The Smallest Planet. Mercury is the smallest planet in the solar system. The diminutive planet is about 3,030 miles (4,876 kilometers) in diameter, making it about the size of the continental United States and only slightly bigger than Earth's moon.Jan 28, 2015
As a result, Mercury is made out of a large percentage of heavier elements, mainly iron. It is essentially a large metal ball of iron with a very thin silicate crust. Mercury's core makes up about 75% of the planet. Its thin mantle, or crust, is only about 300 to 400 miles thick (500 to 600 km).
In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky.
Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger to the gods. ... An observer on Mercury would therefore see only one day every two years.