NationMaster - Encyclopedia: Io (moon)

Io (eye'-oe, IPA: [ˈaɪoʊ], 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. Unlike most satellites in the outer Solar System (which have a thick coating of ice), Io is primarily composed of silicate rock surrounding a molten iron or iron-sulfide core. Io has one of the most geologically-active surfaces in the solar system, with over 400 active volcanoes.^[2] This extreme geologic activity is the result of tidal heating, with friction generated within Io's interior by Jupiter's varying pull on Io. Several of Io's volcanoes produce volcanic plumes of sulfur and sulfur dioxide that climb as high as 500 km (310 mi). Io's surface is also dotted with more than 100 mountains that have been uplifted by extensive compression at the base of Io's silicate crust. Some of these peaks are taller than Earth's Mount Everest.^[3] The majority of Io's surface is characterized by extensive plains coated with sulfur and sulfur dioxide frost. Image File history File links Download high-resolution version (2796x2796, 771 KB) Original Caption Released with Image: NASAs Galileo spacecraft acquired its highest resolution images of Jupiters moon Io on 3 July 1999 during its closest pass to Io since orbit insertion in late 1995. ... Galileo Galilei (15 February 1564 â€“ 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who is closely associated with the scientific revolution. ... January 7 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. ... 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For the common case of a homogeneous substance, it is expressed as: where, in SI units: Ï (rho) is the density of the substance, measured in kgÂ·m-3 m is the mass of the substance, measured in kg V is... 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 at any point on a velocity-time graph, it is given by the slope of the tangent to that point basicly. ... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ... 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. ... 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Io's volcanism is responsible for many of that satellite's unique features. Io's plumes and lava flows produce large surface changes, and paint the surface in various shades of red, yellow, white, black, and green, largely due to the sulfurous compounds. Numerous extensive lava flows, several longer than 500 km in length, also mark the surface. These volcanic processes have given rise to a comparison of the visual appearance of Io's surface to a pizza. The materials produced by this volcanism provide material for Io's thin, patchy atmosphere and Jupiter's extensive magnetosphere.

Io played a significant role in the development of astronomy in the 17th and 18th centuries. It was discovered, along with the other Galilean satellites, in 1610 by Galileo Galilei. This discovery furthered the adoption of the Copernican model of the Solar System, the development of Kepler's laws of motion, and the first measurement of the speed of light. From Earth, Io remained nothing more than a point of light until the late 19th and early 20th centuries, when it became possible to resolve its large-scale surface features, such as the dark red polar and bright equatorial regions. In 1979, the two Voyager spacecraft revealed Io to be a geologically active world, with numerous volcanic features, large mountains, and a young surface with no obvious impact craters. The Galileo spacecraft performed several close flybys in the 1990s and early 2000s, obtaining data about Io's interior structure and surface composition. These spacecraft also revealed the relationship between the satellite and Jupiter's magnetosphere and the existence of a belt of radiation centered on Io's orbit. The exploration of Io continued in the early months of 2007 with a distant flyby by Pluto-bound New Horizons. // Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ... Galileo Galilei (15 February 1564 â€“ 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who is closely associated with the scientific revolution. ... Heliocentric Solar System Heliocentrism (lower panel) in comparison to the geocentric model (upper panel) In astronomy, heliocentrism is the idea that the sun is at the center of the Universe and/or the Solar System. ... Johannes Kepler (December 27, 1571 â€“ November 15, 1630) was a German mathematician, astronomer and astrologer, and a key figure in the 17th century astronomical revolution. ... Also: 1979 by Smashing Pumpkins. ... Voyager Project redirects here. ... For the band, see 1990s (band). ... The 2000s are the current decade, spanning from 2000 to 2009. ... Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... New Horizons is a robotic spacecraft mission conducted by NASA. It is expected to be the first spacecraft to fly by and study the dwarf planet Pluto and its moons, Charon, Nix and Hydra. ...

1 Name
2 Observational history
3 Orbit
4 Interaction with Jupiter's magnetosphere
5 Structure
6 See also
7 References
8 External links

