You’d think the moons would be quiet compared to their host planets, but that’s not entirely true – if you know how to listen. The principal investigator for NASA’s Juno mission, Scott Bolton, has produced Audio recording of magnetic field activity around Jupiter’s moon Ganymede When the Juno spacecraft passed by on June 7, 2021. The 50-second clip reveals a sharp change in activity as the probe entered a different part of Ganymede’s magnetosphere, possibly because it left the night side to enter 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 is a reminder that even worlds that seem to be dead often full of activity You can detect using the appropriate tools. It’s just a matter of how easy it is to notice this activity.
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