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Takafumi Matsui - One of the best experts on this subject based on the ideXlab platform.
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formation of a hot proto atmosphere on the accreting giant Icy Satellite implications for the origin and evolution of titan ganymede and callisto
Journal of Geophysical Research, 1994Co-Authors: Kiyoshi Kuramoto, Takafumi MatsuiAbstract:Judging from accretion energy and accretion time for the giant Icy Satellites it is suggested that a proto-atmosphere is formed by the evaporation of Icy materials during accretion of these bodies around the proto-gaseous giant planets. We study the blanketing effect of proto-atmosphere during accretion of these Satellites in the gas-free environment. We use a gray atmosphere model in which the condensation of H2O in a convective atmosphere is taken into account. The numerical results strongly suggest that the accretion energy flux is large enough to increase the surface temperature higher than ∼500 K during accretion due to the blanketing effect of proto-atmosphere as long as the accretion time is shorter than 105 years. Such a high surface temperature causes the formation of a deep water-rich ocean due to the melting of Icy materials. Also a rocky core should be eventually formed by sinking of rocky materials through the water-rich ocean during accretion. Therefore, the apparent difference in the surface geologic features between Ganymede and Callisto can hardly be explained by whether or not these bodies have experienced the formation of rocky core. Stability of hydrostatic structure of the proto-atmosphere is also studied. Vigorous escape of the proto-atmosphere is likely to occur under high surface temperature. A large portion of accretional energy is possibly consumed by the vigorous escape during accretion. Thus, the giant Icy Satellites may lose a significant amount of Icy materials during their accretions. This can explain the ice-depleted composition of Titan inferred from the observed mean densities of Saturnian Satellites, if the accretion occurs within 104–105 years. Such a significant loss of Icy materials is also expected for Ganymede and Callisto. The escape and catalytic reaction in the hot proto-atmosphere may play an important role in formation of the present N2-abundant and CO-depleted atmosphere of Titan.
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Formation of a hot proto‐atmosphere on the accreting giant Icy Satellite: Implications for the origin and evolution of Titan, Ganymede, and Callisto
Journal of Geophysical Research, 1994Co-Authors: Kiyoshi Kuramoto, Takafumi MatsuiAbstract:Judging from accretion energy and accretion time for the giant Icy Satellites it is suggested that a proto-atmosphere is formed by the evaporation of Icy materials during accretion of these bodies around the proto-gaseous giant planets. We study the blanketing effect of proto-atmosphere during accretion of these Satellites in the gas-free environment. We use a gray atmosphere model in which the condensation of H2O in a convective atmosphere is taken into account. The numerical results strongly suggest that the accretion energy flux is large enough to increase the surface temperature higher than ∼500 K during accretion due to the blanketing effect of proto-atmosphere as long as the accretion time is shorter than 105 years. Such a high surface temperature causes the formation of a deep water-rich ocean due to the melting of Icy materials. Also a rocky core should be eventually formed by sinking of rocky materials through the water-rich ocean during accretion. Therefore, the apparent difference in the surface geologic features between Ganymede and Callisto can hardly be explained by whether or not these bodies have experienced the formation of rocky core. Stability of hydrostatic structure of the proto-atmosphere is also studied. Vigorous escape of the proto-atmosphere is likely to occur under high surface temperature. A large portion of accretional energy is possibly consumed by the vigorous escape during accretion. Thus, the giant Icy Satellites may lose a significant amount of Icy materials during their accretions. This can explain the ice-depleted composition of Titan inferred from the observed mean densities of Saturnian Satellites, if the accretion occurs within 104–105 years. Such a significant loss of Icy materials is also expected for Ganymede and Callisto. The escape and catalytic reaction in the hot proto-atmosphere may play an important role in formation of the present N2-abundant and CO-depleted atmosphere of Titan.
Jeffrey S. Kargel - One of the best experts on this subject based on the ideXlab platform.
