Polar Stratospheric Clouds (PSCs) are unique cloud formations that occur in the stratosphere, typically at altitudes of 15 to 25 kilometers (9 to 16 miles) during the winter months in polar regions. They form in extremely cold temperatures, often below -78 degrees Celsius (-108 degrees Fahrenheit), and are composed mainly of ice crystals and nitric acid. These clouds play a significant role in the depletion of ozone in the stratosphere. When sunlight returns to the polar regions in spring, it triggers chemical reactions on the surface of PSCs, releasing chlorine compounds that can break down ozone molecules, contributing to the thinning of the ozone layer.