Atmosphere

A = Original atmosphere of hydrogen, methane and ammonia
B = Water added from cooling rocks
C = Carbon dioxide and sulphur dioxide added by volcanoes
D = Oxygen produced by photosynthesis

Atmosphere the layer of gases around a planet, particularly the Earth. Scientists Divide the Earth's atmosphere into several layers which, from the ground upwards, are troposphere. Among the other planets in the solar system, Venus has a thick atmosphere; Mars has a slight atmosphere; and Jupiter and the other outer planets have a very thick atmosphere.

Whereas Earth's atmosphere consists of air, those of Venus and Mars are mainly carbon dioxide; and those of the outer planets, hydrogen and helium.