“Cassini is different — it’s a mission of enormous scope and is being conducted in grand style. It is much more sophisticated than Voyager, … I can’t say it’s got that flavor of romance, though. Voyager was very romantic. Cassini is spectacular.” -Carolyn Porco
It was a big enough mystery when Saturn’s hexagon was first discovered by going back to archival Voyager data, and then confirmed by Cassini. Over the past 36 years, Saturn’s hexagon has not only persisted, it’s remained completely unchanged in size, extent and speed over that time. An artifact of fluid dynamics and the wind speeds at the northern latitudes, the hexagon is a quasi-stable structure that will likely outlive us all.
Cassini’s true-color view of the north pole before the color change occurred. Image credit: NASA / JPL-Caltech / Space Science Institute.
But the color of Saturn’s hexagon has changed over time, and not even over very long timescales. Since the north pole came back into sunlight in 2009, it was observed to be blue in color. But from 2012 to 2016, it gradually yellowed, having now achieved a color almost in sync with the rest of the planet. As solstice approaches next year, this effect should only intensify.
As Saturn approaches solstice in its orbit, the yellows are expected to intensify, but the hexagon should remain unchanged in structure. Image credit: NASA / JPL-Caltech / Space Science Institute.