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Encyclopedia > Ganymede (moon)
Ganymede
True-color image taken by the Galileo probe
Discovery
Discovered by G. Galilei
S. Marius
Discovery date January 11, 1610
Periapsis 1,069,200 km[b]
Apoapsis 1,071,600 km[a]
Eccentricity 0.0013[1]
Orbital period 7.15455296 d[1]
Average orbital speed 10.880 km/s
Inclination 0.20° (to Jupiter's equator)[1]
Satellite of Jupiter
Physical characteristics
Mean radius 2,634.1 ± 0.3 km (0.413 Earths)[2]
Surface area 87.0 million km2 (0.171 Earths)[c]
Volume 7.6×1010 km3 (0.0704 Earths)[d]
Mass 1.4819×1023 kg (0.025 Earths)[2]
Mean density 1.936 g/cm3[2]
Equatorial surface gravity 1.428 m/s2 (0.146 g)[e]
Escape velocity 2.741 km/s[f]
Rotation period synchronous
Axial tilt 0–0.33°[3]
Albedo 0.43 ± 0.02[4]
Surface temp.
K
min mean max
70[5] 110[5] 152[6]
Apparent magnitude 4.61 (opposition) [4]
Atmosphere
Surface pressure trace
Composition oxygen[7]

Ganymede is composed primarily of silicate rock and water ice. It is a fully differentiated body with an iron-rich, liquid core. A saltwater ocean is believed to exist nearly 200 km below Ganymede's surface, sandwiched between layers of ice.[10] Its surface comprises two main types of terrain. Dark regions, saturated with impact craters and dated to four billion years ago, cover about a third of the satellite. Lighter regions, crosscut by extensive grooves and ridges and only slightly less ancient, cover the remainder. The cause of the light terrain's disrupted geology is not fully known, but was likely the result of tectonic activity brought about by tidal heating.[2] In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... In cosmogony, planetary differentiation is a process by which the denser portions of a planet will sink to the center; while less dense materials rise to the surface. ... KM, Km, or km may stand for: Khmer language (ISO 639 alpha-2, km) Kilometre Kinemantra Meditation Knowledge management KM programming language KM Culture, Korean Movie Maker. ... Tycho crater on Earths moon. ... ... 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. ...

Ganymede is the only satellite in the Solar System known to possess a magnetosphere, likely created through convection within the liquid iron core.[11] The meager magnetosphere is buried within Jupiter's much larger magnetic field and connected to it through open field lines. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3 (ozone).[7] Atomic hydrogen is a minor atmospheric constituent. Whether the satellite has an ionosphere to correspond to its atmosphere is unresolved.[12] A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... For the indie-pop band, see The Magnetic Fields. ... Equipotential surfaces are surfaces of constant scalar potential. ... This article is about the chemical element and its most stable form, or dioxygen. ... For other uses, see Atmosphere (disambiguation). ... For other uses, see Ozone (disambiguation). ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ...

Ganymede's discovery is credited to Galileo Galilei, who observed it in 1610.[13] The satellite's name was soon suggested by astronomer Simon Marius, for the mythological Ganymede, cupbearer of the Greek gods and Zeus's beloved.[14] Beginning with Pioneer 10, spacecraft have been able to examine Ganymede closely.[15] The Voyager probes refined measurements of its size, while the Galileo craft discovered its underground ocean and magnetic field. The Jupiter Icy Moons Orbiter was meant to orbit Ganymede, but the NASA project was cancelled in 2005.[16] Galileo redirects here. ... Simon Marius Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer. ... In Greek mythology, Ganymede (Greek: Γανυμήδης, Ganumêdês)) was a divine hero whose homeland was the Troad. ... 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. ... For other uses, see Zeus (disambiguation). ... Pioneer 10 was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. ... Voyager Project redirects here. ... 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. ... For other uses, see NASA (disambiguation). ...

On January 7, 1610, Galileo Galilei observed what he believed were three stars near Jupiter; the next night he noticed that they had moved. He found a fourth supposed star, which would turn out to be Ganymede, on January 11. By January 15, Galileo came to the conclusion that the stars were actually bodies orbiting Jupiter.[17] He claimed the right to name the moons; he considered "Cosmian Stars" and settled on "Medicean Stars".[14] is the 7th day of the year in the Gregorian calendar. ... // Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ... is the 11th day of the year in the Gregorian calendar. ... is the 15th day of the year in the Gregorian calendar. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ...

The French astronomer Nicolas-Claude Fabri de Peiresc suggested individual names from the Medici family for the moons, but his proposal was not taken up.[14] Simon Marius, who had originally claimed to have found the Galilean satellites,[18] tried to name the moons the "Saturn of Jupiter", the "Jupiter of Jupiter" (this was Ganymede), the "Venus of Jupiter", and the "Mercury of Jupiter", another nomenclature that never caught on. From a suggestion by Johannes Kepler, Marius once again tried to name the moons:[14] Nicolas-Claude Fabri de Peiresc (December 1, 1580 â€“ June 24, 1637) was a French astronomer and savant who maintained a wide correspondence with scientists and was a successful organizer of scientific inquiry, whose own researches were not confined to the matter of determining the difference in longitude of various locations... For the board game, see Medici (board game). ... Simon Marius Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer. ... Kepler redirects here. ...

 “ …Then there was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell … the Third, on account of its majesty of light, Ganymede …[17] ”

This name and those of the other Galilean satellites fell into disfavor for a considerable time, and were not in common use until the mid-20th century. In much of the earlier astronomical literature, Ganymede is referred to instead by its Roman numeral designation (a system introduced by Galileo) as Jupiter III or as the "third satellite of Jupiter". Following the discovery of moons of Saturn, a naming system based on that of Kepler and Marius was used for Jupiter’s moons.[14] Ganymede is the only Galilean moon of Jupiter named after a male figure.

