Jupiter

Overview

Io (Jupiter I) is the first of the Galilean moons by distance from Jupiter, and the fourth largest moon in the Solar system with a diameter of 3,642 km. It is the most geologically active object in the Solar System, with over 400 active volcanoes. Discovered in 1610 by Galileo Galilei, it was originally thought to be a single object with Europa, however it was determined on the following day that it is, in fact, a completely separate object.^[1]

Surface Environment

Io's surface is composed of a wide variety sulfurous compounds, which make the surface look colorful. It lacks impact craters, which indicates that it's surface is geologically young, as volcanic materials constantly bury the craters that are made. The surface is mostly composed of plains, with infrequent mountains and lava flows. The colorful surface is mainly composed of silicates, sulfur and sulfur dioxide, mostly of volcanic origin.

Internal structure

Io is the densest moon in the entire Solar system, with a density of 3.52 g/cm3. It contains a silicate-rich crust and mantle and an iron-rich core, which makes up around 20% of Io's total mass. The main source of volcanism on Io is tidal heating- it's gravitational interaction with Jupiter and the other Galilean moons.

Atmosphere

Io has an extremely thin atmosphere consisting mainly of sulfur dioxide. This is mostly due to the fact that most of Io's atmosphere is stripped away by Jupiter's magnetosphere

Orbit

Io is in a 2:1 mean-motion orbital resonance with Europa and a 4:1 mean-motion orbital resonance with Ganymede. This causes Io's orbital eccentricity, which in turn is the main heating source for geological activity.

Exploration

The Pioneer spacecraft were the first ones to conduct any major examination of Io, determining it's approximate mass and suggesting that it has the hightest density of the Galilean satellites. They also produced the only good image of Io's surface. The Voyager spacecraft were the ones to detect it's colorful surface, along with it's volcanic activity. The Galileo spacecraft arrived in 1995, determining that Io has large iron core, observed a major eruption and confirmed that they are mostly composed of silicate magmas.

Images