Polar stratospheric cloud over Iceland

This is an incredible image of one of the rarest and most beautiful types of clouds in the world. It goes by three different names and it forms in the stratosphere around 49,000 to 82,000 feet in altitude.

Named after the French word "nacré", meaning "mother of pearl", these types of clouds can be known as Nacreous, Mother of Pearl or Polar Stratospheric Clouds. They only occur close to the poles during the cold winter season.

This cloud only forms when temperatures in the stratosphere drop below -108.4 F and when the air is saturated with super-cooled liquid and ice crystals.

When the sun is located below the horizon, its rays are refracted through the ice crystals in the stratosphere, known as cloud iridescence, and causes the shimmering rainbow to form over the cloud. The higher the sun on the horizon, the more colors are seen.