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Modeling Impacts on Icy Bodies: Applications to Saturn’s Moons

Modeling Impacts on Icy Bodies: Applications to Saturn’s Moons. Rhea. Tethys. Vanessa Lauburg TERPS Conference: December 7, 2004. Mimas. Motivation. Solar System Formation Formation of moons around gas giants Key: understand internal structures of satellites

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Modeling Impacts on Icy Bodies: Applications to Saturn’s Moons

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  1. Modeling Impacts on Icy Bodies:Applications to Saturn’s Moons Rhea Tethys Vanessa Lauburg TERPS Conference: December 7, 2004 Mimas

  2. Motivation • Solar System Formation • Formation of moons around gas giants • Key: understand internal structures of satellites • Proposed Method: analyze global damage from large impacts

  3. Goals of this Study • Relating Global Damage to Internal Structure • Simulate impacts on model satellites • Vary internal structure: core size and density • Measure damage: surface fragmentation, antipodal disruption • Correlation between structure and damage? • Simulate impacts on Saturn’s moons Rhea, Mimas, & Tethys • Which internal structure values best reproduce observed damage?

  4. Simulations • Code • 3D Smooth Particle Hydrodynamics • triaxial objects, fragmentation • Model Objects • targets: silicate cores, water ice mantles • impactors: undifferentiated water ice spheres • Analysis • peak surface velocity  seismic disturbances and terrain degradation • peak tensile strength  surface rupturing

  5. Results Fig. 1. Time Sequence: P wave passing through Tethys (basalt core), from t = 25 sec to t=300 sec (each frame advances 25 sec).

  6. Results • Seismic Energy Weakly Focused at Antipode • correlation: core radius and terrain damage • observed antipodal damage  core geometry? • Tethys Simulations Produce Greatest Damage • higher peak surface velocity and tensile stress than • on Mimas or Rhea • Expected! Tethys has the largest crater

  7. Results Fig. 2. 2D projections of surfaces of (a) test satellite, (b) Mimas, (c) Rhea, and (d) Tethys. Color scale: peak surface velocity.

  8. Conclusions • 3D simulations show weak antipodal focusing • strong focusing in previous 2D sims is due to • axisymmetry of the code • Core radius is correlated with antipodal damage • core density not as important • observations of terrain damage might provide info • about core geometry • Future Work • fragmentation results are inconclusive (inadequate resolution) • improve resolution, laboratory constraints on properties of ice

  9. References Bruesch, L.S., Asphaug, E., 2004. Modeling global impact effects on middle-sized icy bodies: applications to Saturn’s moons. Icarus 168, 457-466 De Pater, I., Lissauer, J., 2001. Planetary Sciences. Cambridge University Press, Cambridge, UK.

  10. Extra Bits Tethys (Odysseus) : D/DT = 0.38 Mimas (Herschel) : D/DM = 0.34 Rhea (Tirawa) : D/DR = 0.23 Density of impactor: 2-3.97

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