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There's a giant magnetic bubble leaking atmosphere from Uranus

Scientists looking at Voyager 2 data from its flyby of Uranus 34 years ago just made the discovery.

Scientists taking another look at data collected from the Voyager 2 space probe from more than 30 years ago have discovered that the gas giant Uranus appears to have a giant magnetic bubble that is causing atmosphere to be whisked out into space.

NASA said that Voyager 2 may have flown through what is called a plasmoid when it zipped past Uranus on January 24, 1986. Voyager 2's flyby is the only close encounter an Earth-based probe has had with the seventh planet from the sun.

"These giant bubbles of plasma, or electrified gas, pinch off from the end of a planet’s magnetotail — the part of its magnetic field blown back by the Sun like a windsock," NASA writes. "With enough time, escaping plasmoids can drain the ions from a planet’s atmosphere, fundamentally changing its composition."

Credit: NASA/JPL-Caltech
Voyager 2 took this image as it approached the planet Uranus on Jan. 14, 1986. The planet’s hazy bluish color is due to the methane in its atmosphere, which absorbs red wavelengths of light.

Space physicists Gina DiBraccio and Dan Gershman with NASA’s Goddard Space Flight Center believe the plasmoid could account for between 15% and 55% of atmospheric mass loss at Uranus. That's more than either Jupiter or Saturn.

DiBraccio and Gershman believe Uranus' plasmoid is a cylindrical shape at least 127,000 miles long and up to 250,000 miles across. It's likely charged with mostly ionized hydrogen particles.

To be fair, all planets leak atmosphere into space -- even Earth. It just happens very slowly. DiBraccio notes that Mars used to be a wet planet with a thick atmosphere. Four billion years of atmospheric leakage into space is part of the reason it is now dry.

Voyager 2 only had a 60-second encounter with the suspected plasmoid 34 years ago, so it's hard to say how much the plasmoid has changed Uranus over time.

The finding is published in Geophysical Research Letters.

The discovery raises new questions about what NASA calls a "wobbly magnetic oddball" planet. Uranus already has some strange characteristics, such as spinning almost perfectly on its side every 17 hours. Its magnetic axis points 60 degrees away from that spin axis. That causes its magnetosphere to wobble like a poorly-thrown football, according to NASA.

By the way, NASA says not to worry about Earth's atmosphere. Its leakage won't be an issue for humans for about 1 billion years. And by then, the Earth will be well on its way to becoming another hothouse planet like Venus, anyway.

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