Chapter 8
Jovian Planet Systems
Key Questions….
• How do we know what we do?
• What value is there to ask these questions, and
build probes to answer them?
A Different Kind of Planet
Our goals for learning:

What are jovian planets made of?

What are jovian planets like on the inside?

What is the weather like on jovian planets?
The Jovian Planets
Jupiter!
The biggest
planet! (By
far…)
Jupiter’s
atmosphere is
dynamic!
Jupiter!
Jupiter!
Some great
moons create
eclipses
every day!
A model of Jupiter
Jupiter’s
Colors


Ammonium sulfide clouds reflect red/brown.
Ammonia reflects white (highest, coldest clouds)
Jupiter’s Atmosphere

Hydrogen compounds
in Jupiter form clouds.

Different cloud layers
correspond to freezing
points of different
hydrogen compounds.

Other jovian planets
have similar cloud
layers.
Jupiter’s
Great
Red
Spot
A storm twice as wide as Earth
 Has existed for at least 3 centuries

Seen for
years!
1880 view
from
French
Astronomer
Etienne
Trouvelot
Recent images: The spot is shrinking!
1980
Recent images: The spot is shrinking!
What kinds of moons orbit the
jovian planets?
Common Features?
• Cratering increases farther from Jupiter
• Cracks increase closer to Jupiter
Why are Jupiter’s Galilean
moons geologically active?
Io’s Volcanoes
Volcanic eruptions continue to
change Io’s surface
Io’s Volcanic Activity

Io is the most volcanically active body in
the solar system, but why?
Io’s Volcanic Activity
Thought Question
How does Io get heated by Jupiter?
A.
B.
C.
D.
Auroras
Infrared light
Jupiter pulls harder on one side than the
other
Volcanoes
Thought Question
How does Io get heated by Jupiter?
A.
B.
C.
D.
Auroras
Infrared light
Jupiter pulls harder on one side than the
other
Volcanoes
Tidal Heating
Io is squished and
stretched as it orbits
Jupiter.
But why is its
orbit so
elliptical?
Orbital
Resonances
Every 7 days,
these three
moons line up.
The tugs add up over
time, making all three
orbits elliptical.
Europa’s Ocean: Waterworld?
Europa’s Ocean: Waterworld?
Tidal Stresses Crack Europa’s
Surface Ice
Tidal stresses crack Europa’s
surface ice
Tidal flexing
closes crack,
grinds up ice
Tidal flexing
opens crack,
leaving two
ridges
Europa’s Interior Also Warmed by Tidal
Heating
Europa’s Surface
A lava-lamp model for Europa?
Ganymede
Ganymede
Largest moon in
the solar system
 Clear evidence of
geological activity
 Tidal heating plus
heat from radioactive decay?

Ganymede’s
Two Faces
Callisto
Callisto
“Classic”
cratered iceball
 Little/No tidal
heating, no
orbital
resonances
 But it has
magnetic field !?

Saturn’s
Colors

Saturn’s layers are similar but are deeper in
and farther from the Sun — more subdued.
Belts & Zones on Saturn, too!
Storms on Saturn, too!
Storms on Saturn, too!
Storms on Saturn, too!
Storms on Saturn, too!
New Results from Cassini
Gossamer
thin rings…
Saturn’s rings vary in
composition, and change
temperature of the planet
Saturn’s
Largest
Moon:
Titan
Titan’s Atmosphere

Titan is the only
moon in the solar
system which has
a thick
atmosphere.

It consists mostly
of nitrogen with
some argon,
methane, and
ethane.
Titan’s Surface


Huygens probe provided a first look at Titan’s surface in
early 2005
Liquid methane, “rocks” made of ice.
A view of Titan
Titan’s “Lakes”

Radar imaging of Titan’s surface has
revealed dark, smooth regions that may be
lakes of liquid methane.
Ongoing Activity on Enceladus
Ongoing Activity on Enceladus

Fountains of ice
particles and
water vapor from
the surface of
Enceladus
indicate that
geological activity
is ongoing.
Ongoing Activity on Enceladus
Ongoing Activity on Enceladus
Revisiting the Jovian Planets
Jovian Planet Composition

Jupiter and Saturn
—
—

Mostly H and He gas
Rock/Metal core
Uranus and Neptune
—
—
—
Mostly hydrogen compounds: water (H2O),
methane (CH4), ammonia (NH3)
Some H, He
Rock/Metal core
Jovian Planet Formation
Recall the CONDENSATION SEQUENCE theory:

Where the planets formed dictated what solid
materials they could form from.

Beyond the frost line, planetesimals could
accumulate Hydrogen-rich ICE.

Hydrogen compounds are more abundant than
rock/metal => jovian planets got bigger &
acquired H/He atmospheres.
Jovian Planet Formation

Jovian planet cores should be very similar:
~ mass of 10 Earths
 Rock, iron, heavier materials differentiated


Differences are in amount of H/He gas
accumulated.
Why did that amount differ?
Differences in Jovian Planet
Formation

TIMING: “The Early Bird gets the worm.”

LOCATION (“Location, Location, Location!”)
Differences in Jovian Planet
Formation

TIMING: Planets forming earliest capture
most hydrogen & helium gas.


Capture ceases after first solar winds blew
leftover gas away.
LOCATION: Planets that forms in denser
part of nebula forms their cores first.
What are jovian planets like on
the inside?
What are Uranus & Neptune
like on the inside?

Older
hypothesis
had more
gaseous
hydrogen
over water
Comparing Jovian Interiors


Models suggest cores have similar composition.
Lower pressures inside Uranus and Neptune
mean no metallic hydrogen.
What are Uranus & Neptune like
on the inside?