Name

See also: List of geological features on Io

See also: List of paterae on Io

See also: List of mountains on Io

While Simon Marius is not credited with the sole discovery of the Galilean satellites, his names for the moons have stuck. In his 1614 publication Mundus Jovialis, he named the innermost large moon of Jupiter after the Greek mythological figure Io, one of the many lovers of Zeus (who is also known as Jupiter in the Roman mythology).^[4] Marius' names fell out of favor, and were not revived in common use until the mid-20th century. In much of the earlier astronomical literature, Io is simply referred to by its Roman numeral designation (a system introduced by Galileo) as "Jupiter I", or simply as "the first satellite of Jupiter". The most common adjectival form of the name is Ionian. This is a list of named geological features on Io. ... This is a list of paterae on the surface of Io. ... Ios surface is covered in volcanoes and mountains. ... Simon Marius Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer. ... Events April 5 - In Virginia, Native American Pocahontas marries English colonist John Rolfe. ... The bust of Zeus found at Otricoli (Sala Rotonda, Museo Pio-Clementino, Vatican) Greek mythology is the body of stories belonging to the Ancient Greeks concerning their gods and heroes, the nature of the world and the origins and significance of their own cult and ritual practices. ... Jupiter and Io, Renaissance masterwork by Antonio da Correggio. ... The Statue of Zeus at Olympia Phidias created the 12-m (40-ft) tall statue of Zeus at Olympia about 435 BC. The statue was perhaps the most famous sculpture in Ancient Greece, imagined here in a 16th century engraving Zeus (in Greek: nominative: ZeÃºs, genitive: DiÃ³s), is... Jupiter et ThÃ©tis - by Jean Ingres, 1811. ... A head of Minerva found in the ruins of the Roman baths in Bath Roman mythology, the mythological beliefs of the people of Ancient Rome, can be considered as having two parts. ... The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. ...

Features on Io are named after characters and places from the Io myth, as well as deities of fire, volcanoes, the Sun, and thunder from various myths, and characters and places from Dante's Inferno, names which are appropriate to the volcanic nature of the surface.^[5] Since the surface was first seen up close by Voyager 1 the International Astronomical Union has approved 225 names for Io's volcanoes, mountains, plateaus, and large albedo features. The approved feature types used for Io include: Patera (volcanic depressions), Mons, Mensa, Planum, and Tholus (mountains, with morphologic characteristics, like size, shape, and height, determining the term used), Fluctus (lava flows), Vallis (lava channels), Regio (large-scale, albedo features), and Active eruptive centers (locations where plume activity was the first sign of volcanic activity at a particular volcano).^[5] Examples of named features include Prometheus, Pan Mensa, Tvashtar Paterae, and Tsũi Goab Fluctus.^[6] Look up Myth in Wiktionary, the free dictionary. ... DANTE is also a digital audio network. ... Dante shown holding a copy of The Divine Comedy, next to the entrance to Hell, the seven terraces of Mount Purgatory and the city of Florence, in Michelinos fresco. ... Trajectory of Voyager 1 using Celestia The Voyager 1 spacecraft is a 733-kilogram robotic space probe of the outer solar system and beyond, launched September 5, 1977, and is currently operational. ... Logo of the IAU The International Astronomical Union (French: Union astronomique internationale) unites national astronomical societies from around the world. ... Tvashtar Paterae. ...

Observational history

Galileo Galilei, the discoverer of Io

The first reported observation of Io was made by Galileo Galilei on 7 January 1610. The discovery of Io and the other Galilean satellites of Jupiter was published in Galileo's Siderius Nuncius in March 1610.^[7] In his Mundus Jovialis, published in 1614, Simon Marius claimed to have discovered Io and the other moons of Jupiter in 1609, one week before Galileo's discovery. Galileo doubted this claim and dismissed the work of Marius as plagiarism. Given that he also published his discovery before Marius, Galileo is credited with the discovery. ImageMetadata File history File links Galileo. ... ImageMetadata File history File links Galileo. ... Galileo Galilei (15 February 1564 â€“ 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who is closely associated with the scientific revolution. ... January 7 is the 7th day of the year in the Gregorian calendar. ... // Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ...

For the next two and a half centuries, Io remained an unresolved, 5^th-magnitude point of light in astronomers' telescopes. During the 17th century, Io and the other Galilean satellites served a variety of purposes, such as helping mariners determine their longitude,^[8] validating Kepler's Third Law of planetary motion, and determining the light time between Jupiter and Earth.^[7] Based on ephemerides produced by astronomer Giovanni Cassini and others, Pierre-Simon Laplace created a mathematical theory to explain the resonant orbits of Io, Europa, and Ganymede.^[7] This resonance was later found to have a profound effect on the geologies of the three moons. Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... An ephemeris (plural: ephemerides) (from the Greek word ephemeros = daily) was, traditionally, a table providing the positions (given in a Cartesian coordinate system, or in right ascension and declination or, for astrologers, in longitude along the zodiacal ecliptic), of the Sun, the Moon, the planets, asteroids or comets in the... Giovanni Domenico (Jean-Dominique) Cassini Giovanni Domenico Cassini (June 8, 1625 - September 14, 1712) was an Italian-French astronomer and engineer. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Apparent magnitude: 5. ... This article or section does not adequately cite its references or sources. ...

