For decades, scientists have observed mysterious "hotspot" on the poles of Saturn that were later revealed as vast cyclones, each as wide as the planet Earth.
Now, simulations based on observations made by NASA's Cassini spacecraft suggest that thunderstorms in the giant gas planet's atmosphere could be driving these vast polar cyclones.
For the new study published in Nature Geoscience on June 15, atmospheric scientists from MIT used a planetary model of Saturn and simulated the impact of multiple thunderstorms that form across the planet.
The researchers observed that each of these small thunderstorms pulls air towards the planet's poles, a mechanism known as beta drift, and together, these small individual thunderstorms can gather enough atmospheric energy that could generate much larger cyclones at the poles.
"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," said study researcher Morgan O'Neill, from the Department of Earth, Atmospheric and Planetary Sciences (EAPS) of MIT.
The researchers likewise found that a cyclone develops depending on the planet's size relative to the size of the average thunderstorm on it, and how much of the atmospheric energy is induced by storm.
Based on these two parameters, the team predicted that Neptune, which is also characterized by similar polar hotspots, could also generate transient polar cyclones while Jupiter, the solar system's largest planet, should have none.
"We use simulations with a shallow-water model to show that storm generation, driven by moist convection, can create a strong polar cyclone throughout the depth of a planet's troposphere," the researchers wrote. "We find that the type of shallow polar flow that occurs on a giant planet can be described by the size ratio of small eddies to the planetary radius and the energy density of its atmosphere due to latent heating from moist convection."
The findings of the research could provide scientists with a better understanding on large-scale atmospheric phenomena occurring on exoplanets light-years away.
O'Neill said that the model used by his team could eventually be helpful in gauging the atmospheric conditions on planets beyond the solar system. If scientists find a cyclone-like hotspot on an exoplanet, for instance, they will be capable of estimating storm activity and the general atmospheric conditions of the planet.
