Noctilucent Clouds Over Germany

Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun,
sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on
clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual
noctilucent clouds float so high up they can be seen well after dark. Pictured above is a
network of noctilucent clouds cast an eerie white glow after dusk, beyond a local field
near Potsdam, Germany. Although noctilucent clouds are thought to be composed of
small ice-coated particles, much remains unknown about them. Satellites launched to
help study these clouds includes Sweden's Odin and NASA's AIM. Recent evidence
indicates that at least some noctilucent clouds result from freezing water exhaust from
Space Shuttles.