Evdokimova N., Korablev O., Marchenkov K., Rodin A., Malova H., Podzolko M., Zelenyi L. Space Research Institute(IKI), Moscow, Russia All images credit: NASA / JPL / Brown University

Jupiter system 1. Io 2. Europa 3. Ganymede 4. Callisto 5. Amalthea 6. Himalia 7. Elara 8. Pasiphae 9. Sinope 10. Lysithea 11. Carme 12. Ananke 13. Leda 14. Thebe 15. Adrastea 16. Metis 17. Callirrhoe 18. Themisto 19. Megaclite 20. Taygete 21. Chaldene 22. Harpalyke 23. Kalyke 24. Iocaste 25. Erinome Jupiter has ~50 satellites! 26. Isonoe 27. Praxidike 28. Autonoe 29. Thyone 30. Hermippe 31. Aitne 32. Eurydome 33. Euanthe 34. Euporie 35. Orthosie 36. Sponde 37. Kale 38. Pasithee 39. Hegemone 40. Mneme 41. Aoede 42. Thelxinoe 43. Arche 44. Kallichore 45. Helike 46. Carpo 47. Eukelade 48. Cyllene 49. Kore 50. Herse ИоИо Каллис то omy

Galilean Satellites of Jupiter Jupiter has ~50 satellites! 1:2:4 Laplace resonance ИоИо Ganymede Europa Callisto omy MGS view. Image credit: NASA / JPL Four Galilean satellites – since 1610 Io

Activity of Galilean satellites GanymedeEuropaCallistoIo Adapted from Bagenal et al., 2004 Tidal Energy Impact cratering Tectonism Magmatism Distance from Jupiter. Proportions are not kept

Ganymede: General information Diameter: D(Gan) = 5262,4 km ~ 1.5D(Moon) ~ 1.08D(Mercury) - the largest (not the heaviest!) satellite of Solar System; Mass: M(Gan) ~1.48*10 23 kg ~ 2M(Moon) Density: ρ (Gan) ~ kg/m 3 Orbital parameters: Orbital period: T(Gan) = T(Earth) ~ days Semi-major axis: a = km Eccentricity: e = (range: ÷ ) Inclination: i = 0,204° (range: 0,05° ÷ 0.32°) Image credit: NASA / JPL

Breakthrough missions having explored Ganymede 1977 – launch Voyager -1 and – Galileo mission – the best observation of Ganymde 2006 – launch New Horizons. Now it is going to Pluto Ganymede flyby

Galileo mission ( ) 18 Oct 1989 Launch (16:53:40 UT) 10 Feb 1990 Venus Flyby 8 Dec 1990 First Earth Flyby 29 Oct 1991 Asteroid Gaspra Flyby 8 Dec 1992 Earth Flyby 2 28 Aug 1993 Asteroid Ida Flyby Jul 1994 Comet Shoemaker-Levy 9 Impact Observations 13 Jul 1995 Probe Release 7 Dec 1995 Probe Descent (22:04 UT - 23:02 UT) 8 Dec 1995 Jupiter Orbit Insertion (00:27 UT) 6 Sep 1996 Ganymede Encounter 2 4 Nov 1996 Callisto Flyby 3 19 Dec 1996 Europa Flyby 4 20 Feb 1997 Europa Flyby 6 5 Apr 1997 Ganymede Flyby 7 10 Feb 1998 Europa Flyby May 2001 Callisto Flyby 6 Aug 2001 Io Flyby Oct 2001 Io Flyby Jan 2002 Io Flyby 33 5 Nov 2002 Amalthea Flyby 31 Mar 2003 Jupiter Observations Complete 21 Sep 2003 Jupiter Impact (18:57:18 UT) Date: 3 Aug 1989 Image credit: NASA / JPL Date: 18 Oct 1989

Galileo mission ( ) 18 Oct 1989 Launch (16:53:40 UT) 10 Feb 1990 Venus Flyby 8 Dec 1990 First Earth Flyby 29 Oct 1991 Asteroid Gaspra Flyby 8 Dec 1992 Earth Flyby 2 28 Aug 1993 Asteroid Ida Flyby Jul 1994 Comet Shoemaker-Levy 9 Impact Observations 13 Jul 1995 Probe Release 7 Dec 1995 Probe Descent (22:04 UT - 23:02 UT) 8 Dec 1995 Jupiter Orbit Insertion (00:27 UT) 6 Sep 1996 Ganymede Encounter 2 4 Nov 1996 Callisto Flyby 3 19 Dec 1996 Europa Flyby 4 20 Feb 1997 Europa Flyby 6 5 Apr 1997 Ganymede Flyby 7 10 Feb 1998 Europa Flyby May 2001 Callisto Flyby 6 Aug 2001 Io Flyby Oct 2001 Io Flyby Jan 2002 Io Flyby 33 5 Nov 2002 Amalthea Flyby 31 Mar 2003 Jupiter Observations Complete 21 Sep 2003 Jupiter Impact (18:57:18 UT) Date: 3 Aug 1989 Image credit: NASA / JPL Date: 18 Oct 1989

