CHICAGO — An complete ocean of liquid magma, or possibly a sizzling coronary heart of strong metallic, might lurk in Io’s underworld.
The floor of Jupiter’s innermost moon is roofed in scorching lava lakes and gored by tons of of energetic volcanoes, some spitting molten rock dozens of kilometers excessive (SN: 8/6/14). Over the years, the moon’s stressed, mesmerizing hellscape has attracted the eye of many planetary scientists (SN: 5/3/22).
Now, researchers are digging into the character of Io’s infernal inside to clarify what’s driving the spectacular volcanism on the moon’s fiery floor. “It’s the most volcanically active place in the solar system,” says planetary scientist Samuel Howell of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “But it’s not really clear where that energy comes from.”
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Researchers usually agree that Io will get most of its power from a gravitational tug-of-war between its dad or mum planet Jupiter and its sibling moon Europa. Those grand forces pull on Io’s rocky physique, producing great frictional warmth in its inside. But how that warmth is saved and moved round stays a thriller.
One clarification is that Io’s netherworld might home an unlimited ocean of liquid magma, planetary scientist David Stevenson of Caltech mentioned December 15 on the American Geophysical Union’s fall assembly. Though the precise dimension of the proposed molten sea stays unsure, it could should be comparatively giant, he mentioned. “The magma ocean could be, say, 100 kilometers thick.”
In 2011, researchers reported that Io’s mantle couldn’t be fully strong. Magnetic measurements of Io from the Galileo spacecraft indicated there have to be an electrically conductive layer contained in the moon. A world underground layer containing molten rock, the scientists wrote, would match the invoice.
Hot spots speckle the floor of the volcanic moon Io on this infrared picture captured by NASA’s Juno spacecraft on July 5, 2022, when the spacecraft was about 80,000 kilometers from the moon.JPL-Caltech/NASA, SwRI, ASI, INAF, JIRAM
But the researchers couldn’t inform whether or not that layer would encompass a steady sea of magma or many little pockets of molten rock dispersed all through strong rock, resembling a soggy sponge.
Building off that earlier work, Stevenson and Caltech geophysicist Yoshinori Miyazaki calculated {that a} blended layer of magma and strong rock beneath Io’s crust could be basically unstable below the quantity of heating they predict happens contained in the moon. The molten rock and strong rock would cut up into distinct layers, with the molten rock coalescing right into a subsurface sea, Stevenson mentioned. “The final conclusion is [that] Io has a magma ocean.”
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But there are different potentialities. “A lot of information is consistent with a large, global conductive layer that could be a magma ocean,” Howell says. “But I wouldn’t say there’s consensus on how to interpret that data.”
Instead, the reality might lie inside Io’s coronary heart, the place a core made from strong metallic might lurk, Howell reported December 15 on the assembly. Previous analysis has advised that Io has a core wealthy in metals. Howell and colleagues calculate {that a} metallic core that’s about as inflexible as strong ice and a rocky mantle as viscous as Earth’s might absolutely dispense the immense portions of warmth that Io is estimated to emit. That would fulfill the energy-shedding function of a magma ocean.
Future measurements collected by NASA’s ongoing Juno mission as properly two future spacecraft — NASA’s Europa Clipper and the European Space Agency’s JUICE — might present the information wanted to find out whether or not both, or some mixture, of the hypotheses is appropriate, Stevenson and Howell mentioned (SN: 12/15/22). Until then, the thriller of what dwells in Io’s darkish depths might have to stay in purgatory.