The Giant Impact Hypothesis is the theory supporting how our Moon formed. In the hypothesis, 4.54 billion years ago the moon formed when an object the size of Mars slammed into Earth. The colliding object was destroyed in the collision, and the stone and iron was rejected from the Earth's crust layers. The iron stuck together, along with stone, which eventually formed the Moon. The moon was made of pure iron according to stone researches, along with the lava that Earth rejected that stuck to the moon. The lava cooled up and formed the pure iron rocks.