Welcome to The Blue Marbles, a solar system which only a few could dream of. Mars is a moon of Venus, Mercury crashed into Luna, Earth's moon at the formation of the Solar System and two small planets instead take the role of the closest planets to the sun. This also had the effect of sending Callisto crashing into Ganymede, pusing Ganemede away from its orbit and making it the 5th planet from the sun. Due to its large mass and density, its core became warm and allowed liquid water to be present on its suface - thus becoming a habitable planet. It has a moon, Ceres.