High-Energy Oxygen Ions Discovered in Jupiter’s Innermost Radiation Belts.

 

From 1995 to 2003, NASA’s Galileo spacecraft explored the Jupiter system. Its final orbits took the probe deep into the giant planet’s innermost radiation belts, where it also performed a close flyby of Amalthea.
From 1995 to 2003, NASA’s Galileo spacecraft explored the Jupiter system.
Its final orbits took the probe deep into the giant planet’s innermost radiation belts,
where it also performed a close flyby of Amalthea. Credit: Michael Carroll


Jupiter's inner radiation belts include high-energy oxygen and sulfur ions, as well as a previously undiscovered ion source.


Scientists headed by the Max Planck Institute for Solar System Research (MPS) in Germany have discovered a new secret from the enormous data sets of NASA's Galileo mission to Jupiter. For the first time, oxygen and sulfur were found in large amounts in the high-energy ions around Neptune as part of its inner radiation belt. Volcanic eruptions on Jupiter's moon, Io, are assumed to have spawned them. The scientists found a massive concentration of high-energy oxygen ions in the orbit of Jupiter's moon Amalthea, which orbits deeper inward. There's must be a new ion source at work here. In the journal Science Advances, the research findings have been published.


Radiation belts encircle planets with magnetic fields of their own, such as Earth, Jupiter, and Saturn. Fast-moving charged particles like electrons, protons, and heavier ions rush about in the magnetic field, generating torus-shaped radiation belts, which are invisible. A harmful environment may be created when the particles clash with other molecules, ionizing them and posing a more significant threat to space missions and sensors. Jupiter, the massive planet, has the solar system's most intense radiation bands. New research on Jupiter's inner radiation belts' heavy ions, conducted by scientists from the MPS, the California Institute of Technology, the Johns Hopkins Applied Physics Laboratory, the Laboratory of Instrumentation and Experimental Particle Physics in Portugal, and the Academy of Athens in Greece, has just been published.

 

While the high-energy oxygen and sulfur ions outside Amalthea’s orbit are supplied from the distant magnetosphere as byproducts of Io’s volcanic eruptions, another source must be responsible for the high concentration of high-energy oxygen ions inward of Amalthea, which prevents the transmission of such ions across its orbit
While the high-energy oxygen and sulfur ions outside Amalthea’s orbit are supplied from the distant magnetosphere as byproducts of Io’s volcanic eruptions, another source must be responsible for the high concentration of high-energy oxygen ions inward of Amalthea, which prevents the transmission of such ions across its orbit. Credit: MPS

 

The radiation belts around Jupiter span millions of kilometers into space. Still, the maximum concentrations and velocities of energetic particles may be found inside Europa's orbit around the gas giant, a region with a radius of roughly 670,000 kilometers. Europa is the second of Jupiter's four massive satellites termed "Galilean moons" after Galileo, who discovered them in the 17th century. The innermost Galilean moon, Io, may be found here. There have so far been three space missions that have made in-situ measurements in this deepest region of these radiation belts: Pioneer 11, Galileo, and Juno. According to lead author Dr. Elias Roussos of the new study, "Unfortunately, the data from Pioneer 11 and Juno do not enable us to infer without question what sort of ions the spacecraft met there." As a result, "their energy and origin were likewise unknown until today," he continues. Only newly obtained data from the last months of the Galileo mission is comprehensive enough to rectify this scenario.




It is dangerous to go into the radiation belts' core regions.


In 1995, NASA's Galileo spacecraft arrived on the planet Jupiter. The mission spent the next eight years providing fundamental insights into the distribution and dynamics of charged particles around the gas giant, thanks to the contributions of the Heavy Ion Counter (HIC) from the California Institute of Technology and the Energetic Particle Detector (EPD) from the Johns Hopkins Applied Physics Laboratory and the MPS. Nonetheless, the spacecraft was protected by flying only over the outer sections of the radiation bands, which are less intense than the inner belts. Galileo did not travel into the innermost area of the moons Amalthea and Thebe's orbits until 2003 when a bigger risk was justified and just before the mission's conclusion. Amalthea and Thebe are Jupiter's third and fourth moons, respectively. Io and Europa have farther-reaching orbits.


"The significantly distorted measurement data from HIC and EPD from the inner portion of the radiation belt was predicted due to the exposure to intense radiation. When he began working on the present research three years ago, Roussos had high hopes since none of the equipment had been particularly developed to function in such a hostile environment. Though he wanted to see for himself, the researcher was determined to find out. A Cassini crew member two years before, he had seen the spacecraft's last, equally perilous orbits around Saturn and examined the unique data it yielded. In his own words, "the long-abandoned Galileo expedition kept returning to my thoughts," remembers Rousso. Many of the data sets were useless, but he was surprised to find a few that could be processed and examined with much effort.




Oxygen ions are mysterious.


For the first time, researchers have been able to identify the ion composition inside the inner radiation belts and the ions' velocities and spatial distribution, thanks to the aid of this scientific treasure. Oxygen and sulfur ions predominate in Io's radiation belt, unlike the protons-dominated radiation belts on Earth and Saturn. According to Roussos, this shows that the heavy ions are coming from a more remote section of the radiation belts, who studied their energy distribution. The most probable culprits are the sulfur-emitting moons Io and Europa, which have active volcanoes that spew vast quantities of sulfur and sulfur dioxide into space.


Oxygen dominates the ion composition when one moves closer to Amalthea's orbit. According to the researcher, a greater than predicted quantity of oxygen ions has been found in the area. Because the tiny moons Amalthea and Thebe act as a natural ion barrier by absorbing incoming ions, the concentration should be dropping in this area. With its numerous moons, the Saturnian system has radiation bands that exhibit this kind of activity.


Only a local source in the innermost radiation belts can account for the increasing concentration of oxygen ions. According to computer simulations by researchers, sulfur ions colliding with small dust particles in Jupiter's rings might release oxygen. The rings, which are considerably fainter than Saturn's, stretch to around the orbit of Thebe. In the magnetospheric environment of the deepest radiation belts, however, low-frequency electromagnetic waves may also heat oxygen ions to the measured energy.


At this time, none of these potential origins can be ruled out, according to Roussos. However, either of these two potential mechanisms has parallels to high energy particle production in stellar or extrasolar environments, establishing that Jupiter's radiation belts extend into the astrophysical realm, a fact that the researcher hopes will justify their future exploration by a dedicated space mission.

 

Also Read: Astronomers Discover Evidence of a Giant Moon Orbiting a Jupiter-Sized Planet Outside Our Solar System

 

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