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

The Giant Planets -Jupiter, Saturn, Uranus & Neptune

Chapter 8

Jovian Planets: Basics

• Distance: 5-30 AU– Much farther from Sun than terrestrial planets– Much colder (100-50 K)

• Mass: 10-100 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

Basic Data

• Jupiter– 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

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Basic Data

• Uranus– 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



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

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Clouds

• Clouds on Jupiter & Saturn – 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

Atmospheric Structure• Temperature and pressure increase inward

– Different molecules condense at different altitudes• Form cloud layers

Winds and Weather• Cloud Bands

– alternating E-W wind patterns– Light zones indicate upwelling– Dark zones indicate sinking

convection

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)



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Axial Tilt & Seasons

• Jupiter– 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

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

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

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

– planet cores• 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)

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

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