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Chapter 11
Jovian Planet Systems
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11.1 A Different Kind of Planet
Our goals for learning Are jovian planets all alike?
h t re o i n l nets like on the inside?
What is the weather like on jovian planets?
Do jovian planets have magnetospheres like
Earths?
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Are jovian planets all alike?
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Jovian Planet Composition
Jupiter and Saturn
Mostly H and He gas
Mostly hydrogen compounds: water (H2O),methane (CH4), ammonia (NH3)
Some H, He, and rock
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Density Differences
1.5
2
(g/cc)
Uranus and Neptune
0
0.5
JupiterSa
turnUr
anus
Neptune
Densit
because they have less
H/He, proportionately
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Density Differences
1.5
2
(g/cc) But that explanation
doesnt work for
0
0.5
JupiterSa
turnUr
anus
Neptune
Densit
.
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Sizes of Jovian Planets
Adding mass to a
jovian planetcompresses theunderlying gas
layers
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Sizes of Jovian Planets Greater compression
is why Jupiter is notmuch larger thanSaturn even though it
massive
Jovian planets with
even more mass canbe smaller thanJupiter
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Rotation and Shape
Jovian planets are
not quite sphericalbecause of theirrapid rotation
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What are jovian planets like onthe inside?
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Interiors of Jovian Planets
No solid surface. Layers under high pressure and
.
Cores (~10 Earth masses) made of hydrogen
compounds, metals & rock
The layers are different for the differentplanets. WHY?
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Inside Jupiter
High pressures
inside Jupiter causephase of hydrogen
to change with depth
Hydrogen acts like a
metal at great depths
because its electronsmove freely
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Inside Jupiter
Core is thought to
be made of rock,metals, and
hydrogen
compounds
Core is about same
size as Earth but 10times as massive
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Comparing Jovian Interiors
Models suggest cores of jovian planets have similar
composition Lower pressures inside Uranus and Neptune mean no
metallic hydrogen
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Jupiters Internal Heat
Jupiter radiates
twice as muchenergy it receives
from Sun
Energy probably
comes from slow
contraction ofinterior (releasing
potential energy)
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Internal Heat of Other Planets
Saturn also radiates twice as much energy itreceives from Sun
(helium rain)
Neptune emits nearly twice as much energy
as it recieves, but the source of that energyremains mysterious
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What is the weather like onjovian planets?
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Jupiters Atmosphere
Hydrogen
compounds inJupiter form clouds
Different cloudlayers correspond to
freezing points of
different hydrogencompounds
H2O
NH4SH
NH3
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Jovian Planet Atmospheres
Other jovian planets
have cloud layerssimilar to Jupiters
Differentcompounds make
clouds of different
colors
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Jupiterscolors
Ammonium sulfide clouds (NH4SH) reflect red/brown.
Ammonia, the highest, coldest layer, reflects white.
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Saturns
colors
Saturns layers are similar, but deeper in and
farther from the Sun --- more subdued.
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Methane on Uranus and Neptune Methane gas of
Neptune and Uranusabsorb red light but
transmit blue light
Blue light reflects
off methane clouds,
making those planeslook blue
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Jupiters BandsWhite ammonia
clouds form
where air rises Coriolis effectchanges N-S
flow to E-W
windsBetween white
deeper reddishclouds of
NH4SH
Warmer red bands
are brighter in IR
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Jupiters
Great
Red
A storm twice as wide as Earth
Has existed for at least 3 centuries
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Weather on Jovian Planets
All the jovian planets have strong winds and
storms
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Do jovian planets havemagnetospheres like Earths?
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Jupiters Magnetosphere
Jupiters strong magnetic field gives it an enormousmagnetosphere
Gases escaping Io feed the donut-shaped Io torus
Aurora on Jupiter
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Thought QuestionJupiter does nothave a large metal core like
the Earth. How can it have a magnetic field?
a) The magnetic field is left over from when Jupiter
accreteb) Its magnetic field comes from the Sun
c) It has metallic hydrogen inside, which circulates
and makes a magnetic fieldd) Thats why its magnetic field is weak
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Thought QuestionJupiter does nothave a large metal core like
the Earth. How can it have a magnetic field?
a) The magnetic field is left over from when Jupiter
accreteb) Its magnetic field comes from the Sun
c) It has metallic hydrogen inside, which circulates
and makes a magnetic fieldd) Thats why its magnetic field is weak
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What have we learned?
Are jovian planets all alike?
Jupiter and Saturn are mostly H and He gas
Uranus and Nepture are mostly H compounds
What are jovian planets like on the inside?
ayere nter ors w t very g pressure ancores made of rock, metals, and hydrogencompounds
Very high pressure in Jupiter and Saturn can
produce metallic hydrogen
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What have we learned?
What is the weather like on jovian planets?
Multiple cloud layers determine colors of
jovian planets All have strong storms and winds
like Earths? All have substantial magnetospheres
Jupiters is largest by far
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11.2 A Wealth of Worlds: Satellites ofIce and Rock
Our goals for learning What kinds of moons orbit jovian planets?
h re iters lile n moons so
geologically active? What is special about Titan and other major
moons of the solar system?
Why are small icy moons more geologicallyactive than small rocky planets?
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What kinds of moons orbit thejovian planets?
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Sizes of Moons
Small moons (< 300 km) No geological activity
- - ,
Geological activity in past
Large moons (> 1,500 km)
Ongoing geological activity
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Medium &
Large Moons
Enough self-gravity tobe spherical
Have substantial
amounts of ice. Formed in orbit
around jovian planets.
