Download The Fathers of the Gods: Jupiter and Saturn

The Fathers of the Gods:
Jupiter and Saturn
Learning Objectives
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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 Jupiter’s Galilean moons and Saturn’s moon
Titan. Each has one characteristic that makes it special
What are Saturn’s rings made of? Is Saturn the only
planet with rings?
The Outer Planets
Inner Planets:
“Terrestrial” or “rocky”
Outer Planets:
“Jovian” or “Gas Giants”
Jupiter Facts!
Jupiter has over 65
moons, the 4 most
massive (“the Galilean
Moons”) were discovered
by Galileo
Radius
Surface gravity
Mass
Distance from Sun
Eccentricity
Tilt
Year
Solar day
11.2 Earth
2.5 Earth
318 Earth
5.2 AU
0.048
3.1°
11.9 Earth years
9 hrs 56 mins
Jupiter, King of the Planets
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An atmosphere unlike Earth’s
 90%
Hydrogen, 10% Helium, ~0.3%
other stuff
 Very
 Rich
similar to the Sun’s composition
chemistry
 0.3%
contains methane, ammonia, other
hydrocarbons, water, etc..
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500-600 mph winds are commonplace
 Incredible pressures
 Increasing temperatures with depth
Driving Jupiter’s Weather
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On Earth, solar heating drives weather
On Jupiter, internal heat drives weather
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Jupiter radiates ~70% more heat than it receives
from the Sun
 This heat is from Jupiter
contracting under
its own gravity
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Convection then
leads to cloud bands
Jupiter’s strong
rotation produces
compact bands parallel to Jupiter’s equator
The Great Red Spot
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A huge storm 25,000 km across
Three Earths would fit inside
Probably first observed over 300 years ago
Cassini images
Voyager 1 image
Jupiter’s Interior
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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
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Liquid metal
hydrogen
generates a
magnetic field
 14x stronger than
the Earth’s field
 Over 4 million
km across
J. Spencer
A ring of ionized
(electrically charged) particles surrounds Jupiter
 Stripped from Jupiter’s moon Io by Jupiter’s
very powerful magnetic field
Saturn Facts!
Saturn has over 60
moons
Equatorial radius
Mass
Eccentricity
Year
9.45 Earth
95.2 Earth
0.056
29.5 Earth years
Surface gravity
1.06 Earth
Distance from Sun 9.55 AU
Tilt
26.7°
Sidereal day 10 hrs 33 mins
Driving Saturn’s Weather
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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 is contracts, heat is produced
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As on Jupiter, storms are produced
between cloud bands
 No
long-lasting storm like the Great Red Spot
The Great White Spot
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A seasonal storm!
 Unlike
Jupiter,
Saturn has seasons
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An ammonia bubble
that forms in summer
in Saturn’s northern
hemisphere
 Lasts a few
months
 Gets
wrapped
around the planet by
the equatorial winds
Saturn’s Interior
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Similar structure to
Jupiter’s
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Saturn is less
massive, so less selfgravity
 The interior is less
compressed
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Liquid metallic hydrogen
creates a magnetic field
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not a strong one
 Slightly weaker than
the Earth’s
Jupiter’s Moons
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Jupiter has over 65 moons
 Most are small
 Some are captured asteroids
The 4 largest are the Galilean moons
 Callisto, Ganymede, Europa, and Io
 Discovered by Galileo (early use of telescope)
Io
Europa
Ganymede
Callisto
All Stirred Up
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The Galilean moons have weak magnetic
fields
Tidal and magnetic forces from Jupiter
stirs 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
Io
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Innermost Galilean
moon
Most volcanically
active body in the
Solar System
Volcanoes spew
molten sulfur-loaded
magma
Constantly repaved
surface - no impact
craters
Pillan Patera eruption
Before & after
Europa
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Icy crust 10 to 30 km thick
Cracks and fissures on surface – upwelling?
Evidence for a deep (~100 km) liquid water ocean
beneath the crust
Galileo Spacecraft
Ganymede
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Largest moon in the Solar
System
Partly ancient surface,
partly younger surface
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Younger surfaces about the
age of the Moon’s maria
Compared to our Moon:
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50% larger
 10% larger than Mercury!
 100% more massive
 40% less dense
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Interior more differentiated than Callisto, probably
has an iron core
Callisto
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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
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Surface is made of “dirty ice”
Interior is rocky, mixed with ice
Saturn’s Famous Rings
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Two main rings
 (A and
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Several fainter rings
 (C
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B)
through G)
The rings are thin
 Only
roughly tens to
hundreds of meters
thick
 Made of ice-covered rocks and ice pellets
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Note that Jupiter also has a weak ring system
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fact, all of the Gas Giants have rings
Titan
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Saturn’s largest moon
 bigger than Mercury
 second largest in Solar System
Titan’s atmosphere
Dense nitrogen/methane
atmosphere (like smog)
 Only Solar System moon
that has 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
Next Time
The Edge of Town