Jupiter’s moons may warm each other by tidal resonance

Jupiter’s four largest moons in the range of distance from Jupiter: Io, Europa, Conmeet and Callisto. Credit: NASA / JBL / DLR

Gravity and pull ThursdayThe moons may be responsible for global warming more than just the gas company Jupiter.

Jupiter’s moons are hot.

Since they are far away from the sun, they need to be warmer than that. In a process called tidal warming, the gravitational forces coming from Jupiter’s planets and the planet itself will stretch and squeeze the moons to the point of heating them up. As a result, some icy moons have enough interiors to host oceans of liquid water, and in the case of the rock moon Io, tidal warming melts the rock into magma.

Researchers have previously suggested that the gas giant Jupiter is responsible for most of the wave heat associated with the Moon’s liquid interior, but a new study has been released. Geophysical Research Letters It was found that lunar-lunar interactions may be responsible for more heat than Jupiter alone.

“This is surprising because the moons are much smaller than Jupiter,” said Hamish Hay, a postdoctoral colleague at the Jet Propulsion Laboratory in Pasadena, California.

It is important to understand how the moons influence each other because it may shed light on the overall evolution of the lunar system. Jupiter has about 80 moons, the largest of which are Io, Europa, Canmeet and Callisto.

“Maintaining surface oceans against frost during geological times requires a good balance between internal heat and heat loss, although there is ample evidence that Europa, Canmeet, Callisto and other moons must be marine worlds,” said co-author Anthony Trinh. A postdoctoral research fellow in the lunar and planetary laboratory. “The Galilean Moon Io, closest to Jupiter, shows widespread volcanic activity, another effect of tidal warming, but other Earth-like planets with greater intensity will experience it in their early history. Finally, we would like to understand the source of this heat, the evolution of many worlds in the solar system and beyond For its influence on habitat. ”

Tidal vibration

The trick to tidal warming is an event called tidal resonance.

“Vibration loads generate more heat,” Hay said. “Basically, if you push an object or system out, it will swing at its own natural frequency. If you keep pushing the computer at the right frequency, those oscillations will get bigger and bigger, just like when you push on a swing. If you push the swing at the right time, it will go higher, but misunderstand the time, and the movement of the swing will decrease. ”

The natural frequency of each moon depends on the depth of its ocean.

“This wave resonance was known before this work, but was only known for waves due to Jupiter, which can only produce this vibration effect if the ocean is really thin (less than 300 meters or under 1,000 feet),” Hay said. “When tidal forces act on the global ocean, it creates a tidal wave at the surface that propagates the equator with a certain frequency or duration.”

According to the researchers’ model, Jupiter’s influence alone cannot create waves with the right frequency to resonate with the moons because the oceans of the moons are thought to be too thick. It was only when researchers added to the gravitational influence of other moons that they began to see forces approaching the natural frequencies of the moons.

When the waves generated by other objects in Jupiter’s lunar system correspond to each moon’s own vibrational frequency, the Moon begins to experience more heat than just the waves raised by Jupiter, and in the most extreme cases, this can lead to melting ice or rock internally.

For the moons to experience tidal vibrations, their oceans must be tens of thousands of kilometers – at most a few hundred miles – thick, which is within the range of scientists’ current estimates. However, there are some caveats to the researchers’ findings.

Their model assumes that the wave pattern will never intensify, Hay said. He and his team want to return to this variable in the model and see what happens when that control is removed.

Hay believes that future studies can predict the true depth of the oceans within these moons.

Note: Hamish CFC Hay, Anthony Trinh and Isamu Matsuyama wrote “Galilean satellites operating with the moon – lunar waves”, July 19, 2020, Geophysical Research Letters.
DOI: 10.1029 / 2020GL088317

The study was funded NASAHabitat Worlds Project.