Which planets are metallic planets?

• A. Mercury, Venus, Earth, Mars
• B. Jupiter, Saturn, Uranus, Neptune
• C. Pluto and Eris
• D. Earth and Mars

Answer: (A)

Metallic planets, in this context, are the rocky worlds with metal-rich cores and solid surfaces, which gives them higher densities. The four inner planets fit this description: Mercury, Venus, Earth, and Mars are terrestrial planets with rocky mantles and iron-nickel cores, so they are dense and solid. The outer planets are gas or ice giants, lacking solid surfaces and having much lower overall densities, so they aren’t considered metallic planets in this sense. Pluto and Eris are dwarf/icy bodies and not part of the metallic, rocky category. Earth and Mars alone don’t capture the full set of metallic planets, so the complete group of rocky, metal-rich worlds is Mercury, Venus, Earth, and Mars.