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What happens at the turbopause about 100 kilometres above Earth?

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Wispy cirrus clouds stretch across a bright blue sky above trees and a river at Pinawa Dam Provincial Park in Manitoba, Canada, with sunlight illuminating the scene. — Atmosphere The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.

The turbopause, located at an altitude of approximately 100 kilometres, serves as the transition zone between two major atmospheric regions: the homosphere and the heterosphere.1

Below this altitude, in the homosphere, turbulent mixing is the dominant process, which keeps the chemical composition of the atmosphere relatively uniform regardless of height. At the turbopause, this dominance of turbulent mixing gives way to molecular diffusion.1

Consequently, above the turbopause in the heterosphere, atmospheric gases are no longer mixed uniformly; instead, they are separated by molecular mass. In this higher region, lighter gases become concentrated in the upper layers, while heavier gases decrease in concentration with increasing altitude.1