July 22, 2008—Wispy, "night shining" clouds float at an altitude of 250,000 to 280,000 feet (76 to 85 kilometers), lit by sunlight while much of Earth's lower atmosphere and horizon remain dark.

An astronaut captured this image in the pre-dawn hours as the International Space Station soared some 200 miles (321 kilometers) over western Mongolia.

Also called polar mesospheric clouds, night-shining clouds occur at high latitudes in each hemisphere. The transient phenomena aren't fully understood.

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