Mars

Mars is one of the core Terran worlds and first Terran colony. It is one of the most populated planets in the Federation, and is a major industrial center. It is located in the Sol system. Mars is administered by the Martian Administration, commonly known as the Commonwealth of Mars. It is significant for being the first planet in the galaxy to have been terraformed. 
Mars is visible to the naked eye from Earth. For thousands of years, people on Earth were aware of Mars as a planet, distinct from stars. In the late 19th and early 20th century many believed Mars hosted life. However, in the 1960s, humanity became capable of launching probes to other worlds. This culminated in 2001 with the Pathfinder mission, which confirmed Mars as a dead and sterile world. It would be another 27 years until humans made the next step in martian exploration, sending a manned expedition of 12, meant to arrive and stay on Mars for a full month before returning to Earth. These first manned missions deployed a great deal of infrastructure and automated construction robots to prepare for future settlements. In 2038, the first permanent settlement was established. It came to be known as New Jamestown. Many fled Earth during the Unification Wars, and arrived on Mars. As a result, by 2080, Mars had a population of a million. In 2096 it was declared the second commonwealth of the Terran Federation.
Mars' population grew steadily from the Foundation of the Federation. It reached a population of 400 million in the 2400s, mostly in domed cities with artificial gravity. It was decided in 2431 that Mars would be terraformed by the Frijkstadt Corporation. The terraforming lasted for nearly 60 years, ending in 2489. Now, Mars has a day-night cycle, surface temperature, atmosphere and gravity comparable to that of Earth on the entire planet. The population has since exploded, and is now around 4 billion. Mars, unlike Earth does not have a large alien minority, as they make up only 4% of the population. These are almost entirely workers which have immigrated from the Dominions. Mars also houses most of its population in New Cities, which are cities which are built on planets other than Earth. These are planned and have exceptional population density, but do not house as many people as arcologies.
Mars is a major industrial center of the Federation. It hosts many heavy industries, in contrast to Earth and Venus which host high-tech industries. It is one of the largest non-ship weapon manufacturing centers of the Federation. Mars alone accounts for nearly a third of all ammunition for heavy weapons in the Federation. Along with other major industrial centers such as New Tyre, Xanadu, Rechio and Gondwana, it is considered a "national champion", as the Terran Government heavily invests in heavy industries and manufacturing operations. It also hosts some important institutions, such as the Orion Economic Cooperation and Development Association and Ultramarine Corps headquarters. These are located in Olympus Mons City, the second largest city after New Jamestown.