Satellite120524

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Satellite120524

  1. 1. Formation of The Jovian and SaturnianSatellite SystemsTakanori Sasaki, Shigeru Ida (Tokyo Tech)Glen R. Stewart (U. Colorado)
  2. 2. Jovian System v.s. Saturnian System rocky rocky icy icy, undiff. Io Europa Ganymede Callisto mutual mean motion resonances (MMR) icy, undiff. only one big body Inside Titan. Global gravity field and sha pletely separated within Titan’s deep inter may contain a cold water-ammonia ocean water ice below (gray) and a floating ice/cl images show that the extent of separation density that is predominantly affected by t Titan dial ice-rock mixtures may display distinct degrees of internal differentiation. Impact- induced melting and/or intense tidal heating of Ganymede, locked in orbital resonances with the inner neighboring satellites Io and ries and gradual unmixing of ice and rock may also play a role for incomplete differentiation of icy satellites. References and Notes 1. L. Iess et al., Science 327, 1367 (2010). Europa, may have triggered runaway differ- 2. R. Jaumann et al., in Titan from Cassini-Huygens, R.H. Brown, J.-P. Lebreton, J. Hunter Waite, Eds. (Springer, entiation, but Callisto farther out from Jupiter New York, 2009), pp. 75–140.
  3. 3. Circum-planetary disk models Actively-Supplied Accretion Disk “Minimum Mass” Disk [Canup & Ward, 2002] [Mosqueira & Estrada, 2003] Inflow (gas + small solids) H RP ν = αcH ro rd × Only for Jovian system Figure 8: Left: Idealization of the initial Σ and assumed photospheric ○ Msatellites/Mplanet ~ 10-4 subnebula. The re-constituted mass of Io, Europa, and Ganymede det thick inner disk, while the mass of Callisto is spread out over the opticall inflow-produced accretion disk. [Canup & Ward, 2006] Inflowing gas and solids initially achieve just inside the centrifugal radius rc , while Callisto lies outside a transitio × Unrealistic initial conditions and outer disks. The transition region between in the inner and outer e balance across a region extending from the surface of the planet out to distance temperature is set to agree with the compositional constraints of the Ga ccrete into satellites throughout this region. The gas spreads viscously onto the [Tanigawa et al., 2012 JpGU] Stevenson, 1982; Mosqueira and Estrada, 2003a,b), which implies a Jovi ○ removal distance, rd with rd >> ro. Saturnian a planetary radius of ∼ 1.5 − 2 RJ consistent with planet formation moward to aDifference b/w ,Jovian and The half-thickness of the gas disk is 1a). Upper left: Critical mass at which migration stalls as a function of J using both vertically thermally stratified (solid and dotted curves), and v c is gas satellite systemsorbital frequency, with H/r ~ 0.1. After Canup and sound speed and Ω is × Difficult to make satellites(?) dashed curve). Gas drag is included. The solid curve corresponds to the dotted and dashed curves correspond to the SEMM model. The short-d [Sasaki et al., 2010; Ogihara et al., 2012] T model. Lower right: Migration and growth models for proto-Ganyme [Miguel, Sasaki & Ida, in prep.]; evolved backward in time from the location where it opens a gap to th size (∼ 1000 km) for a SEMM disk. Two models for growth are used. S Dotted curve: growth rate proportional to the disk surface density. Grow
  4. 4. Circum-planetary disk models Actively-Supplied Accretion Disk “Minimum Mass” Disk [Canup & Ward, 2002] [Mosqueira & Estrada, 2003] Inflow (gas + small solids) H RP ν = αcH ro rd × Only for Jovian system ○ Msatellites/Mplanet ~ 10-4 inflow-produced accretion disk. [Canup & Ward, 2006] Inflowing gas and solids initially achieve × Unrealistic initial conditions e balance across a region extending from the surface of the planet out to distance ccrete into satellites throughout this region. The gas spreads viscously onto the [Tanigawa et al., 2012 JpGU] ○ removal distance, rd with rd >> ro. Saturnianward to aDifference b/w ,Jovian and The half-thickness of the gas disk is c is gas satellite systemsorbital frequency, with H/r ~ 0.1. After Canup and sound speed and Ω is × Difficult to make satellites(?) [Sasaki et al., 2010; Ogihara et al., 2012] [Miguel, Sasaki & Ida, in prep.];
