The Kalandan outpost was an artificial planet manufactured by the Kalandans around the 1st millennium BC. It was approximately the same size as Luna, but had a mass and atmosphere similar to that found on Earth.
The surface was dry with no signs of occurring rainfalls and was covered with poisonous vegetation. A thin layer of topsoil covered a much more durable shell composed of a material with a melting point greater than 9000 degrees. (James T. Kirk discovered this last when he attempted to excavate a grave using a hand phaser.)
During its construction, a deadly disease organism was accidentally created, killing all the Kalandans. The last survivor, Losira, enabled the outpost's automated defenses to protect it until the day when more Kalandans would arrive to secure it. This defense system killed several USS Enterprise crewmen when the ship surveyed the planet in 2268. (TOS: "That Which Survives")