Jupiter is the largest planet in the solar system. It has 67 moons which orbit around it. The spot in the lower left is the Great Red Spot, a giant high-pressure storm that has existed since at least the century.
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.