Bourdarie S. Burger M
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_______________ Bourdarie S. Radiation belts and their interactions with solid bodies In ANALYSIS: External processes: interact. with atmosph. and space environ. (Thursday afternoon) _______________ Burger M University of Maryland-Baltimore County and NASA/GSFC Interactions between satellites and magnetospheres in the outer solar system In ANALYSIS: External processes: interact. with atmosph. and space environ. (Thursday afternoon) The satellites of Jupiter and Saturn interact with the planetary magnetospheres to produce tenuous atmospheres or exospheres. These atmospheres are stripped away by sputtering and ionization by magnetospheric plasma to produce neutral gas clouds and supply fresh plasma. I will briefly review three cases in the outer solar system of the interactions between satellite atmospheres and the magnetospheres in which they are embedded. Gases in Io's atmosphere are supplied by the volcanoes and achieve a rough balance with frost on the surface. Interactions between the atmosphere and surface with plasma and high energy particles in Jupiter's magnetosphere produce fresh ions which are swept up by the magnetic field and form the Io plasma torus, a ring of plasma encircling Jupiter which extends from inside Io's orbit out beyond Europa. Neutrals also escape from Io through both slow and fast escape processes. Sputtering of the atmosphere results in slowly (~2 km/s) escaping neutrals which form a partial torus neutral cloud orbiting Jupiter. Resonant charge exchange between Na+ ions in the plasma torus and Na in the atmosphere produce fast neutrals which form a sodium jet whose orientation varies with Jupiter's magnetic field. W hen high energy ions impact Europa's surface, H2O, O2, and H2 are ejected. The hydrogen escapes from Europa, and most of the water molecules return to the surface and stick. The O2, however, neither immediately escapes nor returns to the surface, but instead builds up forming a tenuous atmosphere. This atmosphere is ultimately limited by its interaction with the Io plasma torus: charge exchange with the ions and dissociation and ionization by the electrons remove material and produce emissions which have been observed by the Hubble Space Telescope and Cassini. W hile Enceladus does not have a full exosphere, the interactions between its south polar plume and Saturn's magnetosphere are similar to the atmosphere/plasma interactions at Jupiter. H2O escaping from Enceladus forms a neutral torus around Saturn. Charge exchange and neutral-neutral reactions in this torus redistribute neutrals throughout the magnetosphere, providing an extended source of plasma. _______________ Cassidy T. Space weathering and magnetospheric interactions In ANALYSIS: External processes: interact. with atmosph. and space environ. (Wednesday morning) Most of the icy satellites in our solar system are embedded in their parent planet's magnetosphere, where they are exposed to energetic ion and electron bombardment that erodes and alters their surfaces. Ion erosion (sputtering) launches molecules on ballistic arcs above the surface, forming tenuous "atmospheres" representative of surface composition and space weathering processes. The incoming plasma also alters surface composition by breaking molecular bonds and introducing new material to the surface. I will discuss these processes and their importance on the icy satellites of Jupiter and Saturn and Saturn's E ring. _______________ Coll P. Tholins œ a way to understand the organic complexity of Titan In DATA/FACTS : Physics and chemistry of ices and organics (Tuesday afternoon) _______________ Coradini A. A. Coradini, G. Magni, D. Turrini Initial conditions in circumplanetary nebulae in IMPLICATIONS : Origin of the moons (Friday morning) Early stages of planetary satellites formation are possibly related to the condition characterizing Jupiter and Saturn subnebulae. The nature and life-time of these nebulae depend, in turn, on the formation scenario assumed for giant planets' formation. If giant planets form through rapid gas-accretion onto a previously formed solid core, then the formation of planetary subnebulae, which then evolve into circumplanetary disks, is a by- product of the planetary formation process. During the first rapid accretion phases, disks are relatively hot, turbulent and partially embedded in their planets‘ atmospheres. At later stages, when the accretion slows down, the disk's turbulence decreases accordingly and different ices can condense. Understanding the thermodynamical evolution of the disks surrounding the giant planets is mandatory to understand the origin of the satellites. W e will describe the disk's thermodynamical state at the end of the accretion phase and we will compare its