Voyager-2 visited Uranus in 1986. Something more happened when it arrived

The Voyager 2 mission, which provided humanity's first and only close-up view of Uranus, revealed a planet with unexpectedly intense radiation belts and an apparently plasma-depleted magnetosphere.

In Short

• Reanalysis of the 38-year-old data has unveiled a cosmic coincidence
• Voyager 2 arrived at Uranus just days after an unusual solar wind event
• It had dramatically compressed the planet's magnetosphere

Nearly four decades after Nasa's Voyager 2 spacecraft made its historic flyby of Uranus, scientists have uncovered new revelations about the ice giant's peculiar magnetic field.

A recent study published in Nature Astronomy has shed light on the baffling observations made during the 1986 encounter, potentially resolving long-standing mysteries about the planet's magnetosphere.

The Voyager 2 mission, which provided humanity's first and only close-up view of Uranus, revealed a planet with unexpectedly intense radiation belts and an apparently plasma-depleted magnetosphere.

These findings contradicted scientists' understanding of planetary magnetic fields and particle radiation, earning Uranus a reputation as an outlier in our solar system.

However, a reanalysis of the 38-year-old data has unveiled a cosmic coincidence that may explain these anomalies. Lead author Jamie Jasinski of Nasa's Jet Propulsion Laboratory reports that Voyager 2 arrived at Uranus just days after an unusual solar wind event had dramatically compressed the planet's magnetosphere.

"If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus," Jasinski explained. "The spacecraft saw Uranus in conditions that only occur about 4% of the time".

This solar wind event likely drove plasma out of Uranus's magnetic bubble while simultaneously intensifying its radiation belts by injecting electrons into them.

The findings suggest that the planet's magnetosphere is far more dynamic than previously thought, potentially aligning it more closely with other gas giants in the solar system.

The study also offers hope for Uranus's five major moons, previously thought to be geologically inert. With an explanation for the temporarily missing plasma, researchers now speculate that these moons might be actively spewing ions into the surrounding space.

As planetary scientists focus on expanding our knowledge of the Uranian system, these new insights are timely. The National Academies' 2023 Planetary Science and Astrobiology Decadal Survey has prioritised Uranus as a target for a future Nasa mission, making these findings particularly valuable for mission planning.

This reinterpretation of Voyager 2's data shows the enduring value of space exploration and the importance of revisiting historical datasets with new analytical techniques.

As we continue to unravel the mysteries of our solar system, Uranus remains a fascinating subject of study, promising more surprises in the years to come.