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Encyclopedia > Europa (moon)
Europa
True color image taken by the Galileo probe
Europa, as seen by the Galileo spacecraft
Discovery
Discovered by: G. Galilei
S. Marius
Discovery date: January 7, 1610
Orbital characteristics[1]
Epoch January 8, 2004
Periapsis: 664,300 km (0.00444 AU)
Apoapsis: 677,900 km (0.00453 AU)
Mean radius of orbit: 671,079 km (0.004486 AU)
Eccentricity: 0.0101
Orbital period: 3.551810 d (0.0097243 a)
Avg. orbital speed: 13.740 km/s
Max. orbital speed: 13.879 km/s
Min. orbital speed: 13.601 km/s
Inclination: 1.78° (to the ecliptic)
0.464° (to Jupiter's equator)
Satellite of: Jupiter
Physical characteristics
Mean radius: 1,560.8 km (0.245 Earths)
Surface area: 3.06×107 km² (0.060 Earths)[2]
Volume: 1.593×1010 km³ (0.015 Earths)
Mass: 4.80×1022 kg (0.008 Earths)
Mean density: 3.014 g/cm³
Equatorial surface gravity: 1.314 m/s² (0.134 g)
Escape velocity: 2.025 km/s
Rotation period: Synchronous[3]
Axial tilt: zero
Albedo: 0.64
Surface temp.:
   Surface
min mean max
~50 K 103 K 125 K
Apparent magnitude: 5.3
Atmosphere
Surface pressure: 1 µPa

Europa (IPA: [juˈroʊpə] listen ; Greek Ευρώπη) is the sixth nearest and fourth largest natural satellite of the planet Jupiter. Europa was discovered in 1610 by Galileo Galilei (and independently by Simon Marius shortly thereafter) and is the smallest of the four Galilean moons named in Galileo's honor. Image File history File links Download high resolution version (913x913, 462 KB) [[Melanie is a cool moon my aunt found this moon and she is still living nnnnnnaaaaaaasssssssass[[Media:--~~~~Example. ... Galileo Galilei (15 February 1564 – 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who is closely associated with the scientific revolution. ... Simon Marius Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer. ... is the 7th day of the year in the Gregorian calendar. ... // Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... is the 8th day of the year in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... ‹ The template below (Unit of length) is being considered for deletion. ... The astronomical unit (AU or au or a. ... (This page refers to eccitricity in astrodynamics. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... For the science fiction novella by William Shunn, see Inclination (novella). ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... This article is about Earth as a planet. ... In mathematics, a spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ... To help compare sizes of different areas, here is a list of areas between 10 million km² and 100 million km². See also areas of other orders of magnitude. ... Square kilometre (U.S. spelling: square kilometer), symbol km², is a decimal multiple of SI unit of surface area square metre, one of the SI derived units. ... The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. ... A cubic kilometre (symbol km³) is an SI derived unit of volume. ... This article or section is in need of attention from an expert on the subject. ... Shown above is a computer-generated image of the International Prototype Kilogram (“IPK”). The IPK is the kilogram. ... For other uses, see Density (disambiguation). ... BIC pen cap, about 1 gram. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ... The surface gravity of a Killing horizon is the acceleration, as exerted at infinity, needed to keep an object at the horizon. ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... Space Shuttle Atlantis launches on mission STS-71. ... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis relative to the background stars. ... Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ... In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... For other uses, see Temperature (disambiguation). ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabet”. For information on how to read IPA transcriptions of English words, see IPA chart for English. ... Image File history File links En-Europa. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... The eight planets and three dwarf planets of the Solar System. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Galileo Galilei (15 February 1564 – 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who is closely associated with the scientific revolution. ... Simon Marius Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ...


Europa is primarily composed of silicate rock, has an outer layer of water, and likely has an iron core. At just over 3000 kilometers in diameter, it is slightly smaller than the Earth's moon and the sixth largest moon in the solar system. The satellite has a very tenuous oxygen atmosphere and one of the smoothest surfaces in the solar system. The young surface of the moon is striated by cracks and streaks, while craters are relatively infrequent. Due to a hypothesized water ocean beneath its icy surface, and an energy source provided by tidal heating, Europa has been cited as a possible host of extraterrestrial life.[4] The heat energy ensures the ocean remains liquid and also drives geological activity. In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Iron (disambiguation). ... DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ... This is a list of natural satellites in the solar system, ordered from largest to smallest by average diameter. ... This article is about the Solar System. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite ( a moon), and the planet (called the primary) that it orbits. ... This article is about Extraterrestrial life. ...


The intriguing character of Europa has led to a number of ambitious exploration proposals; to date, only flyby missions have visited the moon. The Galileo mission provided the bulk of current data on the satellite, while the abortive Jupiter Icy Moons Orbiter, cancelled in 2005, was the most ambitious planned spacecraft. Conjecture on extraterrestrial life has ensured a high profile for the moon and led to continued lobbying for future missions.[5][6] Galileo is prepared for mating with the IUS booster Galileo and Inertial Upper Stage being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... Artistss Conception of Jupiter Icy Moons Orbiter The Jupiter Icy Moons Orbiter (JIMO) was a proposed spacecraft designed to explore the icy moons of Jupiter. ...

