Mercury is the first planet of pur solar system. It's diameter is about 4,880km. It has mass about 3,302,000,000,000 tonnes. An average distance from Sun is about 57,909,175km. It completely rotates in 58.969 days. Its average temperature is +166.86°C. It has 0 moons. It was named after the speedy messenger of the Gods because it seemed to move more quickly than the other planets. In 2004, NASA launched MESSENGER probe, which is due to reach Mercury in 2011.