You’d think the moons would be quiet compared to the host planets, but that’s not entirely true – if you know how to listen. NASA’s Juno mission principal investigator Scott Bolton has produced an audio recording of magnetic field activity around Jupiter’s moon Ganymede during the passage of the Juno spacecraft on June 7, 2021. The 50-second clip reveals a sharp change in the probe’s activity as it entered a different part of Ganymede’s magnetosphere, probably because it left the night side to enter the daylight.
The sound came from the conversion of electrical and magnetic frequencies into the audible range. Jupiter’s moons are dominated by the magnetosphere and are in the recording, but Ganymede is the only moon in the Solar System to have a magnetic field (most likely due to its liquid iron core). This is not an feat that you can replicate elsewhere in the near future.
The soundtrack was part of a larger briefing for Juno as the mission team revealed the most detailed map yet of Jupiter’s magnetic field. The data showed how long it would take the Great Red Spot and the Great Tropical Blue Spot to move around the planet (about 4.5 years and 350 years, respectively). The results also showed that east-west jet streams ruptured the Great Blue Spot, and that polar cyclones behave like ocean vortices on Earth.
You won’t hear these sounds if you can visit Ganymede yourself. However, it’s a reminder that even seemingly dead worlds are often brimming with activity that you can discover with the right tools. It’s just a matter of how easy it is to notice this activity.
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