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THE AMMONIA-WATER SYSTEM AND THE CHEMICAL DIFFERENTIATION OF Icy SatelliteS
Icarus, 1997Co-Authors: D. L. Hogenboom, Jeffrey S. Kargel, G.j. Consolmagno, T. C. Holden, L. Lee, M. BuyyounouskiAbstract:Abstract We report the discovery of the first high-pressure polymorphs of ammonia hydrates: ammonia monohydrate II and ammonia dihydrate II. The subsolidus transitions and melting curves of these substances are shown by their volume–temperature functions; uncalibrated calorimetry corroborates these phase changes. From 20 to 300 MPa ammonia dihydrate and ice melt at a eutectic to form water-rich liquids; at lower and higher pressures, ammonia dihydrate melts incongruently to ammonia-rich liquids. The new data are consistent with independently known thermodynamic parameters of the ammonia–water system. These results fill in an important region of pressure–temperature space not previously studied; a body of previous data reported by other investigators covers a complementary region (higher pressures), but in the light of the new data those earlier results now appear to have been misinterpreted. We show that a suitable reinterpretation of the previous data supports the identification of at least one high-pressure polymorph of each compound. The behavior of the system H2O–NH3in many ways follows that of MgO–SiO2, and the roles of ammonia–water in Icy Satellite evolution may parallel those of magnesium silicates in Earth's structure, volcanism, and deep mantle tectonism. Pressure-related effects, including a pressure influence on the ammonia content of cryomagmas, might be significant in determining some potentially observable aspects of cryovolcanic morphologies, surface compositions, and interior structures of Icy Satellites.
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Ammonia-water volcanism on Icy Satellites: Phase relations at 1 atmosphere
Icarus, 1992Co-Authors: Jeffrey S. KargelAbstract:Abstract Icy Satellites exhibit an amazing variety of terrains, many of which were formed by extrusions of aqueous solutions. Aqueous ammonia has been implicated on the basis of theoretical and morphological evidence as a probably cryovolcanic agent on some resurfaced Icy Satellites. Considering the solvent and caustic properties of ammonia-water (pH up to 13) with respect to chondritic rock, and that many other ammonia-water-soluble substances are probably present in Satellite ices, it is unlikely that ammonia-water magmas would be pure. Comets and carbonaceous chondrites represent two possible components of Icy Satellites. Several comets contain ∼ 1 to several percent each of methanol, formaldehyde, and carbon dioxide relative to water, and C1 and C2 carbonaceous chondrites contain up to 10% magnesium sulfate. Carbon dioxide, magnesium sulfate, and formaldehyde sequester ammonia as ammonium carbonate, ammonium sulfate, and the organic salt hexamethylenetetramine (HMT). If these reactions leave excess ammonia, the resulting ices may include water ice, ammonia dihydrate, and methanol monoammoniate in addition to the reaction salts. This mixture melts near 153 K yielding an extremely viscous solution of water, ammonia, methanol, and small amounts of salts. This liquid may resemble the viscous lavas extruded on Triton, Ariel, and Miranda. However, if these reactions sequester all available ammonia, or if ammonia was not initially present in an Icy Satellite, then melting produces comparatively low-viscosity, ammonia-deficient saline or methanol solutions. Formation of ammonia-rich liquids is possible only if the molar abundance of ammonia N NH 3 > (2N CO 2 + 2N MgSO 4 + sol2 3N H 2 CO ) . For instance, direct melting of pure Comet Halley, even though it may contain some ammonia, probably would not yield an ammonia-water liquid. Sulfur-and carbon-bearing constituents in ammonia-water lavas would alter to spectrally important chromophores on irradiated Satellite surfaces, possibly explaining geologically correlated variations in the colors and albedos of Icy Satellites. Many cryovolcanic surfaces have nearly uniform spectrophotometric properties and may be explained as compositionally invariant eutectic or peritectic mixtures. Other cryovolcanic terrains have stark color and albedo contrasts and may be explained as compositionally distinct melt products. Small but important quantities of dissolved potassium-and rubidium-bearing salts are probably sufficient for isotopic dating.
