Io, Europa, Ganimedes puer, atque Calistolascivo nimium perplacuere Iovi.(Io, Europa, the boy Ganymede, and Callisto greatly pleased lustful Jupiter.)[Marius naming Jupiter's moons]
The moon is considered a relatively easy object to land humans on, everything else is much harder by orders of magnitude. It is the reason why we have not been to Mars and will likely never go there s...