atmospheric pressure

Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a planet's gravitational force in combination with the total mass of a column of air above a location. Units of air pressure are based on the internationally-recognized standard atmosphere (atm), which is defined as 101,325 Pa (or 1,013,250 dynes per cm²). The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm M^2 redirects here For other uses see M². CM2 redirects here

The pressure of an atmosphere decreases with altitude due to the diminishing mass of gas above each location. The height at which the pressure from an atmosphere declines by a factor of e (an irrational number with a value of 2. The Mathematical constant e is the unique Real number such that the function e x has the same value as the slope of the tangent line In Mathematics, an irrational number is any Real number that is not a Rational number — that is it is a number which cannot be expressed as a fraction 71828. . . ) is called the scale height and is denoted by H. A scale height is a term often used in scientific contexts for a distance over which a quantity decreases by a factor of e. For an atmosphere with a uniform temperature, the scale height is proportional to the temperature and inversely proportional to the mean molecular mass of dry air times the planet's gravitational acceleration. The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one For such a model atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the exact determination of the atmospheric pressure at any particular altitude is more complex.

Escape

Main article: Atmospheric escape

Surface gravity, the force that holds down an atmosphere, differs significantly among the planets. There are several different processes that can lead to the escape of a planetary atmosphere. The surface gravity, g, of an astronomical or other object is the Gravitational acceleration experienced at its surface For example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from lower gravity objects. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Second, the distance from the sun determines the energy available to heat atmospheric gas to the point where its molecules' thermal motion exceed the planet's escape velocity, the speed at which gas molecules overcome a planet's gravitational grasp. Thermal motion is the random motion of Molecules or other small objects that results from their being in thermal equilibrium at a particular Temperature. In Physics, escape velocity is the speed where the Kinetic energy of an object is equal to the magnitude of its Gravitational potential energy Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite relatively low gravities. TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as TemplateInfobox Planet.--> Triton (ˈtraɪtən, or as in Greek Interstellar planets, theoretically, may also retain thick atmospheres. A rogue planet is an object which has equivalent mass to a Planet and is not gravitationally bound to any Star, and that therefore moves through space as

Since a gas at any particular temperature will have molecules moving at a wide range of velocities, there will almost always be some slow leakage of gas into space. Lighter molecules move faster than heavier ones with the same thermal kinetic energy, and so gases of low molecular weight are lost more rapidly than those of high molecular weight. The kinetic energy of an object is the extra Energy which it possesses due to its motion The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one It is thought that Venus and Mars may have both lost much of their water when, after being photodissociated into hydrogen and oxygen by solar ultraviolet, the hydrogen escaped. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Earth's magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges However, over the past 3 billion years the Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen. ^[2]

Other mechanisms that can cause atmosphere depletion are solar wind-induced sputtering, impact erosion, weathering, and sequestration — sometimes referred to as "freezing out" — into the regolith and polar caps. There are several different processes that can lead to the escape of a planetary atmosphere. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. See also Impact crater An impact event is the Collision of a large Meteoroid, Asteroid or Comet (generically Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. Regolith ( Greek: "blanket rock" is a layer of loose Heterogeneous material covering solid rock. A polar ice cap is a high- Latitude region of a Planet or moon that is covered in Ice.

Composition

Atmospheric gases scatter blue light more than other wavelengths, giving the Earth a blue halo when seen from space.

Initial atmospheric makeup is generally related to the chemistry and temperature of the local solar nebula during planetary formation and the subsequent escape of interior gases. The formation and evolution of the Solar System is estimated to have begun These original atmospheres underwent much evolution over time, with the varying properties of each planet resulting in very different outcomes.

The atmospheres of the planets Venus and Mars are primarily composed of carbon dioxide, with small quantities of nitrogen, argon, oxygen and traces of other gases. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 This article pertains to the chemical element For other uses see Argon (disambiguation. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the

The atmospheric composition on Earth is largely governed by the by-products of the very life that it sustains. Earth's atmosphere consists principally of a roughly 78:20 ratio of nitrogen and oxygen, plus substantial water vapor (a gas), with a minor proportion of carbon dioxide. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five There are traces of hydrogen, and of argon, helium and other "noble" gases (and of volatile pollutants). Exact measurements are difficult, except for particular locales at a particular time.

The low temperatures and higher gravity of the gas giants — Jupiter, Saturn, Uranus, and Neptune — allows them to more readily retain gases with low molecular masses. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System. The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one These planets have hydrogen-helium atmospheres, with trace amounts of more complex compounds.

Two satellites of the outer planets possess non-negligible atmospheres: Titan, a moon of Saturn, and Triton, a moon of Neptune, which are mainly nitrogen. TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as TemplateInfobox Planet.--> Triton (ˈtraɪtən, or as in Greek Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Pluto, in the nearer part of its orbit, has an atmosphere of nitrogen and methane similar to Triton's, but these gases are frozen when farther from the Sun.

