Mercury, Mars, and Earth’s moon all show evidence of heavy cratering from meteor impacts while Earth shows much less evidence of meteor impacts. The most reasonable conclusion to make from this data is that the early solar system had a much higher density of rocky material, but– a) Earth has been resurfaced by ongoing processes.
b) the rocky material was less likely to reach Earth.
c) Earth formed much later, when the solar system had fewer meteors.
d) the protection from impact provided by Earth’s atmosphere is decreasing.