Why Jupiter's Great Red Spot Should be Gone But Isn't
A team of scientists claim to have an explanation for why the so-called Great Red Spot on Jupiter -- a gargantuan storm large enough to engulf Earth three times -- has not disappeared.
Among planetary scientists, there is a consensus that the Great Red Spot, a defining feature of the distant world, should have disappeared centuries ago. But why hasn't it?
Pedram Hassanzadeh, a postdoctoral fellow at Harvard University, and Philip Marcus, a professor of fluid dynamics at the University of California, Berkeley, think they can explain why, at least partly.
"Based on current theories, the Great Red Spot should have disappeared after several decades. Instead, it has been there for hundreds of years," Hassanzadeh said in a statement.
The Great Red Spot is a vortex, Hassanzadeh explained. Based on what we know about vorticies like the Red Spot elsewhere, Jupiter's storm should have dissipated: turbulent winds sap the vortexes' energy, it loses energy by radiating heat, and it sits between two jet streams that should slow down its spinning by flowing in opposite directions.
Some have argued that the Red Spot gains energy by absorbing smaller vorticies. "Some computer models show that large vortices would live longer if they merge with smaller vortices, but this does not happen often enough to explain the Red Spot's longevity," Marcus said.
Marcus and Hassanzadeh developed their own model of the Red Spot, which differs from other models of the storm because it is very high resolution and fully three dimensional. Their model was also different because took into account vertical air flows as well as the more prominent horizontal winds, where most of the storm's energy resides.
"In the past, researchers either ignored the vertical flow because they thought it was not important, or they used simpler equations because it was so difficult to model," Hassanzadeh said.
But the vertical air flow, it turns out, is the key to the storm's longevity, the researchers learned. As the vortex loses energy, the vertical air flow transports hot gas from above and cold gas from below toward the center of the vortex, restoring its energy. Their model also predicts a radial air flow, which sucks winds from the high-speed jet streams into the center of the storm, providing more power.
The new model accounts for much of the Great Red Spot's mysterious longevity, but it does not account for all of it.
They are continuing to fine-tune the model to learn more about the enormous storm.