Mars

"The Red Planet didn't get hit nearly as hard as the Blue. Don't mistake that for not being hit- most of the population was wiped out in the first hours. No one has heard anything from them in a long time."

Overview
The fourth planet from Sol, Mars was the first planet to be colonised by humans and also the first to be successfully terraformed to a significant degree. Despite the significant amount of resource invested to make the planet habitable, colonisation attempts never became too big due to the advent of FTL travel only a few years later, spurring more people to travel to worlds like Primus and Secundus. Nonetheless, the population grew over the centuries to several hundred million, while remaining relatively quiet though economically prosperous (Due to its proximity to Earth). As such, the vast swaths of land left unoccupied out of the major cities still echo the early colonisation rush and are largely smaller towns and villages constructed from prefabricated structures. These communities gain commerce from being major farms, and supplying much of the Earth and the outlying bases on Sol with food.

Terraforming
Mars was the first planet to be terraformed by humanity, and proved it was possible to do so. The process was done through several methods. The first stage of colonisation was very small and largely automated- the main structures where large prefab drilling rigs were set up to dig down into the northern and southern ice caps to begin releasing liquid water onto the planet.

At the same time, early explorations and research on Venus initiated a joint operation between the two worlds; an experimental portal network was set up on both planets, channeling excess Carbon dioxide into the atmosphere on Mars to make the atmosphere dense enough to shift the gravity to a more stable 0.97G and significantly reduce solar radiation to a low level so that liquid water can exist on the surface. This shift also started an early greenhouse effect. After the atmosphere stabilied, the already set up mining platforms then began to drill and heat up the permafrost, releasing even more greenhouse gases and water into the atmosphere. The final step was then done with smaller terraforming generators that subtly changed the atmospheric composition to that of a more Earthlike planet and made it habitable without suits or other breathing apparatus.

Current Status
When war was initiated against the S'pher in 2654, Mars was overlooked for a short time due to its remote nature, instead being ignored by the fleet which was instead taking Earth. As such, Mars remained the UCE military outpost in-system for a short time in which plans were made to take back the Earth. However, the increasing amount of transmission and FTL travel around the planet soon drew its attention to the onslaught which was still conquering Earth. A small fleet of several ships would engage in deployments around the planet centred on the five major cities- Olympus, Lunae, Solis, Elysium Prime and Acheron. The tactics would change from those used on Earth due to sending troops onto the planet and doing very little damage from orbit unlike Earth, where little fighting was done from infantry, instead mainly being a fleet engagement. The Siege of Mars would last only a few days before the majority of the population would either evacuate (Along with the population who had evacuated there from Earth) or be wiped out. By 2702, Mars is mainly an abandoned colony world- its cities remain abandoned ghost towns and are overgorwn with plant life and animal life. Its main population consists of Vulture, Archer and a few human scavengers in remote outposts and living in the ruins.