Tidal heating explains why Jupiter’s moons are far hotter than researchers expect, study claims

Even though Jupiter is around 778 million kilometres away from the Sun, the planet's moons are hotter than they are expected to be. Jupiter has nearly 80 moons, including Io, Europa, Ganymede and Callisto, which are the four largest.While it was thought that the extra warmth was provided by the planet itself, a new study now says that they are probably heating up each other.The new study published in Geophysical Research Letters found that moon-moon interactions may be more responsible for the heating than Jupiter alone.According to the paper's lead author Hamish Hay, a postdoctoral fellow at the Jet Propulsion Laboratory in Pasadena, California, who did the research while he was a graduate student in the University of Arizona Lunar and Planetary Laboratory, the result was surprising because Jupiter's moons are much smaller than the planet itself and one would not expect them to be able to create such a large tidal response.According to a report by The University of Arizona, in a process called tidal heating, gravitational pull from Jupiter's moons and the planet itself and squish the moons enough to warm them. According to researchers this results in some icy moons containing interiors warm enough to host oceans of liquid water and in case of Io, the rocky moon, magma, due to tidal heating.[caption id="attachment_2210828" align="alignnone" width="940"]

The planet Jupiter is shown with one of its moons, Ganymede (bottom), in this NASA image captured on 9 April 2007. Scientists using the Hubble Space Telescope have confirmed that the Jupiter-orbiting moon Ganymede has an ocean beneath its icy surface, raising the prospects for life, NASA said on Thursday. Image: NASA[/caption]Researchers are of the opinion that understanding how the moons influence each other could shed light on the evolution of the moon system as a whole.Co-author of the study Antony Trinh added that maintaining subsurface oceans against freezing over geological times require a fine balance between internal heating and heat loss, and yet researchers have several pieces of evidence that moons like Europa, Ganymede, Callisto and others should have ocean worlds. Io, which is closest to Jupiter, on its part, shows widespread volcanic activity which is another consequence of tidal heating."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," Trinh added.According to study authors, tidal heating works through what's called tidal resonance, which means that the moons are essentially being vibrated at certain frequencies, and it's a phenomenon that happens everywhere there's water, including Earth.As per Hay, resonance creates more heating. According to him if a person pushes any object or system and let go, it wobbles at its own frequency. He added that if one keeps on pushing the system at right frequency, the oscillations get bigger and bigger. If one pushes at the right time, it goes higher but if the timing goes wrong then the motion gets dampened.While calculating these natural frequencies, researchers discovered that the tidal resonance of Jupiter alone don't match the sizes of the oceans through to be on these moons. According to study authors it is only when gravitational forces from the moons themselves are also added in that the tidal forces match current estimates of the moon oceans.According to the scientists, the overall tidal heating might be enough to melt ice and rock inside the moons.