Improved telescope technology in the late 19th and 20th centuries allowed astronomers to resolve (that is, see) large-scale surface features on Io. In the 1890s, Edward E. Barnard was the first to observe variations in Io's brightness between its equatorial and polar regions, correctly determining that this was due to differences in color and albedo between the two regions and not due to Io being egg-shaped, as proposed at the time by fellow astronomer William Pickering, or two separate objects, as initially proposed by Barnard.^[9]^[10]^[11] Later telescopic observations confirmed Io's distinct reddish-brown polar regions and yellow-white equatorial band.^[12] Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ... The 1890s were sometimes referred to as the Mauve Decade, because William Henry Perkins aniline dye allowed the widespread use of that colour in fashion, and also as the Gay Nineties, under the then-current usage of the word gay which referred simply to merriment and frivolity, with no... Edward Emerson Barnard (December 16, 1857 – February 6, 1923) was an American astronomer. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... William Henry Pickering (February 15, 1858 – January 17, 1938) was an American astronomer, brother of Edward Charles Pickering. ...

Telescopic observations in the mid-20th century began to hint at Io's unusual nature. Spectroscopic observations suggested that Io's surface was devoid of water ice (a substance found to be plentiful on the other Galilean satellites).^[13] The same observations suggested a surface dominated by evaporates composed of sodium salts and sulfur.^[14] Radio telescopic observations revealed Io's influence on the Jovian magnetosphere, as demonstrated by decametric wavelength bursts tied to the orbital period of Io.^[15] General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Standard atomic weight 22. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ...

Pioneer

The first spacecraft to pass by Io were the twin Pioneer 10 and 11 probes on December 3, 1973 and December 2, 1974 respectively.^[16] Radio tracking provided an improved estimate of Io's mass, which, along with the best available information of Io's size, suggested that Io had the highest density of the four Galilean satellites, and was composed primarily of silicate rock rather than water ice.^[17] The Pioneers also revealed the presence of a thin atmosphere at Io and intense radiation belts near the orbit of Io. The camera on board Pioneer 11 took the only good image of Io obtained by either spacecraft, showing its north polar region.^[18] Close-up images were planned during Pioneer 10's encounter with Io, but those observations were lost due to the high-radiation environment.^[16] 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. ... is the 337th day of the year (338th in leap years) in the Gregorian calendar. ... Year 1973 (MCMLXXIII) was a common year starting on Monday (link will display full calendar) of the 1973 Gregorian calendar. ... December 2 is the 336th day of the year (337th in leap years) in the Gregorian calendar. ... 1974 (MCMLXXIV) was a common year starting on Tuesday. ...

Voyager

Mosaic of Voyager 1 images covering Io's South Polar Region

When the twin probes Voyager 1 and Voyager 2 passed by in 1979, their more advanced imaging system allowing for far more detailed images. Voyager 1 flew past the satellite on March 5, 1979 from a distance of 20,600 km (12,800 mi).^[19] The images returned during the approach revealed a strange, multi-colored landscape devoid of impact craters.^[20] The highest resolution images showed a relatively young surface punctuated by oddly-shaped pits, mountains taller than Mount Everest, and features resembling volcanic lava flows. Image File history File links Size of this preview: 464 Ã— 599 pixelsFull resolution (2175 Ã— 2810 pixel, file size: 291 KB, MIME type: image/jpeg) This Voyager 1 image mosaic shows Ios south polar region. ... Image File history File links Size of this preview: 464 Ã— 599 pixelsFull resolution (2175 Ã— 2810 pixel, file size: 291 KB, MIME type: image/jpeg) This Voyager 1 image mosaic shows Ios south polar region. ... Trajectory of Voyager 1 using Celestia The Voyager 1 spacecraft is a 733-kilogram robotic space probe of the outer solar system and beyond, launched September 5, 1977, and is currently operational. ... Trajectory of Voyager 1 using Celestia The Voyager 1 spacecraft is a 733-kilogram robotic space probe of the outer solar system and beyond, launched September 5, 1977, and is currently operational. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... This article is about the day. ... Also: 1979 by Smashing Pumpkins. ...

Shortly after the encounter, Voyager navigation engineer Linda A. Morabito noticed a "plume" emanating from the surface in one of the images.^[21] Analysis of other Voyager 1 images showed nine such plumes scattered across the surface, proving that Io was volcanically active.^[22] This conclusion was predicted in a paper published shortly before the Voyager 1 encounter by Stan J. Peale, Patrick Cassen, and R. T. Reynolds. The authors calculated that Io's interior must experience significant tidal heating caused by its orbital resonance with Europa and Ganymede (see the Tidal Heating section for a more detailed explanation of the process).^[23] Data from this flyby showed that the surface of Io is dominated by sulfur and sulfur dioxide frosts. These compounds also dominate its thin atmosphere and the torus of plasma centered on Io's orbit (also discovered by Voyager).^[24]^[25]^[26] Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ...

