Jupiter's Great Red Spot Explained
The Great Red Spot on Jupiter is a persistent anticyclonic storm that just won't die, making it one of the solar system's most mysterious landmarks. Earth observations estimate that the storm has been around for centuries and it is not known how long the storm and spot will last — even when fluid dynamics prove that the storm must die.
However, for the first time, researchers have made progress on divulging the secrets of the giant storm's longevity.
The Red Spot is about 24,000 km across, east to west, 12,000 km from north to south, and a mere 40 km deep. Its wind are roaring around at about 225 miles per hour and this incredible monster has been observed from Earth almost continuously for at least 150 years, says Philip Marcus of University of California, Berkeley. But based on all the modeling that's been done to try and explain the Red Spot, it just isn't possible.
"Based on current theories, the Great Red Spot should have disappeared after several decades. Instead, it has been there for hundreds of years," said Pedram Hassanzadeh, who is a post-doctoral fellow at Harvard's Center for the Environment and the Department of Earth and Planetary Sciences.
To better understand the Great Red Spot, Marcus and Hassanzadeh built a model that took into account the third, vertical dimension of the storm which was previously ignored.
When Marcus and Hassanzadeh factored in the interactions of the thin storm with the layers of atmosphere below it, the sphericity of Jupiter, and the changing densities of the gases at different levels in the atmosphere, the modeled lifespan of the storm jumped dramatically. The secret source of power for the storm is energy that is moving vertically, not horizontally.
The vertical motion turns out to hold the key to the Red Spot's persistence. As the vortex loses energy, the vertical flow transports hot gases from above and cold gases from below the vortex towards its center, restoring part of its lost energy.
"What we found is that the spot can last 800 years," said Hassanzadeh. The 150 years on record for the Red Spot is just a minimum, he explained.
The discovery of the causes of the Red Spot's longevity could also help explain some other natural vortices that also last far longer they they ought to, said Marcus.
Jupiter image via Shutterstock.