50 Years of Human Space Exploration. This is by far the coolest pin I will see tonight. So amazing as to how far the space exploration campaign(s) has come since we first step foot into the putter abyss!
Mercury is the closest planet to the Sun and due to its proximity it is not easily seen except during twilight. For every two orbits of the Sun Mercury completes three rotations about its axis and up until 1965 it was thought that the same side of Mercury constantly faced the Sun.