Io - Moon of Jupiter, the most volcanic active planet

Moon of Jupiter With hundreds of volcanoes, some spouting lava fountains dozens of miles (or kilometers) high, Io is the most volcanically active planet in the Solar System. Io is caught in a tug-of-war between Jupiter's huge gravity and the lesser but perfectly timed gravitational pulls of two nearby moons, Europa and Ganymede, which orbits farther from Jupiter.

Io is a mortal lady who was turned into a cow in Greek mythology amid a dispute between the Greek god Zeus (Jupiter in Roman mythology) and his wife, Hera (Juno to the Romans).

Size and Distance

Io, Jupiter's third largest moon and the fifth in distance from the planet is somewhat larger than Earth's Moon.

Orbit and Rotation

The massive moons Europa and Ganymede cause Io's orbit to become unusually elliptical, despite the fact that it always points the same side toward Jupiter in its orbit around the giant planet. As a result, Io is subjected to immense tidal forces at various distances from Jupiter.

Io's surface bulges up and down (or in and out) by up to 330 feet as a result of these forces (100 meters). When you compare the tides on Io's solid surface to the tides on Earth's oceans, you'll see how similar they are. The difference between low and high tides on Earth, in the place where tides are strongest, is only 60 feet (18 meters), and this is for water, not solid ground.

Figure 1 Io, the moon of Jupiter from different angles.

Io 3D Model Source: NASA Visualization Technology Applications and Development (VTAD) Published: April 22, 2019, A 3D model of Io, a volcanic moon of Jupiter.

Io's orbit, which keeps it close to Jupiter at about 262,000 miles (422,000 kilometers), crosses across the planet's tremendous magnetic lines of force, thereby turning it into an electric generator. Io can generate 400,000 volts across itself and a 3 million ampere electric current. This current follows the path of least resistance to Jupiter's surface via the planet's magnetic field lines, resulting in lightning in Jupiter's upper atmosphere.

Surface

The tidal forces provide a huge quantity of warmth inside Io, which keeps a good proportion of the surface crust liquid and seeks to release pressure by the escape route open to the surface. The surface of Io is therefore constantly renewed, replenished by molten lava lakes with any impact craters, and spread new fluvial plains of fluid-rock. The structure of this material is not yet fully clear, however, speculations believe it is mainly sulfur molten (which is responsible for the variegated coloring) or silicate rock (which would better account for the apparent temperatures, which may be too hot to be sulfur). The principal component of a thin atmosphere on Io is sulfur dioxide. Unlike the other cooler Galilean lunas, it has no water to talk about. Data from the Galileo probe indicate that Io's own magnetic field can generate an iron core.

Magnetosphere

When Jupiter spins, he takes his magnetic field around, passes Io, and removes roughly 1 ton (1000 kilograms) every second of Io's material. This material is ionized in the magnetic field and generates a cloud of intensive radiation called a plasma torus. Some of the ions are drawn into the atmosphere of Jupiter along the magnetic force lines and form auroras in the high atmosphere of the planet. The ions that flee from this torus inflate the magnetosphere of Jupiter more than double the size which we would expect.

Discovery

On January 8, 1610, Galileo Galilei discovered the planet Io. It was the first time a moon orbiting a planet other than Earth had been discovered, along with three additional Jovian moons. The discovery of the four Galilean satellites led to the realization that our solar system's planets circle the Sun rather than the Earth. Galileo is said to have seen Io on January 7, 1610, but was unable to distinguish between it and Europa until the next night.

Galileo originally referred to Medicean planets as Jupiter's moons and referred numerically to the powerful Italian Medici families as I, II, III, and IV. For a few hundred years the Galileo naming method would be used.

Only in the mid-1800s would the names of the Galilean moons, Io, Europa, Ganymed, and Callisto be formally adopted, and only when the name of the moons by number became evident would it become highly confusing to discover the newly added moons.

Figure 2 August 1609, the manuscript of a letter to Leonardo Donato, Doge of Venice, and January 1610, Notes on Jupiter's Moons Special Collections Library at the University of Michigan is the source of this image.

Existence of Life

Io is an unlikely place to find life due to its constant volcanism and high radiation.