Contents

Discovery and naming

Europa was discovered in January 1610 by Galileo along with the three other large satellites of the planet Jupiter, Io, Ganymede, and Callisto; the discovery proved that Jupiter exerted an independent gravitational force, which helped buttress the emerging Copernican cosmology.[7] The satellites were apparently independently discovered by Simon Marius shortly afterwards (although there were allegations of plagiarism from Galileo) and he suggested the name after other nomenclature for the Jovian moons failed to catch on; he attributed the proposal to Johannes Kepler.[8][9] Europa is named after the mythological Europa, daughter of Agenor, king of the Phoenician city of Tyre (now in Lebanon), and sister of Cadmus, founder of Thebes, Greece. Atmosphere Surface pressure: trace Composition: 90% sulfur dioxide Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3,642 kilometers, is the fourth largest moon in the Solar System. ... This article is about the natural satellite of Jupiter. ... There is also an asteroid named 204 Kallisto. ... In astronomy, heliocentrism is the theory that the Sun is at the center of the Universe and/or the Solar System. ... Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer and astrologer, and a key figure in the 17th century astronomical revolution. ... Europa and Zeus, on the Greek €2 coin A commemorative Italian euro coin depicts Europa holding a pen over the text of the Constitution of Europe. ... In history and Greek mythology, Agenor (which means very manly) was a king of Tyre. ... Phoenicia (or Phenicia ,[1] from Biblical Phenice [1]) was an ancient civilization centered in the north of ancient Canaan, with its heartland along the coast of modern day Lebanon and Syria. ... The Triumphal Arch Tyre (Arabic , Phoenician , Hebrew Tzor, Tiberian Hebrew , Akkadian , Greek Týros) is a city in the South Governorate of Lebanon. ... Cadmus Sowing the Dragons teeth, by Maxfield Parrish, 1908 Caddmus, or Kadmos (Greek: Κάδμος), in Greek mythology, was the son of the king of Phoenicia (Modern day Lebanon) and brother of Europa. ... Thebes (Demotic Greek: Θήβα — Thíva; Katharevousa: — Thêbai or Thívai) is a city in Greece, situated to the north of the Cithaeron range, which divides Boeotia from Attica, and on the southern edge of the Boeotian plain. ...


The name fell out of favor for a considerable time (as did those of the other Galilean moons), and was not revived in common use until the mid-20th century.[10] In much of the earlier astronomical literature, it is simply referred to by its Roman numeral designation as Jupiter II (a system introduced by Galileo) or as the "second satellite of Jupiter". The discovery of Amalthea in 1892, closer than any of the other known moons of Jupiter, pushed Europa to third position. The Voyager probes discovered three more inner satellites in 1979, so Europa is now considered Jupiter's sixth satellite, though it is still sometimes referred to as Jupiter II.[10] For other uses, see Astronomy (disambiguation). ... Roman numerals are a numeral system originating in ancient Rome, adapted from Etruscan numerals. ... Amalthea (am-əl-thee-ə, IPA: , Greek Αμάλθεια) is the third moon of Jupiter in order of distance from the planet, and the fifth in order of discovery. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ... The Voyager spacecraft Launch of Voyager 2 Voyager is also the name of a planned series of unmanned probes to Mars, cancelled in 1968. ... The inner satellites of Jupiter are four small moons that orbit close to Jupiter, merging with its planetary ring. ...


Orbit

Europa orbits Jupiter in just over three and a half days, with an orbital radius of about 670,900 km (416,900 mi). The satellite follows a very nearly circular orbit, with an eccentricity of only 0.009. Europa's orbital inclination relative to the Jovian equatorial plane is also slight, at 0.470°.[11] ‹ The template below (Unit of length) is being considered for deletion. ... “Miles” redirects here. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ...


Like all the Galilean satellites, Europa is tidally locked to Jupiter, with one hemisphere of the satellite constantly facing the planet. Research suggests the tidal locking may not be full, as a non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that "the surface is probably decoupled from the interior by a subsurface layer of liquid or ductile ice," in keeping with the proposed subsurface ocean.[12] Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ... Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ...


Because of its orbit's slight eccentricity, maintained by the gravitational disturbances from the other Galilean satellites of the planet, the sub-jovian point oscillates about a mean position. Europa strives to assume a slightly elongated shape pointing towards Jupiter in response to the tidal force of the giant planet; because different parts of Europa end up being on different points of this departure from sphericity at varying times, the crust flexes up and down. This motion dissipates energy from Jupiter's rotation into Europa (tidal heating), giving the moon a source of heat and energy, allowing the subsurface ocean to stay liquefied and driving subsurface geological processes. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite ( a moon), and the planet (called the primary) that it orbits. ...


Physical characteristics

Interior of Europa
Interior of Europa

Image File history File links Download high resolution version (2666x2000, 528 KB) Interior of Europa original description: Cutaway view of the possible internal structure of Europa The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft. ... Image File history File links Download high resolution version (2666x2000, 528 KB) Interior of Europa original description: Cutaway view of the possible internal structure of Europa The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft. ...

