Only two spacecraft have visited this rocky planet: Mariner 10 in 1974-5 and MESSENGER, which flew past Mercury three times before going into orbit around Mercury in 2011.
One day on Mercury (the time it takes for Mercury to rotate or spin once) takes 59 Earth days. Mercury makes a complete orbit around the sun (a year in Mercury time) in just 88 Earth days.
No evidence for life has been found on Mercury. Daytime temperatures can reach 800 degrees Fahrenheit (430 degrees Celsius) and drop to -290 degrees Fahrenheit (-180 degrees Celsius) at night. It is unlikely life (as we know it) could survive on this planet.
Standing on Mercury's surface at its closest point to the sun, the sun would appear more than three times larger than it does on Earth.