Unique in the solar system, scientists consider the possibility that we are catching Jupiter in the middle of a magnetic reversal
NASA’s Juno spacecraft has discovered something extraordinary about Jupiter. There is an extra magnetic pole near the giant planet’s equator, dubbed “The Great Blue Spot” by researchers who identified it. Jupiter’s unexpected magnetic morphology is a sign that strange things may be happening deep beneath the cloudtops.
When NASA’s Juno spacecraft reached Jupiter in 2016, planetary scientists were eager to learn more about the giant planet’s magnetic field. Juno would fly over both of Jupiter’s poles, skimming just 4000 km above the cloudtops for measurements at point-blank range. Today in the journal Nature, a team of researchers led by Kimberly Moore of Harvard University announced new results from Juno–and they are weird. Among the findings: Jupiter has an extra magnetic pole.
“We find that Jupiter’s magnetic field is different from all other known planetary magnetic fields,” the researchers wrote in the introduction to their paper.
The best way to appreciate the strangeness of Jupiter’s magnetic field is by comparison to Earth. Our planet has two well-defined magnetic poles–one in each hemisphere. This is normal. Jupiter’s southern hemisphere looks normal, too. It has a single magnetic pole located near the planet’s spin axis.
Jupiter’s northern hemisphere, however, is something else. The north magnetic pole is smeared into a swirl, which some writers have likened to a “ponytail.” And there is a second south pole located near the equator. The researchers have dubbed this extra pole “The Great Blue Spot” because it appears blue in their false-color images of magnetic polarity..
In their Nature article, the scientists consider the possibility that we are catching Jupiter in the middle of a magnetic reversal–an unsettled situation with temporary poles popping up in strange places. However, they favor the idea that Jupiter’s inner magnetic dynamo is simply unlike that of other planets. Deep within Jupiter, they posit, liquid metallic hydrogen mixes with partially dissolved rock and ice to create strange electrical currents, giving rise to an equally strange magnetic field.
More clues could be in the offing as Juno continues to orbit Jupiter until 2021. Changes to Jupiter’s magnetic structure, for instance, might reveal that a reversal is underway or, conversely, that the extra pole is stable.