## Orbit and rotation

Ganymede orbits Jupiter at a distance of 1,070,400 km, third among the Galilean satellites,[8] and completes a revolution every seven days and three hours. Like most known moons, Ganymede is tidally locked, with one face always pointing toward the planet.[19] Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. The ranges of change are 0.0009–0.0022 and 0.05–0.32°, respectively.[20] These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0 and 0.33°.[3] Two bodies with a slight difference in mass orbiting around a common barycenter. ... Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ... World map showing the equator in red In tourist areas, the equator is often marked on the sides of roads The equator marked as it crosses IlhÃ©u das Rolas, in SÃ£o TomÃ© and PrÃ­ncipe. ... (This page refers to eccitricity in astrodynamics. ... For the science fiction novella by William Shunn, see Inclination (novella). ... In mathematics, almost periodicity is a property of dynamical systems that appear to retrace their paths through phase space, but not exactly. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ... In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ...

The Laplace resonances of Ganymede, Europa, and Io

The current Laplace resonance is unable to pump the orbital eccentricity of Ganymede to a higher value.[22] The value of about 0.0013 is probably a remnant from a previous epoch, when such pumping was possible.[21] The ganymedian orbital eccentricity is somewhat puzzling; if it is not pumped now it should have decayed long ago due to the tidal dissipation in the interior of Ganymede.[22] This means that the last episode of the eccentricity excitation happened only several hundred million years ago.[22] Because the orbital eccentricity of Ganymede is relatively low—0.0015 on average[21]—the tidal heating of this moon is negligible now.[22] However, in the past Ganymede may have passed through one or more Laplace-like resonances[j] which were able to pump the orbital eccentricity to a value as high as 0.01–0.02.[2][22] This probably caused a significant tidal heating of the interior of Ganymede; the formation of the grooved terrain may be a result of one or more heating episodes.[2][22] A wave that loses amplitude is said to dissipate. ... 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. ...

The origin of the Laplace resonance among Io, Europa, and Ganymede is not known. Two hypotheses exist: that it is primordial and has existed from the beginning of the Solar System;[23] or that it developed after the formation of the Solar System. A possible sequence of the events is as follows: Io raised tides on Jupiter, causing its orbit to expand until it encountered 2:1 resonance with Europa; after that the expansion continued, but some of the angular moment was transferred to Europa as the resonance caused its orbit to expand as well; the process continued until Europa encountered 2:1 resonance with Ganymede.[22] Eventually the drift rates of conjunctions between all three moons were synchronized and locked in the Laplace resonance.[22] Primordial elements are chemical elements found on the earth that have existed in their current form since before the earth was formed, according to the big bang theory. ... 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. ... It has been suggested that this article or section be merged with torque. ...

## Physical characteristics

### Composition

Interior of Ganymede

Ganymede's surface has an albedo of about 43%.[26] Water ice seems to be ubiquitous on the surface, with a mass fraction of 50–90%,[2] significantly more than in Ganymede as a whole. Near-infrared spectroscopy has revealed the presence of strong water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 μm.[26] The grooved terrain is brighter and has more icy composition than the dark terrain.[27] The analysis of high-resolution, near-infrared and UV spectra obtained by the Galileo spacecraft and from the ground has revealed various non-water materials: carbon dioxide, sulfur dioxide and, possibly, cyanogen, hydrogen sulfate and various organic compounds.[2][28] Galileo results have also shown magnesium sulfate (MgSO4) and, possibly, sodium sulfate (Na2SO4) on Ganymede's surface.[19][29] These salts may originate from the subsurface ocean.[29] For other uses, see Albedo (disambiguation). ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... Animation of the dispersion of light as it travels through a triangular prism. ... An absorption band is a range of wavelengths (or, equivalently, frequencies) in the electromagnetic spectrum within which electromagnetic energy is absorbed by a substance. ... A micrometre (American spelling: micrometer, symbol Âµm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... 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. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Cyanogen is the chemical compound with the formula (CN)2. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. ... Magnesium sulfate (or sulphate) is a chemical compound containing magnesium and sulfate, with the formula MgSO4. ... Sodium sulfate is an important compound of sodium. ...

The ganymedian surface is asymmetric; the leading hemisphere—that facing the direction of the orbital motion[g]—is brighter than the trailing one.[26] This is similar to Europa, but the reverse is true on Callisto.[26] The trailing hemisphere of Ganymede appears to be enriched in sulfur dioxide.[30][31] The distribution of carbon dioxide does not demonstrate any hemispheric asymmetry, although it is not observed near the poles.[28][32] Impact craters on Ganymede (except one) do not show any enrichment in carbon dioxide, which also distinguishes it from Callisto. Ganymede's carbon dioxide levels were probably depleted in the past.[32] Tycho crater on Earths moon. ...

### Internal structure

A sharp boundary divides the dark Nicholson Regio from the bright Harpagia Sulcus.

Ganymede appears to be fully differentiated, consisting of an iron sulfateiron core, silicate mantle and an outer ice mantle.[33][2] This model is supported by the low value of its dimensionless[h] moment of inertia0.3105 ± 0.0028—which was measured during Galileo flybys.[33][2] In fact, Ganymede has the lowest moment of inertia among the solid solar system bodies. The existence of a liquid, iron-rich core provides a natural explanation for the intrinsic magnetic field of Ganymede detected by Galileo.[34] The convection in the liquid iron, which has high electrical conductivity, is the most reasonable model of magnetic field generation.[11] Download high resolution version (1476x677, 255 KB)Boundary betwen dark and light terrain on Ganymede Original NASA caption: The ancient, dark terrain of Nicholson Regio (left) shows many large impact craters, and zones of fractures oriented generally parallel to the boundary between the dark and bright regions of Jupiters... Download high resolution version (1476x677, 255 KB)Boundary betwen dark and light terrain on Ganymede Original NASA caption: The ancient, dark terrain of Nicholson Regio (left) shows many large impact craters, and zones of fractures oriented generally parallel to the boundary between the dark and bright regions of Jupiters... Iron(II) sulfate, also known as ferrous sulfate and as copperas (FeSO4) is an example of an ionic compound. ... 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. ... Earth cutaway from core to exosphere. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Earth cutaway from core to exosphere. ... Moment of inertia, also called mass moment of inertia and, sometimes, the angular mass, (SI units kg m2, Former British units slug ft2), is the rotational analog of mass. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... Not to be confused with electrical conductance, a measure of an objects or circuits ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. ...