  5. 5. Canup & Ward (2002, 2006)Actively-Supplied Accretion Disk Uniform mass infall Fin from the circum-stellar disk Infall regions: rin < r < rc (rc ~ 30Rp) Diffuse out at outer edge: rd ~ 150Rp Infall rate decays exponentially with time Temperature: balance of viscous heating and blackbody radiation Viscosity: α model Inflow (gas + small solids) H RP ν = αcH ro rd
  6. 6. Overview of Sasaki et al. (2010) Circum-Planetary Disk Satellite FormationCanup & Ward, 2002, 2006 Ida & Lin, 2004, 2008, 2010Satellites formed in c.-p. disk Analytical solution forActively-supplied accretion disk accretion timescaleSupplied from circum-stellar disk type I migration timescale → Analytical solution for T, Σ trapping condition in MMR Adding New Ideas  Disk boundary conditionsDifference of Jovian/Saturnian systems is naturally reproduced.
  7. 7. The New IdeasJupiter inner cavity opened up gap in c.-s. disk  → infall to c.-p. disk stop abruptlySaturn no cavity did not open up gap in c.-s. disk → c.-p. disk decay with c.-s. disk Difference of “inner cavity” is from Königl (1991) and Stevenson (1974) Difference of gap conditions is from Ida & Lin (2004)
  8. 8. Jovian System inner cavity outer proto-satellite @corotation radius grow faster & migrate earlier Because the infall mass flux per unit area is constant, the total mass flux to satellite feeding zones is larger in outer regions.
  9. 9. Jovian System Type I migration is halted near the inner edge The outer most satellite migrates and sweeps up the inner small satellites.
  10. 10. Jovian System MMR Proto-satellites grow & migrate repeatedly They are trapped in MMR with the innermost satellite
  11. 11. Jovian System Total mass of the trapped satellites > Disk mass → the halting mechanism is not effective     → innermost satellite is released to the host planet
  12. 12. Jovian System after the gap opening → c.-p. disk deplete quickly
  13. 13. Saturnian System No inner cavity outer proto-satellite grow faster & migrate earlier
  14. 14. Saturnian System fall to Saturn Large proto-satellites migrate from the outer regions and fall to the host planet with inner smaller satellites
  15. 15. Saturnian System c.-p. disk depleted slowly with the decay of c.-s. disk
  16. 16. Monte Carlo Simulation (n=100) Parameters: Disk viscosity (α model) = 10 3 10 2 in = 3 ⇥ 10 5⇥ 10 6 6 yr Disk decay timescale Number of “satellite seeds” N = 10 20 
  17. 17. Results: Distribution of the number of large satellites Jovian Saturnian 40 80Total count of the case 60 20 40 20 0 0 0 1 2 3 4 5 6 7 0 1 2 3 4 number of produced satellites
  18. 18. Results: Distribution of the number of large satellites Jovian Saturnian 40 80Total count of the case 60 20 40 20 0 0 0 1 2 3 4 5 6 7 0 1 2 3 4 number of produced satellites inner two bodies: rocky icy satellite & outer two bodies: icy & large enough (~MTitan)
  19. 19. Results: Properties of produced satellite systems Jovian Saturnian 1e-3 Galilean Satellites Titan 1e-4Ms/Mp 1e-5 rocky component icy component 1e-6 0 10 20 30 0 10 20 30 a/Rp
  20. 20. Results: Properties of produced satellite systems Jovian Saturnian 1e-3 Galilean Satellites Titan 1e-4Ms/Mp 1e-5 rocky component icy component 1e-6 0 10 20 30 0 10 20 30 a/Rp inner three bodies the largest satellite are trapped in MMR has ~90% of total satellite mass
  21. 21. Summary• Jovian Satellite System v.s. Saturnian Satellite System Difference of size, number, location, and compositions• Satellite Accretion/Migration in Circum-Planetary Disk Canup & Ward (2002, 2006) + Ida & Lin (2004, 2008, 2010)• The Ideas of Disk Boundary Conditions Difference of inner cavity opening and gap opening conditions• Monte Carlo Simulations Difference of Jovian/Saturnian system are naturally reproduced [Sasaki, Stewart & Ida (2010) ApJ 714, 1052]

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