JupiterThe Great Red Spot is a giant vortex that has existed for at least 190 years. Recent studies suggest that it is different from any previously observed spot, and simulations explore how Jupiter’s winds may have shaped it. The Great Red Spot is shrinking, and future research will focus on its persistence and possible future disintegration.
Jupiter’s Great Red Spot stands out as one of the most recognizable features in the Solar System. This massive atmospheric structure, currently spanning about the diameter of Earth, is easily recognizable by its striking reddish color, which contrasts sharply with Jupiter’s pale cloud tops. Even small telescopes can capture its distinctive appearance. The Great Red Spot is a giant anticyclonic vortex, with winds reaching speeds of up to 450 km/h (280 mph) along its outer edges. It holds the title of the largest and longest-lived vortex in the atmosphere of any planet in our Solar System. However, the exact age of the Great Red Spot is still debated, and the processes behind its formation remain a mystery.
Speculation about the origin of the GRS dates back to the first telescopic observations made by astronomer Giovanni Domenico. Cassiniwho in 1665 discovered a dark oval at the same latitude as GRS and named it the “Permanent Spot” (PS), which was observed by him and other astronomers until 1713.
It was then lost for 118 years and was not noticed again until 1831 and later by S. Schwabe, a clear, roughly elliptical structure located at the same latitude as the constellation Corvus Major; this can be considered the first observation of the present Corvus Major, and perhaps of a nascent Corvus Major. Since then, Corvus Major has been regularly observed by telescopes and by various space missions that have visited the planet up to the present day.
GRS Evolution Analysis
In the study, the authors first analyzed the evolution of its size over time, its structure, and the motions of both atmospheric formations, the former PS and the GRS; to do this, they used historical sources dating back to the mid-17th century, shortly after the invention of the telescope.
“From the measurements of the sizes and movements, we conclude that it is extremely unlikely that the current Red Spot is the PS Spot observed by G.D. Cassini. The PS Spot probably disappeared sometime between the mid-18th and 19th centuries, in which case we can say that the Red Spot’s lifetime now exceeds at least 190 years,” explained Agustín Sánchez Lavega, professor of physics at the UPV/EHU who led this research. The Red Spot, which in 1879 measured 39,000 km at its longest axis, has been shrinking to about 14,000 km today and at the same time becoming more rounded.
Recent results and simulation studies
Moreover, since the 1970s, several space missions have closely studied this atmospheric phenomenon. More recently, Sánchez-Lavega explained that “various instruments on board the Juno mission in orbit around Jupiter have shown that the Earth’s atmosphere is shallow and thin compared to its horizontal dimensions, with a vertical length of about 500 kilometers.”
To understand how this enormous vortex was formed, the UPV/EHU and UPC teams performed numerical simulations on Spanish supercomputers, such as MareNostrum IV of the BSC, part of the Spanish Supercomputing Network (RES), using two types of complementary models of the behavior of thin vortices in Jupiter’s atmosphere. The giant planet is dominated by strong wind currents that flow along latitudes alternating in direction with latitude. To the north of the GRS, the wind blows in a westerly direction at speeds of 180 km/h, while to the south it blows in the opposite direction, in an easterly direction, at speeds of 150 km/h. This generates enormous north-south shear in the wind speed, a fundamental element that enables the vortex to grow within it.
In the research, a range of mechanisms were explored to explain the origin of the GRS, including the eruption of a giant superstorm, similar to those rarely observed on the twin planet. SaturnOr the merger of multiple smaller vortices caused by wind shear. The results suggest that although an anticyclone formed in both cases, it differed in shape and dynamic properties from those of the current GRS. “We also believe that if one of these unusual phenomena occurred, astronomers should have observed it or its consequences in the atmosphere and reported it at that time,” Sánchez-La Vega said.
Digital simulation and future research
In a third set of numerical experiments, the research team explored the formation of this red spot from a known wind instability that is thought to be capable of producing an oblong cell that envelops and traps it. This cell would be a nascent red spot, whose subsequent contraction would give rise to the rapidly rotating compact red spot observed in the late 19th century. Large oblong cells have already been observed in the formation of other large vortices on Jupiter.
“In our simulations, supercomputers enabled us to discover that the long cells are stable when they rotate around the GRS at the speed of Jupiter’s winds, as expected when they form due to this instability,” said Enrique Garcia Melendo, a researcher in the Department of Physics at the University of Pittsburgh. Using two different types of numerical models, one at the UPV/EHU and the other at the University of Pittsburgh, the researchers concluded that if the initial GRS rotation speed is lower than the speed of the surrounding wind, the initial GRS will break up, making it impossible to form a stable vortex. If it is too high, the properties of the initial GRS differ from those of the current GRS.
Future research will aim to try to reproduce the shrinkage of the solar atmosphere over time in order to discover the physical mechanisms that underlie its long-term sustainability. At the same time, it will try to predict whether the solar atmosphere will disintegrate and disappear when it reaches a size limit, as Cassini’s solar atmosphere did, or whether it will stabilize at a size limit that may persist for many more years.
Reference: “The Origin of Jupiter’s Great Red Spot” by Agustin Sánchez La Vega, Enrique García Melendo, John Legarreta, Arnau Miró, Manel Soria, and Kevin Arinz Velázquez, June 16, 2024, Geophysical Research Letters.
Digital Document Number: 10.1029/2024GL108993
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