The precise thicknesses of the different layers in the interior of Ganymede depend on the assumed composition of silicates (fraction of olivine and pyroxene) and amount of sulfur in the core.[24][33] The most probable values are 700–900 km for the core radius and 800–1,000 km for the thickness of the outer ice mantle, with the remainder being made by the silicate mantle.[34][33][35][36] The density of the core is 5.5–6 g/cm3 and the silicate mantle is 3.4–3.6 g/cm3.[34][33][35][24] Some models of the magnetic field generation require the existence of a solid core made of pure iron inside the liquid Fe–FeS core—similar to the structure of the Earth's core. The radius of this core may be up to 500 km.[34] The temperature in the core of Ganymede is probably 1,500–1,700 K and pressure up to 100 kBar (10 Gpa).[33][34] The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... This article is about the chemical element. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... For other uses, see Pascal. ...

#### Subsurface ocean

Mass anomalies within Ganymede

The discovery of the induced magnetic moment of Ganymede in 2000 confirmed that it has a saltwater ocean in its interior (see Magnetosphere).[11][10][37] A subsurface ocean is also present in the other icy Galilean moons, Europa and Callisto. The existence of the oceans is connected with the anomalous behavior of the ice I melting temperature—it decreases with pressure reaching as low as 251 K at 2,070 bar (207 Mpa), which is the water–ice I–ice III triple point.[24][25] At higher pressures the stable solid phase is ice III and the melting temperature starts to increase.[24] The maximum possible thickness of the solid crust (lid) overlaying the ganymedian ocean is 146 km, which corresponds to the pressure of 2,070 bar.[38] However, the lid is probably somewhat thinner—closer to 100 km.[39] In this case the depth of the ocean is around 230 km.[25] The existence of the ocean can be made more likely if an antifreeze is dissolved in the water. The best candidates are ammonia and various salts like sulfates and chlorides.[25] Ammonia, for instance, can depress the melting temperature to as low as 175 K.[25] A bar magnet. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ... In physics, melting is the process of heating a solid substance to a point (called the melting point) where it turns into a liquid. ... A tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... World geologic provinces (USGS) Oceanic crust  0-20 Ma  20-65 Ma  >65 Ma Geologic province  Shield  Platform  Orogen  Basin  Large igneous province  Extended crust In geology, a crust is the outermost solid shell of a planet or moon. ... For other uses, see Antifreeze (disambiguation). ... For other uses, see Ammonia (disambiguation). ... The sulfate anion, SO42âˆ’ The structure and bonding of the sulfate ion In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... The chloride ion is formed when the element chlorine picks up one electron to form an anion (negatively-charged ion) Clâˆ’. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. ...

In many respects the ganymedian ocean is similar to that of Callisto.[25] There are important differences with Europa, however. Europa's ocean is much closer to the surface and is in direct contact with hydrothermal systems on its seafloor. Ganymede's ocean, deeper and sandwiched between layers of ice, has thus been seen as a less likely location for extraterrestrial life. Research suggests that interior magmatic activity might still generate pockets of water melt that would supply the ocean with nutrients, possibly sustaining a biosphere.[38] Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ... For other uses, see Biosphere (disambiguation). ...

The detailed analysis of Galileo's trajectory during its closest flyby (G2, at a minimum distance of 264 km) revealed a few mass anomalies in the interior of Ganymede. The data can be fitted with two or three point-like masses located near the surface or near the ice–rock boundary. The locations are not correlated with any surface features and their origin is not known.[40]

### Surface features

Voyager 2 image mosaic of Ganymede's anti-Jovian hemisphere. The ancient dark area of Galileo Regio lies at the upper right. It is separated from the smaller dark region of Marius Regio to its left by the brighter and younger band of Uruk Sulcus. Fresh ice ejected from the relatively recent Osiris Crater created the bright rays at the bottom.

The ganymedian surface is a mix of two types of terrain: very old, highly cratered, dark regions and somewhat younger (but still ancient), lighter regions marked with an extensive array of grooves and ridges. The dark terrain, which comprises about one-third of the surface,[41] contains clays and organic materials that could indicate the composition of the impactors from which Jovian satellites accreted.[42] Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... Tycho crater on Earths moon. ...

The heating mechanism required for the formation of the grooved terrain on Ganymede is an unsolved problem in the planetary sciences. The modern view is that the grooved terrain is mainly tectonic in nature.[2] Cryovulcanism is thought to have played only a minor role, if any.[2] The forces that caused the strong stresses in the ganymedian ice lithosphere necessary to initiate the tectonic activity may be connected to the tidal heating events in the past, possibly caused when the satellite passed through unstable orbital resonances.[2][43] The tidal flexing of the ice may have heated the interior and strained the lithosphere, leading to the development of cracks and horst and graben faulting, which erased the old, dark terrain on 70% of the surface.[44][2] The formation of the grooved terrain may also be connected with the early core formation. During subsequent evolution deep, hot water plumes may have risen from the core to the surface, leading to the tectonic deformation of the lithosphere.[38] Radiogenic heating within the satellite is the most relevant current heat source, contributing, for instance, to thickness of the ocean. Research models have found that if the orbital eccentricity were an order of magnitude greater than current (as it may have been in the past), tidal heating would be a more substantial heat source than radiogenic heating.[45] Planetary science, also known as planetology or planetary astronomy, is the science of planets and the solar system, and incorporates an interdisciplinary approach drawing from diverse sciences. ... ... The tectonic plates of the lithosphere on Earth. ... 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. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Horst and Graben are geological terms referring to regions that lie between normal faults and are either above or lower than the area beyond the faults. ... Plume of the Space Shuttle Atlantis after launch. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ...

