These clouds, also referred to as Noctilucent Clouds, exist approximately 80-85 km (≈50-53 miles) above the Earth’s surface near the coldest part of the atmosphere, the mesosphere. They become visible when tiny water particles (about 1/10,000 mm in diameter) in the upper atmosphere freeze into ice and reflect the sunlight. Polar Mesospheric clouds oftentimes appear in bluish hues because the stratospheric ozone layer absorbs most of the red light.
The formula for the development of these clouds in simple: low temperatures, water vapor, and a surface/nuclei for the water crystal to grow on. Once these criteria have been met, science takes over and with enough frozen water vapor and light the noctilucent clouds come to life. Next time you step outside and bear witness to these magnificent blankets that hover the horizon, thank the sun and the conditions of Earth’s upper atmosphere. Without either, the presence and existence of polar mesospheric clouds would be in question.