The outer planets are called the terrestrial planets.

• True
• False

An astronomical unit is the average distance

• from Earth to Mars.
• from Earth to the Sun.
• from Earth to the Moon.
• from Earth to the asteroid belt.

Which outer planet has a sideways axis of rotation?

• Jupiter
• Saturn
• Uranus
• Neptune

Which outer planet is about the same size, makeup, and structure as Uranus?

• Jupiter
• Saturn
• Neptune

Earth, Mars, Mercury, and Venus are the 

• gas giants.
• terrestrial planets.

The greenhouse effect occurs when a planet's atmosphere traps solar energy and causes the surface temperature to increase.

• True
• False

All of the outer planets are mostly made of

• water ice.
• metal and rock.
• gas and liquid around a solid core.

Which planet is the solar system's largest?

• Jupiter
• Saturn
• Uranus
• Neptune

The outer planets have atmospheres composed mostly of

• nitrogen and oxygen.
• hydrogen and helium.
• water vapor and carbon dioxide.

Which planet has a moon that is larger than the planet Mercury?

• Jupiter
• Saturn
• Uranus
• Neptune