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Old gas blob from Uranus found in vintage Voyager 2 data


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Old gas blob from Uranus found in vintage Voyager 2 data




Buried inside data that NASA's iconic Voyager 2 spacecraft gathered at Uranus more than 30 years ago is the signature of a massive bubble that may have stolen a blob of the planet's gassy atmosphere.

That's according to scientists who analyzed archived Voyager 2 observations of the magnetic field around Uranus. These measurements had been studied before, but only using a relatively coarse view. In the new research, scientists instead looked at those measurements every two seconds. That detail showed what had previously been missed: an abrupt zigzag in the magnetic field readings that lasted just one minute of the spacecraft's 45-hour journey past Uranus.

The tiny wobble in the Voyager 2 data represents something much larger since the spacecraft was flying so fast. Specifically, the scientists behind the new research believe the zigzag marks a plasmoid, a type of structure that wasn't understood particularly well at the time of the flyby in January 1986.

But by now, plasmoids have earned scientists' respect. A plasmoid is a massive bubble of plasma, which is a soup of charged particles. Plasmoids can break off from the tip of the sleeve of magnetism surrounding a planet like a teardrop.

Scientists have studied these structures at Earth and nearby planets, but never at Uranus or its neighbor Neptune, since Voyager 2 is the only spacecraft to date ever to visit those planets.

Scientists want to know about plasmoids because these structures can pull charged particles out of a planet's atmosphere and fling them into space. And if you change a planet's atmosphere, you change the planet itself. And Uranus' situation is particularly complicated because the planet rotates on its side and its magnetic field is skewed from both that axis and the plane all the planets lie in.




Because Voyager 2 flew straight through this plasmoid, scientists could use the archived data to measure the structure, which they believe was about 250,000 miles (400,000 kilometers) across and could have stretched 127,000 miles (204,000 km) long, according to a NASA statement.

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 spacecraft visit the strange sideways world.






Edited by flash13
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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.

Voyager 2 took this image as it approached the planet Uranus on Jan. 14, 1986. The planet's hazy ... [+]



Uranus, the seventh planet from the Sun, is a truly odd place. Now it just got odder.


Not happy with being the coldest planet of them all and the only planet in the solar system to spin on its side (every 17 hours and 14 minutes), the “ice giant” now appears to be a “wobbly magnetic oddball” that’s leaking its atmosphere into space.


The culprit, reports a new paper published in Geophysical Research Letters, is the planet’s off-center magnetic field, which is tilted relative to the planet’s rotation axis. It produces a wobbly, unpredictable magnetosphere—the region of space surrounding Uranus where the dominant magnetic field is the magnetic field of the planet.


Magnetic fields are generally thought to protect a planet’s atmosphere from escaping—largely by providing protection from the solar wind coming from the Sun—but they can also do the opposite.


Uranus is magnetically weird


“The structure, the way that it moves ..,” said Gina DiBraccio, space physicist at NASA's Goddard Space Flight Center, project scientist for the Mars Atmosphere and Volatile Evolution (MAVEN) mission, and first author of the new paper. “Uranus is really on its own.”


The new discovery—and what’s getting planetary scientists excited—is a plasmoid at Uranus.


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.

An animated GIF showing Uranus' magnetic field. The yellow arrow points to the Sun, the light blue ... [+]



What is a plasmoid?


It’s a giant magnetic bubble that may have been whisking Uranus’ atmosphere out to space. A plasmoid is a structure of plasma (electrified gas) in a magnetic bubble in the magnetosphere of a planet. It’s thought that a cylindrical plasmoid discovered at Uranus—which is at least 127,000 x 250,000 miles across—could be responsible for draining ions from the planet’s atmosphere, therefore causing it to lose mass.


How was the plasmoid found?


The new data comes an old source—a really old source. Only one spacecraft has flown by Uranus—the Voyager 2 spacecraft on January 24 1986, the source of all the photos we have of the planet—and it was only in situ fleetingly.


This VLT near-infrared image of the planet Uranus and several of its moons was taken by the European Southern Observatory (ESO) Paranal Observatory in Chile November 19, 2002.  The rings of Uranus were first observed in 1977 and later photographed by Voyager-2 spacecraft. (Photo by ESO/Getty Images)

This VLT near-infrared image of the planet Uranus and several of its moons was taken by the European ... [+]



During its brief flyby from 50,600 miles/81,433 kilometers it discovered two new rings, 11 new moons and temperatures below minus 353º F/-214º C. This new discovery of a plasmoid was made using data downloaded from Voyager 2’s magnetometer, which monitored the strength and direction of the magnetic fields in the vicinity of Uranus.


Remarkably, the plasmoid showed-up for only 60 seconds of Voyager 2’s 45-hour-long flyby of Uranus, so another visit by a spacecraft to the ice giant would be helpful.

Can we go back to Uranus to check?


Yes, but only if we get moving. “Imagine if one spacecraft just flew through this room and tried to characterize the entire Earth,” said DiBraccio. “Obviously it's not going to show you anything about what the Sahara or Antarctica is like.” A report in Nature recently stated that a planetary alignment will provide a window to visit and Neptune in the after a slingshot around Jupiter. However, the spacecraft would need to leave Earth by the early 2030s to get to Uranus by 2043.


That won’t be an easy deadline to meet, but some kind of mission to Uranus remains a strong possibility. The lure of the least-known, oddest planet in the solar system will just be too much for planetary scientists to resist.


Wishing you clear skies and wide eyes.



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