Jupiter’s moon is the most volcanically active object of its kind in the solar system, and is home to hundreds of erupting craters capable of shooting lava up to 250 miles (400 kilometers) into the air – but why does it seem like those volcanoes are in all the “wrong” places?
Thanks to new analysis of tidal flow in a subsurface ocean of magma, NASA scientists may have finally discovered the answer: oceans beneath the crusts of this tidally-stressed moon could be more common and longer-lasting than previously expected. A paper discussing their findings was published earlier this summer in the Astrophysical Journal Supplement Series.
“This is the first time the amount and distribution of heat produced by fluid tides in a subterranean magma ocean on Io has been studied in detail,” lead author Robert Tyler of the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “We found that the pattern of tidal heating predicted by our fluid-tide model is able to produce the surface heat patterns that are actually observed on Io.”
The intense geological activity found on Io, Tyler and his colleagues explained, is caused by a kind of gravitational tug-of-war between Jupiter and gravity from the neighboring satellite Europa. The faster-moving Io finishes two orbits every time Europa completes one, meaning that the former feels the gravitational pull of the latter at the same orbital location every time.
This causes Io’s orbit to be distorted into an oval shape, which makes it flex as it travels around Jupiter and causes material within the moon to change position. This shifting causes friction and generates heat, similar to how rubbing your hands together warms them up, the agency said.
Answer lies in a mixture of fluid and solid tidal heating
Earlier theories used to explain Io’s heat generation looked at the moon as a clay-like object that is solid, but able to be deformed. However, when scientists using this explanation in computer models, they learned that the majority of the volcanoes were not located where they should have been – they were located 30 to degree degrees to the East of where models predicted the most intense heat should have been produced.
The results turned out to be too consistent to be dismissed as an anomaly, so Tyler’s team needed to find an alternative to the traditional solid-body tidal heating models. They ultimately came up with an explanation that centered around the interaction between heat produced by fluid flow and heat from solid-body tides, co-author Christopher Hamilton of the University of Arizona said.
“Fluids – particularly ‘sticky’ (or viscous) fluids – can generate heat through frictional dissipation of energy as they move,” Hamilton explained in a statement. He and his colleagues believe that most of the ocean layer is a partially-molten slurry that is mixed with solid rock. As molten rock flows under gravity’s influence, it rubs against the solid rock surrounding it, generating heat.
Hamilton said that this process “can be extremely effective for certain combinations of layer thickness and viscosity which can generate resonances that enhance heat production,” and his team believes that this a mixture of fluid and solid tidal heating may offer the best explanation for the Jovian moon’s volcanic activity.
Their findings may also have implications for the search for life on other planets, according to NASA. Some tidally stressed moons, such as Europa and Enceladus, have liquid water oceans beneath their icy surfaces. Those subsurface oceans may contain the ingredients required for life to exist, and the new study suggests that these oceans may be more common and longer lasting than previously believed – no matter if they’re made of magma, water, or something else.
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Pictured is a map of Io created using images from the Voyager 1 and Galileo missions. Image credit: NASA
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