Leah Siegelman had was just studying the swirling waters of the Southern Ocean surrounding Antarctica when he stumbled upon a poster image of cyclones around Jupiter’s north pole taken by NASA’s Juno spacecraft. “I looked at him and I was just amazed, ‘Wow, this looks just like turbulence in the ocean,'” she said.
So Siegelman, a researcher at the Scripps Institute of Oceanography in San Diego, turned his attention to the latest detailed images of the outer planet. She and her team proved for the first time that a type of convection observed on Earth explains the physical forces and energy sources that create cyclones on Jupiter. (Since air and water are “fluids” from a physics point of view, the same principles apply to the atmosphere of the gas giant and our oceans.) They published their findings today in the journal Physics of nature.
Jupiter, the elephant weighing 4 octylon pounds in our solar system, creates giant cyclones, large storms that revolve around low-pressure areas. Some are thousands of miles wide – as much as the continental United States – with gusts of wind up to 250 miles per hour. Eight of the largest have been spotted at the planet’s north pole and five at the south pole. Scientists have been speculating for years about their origins, but by mapping these storms and measuring their wind speed and temperature, Siegelman and her colleagues have shown how they actually form. Small whirling vortices pop up here and there in the stormy clouds – not so different from the ocean vortices Siegelman knows – and then begin to merge with each other. Cyclones are growing, constantly absorbing smaller clouds and gaining energy from them, so they keep spinning, she says.
This is a smart way to study extreme weather on a planet that is more than 500 million miles away. “The authors obviously draw from the disciplines of meteorology and oceanography. These people are taking this rich literature and applying it in complex ways to a planet we can barely touch, “said Morgan O’Neill, a Stanford atmospheric scientist who modeled the physics of hurricanes and tornadoes on Earth and applied his work to Saturn.
In particular, says O’Neill, the team demonstrates how, like thunderstorms on Earth, Jupiter’s cyclones accumulate through a process with a rough-sounding name: “wet convection.” The warmer air with less density, deep in the planet’s atmosphere, gradually rises, while the cooler and denser air, near the cooler vacuum of space, is carried down. This creates turbulence, which can be seen in the spinning, moisture-filled ammonia clouds of Jupiter.