We dont actually know why that is, Stevenson says. But I think whatever that explanation might be, its telling us something important about how Jupiter formed. Things could have been stirred up by the impact of another huge proto-planet, he says. Or it could be that somehow Jupiter moved around and more planetesimals were added at a particular stage during formation. There are many different stories you could conjure up.Hybrid magnetismJupiters huge fuzzy core undoubtedly has implications for other aspects of the planets behavior one of them being the planets unusual, contorted magnetic field.

For decades, the textbook picture of the Jovian magnetic field was that it resembled Earths which is to say that it looked like the field of a really big bar magnet, with a well-defined magnetic north pole on one end and a well-defined south pole on the other. Quick peeks from earlier spacecraft seemed to confirm that picture.

But the textbooks were wrong. Junos measurements show that the magnetic field in Jupiters northern hemisphere looks completely different from its southern counterpart. Its as if someone took a bar magnet, bent it almost in half, frayed one end, split the other end, and then stuck the whole thing in the planet at a cockeyed angle. In the north is the frayed end: Rather than emerging around one central spot, the magnetic field sprouts like weeds along a long high-latitude band. In the south is the split end: Some of the field plunges back into the planet around the south pole while some is concentrated in a spot just south of the equator.

Jupiters magnetic field, illustrated in this NASA visualization, is a strange blend of simple and complex. The field emerges from the north in a long band (red areas), and mostly reenters the planet in a compact spot just south of the equator (dark blue).

NASA/JPL-CALTECH/Harvard/Moore et al.

It was weird to have essentially one hemisphere Earth and one hemisphere Uranus and Neptune, says Kimberly Moore, a Caltech astrophysicist and a lead author of several studies of Junos magnetic findings.

Planetary magnetic fields are generated by electrically conductive fluids in their interior. The unusual fields at Uranus and Neptune may be due to these fluids being restricted to a thinner region of the planet, relative to their size. Something similar might be happening at Jupiter thanks to its dilute core, says Moore. The north-south dichotomy may also emerge from all this complexity.

That can really change the geometry of the patterns you can come up with, she says. But thats just one idea. Helium rain might also wreak havoc on the magnetic field, as could penetrating winds.

Jupiter has conga lines of polar cyclones; Saturn has just one vortex per pole (one of which is six-sided!). Jupiters magnetic field is a hodge-podge; Saturns is pretty boring. Jupiters atmosphere is multicolored and banded; Saturns is relatively unblemished.

Giant planets must come in different flavors, Bolton says. We need to understand that if were going to understand them in general, because the same physics must dictate everything.

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What has the Juno spacecraft taught us about Jupiter? - Astronomy Magazine