There are just two ways a moon could have been formed from the planet around which it travels: either part of the planet' s outer shell spun off into orbit around the planet or else a large object such as a comet or meteoroid, struck the planet so violently that it dislodged a mass of material from inside the planet
Earth' s moon consists primarily of materials different from those of the Earth' s outer shell
Comets and large meteoroids normally move at very high speeds.