Saturn’s Polar Hexagon Is The Haziest Place In The Solar System

Saturn hexagon as seen by Cassini. NASA/JPL-Caltech/Space Science Institute

The north pole of Saturn is a peculiar place where clouds end up in an incredible hexagonal pattern. The exact mechanism for this unusual shape is not clear but we have a few ideas about it. Just to make the interplanetary weather forecast even more special, researchers think that the region has the most extensive system of haze layers ever observed in the Solar System.

High-resolution images captured by the Cassini mission in 2015 have revealed the layers in this strange wave structure that surrounds Saturn's north pole. The spacecraft was in an ideal position to look at the limb of the hexagon and was able to study the upper level of the atmosphere, revealing seven stacked haze layers above the clouds, with each layer ranging between 7 and 18 kilometers (4.3 to 11.2 miles) thick. 

“The Cassini images have enabled us to discover that, just as if a sandwich had been formed, the hexagon has a multi-layered system of at least seven mists that extend from the summit of its clouds to an altitude of more than 300 km above them,” lead author Professor Agustín Sánchez-Lavega, from the University of the Basque Country, said in a statement. “Other cold worlds, such as Saturn’s satellite Titan or the dwarf planet Pluto, also have layers of hazes, but not in such numbers nor as regularly spaced out”.

The layers over Saturn's Hexagon. UPV/EHU

Reported in Nature Communications, the team was able to see details as small as one 1-2 kilometers by combining the Cassini observations with ones by Hubble. The team was able to estimate that these haze layers were made of micron-sized particles, possibly some hydrocarbon ice. The full haze system is about 80 miles (130 kilometers) thick.

The hexagon in glorious false colors. NASA/JPL-Caltech/SSI/Hampton University

Another interesting aspect of this complex haze system is how it formed. The team suspects gravity waves as the culprit. These shouldn’t be confused with gravitational waves, which are oscillations of space-time. Gravity waves form in a fluid at the surface boundary between two media, for example, ocean waves.

The researchers suggest that differences in density and temperature (well below zero degrees) and the dynamics between the hexagon and the jet streams around the pole, produce gravity waves that allow for the vertical propagation of gravity waves, forming the hazy layers that Cassini detected.

Cassini was a joint mission between NASA, the European Space Agency, and the Italian Space Agency, studying the Saturn system between 2004 and 2017.

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