Fresh impact craters on the grooved terrain of Ganymede

Cratering is seen on both types of terrain, but is especially extensive on the dark terrain: it appears to be saturated with impact craters and has evolved largely through impact events.[2] The brighter, grooved terrain contains much fewer impact features, which have been only of a minor importance to its tectonic evolution.[2] The density of cratering indicates an age of 4 billion years for the dark terrain, similar to the highlands of the Moon, and a somewhat younger age for the grooved terrain (but how much younger is uncertain).[46] Ganymede may have experienced a period of heavy cratering 3.5 to 4 billion years ago similar to that of the Moon.[46] If true, the vast majority of impacts happened in that epoch, while the cratering rate has been much smaller since.[9] Craters both overlay and are crosscut by the groove systems, indicating that some of the grooves are quite ancient. Relatively young craters with rays of ejecta are also visible.[47][9] Ganymedian craters are flatter than those on the Moon and Mercury. This is probably due to the relatively weak nature of Ganymede's icy crust, which can (or could) flow and thereby soften the relief. Ancient craters whose relief has disappeared leaving only a "ghost" of a crater are known as palimpsests.[9] This article is about Earths moon. ... A palimpsest is a manuscript page, scroll, or book that has been written on, scraped off, and used again. ...

One significant feature on Ganymede is a dark plain named Galileo Regio, which contains a series of concentric grooves, or furrows, likely created during a period of geologic activity.[48] Another prominent feature on Ganymede are polar caps, likely composed of water frost. The frost extends to 40° latitude.[19] These polar caps were first seen by the Voyager spacecraft. Theories on the caps' formation include the migration of water to higher latitudes and bombardment by plasma of the ice. Data from Galileo suggests the latter is correct.[49] Voyager Project redirects here. ...

### Atmosphere and ionosphere

In 1972, a team of Indian, British and American astronomers working at Indonesia's Bosscha Observatory claimed that they had detected a thin atmosphere around the satellite during an occultation, when it and Jupiter passed in front of a star.[50] They estimated that the surface pressure was around 1 μBar (0.1 Pa).[50] However, in 1979 Voyager 1 observed an occultation of a star (κ Centauri) during its flyby of the planet, with differing results.[51] The occultation measurements were conducted in the far-ultraviolet spectrum with wavelength shorter than 200 nm; they were much more sensitive to the presence of gases than measurements in the visible spectrum in 1972. No atmosphere was revealed by the Voyager data. The upper limit on the surface particle number density was found to be 1.5×109 cm−3, which corresponds to a surface pressure of less than 2.5×10−5 μBar.[51] The latter value is almost five orders of magnitude less than that measured in 1972, indicating that the earlier interpretation was too optimistic.[51] Bosscha Observatory is the oldest observatory in Indonesia. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... For other uses, see Pascal. ... For the album by The Verve, see Voyager 1 (album). ... Kappa Centauri (Îº Cen / Îº Centauri) is a binary star in the constellation Centaurus. ... For other uses, see Wavelength (disambiguation). ... A nanometre (American spelling: nanometer, symbol nm) (Greek: Î½Î¬Î½Î¿Ï‚, nanos, dwarf; Î¼ÎµÏ„ÏÏŽ, metrÏŒ, count) is a unit of length in the metric system, equal to one billionth of a metre (or one millionth of a millimetre), which is the current SI base unit of length. ... Visible light redirects here. ... The number density, in physics, refers to the number of entities (often of particles, but it could be of sound waves, galaxies, etc. ...

False color temperature map of Ganymede

The existence of a neutral atmosphere implies that an ionosphere should exist, because oxygen molecules are ionized by the impacts of the energetic electrons coming from the magnetosphere[55] and by solar EUV radiation.[12] However, the nature of the ganymedian ionosphere is as controversial as the nature of the atmosphere. Some Galileo measurements found an elevated electron density near the moon, suggesting an ionosphere, while others failed to detect anything.[12] The electron density near the surface is estimated by different sources to lie in the range 400–2,500 cm−3.[12] As of 2008, the parameters of the ionosphere of Ganymede are not well constrained. Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... For other uses, see Electron (disambiguation). ... For other uses, see Ultraviolet (disambiguation). ...

Additional evidence of the oxygen atmosphere comes from spectral detection of gases trapped in the ice at the surface of Ganymede. The detection of ozone (O3) bands was announced in 1996.[56] In 1997 spectroscopic analysis revealed the dimer (or diatomic) absorption features of the molecular oxygen. Such an absorption can arise only if the oxygen is in a dense phase. The best candidate is the molecular oxygen trapped in ice. The depth of the dimer absorption bands depends on latitude and longitude, rather than on surface albedo—they tend to decrease with increasing latitude on Ganymede, while the O3 shows an opposite effect.[57] Laboratory work has found that O2 would not cluster and bubble but dissolve in ice at Ganymede's relatively warm surface temperature of 100 K.[58] For other uses, see Ozone (disambiguation). ... Sucrose, or common table sugar, is composed of glucose and fructose. ... A computer rendering of the Nitrogen Molecule, which is a diatomic molecule. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ... This article is about the geographical term. ... Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation. ... For other uses, see Albedo (disambiguation). ...

A search for sodium in the atmosphere, just after such a finding on Europa, turned up nothing in 1997. Sodium is at least 13 times less abundant around Ganymede than around Europa, possibly because of a relative deficiency at the surface or because the magnetosphere fends off energetic particles.[59] Another minor constituent of the ganymedian atmosphere is atomic hydrogen. Hydrogen atoms were observed as far as 3,000 km from the surface of the moon. Their density on the surface is about 1.5×104 cm−3.[60] For sodium in the diet, see Salt. ...

### Magnetosphere

Enhanced-color Galileo spacecraft image of Ganymede's trailing hemisphere[61]

Magnetic field of the Jovian satellite Ganymede, which is embedded into the magnetosphere of Jupiter. Closed field lines are marked with green color.

The interaction between the ganymedian magnetosphere and Jovian plasma is in many respects similar to that of the solar wind and Earth's magnetosphere.[63][64] The plasma co-rotating with Jupiter impinges on the trailing side of the ganymedian magnetosphere much like the solar wind impinges on the Earth's magnetosphere. The main difference is the speed of plasma flow—supersonic in the case of Earth and subsonic in the case of Ganymede. Because of the subsonic flow, there is no bow shock off the trailing hemisphere of Ganymede.[64] For other uses, see Plasma. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... A United States Navy F/A-18E/F Super Hornet in transonic flight. ... This page is about the physical speed of sound waves in a medium. ... In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ...

