Jupiter’s moons are heating each other up

Hyperaxion September 12, 2020 1:19 am

A model created by scientists at the University of Arizona suggests that a process called tidal heating is behind the phenomenon.

Jupiter’s moons are heating up, and according to a new study published in the August issue of Geophysical Research Letters, it appears that the interaction between them is what is causing it.

Jupiter's moons are heating each other up
(Credit: NASA).

The research was conducted by scientists at the University of Arizona, in the United States, and indicates that tidal heating is stronger between the moons than between them and the planet itself.

Studying how the moons interact with each other is important to understand the evolution of Jupiter’s moon system, which has 79 satellites.

“Maintaining subsurface oceans against freezing over geological times requires a fine balance between internal heating and heat loss,” said co-author Antony Trinh from the Lunar and Planetary Lab.

“We have several pieces of evidence that Europa, Ganymede, Callisto and other moons should be ocean worlds.”

Tidal heating

The moons’ temperature rise is due to a phenomenon known as tidal heating, which can be explained by tidal resonance.

As the experts said, if you push any object or system and let it go, it will oscillate at its own natural frequency.

But, if you keep pushing the system at the right frequency, these oscillations will get bigger and bigger.

“[It’s like] when you’re pushing a swing,” explained Hamish Hay, the study’s leader. “If you push the swing at the right time, it goes higher, but get the timing wrong and the swing’s motion is dampened.”

Previously, researchers believed that Jupiter was responsible for most of the tidal heating associated with the liquid inside the moons.

However, the new study found that interactions between the moons play a more important role in their heating than Jupiter.

That’s because tidal heating is associated with the ocean depth of each of the moons. For Jupiter to be able to create the observed resonance effect on its own, the water layer of the satellites would need to be really thin, under 300 meters.

“When tidal forces act on a global ocean, it creates a tidal wave on the surface that ends up propagating around the equator with a certain frequency, or period,” Hay said.

Looking at the model they created, scientists realized that Jupiter’s influence would not be enough to create tides with the right frequency to resonate with the moons, as their oceans are considered to be very deep.

Only when the researchers added the gravitational influence of the other moons did they begin to see tidal forces approaching the satellites’ natural frequencies.

When the tides generated by other objects in Jupiter’s moon system correspond to the resonance frequency of each moon, it causes the moon to heat up, and, in the most extreme cases, leads to the melting of ice or internal sediment.

“Io, the moon closest to Jupiter, shows widespread volcanic activity, another consequence of tidal heating, but at a higher intensity likely experienced by other terrestrial planets, like Earth, in their early history,” Trinh said.

“Ultimately, we want to understand the source of all this heat, both for its influence on the evolution and habitability of the many worlds across the solar system and beyond.”

The astrophysicists say their model has some flaws and needs to be improved, but they were still happy with the results.

“It’s surprising because the moons are so much smaller than Jupiter,” Hay noted. “You wouldn’t expect them to be able to create such a large tidal response.”

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