The Fathers of the Gods: Jupiter and Saturn

! Order all the planets by size and distance from the Sun! How are clouds on Jupiter (and Saturn) different to the

Earth? What 2 factors drive weather on the Gas Giants?! Compare and contrast the Great Red and White Spots! How does Jupiter’s interior make a strong magnetic field?

Does Jupiter’s gravity and magnetism affect its moons?! Compare Jupiter and Saturn to each other and to Earth

(size, seasons, interior, atmosphere, magnetic field)! Compare the Galilean moons to Titan and Enceladus.

Each has one characteristic that makes it special! What are Saturn’s rings made of? Is Saturn the only

planet with rings?

Learning Objectives

The Outer PlanetsInner Planets:

“Terrestrial” or “rocky” Outer Planets:

“Jovian” or “Gas Giants”

Radius 11.2 Earth Surface gravity 2.5 Earth Mass 318 Earth Distance from Sun 5.2 AU Eccentricity 0.048 Tilt 3.1° Year 11.9 Earth years Solar day 9 hrs 56 mins

Jupiter Facts!

Jupiter has at least 69 moons, the 4 most

massive (“the Galilean Moons”) were discovered

by Galileo

Jupiter, King of the Planets! An atmosphere unlike Earth’s

! 90% Hydrogen, 10% Helium, ~0.3% other stuff! Similar to the Sun’s composition

! Rich chemistry! 0.3% contains methane, ammonia,

other hydrocarbons, water, etc.! 500-600 mph winds are commonplace! Incredible pressures! Increasing temperatures with depth

Driving Jupiter’s Weather! On Earth, solar heating drives weather! On Jupiter, internal heat drives weather

!Jupiter radiates ~70% more heat than it receives from the Sun

!This heat is from Jupiter contracting under its own gravity

! Convection then leads to cloud bands

! Jupiter’s strong rotation produces compact bands parallel to Jupiter’s equator

The Outer Atmosphere! Watch the motion of the clouds:

! A huge storm 16,000 km across! A little larger than the Earth! Probably first observed over 300 years ago

Voyager 1 imageCassini images

The Great Red Spot

J. Spencer

Other storms on Jupiter! Jupiter’s poles are

covered byconstant storms

!Many cyclonesare visible in this(enhanced color)image of Jupiter’ssouth pole from the Juno mission

!The largest are about 1000 km in diameter Juno image

Jupiter’s Interior! Average density only

~30% greater than water! ~25% that of the Earth’s

average density! By 20,000 km below the

surface, the pressure is 3 million times that on the Earth’s surface! Hydrogen is a liquid

metal at this pressure! Core of rock & “ice”

~10-50 Earth masses

Jupiter’s Magnetosphere! Liquid metal

hydrogen generates a magnetic field!14x stronger than

the Earth’s field!Over 4 million

km across! A ring of ionized

(electrically charged) particles surrounds Jupiter!These particles are stripped from Jupiter’s moon

Io by Jupiter’s very powerful magnetic field

Equatorial radius 9.45 Earth Surface gravity 1.06 Earth Mass 95.2 Earth Distance from Sun 9.55 AU Eccentricity 0.056 Tilt 26.7° Year 29.5 Earth years Sidereal day 10 hrs 33 mins

Saturn Facts!

Saturn has at least 62 moons

Driving Saturn’s Weather! Like Jupiter, Saturn’s atmosphere is mostly

hydrogen and helium! As on Jupiter, Saturn’s internal heat drives

weather!Saturn radiates over twice as much energy

back into space as it receives from the Sun!Like Jupiter, Saturn is still contracting!As it contracts, heat is produced

! As on Jupiter, storms are produced between cloud bands!No long-lasting storm like the Great Red Spot

The Great White Spot! A seasonal storm!

!Unlike Jupiter, Saturn has seasons

! An ammonia bubble that forms in summerin Saturn’s northern hemisphere ! Lasts a few months!Gets wrapped around

the planet by the equatorial winds

Saturn’s Interior! Similar structure to Jupiter

!But Saturn is less massive, so less self-gravity

!The interior is less compressed

! Liquid metallic hydrogen creates a magnetic field!But not a strong one!Slightly weaker than

the Earth’s field

Jupiter’s Moons

!Jupiter has over 69 moons!Most are small!Some are captured asteroids

!The 4 largest are the Galilean moons! Io, Europa, Ganymede and Callisto!Discovered by Galileo (one of the first uses of

the telescope as a tool in astronomy)

Io EuropaGanymede Callisto

All Stirred Up! The Galilean moons have weak magnetic

fields! Tidal and magnetic forces from Jupiter stir

the interior of Jupiter’s moons! Leads to warm & liquid interiors

! Liquid conducting cores + rotation = magnetic fields

! Also, this heating is what makes Io volcanic and allows water to stay in liquid form under Europa’s surface

Pillan Patera eruption Before & after

Io! The innermost

Galilean moon ! The most volcanically

active body in the Solar System

! Volcanoes spew molten sulfur-loaded magma

! Constantly repaved surface - very few impact craters

Galileo Spacecraft

Europa! Icy crust ~10 to 30 km thick! Cracks and fissures on the surface – likely some

upwelling of water in impact craters! Evidence for a deep (~100 km) liquid water

ocean beneath the crust

Ganymede! Largest moon in the Solar System! Partly ancient surface, partly younger surface

!Younger surfaces are about the age of the Moon’s maria

! Compared to our Moon:!50% larger

! That’s 10% larger than Mercury!

!100% more massive!40% less dense

! Interior more differentiated than Callisto, probably has an iron core

Callisto! Farthest of the Galilean

Moons from Jupiter! Ancient surface,

covered with craters! Compared to our Moon:

!40% larger! About Mercury’s size

!50% more massive!45% less dense

! Surface is made of “dirty ice”! Interior is rocky, mixed with ice

Saturn’s Famous Rings! Two main rings

! (A and B)! Several fainter rings

! (C through G)! The rings are thin

!Only roughly tens to hundreds of meters thick

!Made of ice-covered rocks and ice pellets! Note that Jupiter also has a weak ring system

! In fact, all of the Gas Giants have rings

Titan! Saturn’s largest moon

!Bigger than Mercury!The second largest

in the Solar System! Dense nitrogen

and methane atmosphere (like smog)!The only moon in the Solar System

to have a dense atmosphere! Liquid/ice hydrocarbons?! Organic compounds –> life?

!Probably not – too cold: 95 K!May be a “freeze” of the chemical

composition of the ancient Earth

Enceladus! Saturn’s Sixth-largest moon

! About 10x smaller in radius than Titan

! Covered in ice! Smoothness suggests

that ice in Enceladussouthern regions is recently deposited

! Geologically active! Dozens of water-rich

geysers venting frombeneath the surface!

Next Time

The Edge of Town