Here’s How Smaller Storms Affect Jupiter’s Great Red Spot

Far from being destructive, a series of smaller storms may actually be helping maintain Jupiter's Great Red Spot, a storm in the gas giant's southern hemisphere with crimson-colored clouds that spin counter-clockwise at wind speeds that exceed those in any storm on Earth. The Great Red Spot is about twice the diameter of Earth and blows at speeds of up to 540 kilometers per hour along its periphery.

"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 study lead author Agustin Sanchez-Lavega, Professor at the Basque Country University in Bilbao, Spain.

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As the larger storm absorbs these smaller storms, it "gains energy at the expense of their rotation energy." However, the Red Spot has been shrinking for at least the past 150 years, dropping from a length of about 40,000 kilometers in 1879 to about 15,000 kilometers today, and researchers still aren't sure about the causes of the decrease, or indeed how the spot was formed in the first place.

The research, published in the Journal of Geophysical Research: Planets, found the smaller anticyclones pass through the high-speed peripheral ring of the Great Red Spot before circling around the red oval. The smaller 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," Sanchez-Lavega said.

The researchers still do not know what has caused the Red Spot to shrink over the decades. But these anticyclones may be maintaining the giant storm for now. "The ingestion of (anticyclones) is not necessarily destructive; it can increase the GRS (Great Red Spot of Jupiter) rotation speed, and perhaps over a longer period, maintain it in a steady-state," Sanchez-Lavega said.

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Sanchez-Lavega and his colleagues looked at satellite images of the Great Red Spot for the past three years taken from the Hubble Space Telescope, the Juno spacecraft in orbit around Jupiter, and other photos taken by a network of amateur astronomers with telescopes. Cyclones like hurricanes or typhoons usually spin around a center with low atmospheric pressure, rotating counter-clockwise in the northern hemisphere and clockwise in the southern, whether on Jupiter or Earth.

Anticyclones spin the opposite way as cyclones, around a center with high atmospheric pressure. The Great Red Spot is itself an anticyclone, though it is six to seven times as big as the smaller anticyclones that have been colliding with it. But even these smaller storms on Jupiter are about half the size of the Earth and about 10 times the size of the largest terrestrial hurricanes. Before 2019, the larger storm was only hit by a couple of anticyclones a year while more recently it was hit by as many as two dozen a years. (IANS/SP)