In addition to the intrinsic magnetic moment, Ganymede has an induced dipole magnetic field.[11] Its existence is connected with the variation of the Jovian magnetic field near the moon. The induced moment is directed radially to or from Jupiter following the direction of the varying part of the planetary magnetic field. The induced magnetic moment is an order of magnitude weaker than the intrinsic one. The field strength of the induced field at the magnetic equator is about 60 nT—half of that of the ambient Jovian field.[11] The induced magnetic field of Ganymede is similar to those of Callisto and Europa, indicating that this moon also has a subsurface water ocean with a high electrical conductivity.[11] ÊIn physics, the field strength of a field is the magnitude of its vector (spatial) value. ... There is also an asteroid named 204 Kallisto. ... Apparent magnitude: 5. ... Not to be confused with electrical conductance, a measure of an objects or circuits ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. ...

Given that Ganymede is completely differentiated and has a metallic core,[2][34] its intrinsic magnetic field is probably generated in a similar fashion to the Earth's: as a result of conducting material moving in the interior.[11][34] The magnetic field detected around Ganymede is likely to be caused by compositional convection in the core,[34] if the magnetic field is the product of dynamo action, or magnetoconvection.[11][65]

Despite the presence of an iron core, Ganymede's magnetosphere remains enigmatic, particularly given that similar bodies lack the feature.[2] Some research has suggested that, given its relatively small size, the core ought to have sufficiently cooled to the point where fluid motions and a magnetic field would not be sustained. One explanation is that the same orbital resonances proposed to have disrupted the surface also allowed the magnetic field to persist: with Ganymede's eccentricity pumped and tidal heating increased during such resonances, the mantle may have insulated the core, preventing it from cooling.[44] Another explanation is a remnant magnetization of silicate rocks in the mantle, which is possible if the satellite had a more significant dynamo-generated field in the past.[2]

## Origin and evolution

Ganymede likely formed by an accretion in Jupiter’s subnebula, a disk of gas and dust surrounding Jupiter after its formation.[66] The accretion of Ganymede probably took about 10,000 years,[67] much shorter than the 100,000 years estimated for Callisto. Jovian subnebula may have been relatively "gas-starved" when the Galilean satellites formed; this would have allowed for the lengthy accretion times required for Callisto.[66] In contrast Ganymede formed closer to Jupiter, where the subnebular was denser, which explains its shorter formation timescale.[67] This relatively fast formation prevented the escape of accretional heat, which led to ice melt and differentiation: the separation of the rocks and ice. The rocks settled to the center, forming the core. In this respect, Ganymede is different from Callisto, which failed to melt and differentiate early due to loss of the accretional heat during its slower formation.[68] This hypothesis explains why the two Jovian moons look so dissimilar, despite their similar mass and composition.[36][68] In astrophysics, the term accretion is used for at least two distinct processes. ... This article or section does not cite any references or sources. ... In cosmogony, planetary differentiation is a process by which the denser portions of a planet will sink to the center; while less dense materials rise to the surface. ...

After formation, the ganymedian core largely retained the heat accumulated during accretion and differentiation, only slowly releasing it to the ice mantle like a kind thermal battery.[68] The mantle, in turn, transported it to the surface by convection.[36] Soon the decay of radioactive elements within rocks further heated the core, causing increased differentiation: an inner, ironiron sulfide core and a silicate mantle formed.[34][68] With this, Ganymede became a fully differentiated body. By comparison, the radioactive heating of undifferentiated Callisto caused convection in its icy interior, which effectively cooled it and prevented large-scale melting of ice and rapid differentiation.[69] The convective motions in Callisto have caused only a partial separation of rock and ice.[69] Today, Ganymede continues to cool slowly.[34] The heat being released from its core and silicate mantle enables the subsurface ocean to exist,[25] while the slow cooling of the liquid Fe–FeS core causes convection and supports magnetic field generation.[34] The current heat flux out of Ganymede is probably higher than that out of Callisto.[68] Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... 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. ... Iron(II) sulfide is a form of iron sulfide (others include iron pyrite aka Fools Gold), and can be obtained by reacting iron and sulfur under great heat. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ...

## Exploration

Several probes flying by or orbiting Jupiter have explored Ganymede in detail. The first probes to explore were Pioneer 10 and Pioneer 11,[15] neither of which returned much information about the satellite.[70] Voyager 1 and Voyager 2 were next, passing by Ganymede in 1979. They refined its size, revealing it was larger than Saturn's moon Titan, which was previously thought to have been bigger.[71] The grooved terrain was also seen.[72] Voyager Spacecraft File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Voyager Spacecraft File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Voyager spacecraft Launch of Voyager 2 Voyager is also the name of a planned series of unmanned probes to Mars, cancelled in 1968. ... 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. ... For the album by The Verve, see Voyager 1 (album). ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... This article is about the planet. ... Titan (, from Ancient Greek Î¤á¿‘Ï„Î¬Î½) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ...

In 1995, the Galileo spacecraft entered orbit around Jupiter and between 1996 and 2000 made six close flybys to explore Ganymede.[19] These flybys are G1, G2, G7, G8, G28 and G29.[11] During the closest flyby—G2—Galileo passed just 264 km from the surface of Ganymede.[11] During a G1 flyby in 1996, the ganymedian magnetic field was discovered,[73] while the discovery of the ocean was announced in 2001.[19][11] Galileo transmitted a large number of spectral images and discovered several non-ice compounds on the surface of Ganymede.[28] The most recent spacecraft to explore Ganymede up close was New Horizons, which passed by in 2007 on its way to Pluto. New Horizons made topography and composition maps of Ganymede as it sped by.[74][75] 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. ... New Horizons on the launchpad 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. ... For other uses, see Pluto (disambiguation). ...

One proposal to orbit Ganymede was the Jupiter Icy Moons Orbiter. Nuclear fission would have been used to power the craft, which would have been able to study Ganymede in detail.[76] However, the mission was cancelled in 2005 because of budget cuts.[16] There is a proposal to send a dedicated mission to orbit Ganymede, tentatively called The Grandeur of Ganymede. If flown, the orbiter will stay in a low-altitude polar orbit around the moon for at least a year.[42] 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. ... For the generation of electrical power by fission, see Nuclear power plant. ... Altitude is the elevation of an object from a known level or datum. ...

