![]() ![]() Instead, it's in a 3:2 resonance - in other words, Mercury's day is two-thirds as long as its year.Ĭloser to the Roche limit the body (an exoplanet) is deformed by tidal forces. Mercury's eccentric orbit prevents it from being in a 1:1 spin-orbit resonance. Pluto and Charon are tidally locked to each other. ![]() Examples of this are common in our Solar System. Another way of saying this is that the Moon is in a 1:1 spin-orbit resonance - the ratio of its rotational (spin) period to its orbital period is 1 to 1. ![]() We always see the same face of the Moon from the Earth because the Moon's rotation period is the same as the time it takes to complete one orbit around the Earth. This is why most satellites, like the Moon, face toward their planet - they are "tidally locked" in that orientation. Just as the Earth's rotation is slowing due to the Moon's tidal force on it, the Moon's rotation has slowed until it is locked into this position. The same tidal force that stretches a satellite also tends to slow its rotation until the longest axis of the satellite lines up with the planet. (The Moon is shown in polar view, and is not drawn to scale.) If the Moon didn't spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right. Except for libration effects, this results in it keeping the same face turned towards the Earth, as seen in the figure on the left. The findings of this study were published in the journal Geophysical Research Letters, and they can be accessed here.įor weather, science, and COVID-19 updates on the go, download The Weather Channel App (on Android and iOS store).Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth. In future studies, Hay and his team of researchers intend to see what happens when they lift that constraint, and also study the true depth of the oceans within these moons.Īll in all, getting a complete picture of how these moons influence each other is crucial, as it could shed light on how Jupiter’s wonderful moon system evolved as a whole, and also improve our understanding of how ocean worlds in compact systems evolve. However, this current model functions on the assumption that the tidal resonances never get too extreme. Subsequently, these moons begin experiencing more heating than that caused by Jupiter alone, and in extreme cases, it could also result in the melting of ice or rock internally, especially on Io. This leads to the generation of fast-flowing tidal waves, which effectively release significant amounts of heat into the oceans and crusts of Io and Europa. It was only when the researchers added in the gravitational influence of the other moons that they started to see tidal forces approaching the natural frequencies of the moons.Īs the tides generated by other moons resonate with a moon’s frequency, they serve as an energy source and excite the subsurface lunar oceans near their natural frequencies. Incidentally, the oceans on Jupiter’s moons are so thick, that the planet’s influence alone is incapable of creating tides with the right frequency to resonate with the moons. “You wouldn't expect them to be able to create such a large tidal response.”įor any moon to experience tidal resonance, their oceans must be tens to hundreds of kilometers thick. ![]() “It's surprising because the moons are so much smaller than Jupiter,” said the paper's lead author Hamish Hay, a postdoctoral fellow at the Jet Propulsion Laboratory in Pasadena, California. The tidal heating is what causes the interiors of the moons to heat-up, and it is driven by a phenomenon called tidal resonance. But now, a new study has found that moon-moon interactions may be more responsible for the heating than the Gas Giant.Įssentially, the researchers have found that the moons gravitationally tug at each other and create friction-a process called tidal heating-while Jupiter itself stretches and squishes them. Previously, researchers believed that Jupiter was the sole reason behind most of the heating associated with Io's internal ocean of magma as well as the liquid interiors of its three icy Galilean moons: Europa, Ganymede, and Callisto. And on the planet’s innermost moon, Io, the heat is intense enough to melt rocks into magma. Despite being so far away from the Sun, Jupiter’s moons are hot-hotter than they should be! The beautiful, icy moons are known to contain interiors warm enough to host oceans of liquid water. ![]()
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