Jackhead is a human colony planet re-charted by the Pathfinder Ship Lexington Keeler .
57% of the planet’s surface area is uninhabitable wasteland. The remaining area is covered by a vast sea, almost perfectly circular. The ocean occupies an enormous crater, the result of a collision with another planet that almost split the world in half, and accounts for the complete uninhabitability of the rest of the planet.
In the middle of this ocean is a small archipelago of islands, whose combined area is less than 100,000 square kilometers. These islands contain most of the human population.
The planet’s population is approximately 90 million people. Most of them reside in a city called Jackhead, built on the island archipelago. The city consists of thousand-meter towers that rise from the islands, or in some cases, the sea-bed. The inhabitants have also constructed ocean-cities with names like Nautica, and Aquatica built on platforms partly above the sea, and partly below.
The crew of Lexington Keeler found the inhabitants to be technologically advanced, well-dressed, well-fed, and provided with ample personal comforts, albeit living under very crowded conditions. Also, due to circumstances that are not quite clear, the inhabitants of Jackhead became the rightful owners of the Pathfinder Ship Lexington Keeler. (Book 06: Crucible )