WEEK 3

• Earth is the only planet that is known to sustain life in our solar system
• One of the factors that make our planet habitable is its atmosphere
• Atmosphere


  The blanket or envelope of gases surrounding the earth
• Atmosphere


  • Keeps us warm
  • Gives us oxygen to breathe
  • Where weather happens
  • Keeps the overall temperature of the earth fairly steady especially between night and day
• Gases in the atmosphere

  • 78% nitrogen
  • 21% oxygen
  • 1% other trace gases including carbon dioxide, inert gases, hydrogen, methane, ozone
• Layers of the atmosphere

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• Basis for dividing atmosphere into layers

  Change of temperature with height
• Troposphere


  • Lowest layer
  • 75% of total mass of atmosphere
  • 99% of atmosphere's water
  • Where wind, clouds, and water vapor are found
  • Where weather phenomena takes place
  • Air is constantly moving
• Stratosphere


  • Air flow is more stable than troposphere
  • Ozone layer is found here
  • Ozone layer protects from harmful ultraviolet rays
• Mesosphere


  • Temperature decreases with height
  • Coldest layer
  • Burns up most meteors and asteroids before reaching Earth's surface
• Thermosphere


  • Closer to the sun
  • Absorbs a large amount of solar radiation
  • Temperature increases tremendously
  • International Space Station and space shuttles orbit in this layer
• Ionosphere


  • Ion-rich region within the thermosphere
  • Auroras are seen here
• Exosphere


  • Merges into outer space
  • Temperature varies from very hot to very cold
  • Ideal for placing artificial satellites as there is little friction