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Jupiter’s iconic Great Red Spot is a massive storm that has been swirling in the atmosphere of the largest planet in the solar system for years.
But astronomers have debated how old the vortex really is, as well as when and how it formed. Some experts believed the storm was centuries old and was first observed by 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 different on Jupiter in 1665. And despite being younger than previously thought, the storm remains both the largest and longest-lived vortex known in our entire world. solar system, according to researchers.
A study detailing the findings appeared June 16 in the journal Geophysical Research Letters.
A look at the storm
Jupiter’s striking appearance consists of streaks and spots composed of planet-circling cloud bands and cyclonic storms. The colors result from the composition of different atmospheric layers, which according to NASA are individually made of ammonia, water ice, sulfur and phosphorus gases. Fast jet streams shape and stretch the clouds into long bands.
Cyclonic storms on Jupiter can last for years because the gas planet has no solid surface, which can slow down storms.
The Great Red Spot is a huge vortex in Jupiter’s atmosphere that is about 10,000 miles (16,350 kilometers) wide, which is comparable to the diameter of Earth, according to NASA. The storm towers at an altitude of more than 200 miles (322 kilometers) high.
Screaming winds rush past the storm’s boundaries at 280 miles per hour. And the distinctive red hue comes from chemical reactions in the atmosphere.
The iconic feature is visible even through small telescopes.
And it sounded like a dark oval at the same latitude that Cassini first saw when he looked through his telescope in the mid-17th century. He named the object he spotted the “Permanent Spot,” and Cassini and other astronomers observed it until 1713, when they lost sight of the storm.
Then in 1831, at the same latitude on Jupiter, astronomers discovered a large, oval-shaped storm, which continues and is still observed today. But astronomers have long wondered whether it was possible that the storms were the same phenomenon, or two different vortices manifesting in the same spot more than a century apart.
A team of researchers looking to solve the enigma collected a wealth of data and analyzed historical drawings and images that depict the structure, location and size of the site over time. The data was used to create numerical models that simulate the storm’s potential lifetime.
“From the size and motion measurements, we concluded that it is highly unlikely that today’s Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” said lead study 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 lifespan of the Red Spot is more than 190 years.”
The Permanent Spot persisted for about 81 years, and according to the study authors, none of the drawings the team analyzed mentioned a specific color for the storm.
“It was very motivating and inspiring to look at the notes and drawings of Jupiter and its permanent position made by the great astronomer (Cassini), and at his articles from the second half of the 17th century describing the phenomenon,” says Sánchez-Lavega. said. “Others before us had investigated these observations, and now we have quantified the results.”
Shrinking in size
While reviewing the historical data, the researchers also investigated how the storm formed by running simulations on supercomputers using models of how vortices behave in Jupiter’s atmosphere.
The team ran simulations to see whether the Great Red Spot formed from a giant superstorm, the merger of smaller vortices produced by Jupiter’s intense and alternating winds, or from an instability in the wind that an atmospheric storm cell could create. A storm cell is an air mass formed by upward and downward wind currents that moves as one unit.
Although the first two scenarios resulted in cyclones, they differed in shape and other features seen in the Great Red Spot.
“We also think that if any of these unusual phenomena had occurred, it or its consequences in the atmosphere should have been observed and reported by the astronomers at the time,” Sánchez-Lavega said.
But researchers believe the persistent atmospheric storm cell, which resulted from intense wind instability, caused the Great Red Spot.
According to records from 1879, the storm was about 24,200 miles (about 39,000 kilometers) long at its longest point, but over time it has shrunk and become more rounded, and is now about 8,700 miles (14,000 kilometers).
Previous research, published in March 2018, has shown that the Great Red Spot grows larger as it decreases in size. The 2018 study also used archival data to study how the storm has changed over time.
Data from modern space missions, such as NASA’s Juno spacecraft, have given astronomers unprecedented insight into the storm’s shape.
“Several instruments on board the Juno mission orbiting Jupiter have shown that the (Great Red Spot) is shallow and thin compared to its horizontal dimension, as it is about 500 km vertically long,” Sánchez-Lavega said. .
In the future, researchers will attempt to simulate the storm’s shrinking rate over time to understand the processes that keep the storm stable, and to determine whether the storm will persist for years or dissipate once it reaches a certain size reached – which could possibly have been the cause. fate of Cassini’s permanent spot.
“I like these kinds of articles that delve into pre-photographic observations,” says Michael Wong, a research scientist at the University of California, Berkeley and co-author of the 2018 article, after reading Sánchez-Lavega’s research. “(Our) paper used tracking data back to 1880, but the new Sánchez-Lavega paper went back further and used data from signatures. The supplementary material for this article is also great.”
Wong was not involved in the new investigation.
“We can still learn a lot about these planets by making continuous long-term observations of their weather and climate.”
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