The gas giants are still far from having revealed all their secrets, and these cyclones are proof.
The poles of our Earth are immediately identifiable thanks to the polar caps that permanently cover them, at least until global warming has reduced them to nothing. But in the case of Jupiter, the landscape is much more dynamic and also very mysterious. Recently, in a study discovered by © NASA/JPL-Caltech/SwRI/MSSS, a new team of astronomers looked back at a geometric pattern so far they have not been able to explain satisfactorily.
It all starts with Jupiter’s famous cyclones, those huge whirlpools that can linger on the gas giant’s surface for years. Since they were documented by the Juno spacecraft in 2016, they have become a favorite sight for astronomers; but if they are visually sumptuous, these vortices are also a great source of frustration for specialists.
Particularly mysterious swirls
And for good reason: despite long years of effort, astrophysicists are still far from understanding all the dynamics that fuel these behind-the-scenes phenomena. But this investigation advances little by little; In January 2022, a research team confirmed that standard fluid mechanics, which already makes it possible to describe similar phenomena in terrestrial oceans, was able to explain part of this turbulence.
But it was only a beginning. Because at the poles, these vortices adopt a curious behavior. In fact, there are vortices that form a surprisingly geometric patternwith a huge central cyclone surrounded by several smaller vortices: eight at the North Pole and six at the South Pole.
This strange object has the peculiarity of being extremely stable over time; its overall structure hasn’t moved an inch since it was first observed in 2017. And that’s very surprising, as the planet’s constant rotation tends to push this turbulence poleward. Therefore, fluid mechanics suggests that they should either merge, as is the case with Saturn, either accumulate in large quantities, which is not the case here.
To explain this peculiarity, the researchers proposed a first response element in 2020, a few years before the dynamics of individual vortices were studied in detail (see theArticle of Physics Today).
Several studies still incompatible
Based on the size of these objects (2,000 to 3,500 km in diameter anyway!) and their arrangement, they made modeling which allowed them to conclude that each of these vortices could each have its own personal anticyclone. In this context, this term refers to a layer of air that would rotate in the opposite direction, thus stabilizing the storm in a well-defined pocket.
A more than promising track, but the explanations were not neither sufficient nor completely satisfactory to the team of Andrew Ingersoll, professor of planetary sciences at the California Institute of Technology. With his colleagues, therefore, they set out to explore this pathway in more detail.
Therefore, they dissected the images of the North Pole of Jupiter reported by the spectrometer of the Juno probe. The objective: to follow the trajectory of the winds using a set of very advanced mathematical tools. And the good news is that his work was joined in part to that of his predecessors: they managed to prove the existence of a large anticyclonic ring around the main vortex.
On the other hand, unlike previous works, a very important phenomenon is still missing in this context. “We do not find the expected convection signature, even at the smallest spatial scale.”, regret the researchers. This is a major sticking point that makes the conclusions of the two studies incompatible, at least for now.
In fact, they consider that these works are not fundamentally irreconcilable; on the other hand, it will be necessary to use the great means to reach a clear conclusion. To begin with, they propose to carry out a new almost identical study, but this time focused on the South Pole.
“A parallel study of Jupiter’s South Pole vortices, focusing on spin intensity and stability, would be a step in the right direction.”, they affirm in their research work.
New sightings to come
In the meantime, they will continue to analyze the data produced by Juno in hopes of finding new clues. And if they persist on this point, it is because the implications of this work are quite profound.
In fact, even if Jupiter is an exception in our solar system, gas giants of this type are legion in the universe. Due to their enormous mass, these celestial bodies are also important gravitational sinks that have considerable influence on their surroundings. For example, the migrations of the gas giants are thought to have triggered a major gravitational upheaval that played a key role in shaping the structure of the solar system as we know it today.
These immense deposits of gas and dust therefore occupy an important place in the global dynamics of the universe. But to accurately understand all the phenomena in which they participate, it is necessary to begin by mastering the ins and outs of their intrinsic workings, and planetary scientists are still a long way from that.
Since we can’t yet build a device capable of withstanding the overwhelming stresses of their atmospheres, the only way to study gas giants is to do it from the outside. That is why the study of phenomena such as these vortices is fundamental: they represent a window to the internal dynamics of the planet.
The future will tell us, therefore, if the study of Jupiter from new angles will allow us to answer these questions. Otherwise, it may be necessary to search for new physical principles never before documented to explain the incredible regularity of these polar vortices.
The text of the study is available. here.