1. The Giant Planets
Jovian Planets

2. The Giant Planets Four giant (or “Jovian”) planets:
Planet Distance Orbital
from Sun Period
Jupiter AU yrs
Saturn
Uranus
Neptune
All have:
rings
one or more large satellites
many small satellites (probably lots undiscovered)
Jovian Planets

3. Exploration of the Giant Planets
Most information from space probes
Moons, rings, weather, magnetic fields
Technically difficult
Far away, long flight times
Hazards: meteors, cold, radiation
Jovian Planets

4. Past and current spacecraft
Pioneer 10 and 11 (early 1970s)
Voyagers 1 and 2 (1977 to 1989)
Galileo (Jupiter and moons)
Atmospheric probe
Dec to 21 Sept. 2003
Cassini (Saturn and rings)
At Saturn since 2004
Huygens atmospheric probe to Titan (largest moon)—landed Jan. 14, 2005
Jovian Planets

5. Jupiter, the Giant
Jovian Planets

6. Jupiter: largest of all
Mass: 318 times Earth
Radius: 11 times Earth (flattened at poles)
Density: 1.3 gm/cm3 (Earth: 5.5)
Mostly hydrogen, helium, little rock or iron
Rotation: 10 hours (faster at equator than at poles, not a solid surface)
Jovian Planets

7. Jupiter's atmosphere Visible disk is clouds
Frozen ammonia plus hydrocarbons (“smog”)
Pattern of light, dark bands
Driven by internal heat (convection and rotation)
Oval patterns are storms like hurricanes
Jovian Planets

8. a true-color picture of Jupiter
light and
dark bands
in latitude
(along the
direction
of rotation)
are
smog-like
clouds
ovals are
giant storms
like
hurricanes
stretched
out by
rapid
rotation
Jovian Planets

9. (more on Jupiter’s atmosphere)
The Great Red Spot
First seen in 1630, little changed since
40,000 km long, 14,000 km wide
Red due to hydrocarbons and phosphorus
Jovian Planets

10. The Great Red Spot (a long-lived storm)
Jovian Planets

11. Figure 8.10a
enhanced color
image from
your textbook

12. (more on Jupiter’s atmosphere)
Composition of atmosphere
Voyager, and esp. Galileo probe
Element % mass
Hydrogen 86
Helium 14
Others (ammonia, methane)
Very much like Sun’s composition
Jovian Planets

13. Interior Structure of Jupiter
Three clues:
Average density: 1.3 gm/cm3
Composition like Sun
Observations of infrared light: Jupiter radiates almost twice the energy it receives from Sun, so Jupiter must have internal heat source
Jovian Planets

14. Interior Structure (cont.)
Internal layers (best guess model)
Atmosphere (1000 km thick)
includes the clouds, what we see
Liquid hydrogen + helium (20,000 km)
Metallic hydrogen (35,000 km)
Iron and rock core (10-20 times Earth’s mass)
Jovian Planets

15. A model of Jupiter’s interior 1 bar is the pressure
Figure 8.3
(density of liquid water)
1 bar is the pressure
of the air we breathe
A model of
Jupiter’s interior

16. A model of Jupiter’s interior
Jovian Planets

17. Jupiter’s magnetic field and radiation belts
Space probes found strong field,
10 times Earth’s
Generated by metallic liquid hydrogen layer and rapid rotation (a “dynamo”)
Makes big, intense radiation belts
Electrons and protons from Sun trapped on magnetic field
Hazard to spacecraft like Galileo
Jovian Planets

18. Jupiter’s radiation belt and magnetic field
Jovian Planets

19. Jupiter’s satellites and ring
At least 63 moons, 1 ring known
4 largest seen by Galileo (in 1610)
Voyager, Galileo probes found great variety
Jovian Planets

20. Jupiter’s Galilean satellites
Satellite Period Density Mass
(days) (gm/cm3) (Moon=1) Io
Europa
Ganymede
Callisto
Composition varies a lot (note range of densities)
Jovian Planets

21. The Galilean Satellites and the Great Red Spot
Jovian Planets

22. The Galilean Satellites (in order from Jupiter)Io
Mostly rock (note density)
Active volcanoes! (molten sulfur)
Heated by tidal forces from Jupiter
Elliptical orbit, gets squeezed each time
Surface: very young, constantly renewed by volcanic outflows
(seen by Galileo spacecraft)
Jovian Planets

23. Slides of Io Full-view images Closeup of active volcano Lava flow
Enhanced and true color
Lava flow
Active eruption; note glowing lava
Left, Io in eclipse with glowing gases over active volcanoes
Jovian Planets

24. Images of Io from Galileo spacecraft
Jovian Planets

25. Active eruption; note glowing lava
Jovian Planets

26. Galilean satellites (cont.)
Europa
Mostly rock (note density)
Thin, icy crust, with long complex cracks
Surface: rel. young, few impact craters
Eroded since 3 billion years ago
Galileo spacecraft found evidence of liquid water ocean under icy crust!
Possible life in the water???
(NASA wants to go ice fishing)
Jovian Planets

27. Slides of Europa Enhanced color view Closeup of crossing cracks
Note many long cracks
Closeup of crossing cracks
Super closeup, looks like ice flows
Who lost a mitten?
What made this structure?
Chaotic icy blocks
Two models of Europa’s inside
Warm icy slush (a giant Eegee’s ! )
Real liquid water under ice
Jovian Planets

28. Enhanced color view of Europa Note many long cracks
Jovian Planets

29. Closeup of crossing cracks
Jovian Planets

30. Super closeup, looks like ice flows
Jovian Planets

31. Who lost a mitten? (What made this structure?)
Jovian Planets

32. Chaotic icy blocks
Jovian Planets

33. Two models of Europa’s inside (1) Warm icy slush (a giant Eegee’s
Two models of Europa’s inside (1) Warm icy slush (a giant Eegee’s ! ) (2) Real liquid water under ice
Jovian Planets

34. Continuing our tour of Jupiter’s Galilean satellites… Io Europa
Ganymede
Callisto
Jovian Planets

35. Galilean satellites (cont.)
Ganymede
Largest moon in solar system
Density implies
Rocky core, size of our Moon
Thick mantle of water ice
(brittle, because very cold: C)
1/3 of surface heavily cratered
Old, over 4 billion years
Rest smooth or grooved terrain
(but ice, not rock)
Jovian Planets

36. Ganymede: a strange mix of dark, light areas
Jovian Planets

37. Grooves in surface of Ganymede—”tectonic” activity in ice!
Jovian Planets

38. Galilean satellites (cont.)
Callisto
Icy, like Ganymede
Heavily cratered over whole surface
(shallow craters in ice, not rock)
Unchanged since end of heavy impact cratering 4 billion years ago
Oldest surface in Solar System
Atmospheres
No atmospheres in outer 3 Galilean moons
Io has thin atmosphere of volcanic gases, with sulfur compounds
Jovian Planets

39. Callisto, cratered all over-- so entire surface is old, never melted
Jovian Planets

40. Slides of Ganymede, Callisto, and the Ring
Strange mix of dark, light areas
Callisto, cratered all over
Entire surface is old, never melted
Portraits of the Galilean satellites
In order of size: Ganymede, Callisto, Io, Europa
Ring, backlit by Sun
Jovian Planets

41. Portraits of the Galilean satellites In order of size: Ganymede Callisto Io Europa
Jovian Planets