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

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