For years, spacecraft images have shown that the poles of Jupiter and Saturn are anything but calm. Each planet hosts giant atmospheric whirlpools called polar vortices—but the patterns could not be more different.
Saturn’s north pole is capped by a single, massive vortex with a striking hexagonal shape. Jupiter, by contrast, has a central polar vortex surrounded by eight smaller ones, arranged like a ring of spinning storms.
This contrast has long puzzled scientists. Jupiter and Saturn are similar in size and composition, made mostly of hydrogen and helium.
So why do their polar weather systems look so different?
A new study by scientists at MIT offers a promising explanation. The research, published in the Proceedings of the National Academy of Sciences, suggests that the answer may lie deep below the clouds—inside the planets themselves.
The team used computer simulations to explore how organized vortex patterns can form on gas giants.
They started with random atmospheric motion, similar to turbulent weather, and tested how it evolved under different planetary conditions. In some simulations, the chaos settled into a single, planet-spanning vortex, like Saturn’s. In others, it organized into multiple large vortices, similar to Jupiter’s polar storms.
After comparing many scenarios, the researchers found that one factor mattered more than any other: how “soft” or “hard” the base of a vortex is. This base reflects the properties of the planet’s interior layers beneath the atmosphere.
The scientists liken a polar vortex to a spinning cylinder that extends downward through many layers of gas. If the material at the bottom of this cylinder is soft and light, the vortex cannot grow very large. As a result, several smaller vortices can coexist at the pole, as seen on Jupiter. But if the base is harder and denser, a vortex can grow bigger and stronger, eventually absorbing neighboring vortices and forming a single dominant system, like Saturn’s polar cyclone.
This idea connects surface weather to interior structure in a new way. “The fluid patterns we see at the surface may actually tell us something about what’s going on deep inside these planets,” the researchers explain. In this view, Saturn may have a denser or more rigid interior layer than Jupiter.
The work was inspired by observations from NASA’s Juno mission at Jupiter and the Cassini mission at Saturn. Juno revealed that Jupiter’s polar vortices are enormous, each spanning about 3,000 miles. Cassini showed Saturn’s hexagonal vortex stretching roughly 18,000 miles across.
To study these systems efficiently, the team used a two-dimensional model of fluid motion. Although real vortices are three-dimensional, the rapid rotation of gas giants makes their motion fairly uniform along the planet’s spin axis. This allowed the researchers to simplify the problem while still capturing the essential physics.
If this mechanism is correct, it suggests that Saturn’s interior may contain heavier elements or materials that create stronger layering than Jupiter’s. Understanding these differences could help scientists learn how gas giants formed and evolved—and how much their hidden interiors shape the spectacular weather we see from space.
Source: KSR.