Spacecraft instruments: Solid State Imaging Camera (SSI) Near Infrared Mapping Spectrometer (NIMS) Photopolarimeter-Radiometer (PPR) UltraViolet Spectrometer (UVS) Magnetometer Energetic particles detector Plasma wave spectrometer Dust detector Heavy ion counter Galileo’s look at Ganymede ( ) Atmospheric probe: Helium abundance detector Atmospheric structure instrument Neutral mass spectrometer Nephelometer Net flux radiometer Lightning and radio emission detector the highest spatial resolution ( ~12 m/px); the closest flyby ( ~264 km to surface) Galileo mission ( )

Ganymede: previous results 1.Internal structure 2.Geology, surface morphology 3.Atmosphere, exosphere 4.Magnetosphere Gravity field measurements (Galileo) Magnetic field measurements, energetic particles(Galileo), aurorae(HST) Surface features analysis(from images: Voyager, Galileo), mineral composition (from spectroscopy, Earth-based radar) Measurement types Problem UV spectroscopic measurments, Voyager-1, HST, Galileo

Strongly differentiated internal structure: 1) Liquid core : Fe, (+FeS?), R~ km 2) Rock mantle(silicates, Mg-rich?) 3) Ice mantle (liquid-solid: high-pressure phase), km 4) Ice crust ( km) (more lighter) Ice phase state and lattice type are unknown… Ice near its melting becomes a low-viscosity solid => => Ice mantle convection like Earth rock mantle? rocks ~60%, ices~40% (if ρ~1,94 g/cm – Pioneer, Voyager) 1. Internal structure

Crust deformations: tides Callisto tidal flexing < Ganymede tidal flexing < Europe tidal flexing Tides from interior model of Ganymede: In the presence of a liquid ocean: tide can exceed 7 m peak-to-peak variation Without an ocean: tidal amplitudes are less than 0.5 m ( Moore, 2003) Mass anomalies 2 surface mass anomalies? one a positive mass at high latitude and the other - a negative mass at low latitude. No obvious geological features that can be identified with the anomalies. (Galileo data, Anderson 2004) 1. Internal structure

Open questions Interiors structure Existence of liquid mantle Origins of mass anomalies Ice structure and form Role of tidal heating at present and in the past Etc… 1. Internal structure Possible solutions and related payload -Seismometer -Thermal mapping -Gravity field mesurements -Librations measurements (e.g. by stellar sensor) -Etc?…

 Numerous traces of active geological processes in early history: tectonism, volcanism (caldera-like features- Spaun,2001; cryovolcanism –Schenk, 2001), etc…  Numerous impact craters  2 different types of surface: 2. Geology, surface morphology Galileo, 140m/px *both types may be reticulate 2 - Bright terrain(2) ~ 2/3 of Ganymede The youngest; less cratered; lanes through dark terrain 1 - Dark terrain ~ 1/3 of Ganymede The oldest (~4Gy); heavily cratered; palimpsets; Callisto-like

 Numerous traces of active geological processes in early history: tectonism, volcanism (caldera-like features- Spaun,2001; cryovolcanism –Schenk, 2001), etc…  Numerous impact craters  2 different types of surface: 2. Geology, surface morphology Galileo, 140m/px *both types may be reticulate DEM of topography (same scene) Schenk, 2001

Global map based only on low resolution images Galileo/Voyadger data 2. Geology, surface morphology

Geological units Morphology map based on Galileo mosaic Prockter, 1998

Surfical rocks chemical composition (telescopic observations; Galileo/NIMS spectroscopic data: T.McCord, 1998, etc) - mainly H 2 O ice (50-90%) - presence of CO 2 ice (Hibbits, 2003) - signs of SO 2, NH 3 - hydrated minerals (MgSO 4 ·nH 2 O, Na 2 Mg(SO 4 ) 2 ·4H 2 O,...? - still under studies - unknown spectral features *adsorb. bands 3.7, 3.88, 4.05, 4.25 µm, etc - unknown materal: *darker and redder then water ice: carbon-rich meteorite/mix of clays/organics component? tholin? - still under studies… 2. Geology, surface morphology

Surfical rocks chemical composition (telescopic observations; Galileo/NIMS spectroscopic data: T.McCord, 1998, etc) - mainly H 2 O ice (50-90%) - presence of CO 2 ice (Hibbits, 2003), O 2 - signs of SO 2, NH 3 - hydrated minerals (MgSO 4 ·nH 2 O, Na 2 Mg(SO 4 ) 2 ·4H 2 O,...? - still under studies - unknown spectral features *adsorb. bands 3.7, 3.88, 4.05, 4.25 µm, etc - unknown materal: *darker and redder then water ice: carbon-rich meteorite/mix of clays/organics component? tholin? - still under studies… Carlson et al., NIMS/Galileo mapping 2. Geology, surface morphology

