1. Lecture 8: Jovian (Giant) Planets
SCI238 W08
Lecture 8: Jovian (Giant)
Planets
Neptune and Triton image from Voyager 2 spacecraft (1989)
L8 – Jan 31/08
Jovian Planets

2. This week’s events: the Moon: New Moon Feb 7
Venus: visible low in east before sunrise; brightest “morning” star
Mars: is visible all night, rises at sunset
Jupiter: passing Venus. take a look at 6am 1 -3 Feb!
Saturn: rises at 8pm
L8 – Jan 31/08
Jovian Planets

3. Today’s Lecture announcements etc… Moon terrestrial planets compared
assignment 2, also posted on course webpage
Moon
terrestrial planets compared
overview of the Giant Planets
interiors
“surface” features
atmospheres
magnetic structures
moons
rings
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Jovian Planets

4. Moon’s interior differentiated, but not as “extreme” differences as Earth
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Jovian Planets

5. Craters on the Moon are due to impact events
Impact craters found throughout SS
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Jovian Planets

6. Impact process forms characteristic shape...
ejecta
circular, rimmed, low floor
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Jovian Planets

7. Maria and Highlands are different in age
How do we know?
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Jovian Planets

8. Apollo astronauts returned samples from many locations
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9. Lunar samples: radioactive dating => relation between surface density of craters and age
40,000
60,000
# Craters (>1km) 4 2
Age of Surface Deposit (Gyr)
age of oldest samples: ~4.4x109 yr (highlands)
maria samples: ~3x109yr
youngest lunar surface samples ~109yr
L8 – Jan 31/08
Jovian Planets

10. What is the pattern (correlation) here?
Terrestrial surfaces have different “ages”
What is the pattern (correlation) here?
Crustal rock solidified globally first on Moon, last on Earth
L8 – Jan 31/08
Jovian Planets

11. Comparative Planetology…
interiors – role of mass
atmospheres – role of mass, distance from sun
surfaces – liquid water, lava, tectonics, impacts, surface age
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Jovian Planets

12. All terrestrial bodies are differentiated
=> All had hot (and fluid) interiors at some time
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13. Larger terrestrial planets: cooled more slowly
more and longer lasting tectonic activity
easier to retain atmosphere
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14. For planets closer to the sun: higher T
harder to retain liquid water, atmospheres
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15. higher rotation => more “weather”
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16. fewer impact craters on massive planets: cooled more slowly
atmospheres shield only against small impactors
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17. Giant Planets size interiors atmospheres, rapid rotation, circulation
magnetic fields
satellites
rings
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Jovian Planets

18. Physical Properties of the Jovian Planets (mostly Earth units)
radius
mass
Density (kg/m3)
Prot (d)
axis
tilt
Mag. field?
gsurf
Earth
6,378km
5.97×1024 kg
5,520
0.9973
23.45 Y
9.8m/s2
Jupiter
11.2
317.9
0.24
0.41
3.08
2.36
Saturn
9.5
95.2
0.12
0.44
26.73
0.92
Uranus
4.0
14.5
0.23
-0.72
97.92
0.91
Neptune
3.8
17.1
0.30
0.67
29.6 y
1.14

19. Jovian planets: size comparison
Jupiter by far the largest
all >> Earth
Uranus, Neptune similar
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Jovian Planets

20. the giant planets are rapidly rotating, large “gravitationally bound” balls of fluid.
although gravity tends to pull fluid together into a sphere, rotation flattens this into an “ellipsoid”.
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21. Saturn is the most oblate giant planet
Rpolar = 0.9 Requatorial
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22. Jupiter’s interior is differentiated
mostly metallic H!
core: rocky+metallic +H compounds
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Jovian Planets

23. Jovian planets: all have differentiated interiors
Cores all ~10-15MEarth
J,S: higher % H, H compounds
U,N: higher % rocky, H mostly in methane, ammonia
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Jovian Planets

