To his own surprise, among many unusable data sets there were also some that could be processed and analyzed with much effort. 'The thought of the long-completed Galileo mission kept coming to my mind,' Roussos recalls. As a member of NASA's Cassini mission, he had witnessed Cassini's final, similarly daring orbits at Saturn two years earlier and analyzed the unique data from that final mission phase. Nevertheless, the researcher wanted to see for himself. After all, neither of these two instruments was specifically designed to operate in such a harsh environment”, Roussos describes his expectations when he started working on the current study three years ago. 'Because of the exposure to strong radiation, it was to be expected that the measurement data from HIC and EPD from the inner region of the radiation belt would be heavily corrupted. The orbits of Io and Europa lie farther outward.

Viewed from Jupiter, Amalthea and Thebe are the third and fourth moons of the giant planet.

Only in 2003, shortly before the end of the mission, when a greater risk was justifiable, Galileo ventured into the innermost region within the orbits of the moons Amalthea and Thebe. However, to protect the spacecraft, it initially flew solely through the outer, less extreme regions of the radiation belts. Equipped with the Heavy Ion Counter (HIC), contributed by the California Institute of Technology, and the Energetic Particle Detector (EPD), developed and built by Johns Hopkins Applied Physics Laboratory in collaboration with the MPS, the mission spent the following eight years providing fundamental insights into the distribution and dynamics of charged particles around the gas giant. NASA's Galileo spacecraft reached the Jupiter system in 1995. Only the now rediscovered data from the last months of the Galileo mission is detailed enough to improve this situation. 'Therefore, their energies and origin were also unclear until now,' he adds. 'Unfortunately, the data from Pioneer 11 and Juno do not allow us to conclude beyond doubt what kind of ions the spacecraft encountered there,' says MPS scientist Elias Roussos, lead author of the new study, describing the current state of research. With the space probes Pioneer 11 in the mid-1970s, Galileo from 1995 to 2003, and currently Juno, three space missions have so far ventured into this innermost part of these radiation belts and performed in-situ measurements. Viewed from Jupiter, Europa is the second of the four large Jovian satellites named “Galilean moons” after their 17th century discoverer. Like Jupiter's massive magnetic field, its radiation belts extend several million kilometers into space however, the region within the moon's orbit of Europa, an area with a radius of about 670,000 kilometers around the gas giant, is the scene of the highest energetic particle densities and velocities. In their new publication, researchers from the MPS, the California Institute of Technology (USA), the Johns Hopkins Applied Physics Laboratory (USA), the Laboratory of Instrumentation and Experimental Particle Physics (Portugal), and the Academy of Athens (Greece) now present the most comprehensive study to date of the heavy ions in Jupiter's inner radiation belts. In this respect, the gas giant Jupiter sports the most extreme radiation belts in the Solar System. With their high velocities reaching almost the speed of light, the particles can ionize other molecules when they collide, creating a hazardous environment that can also be dangerous to space probes and their instruments. Planets like Earth, Jupiter, and Saturn with global magnetic fields of their own are surrounded by so-called radiation belts: Trapped in the magnetic field, fast moving charged particles such as electrons, protons, and heavier ions whiz around thus forming the invisible, torus-shaped radiation belts.

Jupitors io moon energy source