A team of scientists from MIT has put forward a theory that would explain the presence of enormous polar cyclones present on the gas giant Saturn. The cyclones, first discovered by the Cassini spacecraft in 2008, are so massive that they could swallow the Earth in their expanse. The research may even lead to better characterization of the atmosphere of distant exoplanets.
The element of the cyclones that has been baffling scientists since their discovery is how they can come to exist in an environment such as that prevailing on Saturn. On Earth, cyclones are generated by heat and moisture created by our planet's oceans. These are prerequisites that are obviously lacking on Saturn – a gas giant which is predominantly composed of hydrogen and helium.
A team of scientists from MIT believe that they may have found the answer. According to the team, numerous relatively small thunderstorms occurring in the atmosphere of the ringed giant could have the effect of diverting air towards the gas giant's polar regions, thanks to a phenomenon known as beta drift.
"Each of these storms is beta-drifting a little bit before they sputter out and die," states lead author of a paper on the findings Morgan O’Neill says. "This mechanism means that little thunderstorms – fast, abundant, but not very strong thunderstorms – over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone."
The polar cyclones currently present on Saturn are believed to whip up winds in excess of 300 mph (483 km/h), and have persevered on the gas giant for many years. To make the discovery, the researchers created an atmospheric model and undertook numerous computer simulations that ran for hundreds of days.
The tests showed that for a polar cyclone to be present, there must be sufficient energy in the atmosphere, or alternatively energy whipped up by minor storms in the context of the size of the relevant planet. The larger the planet, the more storms that must be present to trigger a cyclone. Jupiter for example is too massive for the small atmospheric storms to generate a cyclone, but they may exist on Neptune.
If the theory is correct, astronomers may in the future be capable of gauging storm intensity in the atmosphere of distant exoplanets by observing the size of polar cyclones.
A paper regarding the team's findings has been published in the journal Nature Geoscience.