Planet Mercury is named after a god from Roman mythology.
Mercury was the messenger god who, with his winged helmet and winged feet, used to deliver messages to humans on behalf of all the other gods.
Planet Mercury has the fastest orbit of any planet in the Solar System; it reaches a maximum orbital velocity of 105,947 mph (170,505 kmh).
By comparison Earth’s orbital velocity is a much slower 70,000 mph. (108,000 kmh)
Mercury has a diameter of 3,032 miles (4,880 km); compare this with Earth’s diameter of 7,917 miles (12,742 km)
Mercury is one of the four so called ‘terrestrial’ (rocky) planets in the Solar System. Like all other terrestrial planets Mercury has a central metallic core with a surrounding silicate mantle.
The formation of Mercury
Two hypotheses exist to explain how Mercury was formed.
The giant impact hypothesis suggests that the early Mercury used to be much larger than it is now.
In the early Solar System a large planetesimal collided with Mercury, striping it of much of outer mass including much of its mantle; this collision reduced Mercury to the size you see today.