Exploring oxygen ions in Jupiter's innermost radiation belts

The high concentration of high-energy oxygen and sulfur in the distant magnetosphere is a result of Io's volcanic eruptions, but another source must be responsible for the high concentration of high-energy oxygen in the inward part of Amalthea. Credit: MPS

The invisible, torus is formed by fast moving charged particles being trapped in the magnetic field of planets like Earth and Jupiter. 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. Jupiter has the most extreme radiation belts in the solar system. The most comprehensive study to date was presented by researchers from the California Institute of Technology, the California Institute of Technology Applied Physics Laboratory, the Laboratory of Instrumentation and Experimental Particle Physics, and the Academy of Athens.

The region within the moon's orbit of the gas giant is the scene of the highest energetic particle densities and velocities, which is similar to Jupiter's massive magnetic field. The second of the four large Jovian satellites named "Galilean moons" is seen from Jupiter. The innermost moon is Io. Three space missions have so far ventured into this innermost part of the radiation belts and performed in-situ measurements. "Unfortunately, the data from Pioneer 11 and Juno do not allow us to conclude beyond doubt what kind of ion the spacecraft encountered there," says Dr. Roussos, lead author of the new study. Their origin and energies were not clear until now. Only the rediscovered data from the last months of the Galileo mission can improve this situation.

The inner radiation belts are where I went.

The Jupiter system was reached by NASA's Galileo in 1995. The mission spent the next eight years providing fundamental insights into the distribution and dynamics of the particles, thanks to the Heavy Ion Counter and the Energetic Particle Detector. The outer regions of the radiation belts were the only areas it flew through. When a greater risk was justified, Galileo went into the innermost region of the moons. The third and fourth moons of the giant planet are visible from Jupiter. Io and Europa lie farther away from each other.

The measurement data from the inner region of the radiation belt would be heavily corrupted because of the exposure to strong radiation. Roussos started working on the current study three years ago, and he had expectations that neither of the instruments was specifically designed to operate in such a harsh environment. The researcher wanted to see himself. He was a member of NASA's Cassini mission and witnessed the final, similarly daring, orbits at Saturn two years before. Roussos kept thinking about the Galileo mission. He was surprised that there were some data sets that could be processed and analyzed.

The oxygen ion is mysterious.

The authors of the current study have been able to determine for the first time the ion composition within the inner radiation belts, as well as the ion's velocities and spatial distribution, thanks to this scientific treasure. The region within the Io's radiation belt is dominated by protons, but also contains large amounts of oxygen and sulfur ion, with oxygen ion prevailing among the two. Roussos says that the energy distribution of the heavy ion outside the orbit of Amalthea suggests that they are largely introduced from a more distant region of the radiations belts. The moon Io, with its more than 400 active volcanoes, is likely to be the main source of sulfur and sulfur dioxide.

The ion composition changes in favor of oxygen further inside. Roussos says that the concentration and energy of oxygen ion are higher than expected. The two small moons of Thebe and Amalthea form a kind of natural ion barrier, so the concentration should be decreasing. This behavior is known from the radiation belts of theSaturnian system.

There is only one explanation for the increased concentration of oxygen ion in the innermost region of the radiation belts. The release of oxygen following the collision of sulfur ion with the fine dust particles of Jupiter's rings is one possibility. The rings are much fainter than the ones on the other side of the planet. It is possible that low-frequency waves in the magnetospheric environment of the innermost radiation belts heat oxygen ion to the observed energies.

Roussos says it is not possible to distinguish between the two possible sources. The researcher hopes that their future exploration with a dedicated space mission would justify their future exploration with Jupiter's radiation belts extending into the astrophysical realm.

A source of very energetic oxygen is located in Jupiter's inner radiation belts. Science.org has a DOI of/10.1126/sciadv.abm4234.

Science Advances has journal information.

The news about exploring oxygen ion in Jupiter's innermost radiation belts was retrieved on January 12.

The document is copyrighted. Any fair dealing for the purpose of private study or research cannot be reproduced without written permission. The content is not intended to be used for anything other than information purposes.