chemistry with present data on the composition of the satellites. _______________ Coustenis A. - Lunine J. LESIA Observatoire de Meudon Analysis of Titan surface and atmosphere infrared data" In ANALYSIS : External processes: interact. with atmosph. and space environ. (Wednesday morning) Titan observations in the far- and near-infrared have led to a better comprehension of the complex chemical and surface composition of the satellite. I will discuss methods for analyzing Cassini-Huygens and ground-based data and the impact this investigations have had on our understanding of the satellite's processes. _______________ Dalton B. Jet Propulsion Laboratory Spectroscopy of Planetary Ices in Support of Spacecraft Missions In DATA/FACTS : Physics and chemistry of ices and organics (Tuesday morning) The advent of modern imaging spectrometers has created exciting opportunities to discern the composition and distribution of surface materials on solid bodies of the Solar System. In the outer Solar System, recent and planned missions have begun to return a vast library of observations specifically concerned with the icy satellites. Interpreting this data and understanding the operative processes that have led these worlds to their present states, requires a concerted and collaborative effort which combines laboratory spectroscopy at relevant temperatures, wavelengths, viewing geometries and sample characteristics, with advanced automated spectral and image processing techniques which take into account the characteristics, capabilities and limitations of modern instrumentation. _______________ Durham W . Massachusetts Institute of Technology, Cambridge, MA, USA Rheology of icy materials under planetary conditions In DATA/FACTS : Physics and chemistry of ices and organics (Tuesday morning) This review of the rheological properties of planetary ices as seen from the viewpoint of laboratory experiments will cover six topics: (1) a review of the basic language of rheology– the study of the rate at which materials undergo a permanent change of shape under deviatoric stress –and the practical methods by which one goes about determining flow properties under planetary conditions of high pressure, low temperature, and low strain rate; (2) a comparison of the relative strengths of single-phase ices, from the very strong sulfate hydrate salts and clathrates, to water ice phases I through VI, to weaker ices of ammonia and carbon dioxide; (3) a discussion of grain-size-sensitive vs. grain-size-insensitive mechanisms of flow in crystalline materials and current ideas about dynamic changes in grain size, with an emphasis on ice I in the laboratory and in the outer layers of icy moons; (4) an introduction to the complexity of the rheological behavior of two- and multi-phase materials, with examples of several ice-ice systems; (5) a presentation of new results in one specific two-phase system, that of water ice plus silicate dust; and (6) a discussion of future directions for the field, including the rheological behavior of ice + liquid mixtures with and eye toward the crust of Titan. The objective here is to communicate a practical knowledge of the strength differences between various ices, and a basic understanding of the more important factors that influence those strengths in the planetary setting. _______________ Fortes D. STFC Advanced Research Fellow Department of Earth Sciences University College London Instability of hydrates in planetary interiors In DATA/FACTS : Physics and chemistry of ices and organics (Tuesday morning) Experimental studies in recent years have revealed that, in general, most ofthe hydrated phases expected in icy satellite interiors are unstable with respect to lower hydrates as pressure is increased. My work at UCL on ammonia dihydrate and MgSO4 7- and 11-hydrates is reported, and agrees with the trend observed also in Na2SO4 hydrates and in clathrate hydrates towards stabilisation of lower hydrates with pressure. It is predicted that sulfuric acid hydrates will behave in the same way, the octahydrate giving way to lower hydrates at kilobar pressures, for example. The volume changes (and change in transport properties) associated with these dehydration reactions may have significant consequences for the internal structure and evolution of icy satellites. The presence of 'unexpected'phases on the high-pressure liquidus may also have consequences for the subsurface ocean chemistry in these bodies. _______________ Giese B. DLR, Institute of Planetary Research, Rutherfordstr. 2, 12489 Berlin, Germany ithosphere dynamics: flexure and relaxation in ANALYSIS : Past and present dynamics of icy surfaces (Wednesday morning) A lithosphere is not a fundamental quality of a planetary body; it instead is the expression of the response of the near-surface of a planet