Saturn’s polar hexagon has changed from blue to gold

Two pictures taken with natural light from NASA’s Cassini spacecraft have shown a shifting color of the atmosphere around Saturn’s north polar area between 2012 and 2016. Researchers are looking into possible causes for the difference in color.

The color change is thought to be a result of Saturn’s seasons. Specifically, the shift from a bluish color to a yellow hue may be as a result of elevated production of photochemical hazes in the atmosphere as the north pole gets closer to Saturn’s summer solstice in May 2017.

Scientists said the hexagon, which is a six-sided jet stream, might serve as a wall that stops haze particles generated outside it from coming in. Throughout the polar winter night, between November 1995 and August 2009, Saturn’s north polar atmosphere became free from aerosols generated by reactions between sunlight and the atmosphere, also known as photochemical reactions. Because the planet passed equinox in August 2009, the polar atmosphere has been ensconced in continual sunshine, and aerosols are being generated within the hexagon that sits around the north pole, making the polar atmosphere appear hazy today.

Other effects, including variations in atmospheric circulation, may also be playing a part. Researchers have said seasonally moving patterns of solar heating most likely had an impact on the winds in the polar regions.

In 1980 and 1981, NASA’s Voyager 1 and 2 space probes gave us the first looks at the top of Saturn, situated more than 930 million miles from the Sun. Among their several discoveries, the probes showed a strange, hexagon-shaped design in the planet’s uppermost clouds around its north pole. The hexagon stayed virtually static, without moving relative to the planet’s overall rotation, which was not accurately known at the time. The pictures captured by the Voyager probes indicated the clouds were moving quickly inside the hexagon in an enclosed jet stream and were being pulled by winds moving at more than 250 miles per hour. Observations made 30 years later revealed the hexagon and its jet stream have remained largely unchanged.

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Image credit: NASA

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