terrestrial planet, the earth or a planet that resembles the earth in its physical characteristics. The terrestrial planets in the solar system are the earth , Mercury , Venus , and Mars . These planets are approximately the same size, with the earth the largest. They are considerably denser than the Jovian planets , ranging from a specific gravity of 4 for Mars to 5.5 for the earth. Because they spin less rapidly than the Jovian planets, the terrestrial planets are less flattened at their poles.
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