Saturn polar hexagon caused by massive cyclones deep in the atmosphere

Giant hexagonal storm that has raged around Saturn’s north pole for over four decades is caused by massive cyclones deep in the planet’s atmosphere, study shows

  • Researchers created a computer model to simulate conditions found on Saturn
  • They then ran the simulation to see if a hexagonal polar storm would be formed
  • They found these storms require cyclones to start very deep inside the planet 

An unusual hexagon covering Saturn’s north pole may be the result of giant cyclones going deep into the ringed planet’s atmosphere, a new study shows.

This polar hexagon is 18,000 miles wide and has been observed for the past 40 years – since it was first discovered by the NASA Voyager mission in 1981. 

Researchers from Harvard University created a new atmospheric model in the lab to mimic the conditions found surrounding Saturn’s turbulent hexagon storm. 

They discovered that giant cyclones could be forming thousands of miles inside the gas giant, which intersect with jet flows and other airflows moving in different directions to create the hexagon.

Top is the hexagonal polar storm as captured on Saturn and below is the computer simulation created for this study of a similar gas giant showing a polygonal storm developing

The team, including Rakesh Yadav and Jeremy Bloxham, found that the storm is likely to go very deep – potentially thousands of miles into the gas giant planet. 

They created a computer simulation that mirrored conditions found on the ringed planet to try and recreate the hexagon – to find out how it first formed. 

In their simulations, a large cyclone arose around the north pole, with several smaller cyclones colliding with a strong eastward jet north of the equator. 

The main cyclone was strong enough to overcome the surface gas but the surrounding, smaller vortices were masked by the stronger surface gas.

The central cyclone started much deeper inside the gas giant simulation than the surrounding ones and so was able to overcome the turbulent surface gas.

However, the shallower vortices appeared more like polygonal jets than tornadoes. 

‘This cyclone on the north pole is surrounded by three anticyclonic vortices, several cyclonic vortices and a strong eastward jet north of the equator,’ they wrote.

In their simulation this eastward jet formed a polygonal shape with nine edges as a result of being pinched by the surrounding vortices – on Saturn this likely led to the creation of the hexagon shaped storm we see on the north pole.

This polar hexagon is 18,000 miles wide and has been observed for the past 40 years – since it was first discovered by the NASA Voyager mission in 1981. In their simulation the team recreated a similarly large cyclone on the pole, but it wasn’t a hexagon

They created a computer simulation that mirrored conditions found on the ringed planet to try and recreate the hexagon – to find out how it first formed

These vortices are apparent deep beneath the surface, and if the simulation is accurate, the same would happen for Saturn.  

‘The analysis of the simulation suggests that self-organised turbulence in the form of giant vortices pinches the eastward jet, forming polygonal shapes,’ they wrote.

‘We argue that a similar mechanism is responsible for exciting Saturn’s hexagonal flow pattern.’

Their simulation isn’t perfect. It only maps the outer tenth of the planet’s radius and the polar jets seem to only generate triangles instead of hexagons but they are confident it can help explain the process that creates the hexagon on Saturn.

Researchers say this is a proof of concept, rather than a full model of Saturn, as they need to incorporate more atmospheric data from Saturn to make it more realistic. 

The research has been published in the journal Proceedings of the National Academy of Sciences. 

WHAT DID CASSINI DISCOVER DURING ITS 20-YEAR MISSION TO SATURN?

Cassini launched from Cape Canaveral, Florida in 1997, then spent seven years in transit followed by 13 years orbiting Saturn.

An artist’s impression of the Cassini spacecraft studying Saturn 

In 2000 it spent six months studying Jupiter before reaching Saturn in 2004.

In that time, it discovered six more moons around Saturn, three-dimensional structures towering above Saturn’s rings, and a giant storm that raged across the planet for nearly a year.

On 13 December 2004 it made its first flyby of Saturn’s moons Titan and Dione.

On 24 December it released the European Space Agency-built Huygens probe on Saturn’s moon Titan to study its atmosphere and surface composition.

There it discovered eerie hydrocarbon lakes made from ethane and methane.

In 2008, Cassini completed its primary mission to explore the Saturn system and began its mission extension (the Cassini Equinox Mission).

In 2010 it began its second mission (Cassini Solstice Mission) which lasted until it exploded in Saturn’s atmosphere.

In December 2011, Cassini obtained the highest resolution images of Saturn’s moon Enceladus.

In December of the following year it tracked the transit of Venus to test the feasibility of observing planets outside our solar system.

In March 2013 Cassini made the last flyby of Saturn’s moon Rhea and measured its internal structure and gravitational pull.

Cassini didn’t just study Saturn – it also captured incredible views of its many moons. In the image above, Saturn’s moon Enceladus can be seen drifting before the rings and the tiny moon Pandora. It was captured on Nov. 1, 2009, with the entire scene is backlit by the Sun

In July of that year Cassini captured a black-lit Saturn to examine the rings in fine detail and also captured an image of Earth.

In April of this year it completed its closest flyby of Titan and started its Grande Finale orbit which finished on September 15.

‘The mission has changed the way we think of where life may have developed beyond our Earth,’ said Andrew Coates, head of the Planetary Science Group at Mullard Space Science Laboratory at University College London.

‘As well as Mars, outer planet moons like Enceladus, Europa and even Titan are now top contenders for life elsewhere,’ he added. ‘We’ve completely rewritten the textbooks about Saturn.’

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