Mercury

The closest planet to the sun.  

• Mercury is the closest planet to the sun in our solar system.   It is approximately 36 million miles from the sun.
• Mercury is a small planet.  It is only 3,030 miles (4,878 km) across.  Only Pluto is smaller.  It is about the size of the Earth's moon.  It is about 1/18th of the size of of Earth.
• It takes Mercury about 88 Earth days (almost 3 months) to orbit the sun one time.  Mercury has the smallest orbit of the planets because it is the closest to the sun.
• A day (from sunrise to sunset) on Mercury is about 176 Earth days long (almost 6 months).  This is because Mercury spins very slowly on its axis.
• Mercury's atmosphere is made up of helium, sodium, and hydrogen.
• Mercury is covered with craters, like our moon.  Ice has been detected on Mercury's poles.
• At its coldest, Mercury can be -300° F.  At its hottest, Mercury can be 870° F.
• Mercury does not have any satellites.
• In 1974 and 1975, the Mariner 10 spacecraft passed by the planet and was able to take pictures of the planet, its cratered surface, and to detect ice at the poles.
• Mercury is named after the Roman messenger of the Gods.