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Jupiter’s iconic Red Spot is a massive storm that has been raging within the atmosphere of the largest planet in the solar system for years.
But astronomers have debated the actual age of the vortex, as well as when and how it formed. Some experts believed it was hundreds of years old and was first noticed by the Italian astronomer Giovanni Domenico Cassini in the 17th century, while others thought the storm was later.
Now, new research suggests that the Great Red Spot formed about 190 years ago, meaning that Cassini observed something else on Jupiter in 1665. And despite being younger than previously believed, the storm is still the largest and longest-lasting vortex throughout our. solar system, according to researchers.
A study detailing the results appeared June 16 in the journal Geophysical Research Letters.
Eye of the storm
Jupiter’s striking streaks and spots are made up of the planet’s encircling cloud bands and cyclonic storms. Its colors come from the composition of different atmospheric layers, which are individually made of ammonia gases, water ice, sulfur and phosphorus, according to NASA. Swift jet streams stretch the clouds into long bands.
Cyclonic storms on Jupiter can last for years because the gas planet does not have a solid surface, which can slow down storms.
The Great Red Spot is a giant vortex within Jupiter’s atmosphere that is about 10,159 miles (16,350 kilometers) wide, about the diameter of Earth, according to NASA. The storm towers at a height of more than 200 miles (322 kilometers) high.
Screaming winds move at 280 miles per hour (450 kilometers per hour) along the boundaries of the storm. And its signature red color comes from atmospheric chemical reactions.
The iconic feature is visible, even through small telescopes.
And it looked like a dark oval at the same latitude that Cassini first saw looking through his telescope in the mid-1600s. He referred to its feature as the “Permanent Spot,” and it was observed by Cassini and other astronomers until 1713, when they lost sight of the storm.
Then, in 1831, astronomers saw a large oval storm at the same latitude on Jupiter, which remained and is still visible today. But astronomers have been questioning for a long time whether it was possible that the storms were the same phenomenon, or two different vortices that appeared in the same place more than a century apart.
A team of researchers aiming to solve the enigma collected a wealth of data, analyzing historical drawings and images that show the structure, location and size of the site over time. The data was used to create numerical models that recreated the potential longevity of the storm.
“From measurements of sizes and motions, we found that the Great Red Spot was unlikely to be 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 Red Spot is more than 190 years.”
The Permanent Spot lasted for about 81 years, and none of the drawings analyzed by the team mentioned any particular color for the storm, according to the study’s authors.
“It was very encouraging and motivating to go to the notes and drawings of Jupiter and its Permanent Spot made by the great astronomer (Cassini), and to his articles in the second half of the 17th century describing the phenomenon,” Sánchez -Lavega said. “These observations have been explored by others before us, and now we have quantified the results.”
Shrinking in size
While going through the historical data, the researchers also explored how the storm evolved by performing simulations on supercomputers using models of how vortices behave in Jupiter’s atmosphere.
The team ran simulations to see if the Great Red Spot arose from a giant storm, the merging of smaller vortices that produced Jupiter’s strong and alternating winds, or from an instability in the winds that could produce an atmospheric storm cell. A storm cell is an air mass shaped by updrafts and downdrafts that move as a single entity.
Although the first two cases resulted in cyclones, they had a different shape and other characteristics seen in the Great Red Spot.
“We also think that if one of these unusual phenomena happened, the astronomers at the time would have to see and report its consequences in the atmosphere,” said Sánchez-Lavega.
But the researchers believe that the persistent atmospheric storm cell, caused by 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 it has been shrinking and becoming more precise over time, and is now about 8,700 miles (14,000 kilometers ).
Previous research, published in March 2018, shows that the Great Red Spot is growing 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 given astronomers unprecedented views of the storm’s shape.
“Various instruments on board the Juno mission in orbit around Jupiter have shown that the (Great Red Spot) is shallow and thin compared to its horizontal dimension, as it is about 500 km (310.7 miles) long vertically,” Sánchez said – Lavega.
From now on, the researchers will try to recreate the rate of contraction of the storm over time to understand the processes that keep the storm stable, as well as to decide whether it will last for years to come or disappear when it reaches a certain size – which may mean. the fate of Cassini’s Permanent Spot.
“I love articles like this that explore 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 data traced back to 1880, but the new Sánchez-Lavega paper went back further and used data from hand drawings. The supplemental materials for this article are great, too.”
Wong was not involved in the new study.
“We have a lot to learn about these planets through continuous long-term observation of their weather and climate.”
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