Voyager 2 passed Io on July 9, 1979 at a distance of 1,130,000 km (702,150 mi). Though it did not approach nearly as close as Voyager 1, comparisons between images taken by the two spacecraft showed several surface changes that had occurred in the five months between the encounters. In addition, observations of Io as a crescent as Voyager 2 departed the Jovian system revealed that eight of the nine plumes observed in March were still active in July 1979, with only the volcano Pele shutting down between flybys.^[27] is the 190th day of the year (191st in leap years) in the Gregorian calendar. ... Also: 1979 by Smashing Pumpkins. ... Color image of Ios trailing hemisphere, highlighting the large red ring around the volcano Pele Pele is a volcano on the surface of Jupiters moon Io. ...

Galileo

Galileo encounters with Io
Date	Distance (km)
December 7, 1995	897
November 4, 1996	244,000
March 29, 1998	252,000
June 30, 1999	127,000
October 11, 1999	611
November 26, 1999	301
February 22, 2000	198
August 6, 2001	194
October 16, 2001	184
January 17, 2002	102
November 7, 2002	45,800

To follow up on the discoveries of the two Voyager probes and ground-based observations taken in the intervening years, the Galileo spacecraft arrived at Jupiter in 1995 after a six-year journey from Earth. Io's location within one of Jupiter's most intense radiation belts precluded a prolonged close flyby, but Galileo did pass close by shortly before entering orbit for its two-year, primary mission studying the Jovian system. While no images were taken during the close flyby on December 7, 1995, the encounter did yield significant results, such as the discovery of a large iron core, similar to that found in the rocky planets of the inner solar system.^[28] is the 341st day of the year (342nd in leap years) in the Gregorian calendar. ... Year 1995 (MCMXCV) was a common year starting on Sunday (link will display full 1995 Gregorian calendar). ... is the 308th day of the year (309th in leap years) in the Gregorian calendar. ... Year 1996 (MCMXCVI) was a leap year starting on Monday (link will display full 1996 Gregorian calendar). ... March 29 is the 88th day of the year in the Gregorian calendar (89th in leap years). ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... is the 181st day of the year (182nd in leap years) in the Gregorian calendar. ... Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... October 11 is the 284th day of the year (285th in leap years) in the Gregorian calendar. ... Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... is the 330th day of the year (331st in leap years) in the Gregorian calendar. ... Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... is the 53rd day of the year in the Gregorian calendar. ... 2000 (MM) was a leap year starting on Saturday of the Gregorian calendar. ... is the 218th day of the year (219th in leap years) in the Gregorian calendar. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... October 16 is the 289th day of the year (290th in leap years). ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... January 17 is the 17th day of the year in the Gregorian calendar. ... For album titles with the same name, see 2002 (album). ... is the 311th day of the year (312th in leap years) in the Gregorian calendar. ... For album titles with the same name, see 2002 (album). ... 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. ... is the 341st day of the year (342nd in leap years) in the Gregorian calendar. ... Year 1995 (MCMXCV) was a common year starting on Sunday (link will display full 1995 Gregorian calendar). ...

Despite the lack of close-up imaging and mechanical problems that greatly restricted the amount of data returned, several significant discoveries were made during Galileo's primary mission. For example, Galileo observed the effects of a major eruption at Pillan Patera and confirmed that volcanic eruptions are composed of silicate magmas with magnesium-rich mafic and ultramafic compositions with sulfur and sulfur dioxide serving a similar role to water and carbon dioxide on Earth.^[29] Distant imaging of Io was acquired for almost every orbit during the primary mission, revealing large numbers of active volcanoes (both thermal emission from cooling magma on the surface and volcanic plumes), numerous mountains with widely varying morphologies, and several surface changes that had taken place both between the Voyager and Galileo eras and between Galileo orbits.^[30] In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms, and is in a gaseous state in the atmosphere of the Earth. ...

The Galileo Mission was twice extended, in 1997 and 2000. During these extended missions, the probe flew by Io three times in late 1999 and early 2000 and three times in late 2001 and early 2002. Observations during these encounters revealed the geologic processes occurring at Io's volcanoes and mountains, excluded the presence of a magnetic field, and demonstrated the extent of volcanic activity.^[30] In December 2000, the Cassini spacecraft had a distant and brief encounter with the Jupiter system en route to Saturn, allowing for joint observations with Galileo. These observations revealed a new plume at Tvashtar Paterae and provided insights into Io's aurorae.^[31] Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... Adjectives: Saturnian Atmosphere Surface pressure: 140 kPa Composition: >93% hydrogen >5% helium 0. ... Tvashtar Paterae. ...

