content long 17-October-2017 09:57:30

Winners Spain

16-18 years old: The hexagon at Saturn's north pole

 Authors: Raquel Juárez Martos, Miriam Martínez Pricopi, María López Gómez

They asked the mountain-climber George Leigh Mallory (1886-1924) what reason he had to risk his life climbing mountains. His answer remained for posterity. "I climb mountains because they are there".

The same happens with the hexagon of the north pole of Saturn. We study it because "it’s there". Its existence captivates us.

After the first images taken by the probe Voyager 2 in 1980 and by the telescope Hubble in 1991, the mission Cassini-Huygens has been sending us information about the polar north vortex delimited by closed currents of cloudy matter with hexagonal form for more than 10 yearsi.

"Climbing this mountain " it isn’t easy. Until now, we don’t know when it was generated nor when the hexagon will be eliminated, unique structure between the polar vortexes of the planets with known atmosphere. Its origin seems to be linked to the latitudinal variation of the speeds of rotation of the gaseous capsii (formed mainly by hydrogen and helium), to the force of Coriolis and to the gradients of pressure and temperatureiii (from the core towards the most external caps of the atmosphere we find differences of the order of 104K). Where there isn’t an agreement in the scientific community is in describing the hexagon as the consequence of stationary wavesiv.

The hexagon is observed at 78° north latitude and doesn’t move longitudinally along the atmosphere. His six sides act as a natural border, generating a superb laboratory where to learn on dynamics of fluids, so important in disciplines as the aeronautics or the atmospheric physics.

Cassini-Huygens has offered information about the radiation in infrared of Saturn, thanks to his systems VIMS and CIRSvi, and has shown, in the visible spectrum, the variation of color of the hexagon according to the station of the planet (going on from bluish tones to golden tonesvii). The central eye of the vortex presents an average diameter of 2.000km and winds that exceed 500km/hviii. The form of the eye and of the hexagon have remained stable, at least, throughout the whole Saturnian year (equivalent to 29,6 Earth years). Therefore, they are phenomena not related to the relative position of the planet with regard to the Sun. His stability contrasts with a few days of average life of the storms in our planet, possibly due to the minor relative action of the gravity of the core of Saturn on his atmosphere.

The polygonal patterns are known in unstable fluids submitted to currents of convection. They even appear in the center of certain hurricanes of our planet. But the dimensions of the hexagon of Saturn, with sides that exceed 13.500km, make it an unique challenge for the science. “The mountain” surprised us every time!

More questions that certainties. The images of the probe Cassini-Huygens are at the service of the science and the society in generalix. The hexagon is waiting for us.


Last Update: 19 May 2017

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