Eruptions of 400 kilometers on a moon of Jupiter

Imagine a world of lava, a land in constant eruption, injecting sulfur and carbon dioxide into the atmosphere. Virtually a hell with eruptions that reach 400 kilometers high. It is not a primitive land, it is not even our world. 628 million kilometers separate us from this land of fire. 628 million kilometers of ice cream space that extend between us and one of the many Jupiter moons.

Its name is Io it has a radius of 1821 kilometers is approximately the size of the moon. This makes it the third largest satellite of Jupiter and, therefore, one of the four moons that Galileo could see with his primitive telescope in 1610. But that does not fool you, because despite its modest size, it is the body geologically more active of the Solar System.

In this world of boilers, water is scarce especially, and not because there are no lakes, but because, directly, it holds the record as the driest body of the Solar System. Io is a satellite of extremes to whom the midpoint does not seem to sit well, even its surface dances between a huge range of temperatures ranging from -130 degrees Celsius to 1600 in its cast rock castings.

Tidal forces

With these huge figures we could think that the interior of Io is exceptionally active and that in it the processes of nuclear fission surpass those of many planets, overheating it. This is, at least, the way in which the interior of our planet "maintains" its heat, but in the case of Io we would be wrong from end to end. Its secret is another and far from relating to nuclear energy, it has to do with the tides.

Specifically we talk about tidal forces, that a body that does not experience the same gravity at all points. Since the force of gravity is reduced with the square of the distance, when two massive objects are close enough, such as the Earth and the Moon, the side of the Moon that "looks at us" is experiencing more force of gravity than the hidden face , braking or even blocking its rotation. This same force is what produces the tides, deforming our seas, causing them to rise under the Moon (and at their antipodes) and that their level drops in the rest of the globe. That is why our moon does not turn just on itself, because it suffers a tidal coupling. Something similar happens with Io, but the Moon is not plagued with volcanoes, so what is the difference?

What changes the rules of the game is that Jupiter not only has a moon, it has many more, and especially two others (Europe and Ganymede) with very interesting properties. As if it were a perfectly synchronized ball, for each lap completed by Ganymede around Jupiter, Europe gives two and Io gives four. This perfect relationship is called orbital resonance, specifically Laplace resonance, and is the key to Io's volcanism.

Thanks to this exceptional synchrony, the tidal forces experienced by Io lengthen its orbit away from the Platonic idea of ​​a circle to make it an ellipse. In this way, and simplifying it a bit: this regularity makes the gravity of the satellites and Jupiter join forces to deform Io among all, generating all that heat that has turned it into a world of lava.

Io's kicks

However, we may be imagining something different from what we can really find in Io. Its volcanoes are not those elevated cones of our Earth. While it is true that it has mountains higher than Everest, the volcanoes of Io are craters sunk in the rock called pateras, and although there are also volcanic cones, these are uncommon and much lower due to the low density of their lava, that spreads across the ground before solidifying.

In Io there are more than 400 active boats and having less than 2% of our mass, it expels more lava than our planet and since its formation, 4,500 million years ago, it has had time to melt all its bark and its mantle approximately eight times. A constant renovation that helps you keep your crust almost like new, with hardly any remnants of the impact of meteors that help us infer the age of the satellite.

And despite this bustling activity, 10% of the temperature of Io is produced by a single patera. Specifically the largest of all, with a diameter of 202 kilometers of pure lava called Loki Patera.

The color of magic in Io

All this volcanism projects into space a multitude of gases present in the earth's crust, especially carbon dioxide and sulfur compounds. Some exceed the escape velocity and fall into the gravitational claws of Jupiter. However, this planet has a huge magnetic shield that deflects these electrically charged particles. Their magnetism redirects them through a sort of invisible highways called field lines, concentrating all of them on the planet's poles and impacting them with their deep atmosphere.

When the eruption is powerful enough, these collisions occur by millions and the result is curtains of lights dancing in the sky, polar auroras in other worlds far away from ours. On the other hand, if the particles fail to overcome the escape velocity of Io, they will fall back on its surface, painting it red, white, gray and cream on a palette from another world.


  • Although Galileo discovered Jupiter's main satellites, he did not give them a name as such. Until Simon Marius, Io, Europe, Ganymede, Callisto arrived with Roman numerals.



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