What Causes Jupiter’s Red Storm?

At one time, the storm was at least 20,000 miles (32,000 km) in diameter and big enough to envelop three Earths. It is similar to a hurricane on Earth, rotating counterclockwise with a maximum windspeed of 268 miles per hour (430 km/h), almost twice as fast as the worst hurricanes on Earth. Historic observations date as far back as the 1600s. Since then, the spot has changed, fluctuating between a deep red and a pale salmon color. Laboratory experiments suggest that complex organic molecules, red phosphorus, and other sulfur compounds cause the vibrant color.

But since the 1930s, the storm has shrunk to half its largest diameter. Even though it may be dwindling in size, the longevity and enormity of our solar system’s biggest storm is full of mystery. The reason for the persistence of the Great Red Spot is unknown, but presumably comes from the fact that it never moves over land, unlike hurricanes on Earth. Jupiter is composed of hydrogen and a small amount of helium and has no “land” in its form. Jupiter’s internal heat source is a driving force, and the spot tends to absorb nearby weaker storms. However, based on computer models, the spot should have disappeared after several decades. Waves and turbulence in and around the storm sap it of energy. The powerful jet streams that surround the spot should slow its spinning. And even though the storm absorbs smaller ones, researchers say that doesn’t happen enough to explain the storm’s longevity. Some scientists think vertical flows in the storm are just as important as the more-studied horizontal flows. When the storm loses energy, vertical flows move hot and cold gases in and out of the storm, restoring energy. Understanding Jupiter’s red storm could reveal more clues about the vortices in Earth’s oceans and also the nurseries of stars and planets. Philip Marcus, a fluid dynamicist and planetary scientist at the University of California at Berkeley, explains the importance of understanding the Great Red Spot: “Vortices with physics very similar to the GRS are believed to contribute to star and planet formation processes, which would require them to last for several million years”—even as the Great Red Spot shrinks, it retains enormous significance for Earth and the very beginnings of the solar system.

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