The mass of air surrounding the Earth.

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The mass of air surrounding Earth is the atmosphere, the gaseous envelope held in place by gravity. This layer contains gases like nitrogen and oxygen and drives weather, climate, and the transfer of heat and energy between the sun and the surface. It also protects living things by absorbing harmful radiation. By contrast, the hydrosphere is all water, the biosphere includes all living organisms, and the lithosphere is the solid crust and upper mantle; these terms describe different parts of Earth’s system, not the air around it.