Jupiter is iconic, with its swirls of water and ammonia vapor that characterize its outer surface and its distinctive Giant Red Spot, a gigantic storm raging across its face.

But its mysteries abound — such as Jupiter’s strange and asymmetrical magnetic field, which has a strong area of magnetism in its equator called the “Great Blue Spot” — blue because that’s how it’s color-coded in maps tracing the magnetic field.

In an effort to understand the planet’s magnetic field better, a team of American scientists from Harvard University, the California Institute of Technology, NASA and the Southwest Research Institute in San Antonio, Texas studied an atmospheric jet — a high speed current in the gas giant’s atmosphere — in the Great Blue Spot. Their finding? It’s a dynamic system that fluctuates every four years or so.