For decades, Saturn seemed to break the laws of physics. Scientists measured the giant planet's rotation and found it appeared to spin at slightly different speeds. This should have been impossible.
Professor Tom Stallard from Northumbria University in England finally solved the mystery using the James Webb Space Telescope. Saturn's spin was never actually changing. Instead, powerful winds high in its atmosphere were distorting the signals scientists used to measure rotation.
Saturn is a gas giant with no solid surface, so scientists measure its rotation indirectly using its magnetic field and radio emissions. When NASA's Cassini spacecraft began studying Saturn in 2004, measurements suggested the rotation rate was slowly drifting. The numbers did not match earlier observations from NASA's Voyager probes in the 1980s.
Stallard's team used Webb to observe Saturn's northern auroral region continuously. They measured the infrared glow of a molecule called the trihydrogen cation, which forms in the upper atmosphere. Webb's readings were ten times sharper than earlier instruments.
The researchers discovered that Saturn's aurora heats the upper atmosphere. This heat drives winds that generate electrical currents, which power the aurora. This self-sustaining cycle distorts the radio signals used to measure the planet's spin.
The work was published in the Journal of Geophysical Research: Space Physics and involved researchers from institutions including Boston University, the University of Leicester, and Imperial College London. This discovery changes how scientists understand planetary atmospheres everywhere.