Mercury
Mercury is one of five planets visible with the naked eye on the sky. Is also one of four rocky planets (along with Venus, Earth and Mars). It surface is all covered with craters and it doesn’t have any moons.
Mercury is the smallest planet in our solar system. Is just 4,879 km. across its equator, compared with 12,742 km. for the Earth. It’s just a little bigger than Earth’s moon. Mercury is the closest planet to the sun, but it’s actually not the hottest. Mercury's surface temperature can reach 450 C. But becouse Mercury doesn't have much of a real atmosphere to keep any heat, at night temperatures can drop to -170 C.
This small planet spins around slowly compared to Earth, so one day on Mercur takes 59 Earth days. A year on Mercury goes by fast. Because it’s the closest planet to the sun, it doesn’t take very long to go all the way around. It completes one revolution around the sun in just 88 Earth days.
A day on Mercury is not like a day here on Earth. For us, the sun rises and sets each and every day. Because Mercury has a slow spin and short year, it takes a long time for the sun to rise and set there. Mercury only has one sunrise every 180 Earth days!