"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."Īccording to the researchers' model, Jupiter's influence alone can't create tides with the right frequency to resonate with the moons because the moons' oceans are thought to be too thick. "These tidal resonances were known before this work, but only known for tides due to Jupiter, which can only create this resonance effect if the ocean is really thin (less than 300 meters or under 1,000 feet), which is unlikely," Hay said. If you push the swing at the right time, it goes higher, but get the timing wrong and the swing's motion is dampened."Įach moon's natural frequency depends on the depth of its ocean. If you keep on pushing the system at the right frequency, those oscillations get bigger and bigger, just like when you're pushing a swing. "Basically, if you push any object or system and let go, it will wobble at its own natural frequency. "Resonance creates loads more heating," Hay said. The trick to tidal heating is a phenomenon called tidal resonance. 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." "Maintaining subsurface oceans against freezing over geological times requires a fine balance between internal heating and heat loss, and yet we have several pieces of evidence that Europa, Ganymede, Callisto and other moons should be ocean worlds," said co-author Antony Trinh, a postdoctoral research fellow in the Lunar and Planetary Lab. "Io, the Galilean 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. Jupiter has nearly 80 moons, the four largest of which are Io, Europa, Ganymede and Callisto. Understanding how the moons influence each other is important because it can shed light on the evolution of the moon system as a whole.
You wouldn't expect them to be able to create such a large tidal response," said the paper's lead author Hamish Hay, a postdoctoral fellow at the Jet Propulsion Laboratory in Pasadena, California, who did the research when he was a graduate student in the University of Arizona Lunar and Planetary Laboratory.
"It's surprising because the moons are so much smaller than Jupiter. Researchers previously believed that the gas giant Jupiter was responsible for most of the tidal heating associated with the liquid interiors of the moons, but a new study published in Geophysical Research Letters found that moon-moon interactions may be more responsible for the heating than Jupiter alone. As a result, some of the icy moons contain interiors warm enough to host oceans of liquid water, and in the case of the rocky moon Io, tidal heating melts rock into magma. In a process called tidal heating, gravitational tugs from Jupiter's moons and the planet itself stretch and squish the moons enough to warm them. Well, hotter than they should be, for being so far from the sun. The four largest moons of Jupiter in order of distance from Jupiter: Io, Europa, Ganymede and Callisto.
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