NASA spacecraft spots Io's elusive volcanoes. A big question remains.

NASAis unraveling Io's volcanic secrets.

The 关键字2space agency's Juno spacecraft has been swooping progressively closer to Jupiter's profoundly volcanic moon Io, and its observations reveal the full scope of this lava world's volcanoes. Juno, with instruments that both capture rich imagery and measure heat emanating from the moon's surface, flew over Io's little-known poles in recent years, giving planetary scientists views of these volcanoes — and bringing them closer to an understanding of what's transpiring beneath Io's tortured surface.

"It is the purest form of discovery," Ashley Davies, a planetary scientist at NASA's Jet Propulsion Laboratory who researches Io, told Mashable. "We're seeing things that we have never seen before." 

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Davies led the new research, which was published in the science journal Nature Astronomy.

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Io is blanketed in erupting volcanoes because it's relentlessly locked in a tug-of-war between nearby objects. "Not only is the biggest planet in the solar system [Jupiter] forever pulling at it gravitationally, but so are Io’s Galilean siblings — Europaand the biggest moon in the solar system, Ganymede," NASA explained. "The result is that Io is continuously stretched and squeezed, actions linked to the creation of the lava seen erupting from its many volcanoes."

You can view the vigorous activity in both the north and south poles, detected by Juno's heat-detecting JIRAM instrument, in the image below. The images (a) and (b) show hot spots and volcanoes in the south polar region overlaid over a detailed image of Io; (c) and (d) show hot spots and volcanoes in the north polar region.

The volcanoes on the poles are smaller than those in the lower latitudes, the researchers found, but it's clear there's lively volcanic activity all over Io. Scientists have found 266 active hot spots.

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"We can now see the entire elephant," Davies said.

The red, yellow, and white spots show areas of heat emanating from Io's surface. The images (a) and (b) show the south polar region; (c) and (d) show the north polar region. Credit: NASA / JPL-Caltech / SwRI / ASI / INAF / UArizona / LPL / Jason Perry A graphic showing how Juno's more recent orbits around Jupiter are bringing the spacecraft closer to Io. Credit: NASA / JPL-Caltech / SwRI

Yet even with a complete view of Io's volcanoes, an intriguing geologic question remains: Is there a grandiose global sea of magma swirling beneath Io's surface? Or, perhaps, is the lava pouring onto the moon largely created by a process more similar to Earth's, whereby a great amount of heat flow is created below the hard crust (in the upper mantle), which ultimately gives rise to regions where magma erupts onto the surface?

"That's the big question," Davies noted.

Soon enough, NASA and other Io researchers may get more answers. At the end of 2023, the Juno spacecraft will swoop closer to Io than any mission before it, coming within 930 miles, or 1,500 kilometers, from the Jovian moon. That's quite close: The Hubble telescope orbits just around 332 miles above Earth. If Juno's instruments work well, the spacecraft may beam back some exquisite images of Io, a snapshot of activity on the most volcanically active world in our solar system. 

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"We can now see the entire elephant."

It's possible we'll see lakes of lava. Or lava flowing from volcanoes. 

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But the craft will be traveling through harsh environs during such close passes, where it will be exposed to profoundly high levels of radiation — the type that could damage Juno's instruments. In 2022, a radiation spike during an Io fly-by caused the loss of some images.

"I'm fascinated by this place. This place blows my mind," Davies said. "You keep your fingers crossed that everything works."