noctilucent cloud

noun1

1. •
   Clouds characterized by their electric-blue or silvery-white, wispy streaks, filaments, or ripples high in the twilight sky; Earth's highest clouds, glowing at the edge of space, serving as indicators of climate change, showing increased frequency and visibility linked to human activities like methane emissions and rocket launches; maintain unique formation in frigid summer mesosphere, from ice crystals on meteoric dust, providing scientists with high-altitude atmospheric window into changes in upper atmospheric water vapor and dynamics.