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   Science  Environment

Saturn's weird hexagon changes colour

      25 October 2016
      From the section Science  Environment

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   Saturn hexagon Image copyright NASA

   The mysterious hexagon at Saturn's northern pole has changed colour
   from blue to gold, scientists have said.

   The hexagon is essentially a rotating cloud pattern; its shape may
   originate as the result of large differences in the speeds of Saturn's
   winds.

   The observation was made by Nasa's Cassini spacecraft, which has been
   exploring the sixth planet since 2004.

   The change in colour is thought to be the result of seasonal changes on
   the planet.

   In particular, the amount of sunlight falling on the poles affects the
   production of suspended particles - aerosols - in the atmosphere.

   Scientists think the shift from a bluish colour to a golden one may be
   due to more aerosols being produced through reactions involving
   sunlight and the atmosphere.

   This could be happening as the planet's north pole reaches its summer
   solstice in May 2017.

   Cassini was despatched to Saturn in 1997, to better understand the
   processes operating on Saturn and perhaps other giant planets.

   Using computer simulations, scientists have shown that small
   perturbations in winds flowing around the north pole can form a hexagon
   shape rotating at speeds close to those of the real one.

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