Jupiter's moon Io is the closest to Jupiter of the four main Jupiter satellites. As a result, Jupiter's tidal forces are very large. Furthermore, it is also in a resonant relationship with its side satellite Europa, so that if it orbits twice, Europa has orbited once. Therefore, when Europa, Io and Jupiter are aligned, Io becomes slightly elliptical in size. Then, when it returns to its original shape, its interior is tidally heated due to frictional heat. For this reason, Io's center is said to be composed of magma, and it is also said to be the driest object (perhaps even drier than Venus).
In addition, magma from underground has risen to the surface and formed many volcanoes. It is the most geologically active object in the solar system. There are 400 volcanoes confirmed, which may be fewer than on Earth, but Io, with a smaller surface area than Earth, has the largest number of volcanoes in terms of density. There are 11 active volcanoes in operation right now.
In addition, volcanic eruptions cause material to accumulate within Jupiter's magnetosphere. As a result, materials within the geosphere ionize, emitting radiation into space. Therefore, Jupiter probes are designed to withstand radiation. An example would be Juno. Also, no magnetic field is formed.
IO
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