Mercury

Mercury is the innermost planet in our solar system. Because of its small size – a diameter of 3030 miles – it is not the easiest of planets to observe. German scientist Johannes Hevelius (1611 - 1687) was among the first to observe a Mercurial transit and discovered the Mercurial phases. Most of our information has been collected by the Mariner 10 space probe that made three successful passes of the planet (March 29 1974, September 21 1974, and March 16 1975) before losing contact with Earth. Averaging an orbital velocity of 47.87 km per second, Mercury is the fastest-moving planet in our solar system.

Mercury: Exploration of a planet
This is a special video in 1-hour mission to the planet Mercury from Mariner 10.