The strength of the magnetic fields within the Great Blue Spot changes by up to one percent each year, getting stronger in some places, and weakening in others. At the end of the expanded mission in 2025, Moore will have nearly a decade of data to test his hypothesis, which predicts changes of up to 10 percent over that time. “That’s what our model expects, and we want to test it,” he said.
Scientists are also likely to encounter new mysteries. The Great Blue Spot is roughly at the same latitude as the Great Red Spot. Are the two phenomena related or different?
“The fact that they are traveling at different speeds suggests that they may not be related,” Moore said. But there may be some kind of causal mechanism. At the end of the day, it’s one fluid planet.”
During the extended mission, Juno will also pass three large moons of Jupiter.
Last week, Juno gave scientists the first close-up shot of Ganymede, Jupiter’s largest moon in more than 20 years. Ganymede is more than 5,100 kilometers wide, and is larger and more massive than the planet Mercury, the only known moon to generate its own magnetic field.
Hansen-Koharcheck will compare Juno’s photos of Ganymede to older photos. Some parts of the surface feature grooves often seen on icy moons. Although there is an ocean of liquid water under the moon’s icy crust, the ice is thought to be about 100 kilometers thick, and Ganymede’s grooves likely formed a few billion years ago, when the surface was warmer and more resilient, Hansen-Koharczyk said.
“It is unlikely that the land in the canyons was in contact with the water cover,” he said. “However, if we find him, he also jumps and screams.”