1. The Giant Planets - Jupiter, Saturn, Uranus & Neptune
Chapter 8

2. Jovian Planets: Basics
Distance: 5-30 AU
Much farther from Sun than terrestrial planets
Much colder ( K)
Mass: Earth masses
Much more massive than terrestrial planets
Jupiter & Saturn are similar
Size (about 10 Earth diameters)
Composition: mostly hydrogen and helium
Uranus & Neptune are similar
Smaller than Jupiter & Saturn
Less hydrogen and helium

3. Basic Data Jupiter Saturn 318 Earth masses 11 Earth diameters
density 1.3 g/cm3
Saturn
95 Earth masses
density 0.7 g/cm3
would float!
lowest of any planet

4. Basic Data Uranus Neptune 14 Earth masses density 1.2 g/cm3
diameter 36% of Jupiter’s
Neptune
17 Earth masses
density 1.6 g/cm3
diameter 35% of Jupiter’s

5. Appearance Jovian planets show “banded” appearance
due to atmosphere
we see only cloud tops
Rotation quite fast (hours)
Jupiter: 10 hrs
Saturn: 11 hrs
Uranus: 17 hrs
Neptune: 16 hrs

6. Clouds Clouds on Jupiter & Saturn Clouds on Uranus & Neptune
composed of ammonia ice (NH3)
different colors
due to differing cloud composition
Saturn’s clouds deeper; less visible
Clouds on Uranus & Neptune
composed of methane (CH4)
produces blue-green color

7. Atmospheric Structure
Temperature and pressure increase inward
Different molecules condense at different altitudes
Form cloud layers

8. Winds and Weather Cloud Bands alternating E-W wind patterns
Light zones indicate upwelling
Dark zones indicate sinking
convection

9. Winds and Weather “Storms” Great Red Spot on Jupiter
has persisted for over 400 yrs
Great Dark Spot on Neptune
seen in 1989 by Voyager
not seen in 1994 (by HST)

11. Axial Tilt & Seasons Jupiter Saturn Neptune Uranus
only 3º axis tilt; no real seasons
Saturn
27º tilt; normal seasonal variation
Neptune
29º tilt; similar to Saturn
Uranus
98º tilt (on its side!) [collision?]
extreme seasons!
each 21 yrs long
Seasons on Uranus

12. Interior: Composition and Structure
Cores: “rock” & “ice”
extreme pressure
Jupiter and Saturn
large outer layers (H, He)
Uranus and Neptune
like Jupiter, Saturn with outer layers removed
Much less hydrogen

13. Summary of Jovian Planets
Jovian planets larger, more massive than terrestrial
Composition:
mostly hydrogen (H) and helium (He)
dominated by hydrogen
also large amounts of ices (water, ammonia, methane)
Why So Large?
basic reason is distance from sun
cooler temps allowed ices (volatiles) to freeze

14. Role of Volatiles Inner solar system is hot:
volatiles are gaseous; not available for planet core formation
planet cores
only rock (no ice)
smaller, less massive (1 earth mass)
Outer solar system is cold:
volatiles are solid; available for planet core formation
both rock and ice
bigger, more massive (10 earth masses)
Massive cores have larger gravity; can capture gas
Jovian planets have massive atmospheres (lots of H and He)
Terrestrial planets have minimal atmosphere (little H and He)