The Experts below are selected from a list of 15684 Experts worldwide ranked by ideXlab platform
T A Cassidy - One of the best experts on this subject based on the ideXlab platform.
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Effects of the External Environment on Icy Satellites
Space Science Reviews, 2010Co-Authors: Matthew H. Burger, Roland Wagner, Ralf Jaumann, T A CassidyAbstract:In order to understand the evolution of planetary Satellite Surfaces and atmospheres it is important to understand their external environments. In this paper we look at the interactions between plasma in planetary magnetospheres and Satellite atmospheres responsible for the production and loss of atmospheric mass. We focus on the processes which take place in the tenuous atmospheres of the Galilean Satellites and in the Enceladus water plume. We also review the impact histories of Satellites in the outer solar system, and compare the record of impacts in the inner and outer solar system.
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radiolysis and photolysis of icy Satellite Surfaces experiments and theory
Space Science Reviews, 2010Co-Authors: R.e. Johnson, Robert W. Carlson, T A Cassidy, Patrice Coll, F Raulin, M J Loeffler, K P Hand, R A BaragiolaAbstract:The transport and exchange of material between bodies in the outer solar system is often facilitated by their exposure to ionizing radiation. With this in mind we review the effects of energetic ions, electrons and UV photons on materials present in the outer solar system. We consider radiolysis, photolysis, and sputtering of low temperature solids. Radiolysis and photolysis are the chemistry that follows the bond breaking and ionization produced by incident radiation, producing, e.g., O2 and H2 from irradiated H2O ice. Sputtering is the ejection of molecules by incident radiation. Both processes are particularly effective on ices in the outer solar system. Materials reviewed include H2O ice, sulfur-containing compounds (such as SO2 and S8), carbon-containing compounds (such as CH4), nitrogen-containing compounds (such as NH3 and N2), and mixtures of those compounds. We also review the effects of ionizing radiation on a mixture of N2 and CH4 gases, as appropriate to Titan’s upper atmosphere, where radiolysis and photolysis produce complex organic compounds (tholins).
Jeffrey S. Kargel - One of the best experts on this subject based on the ideXlab platform.
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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.
T V Johnson - One of the best experts on this subject based on the ideXlab platform.
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non water ice constituents in the surface material of the icy galilean Satellites from the galileo near infrared mapping spectrometer investigation
Journal of Geophysical Research, 1998Co-Authors: T B Mccord, C A Hibbitts, G B Hansen, Roger N Clark, P D Martin, F P Fanale, J C Granahan, M Segura, D L Matson, T V JohnsonAbstract:We present evidence for several non-ice constituents in the surface material of the icy Galilean Satellites, using the reflectance spectra returned by the Galileo near infrared mapping spectrometer (NIMS) experiment. Five new absorption features are described at 3.4, 3.88, 4.05, 4.25, and 4.57 μm for Callisto and Ganymede, and some seem to exist for Europa as well. The four absorption bands strong enough to be mapped on Callisto and Ganymede are each spatially distributed in different ways, indicating different materials are responsible for each absorption. The spatial distributions are correlated at the local level in complex ways with surface features and in some cases show global patterns. Suggested candidate spectrally active groups, perhaps within larger molecules, producing the five absorptions include C-H, S-H, SO2, CO2, and C≡N. Organic material like tholins are candidates for the 4.57- and 3.4-μm features. We suggest, based on spectroscopic evidence, that CO2 is present as a form which does not allow rotational modes and that SO2 is present neither as a frost nor a free gas. The CO2, SO2, and perhaps cyanogen (4.57 μm) may be present as very small collections of molecules within the crystal structure, perhaps following models for radiation damage and/or for comet and interstellar grain formation at low temperatures. Some of the dark material on these Surfaces may be created by radiation damage of the CO2 and other carbon-bearing species and the formation of graphite. These spectra suggest a complex chemistry within the surface materials and an important role for non-ice materials in the evolution of the Satellite Surfaces.
Juan Cristobal Zagal - One of the best experts on this subject based on the ideXlab platform.
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evolutionary design of a Satellite thermal control system real experiments for a cubesat mission
Applied Thermal Engineering, 2016Co-Authors: Emanuel Escobar, Marcos Diaz, Juan Cristobal ZagalAbstract:Abstract This paper studies the use of artificial evolution to automate the design of a Satellite passive thermal control system. This type of adaptation often requires the use of computer simulations to evaluate fitness of a large number of candidate solutions. Simulations are required to be expedient and accurate so that solutions can be successfully transferred to reality. We explore a design process that involves three steps. On a first step candidate solutions (implemented as surface paint tiling patterns) are tested using a FEM model and ranked according to their quality to meet mission temperature requirements. On a second step the best individual is implemented as a real physical Satellite mockup and tested inside a vacuum chamber, having light sources imitating the effect of solar light. On a third step the simulation model is adapted with data obtained during the real evaluation. These updated models can be further employed for continuing genetic search. Current differences between our simulation and our real physical setup are in the order of 1.45 K mean squared error for faces pointing toward the light source and 2.4 K mean squared errors for shadowed faces. We found that evolved tiling patterns can be 5 K below engineered patterns and 8 K below using unpainted aluminum Satellite Surfaces.
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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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.
