Mining Old Data from NASA’s Voyager 2 Solves Several Uranus Mysteries | JPL
NASA’s Voyager 2 captured this image of planet Uranus while flying by the ice giant in 1986. New research using data from the mission shows a solar wind event took place during the flyby, leading to a mystery about the planet’s magnetosphere that may now be better understood.
Artist’s concept depicts how Uranus’s magnetosphere was acting before and during the flyby of NASA’s Voyager 2. The first panel of this artist’s concept depicts how Uranus’s magnetosphere—its "protective bubble"—was before the flyby of NASA’s Voyager 2. The second panel shows an unusual kind of solar weather was happening during the 1986 flyby, giving scientists a skewed view of the magnetosphere.
NASA’s Voyager 2 spacecraft flyby of Uranus thirty-eight years ago in 1986 shaped scientists’ understanding of the planet but also introduced unexplained oddities. A recent data investigation has offered potential new answers.
NASA’s Voyager 2 spacecraft provided scientists’ first—and, so far, only—close glimpse of this strange, sideways-rotating outer planet. Alongside the discovery of new moons and rings, new mysteries confronted scientists. The energized particles around the planet defied their understanding of how magnetic fields work to trap particle radiation, and Uranus earned a reputation as an outlier in our solar system.
Now, new research analyzing the data collected during that flyby 38 years ago has found that the source of that particular mystery is a cosmic coincidence. It turns out that in the days just before Voyager 2’s flyby, the planet had been affected by an unusual kind of space weather that compressed the planet’s magnetic field substantially.
“If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus,” said Jamie Jasinski of NASA’s Jet Propulsion Laboratory (JPL) in Southern California and lead author of the new work published in Nature Astronomy. “The spacecraft saw Uranus in conditions that only occur about 4% of the time.”
Magnetospheres act as "protective bubbles" around planets (including Earth) with magnetic cores and magnetic fields, shielding them from jets of ionized gas—or plasma—that stream out from the Sun in the solar wind. Learning more about how magnetospheres work is also important for understanding our own planet.
Inside Uranus’ magnetosphere were electron radiation belts with an intensity second only to Jupiter’s notoriously brutal radiation belts. However, there was apparently no source of energized particles to feed those active belts. In fact, the rest of Uranus’ magnetosphere was almost devoid of plasma.
The missing plasma also puzzled scientists because they knew that the five major Uranian moons in the magnetic bubble should have produced water ions, as icy moons around other outer planets do. They concluded that the moons must be inert with no ongoing activity.
Solving the Mystery
Why was no plasma observed, and what was happening to boost the radiation belts? The new data analysis points to the solar wind. When plasma from the Sun pounded and compressed the magnetosphere, it likely drove plasma out of the system. The solar wind event also would have briefly intensified the dynamics of the magnetosphere. This would have fed the belts by injecting electrons into them.
The findings could be good news for those five major moons of Uranus. Several of them may be geologically active after all. With an explanation for the temporarily missing plasma, researchers say it is plausible that the moons actually may have been spewing ions into the surrounding bubble all along.
Planetary scientists are focusing on bolstering their knowledge about the mysterious Uranus system. The National Academies’ 2023 Planetary Science and Astrobiology Decadal Survey prioritized it as a target for future NASA missions.
JPL’s Linda Spilker was among the Voyager 2 mission scientists concentrating on the images and other data that arrived during the Uranus flyby in 1986. She remembers the anticipation and excitement of the event. It changed how scientists thought about the Uranian system.
“The flyby was packed with surprises, and we were searching for an explanation of its unusual behavior. The magnetosphere Voyager 2 measured was only a snapshot in time,” said Spilker, who has returned to the iconic mission to lead its science team as project scientist. “This new work explains some of the apparent contradictions, and it will change our view of Uranus once again.”
Voyager 2, now in interstellar space, is almost 13 billion miles (21 billion kilometers) from Earth.
Credits: NASA's Jet Propulsion Laboratory-Caltech
Release Date: Nov. 11, 2024
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