Lia Siegelman had I was just studying the swirling waters of the Southern Ocean, which surrounds Antarctica, when I came across a poster image of cyclones around Jupiter’s North Pole, taken by NASA’s Juno spacecraft. “I looked at him and he was surprised,‘ Hey, this looks like turbulence in the ocean, ’” he says.
So Siegelman, a researcher at the Scripps Institution of Oceanography in San Diego, turned her attention to the latest detailed images of the outer planet. She and her team first demonstrated that a kind of convection seen on Earth explains the physical forces and energy sources that create cyclones on Jupiter. (Since air and water are both “fluids,” from a physical perspective, the same principles apply to the atmosphere of the gas giant and our oceans.) Today they published their findings in the magazine. Nature physics.
Jupiter, the 4-pound elephant elephant in our solar system, makes giant cyclones, large storms that revolve around low-pressure areas. Some are thousands of miles wide, as large as the continental United States, with wind gusts of up to 250 miles per hour. Eight of the largest have been detected at the North Pole of the planet and five at the South Pole. Scientists have speculated for years about their origins, but by tracing these storms and measuring their wind speeds and temperatures, Siegelman and his colleagues showed how they actually form. Small rotating vortices appear here and there among the turbulent clouds, not so different from the ocean eddies known as Siegelman, and then begin to fuse with each other. Cyclones grow by continuously thickening smaller clouds and getting energy from them, so they keep spinning, he says.
It’s a smart way to study extreme weather on a planet more than 500 million miles away. “The authors are clearly drawing on meteorology and oceanography. These people are taking this rich literature and applying it in sophisticated ways to a planet we can barely touch,” says Morgan O’Neill, a Stanford atmospheric scientist who he models the physics of hurricanes and tornadoes on Earth and has applied his work to Saturn.
In particular, says O’Neill, the team of scientists demonstrates how, like storms on Earth, Jupiter’s cyclones accumulate through a process with a name that sounds dirty: “wet convection.” The warmer, less dense air, in the depths of the planet’s atmosphere, rises gradually, while the cooler, denser air, near the cold void of space, drifts down. This creates turbulence, which can be seen in Jupiter’s swirling and humid ammonia clouds.