Jupiter's moons leave signature spots in its dawn

Although it is very different from the Earth, Jupiter presents familiar phenomena, including the aurora, what we call the North and South lights. . But the aurorae of Jupiter have something that the Earth does not do: strange features caused by Jovian moons.

Scientists analyzing data from the Juno spacecraft have spotted some of these anomalies in action. They saw swirls and spots caused by the moons of Jupiter Io and Ganymede. And, as is often the case, things were not what they seemed from far away.

"It's always surprising when you look something closer," Bertrand Bonfond, one of the study authors and astronomer at the University of Liege in Belgium, told Gizmodo . "You always find small-scale features that are really surprising and unexpected, the more you look, the more complex it looks."

Jupiter's aurorae, like those of the Earth, are the result of charged particles striking the atmosphere , producing a glow. In the case of Jupiter, the particles come from its magnetosphere, plasma surrounding the planet carried by its intense magnetic field. This plasma comes in part from its moon, the magnetic field of Io-but Io leaves its own mark on the dawn.

Researchers analyzed data from the Infrared Camera and Jovian Infrared Auroral Mapper (JIRAM) spectrometer on the Juno spacecraft. Think of magnetic fields as a set of instructions at each point in the space that tell the charged particles what to do. Io has a magnetic field line that connects the planet and the moon like pearls on a hoop. Crossing the magnetic field of plasma and Jupiter, Io creates waves along this line that sends electrons into the atmosphere of Jupiter

Scientists have already observed the result of this behavior: a bright aurora in the auroras of Jupiter. But they looked more closely and saw what appears to be two streaks or a scribble of other spots – perhaps a secondary vortex effect, a trail left by the intersection of the two magnetic fields. The team also saw Ganymede leave Juno's aurora, but did not see any tail.

Jupiter is not the only planet whose moons cause disturbances in its aurorae – The moon of Saturn Enceladus leaves a similar imprint, according to the article published in Science. "These results are really interesting because it's the first time we've seen a double tail, or cracked, in the aurora Io imprint," said Gizmodo Marissa Vogt, a postdoctoral fellow at Space Physics Center of Boston University.

Results like these can help us understand the intense magnetic environment around Jupiter and other planets. "They provide valuable information about the different magnetic fields and plasma environments, or magnetospheres, that we see through the solar system," Vogt said. "In this case, we learn new things about how Jupiter's moons interact with Jupiter's magnetosphere and how this interaction produces aurora on Jupiter."

Bofond points out that, for the moment, the conclusions come from appearances -and they have not yet been able to make many other observations. Now, he says, scientists must take all the results of different instruments, assemble them and see if they really understand what's going on.

[Science]