Many data centres today are located in environments that are vulnerable to the effects of global warming. Humanity needs a backup plan. Lunar Ark aims to establish a data centre on the moon that is built by robots and periodically updated using laser optical communication. The data centre consists of a Lunar Data Receiving Terminal, Lunar Data Archive, and Lunar Construction Robotics System, the first two of which will be constructed by the third part. Lunar Ark envisions a master plan for a multi-planet data infrastructure. The moon is the stepping stone to this long-term vision.