Some of the best views of Earth come from beyond our home planet, as recently captured by astronauts aboard the International Space Station (ISS). In late October, astronauts saw Earth covered in a green sheen, a phenomenon called airglow.

What is it?

Airglow is a faint light emitted by Earth's upper atmosphere, produced when molecules emit energy after being excited by cosmic rays or ultraviolet solar radiation. Although far dimmer than auroras, airglow forms a continuous global layer and is always present, both day and night, though it's best visible from space.

Where is it?

This image was taken from low Earth orbit as the ISS flew 260 miles (418 kilometers) above Texas.

Why is it amazing?

Airglow is more than just visually stunning; it can also be used as a diagnostic tool for und

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