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The two smallest major planets, Mercury and Mars, are both smaller than the estimated size of the Earth's core (combined inner and outer core). Mercury has a diameter of about 4879 km and Mars is about 6792 km, compared to the Earth's core which is a sphere about 6972 km in diameter. All of the dwarf planets (Pluto, Eris, Haumea, Makemake, and Ceres) are smaller in diameter than even the Earth's solid inner core (~2440 km in diameter), although Eris is almost as large and Pluto only slightly smaller than Eris. -The Earth's inner core has a thickness (radius) of about 1220 km. -The Earth's outer core has a thickness (radius) of about 2266 km.
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