Medium and Large Icy Worlds

1. Medium and Large Icy Worlds

2. Medium and Large Icy Worlds • Enough self-gravity to be spherical. • Metal/rock core, ice mantle and crust. • Some geological activity • Two main locations: • Larger Icy moons orbiting gas giant planets • Largest objects in Kuiper belt in the outermost solar system (Pluto, Sedna, Quoaor and others)

3. Ch.11.2, A Wealth of Worlds: Moons of Ice and Rock • Our goals for learning • What kinds of moons orbit Gas Giant planets? • Why are Jupiter’s Galilean moons so geologically active? • What is special about Titan and other major moons of the solar system? • Why are icy moons more geologically active than rocky planets of the same size?

4. What kinds of moons orbit Gas Giant planets? • Small moons (< 300 km) • No geological activity • Medium-sized moons (300-1,500 km) • Geological activity in past • Large moons (> 1,500 km) • Ongoing geological activity

5. Medium & Large Moons • Formed in orbit around gas giant planets. • Circular orbits in same direction as planet rotation.

6. Jupiter’s Galilean Moons

7. Why are Jupiter’s Galilean moons so geologically active?

8. Io 12th largest world

9. Active sulfur volcanism

10. Global Volcanism seen in IR Hotspots indicating active eruptions

11. Io’s Volcanic Activity • Io is the most volcanically active body in the solar system, but why?

12. Io’s Volcanoes • Volcanic eruptions continue to change Io’s surface

13. Changing volcanoes over 2 years

14. Io Eruptions -New Horizons Flyby Feb. 2007 300-kilometer (190-mile) Tvashtar eruption plume

15. Other Processes • Thrust faults produce mountains 7 km (23,000 ft) high • Mass wasting

16. Tidal Heating Io is squished and stretched as it orbits Jupiter But why is its orbit so elliptical?

17. The tugs add up over time, making all 3 orbits elliptical. Orbital Resonances Every 7 days, these 3 moons line up.

18. Thought Question How does Io get heated by Jupiter? a) Auroras b) Infrared Light c) Jupiter pulls harder on one side than the other d) Volcanoes

19. Thought Question How does Io get heated by Jupiter? a) Auroras b) Infrared Light c) Jupiter pulls harder on one side than the other d) Volcanoes

20. Europa -13th largest world

21. Europa -13th largest world

22. Tidal stresses crack Europa’s surface ice.

24. Europa’s Ocean: Waterworld?

25. Inside Europa • Secondary magnetic field (requires liquid) • Broken disrupted surfaces from flowing ice • Surface covered in faults -some areas spread apart. • Conclusion: • Liquid interior layer -a global ocean

26. Europa’s interior also warmed by tidal heating

27. Ganymede -8th largest world • Largest moon in the solar system

28. Ganymede • Clear evidence of geological activity • Tidal heating plus heat from radio-active decay? • Has a magnetic Field that varies.

30. Callisto -11th largest world Valhalla -largest crater in the solar system 1875 miles across

31. Callisto • “Classic” cratered iceball. • No tidal heating, no orbital resonances. • But it has 2ndary magnetic field !?

32. The tugs add up over time, making all 3 orbits elliptical. Orbital Resonances Every 7 days, these 3 moons line up.

33. What have we learned? • What kinds of moons orbit jovian planets? • Moons of many sizes • Level of geological activity depends on size • Why are Jupiter’s Galilean moons so geologically active? • Tidal heating drives activity, leading to Io’s volcanoes and ice geology on other moons