Jupiter’s Great Red Spot may not be as old as we expected

Jupiter’s iconic Great Red Spot, persisting for at least 190 years, is likely different from the spot observed by Giovanni Domenico Cassini in 1665, according to a new study led by the University of the Basque Country. 

Largest vortex in the solar system

The current Great Red Spot likely emerged due to instability in Jupiter’s intense atmospheric winds, forming a long-lasting atmospheric cell. This vortex, the largest in the solar system, has had its age and formation mechanisms debated for years. 

The new study utilized historical observations and numerical models to explain its longevity and nature.

Disappearance of the Permanent Spot 

“From the measurements of sizes and movements, we deduced that it is highly unlikely that the current Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” said lead author Agustín Sánchez-Lavega, a planetary scientist at the University of the Basque Country. 

“The ‘Permanent Spot’ probably disappeared sometime between the mid-18th and 19th centuries, in which case we can now say that the longevity of the Red Spot exceeds 190 years.”

Studying the Great Red Spot

The Great Red Spot’s large size, which makes it visible with small telescopes, has intrigued scientists for centuries. 

Discovered by Cassini in 1665, the dark oval he termed the “Permanent Spot” was observed until 1713, after which it was lost. A similar structure was not seen again until 1831. Scientists have debated whether today’s Great Red Spot is the same as Cassini’s spot.

Historical data

The researchers analyzed historical data from the mid-1600s, examining the spot’s size, structure, and location over time. 

“It has been very motivating and inspiring to turn to the notes and drawings of Jupiter and its Permanent Spot made by the great astronomer Jean Dominique Cassini,” Sánchez-Lavega said. “Others before us had explored these observations, and now we have quantified the results.”

Shrinking size

The study found that the Great Red Spot, which measured 39,000 kilometers in 1879, has been shrinking to its current size of about 14,000 kilometers. 

Space missions since the 1970s, particularly NASA’s Juno, have provided insights, revealing the spot’s shallow and thin nature, crucial for understanding its formation.

Formation of the Great Red Spot 

The scientists conducted numerical simulations to explore the formation of this massive vortex. They considered three scenarios: a gigantic superstorm, the merging of smaller vortices, or instability in the winds producing an elongated atmospheric cell. 

The cell-producing wind instability seemed the most likely, leading to the “proto-Great Red Spot,” which then shrank over time.

Future research aims to simulate the Great Red Spot’s shrinking and explore the physical mechanisms behind its stability. Scientists hope to predict whether it will disintegrate and disappear or stabilize at a smaller size.

More about the Great Red Spot 

The Great Red Spot is a massive, persistent storm in Jupiter’s atmosphere. It is an anticyclonic storm, meaning it rotates in a counterclockwise direction in the planet’s southern hemisphere. The storm is so large that it can fit two to three Earths within its boundaries. 

The spot is characterized by its reddish color, which is thought to be due to the complex organic molecules, red phosphorus, or other chemical compounds that are present in the atmosphere. 

Facts about Jupiter

Jupiter, the largest planet in our solar system, is a gas giant primarily composed of hydrogen and helium. 

Dozens of moons

Jupiter has a strong magnetic field and at least 79 moons, with the four largest being Ganymede, Callisto, Io, and Europa. 

These moons are of great interest to scientists due to their unique characteristics, such as the possibility of subsurface oceans on Europa. 

Solar system dynamics 

Jupiter’s immense size and gravitational influence play a crucial role in the dynamics of our solar system, affecting the orbits of other planets and capturing numerous comets and asteroids. 

Rapid rotation 

Its rapid rotation, taking just under 10 hours to complete a full spin, contributes to its oblate shape, meaning it is slightly flattened at the poles and bulging at the equator. 

Observations

Observations and missions like Galileo and Juno have provided significant insights into Jupiter’s composition, atmosphere, magnetosphere, and its diverse system of moons, enhancing our understanding of this giant planet and its place in the cosmos.

The study is published in the journal Geophysical Research Letters.

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