Other bodies within the Solar System have extremely thin atmospheres not in equilibrium. These include the Moon (sodium gas), Mercury (sodium gas), Europa (oxygen), Io (sulfur), and Enceladus (water vapor). Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 TemplateInfobox Planet.--> Europa (jʊˈroʊpə; or as TemplateInfobox Planet.--> Io (ˈaɪoʊ, or as Greek Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 TemplateInfobox Planet.--> This article is about the moon of

The atmospheric composition of an extra-solar planet was first determined using the Hubble Space Telescope. An extrasolar planet, or exoplanet, is a Planet beyond the Solar System, orbiting around other Stars As of September 2008 312 The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into Planet HD 209458b is a gas giant with a close orbit around a star in the constellation Pegasus. HD 209458 is an 8th magnitude Star in the Constellation Pegasus. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture In Greek mythology, Pegasus ( Greek: Πήγασος, Pégasos, 'strong' was a winged horse that was the son of Poseidon, in his role The atmosphere is heated to temperatures over 1,000 K, and is steadily escaping into space. Hydrogen, oxygen, carbon and sulfur have been detected in the planet's inflated atmosphere. ^[3]

Structure

Earth

Main article: Earth's atmosphere

The Earth's atmosphere consists, from the ground up, of the troposphere (which includes the planetary boundary layer or peplosphere as lowest layer), stratosphere, mesosphere, ionosphere (or thermosphere), exosphere and the magnetosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and The planetary boundary layer ( PBL) also known as the atmospheric boundary layer ( ABL) or peplosphere, is the lowest part of the Atmosphere The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. This article is about the atmospheric mesosphere for the Earth's mantle see Mesosphere (mantle. The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation The thermosphere is the layer of the Earth's atmosphere directly above the Mesosphere and directly below the Exosphere. The exosphere is the uppermost layer of the atmosphere. On Earth, its lower boundary at the edge of the Thermosphere is estimated to be 500 km to A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. Each of the layers has a different lapse rate, defining the rate of change in temperature with height. The lapse rate is defined as the negative of the rate of change in an atmospheric variable usually Temperature, with height in an atmosphere

Three quarters of the atmosphere lies within the troposphere, and the depth of this layer varies between 17 km at the equator and 7 km at the poles. The ozone layer, which absorbs ultraviolet energy from the Sun, is located primarily in the stratosphere, at altitudes of 15 to 35 km. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays The Kármán line, located within the thermosphere at an altitude of 100 km, is commonly used to define the boundary between the Earth's atmosphere and outer space. However, the exosphere can extend from 500 up to 10,000 km above the surface, where it interacts with the planet's magnetosphere.

Others

Other astronomical bodies such as these listed have known atmospheres.

In our solar system

Outside our solar system

• Atmosphere of HD 209458 b

Circulation

Main article: Atmospheric circulation

The circulation of the atmosphere occurs due to thermal differences when convection becomes a more efficient transporter of heat than thermal radiation. Atmospheric composition This atmosphere is not stable—atoms are continuously lost and replenished from a variety of sources Structure and composition Composition The atmosphere of Venus is composed mainly of Carbon dioxide, along with a small amount of Nitrogen and other The atmosphere of the Moon is very tenuous and insignificant in comparison with that of the Earth. Structure Mars' atmosphere is composed of the following major divisions Lower Atmosphere This is a warm region affected by heat from airborne Dust and TemplateInfobox Planet.--> Europa (jʊˈroʊpə; or as TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as TemplateInfobox Planet.--> This article is about the moon of The atmosphere of Uranus, like that of Neptune, is markedly different from those of the larger Gas giants Jupiter and Saturn. The Atmosphere of Triton extends 800 kilometers above Triton's surface HD 209458 b, also unofficially named Osiris, is an Extrasolar planet that orbits the Solar twin Star HD 209458 in the constellation Atmospheric circulation is the large-scale movement of air and the means (together with the smaller Ocean circulation) by which Heat is distributed on the surface Convection in the most general terms refers to the movement of molecules within Fluids (i Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. On planets where the primary heat source is solar radiation, excess heat in the tropics is transported to higher latitudes. When a planet generates a significant amount of heat internally, such as is the case for Jupiter, convection in the atmosphere can transport thermal energy from the higher temperature interior up to the surface.

Importance

From the perspective of the planetary geologist, the atmosphere is an evolutionary agent essential to the morphology of a planet. A geologist is a contributor to the Science of Geology, studying the physical structure and processes of the Earth and planets of the solar system Comparative anatomy is the study of similarities and differences in the Anatomy of Organisms It is closely related to Evolutionary biology and Phylogeny A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is The wind transports dust and other particles which erodes the relief and leaves deposits (eolian processes). Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) Dust is a general name for minute Solid particles with Diameters less than 500 micrometers. Terrain, or relief, is the third or vertical dimension of land surface. Deposition is the geological process by which material is added to a Landform or land mass Aeolian (or Eolian or Æolian) processes pertain to the activity of the Winds and more specifically to the winds' ability to shape the surface of the Frost and precipitations, which depend on the composition, also influence the relief. The frost line —also known as frost depth or freezing depth —is most commonly the depth that the Groundwater in Soil is expected In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric Climate changes can influence a planet's geological history. Conversely, studying surface of earth leads to an understanding of the atmosphere and climate of a planet - both its present state and its past.

For a meteorologist, the composition of the atmosphere determines the climate and its variations. Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of

For a biologist, the composition is closely dependent on the appearance of the life and its evolution. A biologist is a Scientist devoted to and producing results in Biology through the study of Organisms Typically biologists study organisms and their relationship eVolution is the third Album by eLDee, it was due to be released in 2008

References

1. ^ Ontario Science Centre website
2. ^ Seki, K. ; Elphic, R. C. ; Hirahara, M. ; Terasawa, T. ; Mukai, T. (2001). "On Atmospheric Loss of Oxygen Ions from Earth Through Magnetospheric Processes". Science 291 (5510): 1939-1941. doi:10.1126/science.1058913. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
3. ^ Weaver, D. ; Villard, R. . "Hubble Probes Layer-cake Structure of Alien World's Atmosphere", Hubble News Center, January 31, 2007. Retrieved on 2007-03-11. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1425 BC - Thutmose III, Pharaoh of Egypt, dies (according to the Low Chronology of the 18th Dynasty  

See also

• Atmometer (evaporimeter)
• Edge of space
• Ionosphere
• Stellar atmosphere
• Table of Global Climate System Components