Greenhouse Effect

It's a thin layer of gases surrounding our planet.  Many of the planets in this solar system have atmospheres, but none that we know of have an atmosphere quite like ours - one that can support life.

The atmosphere is held to the planet by the force of gravity, which also determines what gases are present in it.

The Earth's primitive atmosphere was much different from today's and consisted primarily of ammonia, methane, and trace amounts of carbon dioxide and water vapour.  There was little, if any, free oxygen present.

The atmosphere decrease in concentration, and hence pressure, as you rise above the surface of the earth. (To read more)

National Geographic - 5 min

Visual Learning - 2 min