Luna (Sol 3a) is the moon of Earth (Sol III), United Empire of Earth (UEE). Tidally locked to Earth, it has long been a subject of fascination for Humans, and became the first celestial body they visited in SEY 1969. In the 22nd century, Humans began to experiment with sealed bases on Luna's surface, marking their earliest attempts at colonization outside Earth. The remains of these nascent bases were declared a protected historical site in 2799. Today, Luna is home to multiple robust sealed colonies.