By Francesca Serra

Jupiter, the largest planet in the Solar System, has fascinated astronomers and scientists for centuries. At the heart of Jupiter's features lies its most iconic hallmark: the Great Red Spot (GRS). This persistent anticyclone storm that has raged across Jupiter's equatorial atmosphere for centuries has remained a puzzle for researchers. How could it have lasted for so long? Recent strides in observational data and simulations are shedding new light on the dynamics of this gigantic vortex.

The Perfect Storm

The Great Red Spot was first spotted by Giovanni Cassini in 1655 and, even if we cannot be sure to observe today the same feature he saw, its enigma has persisted throughout the years, spurring curiosity about its origins and behavior. The detailed image captured by Voyager 1 in 1979 further revived interest in the GRS, and subsequent missions, including NASA's Juno, have all contributed valuable data on Jupiter's cloud belts and magnetosphere.

Pankaj Jagad, a research scientist in the Physical Science and Engineering Division at KAUST, uses those data to model the fluid dynamics conditions that gave rise to Jupiter's Great Red Spot. Jagad specializes in investigating flows dominated by vorticity on surfaces and developing numerical methods for fluid flows using structure-preserving discrete exterior calculus. His contribution to the studies on the GRS consists in simulating the behavior of the Great Red Spot using a spherical model, departing from previous approximations that relied on planar representations. By leveraging observational data as the starting point, Jagad's simulations offer unprecedented insights into Jupiter's atmosphere.

A turbulent behavior

A primary objective of Pankaj's research is to investigate the reasons behind the longevity of the GRS and ultimately enhance our understanding of the atmospheres of the other giant planets in the Solar System, such as Saturn, Neptune, and Uranus, which - just like Jupiter - have no orographic features to dissipate the energy of their atmosphere.

Although persistent, the GRS keeps on changing shape and size. In the last decades, thanks to the spacecraft sent across the Solar System, astronomers were able to observe that the GRS's shape became more circular from the original cigar-like shape and shrank to the size of planet Earth. These changes also affected the wind speed at the rim and at the center of the vortex, and possibly also its depth, even if, until now, there are no tools to measure the dynamics of the deeper atmosphere.

Is the GRS vanishing?

We don't know.

Simulating the Great Red Spot could help predict the fate of this giant vortex and understand what will come next, but it is a challenging task. Numerical dissipation, for instance, can result in the unphysical disappearance of the storm. Moreover, Jupiter's spherical shape adds complexity to the simulation process due to the latitude-dependent nature of Coriolis, a critical parameter in fluid dynamics. 

To tackle these challenges, Jagad employs a numerical method known as discrete exterior calculus, which minimizes numerical dissipation and remains independent of specific coordinates. This approach enables more accurate handling of Jupiter's sphericity, allowing for a more comprehensive simulation of the planet's atmosphere.

Jagad's model will also be useful for a holistic simulation of other vortices on Jupiter, such as the White Ovals, recurrent anticyclonic storms also called the Great White Spots (GWS), which appear near Jupiter's poles and can last for several months before fading away.

A glimpse of the primordial solar system

The study of Jupiter's Great Red Spot has come a long way since its discovery centuries ago. Through the collective efforts of astronomers, scientists, and researchers like Pankaj Jagad, we are gradually unraveling the intricate interplay of gravity, friction, and fluid dynamics that sustain this never-ending storm.

But unraveling Jupiter's atmospheric dynamics is not the only scope of this research. As we delve deeper into the secrets of Jupiter and its unaltered gas composition, we extend our glance to the primordial nebula of gasses that generated our solar system.

In the coming years, new missions and innovative modeling techniques will yield further insights into the Great Red Spot, unlocking its mysteries and unveiling the story of Jupiter's turbulent atmosphere and, ultimately, the formation of our home in the universe.