Has the mystery of Saturn’s 20,000 mile wide hexagonal storm been solved?

Apr 9, 2014 Source: dailymail.co.uk

The bizarre six-sided storm churning Saturn’s north pole has flummoxed astronomers ever since it was first spotted thirty years ago.

Now, astronomers believe they may have solved one of its biggest mysteries by working out how it operates - and discovering the rotation period of Saturn in the process.

The giant storm operates rather like the jet stream on Earth they say - explaining why it never appears to move.

The unusual structure with a hexagonal shape surrounding Saturn’s north pole was spotted on the planet for the first time thirty years ago.

The hexagon is a wavy jet stream of 200 mph winds and spans 20,000 miles (30,000 kilometers) across - more than twice the diameter of Earth.

Nothing similar with such a regular geometry had ever been seen on any planet in the Solar System.

The Planetary Sciences Group has now been able to study and measure the phenomenon and, establish its rotation period, and that of Saturn - the only planet in the Solar System whose rotation time remains unknown.

Researchers found seasonal variations do not affect the hexagon and its jet stream at all, so concluded both are part of an extensive wave, deeply rooted in Saturn’s atmosphere.

The UPV/EHU researchers suggest that the hexagon and its stream are the manifestation of a ’Rossby wave’ similar to those that form in the mid-latitudes of the earth.

On our planet the jet stream meanders from west to east and brings, associated with it, the system of areas of low pressure and anticyclones which we have been seeing regularly on weather maps.

On Saturn, a hydrogen gas planet, ten times the size of the Earth, cold in its upper clouds, without a solid surface, and with an atmosphere as deep as that of an ocean, ’the hexagonal wavy motion of the jet stream is expected to be propagated vertically and reveal to us aspects of the planet’s hidden atmosphere,’ said Agustín Sánchez-Lavega, Head of the Planetary Sciences research group.

’The movement of the hexagon could therefore be linked to the depths of Saturn, and the rotation period of this structure, which, as we have been able to ascertain, is 10 hours, 39 minutes and 23 seconds, could be that of the planet itself,’ he added.

Saturn is the only planet in the Solar System whose rotation period is not yet known.

Due to the tilt of approximately 27º of the planet Saturn, its polar atmosphere undergoes intense seasonable variations with long polar nights lasting over seven years, followed by a long period of 23 years of variable illumination.

In 1980 and 1981 NASA’s Voyager 1 and 2 space probes passed for the first time over the planet Saturn, located 1,500 million km from the Sun.

Among their numerous discoveries they observed a strange, hexagon-shaped structure in the planet’s uppermost clouds surrounding its north pole.

The hexagon remained virtually static, and images captured by the Voyager probes found that the clouds were moving rapidly inside the hexagon in an enclosed jet stream and were being dragged by winds travelling at over 400 km/h.

Thirty years later –the equivalent of one Saturn year, in other words, the time the planet takes to go all the way around the Sun– and over more than six consecutive years, researchers in the UPV/EHU’s Planetary Sciences Group, in collaboration with astronomers from various countries, were able to observe Saturn’s northern polar region in detail once again and confirmed that the hexagon continued in place.

After measuring the positions of the hexagon vertices with great precision, they determined that its movement remains extremely stable, and on the basis of the cloud movements, that the jet stream inside it remains unchanged.

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