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

EARTHMERCURYMOON Mercury’s diameter is 4,880 km. That’s 40% smaller than Earth and 40% larger than the moon

Mercury’s core is 75% of its mass, and consists of iron and molten lava Rocky mantle Scientists think Scientists think Mercury’s dipolar magnetic field is produced by its partially molten core. Mercury’s density is similar to that of Earth’s at 5.42 gm/cm^3

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.

Mercury rotates 1.5 times for every revolution. So it has 1.5 days in its year! Its rotational period is Earth days and its orbital period is 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.