Newer hypothesis has less gas
Methane on Uranus & Neptune

Methane gas on
Neptune & Uranus
absorbs red light
but transmits blue.

Blue light reflects
off methane
clouds, making
those planets look
blue.
Sizes of Jovian Planets

Adding mass to
a jovian planet
compresses the
underlying gas
layers.
Sizes of Jovian Planets

Greater
compression is
why Jupiter is not
much larger than
Saturn even
though it is three
times more
massive.

Jovian planets with
even more mass
can be smaller
than Jupiter.
Inside Jupiter & Saturn

High pressure
inside of
Jupiter/Saturn
causes hydrogen
to change its
properties with
depth.

Gas => Liquid =>
Conducting Liquid
Inside Jupiter & Saturn

Hydrogen acts like
metal at great
depths because its
electrons move
freely.

Fast rotation =>
HUGE magnetic
Field!
Inside Jupiter & Saturn
Jupiter’s Magnetosphere
Jupiter’s
strong
magnetic
field
creates
enormous
magnetosphere.
Visible Proof!
Aurora on Jupiter
Magnetic Fields channel solar wind to rotation poles
Produce Aurorae
Visible Proof!
Aurora on Jupiter
Magnetic Fields channel solar wind to rotation poles
Produce Aurorae
Magnetic Fields!
Weather on Jovian Planets
All Jovian planets have strong winds & storms.
What are Saturn’s rings like?
Jovian Planet Rings
Our goals for learning:

What are Saturn’s rings like?

Why do the Jovian planets have rings?
What are Saturn’s rings like?

They are made up of numerous, tiny
individual particles.

They orbit over Saturn’s equator.

They are very thin.
How do we know this??
Earth-Based View
Earth-Based View
Spacecraft View of Ring Gaps
Artist’s Conception of Close-Up
Gap Moons

Some small
moons create
gaps within rings.
Why do the jovian planets have
rings?
Jovian Ring Systems


All four jovian planets have ring systems.
Others have smaller, darker ring particles than does
Saturn.
Why do the jovian planets have
rings?

They formed from dust created in impacts
on moons orbiting those planets.
How do we know this?
How do we know?

Rings aren’t leftover from planet formation
because the particles are too small to
have survived this long.

There must be a continuous replacement
of tiny particles.

The most likely source is impacts with the
jovian moons.
Ring Formation

Jovian planets all have rings because they
possess many small moons close-in.
Ring Formation

Impacts on these moons are random.

Saturn’s incredible rings may be an
“accident” of our time.
What kinds of moons orbit the
jovian planets?
A Wealth of Worlds: Satellites of Ice
and Rock
Our goals for learning:

What kinds of moons orbit the jovian planets?

Why are Jupiter’s Galilean moons geologically active?

What geological activity do we see on Titan & other
moons?

Why are jovian planet moons more geologically active
than small rocky planets?
Sizes of Moons

Small moons (< 300 km)
—

Medium-sized moons (300–1,500 km)
—

No geological activity
Geological activity in past
Large moons (> 1,500 km)
—
Ongoing geological activity
Medium and
Large Moons




Spherical from
gravity
Substantial amounts
of ice
Formed in orbit
around jovian
planets
Circular orbits in
same direction as
planet rotation
Small Moons

Far more
numerous than
the medium
and large
moons

Not enough
gravity to be
spherical:
“potato-shaped”
Medium Moons of Saturn
Medium Moons of Saturn
Almost all show evidence of past volcanism
and/or tectonics.
Medium Moons of Uranus

Varying amounts
of geological
activity.

Moon Miranda has
large tectonic
features and few
craters

Hypotheses?
Neptune’s Moon Triton

Similar to Pluto?
(but larger!)

Evidence for past
geological activity
Why are jovian planet moons
more geologically active than
small rocky planets?
Rocky Planets vs. Icy Moons

Rock melts at
higher
temperatures.

Ice melts at lower
temperatures.
Rocky Planets vs. Icy Moons

Only large rocky
planets have
enough heat for
activity.

Tidal heating can
melt internal ice,
driving activity.
Why study these at all?
http://solarsystem.nasa.gov/docs/Vision_and_Voy
ages-FINAL.pdf
WHAT DID YOU THINK?
Is Jupiter a “failed star”? Why or why not?
 No. Jupiter has 75 times too little mass to
shine as a star.

WHAT DID YOU THINK?
What is Jupiter’s Great Red Spot?
 The Great Red Spot is a long-lived, oval
cloud circulation, similar to a hurricane on
Earth.

WHAT DID YOU THINK?
Does Jupiter have continents and oceans?
 No. Jupiter is surrounded by a thick
atmosphere primarily of hydrogen and
helium that gradually becomes liquid as
you move inward. The only solid matter in
Jupiter is its core.

WHAT DID YOU THINK?
Is Saturn the only planet with rings?
 No. All four outer planets (Jupiter, Saturn,
Uranus, and Neptune) have rings.

WHAT DID YOU THINK?
Are the rings of Saturn solid ribbons?
 No. Saturn’s rings are all composed of
thin, closely spaced ringlets consisting of
particles of ice and ice-coated rocks. If
they were solid ribbons, Saturn’s
gravitational tidal force would tear them
apart.

Essay Questions for the Final
Question 6:
Describe Jupiter's atmosphere and its
four largest moons.
Why are they similar, and why are they
different?
Essay Questions for the Final
Question 7:
What are the similarities and differences
between Jupiter and Saturn?
Describe Saturn's Rings. How did they
probably arise? How do we know?
Essay Questions for the Final
Question 8:
What are the properties shared by Uranus
and Neptune? How are they unique?
What is Pluto like? How about the other
small bodies in the outer solar system?