Saturn Thunderstorms Cause Massive Cyclones on the Planet's Poles that Last Years

Scientists may now know what causes the "hotspots" on Saturn's poles. NASA's Cassini spacecraft has revealed that these hotspots are actually immense cyclones, each as wide as the Earth itself, that have been churning for years.

Cyclones on Earth are fueled by the heat and moisture of the oceans. However, bodies of water like this don't exist on Saturn. So what's causing these massive storms? Researchers may have found out.

Scientists developed a simple model of Saturn's atmosphere, and then simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they saw that each thunderstorm essentially pulled air toward the poles. Together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.

The researchers found that whether or not a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere.

"Before it was observed, we never considered the possibility of a cyclone on a pole," said Morgan O'Neill, the lead author of the new study, in a news release. "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."

The true reason why Saturn has cyclones is something called "beta drift." This phenomenon is when a planet's spin causes small thunderstorms to drift toward the poles, which then accumulate to cause cyclones.

"Each of these storms is beta-drifting a little bit before they sputter out and die," said O'Neill. "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 findings are published in the journal Nature Geoscience.

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