Oct 2010 Io in True Color Credit: Galileo Project, JPL, NASA The strangest moon in the Solar System is bright yellow. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes.
Mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune.
Callisto - Fourth moon of Jupiter after Io - Europa - Ganymede. Formed of rock and ices Third largest moon in our solar system after Titan (Saturn) and Ganymede (Jupiter) respectively. Jupiter's Io being fourth and our Luna fifth.
This view of Jupiter’s moon Io was captured by NASA’s Galileo spacecraft. Slightly larger than Earth’s moon, Io is the most volcanically active body in the solar system. Credit: NASA/JPL/University of.