The magnetic field is also not simple. “What scientists expected was that Jupiter was relatively boring and uniform inside,” Dr. Bolton said. “What we’re finding is anything but that is the truth.”
John E.P. Connerney, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the deputy principal investigator on the mission, reported spatial variations in the magnetic field that were much stronger than expected in some areas and much weaker in others.
The magnetic field is generated by the churning of electrically charged fluids at the core. On Earth, that comes from the convection of molten iron in the outer core. On Jupiter, the currents come from hydrogen, which turns into a metallic fluid under crushing pressures.
The spatial variations suggest that the dynamo of churning currents is larger than had been thought and may extend beyond the metallic hydrogen region, Dr. Connerney said.
For the magnetic field and gravity measurements, a glitch that has greatly slowed the pace of data gathering could turn out to be beneficial. A final engine burn last October was to put Juno in a 14-day orbit, but a pair of sluggish valves in the fuel system led mission managers to forgo that, and Juno remains in the 53-day orbit instead. The spacecraft is to make the same number of orbits and collect the same amount of data, and the longer mission means that Juno may be able to detect slow changes in the magnetic field.
More surprises were found at the top and bottom of Jupiter.
With Juno’s orbits passing almost directly over the north and south poles, scientists can better study the powerful auroras, which are generated by charged…