7.9A Characteristics of the Solar System

What characteristics of the planet, Earth, is essential to the survival of living organisms?

• Earth has abundant available water
  
• Earth has just one orbiting moon.
• Earth orbits the Sun once every 365 days
  
• Earth rotates on its axis once every 24 hours.

Layer of ozone in upper atmosphere of Earth is important to life because it shields Earth from

• changes in temperature.
• ultraviolet radiation.
• solar winds.
  
• impacts from meteors.

The magnetic field of Earth protects life against 

• debris ejected from the Moon.
• ultraviolet radiation from the stars.
  
• high energy particles from the Sun.
• falling meteors from outer space.
  

Earth is 150 mil. km from the Sun. If it was 200 mil. km away, it wouldn't support life because

• there would be less exposure to solar wind.
• the oxygen would leave the atmosphere.
• the temperature would be too cold.
• the surface water would evaporate
  

What is the most important factor that determines Earth’s temperature?

• Distance to the Moon
  
• Gas composition of the atmosphere
• Proximity to the Sun
• Amount of water on the planet

The habitable zone for the star is about 25 mil. km away. Which planet can support life?

• Planet W
• Planet X
• Planet Y
• Planet Z

What discovery about Mars suggests conditions that may have once supported life? Mars has

• small amounts of water in the soil
• only a small amount of atmosphere.
• two moons orbiting the planet
• the tallest mountain in the solar system.

 Ozone contributes to supporting life on earth by blocking 

• ultraviolet light.
  
• water vapor.
• helium ions.
  
• atmospheric heat.

If Earth were much smaller, 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 once per day.

What data could be collected, that gives scientists info about if life exists on that planet?

• The number of other planets in the system
• How long the planet takes to rotate
• The orbit length of the planet
• The presence of an atmospheric ozone layer