The Earth and Mars are examples of two planets which are next to each other in space. One might think that because they are neighbors that they would have a similar history, but this is not so. Early in its history Earth did separate into layers. Earth has a well-shaped core and a strong magnetosphere. The interior of Mars seems only to be partially separated into layers. Mars has a small core, a weak magnetic field. A lot of its iron seems to have remained on the surface and in the rocks of the surface. This helps give the planet a reddish-borwn look which is why we call it the "Red Planet". This means that these two planets had a different history.
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