The atmosphere. This can be broken down further into layers.
An atmosphere.
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An atmosphere
An atmosphere
An outer layer of gas on a planet is called an atmosphere.
An atmosphere.
The outer layer is atmosphere.
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An atmosphere
An atmosphere
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The outer layer of gas around the terrestrial or rocky planets is called the atmosphere, although Mercury's is so sparse that it is referred to an an exosphere (as if space began at its surface).
The gas surrounding any planet is called its atmosphere.
The crust is the outer or surface layer of the planet.