…showed first 75 words of 413 total…

…showed last 75 words of 413 total…to it?s nearness tot he sun, Mercury cooled very slowly. This allowed plenty of time for the iron to settle to the center of the planet. This happened due to the pull of gravity. Mars, in contrast, cooled very quickly because it is more distant from the sun. The rapid cooling did not allow much time for the iron to settle to the planet?s center. This, in turn, made Mars? core less massive.