From Halopedia, the Halo wiki
The Sol system, also referred to as the Sol star system, is the home star system of the human species. Earth, the human homeworld, holds the seat of power for both the Unified Earth Government, and the United Nations Space Command.
Humanity first colonized the system's worlds beyond Earth in the late 21st and early 22nd centuries, followed by steady growth of the populations on Earth and the off-world colonies throughout the next two centuries before the launch of the first extrasolar colonization program in 2362, enabled by the development of the Shaw-Fujikawa Translight Engine in 2291.
Attacks on the system
On October 20, the Fleet of Sacred Consecration was detected near the moon of Io. Soon after, the Fleet appeared near Earth, commencing the Battle for Earth. Over the next few months, battles on Earth and elsewhere in the system would take place. The Battle of Mare Erythraeum on Mars would take place during this time frame. The UNSC Home Fleet would be utterly devastated by November 17 with the arrival of the Anodyne Spirit and Truth's fleet. The final skirmish on Earth would take place on December 3, during Operation: MARSH FLASH.
Many of the human habitats in the system survived the assault relatively intact.
List of appearances