24. The Structure of Jupiter’s Atmosphere
as with terrestrial atmospheres: clouds, T, altitude
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25. atmospheres ~same structure…
differences: Tmax, pressure, some composition
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26. Bands in Jupiter’s atmosphere:
result of heat, convection, rotation (Coriolis)
visible light image
IR image
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27. the colour differences between various components of Jupiter’s atmosphere combined with the circulation pattern produce distinctive banding structure.
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Jovian Planets

28. Jupiter’s Great Red Spot is a high pressure storm region
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Jovian Planets

29. …and the white spot is a low pressure storm region
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30. …and now Jupiter has a second large red storm
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31. Saturn too has bands and storms, but less prominent
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32. Neptune and Uranus’ blue colour:
methane absorbs red λ and reflects blue
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33. all 4 jovian planets have strong magnetic fields and huge magnetospheres
Uranus’ and Neptune’s magnetic fields strongly tilted re rotation axis
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Jovian Planets

34. we also see auroral zones near the magnetic poles
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35. 3/4 Jovian planets have internal heat sources
TBB(obs)
“total” Power
Internal Power
Jupiter
127K
2x input
4x1017 W
Saturn 97
2.8x
2x1017
Uranus 58
~1x
1015
Neptune 56
2.5x
3x1015
Primordial heat? Helium rain?
Other?
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Jovian Planets

36. Jupiter: strongest, most colourful bands, storms…
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Jovian Planets

37. Jupiter very layered atmosphere strong magnetic field no true surface
hydrogen/helium, methane, ammonia, water
strong “banding” – seeing different cloud layers
white at depth “0 km” is ammonia
red at depth 25 km is ammonia hydrosulphide
blue at depth 100 km is water ice
Giant Red Spot – a giant storm seen since first telescope viewed Jupiter, fading a bit perhaps, but still 40,000 km wide; and now another!
strong magnetic field
no true surface
very oblate planet (fast rotation)
hotter than expected – but not Greenhouse effect
planet is contracting!
mostly H/He interior with metallic H and rocky core
L8 – Jan 31/08
Jovian Planets

38. Saturn: prominent ring system, more subtle bands
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Jovian Planets

39. Saturn similar to Jupiter but smaller layered banded atmosphere
hydrogen/helium, methane, ammonia
strong magnetic field
metallic hydrogen and rocky core
rings are most massive and prominent of all
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40. Cassini-Huygens mission to Saturn
a joint NASA-ESA mission to explore Saturn and its moons
web site at saturn.jpl.nasa.gov
reached Saturn 30 June, 2004 (after seven year flight)
now in 4 year mission, orbiting through the Saturn system
recent results: in the midst of series of flybys of Titan (last on 15 Jan. 2006)
Huygens
probe toTitan Jan 24/2005
landed in mud
has found water ice, methane springs, rivers with islands
Epimetheus (30 Mar. 2005)
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Jovian Planets

41. Uranus: almost completely featureless in visible light
but shows more detail in IR
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42. Uranus accidentally discovered telescopically in 1781
faint features, blue atmosphere
hydrogen, helium, methane, BUT NO AMMONIA
strong magnetic field
hydrogen NOT metallic, rocky core
rotation axis tilted 98o → very strong seasonal effect
L8 – Jan 31/08
Jovian Planets

43. Neptune shows large storm features, like Jupiter
the storms change over timescales of years or less
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Jovian Planets

44. Neptune position predicted from observations of Uranus
discovered in 1846
very similar to Uranus, but more methane
more cloud features
warmer(!) than Uranus
L8 – Jan 31/08
Jovian Planets

45. Jovian satellites: some large, many small some have been
geologically active:
now or in the past
some formed
with planet,
some captured
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Jovian Planets

