Saturn’s Hexagonal Hurricane Is a Brilliant Bright Blue

Last week, NASA’s Cassini spacecraft plummeted antennae-first into the narrow gap between Saturn and its innermost ring. We’ve been watching in suspense as the newest raw images populate NASA’s website.

One of the research targets of the Cassini mission has always been Saturn’s hexagonal hurricane, which is spinning virulently at its north pole. Cassini swooped by the 1,200 mile-wide hurricane last week and took some close-up snapshots; astroparticle physicist Sophia Nasr then processed this photo (which was replicated by her one of her colleagues) and posted it to Twitter:

This bright aquamarine color is the result of scattered sunlight—it’s also why we see blue skies here on Earth.

NASA has a high-res movie of the hexagon in motion; the team reports that the eye of this hurricane is about 50 times larger than the average hurricane eye on Earth—and that its clouds are speeding along at 300 miles per hour.

NASA reports:

High-resolution views of the hexagon have only recently become possible because of the changing of the seasons at Saturn and changes in the Cassini spacecraft’s orbit. The north pole was dark when Cassini first arrived in July 2004. The sun really only began to illuminate the entire interior of the hexagon in August 2009, with the start of northern spring. In late 2012, Cassini began making swings over Saturn’s poles, giving it better views of the hexagon.

The eight frames of the movie were captured over 10 hours on Dec.10, 2012. Each of the eight frames consists of 16 map-projected images (four per color filter, and four filters per frame) so the movie combines data from 128 images total.

In this color scheme, scientists assigned red to the 0.750-micron part of the light spectrum (near infrared). This part of the spectrum penetrates the high-altitude haze layer to sense the top of tropospheric cloud deck. They assigned green to the 0.727-micron part of the light spectrum that senses the upper tropospheric haze (a near-infrared wavelength corresponding to a methane absorption band). They assigned blue to the sum of blue and ultraviolet broadband filters—combined, this blue channel covers between 0.400 and 0.500 microns (covering very near ultraviolet to blue in visible light). This part of the spectrum is sensitive to small aerosols.

To human eyes, the hexagon and north pole would appear in tones of gold and blue. See PIA14945 for a still image of the area in natural color.

A hurricane on Earth lasts a relatively short amount of time (about a week), but NASA scientists say that Saturn’s hurricane might be several decades old—and counting.