Internal structure

Europa is somewhat similar in bulk composition to the terrestrial planets, being primarily composed of silicate rock. It has an outer layer of water thought to be around 100 km thick (some, as frozen ice upper crust; some, as liquid ocean underneath the ice), and recent magnetic field data from the Galileo orbiter probe, which orbited Jupiter and studied Europa between 1995 and 2003, shows that Europa generates an induced magnetic field by interacting with Jupiter's field, which suggests the presence of a subsurface conductive layer which is likely a salty liquid-water ocean. Europa probably also contains a metallic iron core.[13] The inner planets, Mercury, Venus, Earth, and Mars, their sizes to scale. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... For other uses, see Rock (disambiguation). ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... Galileo is prepared for mating with the IUS booster Galileo being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... This article does not cite any references or sources. ... For other uses, see Iron (disambiguation). ...


Surface features

Europa is one of the smoothest objects in the solar system.[14]; few features more than a few hundred metres high have been observed, but topographic relief in places approaches a kilometre (0.62 mi)[citation needed]. The prominent markings crisscrossing the moon seem to be mainly albedo features, which emphasize low topography. There are very few craters on Europa because its surface is active and young.[15][16] Europa's albedo (light reflectivity) of 0.64 is one of the highest of all moons because of its icy surface.[11][16] This would seem to indicate a young and active surface; based on estimates of the frequency of cometary bombardment that Europa probably endures, the surface is about 20 to 180 million years old[17] (the geological features of the surface clearly show a variety of ages[citation needed]). Cynthia Phillips, a member of SETI and an expert on Europa states there is currently no consensus among the often contradictory explanations for the surface features of Europa.[2] An albedo feature is a large area on the surface of a planet (or other solar system body) which shows a contrast in brightness or darkness (albedo) with adjacent areas. ... Tycho crater on Earths moon. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ...


Lineae

Approximately natural color image of Europa by the Galileo spacecraft

Europa's most striking surface feature is a series of dark streaks criss-crossing the entire globe. Close examination shows that the edges of Europa's crust on either side of the cracks have moved relative to each other. The larger bands are roughly 20 km (12 mi) across commonly with dark diffuse outer edges, regular striations, and a central band of lighter material. This is a list of lineae on Europa. ... Europa True Color Orbit 1 by the Galileo spacecraft (NASA/JPL image) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Europa True Color Orbit 1 by the Galileo spacecraft (NASA/JPL image) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ...


Among the controversial hypotheses put forward to explain these features, one states that they may have been produced by a series of volcanic water eruptions or geysers as the Europan crust spread open to expose warmer layers beneath. The effect would have been similar to that seen in the Earth's oceanic ridges. These various fractures are thought to have been caused in large part by the tidal stresses exerted by Jupiter; since Europa is tidally locked to Jupiter, and therefore always maintains the same approximate orientation towards the planet, the stress patterns should form a distinctive and predictable pattern. However, only the youngest of Europa's fractures conform to the predicted pattern; other fractures appear to have occurred at increasingly different orientations the older they are. This could be explained if Europa's surface rotates slightly faster than its interior, an effect which is possible due to the subsurface ocean mechanically decoupling the moon's surface from its rocky mantle and to the effects of Jupiter's gravity tugging on the moon's outer ice crust. Comparisons of Voyager and Galileo spacecraft photos serve to put an upper limit on this hypothetical slippage of no faster than once every 10,000 years for the surface relative to its interior. Ganesa Macula, a dark feature on Saturns moon Titan, might be a cryovolcanic dome. ... An oceanic ridge is an underwater mountain range, usually formed by plate tectonics. ... Voyager Project redirects here. ...


Other geological features

Craggy mountains and smooth plates jumbled together in the Conamara Chaos region

Another type of feature present on Europa are circular and elliptical lenticulae, Latin for "freckles". Many are domes, some are pits and some are smooth dark spots. Others have a jumbled or rough texture. The dome tops look like pieces of the older plains around them, suggesting that the domes formed when the plains were pushed up from below. This is a list of named geological features on Europa. ... Chaotic terrain on Europa Original NASA caption This view of the Conamara Chaos region on Jupiters moon Europa taken by NASAs Galileo spacecraft shows an area where the icy surface has been broken into many separate plates that have moved laterally and rotated. ... Chaotic terrain on Europa Original NASA caption This view of the Conamara Chaos region on Jupiters moon Europa taken by NASAs Galileo spacecraft shows an area where the icy surface has been broken into many separate plates that have moved laterally and rotated. ... Conamara Chaos The Conamara Chaos Zone is a region of chaotic terrain on Jupiters moon Europa. ... For other uses, see Latin (disambiguation). ... Freckles are small colored spots of melanin on the exposed skin or membrane of people with complexions fair enough for them to be visible. ...


