NASA records ghost sound on Jupiter's moon


Ganymede, Jupiter's moon, may actually be a planet. As the largest moon in our Solar System, Ganymede has its own charm to explore further, one of which is related to the mysterious sound that was recorded by NASA.

On June 7, 2021, the Juno probe made a flyby near Ganymede, recording the moon's electromagnetic waves with the Waves instrument. When these emission frequencies are shifted into the audio range, the result is a series of eerie screams and howls. This audio was unveiled at the 2021 American Geophysical Union Fall Meeting.

"These recorded sounds are quite wild and make you feel as if you're driving with Juno, sailing past Ganymede for the first time in more than two decades," said physicist Scott Bolton of the Southwest Research Institute, Juno's principal investigator.

"If you listen closely, you can hear a sudden change to a higher frequency around the midpoint of the recording, indicating the entry of a different region in Ganymede's magnetosphere."

Converting the data obtained to the audio frequency is not just for fun. This is a different way of accessing and experiencing the data, which in turn can help understand fine details that might have been overlooked.

"We have recorded the 'sound' of the Solar System with various probes, including the Voyager spacecraft, as well as planetary missions," Bolton said.

Ganymede has a fully differentiated core, and may have liquid oceans deep beneath its icy crust that could support life. On top of that, it has its own magnetic field, the only moon in the Solar System that has one.

The Galileo spacecraft, which studied Jupiter in the 1990s and early 2000s, also sampled the space around Ganymede, leading to the discovery that the plasma waves were one million times stronger around the moon than the median activity at a corresponding distance around the moon. Jupiter. It's unclear whether it has anything to do with the moon's magnetic field or not. But the theory seems possible.

Juno flew as low as 1,038 kilometers from Ganymede's surface, with a relative speed of 67,000 kilometers per hour. What the new data will reveal is a work in progress, but scientists already have some ideas.

"It is possible that the change in frequency shortly after closest approach was caused by a shift from the night side to the daytime side of Ganymede," said physicist and astronomer William Kurth of the University of Iowa.

Of course, this new discovery is not limited to Ganymede. Juno is also busy observing Jupiter and compiling the most detailed map of the gas giant's magnetic field. This map has taken 32 orbits to compile, and has provided new insight into the equatorial magnetic anomaly known as the Great Blue Spot.

The data show that Jupiter's magnetic field has changed in the past five years, and the Great Blue Spot, pulled by strong Jovian winds, is moving eastward at a speed of four centimeters per second relative to the rest of the planet's interior. This indicates that it completes one turn every 350 years.

Because a planet's magnetosphere is generated by a "dynamo" in the planet's interior (a rotating fluid, convection, and electrical conduction that converts kinetic energy into magnetic energy), studying magnetic fields allows scientists to understand the dynamo. The team's new map shows Jupiter's dynamo is generated by a deep layer of metallic hydrogen surrounding its core.

Scientists are also studying Juno's data to understand turbulence in the Jovian planet's atmosphere. The similarity of this turbulence to the turbulence of phytoplankton in Earth's oceans made oceanographer Lia Siegelman of the Scripps Institution of Oceanography try to connect the dots. He knew that on Jupiter, eddies formed spontaneously and would persist in the long run.

Finally, researchers have unveiled a new photo of something rarely seen: Jupiter's tenuous main dust ring, linked to dust released by its moons Metis and Adrastea. Juno imaged the structure from inside the ring, peered into the stars, and captured the arms of the constellation Perseus.

"It's amazing that we can gaze at this familiar constellation from a spacecraft half a billion miles away," said astronomer Heidi Becker of NASA's Jet Propulsion Laboratory.

"But everything looks pretty much the same as when we look at it from our backyard on Earth. It's a stunning reminder of how small we are and how much is left to explore."

The extended Juno mission will last until June 2025, and is expected to continue to provide incredible insights into the complex, bizarre, and incredibly giant Jupiters of our Solar System.

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