According to a new model for simulating and analyzing planetary storm patterns, scientists can now present a theory showing how smaller storms over a longer period of time could accumulate angular momentum with a result looking like the north pole of Saturn.
The hexagonal shape of the constant polar cyclone of Saturn has puzzled both scientists and the general public ever since it was discovered in 2008, by the NASA spacecraft Cassini.
Morgan O’Neill, a postdoc at the Weizmann Institute of Science in Israel, and a former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences, explains the difficulties they faced when trying to figure out how the 20,000 miles (30,000 kilometers) wide cyclone has formed. “There’s no surface at all—it just get’s denser as you get deeper. If you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?”
What they found was a phenomenon called “beta drift”. This allows for small thunderstorms to move towards the poles of a planet, a movement caused by its spin. At the same time, storms spin in different directions depending on wether they are at the surface or in the upper atmosphere.
“The whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum. If you converge a bunch of that air at the base of a thunderstorm, you’re going to get a small cyclone,” O’Neill explains in the study which was published in the journal Nature Geoscience.
Her team developed an atmospheric model for Saturn. By performing hundreds of simulations for hundreds of days for each simulation, they could determine that several of the smaller storms would beta drift, and end up accumulating so much circulation in the atmosphere that it would create a large cyclone like this over the poles of the planet.