Sometimes deep into the winter, after sunset or before dawn, sheets of unbelievably bright and vividly colored clouds can be seen forming against the partially dark twilight sky. This rare type of cloud formations are known as “polar stratospheric clouds” or “nacreous clouds”, and they can only be seen from high latitude regions such as Iceland, Alaska, Northern Canada, the Scandinavian countries and Antarctica. The Scandinavians call them “mother of pearls” because of their spectacular iridescent colors. Described as “one of the most beautiful of all cloud formations,” nacreous clouds are also the most destructive to our atmosphere. Their presence encourages a chemical reaction that breaks down the ozone layer, which is an essential shield protecting us from the sun's harmful rays.

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