A fresh look at data on Uranus from 1986 has prompted NASA scientists to suggest the planet could support life.
Much of the knowledge about Uranus was gleaned when NASA's robotic spacecraft Voyager 2 conducted a five-day flyby in 1986.
But scientists have now discovered that the probe visited the third largest planet in the solar system at a time of unusual conditions.
At the exact point the Voyager 2 spacecraft flyby took place, Uranus was going through an intense solar wind event.
That led to misleading observations about Uranus, and specifically its magnetic field, NASA scientists said.
"We found that the solar wind conditions present during the flyby only occur 4 per cent of the time," said space plasma physicist Jamie Jasinski of NASA's Jet Propulsion Laboratory, lead author of the study published on Monday in the journal Nature Astronomy.
"The flyby occurred during the maximum peak solar wind intensity in that entire eight-month period."
Researchers took a fresh look at eight months of data from around the time of Voyager 2's visit and found that it encountered Uranus just a few days after the solar wind had squashed its magnetosphere to about 20 per cent of its usual volume.
"We would have observed a much bigger magnetosphere if Voyager 2 had arrived a week earlier," Dr Jasinski said.
A search for potential life
The Voyager 2 observations had suggested that its two largest moons — Titania and Oberon — often orbit outside the magnetosphere.
However, the new study indicates they tend to stay inside the protective bubble, making it easier for scientists to magnetically detect potential subsurface oceans.
"Both are thought to be prime candidates for hosting liquid water oceans in the Uranian system due to their large size relative to the other major moons," Jet Propulsion Laboratory planetary scientist and study co-author Corey Cochrane said.
The scientists believe that large subsurface oceans are a key signifier for potential to support life.
"I mean, the search for habitability for life is one of the key investigations for NASA and science generally. To the slogan usually is follow the water," Dr Jasinski said.
"If these moons we previously thought weren't a place you could find subsurface oceans. If they're more similar to the moons at Jupiter, like Europa, you could have large bodies of subsurface oceans on Uranium moons."
On October 14, NASA launched a spacecraft on a mission to Jupiter's moon Europa to see if it can support life.
NASA scientists are eager to learn whether subsurface oceans on moons around Uranus have conditions suitable to support life.
"A future mission to Uranus is crucial to understanding not only the planet and magnetosphere, but also its atmosphere, rings and moons," Dr Jasinski said.
Uranus is blue-green in colour due to the methane contained in the atmosphere and it has a diameter of about 50,700km.
That means Uranus is big enough to fit 63 Earths inside it and it has 28 known moons and two sets of rings.
