1.   Further gravitational segregation of the iron core means that denser material moves inwards displacing less dense material outwards.

2.   This explains why the moon is so rich in silicates but has only a small iron core.

3.   This explains why the moon is so rich in silicates but has only a small iron core, scientists believe.

4.   The finding also supports the idea that Mercury has a thin crust atop an iron core, unlike Earth.

5.   He also has an iron core behind that permanent smile.