Mercury is a hot, airless, metal rich planet and the closest to the star Sol. While not the hottest planet in the Sol system, it experiences the greatest temperature variation out of all the planets due to its lack of an atmosphere. On the star-facing side of Mercury, temperatures can reach a searing 427° Celsius (801° Fahrenheit), hot enough to melt lead, while on the dark side it can reach a frigid -173°C (-279° F), cold enough to turn a human being into a living ice cube.
Metal rich worlds like this have a large metallic core, with plentiful metallic ores even at the surface. In places, especially around areas past or current volcanism or liquid erosion, some higher metals can be found in their elemental form too. Mining is therefore very efficient, so these worlds are highly valued.
— In-Game Description
Billions of years ago, Mercury was a large hot molten rocky planet. It was bombarded by asteroids and comets which created the craters. It was even hit by another planet, an event that resulted in the formation of the Caloris Basin. Over a thousand of years before the construction of the 3 surface ports, Mercury was visited by many space probes such as Mariner 10 (1974-1975), MESSENGER (2008-2015) and BepiColombo (2025).