Ultra-rare 'rainbow clouds' light up the Arctic Circle like auroras in stunning new photos

The dark skies in the Arctic Circle recently shone with ethereal multi-colored light. But this jaw-dropping spectacle was not caused by auroras. Instead, the iridescent rainbows were caused by clouds of tiny ice crystals floating higher in the atmosphere than is normally possible.

The clouds, known as polar stratospheric clouds (PSC), only form when the lower stratosphere reaches temperatures below minus 114 degrees Fahrenheit (minus 81 degrees Celsius). Normally, clouds do not form in the stratosphere because it is too dry, but at these extremely low temperatures "widely-spaced water molecules begin to coalesce into tiny ice crystals" that form into clouds, Spaceweather.com(opens in new tab) reported. This means PSCs can form much higher up than normal clouds, between 9.3 and 15.5 miles (15 to 25 kilometers) above the ground.