A Storm that is Shaped Hexagonal

Ever heard of a storm that's hexagonal in shape? Well, that sounds strange but it's actually known to exist on the ringed planet of our solar system - The Mighty Saturn

The strange Hexagonal storm spins over the northern hemisphere of Saturn; Credits: Space.com

When staring at a picture of Saturn, it's easy to get so distracted by all the rings that we don't notice the bizarre hexagon shaped winds on the top of this gas giant. These unusual storms are powerful, reaching speeds of 1,100 miles per hour (1,800 kilometers per hour) as they grow to the size of Earth. Yes! You read it correct, these storms are massive to the size of our planet.!

The Discovery

The bizarre hexagonal cloud pattern was first discovered in 1988 by scientists reviewing data from NASA's Voyager flybys of Saturn in 1980 and 1981, but its existence was not confirmed until NASA's Cassini spacecraft observed the ringed planet up-close years later. In 1988, scientists noticed, while sifting through Voyager data, that there was a massive hexagon at the planet’s north pole. In 1997, NASA launched the Cassini spacecraft on a mission to Saturn from which we know that today, the hexagon has a tight spiral at its center, it is about 100 km thick, and it has changed colour slowly over the years: from generally blue up to 2012 to mostly yellow now. This marvelous storm has been named 'The Hexagon' by researchers.

Credits: NASA/JPL

Nothing like 'the hexagon' has ever been seen on any other world. The structure, which contains a churning storm at its center, is about 20,000 miles (32,000 kilometers) wide, and thermal images show that it reaches roughly 60 miles (100 km) down into Saturn's atmosphere.

Now a storm on Saturn is not surprising by itself. But how did this one get shaped into a more or less permanent hexagon?

Conclusions so far

We have clues. Scientists noticed that the hexagon rotates at nearly the same speed that Saturn itself rotates on its own axis—so it appears almost stationary on Saturn. The images from Cassini also suggest the presence of a powerful current of air—what we call a jet-stream here on Earth—flowing east, along the borders of the hexagon, at about 350 km per hour. That’s speedy, but it’s not the highest wind speed detected on Saturn—so wind speed alone does not cause this shape.

Credits: NASA/JPL

In 2010, a team of Portuguese scientists  wrote a paper explaining that at the hexagon’s border, there’s a dramatic change in wind speeds. Meaning that right there, you’ll find adjacent segments of Saturn’s atmosphere moving at very different speeds. The scientists concluded that it’s the way these segments move against each other that’s responsible for the hexagon.

They experimented with liquids in concentric containers, moving them at different speeds and observing what happened. At certain speed differences, a distinct wavy motion emerged at the boundary between the liquids. On Saturn, such waves would circle the planet at the latitude where the hexagon forms (about 78 degrees North), meeting themselves after going all the way round. The latitude and the length of that circumnavigation determine how many such waves form—in this case, six. This is why we get a hexagon: if the wind speed change happened further north, Voyager and Cassini might have stumbled upon a pentagon instead. The hexagon is so big, in fact, that "small" vortices inside of it are often twice as wide as the largest hurricanes on Earth.

The Hexagon with the small whirlpools visible; Credits: NASA,JPL

The Puzzle is endless!

This hexagon has many more mysteries enrolled inside it that scientists are working on, like the mysterious change in the colour of the hexagon and many more. Researchers are unable to fully understand this extraordinary hexagon despite years of observation through Cassini.

NASA's Cassini wrapped up 20 historic years in space, as it crashed into Saturn's atmosphere and burned up like a meteor on September 15th, 2017.
Cassini, after its immense contribution towards this ringed beauty, finally met the hexagon it chased for so long..

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Splendid shots by Cassini Spacecraft; Credits: NASA

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