This is because Enceladus is expected to have a more rigid ice shell due to its smaller size. The findings indicate that this effect would be greater on Enceladus than on Europa. The study includes a discussion of how an overlying shell on icy moons might dampen ocean tides and cause a reduction in tidal heating. Understanding how tidal heating works can help astrobiologists identify worlds that support subsurface oceans and determine whether or not these oceans might be habitable for life as we know it. Under the right conditions, tidal heating is thought to be a long-term source of energy on some icy worlds that can help to create and maintain liquid subsurface oceans. īy Chrissy Sexton, Earth.A recent study supported in part by the NASA Astrobiology Program discusses the dynamics of tidal heating on worlds with thin subsurface oceans that are covered by ice shells of varying thickness. The study is published in the journal Geophysical Research Letters. It was not until the scientists accounted for the gravitational influence of the other moons that the tidal forces started to approach the natural frequencies of the moons. The model created by the researchers indicates that Jupiter’s influence alone cannot cause tidal resonance within the moons because the moons’ oceans are likely too deep. “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.” “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,” explained Hay. If you push the swing at the right time, it goes higher, but get the timing wrong and the swing’s motion is dampened.” 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. 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.”Īccording to Hay, tidal heating is driven by a phenomenon called tidal resonance. “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. “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 study co-author Antony Trinh. Jupiter has nearly 80 moons, and the four largest are Europa, Ganymede, Io, and Callisto.
You wouldn’t expect them to be able to create such a large tidal response,” said study lead author Hamish Hay.īy understanding how moons affect each other, experts can gain insight into the evolution of the moon system as a whole.
“It’s surprising because the moons are so much smaller than Jupiter. It was previously assumed that Jupiter itself was responsible for most of the tidal heating, but the researchers determined that the gravitational interactions between the moons have a more powerful effect.
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