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Brine volcanism and the interior structures of asteroids and Icy Satellites
Icarus, 1991Co-Authors: Jeffrey S. KargelAbstract:Abstract Cryovolcanism is among the foremost processes responsible for modifying the surfaces of Icy Satellites. Volcanic brine petrogenesis in ammonia-deficient Satellites should mainly involve eutectic melting in relevant salt-water systems. Carbonaceous chondrites provide useful insights into the compositions of salts and aqueously altered rock in Icy Satellites and asteroids. C1 chondrites contain about one-fifth by mass of salts in various states of hydration. Many aspects of the petrogenesis and physical volcanology of Icy Satellite brines should be well described in the system H2OMgSO4Na2SO4. Minor components include sulfates of K, Ni, Mn, and Ca. Chondrites also contain abundant carbonates, but these are probably not very important in brine magmatism due to their low solubilities under expected conditions. Chlorides are also unimportant under most circumstances because of the low cosmic abundance ratio of Cl/S. Soluble salts may have profound effects on the geology and structure of Icy Satellites and asteroids. In some models late episodes of water volcanism are facilitated by high buoyant forces due to the relatively high densities of sulfate-rich mantle and crustal layers. In other models early hypersaline brine volcanism quickly yields to plutonic magmatism due to low crustal densities. Europa probably has a layered crust composed of anhydrous MgNa sulfates near the base and a frozen or partially molten eutectic mixture of ice and hydrated Mg and Na sulfates near the surface. Ganymede may have a crust about 300 km thick composed of a 10:1 ratio of ice: mirabilite, and a mantle 500 km thick composed of 50% ice phases plus 50% hydrated Mg and Na sulfates.
Francis Nimmo - One of the best experts on this subject based on the ideXlab platform.
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Tidal heating in Icy Satellite oceans
Icarus, 2014Co-Authors: E.m.a. Chen, Francis Nimmo, Gary A. GlatzmaierAbstract:Abstract Tidal heating plays a significant role in the evolution of many Satellites in the outer Solar System; however, it is unclear whether tidal dissipation in a global liquid ocean can represent a significant additional heat source. Tyler (Tyler, R.H. [2008]. Nature 456, 770-772; Tyler, R.H. [2009]. Geophys. Res. Lett. 36, doi:10.1029/2009GL038300) suggested that obliquity tides could drive large-scale flow in the oceans of Europa and Enceladus, leading to significant heating. A critical unknown in this previous work is what the tidal quality factor, Q , of such an ocean should be. The corresponding tidal dissipation spans orders of magnitude depending on the value of Q assumed. To address this issue we adopt an approach employed in terrestrial ocean modeling, where a significant portion of tidal dissipation arises due to bottom drag, with the drag coefficient O (0.001) being relatively well-established. From numerical solutions to the shallow-water equations including nonlinear bottom drag, we obtain scalings for the equivalent value of Q as a function of this drag coefficient. In addition, we provide new scaling relations appropriate for the inclusion of ocean tidal heating in thermal–orbital evolution models. Our approach is appropriate for situations in which the ocean bottom topography is much smaller than the ocean thickness. Using these novel scalings, we calculate the ocean contribution to the overall thermal energy budgets for many of the outer Solar System Satellites. Although uncertainties such as ocean thickness and Satellite obliquity remain, we find that for most Satellites it is unlikely that ocean tidal dissipation is important when compared to either radiogenic or solid-body tidal heating. Of known Satellites, Triton is the most likely Icy Satellite to have ocean tidal heating play a role in its present day thermal budget and long-term thermal evolution.
