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28.3
THE OUTER PLANETS
THE OUTER PLANETS
Main Idea: Jupiter, Saturn,
Uranus, and Neptune have large
masses, low densities, and many
moons and rings
You should be able to:
Compare and contrast the
gas giant planets
Identify the major moons
Explain the formation of
moons and rings
Compare the composition
of the gas giants to the sun
THE GAS GIANT
PLANETS
Jupiter, Saturn, Uranus, and Neptune are all known as the
gas giants
They are very large! From about 15 to more than 300 times
the mass of Earth
Their interiors are either gases or liquids, and they may have
small, solid cores
GAS GIANTS
They are
primarily made
up lightweight
elements such
as hydrogen,
helium, carbon,
nitrogen and
oxygen
They gas giants
all have many
satellites as well
as ring systems
JUPITER
Jupiter is the largest planet
Its diameter is 1/10th of the sun and 11
times larger than Earth
Jupiter makes up 70% of all planetary
matter in the solar system
JUPITER
Jupiter seems bright because
its albedo is 0.52
Jupiter has a banded
appearance, as a result of flow
patterns in its atmosphere
Jupiter has a Great Red Spot
This spot is an atmospheric
storm that has raged for more
than 300 years!
JUPITER’S RINGS
Galileo spacecraft observed Jupiter and its moon during a 5
year mission in the 1990s.
It showed two faint rings around the planet in addition to a
6400km wide ring around the Jupiter
ATMOSPHERE AND
INTERIOR
Jupiter is lighter than it may
appear in size because it is
composed mostly of hydrogen
and helium in a gaseous or
liquid form
Below the liquid hydrogen is a
layer of liquid metallic hydrogen
Jupiter has a magnetic field due
to this metallic hydrogen
Earth-sized core
JUPITER’S ROTATION
Rotates very quickly for its
size
It spins once every 10
hours, giving it the shortest
day in our solar system
Because Jupiter rotates so
quickly, the clouds slow
rapidly as well, in bands of
alternating dark and light
colors
These light and dark colors
are known as belts and
zones
JUPITER’S ROTATION
Belts are low, warm, dark coloured clouds that sink
Zones are high, cool, light coloured clouds that rise
JUPITER’S MOONS
Jupiter has more than
60 moons, most of
which are really small
Jupiters four largest
moons are
Io, Europa,
Ganymede, and
Callisto
All 4 of the moons are
made up of rock and
ice
JUPITER’S MOONS
Because of the gravitational
pull of Jupiter, scientists
believe the they have been
squeezed and heated when
they were formed
Io, is almost completely molten
inside and undergoes constant
volcanic eruptions!
JUPITER’S MOONS
Europa has many cracks and water channels because it is
thought that gravitational heating has melted the ice on
Europa’s surface
Astronomers hypothesize that it still has subsurface oceans
of liquid water
SATURN
Saturn is the second largest planet in our solar system
Five space probes have visited Saturn including
1. Pioneer 10
2. Pioneer 11
3. Voyagers 1 and 2
4. Cassini
ATMOSPHERE AND
INTERIOR
Saturn is slightly smaller than Jupiter
It has a layered cloud system and the
planet spins quite quickly for its size
Saturn’s atmosphere is mostly made up
of hydrogen and helium with ammonia ice
near the cloud tops
Magnetic field similar to Jupiter that has a
small solid core and fluid throughout
RINGS
The rings of Saturn
are large chunks of
ice and dust with ice
attached to the
particles
The rings are more
visible than other
planets because it
has 7 major ring
systems
As you move closer
to the planet, the
rings get narrower
called ringlets
RINGS
You will never see satellites or moons forming in the rings
because the gravitational force and prevented them from
forming.
The satellites will form just past the ring systems
MOONS
Saturn has more than 55 satellites including the giant Titan,
which is larger than the planet Mercury
In 2005, scientists sent a probe to collect data on Titan and
found it has a dense atmosphere made up of nitrogen and
methane
URANUS
The blue color of Uranus is caused by
methane in its atmosphere, which reflects
blue light
Uranus’ average temperature is -215°C
In 1986, Voyager 2 flew by Uranus which
provided detailed information about the
planet
ATMOSPHERE
Uranus is 4 times larger and 15 times more massive than
Earth.
Uranus is made up of mostly helium and hydrogen
There are few clouds
STRUCTURE
The structure is very similar to that of Jupiter and Saturn
It is completely fluid except for a small, solid core
It also has a strong magnetic field
MOONS AND RINGS
Uranus has at least 27 moons and a faint ring system
Uranus’ rings are very dark, almost black and faint
ROTATION
Uranus is tipped so far the its north
pole lies on its orbital plane!
Scientists believe the planet had a
large collision with an asteroid
which caused it to be ‘knocked
over’
Each pole spends 42 Earth years in
darkness and 42 years in sunlight
due to this tilt
NEPTUNE
Few details can be observed with an Earth-based telescope,
but in 1989 Voyager 2 flew past and took a picture of its
cloud-streaked atmosphere
Neptune is the last of the gas giant planets and orbits the sun
almost 4.5 billion km away
ATMOSPHERE
Smaller and less dense than Uranus
Radius is 4 times larger than Earth’s
Neptune also looks blue due to the methane
in the atmosphere
Neptune has distinctive clouds and belts and
zones like Jupiter
ATMOSPHERE
In fact, Neptune once
had a persistent
storm, called the Great
Dark Spot, similar to
Jupiter’s Great Red
Spot
It disappeared in 1994
MOONS AND RINGS
Neptune has 13 moons, the largest which is called Triton
Triton has a retrograde orbit, which means that it orbits
backwards compared to the other moons
Triton has geysers caused by polar ice made from nitrogen
expanding and erupting when heated by the sun
RINGS
Neptune has 6 rings made up of microscopic dust particles,
which do not reflect light well, therefore the rings are not
visible from Earth like Saturn’s are