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Jupiter’s iconic Great Red Spot is a massive storm that has swirled in the atmosphere of the solar system’s largest planet for years.
But astronomers have debated the vortex’s real age, as well as when and how it formed. Some experts believed it was centuries old and 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 else on Jupiter in 1665. And despite being younger than previously believed, the storm continues to be the largest and longest-lasting vortex known on our entire planet. solar system, according to researchers.
A study detailing the findings was published June 16 in the journal Geophysical Research Letters.
Keeping an eye on the storm
Jupiter’s striking appearance features streaks 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 composed of ammonia gases, ice water, sulfur and phosphorus, according to NASA. Speedy jet streams sculpt and stretch clouds into long ribbons.
Cyclonic storms on Jupiter can last for years because the gaseous planet does not have a solid surface, which can slow down the storms.
The Great Red Spot is a massive vortex in Jupiter’s atmosphere about 16,350 kilometers wide, similar to the diameter of Earth. according to NASA. The storm reaches a height of more than 200 miles (322 kilometers) high.
Strong winds are blowing at 450 kilometers per hour along the storm’s boundaries. And its characteristic red hue comes from atmospheric chemical reactions.
The iconic feature is visible even through small telescopes.
And it looked similar to a dark oval at the same latitude that Cassini first spotted when he looked through his telescope in the mid-1600s. He referred to the feature he had 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-shaped storm at the same latitude on Jupiter, which persisted and is still observed today. But astronomers have long questioned whether it was possible that the storms were the same phenomenon, or two different vortices that manifested in the same location more than a century apart.
A team of researchers aiming to solve the enigma gathered a wealth of data, analyzing 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 recreate the storm’s potential longevity.
“From measurements of sizes and movements, we deduce that it is highly unlikely that the current Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” said the study’s 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 Red Spot exceeds 190 years.”
The Permanent Spot 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 was 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 that describe the phenomenon,” Sánchez-Lavega said. “Others before us have explored these observations, and we have now quantified the results.”
Decreasing in size
By analyzing historical data, researchers also explored the origin of the storm, 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 one entity.
Although the first two scenarios resulted in cyclones, they differed in shape and other characteristics witnessed in the Great Red Spot.
“We also think that if one of these unusual phenomena occurred, it or its consequences in the atmosphere must have been observed and reported by astronomers at the time,” said Sánchez-Lavega.
But researchers believe that the persistent atmospheric storm cell, which resulted from intense wind instability, produced the Great Red Spot.
The storm measured about 24,200 miles (about 39,000 kilometers) at its longest point, according to data from 1879, but has been shrinking and becoming rounder over time, and is now about 8,700 miles long. (14,000 kilometers).
Previous research, published in March 2018, showed that the Great Red Spot is growing taller as it decreases in size overall. O 2018 study also used archival data to study how the storm changed over time.
Data from modern space missions, such as NASA’s Juno probe, have given astronomers an unprecedented look at 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 (310.7 miles) long.” , said Sánchez-Lavega. .
In the future, 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 over the next few years or disappear once it reaches a certain size – which may have been the case. fate of the Cassini Permanent Spot.
“I love articles like this that delve deeper 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 was older and used data from hand drawings. 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 weather and climate.”
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