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shear heating as the origin of the plumes and heat flux on enceladus
Nature, 2007Co-Authors: Francis Nimmo, Robert T. Pappalardo, J R Spencer, Mccall MullenAbstract:The Cassini flyby of 14 July 2005 revealed plumes of water vapour and ice associated with the 'tiger stripe' features on the surface of Saturn's Icy moon Enceladus. Since then the challenge has been to explain the nature of the plumes and the forces driving them. Two papers this week offer an explanation that accounts for both the plume characteristics and the presence of hot spots without the need to assume the existence of near-surface liquid water, a requirement of some previous models. Nimmo et al. identify tidally driven lateral fault motions near the tiger stripes as the most likely drivers of heat and vapour production. And Hurford et al. show that as Enceladus orbits Saturn, the parent planet's tides make the Satellite's ice flex. This may cause the tiger stripes to open and close periodically, exposing volatile gases and allowing them to be released. Enceladus, a small Icy Satellite of Saturn, has active plumes jetting from localized fractures (‘tiger stripes’) within an area of high heat flux near the south pole. Nimmo et al. show that the most likely explanation is shear heating by tidally driven lateral (strike-slip) fault motion with a displacement of about 0.5 metres over a tidal period: vapour produced by this heating may escape as plumes through cracks reopened by the tidal stresses. Enceladus, a small Icy Satellite of Saturn, has active plumes jetting from localized fractures (‘tiger stripes’) within an area of high heat flux near the south pole1,2,3,4. The plume characteristics1 and local high heat flux2 have been ascribed either to the presence of liquid water within a few tens of metres of the surface1, or the decomposition of clathrates5. Neither model addresses how delivery of internal heat to the near-surface is sustained. Here we show that the most likely explanation for the heat2 and vapour production6,7 is shear heating by tidally driven lateral (strike-slip) fault motion1,8,9 with displacement of ∼0.5 m over a tidal period. Vapour produced by this heating may escape as plumes through cracks reopened by the tidal stresses10. The ice shell thickness needed to produce the observed heat flux is at least 5 km. The tidal displacements required imply a Love number of h2 > 0.01, suggesting that the ice shell is decoupled from the silicate interior by a subsurface ocean. We predict that the tiger-stripe regions with highest relative temperatures will be the lower-latitude branch of Damascus, Cairo around 60° W longitude and Alexandria around 150° W longitude.
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Dynamics of rifting and modes of extension on Icy Satellites
Journal of Geophysical Research, 2004Co-Authors: Francis NimmoAbstract:[1] A simple numerical model of extension in Icy Satellite shells is developed. Thinning of the ice weakens the shell, promoting further extension. If lateral flow in the lower part of the shell is unimportant, extension is opposed and wide rifts are generated; if lateral flow is rapid, localized extension is favored and narrow rifts are produced. Thick shells or high strain rates favor the development of narrow rifts; low strain rates favor wide rifting. It is proposed that bands, extensional features on Europa, are narrow rifts, while groove lanes on Ganymede are wide rifts. The existence of wide rifting on Ganymede is consistent with previous estimates of a conductive shell thickness at the time of rifting of 4–8 km and a strain rate of 10 � 15 s � 1 ) strain rates at the time of rifting. Whether this shell thickness applies to present-day Europa depends on the age of band formation, which is poorly known. The difference between rifting behavior on Ganymede and Europa is due to either higher strain rates or higher shell thicknesses on Europa during rifting. The mean stresses required to cause the observed rifting are � 0.2 MPa for Ganymede and � 0.3 MPa for Europa. These values are comparable to estimates derived from flexural features. INDEX TERMS: 5475 Planetology: Solid Surface Planets: Tectonics (8149); 6218 Planetology: Solar System Objects: Jovian Satellites; 8109 Tectonophysics: Continental tectonics—extensional (0905); 8160 Tectonophysics: Rheology—general; KEYWORDS: Europa, Ganymede, extension, faulting, ice
J. B. Dalton - One of the best experts on this subject based on the ideXlab platform.
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Chemical Composition of Icy Satellite Surfaces
Space Science Reviews, 2010Co-Authors: J. B. Dalton, Katrin Stephan, Athena Coustenis, Thomas B. Mccord, Robert W. Carlson, Dwight P Cruikshank, Angioletta CoradiniAbstract:Much of our knowledge of planetary surface composition is derived from remote sensing over the ultraviolet through infrared wavelength ranges. Telescopic observations and, in the past few decades, spacecraft mission observations have led to the discovery of many surface materials, from rock-forming minerals to water ice to exotic volatiles and organic compounds. Identifying surface materials and mapping their distributions allows us to constrain interior processes such as cryovolcanism and aqueous geochemistry.
