The planet Mercury is the smallest planet in the solar system and the closest planet to the sun. It revolves around the sun at a distance of approximately 36 million miles, taking 88 Earth days to complete each orbit.
Mercury rotates slowly, taking 59 Earth days to complete a single rotation. Because it is so close to the sun, temperatures on the side of the planet facing the sun can reach up to 800 degrees Fahrenheit. However, because the planet has virtually no atmosphere, the side facing away from the sun does not retain any of this heat. Temperatures on the night side drop as low as 275 degrees below zero.
Two spacecraft have visited Mercury. The Mariner 10 probe reached the planet in 1974 and made three passes around it, taking pictures and measurements. The Messenger probe, launched in 2004, arrived at Mercury in 2008 and entered an orbit around the planet. The spacecraft is still orbiting Mercury as of 2015 and has sent back a great deal of information about its composition.
There is no evidence that life could survive on Mercury. While the Messenger spacecraft detected signs of ice in permanently shaded areas near the north pole, conditions on the planet seem too extreme to allow any form of life to survive.