Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
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
Jovian B Field
keV S+, O+
Magnetic Field Lines
Jupiter
Europa
Europa's OrbitO2
O2
O2
e-
O2
O2
H2Na
H2O
O2*
e-
Courtesy: R.E. Johnson
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
O+, S + e, H+
O2, H2, H2O
H2SO4X H2OSO2, H2S
Na2SO4XH2O ?Mg SO4XH2O ?Sx ,Other Na, S ?
(Na+,K+)
Mixing
Na, K, SO2, H2S, CO2
Implantation/Sputtering
Sx
H2CO3 X H2OCO2
Cx
Meteoroids
Organics? Metals?Salts?
Radiolysis
OpticalLayer
Surface
H2O2
From Johnson et al. (2004)
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
The Na sodium cloud: modelling and observation
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
ICE
LIQUID WATER
SOLID CORE
O2
O2H2
H2O
NaSO2?
IONS
Sodium cloud: A 3D Monte Carlo modelSodium 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
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Europa Orbit
Jupiter
Io Orbit
~2 kR
~5 kR
~1.2 kR
~1.5 kR
Na D2 emissions at 4 RE
Europa’s sodium exospheric variations?Europa’s sodium exospheric variations?
Source of Na is spatiallyand 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)
Sun/Earth
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Loss Flux of Na = 1.2107 Na/cm2/s (~70% by ionization, ~30% reaching > 1000 RE)
Exogenic source (from Io) =0.2 - 0.8106 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
Europa’s Alkali: endogenic or exogenic?Europa’s Alkali: endogenic or exogenic?
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
What should we look from JGO?
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Internal B field
internal radiation belt and observation of Aurora
emissions (Feldman et al. 2000)
Ganymede oxygen auroraMcGrath et al. (2008)
protected from energetic ions of less than 10 MeV and electrons impacts at mid latitude
Khurana et al. (2007)
Exploration des magnétosphères de Jupiter 14 Mars 2011 Meudon
Marconi, Icarus, (2007)
Ganymede
Atmosphere: O2 (1014 - 1015 cm-2) H everywhere (~9 1012)< Na 108 cm-2
Spectral features similar than Europa and Callisto S implanted on trailing side, formation of H2SO4, CO2 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