The surface has a strong yellowish tinge. Vertical drops extend up to a thousand meters from the surface towards mountains that can be up to 18 kilometers high.
Lava rivers several hundred kilometers long evaporate sulfur dioxide directly into the highly toxic atmosphere. The surface temperature is several hundred degrees below zero, while lava is over 1,000 degrees.
At first glance, it might sound like a description drawn from the mind of a sci-fi writer, but this is in our very own cosmic backyard.
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The most volcanically active place in the solar system
The moon Io is one of the four Galilean moons that orbit the largest planet in the solar system – Jupiter. They are called the Galilean moons because Galileo Galilei discovered them in the early 17th century. This was among the earliest astronomical discoveries made with telescopes.
But it took more than 350 years before humanity learned more about these alien worlds. And now we get new glimpses.
Galileo Galilei was photographed in 1636. He may have been the first to see the moons of Jupiter.
The first scientific measurements made near Jupiter and Io came in the 1970s. The Pioneer probes gave the first signs that something special was going on here, but Voyager 2 showed very hot regions on Io’s surface.
Scientists soon realized that Io must be volcanic. And over the past few decades, Io has been found to be the most volcanically active place in the solar system, according to NASA. No space probe has landed on the Moon yet, but it has been investigated by several space missions, such as the Galileo probe in the 1990s.
Exploration has revealed several hundred volcanoes here spewing lava.
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A highly toxic mixture
This is one of the reasons why the atmosphere is a highly toxic mixture of about 90 percent sulfur dioxide, according to This summary of knowledge about Io from the year 2022, published in the journal Experimental Astronomery.
It takes no more than 0.01 percent of the sulfur dioxide in the air we breathe before it becomes dangerous to us, According to the American Institute of Public Health CDC.
Perhaps unsurprisingly, this moon is inhospitable to life as we know it. Scientists don’t think Io is a good candidate for the search for Earth-like life in the solar system.
Another of Galileo’s moons – Europa – may be hiding a liquid ocean beneath the globe’s ice sheet. This is a much more interesting place in the pursuit of life.
But Io is an extreme planet in a geological context.
The new images come from NASA’s JUNO probe. This probe has been investigating the Jupiter system and its moons since 2016. About a week ago, it flew by Io and provided new images of its volcanic surface.
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quickly fly by
The probe will now make several such fast flybys, as the probe passes by at high speed. It should get close to the surface, although the previous round was relatively close, on an astronomical scale.
It was about 35,000 kilometers from the surface of Io. In comparison, the Moon is about 385,000 km away from us. During the fall, the probe will get closer and closer, as the images will become more detailed.
This gives researchers the ability to track, for example, changes in pyroclastic flows from volcanoes, when they erupt and how big the eruptions are, According to NASA.
In February of next year, Juno will race past the surface of Io within the breadth of a cosmic hair. It must be 1,500 km above the surface.
By comparison, that’s well within the orbit of many Earth-orbiting satellites. We will then obtain new, more detailed images and measurements of the surface.
And this rooftop is a very cool place.
Composite image of many small images from the Galileo mission in the 1990s. The yellow color of all sulfur probably originates from volcanoes. (Image: NASA) Image: search
New surface and tall mountains
At forskning.no, we previously said how tall mountains can be on Earth. It turns out, for example, that Mount Everest, which is 8849 meters high, and other mountains that exist now are higher than terrestrial mountains can be.
But these are tiny wisps compared to what can be found on Io’s surface. Extremely large rock blocks have risen from the surface, and the highest mountains can reach a height of 17 kilometers. According to a 2017 study.
The highest is called Boösaule Montes. These mountains seem to have been propelled by the crust, although the processes that form the mountains are not clear. This is something perhaps close-ups of Juno could shed more light on.
One theory is that the highly active volcanoes on Io expel so much mass that the crust contracts. This creates strong pressures in the crust, which can also contribute to the formation of huge mountains, According to the news site Ars Technica.
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According to astronomer Nicholas Thomas of the University of Bern, not a single meteorite crater has been found on Io’s surface yet.
This is in stark contrast to almost all of the other moons and planets in the solar system. Even the geologically active globe has many relatively new and visible meteorite craters.
This does not mean that Io does not get hit by meteors. This means that the Moon is so geologically active that the surface is renewed and regenerated, so the craters disappear.
And something completely different is driving volcanoes on Io than here on Earth.
In the middle of this photo you can see Boösaule Montes. The mountain can be up to 18 kilometers high, with slopes as high as 15 kilometers. The image is of low quality and was taken by the Voyager probe in 1979 (Photo: NASA) Image: search
friction and heating
The Earth is very hot inside, and this heat is the engine that drives “our” volcanoes.
Incredibly, this heat arises since the planet formed more than 4.5 billion years ago, locked in layers beneath Earth’s crust. Heat also originates from radioactive elements scattered far underground. According to Scientific American.
But Ayo is different. Io is pulled and pulled by the interaction between its giant parent planet Jupiter and the other moons of the Jupiter system.
The graphic below shows an echo in the system. When the moons turn green, they are aligned with each other.
This resonance means that Io and the moons Ganymede and Europa end up in line with each other during certain moments in their orbits. The gravitational pull of the moons and Jupiter helps stretch and push Io.
This creates a lot of internal friction, which in turn creates a lot of heat. This heat melts rocks and feeds the volcanoes on Io. But scientists still know little about what Io looks like on the inside, and what, for example, the core is made of.
These are questions that we hope future exploration can answer.
(The article was first published by forcing)
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