Ganymede is the largest moon in the solar system, and thus has many craters covering its hard surface. ... The Lunar and Planetary Institute is a NASA-funded research institute, dedicated to studies of the solar system, its evolution and formation. ... Some of the moons of the outer planets of the solar system are large enough to be suitable places for colonization. ... Galilean moons of Jupiter Jupiters extensive system of natural satellites â€“ in particular the four large Galilean moons (Io, Europa, Ganymede and Callisto) â€“ has been a common science fiction setting. ...

## Notes

1. ^  Apoapsis is derived from semimajor axis a and eccentricity e: a * (1 + e).
2. ^  Periapsis is derived from semimajor axis a and eccentricity e: a * (1 − e).
3. ^  Surface area derived from the radius r: r2.
4. ^  Volume v derived from the radius r: r3 / 3.
5. ^  Surface gravity derived from the mass m, the gravitational constant G and the radius r: Gm / r2.
6. ^  Escape velocity derived from the mass m, the gravitational constant G and the radius r: $sqrt{frac{2Gm}{r}}$.
7. ^  Leading hemisphere is a hemisphere looking in the direction of the orbital motion, the trailing hemisphere looks in the reverse direction.
8. ^  The dimensionless moment of inertia referred to is I/(mr²), where I is the Moment of Inertia, m the mass, and r the maximal radius. It is 0.4 for a homogenous spherical body, but less than 0.4 if density increases with depth.
9. ^  The surface number density and pressure were calculated from the column densities reported in Hall, et. al. 1998, assuming a scale height of 20 km and temperature 120 K.
10. ^ Laplace-like resonance is similar to the current Laplace resonance among Galilean moons with the only difference that longitudes of the Io–Europa and Europa–Ganymede conjunctions change with rates, whose ratio is a rational number—not unity as in the case of the Laplace resonance

According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ... According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ... A scale height is a term often used in scientific contexts for a distance over which a quantity decreases by a factor of e. ...