46. Jupiter’s Large SatellitesIo
geologically active (with active volcanoes!)
covered in orange sulphur compounds
strongly tied to Jupiter’s magnetic field
Europa
smooth surface with few craters
water ice, possibly over liquid water
Ganymede
largest moon in the Solar System
water ice over much of surface
Callisto
heavily cratered
concentric circular ridges are signs of a large impact
L8 – Jan 31/08
Jovian Planets

47. the four “Galilean” satellites of Jupiter
Io Europa Ganymede Callisto
surface “age” ↑ and mean density ↓ with distance from Jupiter
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48. Io: most volcanically active body in SS
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49. Io: volcanoes are frequent …constantly changing surface appearance
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50. Io: tidal interaction and eccentric orbit heat its interior
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51. Io, Europa, Ganymede: and orbital resonance
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52. Charged particles escaping Io interact with Jupiter’s magnetosphere => Io torus
Periodic variability in
radio emission from
torus first observed
in 1960s
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Jovian Planets

53. Europa’s smooth surface and cracked terrain
the result of tidal heating and icy composition
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54. just below Europa’s surface: liquid water or warm convecting ice?
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55. Ganymede’s surface shows both old and young regions
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56. Callisto’s surface is the “oldest” of the four Galilean satellites
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57. L8 – Jan 31/08
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58. Saturn’s Moons
many moons, but probably a large number still to be discovered
Titan: largest of Saturn’s moon’s – has a thick atmosphere, extending far out into space, probably has frozen water (ice)
innermost moons tidally locked to planet
moons interact with rings
L8 – Jan 31/08
Jovian Planets

59. Titan: Saturn’s largest moon; has a thick atmosphere
methane,
nitrogen…
smoggy
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60. Huygens probe shows some surface features on Titan
Titan: icy “rocks”, “river” valleys…
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61. Saturn’s Moons are varied, enigmatic
deathstar Mimas
icy Enceladus
cratered Tethys
old Dione
streaky Rhea
two-faced Iapetus
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Jovian Planets

62. Uranus’ moons
more than 20 small ones, some irregular in shape, some retrograde
five midsized: Miranda, Ariel, Umbriel, Titania, Oberon
All icy, varied geological history
Miranda is strange – very fractured surface, some cataclysmic event?
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Jovian Planets

63. near IR image shows Neptune’s rings and seven of its moons
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Jovian Planets

64. Urabus’ Miranda shows a fractured surface, obvious violence, but from what?
messed-up
Miranda
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Jovian Planets

65. Neptune’s moons five small inner moons near ring system
two larger, icy…
five small outer, retrograde
Triton
very much larger than any other Neptune moon
has thin nitrogen atmosphere
surface has nitrogen geysers
retrograde (backwards) orbit
spiraling in towards Neptune
L8 – Jan 31/08
Jovian Planets

66. Triton: moon of Neptune
Nitrogen
atmosphere
surface has been
reshaped by
geological activity
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Jovian Planets

67. Saturn’s Rings: the brightest, best known
within “Roche Limit” of Saturn where any large rocks (moons) break up due to tidal effects
major rings (“A”, “B”, and “C”) with gaps between them “Cassini’s Division”
composed of icy particles with sizes between 1 micron and 10 meters
Voyager discoveries:
several other rings
fine rings within each ring, like record grooves: “spiral density waves”
short-lived spokes
braided rings
“shepherd” satellites
rings are very thin – at most a few tens of meters
L8 – Jan 31/08
Jovian Planets

68. Saturn’s rings are wide, thin, and complex
Radio image
colours ->
particle size
purple: mainly >5cm
green: mainly <1cm
white: particle
density too high
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Jovian Planets

69. Shepherd moons control the width of rings…
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70. …and also make gaps
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71. “spokes” in Saturn’s rings: charged particles briefly suspended above the plane?
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72. Galileo spacecraft shows rings around Jupiter
ring particles are small and dark: debris from Metis..
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Jovian Planets

73. Near IR image shows rings around Uranus and some of its moons
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Jovian Planets

74. Neptune’s rings are narrow and bright with dusty regions
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Jovian Planets