One of the solar system’s largest — and perhaps the most geometric — storm systems surrounds the north pole of Saturn. This prominent feature of Saturn’s atmosphere not only appears as a geometric hexagonal pattern, but it has also sported a distinctive blue hue, contrasting with the pale golden atmosphere that makes up the rest of Saturn’s clouds to the south. But recently, it has been found that the region has made a dramatic chromatic shift, turning from its typical blue color, to gold.
First spotted in 1981 by the Voyager space probe, the 32,000 km-diameter (20,000 mile) storm system appears to be formed by a series of six smaller storms that are situated at a latitude of roughly 78ºN. Between these smaller storms are jetstream-like winds that tear along at speeds of 321 km/h (200 mph), forming a barrier between the northern and southern atmosphere that extends 100 km (60 miles) down into the clouds.
The prevailing theory behind the abrupt change in color is that Saturn’s polar clouds are being affected by its increased exposure to sunlight as it transitions into summer, as explained on NASA’s Photojournal:
"The colour change is thought to be an effect of Saturn’s seasons. In particular, the change from a bluish colour to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017."
It is thought that the barrier created by the winds that form the hexagon’s sides keep the southern atmosphere, colored gold by its daily exposure to sunlight, from mixing with the polar atmosphere, that receives no sunlight during Saturn’s northern winter. As each of the planet’s seasons last for 7.36 Earth years, the gasses inside the hexagon began warming up roughly three years ago, when the planet experienced its most recent equinox.
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