## References

1. ^ a b c d Planetary Satellite Mean Orbital Parameters. Jet Propulsion Laboratory, California Institute of Technology.
2. ^ a b c d e f g h i j k l m n o p q r s t Showman, Adam P.; Malhotra, Renu (1999). "The Galilean Satellites" (pdf). Science 286: 77–84. doi:10.1126/science.286.5437.77.
3. ^ a b Bills, Bruce G. (2005). "Free and forced obliquities of the Galilean satellites of Jupiter" 175: 233–247. doi:10.1016/j.icarus.2004.10.028.
4. ^ a b Yeomans, Donald K. (2006-07-13). Planetary Satellite Physical Parameters. JPL Solar System Dynamics. Retrieved on 2007-11-05.
5. ^ a b Delitsky, Mona L.; Lane, Arthur L. (1998). "Ice chemistry of Galilean satellites" (pdf). J.of Geophys. Res. 103 (E13): 31,391–31,403. doi:10.1029/1998JE900020.
6. ^ Orton, G.S.; Spencer, G.R.; Travis, L.D. et.al. (1996). "Galileo Photopolarimeter-radiometer observations of Jupiter and the Galilean Satellites". Science 274: 389–391.
7. ^ a b c d e Hall, D.T.; Feldman, P.D.; McGrath, M.A. et.al. (1998). "The Far-Ultraviolet Oxygen Airglow of Europa and Ganymede". The Astrophysical Journal 499: 475–481. doi:10.1086/305604.
8. ^ a b Jupiter's Moons. The Planetary Society. Retrieved on 2007-12-07.
9. ^ a b c d Ganymede. nineplanets.org (October 31, 1997). Retrieved on 2008-02-27.
10. ^ a b Solar System's largest moon likely has a hidden ocean. Jet Propulsion Laboratory. NASA (December 16, 2000). Retrieved on 2008-01-11.
11. ^ a b c d e f g h i j k l m n o p Kivelson, M.G.; Khurana, K.K.; Coroniti, F.V. et.al. (2002). "The Permanent and Inductive Magnetic Moments of Ganymede" (pdf). Icarus 157: 507–522. doi:0.1006/icar.2002.6834.
12. ^ a b c d e Eviatar, Aharon; Vasyliunas, Vytenis M.; Gurnett, Donald A. et.al. (2001). "The ionosphere of Ganymede" (ps). Plan.Space Sci. 49: 327–336. doi:10.1016/S0032-0633(00)00154-9.
13. ^ Sidereus Nuncius. Eastern Michigan University. Retrieved on 2008-01-11.
14. ^ a b c d e Satellites of Jupiter. The Galileo Project. Retrieved on 2007-11-24.
15. ^ a b Pioneer 11. Solar System Exploration. Retrieved on 2008-01-06.
16. ^ a b Jupiter Icy Moons Orbiter Victim of Budget Cut. Planet Surveyor. Retrieved on 2008-01-06.
17. ^ a b The Discovery of the Galilean Satellites. Views of the Solar System. Space Research Institute, Russian Academy of Sciences. Retrieved on 2007-11-24.
18. ^ DISCOVERY. Cascadia Community College. Retrieved on 2007-11-24.
19. ^ a b c d e Miller, Ron; William K. Hartmann (May 2005). The Grand Tour: A Traveler's Guide to the Solar System, 3rd edition, Thailand: Workman Publishing, 108–114. ISBN 0-7611-3547-2.
20. ^ a b c Musotto, Susanna; Varadi, Ferenc; Moore, William; Schubert, Gerald (2002). "Numerical Simulations of the Orbits of the Galilean Satellites" 159: 500–504. doi:10.1006/icar.2002.6939.
21. ^ a b c High Tide on Europa. SPACE.com. Retrieved on 2007-12-07.
22. ^ a b c d e f g h i Showman, Adam P.; Malhotra, Renu (1997). "Tidal Evolution into the Laplace Resonance and the Resurfacing of Ganymede" (pdf). Icarus 127: 93–111. doi:10.1006/icar.1996.5669.
23. ^ Peale, S.J.; Lee, Man Hoi (2002). "A Primordial Origin of the Laplace Relation Among the Galilean Satellites". Science 298: 593–597. doi:10.1126/science.1076557.
24. ^ a b c d e f g Kuskov, O.L.; Kronrod, V.A. (2005). "Internal structure of Europa and Callisto" 177: 550–369. doi:10.1016/j.icarus.2005.04.014.
25. ^ a b c d e f g Spohn, T.; Schubert, G. (2003). "Oceans in the icy Galilean satellites of Jupiter?" (pdf). Icarus 161: 456–467. doi:10.1016/S0019-1035(02)00048-9.
26. ^ a b c d Calvin, Wendy M.; Clark, Roger N.;Brown, Robert H.; and Spencer John R. (1995). "Spectra of the ice Galilean satellites from 0.2 to 5 µm: A compilation, new observations, and a recent summary". J.of Geophys. Res. 100: 19,041–19,048.
27. ^ Ganymede: the Giant Moon. Wayne RESA. Retrieved on 2007-12-31.
28. ^ a b c McCord, T.B.; Hansen, G.V.; Clark, R.N. et.al. (1998). "Non-water-ice constituents in the surface material of the icy Galilelean satellites from Galileo near-infrared mapping spectrometer investigation". J. of Geophys. Res. 103 (E4): 8,603–8,626.
29. ^ a b McCord, Thomas B.; Hansen, Gary B.; Hibbitts, Charles A. (2001). "Hydrated Salt Minerals on Ganymede’s Surface: Evidence of an Ocean Below". Science 292: 1523–1525. doi:10.1126/science.1059916.
30. ^ Domingue, Deborah; Lane, Arthur; Moth, Pimol (1996). "Evidence from IUE for Spatial and Temporal Variations in the Surface Composition of the Icy Galilean Satellites". Bulletin of the American Astronomical Society 28: 1070.
31. ^ Domingue, Deborah L.; Lane, Arthur L.; Beyer, Ross A. (1998). "IEU’s detection of tenuous SO2 frost on Ganymede and its rapid time variability". Geophys. Res. Lett. 25 (16): 3,117–3,120. doi:10.1029/98GL02386.
32. ^ a b Hibbitts, C.A.; Pappalardo, R.; Hansen, G.V.; McCord, T.B. (2003). "Carbon dioxide on Ganymede". J.of Geophys. Res. 108 (E5): 5,036. doi:10.1029/2002JE001956.
33. ^ a b c d e f Sohl, F.; Spohn, T; Breuer, D.; Nagel, K. (2002). "Implications from Galileo Observations on the Interior Structure and Chemistry of the Galilean Satellites". Icarus 157: 104–119. doi:10.1006/icar.2002.6828.
34. ^ a b c d e f g h i j k Hauk, Steven A.; Aurnou, Jonathan M.; Dombard, Andrew J. (2006). "Sulfur’s impact on core evolution and magnetic field generation on Ganymede" (pdf). J. of Geophys. Res. 111: E09008. doi:10.1029/2005JE002557.
35. ^ a b Kuskov, O.L.; Kronrod, V.A.; Zhidicova, A.P. (2005). "Internal Structure of Icy Satellites of Jupiter" (pdf). Geophysical Research Abstracts 7: 01892. European Geosciences Union.
36. ^ a b c Freeman, J. (2006). "Non-Newtonian stagnant lid convection and the thermal evolution of Ganymede and Callisto" (pdf) 54: 2–14. doi:10.1016/j.pss.2005.10.003.
37. ^ Karr, Richard (January 2001). "Jupiter's Two-Faced Moon, Ganymede, Falling Into Line". Science 291 (5501): 22–23.
38. ^ a b c Barr, A.C.; Pappalardo, R. T. et. al. (2001). "Rise of Deep Melt into Ganymede's Ocean and Implications for Astrobiology" (pdf). Lunar and Planetary Science Conference 32: 1781.
39. ^ Schenk, Paul M. (2002). "Thickness constraints on the icy shells of the galilean satellites from a comparison of crater shapes". Letters to Nature 417: 419–421. doi:10.1038/417419a.
40. ^ Anderson, John D.; Schubert, Gerald; Jacobson, Robert A. et.al. (2004). "Discovery of Mass Anomalies on Ganymede". Science 305: 989–991. doi:10.1126/science.1099050.
