Particle physics research

New research reveals oxygen ions in Jupiter’s innermost radiation belts

January 23, 2022 12:03 STI

Berlin [Germany], Jan 23 (ANI): NASA ended its Galileo mission to Jupiter on September 21, 2003, nearly 20 years ago. Today, German scientists have uncovered a new secret from the mission’s vast datasets.
For the first time, the research team, led by the Max Planck Institute for Solar System Research (MPS), was able to determine beyond doubt that the high-energy ions surrounding the gas giant as part of its inner radiation belt are mainly oxygen and sulfur ions.
The results of the study have been published in the journal “Science Advances”.
The ions are thought to come from volcanic eruptions on Jupiter’s moon Io. Near the orbit of the moon Amalthea, which orbits more interior Jupiter, the team discovered a surprisingly high concentration of high-energy oxygen ions that cannot be explained by volcanic activity on Io . A previously unknown ion source may have been at work here.
Planets like Earth, Jupiter, and Saturn with their own global magnetic fields are surrounded by so-called radiation belts: Trapped in the magnetic field, fast-moving charged particles such as electrons, protons, and ions heavier ones swirl thus forming the invisible. , torus-shaped radiation belts. With their high speeds reaching almost the speed of light, the particles can ionize other molecules when they collide, creating a hazardous environment that can also be hazardous to space probes and their instruments.
In this regard, the gas giant Jupiter sported the most extreme radiation belts in the solar system. In their new publication, researchers from MPS, California Institute of Technology (USA), Johns Hopkins Applied Physics Laboratory (USA), Laboratory of Instrumentation and Experimental Particle Physics (Portugal) and Academy of Athens (Greece ) presented the most comprehensive study to date of heavy ions in Jupiter’s inner radiation belts.
Like Jupiter’s massive magnetic field, its radiation belts stretched millions of miles into space; however, the region within Europa’s lunar orbit, an area with a radius of about 670,000 kilometers around the gas giant, was the scene of the highest energetic particle densities and velocities. Seen from Jupiter, Europa was the second of four large Jovian satellites named “Galilean moons” after their discoverer in the 17th century.

Io was the innermost Galilean moon. Along with 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 deepest part of these radiation belts and made measurements in if you. “Unfortunately, data from Pioneer 11 and Juno does not allow us to conclude beyond doubt what type of ions the spacecraft encountered there,” said MPS scientist Dr. Elias Roussos, lead author of the new study, outlining the current state of research. “Therefore, their energies and origin were unclear until now,” he added. Only the now rediscovered data from the last months of the Galileo mission was sufficiently detailed to improve this situation.
NASA’s Galileo spacecraft reached the Jupiter system in 1995. Equipped with the Heavy Ion Counter (HIC), provided by the California Institute of Technology, and the Energetic Particle Detector (EPD), developed and built by the Johns Hopkins Applied Physics Laboratory in conjunction with the MPS, the mission spent the next eight years providing fundamental information on the distribution and dynamics of charged particles around the gas giant. However, to protect the spacecraft, it initially flew only through the outer and less extreme regions of the radiation belts. It was not until 2003, shortly before the end of the mission, when a greater risk was justifiable, that Galileo ventured into the innermost region of the orbits of the moons Amalthea and Thebe. As seen from Jupiter, Amalthea and Thebes were the giant planet’s third and fourth moons. The orbits of Io and Europa were further apart.
“Due to the exposure to strong radiation, it was to be expected that the HIC and EPD measurement data of the inner region of the radiation belt would be highly corrupted. After all, neither of these two instruments ‘was specifically designed to operate in such a harsh environment,” Roussos described his expectations when he began working on the current study three years ago. Nonetheless, the researcher wanted to see for himself- As a member of NASA’s Cassini mission, he had witnessed Cassini’s final and equally daring orbits of Saturn two years earlier and analyzed the unique data from that final phase of the mission.” Thought of the long-completed Galileo mission kept coming to mind,” Roussos recalls.
To his own surprise, among many unusable datasets, there were also some that could be processed and analyzed with great effort.
With the help of this scientific treasure, the authors of the current study were able to determine for the first time the composition of the ions in the inner radiation belts, as well as the velocities and spatial distribution of the ions. Unlike the radiation belts of Earth and Saturn, which are dominated by protons, the region of Io’s orbit also contains large amounts of much heavier oxygen and sulfur ions, with oxygen ions predominating between the two. .
“The heavy ion energy distribution outside of Amalthea’s orbit suggests that they are largely introduced from a region farther from the radiation belts,” Roussos said. The moon Io with its more than 400 active volcanoes, which repeatedly shoot large amounts of sulfur and sulfur dioxide into space, and to a lesser extent Europa, are likely the main sources.
Further inland, in the orbit of Amalthea, the ionic composition changes radically in favor of oxygen. “The concentration and energy of oxygen ions there are much higher than expected,” Roussos said. In fact, the concentration should decrease in this region, because the moons Amalthea and Thebe absorb the incoming ions; the orbits of the two small moons thus form a kind of natural ionic barrier. This behavior is, for example, known from the radiation belts of the Saturnian system with its many moons.
The only explanation for the increased concentration of oxygen ions was therefore another local source in the innermost region of the radiation belts. The release of oxygen from collisions of sulfur ions with fine dust particles from Jupiter’s rings was a possibility, the researchers’ computer simulations showed. The rings, much fainter than those of Saturn, extended approximately to the orbit of Thebes. However, it was also conceivable that low-frequency electromagnetic waves in the magnetospheric environment of the innermost radiation belts heated the oxygen ions to the observed energies.
“Currently, it is not possible to discriminate in favor of one or the other of these possible sources,” Roussos said. Each of these two candidate mechanisms, however, had parallels with the production of high-energy particles in stellar or extrasolar environments, further establishing that Jupiter’s radiation belts extend into the astrophysical realm, a fact that the researcher hoped to justify their future exploration with a dedicated space mission. . (ANI)