Mercury  is a little larger than the Earth's Moon and is believed to be composed mostly of iron and rock, making it considerably denser than the Moon. Mercury also has a magnetic field about 1% as strong as the Earth's. 

• Mercury's diameter is only one third that of the Earth's

• It has only 6 percent the mass

• If you weigh 180 pounds on the Earth, you would weigh 64 pounds on Mercury

• Is only one-third the Earth's distance from the Sun