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dark sky in Arctic Circle It recently shone with a multicolored ethereal light. But this amazing sight wasn’t caused by the Northern Lights. Instead, iridescent rainbows were caused by clouds of tiny ice crystals floating higher in the atmosphere than would normally be possible.
The clouds, known as polar stratospheric clouds (PSC), only form when the temperature of the lower stratosphere reaches minus 114 degrees Fahrenheit (minus 81 degrees Celsius). Normally, clouds don’t form in the stratosphere because it’s so dry, but at these extremely low temperatures, “widely spaced water molecules begin to coalesce into tiny ice crystals” that form in clouds, Spaceweather.com (Opens in a new tab) mentioned. This means that special stem cells can form much higher than normal clouds, between 9.3 and 15.5 miles (15 to 25 kilometers) above the Earth’s surface.
When sunlight shines through these crystal clouds, it scatters, creating several different wavelengths of light, which inspired the PSCs’ nickname, “rainbow clouds.” Because the clouds are so high, sunlight can strike the crystals and scatter over an observer even if the sun is behind the horizon, which is when these clouds appear brightest.
On January 25, severe freezing conditions in the stratosphere allowed for a rare proliferation of stem cells across the Arctic Circle, including in Iceland, Norway and Finland, according to Spaceweather.com. amateur photographer Junina Goran Askarsdottir (Opens in a new tab) Take a stunning photo of the vibrant clouds above the peak of Mount Jökultindur in Iceland and the photographer Frederick Promes (Opens in a new tab) Take a series of shots of the colorful lights over Kevalua near Tromsø, Norway.
Related: The solar storm blows a hole in Earth’s magnetosphere, causing extremely rare pink aurorae
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There are two types of PSCs: Type 1, which is made of a mixture of ice crystals and nitric acid, which produces less exciting colors and may be related to the formation of ozone holes. and Type II, which are composed of pure ice crystals and produce brighter colors. The species that formed recently over the North Pole were of the second type.
Type II PSCs are often referred to as nacreous clouds because their iridescent colors can sometimes resemble mother-of-pearl, also known as mother-of-pearl, which is produced in the shells of some molluscs. However, they are much rarer than Type I clouds.
Type II clouds typically occur no more than two or three times a year in the Arctic, usually during the colder winter months, according to Spacewaether.com. However, experts believe that both types of PSCs could occur more often in the future as climate change causes more extreme weather, which could have a detrimental effect on the ozone layer if more Type 1 clouds are formed, according to NASA (Opens in a new tab).
Because of their intense colors, dark clouds are often confused with northern lights, or the aurora borealis, in the North Pole. These phenomena most commonly occur when high-energy particles emitted from the sun travel through the magnetic field lines of the Earth’s magnetosphere.