Mercury is the smallest terrestrial planet in the solar system - less than half the diameter of the Earth. Mercury is also the closest planet to the sun and completes a full orbit revolution in just 88 Earth days.
INTERIOR STRUCTURE: Mercury is a heavily cratered planet with no atmosphere and a surprisingly dense internal structure. At least part of Mercury's metallic core is probably liquid metal, and the size of this core is about the same size as Earth's moon.
Author of the graphic: Eleanor Lutz