Among the controversial hypotheses put forward to explain these features, one states that these lenticulae were formed by diapirs of warm ice rising up through the colder ice of the outer crust, much like magma chambers in the Earth's crust. The smooth dark spots could be formed by melt water released when the warm ice breaks through the surface, and the rough, jumbled lenticulae (called regions of "chaos", for example the Conamara Chaos) would then be formed from many small fragments of crust embedded in hummocky dark material, perhaps like icebergs in a frozen sea. A lava lamp illustrates the basic principle of diapirism. ... A magma chamber is a chamber typically between 1 km and 10 km beneath the surface of the Earth formed as rising magma forms a reservoir if it is unable to rise any further. ... Conamara Chaos The Conamara Chaos Zone is a region of chaotic terrain on Jupiters moon Europa. ... Icebergs at Cape York, Greenland Iceberg at Cape York, Greenland Iceberg, Témpanos, Patagonia, Argentina. ...


Subsurface ocean

Two possible models of Europa

It is thought that under the surface there is a layer of liquid water kept warm by tidally generated heat. The temperature on the surface of Europa averages about 110 K (-163 °C) at the equator and only 50 K (-223 °C) at the poles, so the surface water ice is permanently frozen. The first hints of a subsurface ocean came from theoretical considerations of the tidal heating (a consequence of Europa's slightly eccentric orbit and orbital resonance with the other Galilean moons). Galileo imaging team members have analyzed Voyager and Galileo images of Europa to argue that Europa's geological features also demonstrate the existence of a subsurface ocean.[18] The most dramatic example is "chaos terrain," a common feature on Europa's surface that some interpret as a region where the subsurface ocean melted through the icy crust. This interpretation is extremely controversial. Most geologists who have studied Europa favor what is commonly called the "thick ice" model, in which the ocean has rarely, if ever, directly interacted with the surface.[19] The different models for the estimation of the ice shell thickness give values between a few hundred meters and tens of kilometers.[20] Image File history File links Size of this preview: 437 × 600 pixel Image in higher resolution (1192 × 1636 pixel, file size: 170 KB, MIME type: image/jpeg) These artists drawings depict two proposed models of the subsurface structure of the Jovian moon, Europa. ... Image File history File links Size of this preview: 437 × 600 pixel Image in higher resolution (1192 × 1636 pixel, file size: 170 KB, MIME type: image/jpeg) These artists drawings depict two proposed models of the subsurface structure of the Jovian moon, Europa. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Galileo is prepared for mating with the IUS booster Galileo being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... Voyager Project redirects here. ... Venusian arachnoid Chaos terrain (or chaotic terrain) is an astrogeological term used to denote planetary surface areas where features such as ridges, cracks, and plains appear jumbled and enmeshed with one another. ...


The best evidence for the so called "thick ice" model is a study of Europa's large craters. The largest craters are surrounded by concentric rings and appear to be filled with relatively flat, fresh ice; based on this and on the calculated amount of heat generated by Europan tides, it is predicted that the outer crust of solid ice is approximately 10–30 kilometers (5–20 mi) thick, including a ductile "warm ice" layer, which could mean that the liquid ocean underneath may be about 100 km (60–65 mi) deep.[17] This leads to a volume of Europa's oceans of 3×1018m³, slightly more than two times the volume of Earth's oceans.


The so called "thin ice" model is a conclusion of the formation of ridges and the flexure of the ice shell due to loading at the surface. With these models the crust of solid ice could be as thin as 200 meters. The "thin ice" model allows regular contact of the liquid interior with the surface through open ridges.[20]


The Galileo orbiter has also found that Europa has a weak magnetic field (about one quarter the strength of Ganymede's field and similar to Callisto's) which varies periodically as Europa passes through Jupiter's massive magnetic field. A likely explanation of this is that there is a large, subsurface ocean of liquid salt water.[13] Spectrographic evidence suggests that the dark reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within. Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically. In either case, since these materials are colorless or white when pure, some other material must also be present to account for the reddish color. Sulfur compounds are suspected. Galileo is prepared for mating with the IUS booster Galileo being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... Magnesium sulfate (or sulphate) is a chemical compound containing magnesium and sulfate, with the formula MgSO4. ... R-phrases S-phrases , , , Flash point Non-flammable Related Compounds Related strong acids Selenic acid Hydrochloric acid Nitric acid Related compounds Hydrogen sulfide Sulfurous acid Peroxymonosulfuric acid Sulfur trioxide Oleum Supplementary data page Structure and properties n, εr, etc. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ...


Atmosphere

Observations with the Goddard High Resolution Spectrograph of the Hubble Space Telescope, first described in 1995, revealed that Europa has a very tenuous atmosphere composed mostly of molecular oxygen (O2).[21][22] At 1 micropascal surface pressure, or 10−11 that of the Earth's atmosphere at sea level, the atmosphere would "fill only about a dozen Houston Astrodomes."[22] The Galileo spacecraft confirmed the presence of a very tenuous ionosphere (an upper atmospheric layer of charged particles) in 1997, supporting the initial deduction of an atmosphere; solar radiation and the energetic particles of Jupiter's magnetosphere are responsible for the ionized layer around Europa.[23][24] The Goddard High Resolution Spectrograph (GHRS or HRS) was a spectrograph installed on the Hubble Space Telescope. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... The Reliant Astrodome, formerly just the Astrodome, is a domed sports stadium in Houston, Texas, and is part of the Reliant Park complex. ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ...


