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Exosphere/Magnetosphere and sputtering F. Leblanc LATMOS/IPSL, France

Exosphere/Magnetosphere and sputtering F. Leblanc LATMOS/IPSL, France. The example of Europa. Europa in the Jovian magnetosphere. e -. keV S + , O +. Courtesy: R.E. Johnson. Magnetic Field Lines. O 2. O 2 *. Na. O 2. H 2. e -. H 2 O. Jupiter. O 2. Europa. O 2. O 2.

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Exosphere/Magnetosphere and sputtering F. Leblanc LATMOS/IPSL, France

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  1. Exosphere/Magnetosphere and sputtering F. Leblanc LATMOS/IPSL, France

  2. The example of Europa

  3. Europa in the Jovian magnetosphere e- keV S+, O+ Courtesy: R.E. Johnson Magnetic Field Lines O2 O2* Na O2 H2 e- H2O Jupiter O2 Europa O2 O2 Europa's Orbit Jovian B Field

  4. Implantation/ Sputtering Meteoroids Radiolysis e, H+ O+, S + (Na+,K+) O2, H2, H2O Na, K, SO2, H2S, CO2 Surface SO2, H2S H2O2 Organics? Metals? Salts? H2SO4X H2O Sx Optical Layer CO2 H2CO3 X H2O Cx Na2SO4XH2O ? Mg SO4XH2O ? Sx,Other Na, S ? Mixing From Johnson et al. (2004)

  5. The Na sodium cloud: modelling and observation

  6. Sodium cloud: A 3D Monte Carlo model • O2 atmosphere • Gravity fields and Solar pressure • Ionization of the Na atoms by electron impact • Trailing/leading anisotropy of the ejected flux • Energy distribution of the ejected particles IONS O2 Na O2 H2 SO2? H2O ICE LIQUID WATER SOLID CORE

  7. Europa’s sodium exospheric variations? Na D2 emissions at 4 RE Source of Na is spatially and temporally variable: Variations of the ejecta flux: by ~2 vs centrifugal latitude by ~21 vs Europa longitude Trailing - Leading recycling of the Na?  Fresh injections of energetic ions? Europa Orbit ~5 kR ~2 kR Jupiter ~1.5 kR Io Orbit ~1.2 kR Sun/Earth Leblanc et al. (2005)

  8. Europa’s Alkali: endogenic or exogenic? Loss Flux of Na = 1.2107 Na/cm2/s (~70% by ionization, ~30% reaching > 1000 RE) Exogenic source (from Io) =0.2 - 0.8106 Na/cm2/s (Leblanc et al. 2005) Na/ K ratio (~25) differs from that at Io (~10) Loss rate (~27) > Implantation Rate (~20) Not exogenic (Johnson et al. 2002)  Endogenic sources of Na and K species Observed sodium sputtered from ice Not directly from a mineral / salt Characteristic of trace species in ice

  9. What should we look from JGO?

  10. Ganymede oxygen aurora McGrath et al. (2008) • Internal B field • internal radiation belt and observation of Aurora emissions (Feldman et al. 2000) Khurana et al. (2007)  protected from energetic ions of less than 10 MeV and electrons impacts at mid latitude

  11. Atmosphere: O2 (1014 - 1015 cm-2) H everywhere (~9  1012) < Na 108 cm-2 Marconi, Icarus, (2007) Ganymede Spectral features similar than Europa and Callisto S implanted on trailing side, formation of H2SO4, CO2 also seen inside dark terrains (radiolysis)

  12. Objectives: geochemical evolution of Ganymede's surface and interior composition • Ganymede trace species from Orbiter: • energetic particles act on Ganymede like matrix assisted SIMS •  • allow ejection of trace species that can be associated to specific surface features and magnetospheric structures • Ganymede bulk composition from Orbiter: • Measurement of the escape rates of elemental species provide key information on interior composition

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