Subsequent observations

Changes in surface features in the eight years between Galileo and New Horizons observations

Following Galileo’s fiery demise in Jupiter's atmosphere in September 2003, new observations of Io's volcanism came from Earth-based telescopes. In particular, adaptive optics imaging from the Keck telescope in Hawaii and imaging from the Hubble telescope have allowed astronomers to monitor Io's active volcanoes.^[32]^[33] This imaging has allowed scientists to monitor volcanic activity on Io, even without a spacecraft in the Jupiter system. The New Horizons spacecraft, en route to Pluto and the Kuiper Belt, flew by the Jupiter system and Io on February 28, 2007. During the encounter, numerous distant observations of Io were obtained. Early results include images of a large plume at Tvashtar, providing the first detailed observations of the largest class of Ionian volcanic plume since observations of Pele's plume in 1979.^[34] New Horizons also captured images of a volcano near Girru Patera in the early stages of an eruption, and several volcanic eruptions that have occurred since Galileo. The only forthcoming mission planned for the Jupiter system, Juno, does not have an imaging system powerful enough to perform Io surface science. Missions to Europa and Ganymede currently in the concept study phase may be able to study Io before starting their primary mission at their respective targets, but, as of 2007, they are at least a decade from arriving at Jupiter.^[35] Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ... Official language(s) English, Hawaiian Capital Honolulu Largest city Honolulu Area Ranked 43rd - Total 10,931 sq mi (29,311 kmÂ²) - Width n/a miles (n/a km) - Length 1,522 miles (2,450 km) - % water 41. ... New Horizons is a robotic spacecraft mission conducted by NASA. It is expected to be the first spacecraft to fly by and study the dwarf planet Pluto and its moons, Charon, Nix and Hydra. ... Adjectives: Plutonian Atmosphere Surface pressure: 0. ... The Kuiper belt, derived from data from the Minor Planet Center. ... February 28 is the 59th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... Juno at Jupiter Juno is a NASA mission to Jupiter planned to cost roughly $700 million and scheduled to launch by June 30, 2010. ...

Orbit

Animation showing Io's Laplace resonance with Europa and Ganymede

Io orbits Jupiter at a distance of 421,700 km (262,000 mi) from the planet's center and 350,000 km (217,000 mi) from its cloudtops. It is the innermost of the Galilean satellites of Jupiter, its orbit lying between those of Thebe and Europa. Including Jupiter's inner satellites, Io is the fifth moon out from Jupiter. It takes 42.5 hours to revolve once (fast enough for its motion to be observed over a single night of observation). Io is in a 2:1 mean motion orbital resonance with Europa and a 4:1 mean motion orbital resonance with Ganymede, completing two orbits of Jupiter for every one orbit completed by Europa, and four orbits for every one completed by Ganymede. This resonance helps maintain Io's orbital eccentricity (0.0041), which in turn provides the primary heating source for its geologic activity (see the Tidal Heating section for a more detailed explanation of the process).^[23] Without this forced eccentricity, Io's orbit would circularize through tidal dissipation, leading to a geological less active world. Like the other Galilean satellites of Jupiter and the Earth's Moon, Io rotates synchronously with its orbital period, keeping one face nearly pointed toward Jupiter. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Atmospheric pressure 0 kPa Thebe (thee-bee, IPA ; Greek Î˜Î®Î²Î·) is the fourth of Jupiters known moons by distance from the planet. ... Apparent magnitude: 5. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... This article or section does not adequately cite its references or sources. ... (This page refers to eccitricity in astrodynamics. ... Apparent magnitude: up to -12. ... Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...

Interaction with Jupiter's magnetosphere

Schematic of Jupiter's magnetosphere and the components influenced by Io (near the center of the image): the Plasma Torus (in red), the neutral cloud (in yellow), the flux tube (in green), and magnetic field lines (in blue).^[36]