Surface temperature distribution (PPR/Galileo data) Need for further studies of surfical thermophysical properties! Night side Heat radiation ~ 60 µm Tmin=80 K (observed) Day side 2. Geology, surface morphology

Open questions Searching for specific substances: -non-organic components: sulfates, hydrated minerals -organics: tholin, etc; Altimetry and geologic mapping; Thermal inertia data; (Water) ice microstructure; Geological processes: current and past Confirmation of cryovolcanism hypotheses Age of “dark” and “light” terrains Vertical structure of crust beneath dark terrain …. etc 2. Geology, surface morphology Possible solutions and related payload Elemental analysis: -Laser-stimulated emission UV spectroscopy -Laser-stimulated mass spectroscopy Analysis of species: -IR imaging spectroscopy -GCMS -Raman spectroscopy -DLS spectroscopy Mineralogical & morphological analysis: -Multispectral camera -IR imaging spectroscopy -Microscope …etc?

-Very tenuous one: ~10 16 cm -2 O, O 2, H, H 2, H 2 O, OH, … ? sublimation and sputtering from icy surface ? -Frozen and trapped gases in the Ganymede surface? -Micron-sized dust halo loosely bound by gravity – ice grains, the result of meteorite impacts 3. Atmosphere. Exosphere Ganymede does have atmosphere!

Results of Dust detector/Galileo 3. Atmosphere. Exosphere Kruger, 2000

Open questions Abundance of volatiles, isotopes Sources/sinks, interactions with the surface and interiors Exosphere, escape mechanisms Photochemistry Interactions with Jovian magnetosphere Thermal and non-thermal heating, kinetics, dynamics (tides?) Dust particles acceleration and escape 3. Atmosphere. Exosphere Possible solutions and related payload Mass-spectrometry Radio occultations between the orbiter and lander Microwave sounding from the orbiter IR heterodyne sounding from the orbiter or lander

4. Magnetosphere

Ganymede’s magnetic field = internal +induced magnetic fields The origin of internal m.f. is the dynamo mechanism due to convection of core forming liquid materials in Ganymede’s core (Fe- FeS ) Hauck et al., JGR, 2006 Induced magnetic field is due to time varying component of the externally imposed Jupiter’s magnetic field. Source: electrical conductivity of a liquid water layer bearing electrolytes such as salts and acids. Kivelson et al., Icarus, 2002 Magnetic moment M=1,3×10 13 Т·м 3 ~ three times greater than Mercury’s magnetic moment M L~4-5 RG ~ km Ganymede is surrounded by a corona of hot oxygen atomes Eviator et al., PSS, 2001 Region of unstably trapped plasma particles; convection region. Kivelson et al., JGR, 1998 Ganymede’s magnetic field at equator ~ 720 nT Jupiter’s magnetic field ~120 nT Induced magnetic field ~ 60 nT

Ganymede’s interaction with the Jupiterian magnetosphere Ganymede’s magnetosphere From presentation by D.Titov 4. Magnetosphere

Regions of high-energy ions+electrons E~100 keV Interaction with Jupiter’s magnetic field No bow shock: velocity of magnetospheric flow is sub- sonic Kivelson et al., 2001 Ultraviolet auroral brightness (Eviator et al., 2001) Ionosphere Open field lines are connected to Jupiter’s polar magnetic field. Field-aligned currents in Alfven wings ~ 1.2*106A Jia et al., JGR, 2009 Upstream Reconnection line Downstream reconnection line Plasma flows. Magnetsopheric convection. Z X Alfven wings Asymmetrical Magnetopause

Charged particle flux and radiation dose equatorial profiles at Jupiter Equatorial profiles of radiation doses under 0.27, 1, 2.2 and 5 g/cm 2 shielding, and separately dose under 2.2 g/cm 2 from protons only near Jupiter. GanymedeIoAmaltheaEuropaGanymedeIoAmaltheaEuropa Equatorial profiles of the integral fluxes of E > 0.5, >2 and >10 MeV electrons and E > 2, >10 and >30 MeV protons at Jupiter.

Open questions: Sources of internal and induced magnetic fields Plasma convection and transfer in Ganymede’s magnetosphere Structure of the ionospheric current system Particle acceleration mechanisms Dynamics of heavy ions in polar and equatorial regions; their role in auroral brightness in Ganymede Influence of Ganymede to Jupiter’s auroras 4. Magnetosphere

Conclusions Ganymede is exceptionally challenging target for Russian and international space exploration program Lots of hot topics to remain hot for the next 15(?) years Strong, multidisciplinary community is needed