New Details About Uranus Discovered In Decades-Old Voyager Data

Uranus as seen by Voyager 2, the only spacecraft that visited the planet. NASA/JPL-Caltech

The ice giant planets of the Solar System, Uranus and Neptune, have not been visited in over 30 years, but deep in the data collected by the Voyager 2 probe, scientists may have discovered new secrets about the atmosphere of Uranus.

Every planet in the Solar System with an atmosphere leaks some of it into space, and the magnetic field of each planet plays a role in it. Mars lost most of its original dense atmosphere, while Earth is holding on to its atmosphere well. Jupiter and Saturn, on the other hand, send blobs of plasma into space, and now researchers think Uranus may do the same.

As reported in Geophysical Research Letters, Gina DiBraccio and Dan Gershman were revisiting Voyager 2 data as they worked on a new mission proposal to the ice giants. Their analysis looked at Voyager 2's magnetometer readings, plotting the data more finely than before. Doing so revealed that within the 45-hour-long study of Uranus, there were 60 seconds of a peculiar magnetic signal. The team believes they detected a plasmoid.

A plasmoid is a blob of charged particles, likely ionized hydrogen. The one detected by Voyager had a cylindrical shape and ranged in size between 204,000 and 400,000 kilometers (127,000 and 250,000 miles). The shape of the magnetic field in the plasmoid suggests it must have come from the atmosphere.

It is difficult to pinpoint how important this mechanism is to the global atmosphere loss of Uranus since it's based on only one set of data. The team estimates that plasmoid ejections could account for between 15 and 55 percent of the planet’s atmosphere that escapes into space. However, without more observations, questions remain.

"It's why I love planetary science," lead author Gina DiBraccio said in a statement. "You're always going somewhere you don't really know."

The authors are primarily interested in the oddities between Uranus' rotation and its magnetic field. The planet rotates on its side, likely from a colossal collision, completing a “barrel roll” in about 17 hours. Its magnetic field is about 60 degrees away, and if we imagine a long magnet bar going through the planet, it would not go through the center. The magnetic field also varies in strength, shifting from around one-third of Earth’s own to four times as much.

An animated GIF showing Uranus' magnetic field. The yellow arrow points to the Sun, the light blue arrow marks Uranus' magnetic axis, and the dark blue arrow marks Uranus' rotation axis. NASA/Scientific Visualization Studio/Tom Bridgman

 

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