Smaller storms feed Jupiter's Great Red Spot

A new report from the American Geophysical Union reveals that Jupiter’s Great Red Spot, a massive storm that is about twice as wide as Earth, is being fed by smaller storms.

Over the past few years, a series of anticyclones crashed into the Great Red Spot and caused chunks of red clouds to flake off, which shrunk the larger storm. The new study shows that these disruptions are just superficial, and do not affect the full depth of the Red Spot.

Study lead author Agustín Sánchez-Lavega is a professor of applied physics at the Basque Country University in Bilbao. He explained that as the larger storm absorbs these smaller storms, it “gains energy at the expense of their rotation energy.”

“The intense vorticity of the Great Red Spot, together with its larger size and depth compared to the interacting vortices, guarantees its long lifetime,” said Professor Sánchez-Lavega.

Prior to 2019, the giant storm only encountered a couple of anticyclones per year. In the last couple years, however, the Red Spot has been hit by as many as two dozen smaller storms in a year. 

The researchers set out to investigate whether the anticyclones had disturbed the spin of the giant storm. The Great Red Spot spins in the atmosphere near the planet’s equator, with wind speeds of up to 335 miles per hour along its border.

Anticyclones spin in the opposite direction of cyclones around a center with high atmospheric pressure. The Great Red Spot is an anticyclone that is six to seven times as big as the smaller anticyclones that have been colliding with it. The “smaller” storms on Jupiter are still about 10 times the size of the largest terrestrial hurricanes.

Professor Sánchez-Lavega and his team looked at satellite images of the Great Red Spot for the past three years taken from the Hubble Space Telescope and the Juno spacecraft, as well as photos taken by a network of amateur astronomers with telescopes.

The researchers found that the smaller anticyclones pass through the high-speed peripheral ring of the Great Red Spot before circling around the red oval. 

According to Professor Sánchez-Lavega, the invading storms create some chaos in an already dynamic situation, temporarily changing the Red Spot’s 90-day oscillation in longitude, and “tearing the red clouds from the main oval and forming streamers.”

Experts are not sure how the Red Spot initially formed or what has been causing it to shrink for at least 150 years, but the current study suggests that smaller storms are helping to maintain it. 

“The ingestion of anticyclones is not necessarily destructive; it can increase the GRS rotation speed, and perhaps over a longer period, maintain it in a steady state,” said Professor Sánchez-Lavega.

The study is published in the Journal of Geophysical Research: Planets.

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By Chrissy Sexton, Earth.com Staff Writer