Io plays a significant role in shaping the Jovian magnetic field. The magnetosphere of Jupiter sweeps up gases and dust from Io's thin atmosphere at a rate of 1 tonne per second.^[37] This material is mostly composed of ionized and atomic sulfur, oxygen and chlorine; atomic sodium and potassium; molecular sulfur dioxide and sulfur, and sodium chloride dust.^[37]^,^[38] These materials ultimately have their origin from Io's volcanic activity, but the material that escapes to Jupiter's magnetic field and into interplanetary space comes directly from Io's atmosphere. These materials, depending on their ionized state and composition, ultimately end up in various neutral (non-ionized) clouds and radiation belts in Jupiter's magnetosphere, and in some cases, are eventually ejected from the Jovian system. Image File history File links Size of this preview: 800 Ã— 600 pixelsFull resolution (1280 Ã— 960 pixel, file size: 426 KB, MIME type: image/jpeg) Schematic of the Jovian magnetosphere showing the Io Plasma Torus (in red), the Neutral Sodium immediately surrounding Io (in yellow), the Io flux tube (in green... Image File history File links Size of this preview: 800 Ã— 600 pixelsFull resolution (1280 Ã— 960 pixel, file size: 426 KB, MIME type: image/jpeg) Schematic of the Jovian magnetosphere showing the Io Plasma Torus (in red), the Neutral Sodium immediately surrounding Io (in yellow), the Io flux tube (in green... A tonne or metric ton (symbol t), sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. ... An electrostatic potential map of the nitrate ion (NO3âˆ’). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ... Jordanian and Israeli salt evaporation ponds at the south end of the Dead Sea Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the formula NaCl. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ...

Surrounding Io (up to a distance of 6 Io radii from the moon's surface) is a cloud of neutral sulfur, oxygen, sodium, and potassium atoms. These particles originate in Io's upper atmosphere but are excited from collisions with ions in the plasma torus (discussed below) and other processes into filling Io's Hill sphere, which is the region where moon's gravity is predominant over Jupiter. Some of this material escapes Io's gravitational pull, and goes into orbit around Jupiter. Over a 20-hour period, these particles form a banana-shaped neutral cloud that can reach as far as 6 Jovian radii from Io, either inside Io's orbit and ahead of the satellite or outside Io's orbit and behind the satellite.^[37] The collisional process that excites these particles also occasionally provides sodium ions in the plasma torus with an electron, removing those new "fast" neutrals from the torus. However, these particles still retain their velocity (70 km/s. compared to the 17 km/s. orbital velocity at Io), leading these particles to be ejected in jets leading away from Io.^[39] A plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation. ... A Hill sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbits. ...

Io orbits within a belt of intense radiation known as the Io Plasma Torus. The plasma in this donut-shaped ring of ionized sulfur, oxygen, sodium, and chlorine originates when neutral atoms in the "cloud" surrounding Io are ionized and carried along by the Jovian magnetosphere.^[37] Unlike the particles in the neutral cloud, these particles co-rotate with Jupiter's magnetosphere, revolving around Jupiter at 74 km/s. Like the rest of Jupiter's magnetic field, the plasma torus is tilted with respect to Jupiter's equator (and Io's orbital plane), meaning Io is at times below and at other times above the core of the plasma torus. As noted above, these ions' higher velocity and energy levels are partly responsible for the removal of neutral atoms and molecules from Io's atmosphere and more extended neutral cloud. The torus is composed of three sections: an outer, "warm" torus that resides just outside Io's orbit, a vertically extended region known as the "ribbon" composed of the neutral source region and cooling plasma at around Io's distance from Jupiter, and an inner, "cold" torus, composed of particles that are slowly spiraling in toward Jupiter.^[37] After residing an average of 40 days in the torus, particles in the "warm" torus escape and are partially responsible for Jupiter's unusually large magnetosphere, their outward pressure inflating it from within.^[40] Particles from Io, detected as variations in magnetospheric plasma, have been detected far into the long magnetotail by New Horizons. The plasma torus emits light at ultraviolet wavelengths, allowing researchers to monitor variations in the plasma torus. While such variations have not been definitively linked to variations in Io's volcanic activity (the ultimate source for material in the plasma torus), this link has been established in the neutral sodium cloud.^[41] A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... â€œUVâ€ redirects here. ...

During an encounter with Jupiter in 1992, the Ulysses spacecraft detected a stream of dust-sized particle being ejected from the Jupiter system.^[42] The dust in these discrete streams travel away from Jupiter at speeds upwards of several hundred kilometers per second, have an average size of 10 μm, and consist primarily of sodium chloride.^[43]^,^[38] Dust measurements by Galileo showed that these dust streams originate from Io, but the exact mechanism for how these form, whether from Io's volcanic activity or material removed from the surface, is currently unknown.^[44] Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... Ulysses spacecraft Ulysses is an unmanned probe designed to study the Sun at all latitudes. ...

Jupiter's magnetic field lines, which Io crosses, couples Io to Jupiter's polar upper atmosphere through the generation of an electric current known as the Io Flux Tube.^[37] This current produces an auroral glow in Jupiter's polar regions known as the Io footprint, as well as aurorae in Io's atmosphere. Particles from this auroral interaction act to darken the Jovian polar regions at visible wavelengths. The location of Io and its auroral footprint with respect to the Earth and Jupiter has a strong influence on the Jovian radio emissions from our vantage point: when Io is visible, radio signals from Jupiter increase considerably.^[37]^,^[15] The Juno mission, planned for the next decade, should help to shed light on these processes. Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges, such as those in electric currents and bar magnets. ... Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic flux. ... Electric current is the flow (movement) of electric charge. ...

