Amazing stuff!
"Over the years, passing spacecraft have observed mystifying weather patterns at the poles of Jupiter and Saturn. The two planets host very different types of polar vortices, which are huge atmospheric whirlpools that rotate over a planet’s polar region. On Saturn, a single massive polar vortex appears to cap the north pole in a curiously hexagonal shape, while on Jupiter, a central polar vortex is surrounded by eight smaller vortices, like a pan of swirling cinnamon rolls.
Given that both planets are similar in many ways — they are roughly the same size and made from the same gaseous elements — the stark difference in their polar weather patterns has been a longstanding mystery.
Now, MIT scientists have identified a possible explanation for how the two different systems may have evolved. Their findings could help scientists understand not only the planets’ surface weather patterns, but also what might lie beneath the clouds, deep within their interiors. ...
After comparing simulations, the team found that vortex patterns, and whether a planet develops one or multiple polar vortices, comes down to one main property: the “softness” of a vortex’s base, which is related to the interior composition.
The scientists liken an individual vortex to a whirling cylinder spinning through a planet’s many atmospheric layers. When the base of this swirling cylinder is made of softer, lighter materials, any vortex that evolves can only grow so large. The final pattern can then allow for multiple smaller vortices, similar to those on Jupiter. In contrast, if a vortex’s base is made of harder, denser stuff, it can grow much larger and subsequently engulf other vortices to form one single, massive vortex, akin to the monster cyclone on Saturn. ..."
From the significance and abstract:
"Significance
One intriguing difference between the two largest planets in the solar system is their polar vortex structures: Jupiter hosts multiple vortices at its poles, while Saturn exhibits a single polar vortex.
By systematically surveying the parameter space of a 2D quasi-geostrophic system, we demonstrate that 4 different polar vortex patterns may arise, depending on two key nondimensional numbers and the initial conditions. Analytical criteria predicting the 4 possible patterns are provided. Utilizing the observed vortex patterns, we further obtain constraints on Saturn’s vortex depth and stratification.
Abstract
The distinct polar vortex dynamics observed on Jupiter and Saturn may provide insights into their interiors. In this study, we examine how the number and structure of polar vortices vary with forcing strength, dissipation rate, and interior stratification using a 1.5-layer quasi-geostrophic model. This simplified setup enables a broad exploration of the parameter space, revealing that vortex characteristics are determined by the sequence in which three key length scales—the deformation radius , the zonostrophic scale , and the dissipative scale —are encountered as energy cascades from small to large scales.
Four distinct vortex patterns are identified, including a vortex crystal resembling Jupiter’s polar vortices and a single-vortex state akin to that of Saturn. The conditions under which these patterns emerge provide constraints on the stratification of Jupiter and Saturn."
Polar vortex dynamics on gas giants: Insights from 2D energy cascades (no public access)
Jupiter
Saturn
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