Mercury

Mercury is the innermost planet of the Sol system. Its radius is about 38% that of Earth. The surface gravity is 0.38 g. Mercury is unique among Sol's planets, in that it is tidally locked to the star, with a 3:2 resonance between its orbital period of 88 earth days and its rotational period of 56 earth days.
Mercury is one of the last places in the Sol system to gain a permanent human presence. It's low orbit around the sun makes the travel there require a lot of fuel. Furthermore, the lack of an atmosphere combined with the slow rotation and the proximity to Sol causes an extreme range of temperatures, from 100 K at night to up to 700 K in the day. Nonetheless, mineral and metal deposits readily available through surface mining provided a strong incentive for economic exploitation, and so the planet is now home to about ten thousand miners across a dozen Roving Bases.

Type

Planet

Location under

Sol