Scientists may have explained a mystery that has puzzled us about Uranus for decades.
Researchers believe that data that appeared not to make sense was collected by a powerful solar storm.
In 1986, Nasa’s Voyager 2 flew by the seventh planet in the Solar System, providing scientists with their first and only glimpse of Uranus, and shaping their understanding of it since.
However, there were some unexpected findings, which experts now say were down to a bout of extreme space weather at the time of the flyby.
They suggest this solar storm likely squashed the planet’s magnetic bubble, pushing plasma out of it, and intensified radiation belts - areas of charged particles trapped on magnetic field lines.
Experts say they now know even less about a typical day on Uranus, and need a second spacecraft to visit the planet in order to find out more about it.
The findings of the flyby indicated the planet’s radiation belts were incredibly intense, second only to Jupiter’s.
Yet the rest of Uranus‘s magnetosphere (magnetic bubble) was nearly empty of plasma (gas atoms or molecules with an electrical charge), meaning no apparent source of charged particles to feed those belts.
Because of the nearly empty magnetosphere, Uranus‘s five moons were assumed to be inert dead worlds, with no ongoing activity.
However, the new findings, published in Nature Astronomy, suggest they could be active after all and may even have oceans.
Co-author Dr William Dunn, of UCL’s Department of Physics and Astronomy, said: “Almost everything we know about Uranus is based on Voyager 2’s two-day flyby.
“This new study shows that a lot of the planet’s bizarre behaviour can be explained by the scale of the space weather event that occurred during that visit.
“We now know even less than we thought about what a typical day in the Uranian system might look like and are even more in need of a second spacecraft to visit to truly understand this mysterious, icy world.
“A big piece of evidence against there being oceans on Uranus‘s moons was the lack of detection of any water-related particles around the planet - Voyager 2 didn’t find water ions.
“But now we can explain that: the solar storm basically would have blown all that material away.”
Dr Linda Spilker, based at Nasa’s Jet Propulsion Laboratory, was among the Voyager 2 mission scientists.
She said: “The flyby was packed with surprises, and we were searching for an explanation of its unusual behaviour.
“The magnetosphere Voyager 2 measured was only a snapshot in time.
“This new work explains some of the apparent contradictions, and it will change our view of Uranus once again.”
A possible Nasa space mission to Uranus is currently being developed after the US National Academies’ 2023 Planetary Science and Astrobiology Decadal Survey prioritised the planetary system as a target for a future mission.
Voyager 2, is now in interstellar space, and is about 13 billion miles (21 billion kilometres) from Earth.
Additional reporting by agencies
