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