ExosphereMagnetosphere and sputtering F Leblanc LATMOSIPSL France Exploration
Exosphere/Magnetosphere and sputtering F. Leblanc LATMOS/IPSL, France Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
The example of Europa Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Europa in the Jovian magnetosphere e- ke. V S+, O+ Courtesy: R. E. Johnson Magnetic Field Lines O 2 O 2* Na e- H 2 O Jupiter Europa's Orbit O 2 O 2 Jovian B Field Exploration des magnétosphères de Jupiter H 2 14 Mars 2011 Meudon
Implantation/ Sputtering (Na+, K+) O+, S + Meteoroids Radiolysis e, H+ O 2, H 2 O Na, K, SO 2, H 2 S, CO 2 SO 2, H 2 S Organics? Metals? Salts? Mixing H 2 SO 4 X H 2 O H 2 CO 3 X H 2 O Sx CO 2 H 2 Optical Layer Cx Na 2 SO 4 XH 2 O ? Mg SO 4 XH 2 O ? Sx , Other Na, S ? Exploration des magnétosphères de Jupiter Surface From Johnson et al. (2004) 14 Mars 2011 Meudon
The Na sodium cloud: modelling and observation Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Sodium cloud: A 3 D Monte Carlo model IONS • O 2 atmosphere • Gravity fields and O 2 Solar pressure O 2 Na H 2 • Ionization of the Na SO 2? atoms by electron H 2 O impact ICE • Trailing/leading LIQUID WATER anisotropy of the ejected flux SOLID CORE • Energy distribution of the ejected particles Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Europa’s sodium exospheric variations? Na D 2 emissions at 4 RE Europa Orbit ~5 k. R ~2 k. R Jupiter ~1. 5 k. R Io Orbit ~1. 2 k. R Sun/Earth 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? Leblanc et al. (2005) Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Europa’s Alkali: endogenic or exogenic? Loss Flux of Na = 1. 2 107 Na/cm 2/s (~70% by ionization, ~30% reaching > 1000 RE) Exogenic source (from Io) =0. 2 - 0. 8 106 Na/cm 2/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 Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
What should we look from JGO? Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Ganymede oxygen aurora Mc. Grath et al. (2008) Internal B field Þ internal radiation belt and observation of Aurora emissions (Feldman et al. 2000) Khurana et al. (2007) protected from energetic ions of less than 10 Me. V and electrons impacts at mid latitude Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Atmosphere: O 2 (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 H 2 SO 4, CO 2 also seen inside dark terrains (radiolysis) Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
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 Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
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