Jupiter’s northern lights are the most powerful in the solar system, but new observations from the James Webb Space Telescope (JWST) have revealed surprising details about how they work.
Scientists have discovered unusual temperature patterns and dramatic changes in the density of charged particles high in Jupiter’s atmosphere—features that had never been seen before.
The research, published in Geophysical Research Letters, was led by Katie Knowles, a Ph.D. researcher in planetary physics at Northumbria University.
Using JWST’s powerful infrared instruments, the team captured the first detailed measurements of the glowing auroral “footprints” created by two of Jupiter’s moons, Io and Europa.
Auroras on Earth are mainly caused by charged particles from the solar wind interacting with our planet’s magnetic field.
Jupiter’s auroras work differently. In addition to solar activity, the giant planet’s four large moons—Io, Europa, Ganymede, and Callisto—also play a major role.
As these moons move through Jupiter’s powerful magnetic field, they generate electrical currents that travel along magnetic field lines and slam into the planet’s upper atmosphere, creating bright spots known as auroral footprints.
The JWST observations allowed scientists to do something that had not been possible before: measure the physical properties of these glowing footprints. Earlier studies had only recorded how bright they were, but the new data revealed their temperature and the density of charged particles within them.
During a 22-hour observing session in September 2023, the team scanned around the edge of Jupiter as the northern lights rotated into view. While tracking the auroras, they captured images of the footprints linked to Io and Europa.
What they found surprised them. One image showed a cold region inside Io’s auroral footprint that was much cooler than expected. The temperature in this spot was about 538 Kelvin (around 265°C), compared with roughly 766 Kelvin (about 493°C) in the surrounding aurora. Even more surprising, the cold area contained extremely dense concentrations of charged particles—about three times higher than those seen in Jupiter’s main aurora.
Io plays a key role in this process. It is the most volcanically active world in the solar system, constantly spewing material into space. This material becomes ionized and forms a huge doughnut-shaped cloud of plasma around Jupiter known as the Io plasma torus. As Io moves through this plasma, it generates powerful electric currents that help produce the bright auroral footprints.
The JWST data also showed that conditions within these footprints can change rapidly. Temperatures and particle densities varied dramatically within minutes, suggesting that the flow of energetic electrons hitting Jupiter’s atmosphere can fluctuate very quickly.
Scientists believe these discoveries could help them better understand how giant planets and their moons interact. Similar effects might also occur in other planetary systems, including those involving Enceladus and Saturn.
To learn more, Knowles has already begun analyzing new observations collected in early 2026 using NASA’s NASA Infrared Telescope Facility in Hawaii.
By watching the auroral footprints rotate with Jupiter over several nights, researchers hope to find out whether these mysterious cold spots are rare events or a common feature of the giant planet’s spectacular light show.
Source: KSR.