Structure

Io is slightly larger than Earth's Moon. It has a mean radius of 1821.3 km (about five percent greater than the Moon's) and a mass of 89.3 Zg (about 21 percent greater than the Moon's). Among the Galilean satellites, in both mass and volume, Io ranks behind Ganymede and Callisto but ahead of Europa. Apparent magnitude: up to -12. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ... This article or section does not adequately cite its references or sources. ... There is also an asteroid named 204 Kallisto. ... Apparent magnitude: 5. ...

Interior

Model of the possible interior composition of Io with an inner, iron- or iron-sulfide core (in gray), an outer silicate crust (in brown), and a partially molten silicate mantle in between (in orange)

Composed primarily of silicate rock and iron, Io is closer in bulk composition to the terrestrial planets, than to other satellites in the outer solar system, which are mostly composed of a mix of water ice and silicates. Io has a density of 3.5275 grams per cubic centimeter, the highest of any moon in the Solar System, significantly higher than the other Galilean satellites, and higher than the Earth's moon.^[45] Models based on the Voyager and Galileo measurements of the moon's mass, radius, quadrupole gravitational coefficients suggest that its interior is differentiated, with an outer, silicate-rich crust and mantle, and an inner, iron- or iron sulfide-rich core.^[28] The metallic core makes up approximately 20% of Io's mass.^[46] Depending on the amount of sulfur in the core, the core has a radius between 350 and 650 km (220 to 400 mi) if it is composed almost entirely of iron, or between 550 and 900 km (310 to 560 mi) for a core consisting of a mix of iron and sulfur. Galileo's magnetometer failed to detect an internal magnetic field at Io, suggesting that the core is not convecting.^[47] Image File history File links Download high resolution version (2666x2000, 566 KB) Interior of Io original description: Cutaway view of the possible internal structure of Io The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft The interior characteristics are inferred from... Image File history File links Download high resolution version (2666x2000, 566 KB) Interior of Io original description: Cutaway view of the possible internal structure of Io The surface of the satellite is a mosaic of images obtained in 1979 by NASAs Voyager spacecraft The interior characteristics are inferred from... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... This balancing rock, Steamboat Rock stands in Garden of the Gods park in Colorado Springs, CO The rocky side of a mountain creek near OrosÃ, Costa Rica. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... This article is about the mineral Pyrite or Fools Gold. ... The planetary core consists of the innermost layers of a planet. ... A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument. ...

Modeling of Io's interior composition suggests that the mantle is composed of at least 75% of the magnesium-rich mineral forsterite, and has a bulk composition similar to that of L-chondrite and LL-chondrite meteorites, with higher iron content (compared to silicon) than the Moon or Earth, but lower than Mars.^[48]^,^[49] To support the heat flow observed on Io, 10-20% of Io's mantle may be molten, though regions where high-temperature volcanism has been observed may have higher melt fractions.^[50] The lithosphere of Io, composed of basalt and sulfur, deposited by Io's extensive volcanism, is at least 12 km (7½ mi) thick, but is likely to be less than 40 km (25 mi) thick.^[51]^[46] Forsterite (Mg2SiO4) is the magnesium rich end-member of the olivine solid-solution series. ... NWA 869, a L4-6 chondrite The L type ordinary chondrites are the second-most common type of meteorite, accounting for approximately 35% of all those catalogued, and 40% of the oridnary chondrites[1]. Their name comes from their relatively (L)ow iron abundance, with respect to the H chondrites... The LL type chondrites are the least abundant group of the ordinary chondrites, accounting for about 9% of the observed falls. ... Worlds second largest Meteorite in Culiacan, Mexico A meteorite is a relatively small extra-terrestrial body that reaches the Earths surface. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance as coarse powder, dark grey with bluish tinge Standard atomic weight 28. ... Apparent magnitude: up to -12. ... This article is about Earth as a planet. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... The tectonic plates of the Lithosphere on Earth. ...

