Mars's core is moltyen still the evidence being that they detect parts of the magnetosphere covering only parts on mars's surface. in a few hundred-thousand years the core will go and cool. as for reproduction on mars those children wouldnt be able to return to earth because when they developed in the mother they would have a smaller heart because the heart does not need to pump against gravity like it does on earth, so they would need a special suit to come to earth as for their bones they would be weaker than those on earth because they dont need to fight against gravity as hard as the bones of people on earth.