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Chemical Composition of Icy Satellite Surfaces
Space Science Reviews, 2010Co-Authors: J. B. Dalton, Katrin Stephan, Athena Coustenis, Thomas B. Mccord, Robert W. Carlson, Dwight P Cruikshank, Angioletta CoradiniAbstract:Much of our knowledge of planetary surface composition is derived from remote sensing over the ultraviolet through infrared wavelength ranges. Telescopic observations and, in the past few decades, spacecraft mission observations have led to the discovery of many surface materials, from rock-forming minerals to water ice to exotic volatiles and organic compounds. Identifying surface materials and mapping their distributions allows us to constrain interior processes such as cryovolcanism and aqueous geochemistry. The recent progress in understanding of Icy Satellite surface composition has been aided by the evolving capabilities of spacecraft missions, advances in detector technology, and laboratory studies of candidate surface compounds. Pioneers 10 and 11, Voyagers I and II, Galileo, Cassini and the New Horizons mission have all made significant contributions. Dalton (Space Sci. Rev., 2010 , this issue) summarizes the major constituents found or inferred to exist on the surfaces of the Icy Satellites (cf. Table 1 from Dalton, Space Sci. Rev., 2010 , this issue), and the spectral coverage and resolution of many of the spacecraft instruments that have revolutionized our understanding (cf. Table 2 from Dalton, Space Sci. Rev., 2010 , this issue). While much has been gained from these missions, telescopic observations also continue to provide important constraints on surface compositions, especially for those bodies that have not yet been visited by spacecraft, such as Kuiper Belt Objects (KBOs), trans-Neptunian Objects (TNOs), Centaurs, the classical planet Pluto and its moon, Charon. In this chapter, we will discuss the major Satellites of the outer solar system, the materials believed to make up their surfaces, and the history of some of these discoveries. Formation scenarios and subsequent evolution will be described, with particular attention to the processes that drive surface chemistry and exchange with interiors. Major similarities and differences between the Satellites are discussed, with an eye toward elucidating processes operating throughout the outer solar system. Finally we discuss the outermost Satellites and other bodies, and summarize knowledge of their composition. Much of this review is likely to change in the near future with ongoing and planned outer planet missions, adding to the sense of excitement and discovery associated with our exploration of our planetary neighborhood.
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A Cryogenic Reflectance Spectroscopy Facility for Characterization of Candidate Icy Satellite Surface Compounds in Support of Spacecraft Observations
2010Co-Authors: J. B. DaltonAbstract:Introduction: Interpretation of visibleto nearinfrared spectral observations of Icy Satellite surfaces from spacecraft-based imaging spectrometers such as the Galileo Near Infrared Mapping Spectrometer (NIMS), Cassini Visual and Infrared Imaging Spectrometer (VIMS) and New Horizons Linear Etalon Imaging Spectral Array (LEISA) is critically dependent upon availability of laboratory spectra of candidate surface materials acquired under conditions relevant to these observations. Application of cryogenic laboratory reflectance spectroscopy to Galileo observations has demonstrated [1,2,3] the potential to differentiate mixtures of surface compounds on Europa, including sulfuric acid and sulfate salt hydrates, enabling the mapping of abundances and distributions of materials in discrete geologic units [4]. The Planetary Ice Characterization Laboratory (PICL) at JPL has been established in order to provide relevant measurements for studies of Icy Satellite surface compositions. Background: Laboratory spectra are needed for a broad range of materials proposed to exist on Icy Satellite surfaces [5,6,7] including minerals, salts, volatile ices, and organics. Though the peer-reviewed literature abounds with published infrared spectra, only a few compounds have thus far been characterized in the manner required to facilitate quantitative interpretation of spacecraft observations of Icy Satellites. In order to be applied to such observations, laboratory measurements must satisfy the following four requirements:
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surface composition of hyperion
Nature, 2007Co-Authors: Dale P Cruikshank, J. B. Dalton, A. Coradini, K Stephan, G Filacchione, A. R. Hendrix, C. J. Hansen, J M Bauer, P Cerroni, F TosiAbstract:Saturn's moon Hyperion, an irregular shaped object in a tumbling orbit, looks odd: the Cassini flyby of September 2005 revealed a unique spongy surface. Two papers this week present the initial Cassini results. First, imaging and radio data suggest that the spongy appearance is caused by impact cratering on a porous body. And second, near-infrared and ultraviolet spectroscopy reveal details of the surface composition of the highly reflective areas that cover much of the surface, and also of the darker areas, mostly at the bottom of craters. The spectra are consistent with the presence of water ice contaminated with an organic solid. The low-albedo (dark) material is spectroscopically similar to that found on two other saturnian moons, Iapetus and Phoebe, containing a mixture of water ice, complex organics, carbon dioxide and nitriles. This cocktail of materials resembles those seen in comets and probably in Kuiper Belt objects. The surface of Hyperion has a large region of high albedo with the signature of H2O ice and another zone of albedo about a factor of four lower. Observations of the surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft detail that the low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe. Hyperion, Saturn’s eighth largest Icy Satellite, is a body of irregular shape in a state of chaotic rotation1,2. The surface is segregated into two distinct units. A spatially dominant high-albedo unit having the strong signature of H2O ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup-like craters. Here we report observations of Hyperion’s surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft at closest approach during a fly-by on 25–26 September 2005. The close fly-by afforded us the opportunity to obtain separate reflectance spectra of the high- and low-albedo surface components. The low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe and a hemisphere-wide superficial coating on Iapetus.
