Unlike anything else in the solar system, Saturn’s north pole is home to a six-sided jet stream in its atmosphere known to scientists simply as "the hexagon." First spotted by the Voyager mission in 1981, the hexagon has fascinated scientists but eluded attempts to capture it in detail on camera. Launched in October of 1997 and arriving in Saturn's orbit in July of 2004, the Cassini spacecraft was sent to study Saturn and its moons. And though it had brought us closer than ever, lighting conditions had kept it from taking a full, detailed picture of the phenomenon. But things are different now.
The problem was winter. The lack of sunlight illuminating Saturn's north pole would keep it in the dark until 2009, when the gas giant's spring season came around and allowed us to get our first detailed look at the enormity of the hexagon.
While the interior of the hexagon remained a mystery,the air current that makes up the hexagon is quite clear, as well as the sheer number of hurricanes and storm systems that surround it in perpetuity, like this one that Cassini filmed a year ago:
However, in late 2012, light began to illuminate the pole's interior, and the probe has been able to observe the hexagon even more clearly than before. Taken over a 10-hour time span with high resolution cameras, NASA was able to obtain a clear, moving image of the planet’s distinct air current and its surrounding storm systems. The images were then analyzed through a rendering method knowns as false color, which allows the different types of particles suspended in the atmosphere to be easily identified.
The view will only get better as we approach 2017, Saturn’s summer solstice—and Cassini's projected end of life. It’s a great end to a year full of breathtaking images taken by the Cassini, like this past summer’s “Day the Earth Smiled,” the first time NASA informed the world that it would be taking a picture of Earth from space in advance. Here are some great ones:
In order to capture these images, the Cassini makes use of its Imaging Science Subsystem (ISS), a remote sensing instrument that can capture images in most visible light, along with some infrared and ultraviolet capabilities. The instrument is outfitted with both wide- and narrow-angle cameras that are equipped with charge-coupled devices for use as an electromagnetic wave detector. Per Wikipedia:
"Each CCD has a 1,024 square array of pixels, 12 μm on a side. Both cameras allow for many data collection modes, including on-chip data compression. Both cameras are fitted with spectral filters that rotate on a wheel—to view different bands within the electromagnetic spectrum ranging from 0.2 to 1.1 μm."