This planet has no moon. Mercury's day equals 3 Earth months. Mercury's gravity is about one-third of the Earth's gravity. Mercury's diameter is 3,025 miles. Mercury travels around the Sun every 88 Earth days.
Mercury consists of virtually no atmosphere.
Mercury's orbit is more elliptical than any other planet except Pluto. Mercury has a crust of light silicate rock. Mercury's iron core is about the size of the Earth's moon. In March 1974, Mariner 10 gave us the first close-up photographs of Mercury's surface. Until Mariner 10, little was known about Mercury.