Unlike the oxygen in Earth's atmosphere, Europa's is not of biological origin. The "surface-bounded atmosphere" forms through radiolysis, the dissocation of molecules through radiation. Solar ultraviolet radiation and charged particles (ions and electrons) from the Jovian magnetospheric environment collide with Europa's icy surface, splitting water into oxygen and hydrogen constituents; chemical components are adsorbed and "sputtered" into the atmosphere. The same radiation also creates collisional ejection of these products from the surface, and the balance of these two processes forms an atmosphere.[25] Molecular oxygen is the densest component of the atmosphere because it has a long lifetime; after returning to the surface from a ballistic arc, it does not stick (freeze) to the surface like a water molecule or hydrogen peroxide molecule, rather it desorbs from the surface and starts another ballistic arc. Molecular hydrogen also does not freeze onto the surface, but is so light that it easily escapes Europa's gravity. “Air” redirects here. ... Radiolysis is the dissociation of molecules by radiation. ... In chemistry, adsorption of a substance is its concentration on a particular surface. ...


Observations of the surface have revealed that some of the molecular oxygen produced by radiolysis is not ejected from the surface. Since the surface may interact with the subsurface ocean (based on the geological discussion above), this molecular oxygen may make its way to the ocean, where it could aid in biological processes.[26]


Exploration

Most human knowledge of Europa has been derived from a series of flybys since the 1970s. The sister craft Pioneer 10 and Pioneer 11 were the first to visit Jupiter, in 1973 and 1974, respectively; the first photos of Jupiter's largest moons produced by the Pioneers were fuzzy and dim.[14] The Voyager flybys followed in 1979, while the Galileo mission orbited Jupiter for eight years beginning in 1995 and provided the most detailed examination to date of the Galilean moons. Pioneer 10 was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. ... Position of Pioneer 10 and 11 Pioneer 11 was the second mission to investigate Jupiter and the outer solar system and the first to explore the planet Saturn and its main rings. ... Voyager Project redirects here. ... Galileo is prepared for mating with the IUS booster Galileo being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ...


Various proposals have been made for future missions. Any mission to Europa would need to be protected from the high radiation levels sustained by Jupiter.[5] The aims of these missions have ranged from examining Europa's chemical composition, to searching for extraterrestrial life in its sub-surface ocean.[27][28] This article is about Extraterrestrial life. ...


Possible extraterrestrial life

Life in such an ocean could possibly be similar to life on Earth's deep ocean

It has been suggested that life may exist in this under-ice ocean, perhaps subsisting in an environment similar to Earth's deep-ocean hydrothermal vents or the Antarctic Lake Vostok.[29] Life in such an ocean could possibly be similar to life on earth in the deep ocean.[27][30] So far, there is no evidence that life exists on Europa but due to the likely presence of liquid water, there are proposals to send a probe there.[31] Robert Pappalardo, an assistant professor within the University of Colorado's space department, said "We’ve spent quite a bit of time and effort trying to understand if Mars was once a habitable environment. Europa today, probably, is a habitable environment. We need to confirm this… but Europa, potentially, has all the ingredients for life… and not just four billion years ago… but today".[6] However, recent budget cuts have prevented proposed missions to search for life.[32] Colony of Pompeii worms: a worms feathery head can be seen poking out of its tube at bottom centre. ... Colony of Pompeii worms: a worms feathery head can be seen poking out of its tube at bottom centre. ... The deep ocean is the lowest layer in an ocean, existing below the thermocline. ... This article is about Extraterrestrial life. ... A hydrothermal vent A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. ... For other uses, see Antarctica (disambiguation). ... Lake Vostoks location within Antarctica (NASA) Lake Vostok is the largest of more than 70 subglacial lakes in Antarctica. ... This article is about the tv programme Life on Earth. ... The deep ocean is the lowest layer in an ocean, existing below the thermocline. ...


Spacecraft proposals and cancellations

Artist's concept of the cryobot and hydrobot
Artist's concept of the cryobot and hydrobot

The plan for the extremely ambitious Jupiter Icy Moons Orbiter was canceled in 2005.[32][5] The 2006 NASA budget includes Congressional language imploring NASA to fund a mission that would orbit Europa. Such a mission would be able to do the following: Image File history File links Cryobot. ... Image File history File links Cryobot. ... A cryobot or Philberth-probe is a robot designed to operate in or around water ice. ... Artistss Conception of Jupiter Icy Moons Orbiter The Jupiter Icy Moons Orbiter (JIMO) was a proposed spacecraft designed to explore the icy moons of Jupiter. ...

