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 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

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

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

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

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)

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

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 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)