1. Atmosphere The atmosphere is a very thin layer of gases wrapped around the earth.

2. Green House Gases The earth’s atmosphere contains gases that trap heat from the sun. The trapped heat cause the Earth to warm. Such gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbon (CFCs). Methane Fluorocarbon Nitrous Oxide Carbon Dioxide

3. Green House Gases Carbon Dioxide, CO 2,is a transparent, non inflammable gas that is recycled by the atmosphere through photosynthesis. Methane, is a colorless, odorless, flammable gas. It is formed when plants decay. Nitrous Oxide gas is colorless, but has a sweet smell. This compound is released by the ocean and by bacteria in soil. Fluorocarbons is a general term for any group of synthetic organic compounds that contain fluorine and carbon.

4. Earth The Earth has just the right amount of green house gases to survive. Too much gases will make the Earth too warm to live in, as in the case of Venus. Too little gases will cause the Earth to become too cold for life. An example of this is Mars.

5. Planets Orbiting The Sun

6. Goldilocks Principle It is used to state that a planet must neither be too far away nor too close to the sun to support life. Venus is too hot, Mars is too cold, but Earth is just right.

7. Atmospheric Factors Responsible For The Planetary Difference

8. Chemical Composition of the Atmospheres

9. References http://www.ucar.edu/learn/1_1_1.htm http://www.pbs.org/wgbh/nova/ice/greenhouse.html http://www.umich.edu/~gs265/society/greenhouse.htm