  1. Confirm a subsurface ocean using gravity and altimetry measurements
  2. Elucidate the origin of surface features by imaging much of the surface at high resolution
  3. Constrain the chemistry of surface materials using spectroscopy
  4. Probe for subsurface liquid water using ice-penetrating radar.[33]
  5. Carry a small lander to determine the surface chemistry directly, and to measure seismic waves, from which the level of activity and ice thickness could be determined.

However, at present it is far from certain that NASA will actually fund this mission, as funding for it is not included in NASA's 2007 budget plan.[5][6][34] Planetary scientist Ronald Greeley said about the Europa mission:[6]

"I am disappointed that after so many false starts over the last decade, it looks like a mission to Europa is slipping once again. The planetary community remains essentially unanimous in setting Europa as the highest priority large mission to the outer solar system"

Additionally, NASA Chief Mike Griffin said the following about the Jupiter Icy Moons Orbiter:[6]

"It was not a mission, in my judgment, that was well-formulated. [A scientific mission to Europa] is extremely interesting on a scientific basis. It remains a very high priority, and you may look forward, in the next year or so, or maybe even sooner, to a proposal for a Europa mission as part of our science line. But we would not -- we would, again, not -- favor linking that to a nuclear propulsion system."

Another possible mission, known as the "Ice Clipper" mission, would use an impactor similar to the Deep Impact DI mission -- it would make a controlled crash into the surface of Europa, generating a plume of debris which would then be collected by a small spacecraft flying through the plume.[35] Without the need for an insertion and relaunch of the spacecraft(s) from an orbit around Jupiter or Europa, this would be one of the least expensive missions since the necessary amount of fuel would be decreased.[36] Illustration of the Deep Impact space probe after impactor separation (artists conception) Deep Impact is a NASA space probe designed to study the composition of the interior of the comet Tempel 1. ...


More ambitious ideas have been put forward for a capable lander to test for evidence of life that might be frozen in the shallow subsurface, or even to directly explore the possible ocean beneath Europa's ice. One proposal calls for a large nuclear powered "Melt Probe" (cryobot) which would melt through the ice until it hit the ocean below.[37] The Planetary Society says that drilling a hole below the surface would be a main goal, and provide protection from radiation.[5] Once it reached the water, it would deploy an autonomous underwater vehicle (hydrobot), which would gather information and send it back to Earth.[38] Both the cryobot and the hydrobot would have to undergo some form of extreme sterilization to prevent it from detecting earth organisms instead of native life and to prevent contamination of the subsurface ocean.[39] This proposed mission has not yet reached a serious planning stage.[40] This article is about applications of nuclear fission reactors as power sources. ... A cryobot or Philberth-probe is a robot designed to operate in or around water ice. ... A cryobot or Philberth-probe is a robot designed to operate in or around water ice. ... Forward-contamination is the accidental contamination of other worlds with Earth microbes. ...


Even though Congress, the National Academy of Sciences, and the NASA advisory committee have all supported a mission to Europa, funding has still been halted.[41][42] The Planetary Society plans to create an "International Europa Task Force" to convince NASA and other space agencies to fund a Europa mission.[43][44] Other people, such as Congressman John Culberson, have also tried to go against NASA's budget cuts.[45][46] This article is in need of attention. ... John Abney Culberson (born August 24, 1956), American politician, has been the Republican congressman representing the Texas 7th congressional district (map) in the U.S. House of Representatives since 2001. ...


A "Solar System Exploration Roadmap" published for NASA by the Universities Space Research Association in 2006 placed exploration of Europa high on its list, and suggested that plans for a "flagship-class" mission to Europa begin by 2008 with hopes to launch by 2015.[47] USRA Logo The Universities Space Research Association was incorporated on March 12, 1969 in the District of Columbia as a private, nonprofit corporation under the auspices of the National Academy of Sciences (NAS). ...


See also

Galilean moons of Jupiter Jupiters extensive system of natural satellites – in particular the four large Galilean moons (Io, Europa, Ganymede and Callisto) – has been a common science fiction setting. ... The surface of Jupiters moon, Europa, is very young, geologically speaking, and as a result there are very few craters. ... This is a list of lineae on Europa. ... This is a list of named geological features on Europa. ... Jupiters outer moons and their highly inclined orbits. ... The Artemis Project designed a plan to colonize Europa. ...

