Some stunning recent images of the atmospheric vortex at the center of Saturn’s north polar hexagon were caught by NASA’s Cassini spacecraft this week. The images were taken during the latest of Cassini’s ring-grazing orbits, which have so far produced spectacular glimpses of Saturn’s rings, and its wonderfully pasta-shaped moons. And now, this.
Image: NASA/JPL-Caltech/SSI/Jason Major
This wouldn’t be the first time Saturn has displayed uncanny, chameleon-like abilities. In fact, the image above is pulled from a press release NASA issued last October, which noted a striking color change across the entire north polar hexagon from 2012 to 2016. Here’s a GIF that illustrates its evolution over time:
NASA has hypothesized that the color change between 2012 to 2016 was due to “increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017.”
In other words, as Saturn’s north pole tilted sunward, interactions between sunlight and atmospheric compounds that produce haze started increasing, changing the hexagon’s overall hue. As Kunio Sayanagi of the Cassini Imaging team noted in 2013, the hexagon acts as a particle barrier “like Earth’s ozone hole.”
It’s difficult for bits of the atmosphere to cross in and out, so any chemical changes within the hexagon tend to stay within the hexagon.