Titan
Sol's second largest moon, Titan, orbits Saturn and has a dense, nitrogen-based atmosphere. Methane exists in abundance on the moon. In fact, oceans of methane give the moon a characteristic shared only with Earth, surface liquid. The development of colonies on the surface had to account for Titan's wind, rain, and seasons. Today, Titan is the home of the Independent Worlds of Sol, or sometimes shortened to the Sol Indies. Those who wish to avoid the aristocracy of the Jovian League or the tighter regulations of the ISA setup shop on Titan.History
Shortly after colonization began of the Jovian moons Ganymede and Callisto, interest began to rise for colonies in the orbit of Saturn - especially Titan. However, there was little incentive for the investment until the now famous eco-biologist, Galen Keye, discovered a way to bioengineer plants that would flourish on methane and nitrogen. Some historians have noted that Galen Keye received massive funding from many large pharmaceutical companies of the day. Regardless, Keye's findings in new, bioengineered plantlife helped advance many new terraforming practices.Starting in 2620, the pharmaceutical giant Biodenali and the fledgling but well-funded Thorn Solar approached colonization of Titan as a joint venture. While Keye's bioengineering efforts produced a variety of methane-hungry plants, Titan still posed significant problems with its extremely cold surface temperatures and its dim light from the Sun. This is where Thorn Solar's expertise came into play. Their engineers developed the satellite platform, Solar-Sat1, with a total light output equivalent to 70% of the solar system's Sun. Solar-Sat1 was placed into orbit over Titan in 2653. Fueled by the abundant, rich source of hydrocarbons found on Titan itself, the satellite aided tremendously in creating an environment for plant growth. The light was enough to trigger the new photosynthesis in Keye's plants. The added light, coupled with increased geothermal activity, also allowed the surface temperature on Titan to rise by as much as 150 degrees C.
Other characteristics of Titan made it favorable for human colonies. Its significant atmospheric pressure allowed colonies to be constructed with thinner bulkheads. Also, Titan's layers of trapped water beneath the surface reduced the need for importing the most important resource for human life. This source of water, and an abundance of nitrogen in the atmosphere, also helped maintain the life support systems of Titan's numerous cities. The healthy supplies of methane and ammonia provided a means of creating great fertilizers for the plantlife inside and outside the colonies. This all contributed greatly in reducing costs to build and sustain colonies on Titan.