little, but fierce
Mercury zooms around the sun faster than any other planet at about 112,000 mph! That means Mercury is the fastest planet in the solar system. It only takes about 88 Earth days to orbit around the sun.
Mercury is one of the four terrestrial planets in the Solar System. Mercury's surface has a rocky, solid composition. Astronomers estimate it to be 70% various metallic materials and 30% silicates, and its core is mostly iron.