Inner & Outer Planets

all inner planets ...

• have at least one moon
• have thick atmosphere
• are rocky and have a solid outer layer

because Mercury's mass is so small, it

• does not rotate
• has no atmosphere
• has a surface that is not solid

why is Venus the hottest inner planet ?

• it is covered with liquid water
• it is the closest planet to the Sun
• its atmosphere traps a lot of heat energy

Earth is the only planet with a wide variety of life because of its

• size and shape
• closeness to the Sun
• moderate temperature and liquid water

why do scientists think that liquid water might have once existed on Mars?

• Mar's surface has deep gullies on it
• the southern half of Mars is covered with craters
• the largest known mountain in the solar system is on Mars

How is Venus unlike other planets?

• it has a solid inner core
• it has a very thin atmosphere
• its period of rotation is longer than its period of revolution

which inner planet has the longest period of revolution and why?

• Venus, because it spins very slowly
• Mercury, because it is closest to the Sun
• Mars, because it is farthest from the Sun

all the outer planets are made mostly of 

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

which planet is the solar system's largest?

• Jupiter
• Saturn
• Neptune

the outer planets have atmospheres composed mostly of

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