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temperature dependence of cryogenic ammonia water ice mixtures and implications for Icy Satellite surfaces
Lunar and Planetary Science Conference, 2001Co-Authors: J. B. Dalton, J M Curchin, R N ClarkAbstract:Infrared spectra of ammonia-water ice mixtures reveal temperature-dependent absorption bands due to ammonia. These features, at 1.04, 2.0, and 2.25 microns, may shed light on the surface compositions of the Galilean and Saturnian Satellites. Additional information is contained in the original extended abstract.
Angioletta Coradini - One of the best experts on this subject based on the ideXlab platform.
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Chemical Composition of Icy Satellite Surfaces
Space Science Reviews, 2010Co-Authors: J. B. Dalton, Katrin Stephan, Athena Coustenis, Thomas B. Mccord, Robert W. Carlson, Dwight P Cruikshank, Angioletta CoradiniAbstract:Much of our knowledge of planetary surface composition is derived from remote sensing over the ultraviolet through infrared wavelength ranges. Telescopic observations and, in the past few decades, spacecraft mission observations have led to the discovery of many surface materials, from rock-forming minerals to water ice to exotic volatiles and organic compounds. Identifying surface materials and mapping their distributions allows us to constrain interior processes such as cryovolcanism and aqueous geochemistry.
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Chemical Composition of Icy Satellite Surfaces
Space Science Reviews, 2010Co-Authors: J. B. Dalton, Katrin Stephan, Athena Coustenis, Thomas B. Mccord, Robert W. Carlson, Dwight P Cruikshank, Angioletta CoradiniAbstract:Much of our knowledge of planetary surface composition is derived from remote sensing over the ultraviolet through infrared wavelength ranges. Telescopic observations and, in the past few decades, spacecraft mission observations have led to the discovery of many surface materials, from rock-forming minerals to water ice to exotic volatiles and organic compounds. Identifying surface materials and mapping their distributions allows us to constrain interior processes such as cryovolcanism and aqueous geochemistry. The recent progress in understanding of Icy Satellite surface composition has been aided by the evolving capabilities of spacecraft missions, advances in detector technology, and laboratory studies of candidate surface compounds. Pioneers 10 and 11, Voyagers I and II, Galileo, Cassini and the New Horizons mission have all made significant contributions. Dalton (Space Sci. Rev., 2010 , this issue) summarizes the major constituents found or inferred to exist on the surfaces of the Icy Satellites (cf. Table 1 from Dalton, Space Sci. Rev., 2010 , this issue), and the spectral coverage and resolution of many of the spacecraft instruments that have revolutionized our understanding (cf. Table 2 from Dalton, Space Sci. Rev., 2010 , this issue). While much has been gained from these missions, telescopic observations also continue to provide important constraints on surface compositions, especially for those bodies that have not yet been visited by spacecraft, such as Kuiper Belt Objects (KBOs), trans-Neptunian Objects (TNOs), Centaurs, the classical planet Pluto and its moon, Charon. In this chapter, we will discuss the major Satellites of the outer solar system, the materials believed to make up their surfaces, and the history of some of these discoveries. Formation scenarios and subsequent evolution will be described, with particular attention to the processes that drive surface chemistry and exchange with interiors. Major similarities and differences between the Satellites are discussed, with an eye toward elucidating processes operating throughout the outer solar system. Finally we discuss the outermost Satellites and other bodies, and summarize knowledge of their composition. Much of this review is likely to change in the near future with ongoing and planned outer planet missions, adding to the sense of excitement and discovery associated with our exploration of our planetary neighborhood.