References

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  2. ^ Using the mean radius
  3. ^ See Geissler et al. (1998) in orbit section for evidence of non-synchronous orbit.
  4. ^ Tritt, Charles S. (2002). Possibility of Life on Europa. Milwaukee School of Engineering. Retrieved on 2007-08-10.
  5. ^ a b c d e Friedman, Louis (December 14, 2005). Projects: Europa Mission Campaign; Campaign Update: 2007 Budget Proposal. The Planetary Society. Retrieved on 2007-08-10.
  6. ^ a b c d e David, Leondard (February 7, 2006). Europa Mission: Lost In NASA Budget. Space.com. Retrieved on 2007-08-10.
  7. ^ Satellites of Jupiter. The Galileo Project. Rice University (1995). Retrieved on 2007-08-09.
  8. ^ Simon Marius. Students for the Exploration and Development of Space. University of Arizona. Retrieved on 2007-08-09.
  9. ^ Marius, S.; (1614) Mundus Iovialis anno M.DC.IX Detectus Ope Perspicilli Belgici, where he attributes the suggestion to Johannes Kepler
  10. ^ a b Marazzini, C.; (2005); The names of the satellites of Jupiter: from Galileo to Simon Marius, Lettere Italiana, Vol. 57, No. 3, pp. 391-407
  11. ^ a b Europa, a Continuing Story of Discovery. Project Galileo. NASA, Jet Propulsion Laboratory. Retrieved on 2007-08-09.
  12. ^ Geissler, P. E.; Greenberg, R.; Hoppa, G.; Helfenstein, P.; McEwen, A.; Pappalardo, R.; Tufts, R.; Ockert-Bell, M.; Sullivan, R.; Greeley, R.; Belton, M. J. S.; Denk, T.; Clark, B. E.; Burns, J.; Veverka, J. (January 1998). "Evidence for non-synchronous rotation of Europa". Nature 391: 368. Retrieved on 2007-08-09. 
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  14. ^ a b Europa: Another Water World?. Project Galileo: Moons and Rings of Jupiter. NASA, Jet Propulsion Laboratory (2001). Retrieved on 2007-08-09.
  15. ^ Arnett, B.; Europa (November 7, 1996)
  16. ^ a b Hamilton, C. J.. Jupiter's Moon Europa.
  17. ^ a b Schenk, P. M.; Chapman, C. R.; Zahnle, K.; Moore, J. M.; Chapter 18: Ages and Interiors: the Cratering Record of the Galilean Satellites, in Jupiter: The Planet, Satellites and Magnetosphere, Cambridge University Press, 2004
  18. ^ Greenberg, R.; Europa: The Ocean Moon: Search for an Alien Biosphere, Springer Praxis Books, 2005
  19. ^ Greeley, R.; et al.; Chapter 15: Geology of Europa, in Jupiter: The Planet, Satellites and Magnetosphere, Cambridge University Press, 2004
  20. ^ a b Billings, S. E. (2005). "The great thickness debate: Ice shell thickness models for Europa and comparisons with estimates based on flexure at ridges". Icarus 177 (2): pp. 397-412. DOI:10.1016/j.icarus.2005.03.013. 
  21. ^ Hall, D. T.; et al.; Detection of an oxygen atmosphere on Jupiter's moon Europa, Nature, Vol. 373 (23 February 1995), pp. 677-679 (accessed 15 April 2006)
  22. ^ a b Savage, Donald; Jones, Tammy; Villard, Ray (February 23, 1995). Hubble Finds Oxygen Atmosphere on Europa. Project Galileo. NASA, Jet Propulsion Labratory. Retrieved on 2007-08-17.
  23. ^ Kliore, A. J.; Hinson, D. P.; Flasar, F. M.; Nagy, A. F.; Cravens, T. E. (July 1997). "The Ionosphere of Europa from Galileo Radio Occultations". Science 277 (5324): 355-358. DOI:10.1126/science.277.5324.355. Retrieved on 2007-08-10. 
  24. ^ Galileo Spacecraft Finds Europa has Atmosphere. Project Galileo. NASA, Jet Propulsion Laboratory (July 1997). Retrieved on 2007-08-10.
  25. ^ Shematovich, V. I.; Cooper, J. F.; Johnson, R. E. (April 2003). "Surface-bounded oxygen atmosphere of Europa". EGS - AGU - EUG Joint Assembly (Abstracts from the meeting held in Nice, France). Retrieved on 2007-08-10. 
  26. ^ Chyba and Hand, "Life without photosynthesis" [1]
  27. ^ a b Chandler, D. L. (20 October 2002). Thin ice opens lead for life on Europa. NewScientist.com.
  28. ^ Muir, H.; Europa has raw materials for life, NewScientist.com (22 May 2002)
  29. ^ Exotic Microbes Discovered near Lake Vostok, [email protected] (December 10, 1999)
  30. ^ Jones, N.; Bacterial explanation for Europa's rosy glow, NewScientist.com (11 December 2001)
  31. ^ Phillips, C.; Time for Europa, Space.com (28 September 2006)
  32. ^ a b Berger, B.; NASA 2006 Budget Presented: Hubble, Nuclear Initiative Suffer Space.com (7 February 2005)
  33. ^ Hibbitts, K.; and Mullen, L.; Hitting Europa Hard, Astrobiology Magazine (May 1, 2006)
  34. ^ Tony Reichhardt (2005). "Designs on Europa unfurl". Nature 437: 8. DOI:10.1038/437008a. 
  35. ^ Goodman, J.; Re: Galileo at Europa, MadSci Network forums, September 9, 1998
  36. ^ McKay C. P. (2002). "Planetary protection for a Europa surface sample return: The ice clipper mission". Advances in Space Research 30 (6): 1601-1605. 
  37. ^ Knight, W.; Ice-melting robot passes Arctic test, NewScientist.com (14 January 2002)
  38. ^ Bridges, A.; Latest Galileo Data Further Suggest Europa Has Liquid Ocean, Space.com (10 January 2000)
  39. ^ National Academy of Sciences Space Studies Board, Preventing the Forward Contamination of Europa, National Academy Press, Washington (DC), June 29, 2000
  40. ^ Powell, J.; Powell, J.; Maise, G.; and Paniagua, J. (July 2005). "NEMO: A mission to search for and return to Earth possible life forms on Europa". Acta Astronautica 57 (2–8): pp. 579-593. DOI:10.1016/j.actaastro.2005.04.003. 
  41. ^ NASA Budget Shuts Out Icy Moons Mission, SpaceDaily.com (February 08, 2006)
  42. ^ Berardelli, P.; AAS Pushing NASA To Rethink Its FY 2007 Budget, Space-Travel.com (May 5, 2006)
  43. ^ Projects: Europa Mission Campaign: Campaign Facts: International Europa Task Force, The Planetary Society
  44. ^ Projects: Europa Mission Campaign, The Planetary Society
  45. ^ David, L.; Lawmaker Campaigns Against NASA Budget Cuts, Space.com (16 March 2006)
  46. ^ Bourge, C.; Lawmakers steer NASA funding toward science mission, GovExec.com (July 31, 2006)
  47. ^ Solar System Exploration: This is the 2006 Solar System Exploration Roadmap for NASA's Science Mission Directorate. Universities Space Research Association (September 2006). Retrieved on September 29, 2006.

