However, the odds of finding another pre-existing, suitable world are literally astronomical. So, we develop our own. We take an uninhabited, lifeless satellite, and customize it to fit our needs. We can start on Saturn's largest moon Titan. Titan, larger than Mercury, already has a planet like atmosphere composed primarily of nitrogen with a few hydrocarbons mixed in.
Some scientists believe Titan's surface is made up of half water-ice and half rocky material.
Small ethane seas laced with methane are also thought to be on the surface. These conditions are believed to be similar to those on earth prior to when life began pumping oxygen into the atmosphere. We do not know. Even if it were to start the process, it would take millions of years. However, with the globe's water freed, the technology to release oxygen from the water and ice, and the ability to transport and transplant life, capabilities we already possess, we believe Titan could be made suitable for habitation.