Uranus is very far from the sun, making it one of the coldest planets in our solar system. Over 30 years ago, Voyager 2 flew by the planet on January 24, 1986. Decades later, scientists were looking over that data again and found another new secret about the planet. What scientists didn’t know 34 years ago was that Voyager 2 had flown through a plasmoid, which is a giant magnetic bubble that scientists believe could have been stripping Uranus of its atmosphere.
Scientists say that atmospheric escape is driven by the magnetic field of the planet that can help the atmospheric escape or hinder the process. Magnetic fields are believed to help protect the planet by fending off atmosphere-stripping blasts from the solar wind. However, these magnetic fields can also create opportunities for the atmosphere to escape. Both Jupiter and Saturn suffer from this condition where significant amounts of atmosphere escape when magnetic field lines become tangled.
Scientists say that Uranus has a strange magnetic field. Unlike any other planet in the solar system, Uranus spins almost entirely on his side, similar to a pig on a spit roast. The planet completes a full roll once every 17 hours. Uranus has magnetic field axis that points 60 degrees away from that spin axis, meaning as the planet spins its magnetosphere wobbles like a poorly thrown football.
The scientists downloaded the Voyager 2 magnetometer readings that monitored the strength and direction of the magnetic fields near the spacecraft as it flew by. The scientists zoomed in on the data closer than previous studies and plotted a new data point every 1.92 seconds. Smooth magnetic field lines gave way to jagged spikes and dips.
In their study, the team discovered a zigzag that they believed could be a plasmoid, which was a phenomenon that was little-known when the decades-old spacecraft made its flyby. Since then, Plasmoids and become recognized as an important way planets lose mass. Over time such giant bubbles of plasma pinch off the magnetotail, which is the part of the magnetic field blown back by the sun like a windsock. That allows escaping plasma in to drain ions from the planet’s atmosphere. This marks the first time that plasmoids were detected at Uranus. Scientists believe that the plasmoids could account for between 15 percent and 55 percent of atmospheric mass loss at Uranus.