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External links

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S/2003 J 2 is a natural satellite of Jupiter. ... This is a list of the named rings of Jupiter. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... This article is about the Solar System. ... This article is about Earths moon. ... The relative sizes of and distance between Mars, Phobos, and Deimos, to scale. ... Jupiters outer moons and their highly inclined orbits. ... The Saturnian system (photographic montage) Saturn has 60 confirmed natural satellites, plus three hypothetical moons. ... Uranus has 27 known moons. ... Neptune (top) and Triton (bottom), 3 days after the Voyager 2 flyby. ... Image File history File links Download high resolution version (604x602, 23 KB)Cassini color image of Rhea taken Jan. ... The planet Pluto has three known moons. ... 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Atmosphere none Rhea (ree-a, Greek ‘Ρέα) is the second largest moon of Saturn and was discovered in 1672 by Giovanni Domenico Cassini. ... Atmospheric pressure 0 kPa Oberon (oe-bur-on) is the outermost of the major moons of the planet Uranus. ... Iapetus (eye-ap-É™-tÉ™s, IPA , Greek Ιαπετός) is the third-largest moon of Saturn, discovered by Giovanni Domenico Cassini in 1671. ... Charon (shair-É™n or kair-É™n (key), IPA , Greek Χάρων), discovered in 1978, is, depending on the definition employed, either the largest moon of Pluto or one member of a double dwarf planet with Pluto being the other member. ... Atmospheric pressure 0 kPa Umbriel (um-bree-É™l, IPA ) is a moon of Uranus discovered on 1851-10-24 by William Lassell. ... Atmospheric pressure 0 kPa Ariel (air-ee-É™l, IPA ) is a moon of Uranus discovered on 24 October 1851 by William Lassell. ... Atmosphere none Dione (dye-oe-nee, Greek Διώνη) is a moon of Saturn discovered by Giovanni Cassini in 1684. ... Atmosphere none Tethys (tee-thÉ™s or teth-É™s, IPA , Greek Τηθύς) is a moon of Saturn that was discovered by Giovanni Domenico Cassini in 1684. ... Atmosphere Surface pressure: trace, significant spatial variability[8][9] Composition: 91% Water vapour 4% Nitrogen 3. ... Miranda (IPA: ) is the smallest and innermost of Uranus five major moons. ... Atmospheric pressure 0 kPa Proteus (proe-tee-us, Greek Πρωτέας) is one of Neptunes moons. ... Mimas (mee-mÉ™s or mye-mÉ™s, IPA: , Greek Μίμᾱς, rarely Μίμανς) is a moon of Saturn that was discovered in 1789 by William Herschel. ... In astronomy, an inner satellite is a natural satellite following a prograde, low inclination orbit inwards of the large satellites of the parent planet. ... A Trojan moon is a natural satellite of a planet occupying the L4 or L5 equilateral Lagrangian points of a primary-moon system. ... 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The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ... The Kuiper belt, derived from data from the Minor Planet Center. ... The scattered disc (or scattered disk) is a distant region of our solar system, thinly populated by icy planetoids known as scattered disk objects (SDOs), a subset of the broader family of trans-Neptunian objects (TNOs). ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... Below is a list of solar system objects with diameter >500km: The Sun, a spectral class G2 star Mercury Venus Earth Moon Mars Jupiter Io Europa Ganymede Callisto complete list of Jupiters natural satellites Saturn Tethys Dione Rhea Titan Iapetus complete list of Saturns natural satellites Uranus Ariel... It has been suggested that Planetary-size comparison be merged into this article or section. ... This is a list of solar system objects by mass, in decreasing order. ...


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