The iconic Jupiter’s Great Red Spot is a huge storm that has been swirling in the atmosphere of the largest planet in the Solar System for years.
But astronomers have debated how long the vortex has actually existed, as well as when and how it formed. Some experts believed it was centuries old and was first observed by the Italian astronomer Giovanni Domenico Cassini in the 17th century, while others thought the storm was more recent.
Now, new research suggests that the Great Red Spot formed about 190 years ago, meaning Cassini observed something else on Jupiter in 1665. And despite being younger than previously believed, the storm remains both the larger than the longest-lasting known vortex in our Solar System, according to researchers.
A study detailing the findings was published June 16 in Geophysical Research Letters magazine.
An eye in the storm
Jupiter’s striking appearance features stripes and patches made up of bands of clouds circling the planet and cyclonic storms. Its colors come from the composition of different atmospheric layers, which are individually formed by ammonia, water ice, sulfur and phosphorus gases, according to NASA (United States space agency). Fast jet streams carve and stretch clouds into long bands.
Cyclonic storms on Jupiter can last for years because the gas planet lacks a solid surface, which could slow down the storms.
The Great Red Spot is a huge vortex within Jupiter’s atmosphere that is about 16,350 kilometers wide, similar to the diameter of Earth, according to NASA. The storm rises to more than 200 miles (322 kilometers) high.
Howling winds pass at 450 kilometers per hour along the edges of the storm. And its characteristic red color comes from atmospheric chemical reactions.
The iconic feature is visible even through small telescopes.
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And it looked similar to a dark oval at the same latitude that Cassini first spotted when looking through his telescope in the mid-1600s. He referred to the feature he spied as the “Permanent Spot,” and Cassini and other astronomers observed it until 1713. , when they lost sight of the storm.
Then, in 1831, astronomers spotted a large oval storm at the same latitude on Jupiter, which persisted and is still observed today. But astronomers had long questioned whether it was possible that the storms were the same phenomenon or two different vortices that manifested in the same place more than a century apart.
A team of researchers aiming to solve the enigma has gathered a large amount of data, analyzing historical drawings and images that depict the structure, location and size of the stain over time. The data was used to create numerical models that recreate the possible longevity of the storm.
“Based on size and motion measurements, we deduce that it is highly unlikely that the current Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” said study lead author Agustín Sánchez-Lavega, professor of applied physics at the University of the Basque Country in Bilbao, Spain, in a statement. “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 Great Red Spot exceeds 190 years.”
The Permanent Stain persisted for about 81 years, and none of the drawings analyzed by the team mentioned any specific color for the storm, according to the study authors.
“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 (Cassini), and to his articles from the second half of the 17th century describing the phenomenon,” said Sánchez-Lavega. “Others before us have explored these observations, and we have now quantified the results.”
Shrinking in size
While examining historical data, researchers also explored how the storm originated, running supercomputer simulations using models of how vortices behave in Jupiter’s atmosphere.
The team ran simulations to see whether the Great Red Spot formed from a gigantic superstorm, the merger of smaller vortices produced by Jupiter’s intense, alternating winds, or an instability in the winds that could produce an atmospheric storm cell. A thunderstorm cell is a mass of air sculpted by updrafts and downdrafts of wind that moves as a single entity.
Although the first two scenarios resulted in cyclones, they differed in shape and other characteristics observed in the Great Red Spot.
“We also think that if one of these unusual phenomena had occurred, it or its consequences in the atmosphere should have been observed and reported by astronomers at the time,” said Sánchez-Lavega.
But researchers believe that the persistent atmospheric storm cell, resulting from intense wind instability, produced the Great Red Spot.
The storm measured about 39,000 kilometers at its longest point, according to data from 1879, but has been shrinking and becoming rounder over time, and now measures about 14,000 kilometers.
Previous research, published in March 2018, showed that the Great Red Spot is getting taller as it shrinks in overall size. The 2018 study also used archival data to study how the storm changed over time.
Data from modern space missions, such as NASA’s Juno spacecraft, have provided astronomers with unprecedented views of the storm’s shape.
“Several instruments aboard the Juno mission in orbit around Jupiter have shown that the (Great Red Spot) is shallow and thin compared to its horizontal dimension, as vertically it is about 500 km long,” said Sánchez-Lavega.
Moving forward, researchers will attempt to recreate the storm’s shrinking rate over time to understand the processes that keep the storm stable, as well as determine whether it will persist for years or disappear once it reaches a certain size — which may have been the case. fate of Cassini’s Permanent Spot.
“I love articles like this that delve into pre-photographic observations,” said Michael Wong, a research scientist at the University of California, Berkeley, and co-author of the 2018 paper, after reading Sánchez-Lavega’s research. “(Our) paper used tracing data going back to 1880, but Sánchez-Lavega’s new paper went further and used hand-drawing data. The supplementary materials for this article are also great.”
Wong was not involved in the new study.
“We have a lot to learn about these planets by making continuous, long-term observations of their climate and weather.”
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