Assertion: terrestrial planet's core | /r/MadeOf | material
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Source sentences:
text: Since the outer/inner core boundary is sharp and the pressure on either side of the boundary is nearly equal (given the nearly flat curve for pressure near the center, as shown just above), there is only one way to explain the solid nature of the inner core and the molten nature of the outer core: the inner core must be made of a material that has a higher melting temperature.