Secret Behind the Longevity of Jupiter's Great Red Spot Revealed

Jupiter's Great Red Spot is one of the planet's most defining features. Yet it won't remain present in our telescopes' fields forever; the spot is actually a massive storm, big enough to engulf the Earth two or three times over. In fact, this storm should have disappeared centuries ago. Now, scientists have found out exactly why Jupiter's spot has remained to this day.

"Based on current theories, the Great Red Spot should have disappeared after several decades," said Pedram Hassanzadeh, one of the researchers, in a news release. "Instead, it has been there for hundreds of years."

Many different processes can dissipate vortices like the Red Spot. The turbulence and waves in and around the Red Spot sap the energy of its winds. The vortex also loses energy by radiating heat. In addition, it sits between two strong jet streams that flow in opposite directions which, in theory, could slow down its spinning.

In order to find out why these processes didn't extinguish this massive storm, the researchers created a computer model. This new model differed from existing ones because it was fully three dimensional and had very high resolution. While most vortex models focus on the swirling horizontal winds and ignore the vertical flows, this new model also took into account the less energetic vertical flows.

In fact, this vertical motion turns out to hold the key to the Red Spots persistence. As the vortex loses energy, the vertical flow transports hot gases from above and cold gases from below the vortex toward its center. This restores part of its lost energy. There's also a radial flow which sucks winds from the high-speed jet streams toward the vortex center. This pumps energy into the vortex, enabling it to last longer.

This finding doesn't just have implications for Jupiter's storm, though. It could also explain why ocean vortices, such as those formed near the Straits of Gibralter, can last for years in the Atlantic Ocean. Their vertical flow plays a role in the ocean ecosystem by lifting nutrients to the surface.

While the model explains some of the storm's power, it doesn't entirely explain the Red Spot's long life span. It's very possible that there's an occasional absorption of smaller vortices that provides the extra energy needed for hundreds of years of life. Currently, the scientists are modifying their model to take this fact into account.

The findings will be presented at the annual meeting of the American Physical Society's Division of Fluid Dynamics.