The past ten years have been an exciting time for astronomers and Saturn. Massive cyclones were discovered near the ringed planet’s poles. What’s causing them? New research suggests small thunderstorms add up to create the huge cyclones.
In 2008, Cassini snapped amazing, close-up images of the cyclones. Check out one of them below.
‘Massive’ doesn’t even begin to describe these cyclones. Scientists estimate the cyclones are as wide as Earth, and each one packs winds approaching 300 mph. Imagine a F5 tornado the size of Earth.
When the Cassini probe gave scientists an up-close view of Saturn’s cyclones, they were blown away.
“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” said Andrew Ingersoll, a Cassini imaging team member. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”
How small thunderstorms help form an enormous cyclone?
Atmospheric scientists from MIT propose a new theory to Saturn’s cyclone formation. Small, brief thunderstorms. These thunderstorms, spread out across the planet, generate spin in Saturn’s atmosphere and ultimately lead to massive cyclones.
To test the theory, scientists created a model of Saturn’s atmosphere. Then they simulated the effect of multiple small thunderstorms forming across the planet. Eventually, enough energy from these small thunderstorms gathered at Saturn’s poles to create a much larger and longer-lasting cyclone.
But, not every thunderstorm helped create a cyclone. MIT scientists say cyclone formation depends on two parameters: the size of a planet relative to the average size of a thunderstorm, and how much atmospheric energy is generated by the thunderstorms.
“Before it was observed, we never considered the possibility of a cyclone on a pole,” says O’Neill. “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.”
How do the thunderstorms get to the poles?
“There’s no surface at all — it just gets denser as you get deeper,” O’Neill says. “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?”
O’Neill believes cyclone formation is possible thanks to a phenomenon called ‘beta drift.’ The planet’s spin nudges any thunderstorm towards the poles.
During model testing, the team noted multiple thunderstorms experiencing this ‘beta drift.’
“Each of these storms is beta-drifting a little bit before they sputter out and die,” 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.”
What’s next for Cassini?
Cassini’s previous discoveries are giving scientists plenty to work with, but what about now? Today, Cassini is set to make its closest approach to Saturn’s icy moon Dione. The spacecraft will come within 321 miles and will use its cameras and instruments to observe Dione.
One area of interest will be a region called “Eurotas Chasmata.” This area was first observed by NASA’s Voyager mission 35 years ago. Voyager spotted bright, wispy streaks across the surface. Scientists are hoping for a clearer look at these features when Cassini flies by Dione this afternoon.
Today won’t be the last time Cassini visits Dione. Another flyby is scheduled for August. It will be even closer; within 295 miles.