Earth's atmosphere from space, showing a blue layer at the stratosphere, above the clouds of the troposphere. The Moon is visible as a crescent in the background.[1]

A Blanket With No Edge

Earth's atmosphere is a layer of gas held by gravity, but it has no sharp border with space. The Kármán line at 100 km is a practical marker, not a physical wall.

Earth's Atmosphere and the Edge of Space

Serene aerial view of a vast expanse of white clouds against a clear blue sky.

Most Of It Hugs The Ground

The atmosphere sounds vast, but three quarters of its mass sits within about 11 km of the surface. Half of all atmospheric mass is packed into the lower 5.6 km.

Earth's Atmosphere and the Edge of Space

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