Johan

Rare clouds that give off bright, multi-colored light like an aurora were recently spotted at multiple locations in the Arctic. But what causes them?

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. 

As sunlight shines through these crystal clouds, it gets scattered, creating multiple different wavelengths of light, which has inspired the PSCs nickname, "rainbow clouds."  Due to the extreme altitude of the clouds sunlight can hit the crystals and scatter above an observer even if the sun is beyond the horizon, which is when these clouds appear brightest. 

On Jan. 25, extreme freezing conditions in the stratosphere allowed for a rare outbreak of PSCs across the Arctic Circle, including Iceland, Norway and Finland, according to Spaceweather.com. Amateur photographer Jónína Guðrún Óskarsdóttir(opens in new tab) captured a stunning shot of the vibrant clouds above the peak of Mount Jökultindur in Iceland and photographer Fredrik Broms(opens in new tab) took a series of snaps of the colorful lights above Kvaløya near Tromsø in Norway.