In a significant astronomical achievement, an international research team, using data from NASA's Juno mission, has definitively detected aurora on Jupiter's moon Callisto. This discovery completes the aurora data for all four of Jupiter's Galilean moons—Io, Europa, Ganymede, and Callisto—providing a more comprehensive understanding of the dynamic interactions within the Jovian system.
Jupiter is known for its brilliant auroras, generated by the interaction of charged particles with its powerful magnetic field. The auroras on its moons, however, are a unique phenomenon arising from their individual electromagnetic interactions with Jupiter's magnetosphere, creating distinct "satellite footprints" in Jupiter's atmosphere. While auroral signatures from Io, Europa, and Ganymede had been previously observed, Callisto's remained elusive due to its faintness and tendency to be obscured by Jupiter's brighter auroral oval.
The breakthrough occurred in September 2019, during Juno's 22nd orbit. A significant solar wind stream impacted Jupiter, causing its auroral oval to shift towards the equator. This celestial alignment, combined with Juno's opportune position, allowed for the simultaneous observation of all four Galilean moons and the successful detection of Callisto's auroral signature. This event provided researchers with a unique opportunity to characterize Callisto's aurora using ultraviolet, radio, plasma, and wave data, confirming a pattern consistent with its sibling moons.
This comprehensive data set not only completes the aurora portrait of the Jovian system but also opens new avenues for scientific inquiry. Scientists can now delve deeper into the properties of plasma, electric currents, and magnetic fields that drive auroral activity on these distant moons. The findings were published in Nature Communications.
Looking ahead, the exploration of Jupiter's moons continues with upcoming missions. NASA's Europa Clipper mission, launched on October 14, 2024, is set to arrive in the Jovian system in April 2030 for an in-depth study of Europa. Similarly, the European Space Agency's Jupiter Icy Moons Explorer (JUICE) mission, launched on April 14, 2023, will arrive in 2031 to conduct detailed studies of Ganymede, Callisto, and Europa, with a particular focus on Ganymede. These missions promise to further illuminate the mysteries of the Jovian system.