Once, the solar system lived in peace. All the planets, from Mercury to Pluto, lived in legion, depending on one another for guidance and hope in darkest times. This time was known as the Silver Millennium and has been long forgotten by the people of Earth.
The most famous story of the Silver Millennium is that of the Earth Prince Darien and the Moon Princess Serena. Their love story was passed from generation to generation as the forgotten tales of the Sailor Orbits faded into the distance.