Circular orbits in samedirection as planet
rotation.
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SmallMoons
Far more numerous than the medium and large
moons. Not enough gravity to be spherical: potato-
shaped
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SmallMoons
Captured asteroids or comets, so orbits do
not follow usual patterns.
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Why are Jupiters Galileanmoons so geologically active?
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Ios Volcanoes
Volcanic eruptions continue to change Ios surface
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Tidal Heating
Io is squished and
stretched as it orbits
Jupiter But why is itsorbit so
elliptical?
O bit l
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Orbital
Resonances
The tugs add up over
time, making all 3orbits elliptical.
Every 7 days,
these 3 moonsline up.
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Europas Ocean: Waterworld?
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Tidal stresses crack Europassurface ice.
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Europas interior also warmed by tidal heating
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Ganymede
Largest moon in the
solar system
Clear evidence of
geo og ca act v ty
Tidal heating plus
heat from radio-
active decay?
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Callisto Classic cratered
iceball. No tidal heating,
resonances. But it has
magnetic field !?
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Thought QuestionHow does Io get heated by Jupiter?
a) Auroras
b) Infrared Light
c) Jupiter pulls harder on one side than the otherd) Volcanoes
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Thought QuestionHow does Io get heated by Jupiter?
a) Auroras
b) Infrared Light
c) Jupiter pulls harder on one side than the otherd) Volcanoes
What is special about Titan and
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What is special about Titan and
other major moons of the outersolar system?
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Titans Atmosphere Titan is the only
moon in the solarsystem to have a
thick atmosphere
It consists mostly of
nitrogen with some
argon, methane, andethane
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Titans Surface
Huygens probe provided first look at Titans surface inearly 2005
Liquid methane, rocks made of ice
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Medium Moons of Saturn
Almost all show evidence of past volcanismand/or tectonics
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Medium Moons of Uranus Varying amounts of
geological activity
Moon Miranda has
large tectonicfeatures and few
craters (episode of
tidal heating inpast?)
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Neptunes Moon Triton Similar to Pluto, but
larger
E idence for ast
geological activity
Why are small icy moons more
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Why are small icy moons more
geologically active than smallrocky planets?
Rocky Planets vs Icy Moons
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Rocky Planets vs. Icy Moons
Rock melts at higher
temperatures
Only large rocky
planets have enough
heat for activity
Ice melts at lower
temperatures
Tidal heating can
melt internal ice,
driving activity
What have we learned?
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What have we learned?
What kinds of moons orbit jovian planets?
Moons of many sizes
Level of geological activity depends on size
Why are Jupiters Galilean moons so
Tidal heating drives activity, leading to Iosvolcanoes and ice geology on other moons
What have we learned?
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What have we learned?
What is special about Titan and other major
moons of the solar system?
Titan is only moon with thick atmosphere Many other major moons show signs of geological
activity
Why are small icy moons more geologicallyactive than small rocky planets?
Ice melts and deforms at lower temperatures enabling
tidal heating to drive activity
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11.3 Jovian Planet Rings
Our goals for learning
What are Saturns rings like?
Ho do other o i n rin s stems com re
to Saturns? Why do the jovian planets have rings?
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What are Saturns rings like?
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What are Saturns rings like?
They are made up of numerous, tinyindividual particles
They are very thin
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Earth-based view
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Spacecraft view of ring gaps
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Artists conception of close-up
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Gap Moons Some small moons
create gaps within
rings
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Shepherd Moons
Pair of small moons can force particles into a narrow ring
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Resonance Gaps Orbital resonance
with a larger moon
can also produce a
gap
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How do other jovian ring systemscompare to Saturns?
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Why do the jovian planets haverings?
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Why do the jovian planets haverings?
They formed from dust created in impacts
on moons orbiting those planets
How do we know that?
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Ring Formation
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Ring Formation
Jovian planets all have rings because they
possess many small moons close-in
Impacts on these moons are random Saturns incredible rings may be an accident
of our time
What have we learned?
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What are Saturns rings like?
Made up of countless individual ice particles
Extremely thin with many gaps How do other jovian ring systems compare
Much fainter ring systems with smaller,darker, less numerous particles
Why do the jovian planets have rings?
Ring particles are probably debris frommoons
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Thought QuestionWhat would happen to Earths temperature if Earth
were more reflective?
a) It would go up.
b) It would go down.
c) It wouldnt change
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Thought QuestionIf Earth didnt have an atmosphere, what would
happen to its temperature?
a) It would go up a little.
b) It would go up a lot.
c) It would go down a little.
d) It would go down a lot.
e) It would not change.
Thought Question
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g Q
If Earth didnt have an atmosphere, what would
happen to its temperature?
a) It would go up a little.
b) It would go up a lot.
c) It would go down a little.
d) It would go down a lot.
e) It would not change.
Thought Question
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g Q
Why is the sky blue?
a) The sky reflects light from the oceans.
b) Oxygen atoms are blue.
c) Nitrogen atoms are blue.
d) Air molecules scatter blue light more than red light.
e) Air molecules absorb red light.
Thought Question
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g Q
Why is the sky blue?
a) The sky reflects light from the oceans.
b) Oxygen atoms are blue.
c) Nitrogen atoms are blue.
d) Air molecules scatter blue light more than red light.
e) Air molecules absorb red light.