Tidal Heating

Unlike the Earth and the Moon, Io's main source of internal heat comes from tidal dissipation rather than radioactive isotope decay, the result of Io's resonant orbit with Europa and Ganymede.^[23] Such heating is dependent on Io's distance from Jupiter, its orbital eccentricity, the composition of its interior, and its physical state.^[50] Its Laplace-resonant orbit with Europa and Ganymede maintains Io's eccentricity and prevents tidal dissipation within Io from circularizing its orbit. The resonant orbit also helps to maintain Io's distance from Jupiter; otherwise tides raised on Jupiter would cause Io to slowly spiral outward from its parent planet.^[52] The vertical differences in Io's tidal bulge, between the times Io is at its periapsis and apoapsis points along its orbit, could be as much as 100 m (330 ft). The friction or tidal dissipation produced in Io's interior due to this varying tidal pull, which without the resonant orbit would have gone into circularizing Io's orbit, instead, creates significant tidal heating within Io's interior, melting a significant amount of the moon's mantle and core. The amount of energy produced is up to 10 times greater than produced solely from radioactive decay. This heat is released in the form of volcanic activity, generating its observed high heat flow (global total: 0.6-1.6×10¹⁴ W).^[50] Models of its orbit suggest that the amount of tidal heating within Io changes with time, and that the current heat flow is not representative of the long-term average.^[50] Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Isotopes are any of the several different forms of an element each having different atomic mass (mass number). ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... 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. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ...

Color image of Io's trailing hemisphere, highlighting the large red ring around the volcano Pele

Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... Color image of Ios trailing hemisphere, highlighting the large red ring around the volcano Pele Pele is a volcano on the surface of Jupiters moon Io. ...

Surface

Based on their experience with the ancient surfaces of the Moon, Mars, and Mercury, scientists expected to see numerous impact craters in Voyager 1's first images of Io. The density of impact craters across Io's surface would have given clues to the moon's age. However, they were surprised to discover that the surface was almost completely lacking in impact craters, but was instead covered in smooth plains dotted with tall mountains, pits of various shapes and sizes, and volcanic lava flows. Compared to most worlds observed to that point, Io's surface was covered in a variety of colorful materials (leading Io to be compared to a rotten orange or to pizza) from various sulfurous compounds. The lack of impact craters indicated that Io's surface is geologically young, like the terrestrial surface, with volcanic materials continuously burying craters as they are produced. This result was spectacularly confirmed as at least nine active volcanoes were observed by Voyager 1. Tycho crater on Earths moon. ... Binomial name (L.) Osbeck Orangeâ€”specifically, sweet orangeâ€”refers to the citrus tree Citrus sinensis (syn. ... For other uses, see Pizza (disambiguation). ...

In addition to volcanoes, Io's surface includes non-volcanic mountains, numerous lakes of molten sulfur, calderas up to several kilometers deep, and extensive flows of low-viscosity fluid (possibly some form of molten sulfur or silicate) which stretch for hundreds of kilometers.^[53] Satellite image of Santorini. ...

Surface composition

Io's colorful appearance is the result of various materials produced by its extensive volcanism. These materials include silicates (such as orthopyroxene), sulfur, and sulfur dioxide.^[54] Sulfur-dioxide frost is ubiquitous across the surface of Io, forming large regions covered in white or grey materials. Sulfur is also seen in many places across the satellite, forming yellow to yellow-green regions. Sulfur deposited in the mid-latitude and polar regions is often radiation damaged, breaking up normally stable 8-chain sulfur. This radiation damage produces Io's red-brown polar regions.^[9] In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ...

Explosive volcanism, often taking the form of umbrella-shaped plumes, paints the surface with sulfurous and silicate materials. Plume deposits on Io are often colored red or white depending on the amount of sulfur and sulfur dioxide in the plume. Generally, plumes formed at volcanic vents from degassing lava contain a greater amount of S₂, producing a red "fan" deposit, or in extreme cases, large (often reaching beyond 450 km (280 mi) from the central vent) red rings.^[55] A prominent example of a red ring plume deposit is located at Pele. These red deposits consist primarily of sulfur (generally 3- and 4-chain molecular sulfur), sulfur dioxide, and perhaps Cl₂SO₂.^[54] Plumes formed at the margins of silicate lava flows (through the interaction of lava and pre-existing deposits of sulfur and sulfur dioxide), produce white or gray deposits. Volcanism on Io produces extensive lava flows, hundreds of volcanic pits, and plumes of sulfur and sulfur dioxide hundreds of kilometers in height on this satellite of Jupiter. ...

Compositional mapping and Io's high density suggest that Io contains little to no water, though small pockets of water ice or hydrated minerals have been tentatively identified, most notably on the northwest flank of the mountain Gish Bar Mons.^[56] This lack of water is likely due to Jupiter being hot enough early in the evolution of the solar system to drive off volatile materials like water in the vicinity of Io, but not hot enough to do so farther out. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral. ... The theories concerning the formation and evolution of the Solar System are complex and varied, interweaving various scientific disciplines, from astronomy and physics to geology and planetary science. ... Volatiles are that group of compounds with low boiling points (see volatile) that are associated with a planets or moons crust and/or atmosphere. ...

Volcanism

Main article: Volcanism on Io