Earth-Moon-Mars, not playing from the same deck

Cosmology deals with the formation of the universe, but a subset of the same study looks as planetary formation. Current studies of silicates are showing that the Earth, Moon and Mars were formed under different conditions and explains some of the differences in mass. The moon is believed to be a planet that crashed into earth and the resultant rebound produced it from the upper portion of the earth, mostly made of silicates. This helps to explain why the Moon doesn't have the same iron core and is much lighter than the Earth. Well, Mars also has an iron core, but the silicates aren't of the same type as Earth. Just goes to show that we're still learning much from and about our solar system.