Chapter 891011 Part 2 Planets in General Standard Plane Comparative Planetology

1. Chapter 891011 Part 2 Planets in General Standard Plane Comparative Planetology Hartmann: Chapters 8 Planetary Interiors 9 Planetary Surfaces 10 Planetary Surfaces 11 Planetary Atmospheres

2. Comparative Planetology Formation history Interior geological activity Atmosphere atmospheric activity Magnetic field magnetic field activity Role of Planetary Size Role of Distance from Sun Role of Rotation

3. Comparative Planetology Formation history Interior geological activity Four basic properties of a planet: mass diameter mean density surface rock properties Basic concept is to use the surface features & materials as observational boundary conditions & then reason out the interior of the planet based on our knowledge of how these materials behave under high pressure and how resulting surface features are formed.

4. Processes that Shape Surfaces • Impact cratering Impacts by asteroids or comets • Volcanism Eruption of molten rock onto surface • Tectonics Disruption of a planet’s surface by internal stresses • Erosion Surface changes made by wind, water, or ice

5. Comparative Planetology Impact Cratering Volcanism (lava, outgassing) Cliffs Mountains tectonics Plains Ice Caps Magnetic field Rotation Distance from Sun Heating /Cooling of Interior Erosion (water, ice, wind, debris) Craters Volcanoes Cliffs Mountains Plains Ice Caps Magnetic field Axis tilt

6. Source of volcanism …. Core, Mantle, Crust, AtmosphereAll terrestrial planets have a similar structure: … a liquid core … a mantle of molten lava … a crust od solid, low-density rocks … an atmosphere (large range of compositions and pressures)

7. Shield Volcanoes Shield volcanoes are found above hot spots. Fluid magma chamber, from which lava erupts repeatedly through surface layers above.

8. Shield Volcanoes and Plate tectonics Tectonic plates moving over hot spots producing shield volcanoes result in chains of volcanoes Example: The Hawaiian Islands

9. All volcanoes on Venus and Mars are shield volcanoes Tectonic platesDO NOT occur on Venus and Mars This is beginning to look to be true for Mercury, too.

10. Volcanism appears to beresponsible for formation of Mercury’s widespread plains

11. 2009

12. Pancake domes are volcanoes that erupted thick molten rock. ~25 km in diameter, but only 1-2 km high. Similar to shield volcanoes in Hawaii, but thicker lava.

13. Volcanoes on Venus Many volcanoes,including both shield volcanoes and stratovolcanoes Sapas Mons (radar image) ~ 400 km (250 miles) 2 lava-filled calderas Lava flows

14. Volcanoes on Mars Highest and largest volcano in the Solar System. Tharsis volcanoes Valleys Olympus Mons

15. NASA

16. Venus is the only planet known to have coronae. (concentric tectonic stretch marks formed by hot rising plumes from the mantle) outward pressure from upwelling mantle material Coronae: Circular bulges formed by volcanic activity 300 km across

18. Jupiter’s Moons 64 known; new ones are still being discovered. Four largest moons already discovered by Galileo: The Galilean moons Callisto Io Europa Ganymede

19. Io: Bursting Energy --> Volcanic Activity Io Europa Ganymede Callisto

20. Ganymede: A Hidden Past Largest of the 4 Galilean moons. • Av. density = 1.9 g/cm3 • Rocky core • Ice-rich mantle • Crust of ice Bright terrain probably formed through flooding when surface broke

21. Ganymede • Largest moon in the solar system • Clear evidence of geological activity • Tidal heating plus heat from radio-active decay? Io Europa Ganymede Callisto

22. Callisto: The Ancient Face Heavily cratered --> OLD No metallic core: possibly silicate core Layer of liquid water, ~ 10 km thick, ~ 100 km below surface, probably heated by radioactive decay.

23. Callisto

24. Saturn’s moon: Titan’s Surface • Huygens probe provided first look at Titan’s surface in early 2005 • Liquid methane, “rocks” made of ice

25. The Moons of Uranus 5 largest moons are visible from Earth. 5 largest moons all tidally locked to Uranus.

26. Interiors of Uranus’s Moons Large rock cores surrounded by icy mantles.

27. Uranus’s Moon Miranda Most unusual of the 5 moons detected from Earth Ovoids: Oval groove patterns, probably associated with convection currents in the mantle, but not with impacts. 20 km high cliff near the equator Surface features are old; Miranda is no longer geologically active.

28. Neptune’s Moon Triton • Similar to Pluto, but larger • Evidence for past geological activity

29. Theoretical Techniques for Calculating Interior Conditions Equation of State ( P, T, rho): and for geologists changes of state (melting and solidifyng) is important to understand minerals

30. Differentiation: the process by which homogeneous material gets divided into masses of different composition and physical properties

31. Differentiation: the process by which homogeneous material gets divided into masses of different composition and physical properties

33. Other Observational that Check the Models for Planet Interiors: moment of inertia … kMR2 , k being coefficient of … {0. 1.} geometric oblateness … reflects mass distribution or departure from hydrostatic equilibrium form of gravitational field rotation rate … necessary for moment of inertia, geometric oblateness surface heat flow composition of neighbors (planets and or meteorites) magnetic field … strong field indicates a flluid core drilling and direct sampling seismic properties } Earth

34. A planet with a magnetic field indicates a fluidinterior in motion • Planetary magnetic fields are produced by the motion of electrically conducting liquids inside the planet • This mechanism is called a dynamo • If a planet has no magnetic field, that is evidence that there is little such liquid material in the planet’s interior or that the liquid is not in a state of motion

35. The magnetic fields of terrestrial planets are produced by metals such as iron in the liquid state • The stronger fields of the Jovian planets are generated by liquid metallic hydrogen or by water with ionized molecules dissolved in it