It takes a total 1407.5 hours, or 58.646 Earth days, for Mercury to make a complete rotation on its axis. A day on Earth is only 23.934 hours long, which pales in comparison to Mercury's extremely long days. Mercury makes a full rotation around the sun in 88 Earth days, and it is the closest planet to the sun, which is a distance of 36 million miles.
Mercury has a mean radius of 2,439.7 kilometers, and it is only a little larger than Earth's moon. The rocky and crater-covered planet has a thin atmosphere that is made up of helium, potassium, oxygen, sodium and hydrogen. Mercury is subjected to extreme heat from the sun during the day, and it experiences temperatures that drop to -290 degrees Fahrenheit at night.