Thanks to data from the Voyager 2 scientists have just discovered that the atmosphere of Uranus is literally leaking gas out into space.
Buried inside data gathered by NASA’s iconic Voyager 2 spacecraft during its historic 1986 encounter with the icy planet was the presence of a plasmoid – a pocket of atmospheric material escaping away from Uranus through the planet’s magnetic field.
Based on these data, NASA suggests that the plasmoid itself was about 127,000 miles long and twice as wide.
But Uranus is not the only planet where the atmosphere leaks out into space. Planetary atmospheres all over the solar system are leaking into space.
Hydrogen springs from Venus to join the solar wind, the continuous stream of particles escaping the Sun. Jupiter and Saturn eject globs of their electrically-charged air.
Even Earth is losing about 90 tonnes of atmospheric material a day. But don’t worry, we have around 5,140 trillion tonnes left.
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While these effects are pretty tiny on human timescales, in astronomical terms atmospheric escape can fundamentally alter a planet’s fate. Look at Mars for example.
Mars used to be a wet planet with a thick atmosphere. But during its 4 billion years of leakage to space, the red planet turned into a dusty barren wasteland.
The magnetic field of a planet drives atmospheric escape, which can both help and hamper the process.
The magnetic field can act as a protector for a planet, fending off the atmosphere-stripping blasts of the solar wind. But they can also create opportunities for escape.
However, Uranus’ situation is particularly complicated because the planet rotates on its side with the magnetic poles angled 59 degrees away from the geographic poles. So its magnetic field is a straight-up mess.
The Voyager data used for this analysis is over two decades old. Ideally, scientists would piece together more observations of Uranus’ magnetic field, enough to better understand how this phenomenon has shaped the planet over time. But that will require another probe to visit the strange world.
The research has been published in Geophysical Research Letters.