![]() ![]() “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. The exact location of this ocean is strongly dependent on how much (if any) ammonia is mixed in with it (since ammonia is an antifreeze).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. Many scientists believe Callisto houses a subsurface ocean located about 100 km beneath the surface. Callisto completes one full orbit once every 9.4 days.Ĭallisto is mostly comprised of rocky material and water ice. This means that the same side is always facing Jupiter in exactly the same process that keeps Earth’s moon facing the same direction. On the other hand, Callisto is tidally locked to its host planet. Because of this, Callisto doesn’t experience the same type of tidal heating. To achieve that feat, you need very good eyesight and Callisto needs to be near its aphelion – it also helps to block out Jupiter’s light with a small object.Ĭallisto is not a member of the orbital resonance that affects the three inner Galilean moons. In fact, Callisto orbits so far away from its host that it’s possible to see the moon without a telescope. Callisto is the eighth closest moon to Jupiter and, of the Galilean satellites, is the furthest one out. This makes the final Galilean moon the thirteenth largest object and third largest moon in the solar system (by both diameter and mass). (We hope you enjoyed our tour of the four Galilean moons of Jupiter!) Callisto is nearly the same size as Mercury by diameter, but with only about a third of the mass. Callisto is the fourth and final of the Galilean satellites. ![]()
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