Mars is the second smallest planet, Mercury is the smallest. So out of the eight planets, it is comparitively small. Mars' diameter is about half that of Earths. The Gas giant planets are much larger...
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It is extremely small to all other planets in the solar system, excluding Pluto who was just given the boot! It is very close to the sun and it has NO atmsphere, so it has one...
Earth is a little bigger than the other terrestrial planets (Mercury, Venus, and Mars), but the immensity of the jovian planets (Jupiter, Saturn, Uranus, and Neptune) cannot be matched by Earth's....