Protects life on Earth from harmful particles from solar winds.

• distance from the sun

• magnetic field

• atmosphere

• water

Keeps Earth's temperature stable and cool.

• distance from the sun

• magnetic field

• atmosphere

• water

Is necessary for life as we know it.

• distance from the sun

• magnetic field

• atmosphere

• water

Affects temperature of a planet.

• distance from the sun

• magnetic field

• atmosphere

• water

Earth's _____ helps protect life from ultraviolet radiation.

• water

• oxygen

• ozone layer

• ice

Earth's atmosphere is mostly made up of the gases _____ and _____.

• water and ice

• atmosphere and ozone layer

• oxygen and nitrogen

• oxygen and water

There is some evidence to suggest that Mars once had liquid _____ though now it may be trapped as _____.

• water, ice

• water, nitrogen

• oxygen, nitrogen

• nitrogen, ice

If Earth were much smaller than it is now, it would not support life because it would not have enough mass to -

• collect needed radiant energy from the Sun

• maintain a gravitational pull on the Moon

• have sufficient gravity to hold an atmosphere

• rotate on its axis

Ozone contributes to supporting life on earth by blocking -

• ultraviolet light

• water vapor

• helium ions

• atmospheric heat

Which of the following discoveries about Mars suggests conditions that may have once supported life? Mars has -

• the tallest mountain in the solar system

• two moons orbiting the planet

• only a small amount of atmosphere

• small amounts of water in the soil