Juno has completed yet another perijove, the fifth in the science phase of the mission, and NASA has released the first batch of findings from the mission. Some of the findings are no surprise, while others show there’s a lot still to learn about the giant of the solar system:
- The planet’s enormous and powerful magnetic field is surprisingly lumpy, suggesting it may not be generated in the core after all, but rather closer to the surface or even throughout the planet, above the core that is presumed to be made of liquid metallic hydrogen.
- Also, the field is a great deal stronger than previously estimated — 7.766 Gauss, ten times stronger than the strongest naturally-occuring field found on Earth.
- The two poles of Jupiter look very different. This echoes what Cassini found on Saturn, except that Jupiter’s poles not only look dissimilar to each other, they also look dissimilar to Saturn — four poles that look nothing alike. One feature the two poles have in common is that they are densely peppered with cyclonic storms bigger than the Earth, so close they sometimes appear to be rubbing against one another. It is unclear how stable these are; they have never before been visible to a camera.
- The equatorial belt appears to extend deep into Jupiter, making it exceptionally stable over long periods of time — but the same is not true of some of the other bands, where storms appear to be more dynamic and the belts themselves can evolve into other structures.
- Jupiter’s auroras remain mysterious — although the basic process that causes them is the same as on Earth (charged particles slamming into the atmosphere), it doesn’t appear to have the same origin as auroras on Earth. One longstanding mystery is why they seem to track the Galilean satellites around; so far, this remains unanswered.
The next pass is particularly exciting — it will be the first to give Juno a good look at the Great Red Spot. The microwave sounder on board has revealed some intriguing things about the cloud bands; hopefully we will soon have answers to basic questions such as how deep the Great Red Spot goes. It has been raging on Jupiter for at least three centuries, having been first observed in 1665 (and continuously monitored since 1830). Other storms come and go, but that one stays, and it’s one of Jupiter’s oldest and most enduring mysteries.
In the meantime, enjoy this gorgeous time-lapse showing the view from JunoCam during the fifth science pass (sixth orbit, seventh perijove if you count the original orbital capture):