The fourth planet is the Old Sol system. The headquarters for the Military Arm of the USEC are located on the planet, near Huygens crater. The atmosphere of Mars is thick enough to support human life through the use of air condensors, due to extensive terraforming projects that were cancelled after Dous Novella, leaving the planet in a state of semi-hospitality. Unlike other planets in the Old Sol system, Mars was never fully abandoned after Dous Novella. The Military Arm of the USEC kept their headquarters on Mars, to show that they were not afraid of Dous Novella, and to reassure the masses of humanity that were undergoing the Great Panic. All non-military personalle on Mars were relocated, partly to reduce any civilian causilites if Dous Novella ever attacked, and partly due to the collapse of the economy of Old Sol during the Great Panic.