Summer ice clouds shine high above the Earth

Caroline Morley, online picture researcher

(Image: courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center)

You don't have to be a druid to have a mystical experience around the summer solstice. An astronaut aboard the International Space Station has captured the immaterial appeal of polar mesospheric clouds as seen from orbit.

These are a type of noctilucent clouds, which are visible at dawn and dusk when the angle of the sun means they are illuminated but the Earth's surface is in darkness. Noctilucent clouds are formed of layers of ice crystals 76 to 85 kilometres above the surface in the mesophere. Polar mesospheric clouds only occur at the two polar regions in the weeks surrounding their respective summer solstices.

Noctilucent clouds seem to be becoming more common and spreading further south but there is no consensus about the underlying cause. Suggestions include meteor dust, climate change and rocket exhaust.

michael kidd gilchrist national championship calipari national archives brock lesnar kentucky jayhawks