some scientists believe a Mercury - like object struck the young moon . The Mars - sized asteroid would have been the heat source for our planet . The same object could have been responsible for striking the moon . It also explains where some rare - Earth asteroid came from .
Oxford scientists say a Mercury-like body struck the young Earth . The Mars-sized object would have been the heat source for our planet . The same object could have been responsible for creating the moon . It also explains where some rare-Earth elements came from .