Mars, once the homeworld of the Martians until they were exterminated.
Mars is the fourth planet in Sol system and the first Human planetary colony in Known Space. Martians were once native to this world, intelligent though they only achieved a barbaric level of technology. Martians were often hostile, resulting in many human deaths before Jack Brennan diverted an ice asteroid to impact the planet. Mars has little resources of value, as metals and other resources are plentiful in the Belt and Jovian moons, and the cost of retrieving said resources from smaller bodies is more efficient.