The hurricane like features at Saturn’s poles and what drives these storms and makes them persist for so long has been a mystery for decades.
The giant vast polar cyclones are likely to be driven by the thunderstorms in Saturn’s atmosphere. This research could help astronomers study atmospheric phenomena on exoplanets.
We know that on Earth thunderstorms or cyclones are caused by the flow of moisture over the oceans, but Saturn does not contain masses of water making it puzzling for scientists to understand the driving forces behind them.
Thus astronomers are looking for other clues behind this phenomenon.
In addition, Saturn’s north polar cyclone is surrounded by a mesmerizing hexagonal feature etched into the atmosphere. The hexagon is thought to be a product of turbulent eddies surrounding the central vortex, so scientists want to understand the driving forces behind these powerful atmospheric flows as an answer to the hexagon may also be found.
It is suggested by the journal Nature Geoscience that it could be many small thunderstorms in Staurn’s atmosphere that combine to form the cyclones.
“Before it was observed, we never considered the possibility of a cyclone on a pole,” said lead author Morgan O’Neill, former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) and now a postdoc at the Weizmann Institute of Science in Israel. “Only recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.”
O’Neill’s team was able to create a simple model of Saturn’s atmosphere that generated many small thunderstorms over time. Taking simple atmospheric dynamics into account, they found that the many storms pulled atmospheric gases toward the poles — a mechanism known as “beta drift” — building up angular momentum (or spin) in the planet’s atmosphere, culminating in vast cyclones at the poles.
With this connection made, the researchers realized that whether or not a polar cyclone forms depends on 2 parameters: “the energy within a planet’s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself,”. This means that the larger the average storm compared to the planet’s size, the more likely a long-lived polar cyclone will occur.
So, looking at the other gaseous planets in our solar system, the team plugged in the numbers for Jupiter and Neptune. They found that, from their model, Jupiter, the largest planet in the solar system, is unlikely to ever have storm-driven cyclones at its poles, whereas Neptune will have transient (or short-lived) polar cyclones.
Their model seems to, so far, hold true for Saturn and Neptune, but we haven’t had a good look at Jupiter’s poles, so we have little idea whether or not the gas giant possesses powerful polar cyclones. But it just so happens that we have a probe, NASA’s Juno mission, heading toward Jupiter orbit in 2016 — a mission that will study the Jovian magnetic field and swing over its poles.
“If what we know about Jupiter currently is correct, we predict that we won’t see these wildly strong cyclones,” added O’Neill. “We’ll find out next year if our predictions are true.”
This research has interesting implications for gauging atmospheric conditions on distant exoplanets. Should an exoplanet-hunting telescopes detect hot-spots near an exoplanet’s poles, say, astronomers may deduce that thunderstorm activity throughout the planet’s atmosphere is high, providing a tantalizing look into the atmospherics on alien worlds.
But the first test will come next year when Juno arrives at J