41. ^ Petterson, Wesley; Head, James W.; Collins, Geoffrey C. et.al. (2007). "A Global Geologic Map of Ganymede" (pdf). Lunar and Planetary Science XXXVIII: 1098.
42. ^ a b Pappalardo, R.T.; Khurana, K.K.; Moore, W.B. (2001). "The Grandeur of Ganymede: Suggested Goals for an Orbiter Mission" (pdf). Lunar and Planetary Science XXXII: 4062.
43. ^ Showman, Adam P.; Stevenson, David J.; Malhotra, Renu (1997). "Coupled Orbital and Thermal Evolution of Ganymede" (pdf). Icarus 129: 367–383. doi:10.1006/icar.1997.5778.
44. ^ a b Bland; Showman, A.P.; Tobie, G. (March 2007). "Ganymede's orbital and thermal evolution and its effect on magnetic field generation" (pdf). Lunar and Planetary Society Conference 38: 2020.
45. ^ Huffmann, H.; Sohl, F. et al. (2004). "Internal Structure and Tidal Heating of Ganymede" (PDF). European Geosciences Union, Geophysical Research Abstracts 6.
46. ^ a b Zahnle, K.; Dones, L. (1998). "Cratering Rates on the Galilean Satellites" (pdf). Icarus 136: 202–222. doi:10.1006/icar.1998.6015.
47. ^ Ganymede. Lunar and Planetary Institute (1997).
48. ^ Casacchia, R.; Strom, R.G. (1984). "Geologic evolution of Galileo Regio". Journal of Geophysical Research 89: B419–B428. Bibcode: 1984LPSC...14..419C.
49. ^ Khurana, Krishan K.; Pappalardo, Robert T.; Murphy, Nate; Denk, Tilmann (2007). "The origin of Ganymede's polar caps". Icarus 191 (1): 193–202. doi:10.1016/j.icarus.2007.04.022.
50. ^ a b Carlson, R.W.; Bhattacharyya, J.C.; Smith, B.A. et.al. (1973). "Atmosphere of Ganymede from its occultation of SAO 186800 on 7 June 1972". Science 53: 182.
51. ^ a b c Broadfoot, A.L.; Sandel, B.R.; Shemansky, D.E. et.al. (1981). "Overview of the Voyager Ultraviolet Spectrometry Results through Jupiter Encounter" (pdf). Science 86: 8259–8284.
52. ^ a b Hubble Finds Thin Oxygen Atmosphere on Ganymede. Jet Propulsion Laboratory. NASA (October 1996). Retrieved on 2008-01-15.
53. ^ a b Feldman, Paul D. (2000). "HST/STIS Ultraviolet Imaging of Polar Aurora on Ganymede". The Astrophysical Journal 535: 1085–1090. doi:10.1086/308889.
54. ^ Johnson, R.E. (1997). "Polar “Caps” on Ganymede and Io Revisited". Icarus 128 (2): 469–471. doi:10.1006/icar.1997.5746.
55. ^ a b c Paranicas, C.; Paterson, W.R.; Cheng, A.F. et.al. (1999). "Energetic particles observations near Ganymede". J.of Geophys.Res. 104 (A8): 17,459–17,469. doi:10.1029/1999JA900199.
56. ^ Noll, Keith S.; Johnson, Robert E. et al. (July 1996). "Detection of Ozone on Ganymede". Science 273 (5273): 341–343. Retrieved on 2008-01-13.
57. ^ Calvin, Wendy M.; Spencer, John R. (December 1997). "Latitudinal Distribution of O2on Ganymede: Observations with the Hubble Space Telescope". Icarus 130 (2): 505-516. doi:10.1006/icar.1997.5842.
58. ^ Vidal, R. A.; Bahr, D. et al. (1997). "Oxygen on Ganymede: Laboratory Studies". Science 276 (5320): 1839–1842. doi:10.1126/science.276.5320.1839.
59. ^ Brown, Michael E. (1997). "A Search for a Sodium Atmosphere around Ganymede". Icarus 126 (1): 236–238. doi:10.1006/icar.1996.5675.
60. ^ Barth, C.A.; Hord, C.W.; Stewart, A.I. et.al. (1997). "Galileo ultraviolet spectrometer observations of atomic hydrogen in the atmosphere of Ganymede". Geophys. Res. Lett. 24 (17): 2147–2150.
61. ^ Galileo has successful flyby of Ganymede during eclipse. Spaceflight Now. Retrieved on 2008-01-19.
62. ^ a b c Kivelson, M.G.; Khurana, K.K.; Coroniti, F.V. et.al. (1997). "The magnetic field and magnetosphere of Ganymede" (pdf). Geophys. Res. Lett. 24 (17): 2155–2158.
63. ^ a b c d Kivelson, M.G.; Warnecke, J.; Bennett, L. et.al. (1998). "Ganymede’s magnetosphere: magnetometer overview" (pdf). J.of Geophys. Res. 103 (E9): 19,963–19,972. doi:10.1029/98JE00227.
64. ^ a b Volwerk, M.; Kivelson, M.G.; Khurana, K.K.; McPherron, R.L. (1999). "Probing Ganymede’s magnetosphere with field line resonances" (pdf). J.of Geophys. Res. 104 (A7): 14,729–14,738. doi:10.1029/1999JA900161.
65. ^ Hauck, Steven A. (2002). "Internal structure and mechanism of core convection on Ganymede" (pdf). Lunar and Planetary Science XXXIII: 1380.
66. ^ a b Canup, Robin M.; Ward, William R. (2002). "Formation of the Galilean Satellites: Conditions of Accretion" (pdf) 124: 3404–3423. doi:10.1086/344684.
67. ^ a b Mosqueira, Ignacio; Estrada, Paul R (2003). "Formation of the regular satellites of giant planets in an extended gaseous nebula I: subnebula model and accretion of satellites" 163: 198–231. doi:10.1016/S0019-1035(03)00076-9.
68. ^ a b c d e McKinnon, William B. (2006). "On convection in ice I shells of outer Solar System bodies, with detailed application to Callisto" 183: 435–450. doi:10.1016/j.icarus.2006.03.004.
69. ^ a b Nagel, K.A; Breuer, D.; Spohn, T. (2004). "A model for the interior structure, evolution, and differentiation of Callisto" 169: 402–412. doi:10.1016/j.icarus.2003.12.019.
70. ^ Exploration of Ganymede. Terraformers Society of Canada. Retrieved on 2008-01-06.
71. ^ Voyager 1 and 2. ThinkQuest. Retrieved on 2008-01-06.
72. ^ The Voyager Planetary Mission. Views of the Solar System. Retrieved on 2008-01-06.
73. ^ New Discoveries From Galileo. Jet Propulsion Laboratory. Retrieved on 2008-01-06.
74. ^ Pluto-Bound New Horizons Spacecraft Gets A Boost From Jupiter. Space Daily. Retrieved on 2008-01-06.
75. ^ Grundy, W.M.; Buratti, B.J.; Cheng, A.F. et.al. (2007). "New Horizons Mapping of Europa and Ganymede". Science 318: 234–237. doi:10.1126/science.1147623.
76. ^ Jupiter Icy Moons Orbiter (JIMO). The Internet Encyclopedia of Science. Retrieved on 2008-01-06.

Results from FactBites:

 Ganymede (moon) - Wikipedia, the free encyclopedia (1504 words) Ganymede is composed of silicate rock and water ice, with an ice crust floating over a warmer ice mantle that may contain a layer of liquid water. Ganymede's intrinsic magnetic field is probably generated in a similar fashion to the Earth's: as a result of conducting material moving in the interior, likely originating in its metallic core. The Primeval to fuse with Ganymede is Lungs Primeval (ZX-17), which creates a "Klein Space" within itself (a pocket dimension bearing spatial geometry similar to that of a klein bottle) in an attempt to seal GGG away upon their arrival in Jovian orbit.
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