Mercury is the first planet out from the sun. It is 57,910,000 km from the sun, about 1/3 of the way between the Sun and Earth
EARTH MERCURY MOON Mercury’s diameter is 4,880 km. That’s 40% smaller than Earth and 40% larger than the moon
Mercury’s density is similar to that of Earth’s at 5.42 gm/cm^3 Rocky mantle Mercury’s core is 75% of its mass, and consists of iron and molten lava Scientists think Scientists think Mercury’s dipolar magnetic field is produced by its partially molten core.
Mercury’s atmosphere is so thin it is almost negligible. It consists mostly of helium and argon. Because the atmosphere is so thin, Mercury cannot trap or keep out heat. The temperature varies between 427C in the sun and -173C in the dark.
Because Mercury's atmosphere is so thin, meteors collide with it often, leaving their mark in the form of craters in Mercury's rocky surface. Lava from the planet's molten core formed the many smooth plains on Mercury's surface.
Mercury rotates 1.5 times for every revolution. So it has 1.5 days in its year! Its rotational period is 58.65 Earth days and its orbital period is 87.969 Earth days, Mercury has an elliptical orbit, so its path around the sun is not a perfect circle. Sun
Mercury was named after the fleet footed messenger of the gods, because it appeared to move faster around the sun than any other planet. We now know that this was because of its small orbit.
The Mariner 10 spacecraft was launched in March 1973, and flew past Mercury in September 1974. Its flight provided much of what we know about Mercury