NASA’s Cassini spacecraft sent scientists close-up images of the “hotspots” at Saturn’s poles in 2008, revealing that hey are in fact massive cyclones, roughly the size of the Earth. The images both intrigued and puzzled experts as they could not figure out what the storms were caused by.
Unlike Earth cyclones, which are caused by heat mixing with moisture from the oceans, scientists now have a reason to believe that Saturn cyclones are caused by small thunderstorms which in time grow into massive cyclones that last for years.
A recent study, published earlier this week, on Monday (June 15, 2015), in the journal Nature Geoscience, informs that researchers at Massachusetts Institute of Technology (MIT) developed a model of Saturn’s atmosphere which shows how small, short-lived thunderstorms across the planet’s surface build up angular momentum in the atmosphere over time. These small, isolated thunderstorms eventually generate massive, long-lived cyclones due to the atmospheric energy that they accumulate.
Morgan O’Neill, lead author, former MIT PhD student and current postdoc at the Weizmann Institute of Science in Israel, gave a statement informing that the scientific community never considered the possibility of a cyclone at the pole until recently, when Cassini provided them with a rich new batch of observations.
He went on to explain the problem that scientists faced: “There’s no surface [on Saturn] at all — it just gets 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?”
He and his team found their answers by developing a model of Saturn’s atmosphere and using it to simulate several small, short-lived thunderstorms across the planet’s surface. They noticed that the thunderstorms had a tendency of drifting towards the planet’s poles due to Saturn’s rotation. The phenomenon is called “beta drift”.
These thunderstorms are able to generate so much atmospheric energy at the poles, that they eventually create a massive, long-klived cyclone.
Hundreds of storms were simulated using the model. They each ran for a hundred days and the tests showed that several of the thunderstorms reached beta drift and eventually led to the formation of cyclones.
Morgan O’Neill shared that each of the beta drifting thunderstorms soon sputter out and die. This mechanism allows for small, fast, abundant, thunderstorms that aren’t very strong to accumulate a great deal of angular momentum right on the pole, over a long period of time. The result is a permanent, “wildly strong” cyclone.
He researchers also inform that there are two (2) factors that determine whether or not a cyclone develops at the poles. The first one is the size of the planet relative to the size of an average storm on that planet, and the second one is how much storm-induced energy is in its atmosphere.
They used these parameters to make predictions about other planets as well. They said that Neptune most likely has polar cyclones that come and go, while giant Jupiter is not likely to have any at all since it’s too large for any of its storms to match the required proportion. However the questioned is not 100 percent answered as scientists have not been able to get a good look at Jupiter’s poles yet.
The lead author is hopeful that the model will some day be used to get a sense of the atmospheric conditions on planets that are outside our solar system.
Image Source: cnet.com