Mysterious Night-Shining Clouds Illuminate Mediterranean Sky

Polar mesospheric clouds, also known as noctilucent or night-shining clouds, are becoming brighter and more visible over mid-latitudes, as observed by an astronaut aboard the International Space Station (ISS). These wispy structures form at altitudes of just over 80 kilometers and are the highest-altitude clouds in Earth's atmosphere. Previously limited to higher latitudes, the clouds are now increasingly visible to observers in middle latitudes. Scientists are investigating the reasons behind this change, including increased humidity in the mesosphere and the impact of exhaust plumes from space vehicle launches.