which planet is the smallest
The smallest planet in the Solar System is Mercury (the biggest planet is Jupiter). For the longest time, the smallest planet was considered to be Pluto, but now Pluto isnât a planet any more, so weâre back to Mercury.Mercury measures 4879 km along its equator.Just for comparison, Earth is 12,742 km across.So Mercury is only 38% the diameter of Earth.or the longest time, the smallest planet was considered to be Pluto, but now Pluto isnât a planet any more, so weâre back to Mercury. Mercury measures 4879 km along its equator. Just for comparison, Earth is 12,742 km across.