A fleeting flyby of Ganymede has revealed that it sparkles northern lights may behave much more like Earth’s than scientists expected.
During a close pass on July 7, 2021, NASA’s Juno spacecraft captured the most detailed ultraviolet views to date of a The Jovian Moon glowing aurora borealis. The new analysis, completed by a team led by the Laboratory of Atmospheric and Planetary Physics (LPAP) at the University of Liège, shows that Ganymede’s auroras are not smooth, continuous ovals. Instead, they splinter into small, bright spots – structures that mirror features seen in the Earth’s own northern lights.
Although we know that auroras are not unique to Earth, they have been seen Venus, MarchJupiter, Saturn and Uranus — Ganymede is the only moon we know of that has its own magnetic field, which is a crucial ingredient for the aurora borealis. On Earth, auroras occur when charged solar particles slam into the magnetosphere, which directs them towards the poles. These particles then interact with gases in the atmosphere and glow in different colors, including green and red. On Ganymede, the auroras are produced via interactions with Jupiter’s enormous magnetosphere rather than the solar wind.
“Observations of Ganymede’s auroras prior to Juno were limited by the spatial resolution of ground-based observations, and they could not resolve the small-scale structures typical of planetary auroras,” said Philippe Gusbin, whose master’s thesis inspired the study. Juno’s ultraviolet spectrograph resolved details just a few kilometers across, revealing the “gems” of the aurora borealis.
Because Juno’s encounter with Ganymede lasted less than 15 minutes—and the spacecraft will not return—scientists cannot yet determine how often these “gem” features appear. That task can fall on JUICEThe European Space Agency mission is on its way to Jupiter, which is expected to begin extended studies of Ganymede after its arrival in 2031.
A study on these results was published on 6 January in the journal Astronomy & Astrophysics.
